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Sample records for geiger-mode avalanche photodiodes

  1. Geiger-Mode Avalanche Photodiode Arrays Integrated to All-Digital CMOS Circuits.

    Science.gov (United States)

    Aull, Brian

    2016-04-08

    This article reviews MIT Lincoln Laboratory's work over the past 20 years to develop photon-sensitive image sensors based on arrays of silicon Geiger-mode avalanche photodiodes. Integration of these detectors to all-digital CMOS readout circuits enable exquisitely sensitive solid-state imagers for lidar, wavefront sensing, and passive imaging.

  2. Characterisation of Geiger-mode avalanche photodiodes for medical imaging applications

    Energy Technology Data Exchange (ETDEWEB)

    Britvitch, I. [Swiss Federal Institute of Technology, CH-8092 Zurich (Switzerland)]. E-mail: Ilia.britvitch@psi.ch; Johnson, I. [Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation); Renker, D. [Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland); Stoykov, A. [Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland); Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation); Lorenz, E. [Swiss Federal Institute of Technology, CH-8092 Zurich (Switzerland); Max Planck Institute for Physics, 80805 Munich (Germany)

    2007-02-01

    Recently developed multipixel Geiger-mode avalanche photodiodes (G-APDs) are very promising candidates for the detection of light in medical imaging instruments (e.g. positron emission tomography) as well as in high-energy physics experiments and astrophysical applications. G-APDs are especially well suited for morpho-functional imaging (multimodality PET/CT, SPECT/CT, PET/MRI, SPECT/MRI). G-APDs have many advantages compared to conventional photosensors such as photomultiplier tubes because of their compact size, low-power consumption, high quantum efficiency and insensitivity to magnetic fields. Compared to avalanche photodiodes and PIN diodes, they are advantageous because of their high gain, reduced sensitivity to pick up and the so-called nuclear counter effect and lower noise. We present measurements of the basic G-APD characteristics: photon detection efficiency, gain, inter-cell crosstalk, dynamic range, recovery time and dark count rate.

  3. Characterisation of Geiger-mode avalanche photodiodes for medical imaging applications

    International Nuclear Information System (INIS)

    Britvitch, I.; Johnson, I.; Renker, D.; Stoykov, A.; Lorenz, E.

    2007-01-01

    Recently developed multipixel Geiger-mode avalanche photodiodes (G-APDs) are very promising candidates for the detection of light in medical imaging instruments (e.g. positron emission tomography) as well as in high-energy physics experiments and astrophysical applications. G-APDs are especially well suited for morpho-functional imaging (multimodality PET/CT, SPECT/CT, PET/MRI, SPECT/MRI). G-APDs have many advantages compared to conventional photosensors such as photomultiplier tubes because of their compact size, low-power consumption, high quantum efficiency and insensitivity to magnetic fields. Compared to avalanche photodiodes and PIN diodes, they are advantageous because of their high gain, reduced sensitivity to pick up and the so-called nuclear counter effect and lower noise. We present measurements of the basic G-APD characteristics: photon detection efficiency, gain, inter-cell crosstalk, dynamic range, recovery time and dark count rate

  4. A discrete model of the development and relaxation of a local microbreakdown in silicon avalanche photodiodes operating in the Geiger mode

    International Nuclear Information System (INIS)

    Vanyushin, I. V.; Gergel, V. A.; Gontar', V. M.; Zimoglyad, V. A.; Tishin, Yu. I.; Kholodnov, V. A.; Shcheleva, I. M.

    2007-01-01

    A new discrete theoretical model of the development and relaxation of a local microbreakdown in silicon avalanche photodiodes operating in the Geiger mode is developed. It is shown that the spreading resistance in the substrate profoundly affects both the amplitude of a single-photon electrical pulse and the possibility of attaining the steady-state form of the avalanche breakdown excluding the Geiger mode of the photodiode's operation. The model is employed to interpret the experimental data obtained using test single-photon cells of avalanche photodiodes fabricated on the basis of the 0.25-μm silicon technology with the use of deep implantation to form the region of avalanche multiplication for the charge carriers. Excellent functional properties of the studied type of the single-photon (Geiger) cell are noted. A typical amplitude characteristic of the cell for optical radiation with the wavelength λ = 0.56 μm in the irradiance range of 10 -3 -10 2 lx is presented; this characteristic indicates that the quantum efficiency of photoconversion is extremely high

  5. Generation efficiency of single-photon current pulses in the Geiger mode of silicon avalanche photodiodes

    International Nuclear Information System (INIS)

    Verkhovtseva, A. V.; Gergel, V. A.

    2009-01-01

    Statistical fluctuations of the avalanche's multiplication efficiency were studied as applied to the single-photon (Geiger) mode of avalanche photodiodes. The distribution function of partial multiplication factors with an anomalously wide (of the order of the average) dispersion was obtained. Expressions for partial feedback factors were derived in terms of the average gain and the corresponding dependences on the diode's overvoltage were calculated. Final expressions for the photon-electric pulse's conversion were derived by averaging corresponding formulas over the coordinate of initiating photoelectron generation using the functions of optical photon absorption in silicon.

  6. Geiger mode avalanche photodiodes for microarray systems

    Science.gov (United States)

    Phelan, Don; Jackson, Carl; Redfern, R. Michael; Morrison, Alan P.; Mathewson, Alan

    2002-06-01

    New Geiger Mode Avalanche Photodiodes (GM-APD) have been designed and characterized specifically for use in microarray systems. Critical parameters such as excess reverse bias voltage, hold-off time and optimum operating temperature have been experimentally determined for these photon-counting devices. The photon detection probability, dark count rate and afterpulsing probability have been measured under different operating conditions. An active- quench circuit (AQC) is presented for operating these GM- APDs. This circuit is relatively simple, robust and has such benefits as reducing average power dissipation and afterpulsing. Arrays of these GM-APDs have already been designed and together with AQCs open up the possibility of having a solid-state microarray detector that enables parallel analysis on a single chip. Another advantage of these GM-APDs over current technology is their low voltage CMOS compatibility which could allow for the fabrication of an AQC on the same device. Small are detectors have already been employed in the time-resolved detection of fluorescence from labeled proteins. It is envisaged that operating these new GM-APDs with this active-quench circuit will have numerous applications for the detection of fluorescence in microarray systems.

  7. Adaptive aperture for Geiger mode avalanche photodiode flash ladar systems

    Science.gov (United States)

    Wang, Liang; Han, Shaokun; Xia, Wenze; Lei, Jieyu

    2018-02-01

    Although the Geiger-mode avalanche photodiode (GM-APD) flash ladar system offers the advantages of high sensitivity and simple construction, its detection performance is influenced not only by the incoming signal-to-noise ratio but also by the absolute number of noise photons. In this paper, we deduce a hyperbolic approximation to estimate the noise-photon number from the false-firing percentage in a GM-APD flash ladar system under dark conditions. By using this hyperbolic approximation function, we introduce a method to adapt the aperture to reduce the number of incoming background-noise photons. Finally, the simulation results show that the adaptive-aperture method decreases the false probability in all cases, increases the detection probability provided that the signal exceeds the noise, and decreases the average ranging error per frame.

  8. The performance of photon counting imaging with a Geiger mode silicon avalanche photodiode

    International Nuclear Information System (INIS)

    Qu, Hui-Ming; Zhang, Yi-Fan; Ji, Zhong-Jie; Chen, Qian

    2013-01-01

    In principle, photon counting imaging can detect a photon. With the development of low-level-light image intensifier techniques and low-level-light detection devices, photon counting imaging can now detect photon images under extremely low illumination. Based on a Geiger mode silicon avalanche photodiode single photon counter, an experimental system for photon counting imaging was built through two-dimensional scanning of a SPAD (single photon avalanche diode) detector. The feasibility of the imaging platform was validated experimentally. Two images with different characteristics, namely, the USAF 1951 resolution test panel and the image of Lena, were chosen to evaluate the imaging performance of the experimental system. The results were compared and analysed. The imaging properties under various illumination and scanning steps were studied. The lowest illumination limit of the SPAD photon counting imaging was determined. (letter)

  9. A novel camera type for very high energy gamma-ray astronomy based on Geiger-mode avalanche photodiodes

    International Nuclear Information System (INIS)

    Anderhub, H; Biland, A; Boller, A; Braun, I; Commichau, S; Commichau, V; Dorner, D; Gendotti, A; Grimm, O; Gunten, H von; Hildebrand, D; Horisberger, U; Kraehenbuehl, T; Kranich, D; Lorenz, E; Lustermann, W; Backes, M; Neise, D; Bretz, T; Mannheim, K

    2009-01-01

    Geiger-mode avalanche photodiodes (G-APD) are promising new sensors for light detection in atmospheric Cherenkov telescopes. In this paper, the design and commissioning of a 36-pixel G-APD prototype camera is presented. The data acquisition is based on the Domino Ring Sampling (DRS2) chip. A sub-nanosecond time resolution has been achieved. Cosmic-ray induced air showers have been recorded using an imaging mirror setup, in a self-triggered mode. This is the first time that such measurements have been carried out with a complete G-APD camera.

  10. Radiation damage of multipixel Geiger-mode avalanche photodiodes irradiated with low-energy γ's and electrons

    Energy Technology Data Exchange (ETDEWEB)

    Kwon, Y.; Yun, Y. B. [Yonsei University, Seoul (Korea, Republic of); Ha, J. M. [Yonsei University, Seoul (Korea, Republic of); Electronics and Telecommunications Research Institute, Daejeon (Korea, Republic of); Lee, J. S.; Yoon, Y. S. [Electronics and Telecommunications Research Institute, Daejeon (Korea, Republic of); Eun, J. W. [Namseoul University, Cheonan (Korea, Republic of)

    2012-05-15

    A few types of multipipixel Geiger-mode avalanche photodiodes (also referred to as silicon photomultipliers SiPMs) are irradiated with 1 to 2.5 MeV γ's and electrons. We characterize radiation damage effects appearing in the reverse bias current, the dark current and count rate, the pixel gain, and the photon detection efficiency of the devices. An interesting observation on the dark current and count rate is made and linked to the specific damage caused by the irradiation.

  11. Analysis and modeling of optical crosstalk in InP-based Geiger-mode avalanche photodiode FPAs

    Science.gov (United States)

    Chau, Quan; Jiang, Xudong; Itzler, Mark A.; Entwistle, Mark; Piccione, Brian; Owens, Mark; Slomkowski, Krystyna

    2015-05-01

    Optical crosstalk is a major factor limiting the performance of Geiger-mode avalanche photodiode (GmAPD) focal plane arrays (FPAs). This is especially true for arrays with increased pixel density and broader spectral operation. We have performed extensive experimental and theoretical investigations on the crosstalk effects in InP-based GmAPD FPAs for both 1.06-μm and 1.55-μm applications. Mechanisms responsible for intrinsic dark counts are Poisson processes, and their inter-arrival time distribution is an exponential function. In FPAs, intrinsic dark counts and cross talk events coexist, and the inter-arrival time distribution deviates from purely exponential behavior. From both experimental data and computer simulations, we show the dependence of this deviation on the crosstalk probability. The spatial characteristics of crosstalk are also demonstrated. From the temporal and spatial distribution of crosstalk, an efficient algorithm to identify and quantify crosstalk is introduced.

  12. Optical Communications With A Geiger Mode APD Array

    Science.gov (United States)

    2016-02-09

    practical performance of a Geiger mode avalanche photodiode ( GM -APD, or Geiger mode APD) array for use in optical com- munications systems. I designed and...signal quality in the first half of the frame. These shorter reset times also did not offer any advantage in the maximum number of counts able to be...pattern was advantageous for the modifications being made in post-processing on the benchmark data. In particular, this allowed post-processing results

  13. Gallium-based avalanche photodiode optical crosstalk

    International Nuclear Information System (INIS)

    Blazej, Josef; Prochazka, Ivan; Hamal, Karel; Sopko, Bruno; Chren, Dominik

    2006-01-01

    Solid-state single photon detectors based on avalanche photodiode are getting more attention in various areas of applied physics: optical sensors, quantum key distribution, optical ranging and Lidar, time-resolved spectroscopy, X-ray laser diagnostics, and turbid media imaging. Avalanche photodiodes specifically designed for single photon counting semiconductor avalanche structures have been developed on the basis of various materials: Si, Ge, GaP, GaAsP, and InGaP/InGaAs at the Czech Technical University in Prague during the last 20 years. They have been tailored for numerous applications. Trends in demand are focused on detection array construction recently. Even extremely small arrays containing a few cells are of great importance for users. Electrical crosstalk between individual gating and quenching circuits and optical crosstalk between individual detecting cells are serious limitation for array design and performance. Optical crosstalk is caused by the parasitic light emission of the avalanche which accompanies the photon detection process. We have studied in detail the optical emission of the avalanche photon counting structure in the silicon- and gallium-based photodiodes. The timing properties and spectral distribution of the emitted light have been measured for different operating conditions to quantify optical crosstalk. We conclude that optical crosstalk is an inherent property of avalanche photodiode operated in Geiger mode. The only way to minimize optical crosstalk in avalanche photodiode array is to build active quenching circuit with minimum response time

  14. Readout electronics for low dark count pixel detectors based on Geiger mode avalanche photodiodes fabricated in conventional CMOS technologies for future linear colliders

    International Nuclear Information System (INIS)

    Vilella, E.; Arbat, A.; Comerma, A.; Trenado, J.; Alonso, O.; Gascon, D.; Vila, A.; Garrido, L.; Dieguez, A.

    2011-01-01

    High sensitivity and excellent timing accuracy of the Geiger mode avalanche photodiodes make them ideal sensors as pixel detectors for particle tracking in high energy physics experiments to be performed in future linear colliders. Nevertheless, it is well known that these sensors suffer from dark counts and afterpulsing noise, which induce false hits (indistinguishable from event detection) as well as an increase in the necessary area of the readout system. In this work, we present a comparison between APDs fabricated in a high voltage 0.35 μm and a high integration 0.13 μm commercially available CMOS technologies that has been performed to determine which of them best fits the particle collider requirements. In addition, a readout circuit that allows low noise operation is introduced. Experimental characterization of the proposed pixel is also presented in this work.

  15. Single-Photon-Sensitive HgCdTe Avalanche Photodiode Detector

    Science.gov (United States)

    Huntington, Andrew

    2013-01-01

    The purpose of this program was to develop single-photon-sensitive short-wavelength infrared (SWIR) and mid-wavelength infrared (MWIR) avalanche photodiode (APD) receivers based on linear-mode HgCdTe APDs, for application by NASA in light detection and ranging (lidar) sensors. Linear-mode photon-counting APDs are desired for lidar because they have a shorter pixel dead time than Geiger APDs, and can detect sequential pulse returns from multiple objects that are closely spaced in range. Linear-mode APDs can also measure photon number, which Geiger APDs cannot, adding an extra dimension to lidar scene data for multi-photon returns. High-gain APDs with low multiplication noise are required for efficient linear-mode detection of single photons because of APD gain statistics -- a low-excess-noise APD will generate detectible current pulses from single photon input at a much higher rate of occurrence than will a noisy APD operated at the same average gain. MWIR and LWIR electron-avalanche HgCdTe APDs have been shown to operate in linear mode at high average avalanche gain (M > 1000) without excess multiplication noise (F = 1), and are therefore very good candidates for linear-mode photon counting. However, detectors fashioned from these narrow-bandgap alloys require aggressive cooling to control thermal dark current. Wider-bandgap SWIR HgCdTe APDs were investigated in this program as a strategy to reduce detector cooling requirements.

  16. Characterization of new hexagonal large area Geiger Avalanche Photodiodes

    International Nuclear Information System (INIS)

    Boccone, V.; Aguilar, J.A.; Della Volpe, D.; Christov, A.; Montaruli, T.; Rameez, M.; Basili, A.

    2013-06-01

    Photomultipliers (PMTs) are the standard detector for construction of the current generation of imaging Atmospheric Cherenkov Telescopes (IACTs). Despite impressive improvements in QE and reliability in the last years, these devices suffer from the limitation of being unable to operate in the partially illuminated sky (during full or partial moon periods) as the excess light leads to a significant increase in the rate of ageing of the devices themselves and consequently limit the life of the camera. A viable alternative is the large area Geiger-mode avalanche photodiodes (G-APDs also known as Silicon Photomultipliers or SiPMs) that are commercially available from different producers in various types and dimensions. The sufficiency of the maturity of this technology for application to Cherenkov Astronomy has already been demonstrated by the FACT telescope. One of the camera designs under study for the 4 m Davies Cotton Telescope foresees the utilization of a large area G-APDs coupled to non imaging light concentrators. In collaboration with Hamamatsu and deriving from their current technology, we have designed a new hexagonal shaped large area G-APD HEX S12516 which when coupled to a Winston cone of 24 degrees cutting angle allows for a pixel angular resolution of 0.25 degrees for a f/D 1.4 telescope with a diameter of 4 m. The device, available in 2 different cell size configurations (50 μm and 100 μm), is divided into 4 different channels powered in common cathode mode. A temperature sensor was included for a better temperature evaluation in the characterization phase. The first 3 prototypes were fully characterized and the results are compared to the larger area devices commercially available such as the S10985-050C (2x2 array of 3x3 mm 2 G-APDs). The photo-detection efficiency is measured applying the Poisson statistics method using pulsed LED at 7 different wavelengths from 355 to 670 nm and for different bias over-voltages (V ov ). Optical crosstalk and

  17. High performance waveguide-coupled Ge-on-Si linear mode avalanche photodiodes.

    Science.gov (United States)

    Martinez, Nicholas J D; Derose, Christopher T; Brock, Reinhard W; Starbuck, Andrew L; Pomerene, Andrew T; Lentine, Anthony L; Trotter, Douglas C; Davids, Paul S

    2016-08-22

    We present experimental results for a selective epitaxially grown Ge-on-Si separate absorption and charge multiplication (SACM) integrated waveguide coupled avalanche photodiode (APD) compatible with our silicon photonics platform. Epitaxially grown Ge-on-Si waveguide-coupled linear mode avalanche photodiodes with varying lateral multiplication regions and different charge implant dimensions are fabricated and their illuminated device characteristics and high-speed performance is measured. We report a record gain-bandwidth product of 432 GHz for our highest performing waveguide-coupled avalanche photodiode operating at 1510nm. Bit error rate measurements show operation with BER-12, in the range from -18.3 dBm to -12 dBm received optical power into a 50 Ω load and open eye diagrams with 13 Gbps pseudo-random data at 1550 nm.

  18. Hybrid AlGaN-SiC Avalanche Photodiode for Deep-UV Photon Detection

    Science.gov (United States)

    Aslam, Shahid; Herrero, Federico A.; Sigwarth, John; Goldsman, Neil; Akturk, Akin

    2010-01-01

    The proposed device is capable of counting ultraviolet (UV) photons, is compatible for inclusion into space instruments, and has applications as deep- UV detectors for calibration systems, curing systems, and crack detection. The device is based on a Separate Absorption and Charge Multiplication (SACM) structure. It is based on aluminum gallium nitride (AlGaN) absorber on a silicon carbide APD (avalanche photodiode). The AlGaN layer absorbs incident UV photons and injects photogenerated carriers into an underlying SiC APD that is operated in Geiger mode and provides current multiplication via avalanche breakdown. The solid-state detector is capable of sensing 100-to-365-nanometer wavelength radiation at a flux level as low as 6 photons/pixel/s. Advantages include, visible-light blindness, operation in harsh environments (e.g., high temperatures), deep-UV detection response, high gain, and Geiger mode operation at low voltage. Furthermore, the device can also be designed in array formats, e.g., linear arrays or 2D arrays (micropixels inside a superpixel).

  19. Studies of avalanche photodiodes for scintillating fibre tracking readout

    International Nuclear Information System (INIS)

    Fenker, H.; Thomas, J.

    1993-01-01

    Avalanche Photodiodes (APDs) operating in ''Geiger Mode'' have been studied in a fibre tracking readout environment. A fast recharge circuit has been developed for high rate data taking, and results obtained from a model fibre tracker in the test beam at Brookhaven National Laboratory are presented. A high rate calibrated light source has been developed using a commercially available laser diode and has been used to measure the efficiency of the devices. The transmission of the light from a 1mm fibre onto a 0.5mm diameter APD surface has been identified as the main problem in the use of these particular devices for scintillating fibre tracking in the Superconducting Supercollider environment. Solutions to this problem are proposed

  20. Photon-counting monolithic avalanche photodiode arrays for the super collider

    International Nuclear Information System (INIS)

    Ishaque, A.N.; Castleberry, D.E.; Rougeot, H.M.

    1994-01-01

    In fiber tracking, calorimetry, and other high energy and nuclear physics experiments, the need arises to detect an optical signal consisting of a few photons (in some cases a single photoelectron) with a detector insensitive to magnetic fields. Previous attempts to detect a single photoelectron have involved avalanche photodiodes (APDs) operated in the Geiger mode, the visible light photon counter, and a photomultiplier tube with an APD as the anode. In this paper it is demonstrated that silicon APDs, biased below the breakdown voltage, can be used to detect a signal of a few photons with conventional pulse counting circuitry at room temperature. Moderate cooling, it is further argued, could make it possible to detect a single photoelectron. Monolithic arrays of silicon avalanche photodiodes fabricated by Radiation Monitoring Devices, Inc. (RMD) were evaluated for possible use in the Super Collider detector systems. Measurements on 3 element x 3 element (2 mm pitch) APD arrays, using pulse counting circuitry with a charge sensitive amplifier (CSA) and a Gaussian filter, are reported and found to conform to a simple noise model. The model is used to obtain the optimal operating point. Experimental results are described in Section II, modeling results in Section III, and the conclusions are summarized in Section IV

  1. Single photon detection in a waveguide-coupled Ge-on-Si lateral avalanche photodiode.

    Science.gov (United States)

    Martinez, Nicholas J D; Gehl, Michael; Derose, Christopher T; Starbuck, Andrew L; Pomerene, Andrew T; Lentine, Anthony L; Trotter, Douglas C; Davids, Paul S

    2017-07-10

    We examine gated-Geiger mode operation of an integrated waveguide-coupled Ge-on-Si lateral avalanche photodiode (APD) and demonstrate single photon detection at low dark count for this mode of operation. Our integrated waveguide-coupled APD is fabricated using a selective epitaxial Ge-on-Si growth process resulting in a separate absorption and charge multiplication (SACM) design compatible with our silicon photonics platform. Single photon detection efficiency and dark count rate is measured as a function of temperature in order to understand and optimize performance characteristics in this device. We report single photon detection of 5.27% at 1310 nm and a dark count rate of 534 kHz at 80 K for a Ge-on-Si single photon avalanche diode. Dark count rate is the lowest for a Ge-on-Si single photon detector in this range of temperatures while maintaining competitive detection efficiency. A jitter of 105 ps was measured for this device.

  2. ASIC Readout Circuit Architecture for Large Geiger Photodiode Arrays

    Science.gov (United States)

    Vasile, Stefan; Lipson, Jerold

    2012-01-01

    The objective of this work was to develop a new class of readout integrated circuit (ROIC) arrays to be operated with Geiger avalanche photodiode (GPD) arrays, by integrating multiple functions at the pixel level (smart-pixel or active pixel technology) in 250-nm CMOS (complementary metal oxide semiconductor) processes. In order to pack a maximum of functions within a minimum pixel size, the ROIC array is a full, custom application-specific integrated circuit (ASIC) design using a mixed-signal CMOS process with compact primitive layout cells. The ROIC array was processed to allow assembly in bump-bonding technology with photon-counting infrared detector arrays into 3-D imaging cameras (LADAR). The ROIC architecture was designed to work with either common- anode Si GPD arrays or common-cathode InGaAs GPD arrays. The current ROIC pixel design is hardwired prior to processing one of the two GPD array configurations, and it has the provision to allow soft reconfiguration to either array (to be implemented into the next ROIC array generation). The ROIC pixel architecture implements the Geiger avalanche quenching, bias, reset, and time to digital conversion (TDC) functions in full-digital design, and uses time domain over-sampling (vernier) to allow high temporal resolution at low clock rates, increased data yield, and improved utilization of the laser beam.

  3. Study of multi-pixel Geiger-mode avalanche photodiodes as a read-out for PET

    CERN Document Server

    Musienko, Yuri; Lecoq, Paul; Reucroft, Stephen; Swain, John; Trummer, Julia

    2007-01-01

    We have studied the performance of two multi-pixel Geiger-mode APDs (recently developed by the Centre of Perspective Technologies and Apparatus (CPTA) in Moscow) with 1×1 mm2 and 3×3 mm2 sensitive area as a readout for LSO and LYSO scintillator crystals. Energy and timing spectra were measured using a 22Na γ-source. The results of this study allow us to conclude that this photodetector is a very promising candidate for PET applications.

  4. Highly enhanced avalanche probability using sinusoidally-gated silicon avalanche photodiode

    Energy Technology Data Exchange (ETDEWEB)

    Suzuki, Shingo; Namekata, Naoto, E-mail: nnao@phys.cst.nihon-u.ac.jp; Inoue, Shuichiro [Institute of Quantum Science, Nihon University, 1-8-14 Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8308 (Japan); Tsujino, Kenji [Tokyo Women' s Medical University, 8-1 Kawada-cho, Shinjuku-ku, Tokyo 162-8666 (Japan)

    2014-01-27

    We report on visible light single photon detection using a sinusoidally-gated silicon avalanche photodiode. Detection efficiency of 70.6% was achieved at a wavelength of 520 nm when an electrically cooled silicon avalanche photodiode with a quantum efficiency of 72.4% was used, which implies that a photo-excited single charge carrier in a silicon avalanche photodiode can trigger a detectable avalanche (charge) signal with a probability of 97.6%.

  5. Nano-multiplication region avalanche photodiodes and arrays

    Science.gov (United States)

    Zheng, Xinyu (Inventor); Pain, Bedabrata (Inventor); Cunningham, Thomas J. (Inventor)

    2011-01-01

    An avalanche photodiode with a nano-scale reach-through structure comprising n-doped and p-doped regions, formed on a silicon island on an insulator, so that the avalanche photodiode may be electrically isolated from other circuitry on other silicon islands on the same silicon chip as the avalanche photodiode. For some embodiments, multiplied holes generated by an avalanche reduces the electric field in the depletion region of the n-doped and p-doped regions to bring about self-quenching of the avalanche photodiode. Other embodiments are described and claimed.

  6. Modelization, fabrication and evaluation avalanche photodiodes polarized in Geiger mode for the single photon in astrophysics applications

    International Nuclear Information System (INIS)

    Pellion, D.

    2008-12-01

    The genesis of the work presented in this this is in the field of very high energy astrophysics. One century ago, scientists identified a new type of messenger coming from space: cosmic rays. This radiation consists of particles (photons or other) of very high energy which bombard the Earth permanently. The passage of cosmic radiations in the Earth's atmosphere results in the creation of briefs luminous flashes (5 ns) of very low intensity (1 pW), a Cherenkov flash, and then becomes visible on the ground. In the current state of the art the best detector of light today is the Photomultiplier tube (PMT), thanks to its characteristics of sensitivity and speed. But there are some drawbacks: low quantum efficiency, cost, weight etc. We present in this thesis a new alternative technology: silicon photon counters, made of photodiodes polarized in Geiger mode. This operating mode makes it possible to obtain an effect of multiplication comparable to that of the PMT. A physical and electrical model was developed to reproduce the behaviour of this detector. We then present in this thesis work an original technological process allowing the realization of these devices in the Center of Technology of LAAS-CNRS, with the simulation of each operation of the process. We developed a scheme for the electric characterization of the device, from the static mode to the dynamic mode, in order to check conformity with SILVACO simulations and to the initial model. Results are already excellent, given this is only a first prototype step, and comparable with the results published in the literature. These silicon devices can intervene in all the applications where there is a photomultiplier and replace it. The applications are thus very numerous and the growth of the market of these detectors is very fast. We present a first astrophysical experiment installed at the 'Pic du Midi' site which has detected Cherenkov flashes from cosmic rays with this new semiconductor technology. (author)

  7. Modelization, fabrication and evaluation avalanche photodiodes polarized in Geiger mode for the single photon in astrophysics applications; Modelisation, fabrication et evaluation des photodiodes a avalanche polarisees en mode Geiger pour la detection du photon unique dans les applications Astrophysiques

    Energy Technology Data Exchange (ETDEWEB)

    Pellion, D

    2008-12-15

    The genesis of the work presented in this this is in the field of very high energy astrophysics. One century ago, scientists identified a new type of messenger coming from space: cosmic rays. This radiation consists of particles (photons or other) of very high energy which bombard the Earth permanently. The passage of cosmic radiations in the Earth's atmosphere results in the creation of briefs luminous flashes (5 ns) of very low intensity (1 pW), a Cherenkov flash, and then becomes visible on the ground. In the current state of the art the best detector of light today is the Photomultiplier tube (PMT), thanks to its characteristics of sensitivity and speed. But there are some drawbacks: low quantum efficiency, cost, weight etc. We present in this thesis a new alternative technology: silicon photon counters, made of photodiodes polarized in Geiger mode. This operating mode makes it possible to obtain an effect of multiplication comparable to that of the PMT. A physical and electrical model was developed to reproduce the behaviour of this detector. We then present in this thesis work an original technological process allowing the realization of these devices in the Center of Technology of LAAS-CNRS, with the simulation of each operation of the process. We developed a scheme for the electric characterization of the device, from the static mode to the dynamic mode, in order to check conformity with SILVACO simulations and to the initial model. Results are already excellent, given this is only a first prototype step, and comparable with the results published in the literature. These silicon devices can intervene in all the applications where there is a photomultiplier and replace it. The applications are thus very numerous and the growth of the market of these detectors is very fast. We present a first astrophysical experiment installed at the 'Pic du Midi' site which has detected Cherenkov flashes from cosmic rays with this new semiconductor technology

  8. 25-Gbit/s burst-mode optical receiver using high-speed avalanche photodiode for 100-Gbit/s optical packet switching.

    Science.gov (United States)

    Nada, Masahiro; Nakamura, Makoto; Matsuzaki, Hideaki

    2014-01-13

    25-Gbit/s error-free operation of an optical receiver is successfully demonstrated against burst-mode optical input signals without preambles. The receiver, with a high-sensitivity avalanche photodiode and burst-mode transimpedance amplifier, exhibits sufficient receiver sensitivity and an extremely quick response suitable for burst-mode operation in 100-Gbit/s optical packet switching.

  9. Study and realization of pixelated APD Geiger photodetectors of very high sensitivity for Very High Energy gamma astronomy

    International Nuclear Information System (INIS)

    Jradi, K.

    2010-07-01

    Very High Energy gamma ray astronomy uses till now exclusively as detector the Photomultiplier Tube (PMT) to collect weak light flux of atmospheric showers. But an alternative is now emerging: Avalanche Photodiodes polarized in Geiger mode called 'Geiger-APD'. The PMT is a detector designed in the 70's which presents many advantages but also suffers from several drawbacks: size, weight, cost, sensitivity to magnetic field but especially difficulty to realize its pixelation in matrix. Geiger-APDs are semi-conductor devices made of PN junction integrated in a special technology to detect very low light flux, thanks to the polarization beyond the avalanche voltage. Geiger-APD presents very high photoelectron gain (∼106) strongly dependant on the polarization voltage beyond avalanche. These photodiodes present many advantages with respect to PMT, mainly as concerns miniaturization for applications based on imaging, such as the detection of Cerenkov flashes in gamma ray astronomy. In this thesis, we present the study, the design and the realization of a technological structure, based on Silicon. This structure has shown reliability to detect weak luminous flux with breakdown voltage at 12 V and dark current below 10 pA at breakdown. We also developed several models, physical and electrical, necessary to the technological optimization, as well to the development of control and readout circuits, i.e. the basis of any imaging technology. The work presented here consists in the study, the design and the realization of a matrix of high sensitivity pixels. A project of a Cerenkov telescope based on this innovative technology is also presented. (author)

  10. Scintillator counters with multi-pixel avalanche photodiode readout for the ND280 detector of the T2K experiment

    International Nuclear Information System (INIS)

    Mineev, O.; Afanasjev, A.; Bondarenko, G.; Golovin, V.; Gushchin, E.; Izmailov, A.; Khabibullin, M.; Khotjantsev, A.; Kudenko, Yu.; Kurimoto, Y.; Kutter, T.; Lubsandorzhiev, B.; Mayatski, V.; Musienko, Yu.; Nakaya, T.; Nobuhara, T.; Shaibonov, B.A.J.; Shaikhiev, A.; Taguchi, M.; Yershov, N.; Yokoyama, M.

    2007-01-01

    The Tokai-to-Kamioka (T2K) experiment is a second generation long baseline neutrino oscillation experiment which aims at a sensitive search for ν e appearance. The main design features of the T2K near neutrino detectors located at 280m from the target are presented, and the scintillator counters are described. The counters are readout via WLS fibers embedded into S-shaped grooves in the scintillator from both ends by multi-pixel avalanche photodiodes operating in a limited Geiger mode. Operating principles and results of tests of photosensors with a sensitive area of 1mm 2 are presented. A time resolution of 1.75ns, a spatial resolution of 9.9-12.4cm, and a detection efficiency for minimum ionizing particles of more than 99% were obtained for scintillator detectors in a beam test

  11. Linear Mode HgCdTe Avalanche Photodiodes for Photon Counting Applications

    Science.gov (United States)

    Sullivan, William, III; Beck, Jeffrey; Scritchfield, Richard; Skokan, Mark; Mitra, Pradip; Sun, Xiaoli; Abshire, James; Carpenter, Darren; Lane, Barry

    2015-01-01

    An overview of recent improvements in the understanding and maturity of linear mode photon counting with HgCdTe electron-initiated avalanche photodiodes is presented. The first HgCdTe LMPC 2x8 format array fabricated in 2011 with 64 micron pitch was a remarkable success in terms of demonstrating a high single photon signal to noise ratio of 13.7 with an excess noise factor of 1.3-1.4, a 7 ns minimum time between events, and a broad spectral response extending from 0.4 micron to 4.2 micron. The main limitations were a greater than 10x higher false event rate than expected of greater than 1 MHz, a 5-7x lower than expected APD gain, and a photon detection efficiency of only 50% when greater than 60% was expected. This paper discusses the reasons behind these limitations and the implementation of their mitigations with new results.

  12. Investigation of avalanche photodiodes

    Energy Technology Data Exchange (ETDEWEB)

    Si Mohand, D.; Benhammou, Y.; Depasse, P.; Goyot, M.; Ille, B.; Linard, E.; Martin, F.; Musienko, Y.

    1996-06-01

    Some characteristics and performances of a set of nine Hamamatsu avalanche photodiodes have been investigated. These APDs have equipped a small 3x3 PbWO{sub 4} crystal matrix in X3 beam during the summer of 1995. This note summarizes the main results of this work. An electromagnetic calorimeter with a high resolution is necessary to search for the Higgs if it has a mass between 80 and 160 GeV. A PbWO{sub 4} crystal option has been chosen by the CMS collaboration to achieve this task. The light is collected and converted into an electric charge by an Avalanche Photodiode (APD) followed by a fast preamplifier. The advantage of the APDs is that they are not sensitive to the strong magnetic field when compared to photomultipliers and they are a small nuclear counter effect when compared to PIN diodes. In this study, we have tested nine low capacitance Hamamatsu APDs (S5345) received in spring, 1995 with an area of 0.2 cm{sup 2}. We have measured the capacitance and dark current for each APD. The gain measurements have also been done with gamma sources, continuous and pulsed light. The gain sensitivity versus bias and temperature have also been investigated succinctly. (author). 8 refs., 16 figs., 1 tab.

  13. Investigation of avalanche photodiodes

    International Nuclear Information System (INIS)

    Si Mohand, D.; Benhammou, Y.; Depasse, P.; Goyot, M.; Ille, B.; Linard, E.; Martin, F.; Musienko, Y.

    1996-06-01

    Some characteristics and performances of a set of nine Hamamatsu avalanche photodiodes have been investigated. These APDs have equipped a small 3x3 PbWO 4 crystal matrix in X3 beam during the summer of 1995. This note summarizes the main results of this work. An electromagnetic calorimeter with a high resolution is necessary to search for the Higgs if it has a mass between 80 and 160 GeV. A PbWO 4 crystal option has been chosen by the CMS collaboration to achieve this task. The light is collected and converted into an electric charge by an Avalanche Photodiode (APD) followed by a fast preamplifier. The advantage of the APDs is that they are not sensitive to the strong magnetic field when compared to photomultipliers and they are a small nuclear counter effect when compared to PIN diodes. In this study, we have tested nine low capacitance Hamamatsu APDs (S5345) received in spring, 1995 with an area of 0.2 cm 2 . We have measured the capacitance and dark current for each APD. The gain measurements have also been done with gamma sources, continuous and pulsed light. The gain sensitivity versus bias and temperature have also been investigated succinctly. (author). 8 refs., 16 figs., 1 tab

  14. Characterization of midwave infrared InSb avalanche photodiode

    Energy Technology Data Exchange (ETDEWEB)

    Abautret, J., E-mail: johan.abautret@ies.univ-montp2.fr; Evirgen, A. [Université Montpellier, IES, UMR 5214, F-34095 Montpellier (France); CNRS, IES, UMR 5214, F-34095 Montpellier (France); SOFRADIR, BP 21, 38113 Veurey-Voroize (France); Perez, J. P.; Christol, P. [Université Montpellier, IES, UMR 5214, F-34095 Montpellier (France); CNRS, IES, UMR 5214, F-34095 Montpellier (France); Rothman, J. [CEA-LETI, 17 rue des Martyrs, 38054 Grenoble Cedex 9 (France); Cordat, A. [SOFRADIR, BP 21, 38113 Veurey-Voroize (France)

    2015-06-28

    This paper focuses on the InSb material potential for the elaboration of Avalanche Photodiodes (APD) for high performance infrared imaging applications, both in passive or active mode. The first InSb electron-APD structure was grown by molecular beam epitaxy, processed and electrically characterized. The device performances are at the state of the art for the InSb epi-diode technology, with a dark current density J(−50 mV) = 32 nA/cm{sup 2} at 77 K. Then, a pure electron injection was performed, and an avalanche gain, increasing exponentially, was observed with a gain value near 3 at −4 V at 77 K. The Okuto–Crowell model was used to determine the electron ionization coefficient α(E) in InSb, and the InSb gain behavior is compared with the one of InAs and MCT APDs.

  15. Large area avalanche MRS-photodiodes for nuclear spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ermalitski, F A; Zalesski, V B

    1996-12-31

    Problems of application of avalanche photodiodes (APD) in readout systems of nuclear spectrometers are considered. APD`s with a large sensitive area of a diameter 1-5 mm and a high multiplication coefficient 200-1000 are created. MPS-photodiodes provide for the energy resolution 80% at temperature 231 K for detecting gamma-quanta with energy 662 keV. 4 refs.

  16. Update on Linear Mode Photon Counting with the HgCdTe Linear Mode Avalanche Photodiode

    Science.gov (United States)

    Beck, Jeffrey D.; Kinch, Mike; Sun, Xiaoli

    2014-01-01

    The behavior of the gain-voltage characteristic of the mid-wavelength infrared cutoff HgCdTe linear mode avalanche photodiode (e-APD) is discussed both experimentally and theoretically as a function of the width of the multiplication region. Data are shown that demonstrate a strong dependence of the gain at a given bias voltage on the width of the n- gain region. Geometrical and fundamental theoretical models are examined to explain this behavior. The geometrical model takes into account the gain-dependent optical fill factor of the cylindrical APD. The theoretical model is based on the ballistic ionization model being developed for the HgCdTe APD. It is concluded that the fundamental theoretical explanation is the dominant effect. A model is developed that combines both the geometrical and fundamental effects. The model also takes into account the effect of the varying multiplication width in the low bias region of the gain-voltage curve. It is concluded that the lower than expected gain seen in the first 2 × 8 HgCdTe linear mode photon counting APD arrays, and higher excess noise factor, was very likely due to the larger than typical multiplication region length in the photon counting APD pixel design. The implications of these effects on device photon counting performance are discussed.

  17. Avalanche photodiodes for ISABELLE detectors

    International Nuclear Information System (INIS)

    Strand, R.C.

    1979-01-01

    At ISABELLE some requirements for detecting bursts of photons are not met by standard photomultiplier tubes. The characteristics of immunity to magnetic fields, small size (few mm), low power consumption (approx. 100 mW), insensitivity to optical overloads, and wide dynamic range (approx. 60 dB) are achieved with difficulty, if at all, with PMTs. These are characteristics of the solid state avalanche photodiode (APD), the preferred detector for light-wave communications. Successful field tests with APD detectors stimulated the design of standard optical-fiber communication systems to replace wire carriers by the early 1980's. In other characteristics, i.e., counting rate, pulse-height resolution, effective quantum efficiency, detection efficiency, and reliability, bare APDs are equivalent to standard PMTs. APDs with currently available amplifiers cannot resolve single photoelectrons but they could provide reasonable detection efficiencies and pulse-height resolution for packets of approx. > 100 photons. Commercially available APDs can cost up to 100 times as much as PMTs per active area, but they are potentially much cheaper. Six topics are discussed: (1) detectors for light-wave communication and detectors for particles, (2) avalanche photodiodes, (3) commercially available APDs, (4) dynamic response of PMTs and bare APDs, (5) photon counting with cold APDs, and (6) conclusions and recommendations

  18. Linear LIDAR versus Geiger-mode LIDAR: impact on data properties and data quality

    Science.gov (United States)

    Ullrich, A.; Pfennigbauer, M.

    2016-05-01

    LIDAR has become the inevitable technology to provide accurate 3D data fast and reliably even in adverse measurement situations and harsh environments. It provides highly accurate point clouds with a significant number of additional valuable attributes per point. LIDAR systems based on Geiger-mode avalanche photo diode arrays, also called single photon avalanche photo diode arrays, earlier employed for military applications, now seek to enter the commercial market of 3D data acquisition, advertising higher point acquisition speeds from longer ranges compared to conventional techniques. Publications pointing out the advantages of these new systems refer to the other category of LIDAR as "linear LIDAR", as the prime receiver element for detecting the laser echo pulses - avalanche photo diodes - are used in a linear mode of operation. We analyze the differences between the two LIDAR technologies and the fundamental differences in the data they provide. The limitations imposed by physics on both approaches to LIDAR are also addressed and advantages of linear LIDAR over the photon counting approach are discussed.

  19. Optical fibers and avalanche photodiodes for scintillator counters

    International Nuclear Information System (INIS)

    Borenstein, S.R.; Palmer, R.B.; Strand, R.C.

    1980-01-01

    Fine hodoscopes can be made of new scintillating optical fibers and one half inch end-on PMT's. An avalanche photodiode with small size and immunity to magnetic fields remains as a tempting new device to be proven as a photodetector for the fibers

  20. Investigation of the performance of alpha particle counting and alpha-gamma discrimination by pulse shape with micro-pixel avalanche photodiode

    International Nuclear Information System (INIS)

    Ahmadov, G.; Madatov, R.; Sadigov, A.; Sadygov, Z.; Jafarova, E.; Ahmadov, G.; Sadygov, Z.; Olshevski, A.; Zerrouk, F.; Mukhtarov, R.

    2015-01-01

    Being capable measuring small lights gives possibility to use micro-pixel avalanche photodiodes with scintillators. It is shown two prototypes to use micro-pixel avalanche photodiodes with and without scintillators as alpha and gamma counters in this paper. First prototype is to use two micro-pixel avalanche photodiodes. One for detecting alpha particles and closer to it, the second one with a thin plastic scintillator for detecting gamma rays. Second prototype is called two-layers configuration in which it is used only one micro-pixel avalanche photodiode, but two scntillators with different decay times. One can distinquish alpha particle and gamma ray events by using pulse shape discrimination techniques in the two-layer configuration. In this work an alpha particle and gamma ray counting performance of micro-pixel avalanche photodiodes without scintillators and its combination of plastic and BGO+ plastic scintillators was investigated. Obtained results showed the detection performance of the micro-pixel avalanche photodiodes in combination with plastic scintillator was about the same as conventional semiconductor detectors

  1. Pulse oximeter using a gain-modulated avalanche photodiode operated in a pseudo lock-in light detection mode

    Science.gov (United States)

    Miyata, Tsuyoshi; Iwata, Tetsuo; Araki, Tsutomu

    2006-01-01

    We propose a reflection-type pulse oximeter, which employs two pairs of a light-emitting diode (LED) and a gated avalanche photodiode (APD). One LED is a red one with an emission wavelength λ = 635 nm and the other is a near-infrared one with that λ = 945 nm, which are both driven with a pulse mode at a frequency f (=10 kHz). Superposition of a transistor-transistor-logic (TTL) gate pulse on a direct-current (dc) bias, which is set so as not exceeding the breakdown voltage of each APD, makes the APD work in a gain-enhanced operation mode. Each APD is gated at a frequency 2f (=20 kHz) and its output signal is fed into a laboratory-made lock-in amplifier that works in synchronous with the pulse modulation signal of each LED at a frequency f (=10 kHz). A combination of the gated APD and the lock-in like signal detection scheme is useful for the reflection-type pulse oximeter thanks to the capability of detecting a weak signal against a large background (BG) light.

  2. Degradation and Its Control of Ultraviolet Avalanche Photodiodes Using PEDOT:PSS/ZnSSe Organic-Inorganic Hybrid Structure

    Science.gov (United States)

    Abe, Tomoki; Uchida, Shigeto; Tanaka, Keita; Fujisawa, Takanobu; Kasada, Hirofumi; Ando, Koshi; Akaiwa, Kazuaki; Ichino, Kunio

    2018-05-01

    We investigated device degradation in PEDOT:PSS/ZnSSe organic-inorganic hybrid ultraviolet avalanche photodiodes (UV-APDs). ZnSSe/n-GaAs wafers were grown by molecular beam epitaxy, and PEDOT:PSS window layers were formed by inkjet technique. We observed rapid degradation with APD-mode stress (˜ 30 V) in the N2 (4 N) atmosphere, while we observed no marked change in forward bias current stress and photocurrent stress. In the case of a vacuum condition, we observed no detectable degradation in the dark avalanche current with APD-mode stress. Therefore, the degradation in the PEDOT:PSS/ZnSSe interface under the APD-mode stress was caused by the residual water vapor or oxygen in the N2 atmosphere and could be controlled by vacuum packaging.

  3. Multipixel geiger-mode photon detectors for ultra-weak light sources

    International Nuclear Information System (INIS)

    Campisi, A.; Cosentino, L.; Finocchiaro, P.; Pappalardo, A.; Musumeci, F.; Privitera, S.; Scordino, A.; Tudisco, S.; Fallica, G.; Sanfilippo, D.; Mazzillo, M.; Condorelli, G.; Piazza, A.; Valvo, G.; Lombardo, S.; Sciacca, E.; Bonanno, G.; Belluso, M.

    2007-01-01

    Arrays of Single Photon Avalanche Detectors (SPAD) are considered today as a possible alternative to PMTs and other semiconductor devices in several applications, like physics research, bioluminescence, Positron Emission Tomography (PET) systems, etc. We have developed and characterized a first prototype array produced by STMicroelectronics in silicon planar technology and working at low voltage (30-40 V) in Geiger mode operation. The single cell structure (size down to 20 μm) and the geometrical arrangement give rise to appealing intrinsic characteristics of the device, such as photon detection efficiency, dark count map, cross-talk effects, timing and energy resolution. New prototypes are under construction with a higher number of pixels that have a common output signal to obtain a so-called SiPM (Silicon PhotoMultiplier) configuration

  4. Impulse response measurement in the HgCdTe avalanche photodiode

    Science.gov (United States)

    Singh, Anand; Pal, Ravinder

    2018-04-01

    HgCdTe based mid-wave infrared focal plane arrays (MWIR FPAs) are being developed for high resolution imaging and range determination of distant camouflaged targets. Effect of bandgap grading on the response time in the n+/ν/p+ HgCdTe electron avalanche photodiode (e-APD) is evaluated using impulse response measurement. Gain normalized dark current density of 2 × 10-9 A/cm2 at low reverse bias for passive mode and 2 × 10-4 A/cm2 at -8 V for active mode is measured in the fabricated APD device, yielding high gain bandwidth product of 2.4 THZ at the maximum gain. Diffusion of carriers is minimized to achieve transit time limited impulse response by introducing composition grading in the HgCdTe epilayer. The noise equivalent photon performance less than one is achievable in the FPA that is suitable for active cum passive imaging applications.

  5. Readout of scintillator light with avalanche photodiodes for positron emission tomography

    International Nuclear Information System (INIS)

    Chen, Ruru; Fremout, A.; Tavernier, S.; Bruyndonckx, P.; Clement, D.; Loude, J.-F.; Morel, C.

    1999-01-01

    The noise properties and other relevant characteristics of avalanche photodiodes have been investigated with the perspective of replacing photomultiplier tubes in positron emission tomography. It is clearly demonstrated that they are a valid alternative to photomultiplier tubes in this application

  6. Radiation damage effect on avalanche photodiodes

    CERN Document Server

    Baccaro, S; Cavallari, F; Da Ponte, V; Deiters, K; Denes, P; Diemoz, M; Kirn, Th; Lintern, A L; Longo, E; Montecchi, M; Musienko, Y; Pansart, J P; Renker, D; Reucroft, S; Rosi, G; Rusack, R; Ruuska, D; Stephenson, R; Torbet, M J

    1999-01-01

    Avalanche Photodiodes have been chosen as photon sensors for the electromagnetic calorimeter of the CMS experiment at the LHC. These sensors should operate in the 4T magnetic field of the experiment. Because of the high neutron radiation in the detector extensive studies have been done by the CMS collaboration on the APD neutron radiation damage. The characteristics of these devices after irradiation have been analized, with particular attention to the quantum efficiency and the dark current. The recovery of the radiation induced dark current has been studied carefully at room temperature and at slightly lower and higher temperatures. The temperature dependence of the defects decay-time has been evaluated.

  7. Setting best practice criteria for self-differencing avalanche photodiodes in quantum key distribution

    Science.gov (United States)

    Koehler-Sidki, Alexander; Dynes, James F.; Lucamarini, Marco; Roberts, George L.; Sharpe, Andrew W.; Savory, Seb J.; Yuan, Zhiliang; Shields, Andrew J.

    2017-10-01

    In recent years, the security of avalanche photodiodes as single photon detectors for quantum key distribution has been subjected to much scrutiny. The most prominent example of this surrounds the vulnerability of such devices to blinding under strong illumination. We focus on self-differencing avalanche photodiodes, single photon detectors that have demonstrated count rates exceeding 1 GCounts/s resulting in secure key rates over 1 MBit/s. These detectors use a passive electronic circuit to cancel any periodic signals thereby enhancing detection sensitivity. However this intrinsic feature can be exploited by adversaries to gain control of the devices using illumination of a moderate intensity. Through careful experimental examinations, we define here a set of criteria for these detectors to avoid such attacks.

  8. Effects of the intrinsic layer width on the band-to-band tunneling current in p-i-n GaN-based avalanche photodiodes

    International Nuclear Information System (INIS)

    Wang, Ling; Bao, Xichang; Zhang, Wenjing; Li, Chao; Yuan, Yonggang; Xu, Jintong; Zhang, Yan; Li, Xiangyang

    2009-01-01

    Dark current is critical for GaN-based avalanche photodiodes because it significantly increases the noise current and limits the multiplication factor. It has been found that the band-to-band tunneling current is the dominant origin of the dark current for avalanche photodiodes at the onset of breakdown voltage. Experimentally, for GaN-based avalanche photodiodes with a thinner intrinsic layer, the dark current increases nearly exponentially with the applied voltage even at a lower bias voltage. In this paper, the intrinsic layer (i-layer) width of GaN-based avalanche photodiodes has been varied to study its effect on the band-to-band tunneling current. A widely used equation was used to calculate the band-to-band tunneling current of avalanche photodiodes with different i-layer widths (i-layer 0.1 µm, 0.2 µm and 0.4 µm). At −40 V, the band-to-band tunneling current significantly reduces by a magnitude of 10 −15 A with an increase in the i-layer width from 0.1 µm to 0.2 µm, and a magnitude of 10 −29 A with an increase in the i-layer width from 0.2 µm to 0.4 µm. Then, GaN-based avalanche photodiodes (i-layer 0.1 µm, 0.2 µm and 0.4 µm) with different-sized mesa were fabricated. Also, the measurement of dark current of all three different structures was performed, and their multiplication factors were given

  9. SPADs in CMOS : When Physics Meets Engineering

    NARCIS (Netherlands)

    Charbon, E.

    2011-01-01

    Single-photon avalanche diodes (SPADs) are a class of photodiodes biased above breakdown; in this mode of operation, known as Geiger mode, the devices are capable of detecting one or more photons with high timing accuracy. SPADs are useful in a variety of applications where picosecond timing

  10. An improved design for AlGaN solar-blind avalanche photodiodes with enhanced avalanche ionization

    International Nuclear Information System (INIS)

    Tang Yin; Cai Qing; Chen Dun-Jun; Lu Hai; Zhang Rong; Zheng You-Dou; Yang Lian-Hong; Dong Ke-Xiu

    2017-01-01

    To enhance the avalanche ionization, we designed a new separate absorption and multiplication AlGaN solar-blind avalanche photodiode (APD) by using a high/low-Al-content AlGaN heterostructure as the multiplication region instead of the conventional AlGaN homogeneous layer. The calculated results show that the designed APD with Al 0.3 Ga 0.7 N/Al 0.45 Ga 0.55 N heterostructure multiplication region exhibits a 60% higher gain than the conventional APD and a smaller avalanche breakdown voltage due to the use of the low-Al-content Al 0.3 Ga 0.7 N which has about a six times higher hole ionization coefficient than the high-Al-content Al 0.45 Ga 0.55 N. Meanwhile, the designed APD still remains a good solar-blind characteristic by introducing a quarter-wave AlGaN/AlN distributed Bragg reflectors structure at the bottom of the device. (paper)

  11. X-ray spectrometry with Peltier-cooled large area avalanche photodiodes

    International Nuclear Information System (INIS)

    Fernandes, L.M.P.; Lopes, J.A.M.; Santos, J.M.F. dos; Conde, C.A.N.

    2004-01-01

    Performance characteristics of the response of a Peltier-cooled large-area avalanche photodiode are investigated. Detector gain, energy linearity, energy resolution and minimum detectable energy are studied at different operation temperatures. Detector energy resolution and lowest detectable X-ray energy present a strong improvement as the operation temperature is reduced from 25 to 15 deg. C and slower improvements are achieved for temperatures below 10 deg. C

  12. Application of An Avalanche Photodiode in Synchrotron-Based Ultra-fast X-Radiography

    International Nuclear Information System (INIS)

    Cheong, S.-K.; Liu Jinyuan; Wang Jin; Powell, Christopher F.

    2004-01-01

    A possibility of using avalanche photodiode has been investigated while operated in current or continuous wave mode to accommodate high-intensity synchrotron x-ray beams in an ultra-fast x-radiography. To achieve a time resolution of 1 μs or better in a time-resolved x-radiograhic experiment, the entire time-sequence of the APD response to the pulsed synchrotron x-ray beam is recorded with time resolution of 1-2 ns. We have characterized the APD detector in the continuous wave mode to reveal its linearity, signal to noise ratio, and the time response with various circuit configurations. We have demonstrated that signal-to-noise ratio better than 1000 can be achieved, which is limited only by Poisson statistics. These detectors, coupled with finely focused x-rays, have been used to study structure and dynamics of supersonic fuel sprays with 50 μm-spatial resolution and μs-temporal resolution in the region close to an injection nozzle

  13. Geiger-mode APD camera system for single-photon 3D LADAR imaging

    Science.gov (United States)

    Entwistle, Mark; Itzler, Mark A.; Chen, Jim; Owens, Mark; Patel, Ketan; Jiang, Xudong; Slomkowski, Krystyna; Rangwala, Sabbir

    2012-06-01

    The unparalleled sensitivity of 3D LADAR imaging sensors based on single photon detection provides substantial benefits for imaging at long stand-off distances and minimizing laser pulse energy requirements. To obtain 3D LADAR images with single photon sensitivity, we have demonstrated focal plane arrays (FPAs) based on InGaAsP Geiger-mode avalanche photodiodes (GmAPDs) optimized for use at either 1.06 μm or 1.55 μm. These state-of-the-art FPAs exhibit excellent pixel-level performance and the capability for 100% pixel yield on a 32 x 32 format. To realize the full potential of these FPAs, we have recently developed an integrated camera system providing turnkey operation based on FPGA control. This system implementation enables the extremely high frame-rate capability of the GmAPD FPA, and frame rates in excess of 250 kHz (for 0.4 μs range gates) can be accommodated using an industry-standard CameraLink interface in full configuration. Real-time data streaming for continuous acquisition of 2 μs range gate point cloud data with 13-bit time-stamp resolution at 186 kHz frame rates has been established using multiple solid-state storage drives. Range gate durations spanning 4 ns to 10 μs provide broad operational flexibility. The camera also provides real-time signal processing in the form of multi-frame gray-scale contrast images and single-frame time-stamp histograms, and automated bias control has been implemented to maintain a constant photon detection efficiency in the presence of ambient temperature changes. A comprehensive graphical user interface has been developed to provide complete camera control using a simple serial command set, and this command set supports highly flexible end-user customization.

  14. Proof-of-concept and feasibility demonstrations for an avalanche photodiode/photoelastic modulator-based imaging polarimeter

    Data.gov (United States)

    National Aeronautics and Space Administration — Building on the successful heritage of JPL’s Multiangle SpectroPolarimetric Imager (MSPI), we propose infusing HgCdTe avalanche photodiode (APD) array technology...

  15. Determination of the excess noise of avalanche photodiodes integrated in 0.35-μm CMOS technologies

    Science.gov (United States)

    Jukić, Tomislav; Brandl, Paul; Zimmermann, Horst

    2018-04-01

    The excess noise of avalanche photodiodes (APDs) integrated in a high-voltage (HV) CMOS process and in a pin-photodiode CMOS process, both with 0.35-μm structure sizes, is described. A precise excess noise measurement technique is applied using a laser source, a spectrum analyzer, a voltage source, a current meter, a cheap transimpedance amplifier, and a personal computer with a MATLAB program. In addition, usage for on-wafer measurements is demonstrated. The measurement technique is verified with a low excess noise APD as a reference device with known ratio k = 0.01 of the impact ionization coefficients. The k-factor of an APD developed in HV CMOS is determined more accurately than known before. In addition, it is shown that the excess noise of the pin-photodiode CMOS APD depends on the optical power for avalanche gains above 35 and that modulation doping can suppress this power dependence. Modulation doping, however, increases the excess noise.

  16. High speed, wide dynamic range analog signal processing for avalanche photodiode

    CERN Document Server

    Walder, J P; Pangaud, P

    2000-01-01

    A wide dynamic range multi-gain analog transimpedance amplifier integrated circuit has been developed for avalanche photodiode signal processing. The 96 dB input dynamic range is divided into four ranges of 12-bits each in order to provide 40 MHz analog sampled data to a 12-bits ADC. This concept which has been integrated in both BiCMOS and full complementary bipolar technology along with fitted design techniques will be presented.

  17. High speed, wide dynamic range analog signal processing for avalanche photodiode

    International Nuclear Information System (INIS)

    Walder, J.P.; El Mamouni, Houmani; Pangaud, Patrick

    2000-01-01

    A wide dynamic range multi-gain analog transimpedance amplifier integrated circuit has been developed for avalanche photodiode signal processing. The 96 dB input dynamic range is divided into four ranges of 12-bits each in order to provide 40 MHz analog sampled data to a 12-bits ADC. This concept which has been integrated in both BiCMOS and full complementary bipolar technology along with fitted design techniques will be presented

  18. High speed, wide dynamic range analog signal processing for avalanche photodiode

    Energy Technology Data Exchange (ETDEWEB)

    Walder, J.P. E-mail: walder@in2p3.fr; El Mamouni, Houmani; Pangaud, Patrick

    2000-03-11

    A wide dynamic range multi-gain analog transimpedance amplifier integrated circuit has been developed for avalanche photodiode signal processing. The 96 dB input dynamic range is divided into four ranges of 12-bits each in order to provide 40 MHz analog sampled data to a 12-bits ADC. This concept which has been integrated in both BiCMOS and full complementary bipolar technology along with fitted design techniques will be presented.

  19. The properties of ITE's silicon avalanche photodiodes within the spectral range used in scintillation detection

    CERN Document Server

    Wegrzecka, I

    1999-01-01

    The design and properties of 3 mm silicon avalanche photodiodes developed at ITE are presented. Their performance parameters within the spectral range applicable in scintillation detection (400-700 nm) are discussed and compared to those for near infrared radiation.

  20. The properties of ITE's silicon avalanche photodiodes within the spectral range used in scintillation detection

    Science.gov (United States)

    Wegrzecka, Iwona; Wegrzecki, Maciej

    1999-04-01

    The design and properties of 3 mm silicon avalanche photodiodes developed at ITE are presented. Their performance parameters within the spectral range applicable in scintillation detection (400-700 nm) are discussed and compared to those for near infrared radiation.

  1. Novel micropixel avalanche photodiodes (MAPD) with superhigh pixel density

    International Nuclear Information System (INIS)

    Anfimov, N.; Chirikov-Zorin, I.; Dovlatov, A.

    2010-01-01

    In many detectors based on scintillators the photomultiplier tubes (PMTs) are used as photodetectors. At present photodiodes are finding wide application. Solid state photodetectors allow operation in strong magnetic fields that are often present in applications, e.g., some calorimeters operating near magnets, combined PET and MRT, etc. The photon detection efficiency (PDE) of photodiodes may reach values a few times higher than that of PMTs. Also, they are rigid, compact and have relatively low operating voltage. In the last few years Micropixel Avalanche PhotoDiodes (MAPDs) have been developed and started to be used. The MAPD combines a lot of advantages of semiconductor photodetectors and has a high gain, which is close to that of the PMT. Yet, they have some disadvantages, and one of them is a limited dynamic range that corresponds to a total number of pixels. The novel deep microwell MAPD with high pixel density produced by Zecotek Company partially avoids this disadvantage. In this paper characteristics of these photodetectors are presented in comparison with the PMT characteristics. The results refer to measurements of the gain, PDE, cross-talks, photon counting and applications: beam test results of two different 'Shashlyk' EM calorimeters for COMPASS (CERN) and NICA-MPD (JINR) with the MAPD readout and a possibility of using the MAPD in PET

  2. Ultralow noise midwave infrared InAs-GaSb strain layer superlattice avalanche photodiode

    International Nuclear Information System (INIS)

    Mallick, Shubhrangshu; Banerjee, Koushik; Ghosh, Siddhartha; Plis, Elena; Rodriguez, Jean Baptiste; Krishna, Sanjay; Grein, Christoph

    2007-01-01

    Eye-safe midwavelength infrared InAs-GaSb strain layer superlattice p + -n - -n homojunction avalanche photodiodes (APDs) grown by solid source molecular beam epitaxy were fabricated and characterized. Maximum multiplication gain of 1800 was measured at -20 V at 77 K. Excess noise factors between 0.8 and 1.2 were measured up to gain of 300. Gain of 200 was measured at 120 K. Exponential nature of the gain as a function of reverse bias along with low excess noise factor at higher gain confirms single carrier electron-only impact ionization in the avalanche regime. Decrease in the multiplication gain at higher temperatures correlates with standard APD characteristics

  3. Upgrade of the CMS hardron calorimeter for an upgraded LHC

    OpenAIRE

    Anderson, Jake

    2012-01-01

    The CMS barrel and endcap hadron calorimeters (Hcal) upgrading the current photo-sensors are hybrid photodiodes (HPDs) to meet the demands of the upgraded luminosity of the LHC. A key aspect of the Hcal upgrade is to add longitudinal segmentation to improve background rejection, energy resolution, and electron isolation at L1 trigger. The increased segmentation can be achieved by replacing the HPD's with multi-pixel Geiger-mode avalanche photodiodes. The upgraded electron...

  4. CMOS integrated avalanche photodiodes and frequency-mixing optical sensor front end for portable NIR spectroscopy instruments.

    Science.gov (United States)

    Yun, Ruida; Sthalekar, Chirag; Joyner, Valencia M

    2011-01-01

    This paper presents the design and measurement results of two avalanche photodiode structures (APDs) and a novel frequency-mixing transimpedance amplifier (TIA), which are key building blocks towards a monolithically integrated optical sensor front end for near-infrared (NIR) spectroscopy applications. Two different APD structures are fabricated in an unmodified 0.18 \\im CMOS process, one with a shallow trench isolation (STI) guard ring and the other with a P-well guard ring. The APDs are characterized in linear mode. The STI bounded APD demonstrates better performance and exhibits 3.78 A/W responsivity at a wavelength of 690 nm and bias voltage of 10.55 V. The frequency-mixing TIA (FM-TIA) employs a T-feedback network incorporating gate-controlled transistors for resistance modulation, enabling the simultaneous down-conversion and amplification of the high frequency modulated photodiode (PD) current. The TIA achieves 92 dS Ω conversion gain with 0.5 V modulating voltage. The measured IIP(3) is 10.6/M. The amplifier together with the 50 Ω output buffer draws 23 mA from a1.8 V power supply.

  5. Propagation velocity of an avalanche along the anode wire in a Geiger-Mueller counter filled with Q-gas at 1 ATM

    International Nuclear Information System (INIS)

    Matsuda, Kazunori; Sanada, Junpei

    1990-01-01

    Simple methods were applied to investigate the characteristics of a Geiger-Mueller counter with Q-gas flowing at 1 atm. The propagation velocity of the photon-aided avalanche along the anode wire depends linearly on the strength of the electric field in the counter. Its fluctuation (FWHM) as a function of distance between the source position and the end point is discussed. (orig.)

  6. Single-photon semiconductor photodiodes for distributed optical fiber sensors: state of the art and perspectives

    Science.gov (United States)

    Ripamonti, Giancarlo; Lacaita, Andrea L.

    1993-03-01

    The extreme sensitivity and time resolution of Geiger-mode avalanche photodiodes (GM- APDs) have already been exploited for optical time domain reflectometry (OTDR). Better than 1 cm spatial resolution in Rayleigh scattering detection was demonstrated. Distributed and quasi-distributed optical fiber sensors can take advantage of the capabilities of GM-APDs. Extensive studies have recently disclosed the main characteristics and limitations of silicon devices, both commercially available and developmental. In this paper we report an analysis of the performance of these detectors. The main characteristics of GM-APDs of interest for distributed optical fiber sensors are briefly reviewed. Command electronics (active quenching) is then introduced. The detector timing performance sets the maximum spatial resolution in experiments employing OTDR techniques. We highlight that the achievable time resolution depends on the physics of the avalanche spreading over the device area. On the basis of these results, trade-off between the important parameters (quantum efficiency, time resolution, background noise, and afterpulsing effects) is considered. Finally, we show first results on Germanium devices, capable of single photon sensitivity at 1.3 and 1.5 micrometers with sub- nanosecond time resolution.

  7. Scintillation detector composed by new type of avalanche photodiode and CsI(Tl) crystal

    International Nuclear Information System (INIS)

    He Jingtang; Chen Duanbao; Li Zuhao; Mao Yufang; Dong Xiaoli

    1996-01-01

    Using S5345 type of avalanche photodiode produced by Hamamatsu for the CsI(Tl) crystal readout, the spectrum of γ ray were measured. Energy resolution of 6.8% for 1.27 MeV γ ray from 22 Na source was obtained. The relation between energy resolution and coupling area, dimension of crystal, shaping time and bias were measured

  8. Behaviour of large-area avalanche photodiodes under intense magnetic fields for VUV- visible- and X-ray photon detection

    International Nuclear Information System (INIS)

    Fernandes, L.M.P.; Antognini, A.; Boucher, M.; Conde, C.A.N.; Huot, O.; Knowles, P.; Kottmann, F.; Ludhova, L.; Mulhauser, F.; Pohl, R.; Schaller, L.A.; Santos, J.M.F. dos; Taqqu, D.; Veloso, J.F.C.A.

    2003-01-01

    The behaviour of large-area avalanche photodiodes for X-rays, visible and vacuum-ultra-violet (VUV) light detection in magnetic fields up to 5 T is described. For X-rays and visible light detection, the photodiode pulse amplitude and energy resolution were unaffected from 0 to 5 T, demonstrating the insensitivity of this type of detector to strong magnetic fields. For VUV light detection, however, the photodiode relative pulse amplitude decreases with increasing magnetic field intensity reaching a reduction of about 24% at 5 T, and the energy resolution degrades noticeably with increasing magnetic field

  9. Practical photon number detection with electric field-modulated silicon avalanche photodiodes.

    Science.gov (United States)

    Thomas, O; Yuan, Z L; Shields, A J

    2012-01-24

    Low-noise single-photon detection is a prerequisite for quantum information processing using photonic qubits. In particular, detectors that are able to accurately resolve the number of photons in an incident light pulse will find application in functions such as quantum teleportation and linear optics quantum computing. More generally, such a detector will allow the advantages of quantum light detection to be extended to stronger optical signals, permitting optical measurements limited only by fluctuations in the photon number of the source. Here we demonstrate a practical high-speed device, which allows the signals arising from multiple photon-induced avalanches to be precisely discriminated. We use a type of silicon avalanche photodiode in which the lateral electric field profile is strongly modulated in order to realize a spatially multiplexed detector. Clearly discerned multiphoton signals are obtained by applying sub-nanosecond voltage gates in order to restrict the detector current.

  10. Spectral dependence of the main parameters of ITE silicon avalanche photodiodes

    Science.gov (United States)

    Wegrzecka, Iwona; Grynglas, Maria; Wegrzecki, Maciej

    2001-08-01

    New applications for avalanche photodiodes (APDs) as in systems using visible radiation, have prompted the need for the evaluation of detection properties of ITE APDs in the 400 divided by 700 nm spectral range. The paper presents the method and result of studies on the spectral dependence of the gain, dark and noise currents, sensitivity and excess noise factor of ITE APDs. The studies have shown that ITE APDs optimized for the near IR radiation can be effectively applied in the detection of radiation above the 500 nm wavelength.

  11. Novel micropixel avalanche photodiodes (MAPD) with super high pixel density

    International Nuclear Information System (INIS)

    Anfimov, N.; Chirikov-Zorin, I.; Dovlatov, A.; Gavrishchuk, O.; Guskov, A.; Khovanskiy, N.; Krumshtein, Z.; Leitner, R.; Meshcheryakov, G.; Nagaytsev, A.; Olchevski, A.; Rezinko, T.; Sadovskiy, A.; Sadygov, Z.; Savin, I.; Tchalyshev, V.; Tyapkin, I.; Yarygin, G.; Zerrouk, F.

    2011-01-01

    In many detectors based on scintillators the photomultiplier tubes (PMTs) are used as photodetectors. At present photodiodes are finding wide application. Solid state photodetectors allow operation in strong magnetic fields that are often present in applications, e.g. some calorimeters operating near magnets, combined PET and MRT, etc. The photon detection efficiency (PDE) of photodiodes may reach values a few times higher than that of PMTs. Also, they are rigid, compact and have relatively low operating voltage. In the last few years Micropixel Avalanche PhotoDiodes (MAPD) have been developed and started to be used. The MAPD combines a lot of advantages of semiconductor photodetectors and has a high gain, which is close to that of the PMT. Yet, they have some disadvantages, and one of them is a limited dynamic range that corresponds to a total number of pixels. The novel deep microwell MAPD with high pixel density produced by the Zecotek Company partially avoids this disadvantage. In this paper characteristics of these photodetectors are presented in comparison with the PMT characteristics. The results refer to measurements of the gain, PDE, cross-talks, photon counting and applications: beam test results of two different 'Shashlyk' EM calorimeters for COMPASS (CERN) and NICA-MPD (JINR) with the MAPD readout and a possibility of using the MAPD in PET.

  12. Avalanche photodiode based time-of-flight mass spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Ogasawara, Keiichi, E-mail: kogasawara@swri.edu; Livi, Stefano A.; Desai, Mihir I.; Ebert, Robert W.; McComas, David J.; Walther, Brandon C. [Southwest Research Institute, 6220 Culebra Road, San Antonio, Texas 78238 (United States)

    2015-08-15

    This study reports on the performance of Avalanche Photodiodes (APDs) as a timing detector for ion Time-of-Flight (TOF) mass spectroscopy. We found that the fast signal carrier speed in a reach-through type APD enables an extremely short timescale response with a mass or energy independent <2 ns rise time for <200 keV ions (1−40 AMU) under proper bias voltage operations. When combined with a microchannel plate to detect start electron signals from an ultra-thin carbon foil, the APD comprises a novel TOF system that successfully operates with a <0.8 ns intrinsic timing resolution even using commercial off-the-shelf constant-fraction discriminators. By replacing conventional total-energy detectors in the TOF-Energy system, APDs offer significant power and mass savings or an anti-coincidence background rejection capability in future space instrumentation.

  13. Geiger-Mode Avalanche Photodiode Arrays Integrated to All-Digital CMOS Circuits

    Science.gov (United States)

    2016-01-20

    important in photon‐starved applications, such as night vision or high‐temporal‐resolution imaging. Interest in such scenarios lead to Lincoln’s...information of interest. Lincoln Laboratory’s long-term vision is to merge these functions, so that the work of information extraction is carried...M. Boroson, David O. Caplan, Constantine J. Digenis, David R. Hearn, and Ryan C. Shoup, "Design of an Optical Photon Counting Array Receiver System

  14. Evaluation of phase sensitive detection method and Si avalanche photodiode for radiation thermometry

    International Nuclear Information System (INIS)

    Hobbs, M J; Tan, C H; Willmott, J R

    2013-01-01

    We report the evaluation of Si avalanche photodiodes (APDs) for use in radiation thermometry as an alternative to Si photodiodes. We compared their performance when operated under phase sensitive detection (PSD), where the signal is modulated, and direct detection (DD) methods. A Si APD was compared with a Si photodiode with reference black body temperatures of 275 to 600°C, in terms of the mean output voltage and signal-to-noise ratio (SNR), measured at different APD gain values. We found that using both PSD and DD methods, the high internal gain of the Si APD achieved a lower minimum detection temperature in order to satisfy a specific minimum output voltage of the detector-preamplifier combination employed. The use of PSD over DD for the Si APD allowed for improved performance of the thermometer, with a lower minimum measurable temperature, as well as improvement in the SNR. For instance we found that at 350°C, the Si APD biased at 150 V using PSD can provide ∼ 88 times enhancement in the system SNR over that of a Si photodiode using DD. A corresponding temperature error of ±0.05°C was achieved using the APD with PSD compared to an error of ±2.75°C measured using the Si photodiode with DD.

  15. Study on the property of the avalanche photodiode as the readout component for scintillation crystals

    International Nuclear Information System (INIS)

    He Jingtang; Chen Duanbao; Zhu Guoyi; Mao Yufang; Dong Xiaoli; Li Zuhao

    1996-01-01

    The new avalanche photodiode (APD) and a CsI(Tl) crystal formed a scintillation detector. The energy spectrum of γ rays was measured by this detector. The measured results were compared with that measured by photomultiplier. Our plan is to use APD as PbWO 4 readout component for forward luminosity electromagnetic calorimeter at τ-C factory

  16. Single-Photon Avalanche Diodes (SPAD) in CMOS 0.35 µm technology

    Energy Technology Data Exchange (ETDEWEB)

    Pellion, D.; Jradi, K.; Brochard, N. [Le2i – CNRS/Univ. de Bourgogne, Dijon (France); Prêle, D. [APC – CNRS/Univ. Paris Diderot, Paris (France); Ginhac, D. [Le2i – CNRS/Univ. de Bourgogne, Dijon (France)

    2015-07-01

    Some decades ago single photon detection used to be the terrain of photomultiplier tube (PMT), thanks to its characteristics of sensitivity and speed. However, PMT has several disadvantages such as low quantum efficiency, overall dimensions, and cost, making them unsuitable for compact design of integrated systems. So, the past decade has seen a dramatic increase in interest in new integrated single-photon detectors called Single-Photon Avalanche Diodes (SPAD) or Geiger-mode APD. SPAD are working in avalanche mode above the breakdown level. When an incident photon is captured, a very fast avalanche is triggered, generating an easily detectable current pulse. This paper discusses SPAD detectors fabricated in a standard CMOS technology featuring both single-photon sensitivity, and excellent timing resolution, while guaranteeing a high integration. In this work, we investigate the design of SPAD detectors using the AMS 0.35 µm CMOS Opto technology. Indeed, such standard CMOS technology allows producing large surface (few mm{sup 2}) of single photon sensitive detectors. Moreover, SPAD in CMOS technologies could be associated to electronic readout such as active quenching, digital to analog converter, memories and any specific processing required to build efficient calorimeters (Silicon PhotoMultiplier – SiPM) or high resolution imagers (SPAD imager). The present work investigates SPAD geometry. MOS transistor has been used instead of resistor to adjust the quenching resistance and find optimum value. From this first set of results, a detailed study of the dark count rate (DCR) has been conducted. Our results show a dark count rate increase with the size of the photodiodes and the temperature (at T=22.5 °C, the DCR of a 10 µm-photodiode is 2020 count s{sup −1} while it is 270 count s{sup −1} at T=−40 °C for a overvoltage of 800 mV). A small pixel size is desirable, because the DCR per unit area decreases with the pixel size. We also found that the adjustment

  17. Hole-Initiated-Avalanche, Linear-Mode, Single-Photon-Sensitive Avalanche Photodetector with Reduced Excess Noise and Low Dark Count Rate, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — A radiation hard, single photon sensitive InGaAs avalanche photodiode (APD) receiver technology will be demonstrated useful for long range space based optical...

  18. Response of CMS avalanche photo-diodes to low energy neutrons

    Science.gov (United States)

    Brown, R. M.; Deiters, K.; Ingram, Q.; Renker, D.

    2012-12-01

    The response of the Avalanche Photo-diodes (APDs) installed in the CMS detector at the LHC to neutrons from 241AmBe and 252Cf sources is reported. Signals in size equivalent to those of up to 106 photo-electrons with the nominal APD gain are observed. Measurements with an APD with the protective epoxy coating removed and with the source placed behind the APD show that there is an important response due to recoil protons from neutron interactions with the hydrogen in the epoxy, in addition to signals from neutron interactions with the silicon of the diode. The effective gain of these signals is much smaller than the diode's nominal gain.

  19. A new method to improve multiplication factor in micro-pixel avalanche photodiodes with high pixel density

    Energy Technology Data Exchange (ETDEWEB)

    Sadygov, Z. [National Nuclear Research Center, Baku (Azerbaijan); Joint Institute for Nuclear Research, Dubna (Russian Federation); Ahmadov, F. [National Nuclear Research Center, Baku (Azerbaijan); Khorev, S. [Zecotek Photonics Inc., Vancouver (Canada); Sadigov, A., E-mail: saazik@yandex.ru [National Nuclear Research Center, Baku (Azerbaijan); Suleymanov, S. [National Nuclear Research Center, Baku (Azerbaijan); Madatov, R.; Mehdiyeva, R. [Institute of Radiation Problems, Baku (Azerbaijan); Zerrouk, F. [Zecotek Photonics Inc., Vancouver (Canada)

    2016-07-11

    Presented is a new model describing development of the avalanche process in time, taking into account the dynamics of electric field within the depleted region of the diode and the effect of parasitic capacitance shunting individual quenching micro-resistors on device parameters. Simulations show that the effective capacitance of a single pixel, which defines the multiplication factor, is the sum of the pixel capacitance and a parasitic capacitance shunting its quenching micro-resistor. Conclusions obtained as a result of modeling open possibilities of improving the pixel gain in micropixel avalanche photodiodes with high pixel density (or low pixel capacitance).

  20. Discrimination Voltage and Overdrive Bias Dependent Performance Evaluation of Passively Quenched SiC Single-Photon-Counting Avalanche Photodiodes

    International Nuclear Information System (INIS)

    Liu Fei; Yang Sen; Zhou Dong; Lu Hai; Zhang Rong; Zheng You-Dou

    2015-01-01

    In many critical civil and emerging military applications, low-level UV detection, sometimes at single photon level, is highly desired. In this work, a mesa-type 4H-SiC UV avalanche photodiode (APD) is designed and fabricated, which exhibits low leakage current and high avalanche gain. When studied by using a passive quenching circuit, the APD exhibits self-quenching characteristics due to its high differential resistance in the avalanche region. The single photon detection efficiency and dark count rate of the APD are evaluated as functions of discrimination voltage and over-drive voltage. The optimized operation conditions of the single photon counting APD are discussed. (paper)

  1. Non-Geiger-Mode Single-Photon Avalanche Detector with Low Excess Noise

    Science.gov (United States)

    Zhao, Kai; Lo, YuHwa; Farr, William

    2010-01-01

    This design constitutes a self-resetting (gain quenching), room-temperature operational semiconductor single-photon-sensitive detector that is sensitive to telecommunications optical wavelengths and is scalable to large areas (millimeter diameter) with high bandwidth and efficiencies. The device can detect single photons at a 1,550-nm wavelength at a gain of 1 x 10(exp 6). Unlike conventional single photon avalanche detectors (SPADs), where gain is an extremely sensitive function to the bias voltage, the multiplication gain of this device is stable at 1 x 10(exp 6) over a wide range of bias from 30.2 to 30.9 V. Here, the multiplication gain is defined as the total number of charge carriers contained in one output pulse that is triggered by the absorption of a single photon. The statistics of magnitude of output signals also shows that the device has a very narrow pulse height distribution, which demonstrates a greatly suppressed gain fluctuation. From the histograms of both pulse height and pulse charge, the equivalent gain variance (excess noise) is between 1.001 and 1.007 at a gain of 1 x 10(exp 6). With these advantages, the device holds promise to function as a PMT-like photon counter at a 1,550- nm wavelength. The epitaxial layer structure of the device allows photons to be absorbed in the InGaAs layer, generating electron/hole (e-h) pairs. Driven by an electrical field in InGaAs, electrons are collected at the anode while holes reach the multiplication region (InAlAs p-i-n structure) and trigger the avalanche process. As a result, a large number of e-h pairs are created, and the holes move toward the cathode. Holes created by the avalanche process gain large kinetic energy through the electric field, and are considered hot. These hot holes are cooled as they travel across a p -InAlAs low field region, and are eventually blocked by energy barriers formed by the InGaAsP/ InAlAs heterojunctions. The composition of the InGaAsP alloy was chosen to have an 80 me

  2. A method to quench and recharge avalanche photo diodes for use in high rate situations

    International Nuclear Information System (INIS)

    Regan, T.O.; Fenker, H.C.; Thomas, J.; Oliver, J.

    1992-06-01

    We present a new method of using Avalanche Photo Diodes (APDS) for low level light detection in Geiger mode in high rate situations such as those encountered at the Superconducting Super Collider (SSC). The new technique is readily adaptable to implementation in CMOS VLSI

  3. A micropixel avalanche phototransistor for time of flight measurements

    Energy Technology Data Exchange (ETDEWEB)

    Sadigov, A., E-mail: saazik@yandex.ru [National Nuclear Research Center, Baku (Azerbaijan); Institute of Radiation Problems, Baku (Azerbaijan); Suleymanov, S. [National Nuclear Research Center, Baku (Azerbaijan); Institute of Radiation Problems, Baku (Azerbaijan); Ahmadov, F. [National Nuclear Research Center, Baku (Azerbaijan); Ahmadov, G. [National Nuclear Research Center, Baku (Azerbaijan); Joint Institute for Nuclear Research, Dubna (Russian Federation); Abdullayev, K. [National Aviation Academy, Baku (Azerbaijan); Akberov, R. [National Nuclear Research Center, Baku (Azerbaijan); Institute of Radiation Problems, Baku (Azerbaijan); Heydarov, N. [National Nuclear Research Center, Baku (Azerbaijan); Madatov, R. [Institute of Radiation Problems, Baku (Azerbaijan); Mukhtarov, R. [National Aviation Academy, Baku (Azerbaijan); Nazarov, M.; Valiyev, R. [National Nuclear Research Center, Baku (Azerbaijan)

    2017-02-11

    This paper presents results of studies of the silicon based new micropixel avalanche phototransistor (MAPT). MAPT is a modification of well-known silicon photomultipliers (SiPMs) and differs since each photosensitive pixel of the MAPT operates in Geiger mode and comprises an individual micro-transistor operating in binary mode. This provides a high amplitude single photoelectron signal with significantly shorter rise time. The obtained results are compared with appropriate parameters of known SiPMs. - Highlights: • A new photo detector – micropixel avalanche phototransistor was developed. • MAPT has a matrix of microtransistors with fast output. • In these modules the duration of the leading edge of the signal from the photodetectors are not worse than 50–100 ps.

  4. Pixel multiplexing technique for real-time three-dimensional-imaging laser detection and ranging system using four linear-mode avalanche photodiodes

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Fan; Wang, Yuanqing, E-mail: yqwang@nju.edu.cn; Li, Fenfang [School of Electronic Science and Engineering, Nanjing University, Nanjing 210046 (China)

    2016-03-15

    The avalanche-photodiode-array (APD-array) laser detection and ranging (LADAR) system has been continually developed owing to its superiority of nonscanning, large field of view, high sensitivity, and high precision. However, how to achieve higher-efficient detection and better integration of the LADAR system for real-time three-dimensional (3D) imaging continues to be a problem. In this study, a novel LADAR system using four linear mode APDs (LmAPDs) is developed for high-efficient detection by adopting a modulation and multiplexing technique. Furthermore, an automatic control system for the array LADAR system is proposed and designed by applying the virtual instrumentation technique. The control system aims to achieve four functions: synchronization of laser emission and rotating platform, multi-channel synchronous data acquisition, real-time Ethernet upper monitoring, and real-time signal processing and 3D visualization. The structure and principle of the complete system are described in the paper. The experimental results demonstrate that the LADAR system is capable of achieving real-time 3D imaging on an omnidirectional rotating platform under the control of the virtual instrumentation system. The automatic imaging LADAR system utilized only 4 LmAPDs to achieve 256-pixel-per-frame detection with by employing 64-bit demodulator. Moreover, the lateral resolution is ∼15 cm and range accuracy is ∼4 cm root-mean-square error at a distance of ∼40 m.

  5. State-of-the-art performance of GaAlAs/GaAs avalanche photodiodes

    Science.gov (United States)

    Law, H. D.; Nakano, K.; Tomasetta, L. R.

    1979-01-01

    Ga(0.15)Al(0.85)As/GaAs avalanche photodiodes have been successfully fabricated. The performance of these detectors is characterized by a rise time of less than 35 ps, an external quantum efficiency with an antireflection coating of 95% at 0.53 microns, and a microwave optical gain of 42 dB. The dark current density is in the low range (10 to the minus A/sq cm) at one-half the breakdown voltages, and rises to 0.0001 A/sq cm at 42 dB optical gain.

  6. HgCdTe Avalanche Photodiode Detectors for Airborne and Spaceborne Lidar at Infrared Wavelengths

    Science.gov (United States)

    Sun, Xiaoli; Abshire, James B.; Beck, Jeffrey D.; Mitra, Pradip; Reiff, Kirk; Yang, Guangning

    2017-01-01

    We report results from characterizing the HgCdTe avalanche photodiode (APD) sensorchip assemblies (SCA) developed for lidar at infrared wavelength using the high density vertically integrated photodiodes (HDVIP) technique. These devices demonstrated high quantum efficiency, typically greater than 90 between 0.8 micrometers and the cut-off wavelength, greater than 600 APD gain, near unity excess noise factor, 6-10 MHz electrical bandwidth and less than 0.5 fW/Hz(exp.1/2) noise equivalent power (NEP). The detectors provide linear analog output with a dynamic range of 2-3 orders of magnitude at a fixed APD gain without averaging, and over 5 orders of magnitude by adjusting the APD and preamplifier gain settings. They have been successfully used in airborne CO2 and CH4 integrated path differential absorption (IPDA) lidar as a precursor for space lidar applications.

  7. An excess noise measurement system for weak responsivity avalanche photodiodes

    Science.gov (United States)

    Qiao, Liang; Dimler, Simon J.; Baharuddin, Aina N. A. P.; Green, James E.; David, John P. R.

    2018-06-01

    A system for measuring, with reduced photocurrent, the excess noise associated with the gain in avalanche photodiodes (APDs), using a transimpedance amplifier front-end and based on phase-sensitive detection is described. The system can reliably measure the excess noise power of devices, even when the un-multiplied photocurrent is low (~10 nA). This is more than one order of magnitude better than previously reported systems and represents a significantly better noise signal to noise ratio. This improvement in performance has been achieved by increasing the value of the feedback resistor and reducing the op-amp bandwidth. The ability to characterise APD performance with such low photocurrents enables the use of low power light sources such as light emitting diode rather than lasers to investigate the APD noise performance.

  8. New method for determining avalanche breakdown voltage of silicon photomultipliers

    International Nuclear Information System (INIS)

    Chirikov-Zorin, I.

    2017-01-01

    The avalanche breakdown and Geiger mode of the silicon p-n junction is considered. A precise physically motivated method is proposed for determining the avalanche breakdown voltage of silicon photomultipliers (SiPM). The method is based on measuring the dependence of the relative photon detection efficiency (PDE rel ) on the bias voltage when one type of carriers (electron or hole) is injected into the avalanche multiplication zone of the p-n junction. The injection of electrons or holes from the base region of the SiPM semiconductor structure is performed using short-wave or long-wave light. At a low overvoltage (1-2 V) the detection efficiency is linearly dependent on the bias voltage; therefore, extrapolation to zero PDE rel value determines the SiPM avalanche breakdown voltage with an accuracy within a few millivolts. [ru

  9. Silicon Photo-Multiplier Radiation Hardness Tests with a White Neutron Beam

    International Nuclear Information System (INIS)

    Montanari, A.; Tosi, N.; Pietropaolo, A.; Andreotti, M.; Baldini, W.; Calabrese, R.; Cibinetto, G.; Luppi, E.; Cotta Ramusino, A.; Malaguti, R.; Santoro, V.; Tellarini, G.; Tomassetti, L.; De Donato, C.; Reali, E.

    2013-06-01

    We report radiation hardness tests performed, with a white neutron beam, at the Geel Electron Linear Accelerator in Belgium on silicon Photo-Multipliers. These are semiconductor photon detectors made of a square matrix of Geiger-Mode Avalanche photo-diodes on a silicon substrate. Several samples from different manufacturers have been irradiated integrating up to about 6.2 x 10 9 1-MeV-equivalent neutrons per cm 2 . (authors)

  10. Studies of the LHC detection systems: scintillating fibers projective electromagnetic calorimeter prototype and light reading by avalanche photodiodes

    International Nuclear Information System (INIS)

    Bouhemaid, N.

    1995-01-01

    In this thesis a study concerning the hardware detection system of ATLAS experiment in preparation for L.H.C. is presented. The study is divided in two parts. After a general introduction of the L.H.C. and the ATLAS detector, the first part concerning the electromagnetic calorimeter, and the second part concerning the readout with avalanche photodiodes, are discussed. For both subjects the basic principles are presented before various test results are described. Within the RD1 program three different electromagnetic calorimeter prototypes, which all use the lead scintillating fibres technique, have been built. The first is a non-projective, compensating calorimeter called ''500μm'', the second is a pseudo projective, non-compensating, called ''1 mm'', and the third is fully projective, called ''Radial''. The last prototype is discussed in more detail. Avalanches photodiodes which are used as readout of the ''1 mm'' calorimeter, have been exposed to both, a dedicated test bench in the laboratory as well as to test beams. The results of these tests are also presented. (author). 35 refs., 96 figs., 30 tabs

  11. X-ray fluorescence hologram data collection with a cooled avalanche photodiode

    CERN Document Server

    Hayashi, K; Matsubara, E I; Kishimoto, S; Mori, T; Tanaka, M

    2002-01-01

    A high counting rate X-ray detector with an appropriate energy resolution is desired for high quality X-ray fluorescence hologram measurements because a holographic pattern is detected as extremely small intensity variations of X-ray fluorescence on a large intensity background. A cooled avalanche photodiode (APD), which has about 10% energy resolution and is designed for a high counting rate, fits the above requirements. Reconstructed atomic images from experimental holograms using the APD system provide us a clear view of the first and second neighbor atoms around an emitter. The present result proved that a combination of this APD system and a synchrotron X-ray source enables us to measure a high quality hologram for a reasonable measurement time.

  12. Application of avalanche photodiodes for the measurement of actinides by alpha liquid scintillation counting

    International Nuclear Information System (INIS)

    Reboli, A.

    2005-10-01

    Alpha emitters analysis using liquid scintillation spectroscopy is often used when sensitivity and fast samples preparation are the important points. A more extensive use of this technique is until now limited by its poor resolution compared to alpha particle spectroscopy with semiconductor detectors. To improve the resolution and thus promote this method for the measurement of actinides in environment, we have tested silicon avalanche photodiodes (APD) as new detectors for scintillation photons. The set-up consists of a large area avalanche photodiode (16 mm diameter) coupled to a thin vial containing alpha-emitters within a liquid scintillation cocktail. After optimization of several parameters like bias voltage, temperature, counting geometry and composition of the scintillating cocktail, energy resolutions have been found to be better than those obtained with standard photomultiplier tubes (PMT): 5% (200 keV FWHM) for 232 Th and 4.2% (240 keV FWHM) for 236 Pu. Our results show that the improvement is due to less fluctuations associated with light collection since the spatial response of APDs is more uniform than that of PMTs. The expected gain on quantum efficiency (80% for APDs instead of 25% for PMTs) is nullified by a corresponding increase on electronic noise and excess noise factor. Significant better results are foreseen by using green scintillators (450 - 550 nm wavelengths region) with larger Stokes-shift and blue-enhanced APDs which reach their maximum quantum efficiency in this region. (author)

  13. Best-Practice Criteria for Practical Security of Self-Differencing Avalanche Photodiode Detectors in Quantum Key Distribution

    Science.gov (United States)

    Koehler-Sidki, A.; Dynes, J. F.; Lucamarini, M.; Roberts, G. L.; Sharpe, A. W.; Yuan, Z. L.; Shields, A. J.

    2018-04-01

    Fast-gated avalanche photodiodes (APDs) are the most commonly used single photon detectors for high-bit-rate quantum key distribution (QKD). Their robustness against external attacks is crucial to the overall security of a QKD system, or even an entire QKD network. We investigate the behavior of a gigahertz-gated, self-differencing (In,Ga)As APD under strong illumination, a tactic Eve often uses to bring detectors under her control. Our experiment and modeling reveal that the negative feedback by the photocurrent safeguards the detector from being blinded through reducing its avalanche probability and/or strengthening the capacitive response. Based on this finding, we propose a set of best-practice criteria for designing and operating fast-gated APD detectors to ensure their practical security in QKD.

  14. Progress in low light-level InAs detectors- towards Geiger-mode detection

    Science.gov (United States)

    Tan, Chee Hing; Ng, Jo Shien; Zhou, Xinxin; David, John; Zhang, Shiyong; Krysa, Andrey

    2017-05-01

    InAs avalanche photodiodes (APDs) can be designed such that only electrons are allowed to initiate impact ionization, leading to the lowest possible excess noise factor. Optimization of wet chemical etching and surface passivation produced mesa APDs with bulk dominated dark current and responsivity that are comparable and higher, respectively, than a commercial InAs detector. Our InAs electron-APDs also show high stability with fluctuation of 0.1% when operated at a gain of 11.2 over 60 s. These InAs APDs can detect very weak signal down to 35 photons per pulse. Fabrication of planar InAs by Be implantation produced planar APDs with bulk dominated dark current. Annealing at 550 °C was necessary to remove implantation damage and to activate Be dopants. Due to minimal diffusion of Be, thick depletion of 8 μm was achieved. Since the avalanche gain increases exponentially with the thickness of avalanche region, our planar APD achieved high gain > 300 at 200 K. Our work suggest that both mesa and planar InAs APDs can exhibit high gain. When combined with a suitable preamplifier, single photon detection using InAs electron-APDs could be achieved.

  15. Measurement-based characterization of multipixel avalanche photodiodes for scintillating detectors

    CERN Document Server

    Dziewiecki, M

    2012-01-01

    Multipixel avalanche photodiodes (MAPD) are recently gaining popularity in high energy physics experiments as an attractive replacement for photomultiplier tubes, which have been extensively used for many years as a part of various scintillating detectors. Their low price, small dimensions and another features facilitating their use (like mechanical shock resistance, magnetic field immunity or moderate supply voltage) make the MAPDs a good choice for commercial use as well, what is reflected in growing number of producers as well as MAPD models available on the market. This dissertation presents Author’s experience with MAPD measurements and modelling, gained during his work on the T2K (Tokai-to-Kamioka) long-baseline neutrino experiment, carried out by an international collaboration in Japan. First, operation principle of the MAPD, definitions of various parameters and measurement methods are discussed. Then, a device for large-scale MAPD measurements and related data processing methods are described. Fina...

  16. A transimpedance amplifier for excess noise measurements of high junction capacitance avalanche photodiodes

    International Nuclear Information System (INIS)

    Green, James E; David, John P R; Tozer, Richard C

    2012-01-01

    This paper reports a novel and versatile system for measuring excess noise and multiplication in avalanche photodiodes (APDs), using a bipolar junction transistor based transimpedance amplifier front-end and based on phase-sensitive detection, which permits accurate measurement in the presence of a high dark current. The system can reliably measure the excess noise factor of devices with capacitance up to 5 nF. This system has been used to measure thin, large area Si pin APDs and the resulting data are in good agreement with measurements of the same devices obtained from a different noise measurement system which will be reported separately. (paper)

  17. Application of avalanche photodiode for soft X-ray pulse-height analyses in the Ht-7 tokamak

    CERN Document Server

    Shi Yue Jiang; Hu Li Qun; Sun Yan Jun; LiuSheng; Ling Bil

    2002-01-01

    An avalanche photodiode (APD) has been used as soft X-ray energy pulse-height analysis system for the measurement of the electron temperature on the HT-7 tokamak. The experimental results obtained with the APD with its inferior energy resolution show a little difference compared to the conventional high energy-resolution Si (Li) detector. Both numerical analysis and experimental results prove that the APD is good enough for application of the electron temperature measurement in tokamaks.

  18. Radiation hardness investigation of avalanche photodiodes for the Projectile Spectator Detector readout at the Compressed Baryonic Matter experiment

    Czech Academy of Sciences Publication Activity Database

    Kushpil, Vasilij; Mikhaylov, Vasily; Kushpil, Svetlana; Tlustý, Pavel; Svoboda, Ondřej; Kugler, Andrej

    2015-01-01

    Roč. 787, JUL (2015), s. 117-120 ISSN 0168-9002 R&D Projects: GA MŠk LG12007; GA MŠk LG14004; GA MŠk(CZ) LM2011019 Institutional support: RVO:61389005 Keywords : avalanche photodiodes * single protons detection * radiation hardness * neutron irradiation tests * compressed Baryonic Matter experiment * Projectile Spectator Detector Subject RIV: BG - Nuclear, Atomic and Molecular Physics , Colliders Impact factor: 1.200, year: 2015

  19. Studies of the LHC detection systems: scintillating fibers projective electromagnetic calorimeter prototype and light reading by avalanche photodiodes; Etudes de systemes de detection pour LHC: prototype d`un calorimetre electromagnetique projectif a fibres scintillantes et lecture de la lumiere par des photodiodes a avalanches

    Energy Technology Data Exchange (ETDEWEB)

    Bouhemaid, N

    1995-09-22

    In this thesis a study concerning the hardware detection system of ATLAS experiment in preparation for L.H.C. is presented. The study is divided in two parts. After a general introduction of the L.H.C. and the ATLAS detector, the first part concerning the electromagnetic calorimeter, and the second part concerning the readout with avalanche photodiodes, are discussed. For both subjects the basic principles are presented before various test results are described. Within the RD1 program three different electromagnetic calorimeter prototypes, which all use the lead scintillating fibres technique, have been built. The first is a non-projective, compensating calorimeter called ``500{mu}m``, the second is a pseudo projective, non-compensating, called ``1 mm``, and the third is fully projective, called ``Radial``. The last prototype is discussed in more detail. Avalanches photodiodes which are used as readout of the ``1 mm`` calorimeter, have been exposed to both, a dedicated test bench in the laboratory as well as to test beams. The results of these tests are also presented. (author). 35 refs., 96 figs., 30 tabs.

  20. Readout of plastic scintillators with cooled large-area avalanche photodiodes

    Energy Technology Data Exchange (ETDEWEB)

    Mykulyak, A.; Kapusta, M.; Lynen, U.; Moszynski, M.; Mueller, W.F.J.; Orth, H.; Schwarz, C.; Szawlowski, M.; Trautmann, W.; Trzcinski, A.; Wolski, D.; Zwieglinski, B. E-mail: bzw@fuw.edu.pl

    2004-05-11

    Time-of-flight measurements in multifragmentation of heavy, relativistic projectiles require very good time resolution and at the same time the detecting system must cope with a dynamic range of up to 8000:1. We look into the possibility of application of large-area avalanche photodiodes (LAAPDs) as alternative light sensors to meet the above requirements. The paper presents the results of our amplitude and time response studies of a plastic scintillator BC-408 readout with a phi16 mm LAAPD using radioactive sources. The measurements were performed using two different setups. The best time resolution has been obtained by exploiting LAAPD cooling to increase its gain beyond that accessible at room temperature. We reach 610 ps (FWHM) at -26 deg. C for the corresponding LAAPD gain of {approx}900 and the {sup 90}Sr/{sup 90}Y {beta}-ray source. We hope to reach below the desired 400 ps with the latter setup at the higher light levels available with multifragmentation products.

  1. Investigation of silicon/silicon germanium multiple quantum well layers in silicon avalanche photodiodes

    International Nuclear Information System (INIS)

    Loudon, A.Y.

    2002-01-01

    Silicon single photon avalanche diodes (SPADs) are currently utilised in many single photon counting systems due to their high efficiency, fast response times, low voltage operation and potentially low cost. For fibre based applications however (at wavelengths 1.3 and 1.55μm) and eye-safe wavelength applications (>1.4μm), Si devices are not suitable due to their 1.1μm absorption edge and hence greatly reduced absorption above this wavelength. InGaAs/InP or Ge SPADs absorb at these longer wavelengths, but both require cryogenic cooling for low noise operation and III-V integration with conventional Si circuitry is difficult. Si/SiGe is currently attracting great interest for optoelectronic applications and attempts to combine Si avalanche photodiodes with Si/SiGe multiple quantum well absorbing layers have been successful. Here, an effort to utilise this material system has shown an improvement in photon counting efficiency above 1.1μm of more than 30 times compared to an all-Si control device. In addition to its longer wavelength response, this Si/SiGe device has room temperature operation, low cost fabrication and is compatible with conventional Si circuitry. (author)

  2. Laser annealing heals radiation damage in avalanche photodiodes

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Jin Gyu [University of Waterloo, Institute for Quantum Computing, Waterloo, ON (Canada); University of Waterloo, Department of Electrical and Computer Engineering, Waterloo, ON (Canada); Anisimova, Elena; Higgins, Brendon L.; Bourgoin, Jean-Philippe [University of Waterloo, Institute for Quantum Computing, Waterloo, ON (Canada); University of Waterloo, Department of Physics and Astronomy, Waterloo, ON (Canada); Jennewein, Thomas [University of Waterloo, Institute for Quantum Computing, Waterloo, ON (Canada); University of Waterloo, Department of Physics and Astronomy, Waterloo, ON (Canada); Canadian Institute for Advanced Research, Quantum Information Science Program, Toronto, ON (Canada); Makarov, Vadim [University of Waterloo, Institute for Quantum Computing, Waterloo, ON (Canada); University of Waterloo, Department of Electrical and Computer Engineering, Waterloo, ON (Canada); University of Waterloo, Department of Physics and Astronomy, Waterloo, ON (Canada)

    2017-12-15

    Avalanche photodiodes (APDs) are a practical option for space-based quantum communications requiring single-photon detection. However, radiation damage to APDs significantly increases their dark count rates and thus reduces their useful lifetimes in orbit. We show that high-power laser annealing of irradiated APDs of three different models (Excelitas C30902SH, Excelitas SLiK, and Laser Components SAP500S2) heals the radiation damage and several APDs are restored to typical pre-radiation dark count rates. Of nine samples we test, six APDs were thermally annealed in a previous experiment as another solution to mitigate the radiation damage. Laser annealing reduces the dark count rates further in all samples with the maximum dark count rate reduction factor varying between 5.3 and 758 when operating at -80 C. This indicates that laser annealing is a more effective method than thermal annealing. The illumination power to reach these reduction factors ranges from 0.8 to 1.6 W. Other photon detection characteristics, such as photon detection efficiency, timing jitter, and afterpulsing probability, fluctuate but the overall performance of quantum communications should be largely unaffected by these variations. These results herald a promising method to extend the lifetime of a quantum satellite equipped with APDs. (orig.)

  3. Origin of large dark current increase in InGaAs/InP avalanche photodiode

    Science.gov (United States)

    Wen, J.; Wang, W. J.; Chen, X. R.; Li, N.; Chen, X. S.; Lu, W.

    2018-04-01

    The large dark current increase near the breakdown voltage of an InGaAs/InP avalanche photodiode is observed and analyzed from the aspect of bulk defects in the device materials. The trap level information is extracted from the temperature-dependent electrical characteristics of the device and the low temperature photoluminescence spectrum of the materials. Simulation results with the extracted trap level taken into consideration show that the trap is in the InP multiplication layer and the trap assisted tunneling current induced by the trap is the main cause of the large dark current increase with the bias from the punch-through voltage to 95% breakdown voltage.

  4. Post-processing Free Quantum Random Number Generator Based on Avalanche Photodiode Array

    International Nuclear Information System (INIS)

    Li Yang; Liao Sheng-Kai; Liang Fu-Tian; Shen Qi; Liang Hao; Peng Cheng-Zhi

    2016-01-01

    Quantum random number generators adopting single photon detection have been restricted due to the non-negligible dead time of avalanche photodiodes (APDs). We propose a new approach based on an APD array to improve the generation rate of random numbers significantly. This method compares the detectors' responses to consecutive optical pulses and generates the random sequence. We implement a demonstration experiment to show its simplicity, compactness and scalability. The generated numbers are proved to be unbiased, post-processing free, ready to use, and their randomness is verified by using the national institute of standard technology statistical test suite. The random bit generation efficiency is as high as 32.8% and the potential generation rate adopting the 32 × 32 APD array is up to tens of Gbits/s. (paper)

  5. Large area avalanche photodiodes in scintillation and X-rays detection

    CERN Document Server

    Moszynski, M; Kapusta, M; Balcerzyk, M

    2002-01-01

    The presented paper summarizes our earlier studies on application of beveled-edge Large Area Avalanche Photodiodes (LAAPDs) in gamma-rays scintillation detection. LAAPDs, due to their high quantum efficiency and low excess noise factor allow for better statistical accuracy of the signal as compared to photomultipliers. The device dark noise contribution significantly affects energy resolution only for gamma-rays with energy below 50 keV. Notably better or comparable energy resolutions to those observed with a XP2020Q photomultiplier were obtained with the LAAPDs for a number of different scintillators. Particularly, the recorded energy resolutions of 4.3+-0.2% and 4.8+-0.14% measured with YAP and CsI(Tl) crystals, respectively, for the 662 keV gamma-peak from a sup 1 sup 3 sup 7 Cs source belong to the best observed ever with these scintillation detectors. Results of the study of timing with fast scintillators coupled to the LAAPD showed subnanosecond time resolution of 570+-30 ps for sup 6 sup 0 Co gamma-ray...

  6. Radiation Detection Measurements with a New 'Buried Junction' Silicon Avalanche Photodiode

    CERN Document Server

    Lecomte, R; Rouleau, D; Dautet, H; McIntyre, R J; McSween, D; Webb, P

    1999-01-01

    An improved version of a recently developed 'Buried Junction' avalanche photodiode (APD), designed for use with scintillators, is described and characterized. This device, also called the 'Reverse APD', is designed to have a wide depletion layer and thus low capacitance, but to have high gain only for e-h pairs generated within the first few microns of the depletion layer. Thus it has high gain for light from scintillators emitting in the 400-600 nm range, with relatively low dark current noise and it is relatively insensitive to minimum ionizing particles (MIPs). An additional feature is that the metallurgical junction is at the back of the wafer, leaving the front surface free to be coupled to a scintillator without fear of junction contamination. The modifications made in this device, as compared with the earlier diode, have resulted in a lower excess noise factor, lower dark current, and much-reduced trapping. The electrical and optical characteristics of this device are described and measurements of ener...

  7. CMOS-based avalanche photodiodes for direct particle detection

    International Nuclear Information System (INIS)

    Stapels, Christopher J.; Squillante, Michael R.; Lawrence, William G.; Augustine, Frank L.; Christian, James F.

    2007-01-01

    Active Pixel Sensors (APSs) in complementary metal-oxide-semiconductor (CMOS) technology are augmenting Charge-Coupled Devices (CCDs) as imaging devices and cameras in some demanding optical imaging applications. Radiation Monitoring Devices are investigating the APS concept for nuclear detection applications and has successfully migrated avalanche photodiode (APD) pixel fabrication to a CMOS environment, creating pixel detectors that can be operated with internal gain as proportional detectors. Amplification of the signal within the diode allows identification of events previously hidden within the readout noise of the electronics. Such devices can be used to read out a scintillation crystal, as in SPECT or PET, and as direct-conversion particle detectors. The charge produced by an ionizing particle in the epitaxial layer is collected by an electric field within the diode in each pixel. The monolithic integration of the readout circuitry with the pixel sensors represents an improved design compared to the current hybrid-detector technology that requires wire or bump bonding. In this work, we investigate designs for CMOS APD detector elements and compare these to typical values for large area devices. We characterize the achievable detector gain and the gain uniformity over the active area. The excess noise in two different pixel structures is compared. The CMOS APD performance is demonstrated by measuring the energy spectra of X-rays from 55 Fe

  8. Avalanche and streamer mode operation of resistive plate chambers

    International Nuclear Information System (INIS)

    Cardarelli, R.; Makeev, V.; Santonico, R.

    1996-01-01

    A resistive plate chamber was operated at voltages increasing in steps of 200 V over a 3 kV interval and the transition between the avalanche and streamer modes was studied. The avalanche amplitude was observed to be exponentially dependent on the operating voltage up to a value, characteristic of the gas, where the avalanche saturation occurs and delayed streamer signals start to appear. Signal waveforms, charge and timing distributions are reported. (orig.)

  9. Predictions of silicon avalanche photodiode detector performance in water vapor differential absorption lidar

    Science.gov (United States)

    Kenimer, R. L.

    1988-01-01

    Performance analyses are presented which establish that over most of the range of signals expected for a down-looking differential absorption lidar (DIAL) operated at 16 km the silicon avalanche photodiode (APD) is the preferred detector for DIAL measurements of atmospheric water vapor in the 730 nm spectral region. The higher quantum efficiency of the APD's, (0.8-0.9) compared to a photomultiplier's (0.04-0.18) more than offsets the higher noise of an APD receiver. In addition to offering lower noise and hence lower random error the APD's excellent linearity and impulse recovery minimize DIAL systematic errors attributable to the detector. Estimates of the effect of detector system parameters on overall random and systematic DIAL errors are presented, and performance predictions are supported by laboratory characterization data for an APD receiver system.

  10. Evaluation of a fast single-photon avalanche photodiode for measurement of early transmitted photons through diffusive media.

    Science.gov (United States)

    Mu, Ying; Valim, Niksa; Niedre, Mark

    2013-06-15

    We tested the performance of a fast single-photon avalanche photodiode (SPAD) in measurement of early transmitted photons through diffusive media. In combination with a femtosecond titanium:sapphire laser, the overall instrument temporal response time was 59 ps. Using two experimental models, we showed that the SPAD allowed measurement of photon-density sensitivity functions that were approximately 65% narrower than the ungated continuous wave case at very early times. This exceeds the performance that we have previously achieved with photomultiplier-tube-based systems and approaches the theoretical maximum predicted by time-resolved Monte Carlo simulations.

  11. Large area avalanche photodiodes in scintillation and X-rays detection

    International Nuclear Information System (INIS)

    Moszynski, M.; Szawlowski, M.; Kapusta, M.; Balcerzyk, M.

    2002-01-01

    The presented paper summarizes our earlier studies on application of beveled-edge Large Area Avalanche Photodiodes (LAAPDs) in γ-rays scintillation detection. LAAPDs, due to their high quantum efficiency and low excess noise factor allow for better statistical accuracy of the signal as compared to photomultipliers. The device dark noise contribution significantly affects energy resolution only for γ-rays with energy below 50 keV. Notably better or comparable energy resolutions to those observed with a XP2020Q photomultiplier were obtained with the LAAPDs for a number of different scintillators. Particularly, the recorded energy resolutions of 4.3±0.2% and 4.8±0.14% measured with YAP and CsI(Tl) crystals, respectively, for the 662 keV γ-peak from a 137 Cs source belong to the best observed ever with these scintillation detectors. Results of the study of timing with fast scintillators coupled to the LAAPD showed subnanosecond time resolution of 570±30 ps for 60 Co γ-rays detected in LSO crystal. The response of LAAPD to X-rays and factors limiting energy resolution have been discussed too

  12. Progress in the use of avalanche photodiodes for readout for calorimeters

    International Nuclear Information System (INIS)

    Fenker, H.; Morgan, K.; Regan, T.

    1991-09-01

    During the past year the Superconducting Super Collider Tracking Group has progressed from acquisition of its first avalanche photodiode (APD) to installation of a 96-channel array of the devices. The work was motivated by the desire to learn how to use APDs as the sensitive elements in a fiber tracking detector, moderated by the presence of limited resources and the absence of activity within groups outside the SSC Laboratory on such a project. We chose, therefore, to team up with an ongoing research effort which intended to evaluate both pre-shower and shower-maximum detectors and various means of sensing the light produced. The pre-shower detector is made of layers of scintillating fibers similar to a fiber tracker. The shower-maximum detector uses optical fibers to transmit the light from scintillating plates to the readout devices. Our contribution has been to develop the APD array for use in this test from concept to operation. Currently, the equipment is installed in Fermilab's MP beamline awaiting delivery to the final 36 APDs and exposure to the beam. 9 refs., 18 figs

  13. A silicon avalanche photodiode detector circuit for Nd:YAG laser scattering

    International Nuclear Information System (INIS)

    Hsieh, C.L.; Haskovec, J.; Carlstrom, T.N.; DeBoo, J.C.; Greenfield, C.M.; Snider, R.T.; Trost, P.

    1990-06-01

    A silicon avalanche photodiode with an internal gain of about 50 to 100 is used in a temperature controlled environment to measure the Nd:YAG laser Thomson scattered spectrum in the wavelength range from 700 to 1150 nm. A charge sensitive preamplifier has been developed for minimizing the noise contribution from the detector electronics. Signal levels as low as 20 photoelectrons (S/N = 1) can be detected. Measurements show that both the signal and the variance of the signal vary linearly with the input light level over the range of interest, indicating Poisson statistics. The signal is processed using a 100 ns delay line and a differential amplifier which subtracts the low frequency background light component. The background signal is amplified with a computer controlled variable gain amplifier and is used for an estimate of the measurement error, calibration, and Z eff measurements of the plasma. The signal processing has been analyzed using a theoretical model to aid the system design and establish the procedure for data error analysis. 4 refs., 5 figs

  14. HIGH-SPEED IMAGING AND WAVEFRONT SENSING WITH AN INFRARED AVALANCHE PHOTODIODE ARRAY

    Energy Technology Data Exchange (ETDEWEB)

    Baranec, Christoph; Atkinson, Dani; Hall, Donald; Jacobson, Shane; Chun, Mark [Institute for Astronomy, University of Hawai‘i at Mānoa, Hilo, HI 96720-2700 (United States); Riddle, Reed [Division of Physics, Mathematics, and Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States); Law, Nicholas M., E-mail: baranec@hawaii.edu [Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3255 (United States)

    2015-08-10

    Infrared avalanche photodiode (APD) arrays represent a panacea for many branches of astronomy by enabling extremely low-noise, high-speed, and even photon-counting measurements at near-infrared wavelengths. We recently demonstrated the use of an early engineering-grade infrared APD array that achieves a correlated double sampling read noise of 0.73 e{sup −} in the lab, and a total noise of 2.52 e{sup −} on sky, and supports simultaneous high-speed imaging and tip-tilt wavefront sensing with the Robo-AO visible-light laser adaptive optics (AO) system at the Palomar Observatory 1.5 m telescope. Here we report on the improved image quality simultaneously achieved at visible and infrared wavelengths by using the array as part of an image stabilization control loop with AO-sharpened guide stars. We also discuss a newly enabled survey of nearby late M-dwarf multiplicity, as well as future uses of this technology in other AO and high-contrast imaging applications.

  15. Study of an avalanche-mode resistive plate chamber

    International Nuclear Information System (INIS)

    Ying, J.; Ban, Y.; Liu, H.T.; Zhu, Z.M.; Zhu, Z.Y.; Chen, T.; Ma, J.G.; Ye, Y.L.

    2000-01-01

    Resistive plate chambers (RPCs) are widely used to detect high-energy charged particles, especially muons, due to the high gain, moderate time and spatial resolution, simple design and low cost of these detectors. While the simple streamer mode is adequate for cosmic-ray and low-rate accelerator experiments, the avalanche mode is required for high-rate experiments such as CMS at LHC. In this paper construction of a medium-sized double-gap RPC made of Chinese materials is reported. The experimental set-up of cosmic-ray and muon beam tests are introduced. The avalanche mode was clearly observed. Good efficiency and time resolution were obtained from the beam test at CERN under normal irradiation conditions. At very high radiation background the chamber efficiency decreases, indicating the necessity to change the resistivity value of the Chinese bakelites. (author)

  16. Application of Geiger-mode photosensors in Cherenkov detectors

    Energy Technology Data Exchange (ETDEWEB)

    Gamal, Ahmed, E-mail: gamal.ahmed@assoc.oeaw.ac.a [Stefan Meyer Institute for Subatomic Physics of the Austrian Academy of Sciences, Vienna (Austria); Al-Azhar University, Faculty of Science, Physics Department, Cairo (Egypt); Paul, Buehler; Michael, Cargnelli [Stefan Meyer Institute for Subatomic Physics of the Austrian Academy of Sciences, Vienna (Austria); Roland, Hohler [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, Darmstadt (Germany); Johann, Marton [Stefan Meyer Institute for Subatomic Physics of the Austrian Academy of Sciences, Vienna (Austria); Herbert, Orth [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, Darmstadt (Germany); Ken, Suzuki [Stefan Meyer Institute for Subatomic Physics of the Austrian Academy of Sciences, Vienna (Austria)

    2011-05-21

    Silicon-based photosensors (SiPMs) working in the Geiger-mode represent an elegant solution for the readout of particle detectors working at low-light levels like Cherenkov detectors. Especially the insensitivity to magnetic fields makes this kind of sensors suitable for modern detector systems in subatomic physics which are usually employing magnets for momentum resolution. We are characterizing SiPMs of different manufacturers for selecting sensors and finding optimum operating conditions for given applications. Recently we designed and built a light concentrator prototype with 8x8 cells to increase the active photon detection area of an 8x8 SiPM (Hamamatsu MPPC S10931-100P) array. Monte Carlo studies, measurements of the collection efficiency, and tests with the MPPC were carried out. The status of these developments are presented.

  17. A G-APD based Camera for Imaging Atmospheric Cherenkov Telescopes

    International Nuclear Information System (INIS)

    Anderhub, H.; Backes, M.; Biland, A.; Boller, A.; Braun, I.; Bretz, T.; Commichau, S.; Commichau, V.; Dorner, D.; Gendotti, A.; Grimm, O.; Gunten, H. von; Hildebrand, D.; Horisberger, U.; Koehne, J.-H.; Kraehenbuehl, T.; Kranich, D.; Lorenz, E.; Lustermann, W.; Mannheim, K.

    2011-01-01

    Imaging Atmospheric Cherenkov Telescopes (IACT) for Gamma-ray astronomy are presently using photomultiplier tubes as photo sensors. Geiger-mode avalanche photodiodes (G-APD) promise an improvement in sensitivity and, important for this application, ease of construction, operation and ruggedness. G-APDs have proven many of their features in the laboratory, but a qualified assessment of their performance in an IACT camera is best undertaken with a prototype. This paper describes the design and construction of a full-scale camera based on G-APDs realized within the FACT project (First G-APD Cherenkov Telescope).

  18. Single ion implantation for single donor devices using Geiger mode detectors

    International Nuclear Information System (INIS)

    Bielejec, E; Seamons, J A; Carroll, M S

    2010-01-01

    Electronic devices that are designed to use the properties of single atoms such as donors or defects have become a reality with recent demonstrations of donor spectroscopy, single photon emission sources, and magnetic imaging using defect centers in diamond. Ion implantation, an industry standard for atom placement in materials, requires augmentation for single ion capability including a method for detecting a single ion arrival. Integrating single ion detection techniques with the single donor device construction region allows single ion arrival to be assured. Improving detector sensitivity is linked to improving control over the straggle of the ion as well as providing more flexibility in lay-out integration with the active region of the single donor device construction zone by allowing ion sensing at potentially greater distances. Using a remotely located passively gated single ion Geiger mode avalanche diode (SIGMA) detector we have demonstrated 100% detection efficiency at a distance of >75 μm from the center of the collecting junction. This detection efficiency is achieved with sensitivity to ∼600 or fewer electron-hole pairs produced by the implanted ion. Ion detectors with this sensitivity and integrated with a thin dielectric, for example a 5 nm gate oxide, using low energy Sb implantation would have an end of range straggle of -1 and 10 -4 for operation temperatures of ∼300 K and ∼77 K, respectively. Low temperature operation and reduced false, 'dark', counts are critical to achieving high confidence in single ion arrival. For the device performance in this work, the confidence is calculated as a probability of >98% for counting one and only one ion for a false count probability of 10 -4 at an average ion number per gated window of 0.015.

  19. New Very Low Noise Multilayer And Graded-Gap Avalanche Photodiodes For The 0.8 To 1 .8 μm Wavelength Region

    Science.gov (United States)

    Capasso, F.; Tsang, W. T.; Williams, G. F.

    1982-12-01

    Recent experimental and theoretical results on a new class of low noise avalanche photo-diodes are reviewed. A large enhancement of the impact ionization rates ratio (a/(3=10) has been demonstrated in AlGaAs/GaAs superlattices and graded band gap detector structures. In addition two novel photodiodes ("staircase" and "channeling" APDs) where only electrons multiply, have been proposed. The staircase APD is the solid state analog of the photo-multiplier with discrete dynodes. It has a low operating voltage (5-20 volts) and a lower excess noise factor, in the ideal case, than that of an ideal conventional APD The channeling APD is instead the solid state analog of a channeltron photomultiplier and has the unique feature of an ultrahigh a/β, ratio (≍∞) compatible with high gain (>100).

  20. Gas sampling calorimeter studies in proportional, saturated avalanche, and streamer modes

    International Nuclear Information System (INIS)

    Atac, M.; Bedeschi, F.; Yoh, J.; Morse, R.; Procario, M.

    1982-01-01

    Recently, satisfactory new results were obtained at SLAC from gas sampling calorimeters running in the saturated avalanche mode within the energy range of 1.5 to 17.5 GeV. To study the higher energy behavior of this mode, more tests were carried out in the M4 beamline at Fermilab. This paper contains results obtained from the MAC prototype electromagnetic and hadronic calorimeters running in the proportional, saturated avalanche, and the streamer regions for energies between 12 and 150 GeV

  1. Low power wide spectrum optical transmitter using avalanche mode LEDs in SOI CMOS technology

    NARCIS (Netherlands)

    Agarwal, V.; Dutta, S; Annema, AJ; Hueting, RJE; Steeneken, P.G.; Nauta, B

    2017-01-01

    This paper presents a low power monolithically integrated optical transmitter with avalanche mode light emitting diodes in a 140 nm silicon-on-insulator CMOS technology. Avalanche mode LEDs in silicon exhibit wide-spectrum electroluminescence (400 nm < λ < 850 nm), which has a significant

  2. Development of analog solid-state photo-detectors for Positron Emission Tomography

    International Nuclear Information System (INIS)

    Bisogni, Maria Giuseppina; Morrocchi, Matteo

    2016-01-01

    Solid-state photo-detectors are one of the main innovations of past century in the field of sensors. First produced in the early forties with the invention of the p–n junction in silicon and the study of its optical properties, photo-detectors received a major boost in the sixties when the p-i-n (PIN) photodiode was developed and successfully used in several applications. The development of devices with internal gain, avalanche photodiodes (APD) first and then Geiger-mode avalanche photodiodes, named single photon avalanche diode (SPAD), leads to a substantial improvement in sensitivity and allowed single photon detection. Later on, thousands of SPADs have been assembled in arrays of few millimeters squared (named SiPM, silicon photo-multiplier) with single photon resolution. The high internal gain of SiPMs, together with other features peculiar of the silicon technology like compactness, speed and compatibility with magnetic fields, promoted SiPMs as the principal photo-detector competitor of photomultipliers in many applications from radiation detection to medical imaging. This paper provides a review of the properties of analog solid-state photo-detectors. Particular emphasis is given to latest advances on Positron Emission Tomography instrumentation boosted by the adoption of the silicon photo-detectors as an alternative to photomultiplier tubes (PMTs). Special attention is dedicated to the SiPMs, which are playing a key role in the development of innovative scanners.

  3. Development of analog solid-state photo-detectors for Positron Emission Tomography

    Energy Technology Data Exchange (ETDEWEB)

    Bisogni, Maria Giuseppina, E-mail: giuseppina.bisogni@pi.infn.it; Morrocchi, Matteo

    2016-02-11

    Solid-state photo-detectors are one of the main innovations of past century in the field of sensors. First produced in the early forties with the invention of the p–n junction in silicon and the study of its optical properties, photo-detectors received a major boost in the sixties when the p-i-n (PIN) photodiode was developed and successfully used in several applications. The development of devices with internal gain, avalanche photodiodes (APD) first and then Geiger-mode avalanche photodiodes, named single photon avalanche diode (SPAD), leads to a substantial improvement in sensitivity and allowed single photon detection. Later on, thousands of SPADs have been assembled in arrays of few millimeters squared (named SiPM, silicon photo-multiplier) with single photon resolution. The high internal gain of SiPMs, together with other features peculiar of the silicon technology like compactness, speed and compatibility with magnetic fields, promoted SiPMs as the principal photo-detector competitor of photomultipliers in many applications from radiation detection to medical imaging. This paper provides a review of the properties of analog solid-state photo-detectors. Particular emphasis is given to latest advances on Positron Emission Tomography instrumentation boosted by the adoption of the silicon photo-detectors as an alternative to photomultiplier tubes (PMTs). Special attention is dedicated to the SiPMs, which are playing a key role in the development of innovative scanners.

  4. Electronics for the camera of the First G-APD Cherenkov Telescope (FACT) for ground based gamma-ray astronomy

    International Nuclear Information System (INIS)

    Anderhub, H; Biland, A; Boller, A; Braun, I; Commichau, V; Djambazov, L; Dorner, D; Gendotti, A; Grimm, O; Gunten, H P von; Hildebrand, D; Horisberger, U; Huber, B; Kim, K-S; Krähenbühl, T; Backes, M; Köhne, J-H; Krumm, B; Bretz, T; Farnier, C

    2012-01-01

    Within the FACT project, we construct a new type of camera based on Geiger-mode avalanche photodiodes (G-APDs). Compared to photomultipliers, G-APDs are more robust, need a lower operation voltage and have the potential of higher photon-detection efficiency and lower cost, but were never fully tested in the harsh environments of Cherenkov telescopes. The FACT camera consists of 1440 G-APD pixels and readout channels, based on the DRS4 (Domino Ring Sampler) analog pipeline chip and commercial Ethernet components. Preamplifiers, trigger system, digitization, slow control and power converters are integrated into the camera.

  5. Study of micro pixel photon counters for a high granularity scintillator-based hadron calorimeter

    International Nuclear Information System (INIS)

    D'Ascenzo, N.; Eggemann, A.; Garutti, E.

    2007-11-01

    A new Geiger mode avalanche photodiode, the Micro Pixel Photon Counter (MPPC), was recently released by Hamamatsu. It has a high photo-detection efficiency in the 420 nm spectral region. This product can represent an elegant candidate for the design of a high granularity scintillator based hadron calorimeter for the International Linear Collider. In fact, the direct readout of the blue scintillation photons with a MPPC is a feasible techological solution. The readout of a plastic scintillator by a MPPC, both mediated by the traditional wavelength shifting fiber, and directly coupled, has been systematically studied. (orig.)

  6. First results of systematic studies done with silicon photomultipliers

    International Nuclear Information System (INIS)

    Bosio, C.; Gentile, S.; Kuznetsova, E.; Meddi, F.

    2008-01-01

    Multicell avalanche photodiode structure operated in Geiger mode usually referred as silicon photomultiplier is a new intensively developing technology for photon detection. Insensitivity to magnetic fields, low operation voltage and small size make silicon photomultipliers very attractive for high-energy physics, astrophysics and medical applications. The presented results are obtained during the first steps taken in order to develop a setup and measurement procedures which allow to compare properties of diverse samples of silicon photomultipliers available on market. The response to low-intensity light was studied for silicon photomultipliers produced by CPTA (Russia), Hamamatsu (Japan), ITC-irst (Italy) and SensL (Ireland).

  7. Free-running InGaAs/InP single photon detector with feedback quenching IC

    International Nuclear Information System (INIS)

    Zheng, Fu; Wang, Feilong; Wang, Chao; Sun, Zhibin; Zhai, Guangjie

    2015-01-01

    InGaAs/InP avalanche photodiodes (APD) are usually employed as Geiger-mode single photon detector at near-infrared wavelength between 1.0 μm and 1.7 μm. In order to work in the free-running regime rather than gated regime, we demonstrate a feedback quenching integrated circuit to rapidly quench the avalanche and reset the APD. Because this IC is close to the APD, parasitic capacitance is largely reduced, thus reducing the quench-time, reset-time and also the afterpulsing probability. We investigated the free-running single photon detector's afterpulsing effect, de-trapping time, dark count rate and detection efficiency and also compared with gated regime operation. After corrected for deadtime and afterpulse, we found the free-running detector performance is comparable with gated regime

  8. A low-cost, ultra-fast and ultra-low noise preamplifier for silicon avalanche photodiodes

    Science.gov (United States)

    Gasmi, Khaled

    2018-02-01

    An ultra-fast and ultra-low noise preamplifier for amplifying the fast and weak electrical signals generated by silicon avalanche photodiodes has been designed and developed. It is characterized by its simplicity, compactness, reliability and low cost of construction. A very wide bandwidth of 300 MHz, a very good linearity from 1 kHz to 280 MHz, an ultra-low noise level at the input of only 1.7 nV Hz-1/2 and a very good stability are its key features. The compact size (70 mm  ×  90 mm) and light weight (45 g), as well as its excellent characteristics, make this preamplifier very competitive compared to any commercial preamplifier. The preamplifier, which is a main part of the detection system of a homemade laser remote sensing system, has been successfully tested. In addition, it is versatile and can be used in any optical detection system requiring high speed and very low noise electronics.

  9. Investigation of Avalanche Photodiodes and Multipixel Photon Counters as Light Detectors for Cosmic Rays

    Science.gov (United States)

    Vasquez, Jaime; Saavedra, Arthur; Ramos, Roxana; Tavares, Pablo; Wade, Marcus; Fan, Sewan; Haag, Brooke

    2013-04-01

    Through the Research Scholars Institute, students of Hartnell Community College experimented with the application of avalanche photodiodes (APDs) as cosmic ray detectors during the summer of 2012. An APD detector was coupled with a 10 meter long wavelength shifting fiber (WSF) wrapped around a cylindrical plastic scintillator to maximize signal detection. A photomultiplier tube (PMT) was used in conjunction to detect the same scintillation light caused by incoming cosmic rays. Two APD detectors were evaluated to confirm the viability of the setup. In addition, a similar setup was recently utilized to implement multi-pixel photon counters (MPPCs) as readout detectors. Under this configuration, a high gain preamplifier was used to amplify the signals for both the MPPC and APD detectors. We report on our results characterizing the MPPC and discuss its overall performance. Compared to the APD, our findings suggest that the MPPC detector has greater sensitivity in detecting weak light signals, and can be used in place of the PMT for certain counting applications.

  10. Optimization of eyesafe avalanche photodiode lidar for automobile safety and autonomous navigation systems

    Science.gov (United States)

    Williams, George M.

    2017-03-01

    Newly emerging accident-reducing, driver-assistance, and autonomous-navigation technology for automobiles is based on real-time three-dimensional mapping and object detection, tracking, and classification using lidar sensors. Yet, the lack of lidar sensors suitable for meeting application requirements appreciably limits practical widespread use of lidar in trucking, public livery, consumer cars, and fleet automobiles. To address this need, a system-engineering perspective to eyesafe lidar-system design for high-level advanced driver-assistance sensor systems and a design trade study including 1.5-μm spot-scanned, line-scanned, and flash-lidar systems are presented. A cost-effective lidar instrument design is then proposed based on high-repetition-rate diode-pumped solid-state lasers and high-gain, low-excess-noise InGaAs avalanche photodiode receivers and focal plane arrays. Using probabilistic receiver-operating-characteristic analysis, derived from measured component performance, a compact lidar system is proposed that is capable of 220 m ranging with 5-cm accuracy, which can be readily scaled to a 360-deg field of regard.

  11. Substitution of photomultiplier tubes by photodiodes

    International Nuclear Information System (INIS)

    Teixeira, D.L.

    1990-04-01

    The application of Si semiconductors, either of the conventional or the avalanche type, as light amplifiers in radiation detection, has been studied aiming the substitution of photomultiplier (PM) tubes by photodiodes. The objective of this work is to compare the response of photodiodes and PM tubes when coupled to scintillation crystals. A Hamamatsu Si photodiode, model S 1337-66 B Q, was coupled to a Harshaw NaI (TI) scintillation crystal of window diameter equal to 25,4 mm. Its performance was evaluated by specially designed associated electronics, compatible with the photodiode characteristics. X-ray beams from 30 to 111 KeV were used to determine the response and the repeatability of the scintillator-photodiode and the scintillator-PM tube systems. The repeatability was found to be within 0,27% for the photodiode and 0,57% for the PM tube. This work confirmed that photodiodes can be used as light amplifiers, provided their characteristics, such as light spectrum response, are considered. It also shows that further studies are necessary in order to identify the applications in radiation detection where PM tubes might be replaced by photodiodes. (author)

  12. Progresses in the simulation of Resistive Plate Chambers in avalanche mode

    Energy Technology Data Exchange (ETDEWEB)

    Abbrescia, M.; Colaleo, A.; Iaselli, G.; Loddo, F.; Maggi, M.; Marangelli, B.; Natali, S.; Nuzzo, S.; Pugliese, G.; Ranieri, A.; Romano, F.; Altieri, S.; Bruno, G.; Gianini, G.; Ratti, S.P.; Viola, L.; Vitulo, P

    1999-08-01

    New results about the simulation of Resistive Plate Chambers are reported; particular emphasis is put in the understanding of charge spectra in regions where deviations from the pure avalanche mode of operation can be present.

  13. An accurate behavioral model for single-photon avalanche diode statistical performance simulation

    Science.gov (United States)

    Xu, Yue; Zhao, Tingchen; Li, Ding

    2018-01-01

    An accurate behavioral model is presented to simulate important statistical performance of single-photon avalanche diodes (SPADs), such as dark count and after-pulsing noise. The derived simulation model takes into account all important generation mechanisms of the two kinds of noise. For the first time, thermal agitation, trap-assisted tunneling and band-to-band tunneling mechanisms are simultaneously incorporated in the simulation model to evaluate dark count behavior of SPADs fabricated in deep sub-micron CMOS technology. Meanwhile, a complete carrier trapping and de-trapping process is considered in afterpulsing model and a simple analytical expression is derived to estimate after-pulsing probability. In particular, the key model parameters of avalanche triggering probability and electric field dependence of excess bias voltage are extracted from Geiger-mode TCAD simulation and this behavioral simulation model doesn't include any empirical parameters. The developed SPAD model is implemented in Verilog-A behavioral hardware description language and successfully operated on commercial Cadence Spectre simulator, showing good universality and compatibility. The model simulation results are in a good accordance with the test data, validating high simulation accuracy.

  14. Geneva University - Silicon photomultiplier : features and applications

    CERN Multimedia

    Université de Genève

    2012-01-01

    GENEVA UNIVERSITY École de physique Département de physique nucléaire et corspusculaire 24, quai Ernest-Ansermet 1211 Genève 4 Tél.: (022) 379 62 73 Fax: (022) 379 69 92   Wednesday 7 March 2012 SEMINAIRE DE PHYSIQUE CORPUSCULAIRE 11.15 a.m. - Science II, Auditoire 1S081, 30, quai Ernest-Ansermet, 1211 Genève 4 SILICON PHOTOMULTIPLIER : FEATURES AND APPLICATIONS Dr Giulio SARACINO   University of Naples, Federico II   Silicon photomultipliers were developed about ten years ago and their use, unlike traditional photomultiplier tubes, is increasing more and more. They are an evolution of the avalanche photodiode working in Geiger mode regime. Hundreds of such diodes are connected in parallel, allowing single photon response, high detection efficiency, high gain at low bias voltage and very good timing performance. In spite of their Geiger regime, they can be considered linear devices, until the number of photon...

  15. FACT light collection - solid light concentrators in Cherenkov Astronomy

    Energy Technology Data Exchange (ETDEWEB)

    Braun, Isabel [ETH Zurich, Institute for Particle Physics, CH-8093 Zurich (Switzerland); Collaboration: FACT-Collaboration

    2011-07-01

    Pixelized cameras of Imaging Atmospheric Cherenkov Telescopes use hollow light guides with reflective surfaces based on the Winston cone design. These cones minimize insensitive spaces between the photo sensors and shield the camera from stray background light by limiting the angular acceptance to the primary reflector area. FACT (First G-APD Cherenkov Telescope) will be the first IACT with Geiger-mode avalanche photodiodes as light sensors. Solid light concentrators complementing these sensors will be used instead of hollow Winston cones. We will present simulations and measurements of our light collector design, which was optimized for the requirements of the FACT telescope and detector, and discuss the specific differences to more traditional solutions.

  16. G-APDs in Cherenkov astronomy: The FACT camera

    International Nuclear Information System (INIS)

    Krähenbühl, T.; Anderhub, H.; Backes, M.; Biland, A.; Boller, A.; Braun, I.; Bretz, T.; Commichau, V.; Djambazov, L.; Dorner, D.; Farnier, C.; Gendotti, A.; Grimm, O.; Gunten, H. von; Hildebrand, D.; Horisberger, U.; Huber, B.; Kim, K.-S.; Köhne, J.-H.; Krumm, B.

    2012-01-01

    Geiger-mode avalanche photodiodes (G-APD, SiPM) are a much discussed alternative to photomultiplier tubes in Cherenkov astronomy. The First G-APD Cherenkov Telescope (FACT) collaboration builds a camera based on a hexagonal array of 1440 G-APDs and has now finalized its construction phase. A light-collecting solid PMMA cone is glued to each G-APD to eliminate dead space between the G-APDs by increasing the active area, and to restrict the light collection angle of the sensor to the reflector area in order to reduce the amount of background light. The processing of the signals is integrated in the camera and includes the digitization using the domino ring sampling chip DRS4.

  17. Recent developments with CMOS SSPM photodetectors

    Energy Technology Data Exchange (ETDEWEB)

    Stapels, Christopher J. [Radiation Monitoring Devices, Inc., Watertown, MA (United States)], E-mail: CStapels@RMDInc.com; Barton, Paul [University of Michigan, Ann Arbor, MI (United States); Johnson, Erik B. [Radiation Monitoring Devices, Inc., Watertown, MA (United States); Wehe, David K. [University of Michigan, Ann Arbor, MI (United States); Dokhale, Purushottam; Shah, Kanai [Radiation Monitoring Devices, Inc., Watertown, MA (United States); Augustine, Frank L. [Augustine Engineering, Encinitas, CA (United States); Christian, James F. [Radiation Monitoring Devices, Inc., Watertown, MA (United States)

    2009-10-21

    Experiments and simulations using various solid-state photomultiplier (SSPM) designs have been performed to evaluate pixel layouts and explore design choices. SPICE simulations of a design for position-sensing SSPMs showed charge division in the resistor network, and anticipated timing performance of the device. The simulation results predict good position information for resistances in the range of 1-5 k{omega} and 150-{omega} preamplifier input impedance. Back-thinning of CMOS devices can possibly increase the fill factor to 100%, improve spectral sensitivity, and allow for the deposition of anti-reflective coatings after fabrication. We report initial results from back illuminating a CMOS SSPM, and single Geiger-mode avalanche photodiode (GPD) pixels, thinned to 50 {mu}m.

  18. Evaluation of single photon and Geiger mode Lidar for the 3D Elevation Program

    Science.gov (United States)

    Stoker, Jason M.; Abdullah, Qassim; Nayegandhi, Amar; Winehouse, Jayna

    2016-01-01

    Data acquired by Harris Corporation’s (Melbourne, FL, USA) Geiger-mode IntelliEarth™ sensor and Sigma Space Corporation’s (Lanham-Seabrook, MD, USA) Single Photon HRQLS sensor were evaluated and compared to accepted 3D Elevation Program (3DEP) data and survey ground control to assess the suitability of these new technologies for the 3DEP. While not able to collect data currently to meet USGS lidar base specification, this is partially due to the fact that the specification was written for linear-mode systems specifically. With little effort on part of the manufacturers of the new lidar systems and the USGS Lidar specifications team, data from these systems could soon serve the 3DEP program and its users. Many of the shortcomings noted in this study have been reported to have been corrected or improved upon in the next generation sensors.

  19. Characterization and quality control of avalanche photodiode arrays for the Clear-PEM detector modules

    International Nuclear Information System (INIS)

    Abreu, Conceicao; Amaral, Pedro; Carrico, Bruno; Ferreira, Miguel; Luyten, Joan; Moura, Rui; Ortigao, Catarina; Rato, Pedro; Varela, Joao

    2007-01-01

    Clear-PEM is a Positron Emission Mammography (PEM) prototype being developed in the framework of the Crystal Clear Collaboration at CERN. This device is a dedicated PET camera for mammography, based on LYSO:Ce scintillator crystals, Avalanche PhotoDiodes (APD) and a fast, low-noise electronics readout system, designed to examine both the breast and the axillary lymph node areas, and aiming at the detection of tumors down to 2 mm in diameter. The prototype has two planar detector heads, each composed of 96 detector modules. The Clear-PEM detector module is composed of a matrix of 32 identical 2x2x20 mm 3 LYSO:Ce crystals read at both ends by Hamamatsu S8550 APD arrays (4x8) for Depth-of-Interaction (DoI) capability. The APD arrays were characterized by the measurement of gain and dark current as a function of bias voltage, under controlled temperature conditions. Two independent setups were used. The full set of 398 APD arrays followed a well-defined quality control (QC) protocol, aiming at the rejection of arrays not complying within defined specifications. From a total of 398 arrays, only 2 (0.5%) were rejected, reassuring the trust in these detectors for prototype assembly and future developments

  20. Long-term operation of a multi-channel cosmic muon system based on scintillation counters with MRS APD light readout

    CERN Document Server

    Akindinov, A.; Grigoriev, E.; Grishuk, Yu.; Kuleshov, S.; Mal'kevich, D.; Martemiyanov, A.; Nedosekin, A.; Ryabinin, M.; Voloshin, K.

    2009-01-01

    A Cosmic Ray Test Facility (CRTF) is the first large-scale implementation of a scintillation triggering system based on a new scintillation technique known as START. In START, the scintillation light is collected and transported by WLS optical fibers, while light detection is performed by pairs of avalanche photodiodes with the Metal-Resistor-Semiconductor structure operated in the Geiger mode (MRS APD). START delivers 100% efficiency of cosmic muon detection, while its intrinsic noise level is less than 10^{-2} Hz. CRTF, consisting of 160 START channels, has been continuously operated by the ALICE TOF collaboration for more than 25 000 hours, and has demonstrated a high level of stability. Fewer than 10% of MRS APDs had to be replaced during this period.

  1. Detection of the scintillation light emitted from direct-bandgap compound semiconductors by a Si avalanche photodiode at 150 mK

    International Nuclear Information System (INIS)

    Yasumune, Takashi; Takayama, Nobuyasu; Maehata, Keisuke; Ishibashi, Kenji; Umeno, Takahiro

    2008-01-01

    In this work, the direct-bandgap compound semiconductor materials are irradiated by α particles emitted from 241 Am for the detection of scintillation light at the temperature of 150 mK. For the irradiation experiment, two disk shaped samples were fabricated from an epoxy resin mixed with the powder of PbI 2 and CuI, respectively. Each disk-samples was cooled down to 150 mK by a compact liquid helium-free dilution refrigerator. A Si avalanche photodiode (APD) was employed for detecting the scintillation light emitted from the disk-sample inside the refrigerator. The detection signal current of Si APD was converted into the voltage pulses by a charge sensitive preamplifier. The voltage pulses of the scintillation light emitted from the direct-bandgap semiconductors were observed at the temperature of 150 mK. (author)

  2. Ge/graded-SiGe multiplication layers for low-voltage and low-noise Ge avalanche photodiodes on Si

    Science.gov (United States)

    Miyasaka, Yuji; Hiraki, Tatsurou; Okazaki, Kota; Takeda, Kotaro; Tsuchizawa, Tai; Yamada, Koji; Wada, Kazumi; Ishikawa, Yasuhiko

    2016-04-01

    A new structure is examined for low-voltage and low-noise Ge-based avalanche photodiodes (APDs) on Si, where a Ge/graded-SiGe heterostructure is used as the multiplication layer of a separate-absorption-carrier-multiplication structure. The Ge/SiGe heterojunction multiplication layer is theoretically shown to be useful for preferentially enhancing impact ionization for photogenerated holes injected from the Ge optical-absorption layer via the graded SiGe, reflecting the valence band discontinuity at the Ge/SiGe interface. This property is effective not only for the reduction of operation voltage/electric field strength in Ge-based APDs but also for the reduction of excess noise resulting from the ratio of the ionization coefficients between electrons and holes being far from unity. Such Ge/graded-SiGe heterostructures are successfully fabricated by ultrahigh-vacuum chemical vapor deposition. Preliminary pin diodes having a Ge/graded-SiGe multiplication layer act reasonably as photodetectors, showing a multiplication gain larger than those for diodes without the Ge/SiGe heterojunction.

  3. Design and performance of single photon APD focal plane arrays for 3-D LADAR imaging

    Science.gov (United States)

    Itzler, Mark A.; Entwistle, Mark; Owens, Mark; Patel, Ketan; Jiang, Xudong; Slomkowski, Krystyna; Rangwala, Sabbir; Zalud, Peter F.; Senko, Tom; Tower, John; Ferraro, Joseph

    2010-08-01

    ×We describe the design, fabrication, and performance of focal plane arrays (FPAs) for use in 3-D LADAR imaging applications requiring single photon sensitivity. These 32 × 32 FPAs provide high-efficiency single photon sensitivity for three-dimensional LADAR imaging applications at 1064 nm. Our GmAPD arrays are designed using a planarpassivated avalanche photodiode device platform with buried p-n junctions that has demonstrated excellent performance uniformity, operational stability, and long-term reliability. The core of the FPA is a chip stack formed by hybridizing the GmAPD photodiode array to a custom CMOS read-out integrated circuit (ROIC) and attaching a precision-aligned GaP microlens array (MLA) to the back-illuminated detector array. Each ROIC pixel includes an active quenching circuit governing Geiger-mode operation of the corresponding avalanche photodiode pixel as well as a pseudo-random counter to capture per-pixel time-of-flight timestamps in each frame. The FPA has been designed to operate at frame rates as high as 186 kHz for 2 μs range gates. Effective single photon detection efficiencies as high as 40% (including all optical transmission and MLA losses) are achieved for dark count rates below 20 kHz. For these planar-geometry diffused-junction GmAPDs, isolation trenches are used to reduce crosstalk due to hot carrier luminescence effects during avalanche events, and we present details of the crosstalk performance for different operating conditions. Direct measurement of temporal probability distribution functions due to cumulative timing uncertainties of the GmAPDs and ROIC circuitry has demonstrated a FWHM timing jitter as low as 265 ps (standard deviation is ~100 ps).

  4. Evaluation of Space Radiation Effects on HgCdTe Avalanche Photodiode Arrays for Lidar Applications

    Science.gov (United States)

    Sun, Xiaoli; Abshire, James B.; Lauenstein, Jean-Marie; Sullivan, William III; Beck, Jeff; Hubbs, John E.

    2018-01-01

    We report the results from proton and gamma ray radiation testing of HgCdTe avalanche photodiode (APD) arrays developed by Leonardo DRS for space lidar detectors. We tested these devices with both approximately 60 MeV protons and gamma rays, with and without the read out integrated circuit (ROIC). We also measured the transient responses with the device fully powered and with the APD gain from unity to greater than 1000. The detectors produced a large current impulse in response to each proton hit but the response completely recovered within 1 microsecond. The devices started to have persistent damage at a proton fluence of 7e10 protons/cm2, equivalent to 10 krad(Si) total ionization dose. The dark current became much higher after the device was warmed to room temperature and cooled to 80K again, but it completely annealed after baking at 85 C for several hours. These results showed the HgCdTe APD arrays are suitable for use in space lidar for typical Earth orbiting and planetary missions provided that provisions are made to heat the detector chip to 85 C for several hours after radiation damage becomes evident that system performance is impacted.

  5. Nuclear resonant scattering measurements on (57)Fe by multichannel scaling with a 64-pixel silicon avalanche photodiode linear-array detector.

    Science.gov (United States)

    Kishimoto, S; Mitsui, T; Haruki, R; Yoda, Y; Taniguchi, T; Shimazaki, S; Ikeno, M; Saito, M; Tanaka, M

    2014-11-01

    We developed a silicon avalanche photodiode (Si-APD) linear-array detector for use in nuclear resonant scattering experiments using synchrotron X-rays. The Si-APD linear array consists of 64 pixels (pixel size: 100 × 200 μm(2)) with a pixel pitch of 150 μm and depletion depth of 10 μm. An ultrafast frontend circuit allows the X-ray detector to obtain a high output rate of >10(7) cps per pixel. High-performance integrated circuits achieve multichannel scaling over 1024 continuous time bins with a 1 ns resolution for each pixel without dead time. The multichannel scaling method enabled us to record a time spectrum of the 14.4 keV nuclear radiation at each pixel with a time resolution of 1.4 ns (FWHM). This method was successfully applied to nuclear forward scattering and nuclear small-angle scattering on (57)Fe.

  6. Digitally grown AlInAsSb for high gain separate absorption, grading, charge, and multiplication avalanche photodiodes

    Science.gov (United States)

    Lyu, Yuexi; Han, Xi; Sun, Yaoyao; Jiang, Zhi; Guo, Chunyan; Xiang, Wei; Dong, Yinan; Cui, Jie; Yao, Yuan; Jiang, Dongwei; Wang, Guowei; Xu, Yingqiang; Niu, Zhichuan

    2018-01-01

    We report on the growth of high quality GaSb-based AlInAsSb quaternary alloy by molecular beam epitaxy (MBE) to fabricate avalanche photodiodes (APDs). By means of high resolution X-ray diffraction (HRXRD) and scanning transmission electron microscope (STEM), phase separation phenomenon of AlInAsSb random alloy with naturally occurring vertical superlattice configuration was demonstrated. To overcome the tendency for phase segregation while maintaining a highly crystalline film, a digital alloy technique with migration-enhanced epitaxy growth method was employed, using a shutter sequence of AlSb, AlAs, AlSb, Sb, In, InAs, In, Sb. AlInAsSb digital alloy has proved to be reproducible and consistent with single phase, showing sharp satellite peaks on HRXRD rocking curve and smooth surface morphology under atomic force microscopy (AFM). Using optimized digital alloy, AlInAsSb separate absorption, grading, charge, and multiplication (SAGCM) APD was grown and fabricated. At room temperature, the device showed high performance with low dark current density of ∼14.1 mA/cm2 at 95% breakdown and maximum stable gain before breakdown as high as ∼200, showing the potential for further applications in optoelectronic devices.

  7. FACT-The first Cherenkov telescope using a G-APD camera for TeV gamma-ray astronomy

    International Nuclear Information System (INIS)

    Anderhub, H.; Backes, M.; Biland, A.; Boller, A.; Braun, I.; Bretz, T.; Commichau, S.; Commichau, V.; Domke, M.; Dorner, D.; Gendotti, A.; Grimm, O.; Gunten, H. von; Hildebrand, D.; Horisberger, U.; Koehne, J.-H.; Kraehenbuehl, T.; Kranich, D.; Krumm, B.; Lorenz, E.

    2011-01-01

    Geiger-mode Avalanche Photodiodes (G-APD) bear the potential to significantly improve the sensitivity of Imaging Air Cherenkov Telescopes (IACT). We are currently building the First G-APD Cherenkov Telescope (FACT) by refurbishing an old IACT with a mirror area of 9.5 square meters and are constructing a new, fine-pixelized camera using novel G-APDs. The main goal is to evaluate the performance of a complete system by observing very high energy gamma-rays from the Crab Nebula. This is an important field test to check the feasibility of G-APD-based cameras to replace at some time the PMT-based cameras of planned future IACTs like AGIS and CTA. In this article, we present the basic design of such a camera as well as some important details.

  8. A lens-coupled scintillation counter in cryogenic environment

    International Nuclear Information System (INIS)

    Stoykov, A; Scheuermann, R; Amato, A; Bartkowiak, M; Konter, J A; Rodriguez, J; Sedlak, K

    2011-01-01

    In this work we present an elegant solution for a scintillation counter to be integrated into a cryogenic system. Its distinguishing feature is the absence of a continuous light guide coupling the scintillation and the photodetector parts, operating at cryogenic and room temperatures respectively. The prototype detector consists of a plastic scintillator with glued-in wavelength-shifting fiber located inside a cryostat, a Geiger-mode Avalanche Photodiode (G-APD) outside the cryostat, and a lens system guiding the scintillation light re-emitted by the fiber to the G-APD through optical windows in the cryostat shields. With a 0.8 mm diameter multiclad fiber and a 1 mm active area G-APD the coupling efficiency of the 'lens light guide' is about 50%. A reliable performance of the detector down to 3 K is demonstrated.

  9. 3D Silicon Coincidence Avalanche Detector (3D-SiCAD) for charged particle detection

    Science.gov (United States)

    Vignetti, M. M.; Calmon, F.; Pittet, P.; Pares, G.; Cellier, R.; Quiquerez, L.; Chaves de Albuquerque, T.; Bechetoille, E.; Testa, E.; Lopez, J.-P.; Dauvergne, D.; Savoy-Navarro, A.

    2018-02-01

    Single-Photon Avalanche Diodes (SPADs) are p-n junctions operated in Geiger Mode by applying a reverse bias above the breakdown voltage. SPADs have the advantage of featuring single photon sensitivity with timing resolution in the picoseconds range. Nevertheless, their relatively high Dark Count Rate (DCR) is a major issue for charged particle detection, especially when it is much higher than the incoming particle rate. To tackle this issue, we have developed a 3D Silicon Coincidence Avalanche Detector (3D-SiCAD). This novel device implements two vertically aligned SPADs featuring on-chip electronics for the detection of coincident avalanche events occurring on both SPADs. Such a coincidence detection mode allows an efficient discrimination of events related to an incoming charged particle (producing a quasi-simultaneous activation of both SPADs) from dark counts occurring independently on each SPAD. A 3D-SiCAD detector prototype has been fabricated in CMOS technology adopting a 3D flip-chip integration technique, and the main results of its characterization are reported in this work. The particle detection efficiency and noise rejection capability for this novel device have been evaluated by means of a β- strontium-90 radioactive source. Moreover the impact of the main operating parameters (i.e. the hold-off time, the coincidence window duration, the SPAD excess bias voltage) over the particle detection efficiency has been studied. Measurements have been performed with different β- particles rates and show that a 3D-SiCAD device outperforms single SPAD detectors: the former is indeed capable to detect particle rates much lower than the individual DCR observed in a single SPAD-based detectors (i.e. 2 to 3 orders of magnitudes lower).

  10. Geiger-mueller radiation detector with means for detecting and indicating the existence of radiation overload

    International Nuclear Information System (INIS)

    Kovacs, T.; Mills, A.P.; Pfeiffer, L.N.

    1981-01-01

    When subjected to radiation overload existing geiger-mueller counters may give an erroneously low reading, resulting in possible hazard to personnel. The instant invention discloses simple and inexpensive apparatus to remedy this dangerous shortcoming. Depending on the geometry of the detector tube, two possible failure modes have been identified, and circuitry is disclosed to detect the existence of these respective failure modes. The disclosed apparatus indicates the absence of an overload condition, in addition to signaling, by both visible and audible means, the existence of excessive radiation that might result in erroneously low reading of the geiger-mueller counter

  11. A prototype high-resolution animal positron tomograph with avalanche photodiode arrays and LSO crystals

    International Nuclear Information System (INIS)

    Ziegler, S.I.; Pichler, B.J.; Rafecas, M.; Schwaiger, M.

    2001-01-01

    To fully utilize positron emission tomography (PET) as a non-invasive tool for tissue characterization, dedicated instrumentation is being developed which is specially suited for imaging mice and rats. Semiconductor detectors, such as avalanche photodiodes (APDs), may offer an alternative to photomultiplier tubes for the readout of scintillation crystals. Since the scintillation characteristics of lutetium oxyorthosilicate (LSO) are well matched to APDs, the combination of LSO and APDs seems favourable, and the goal of this study was to build a positron tomograph with LSO-APD modules to prove the feasibility of such an approach. A prototype PET scanner based on APD readout of small, individual LSO crystals was developed for tracer studies in mice and rats. The tomograph consists of two sectors (86 mm distance), each comprising three LSO-APD modules, which can be rotated for the acquisition of complete projections. In each module, small LSO crystals (3.7 x 3.7 x 12 mm 3 ) are individually coupled to one channel within matrices containing 2 x 8 square APDs (2.6 x 2.6 mm 2 sensitive area per channel). The list-mode data are reconstructed with a penalized weighted least squares algorithm which includes the spatially dependent line spread function of the tomograph. Basic performance parameters were measured with phantoms and first experiments with rats and mice were conducted to introduce this methodology for biomedical imaging. The reconstructed field of view covers 68 mm, which is 80% of the total detector diameter. Image resolution was shown to be 2.4 mm within the whole reconstructed field of view. Using a lower energy threshold of 450 keV, the system sensitivity was 350 Hz/MBq for a line source in air in the centre of the field of view. In a water-filled cylinder of 4.6 cm diameter, the scatter fraction at the centre of the field of view was 16% (450 keV threshold). The count rate was linear up to 700 coincidence counts per second. In vivo studies of anaesthetized

  12. An Acoustic Charge Transport Imager for High Definition Television Applications: Reliability Modeling and Parametric Yield Prediction of GaAs Multiple Quantum Well Avalanche Photodiodes. Degree awarded Oct. 1997

    Science.gov (United States)

    Hunt, W. D.; Brennan, K. F.; Summers, C. J.; Yun, Ilgu

    1994-01-01

    Reliability modeling and parametric yield prediction of GaAs/AlGaAs multiple quantum well (MQW) avalanche photodiodes (APDs), which are of interest as an ultra-low noise image capture mechanism for high definition systems, have been investigated. First, the effect of various doping methods on the reliability of GaAs/AlGaAs multiple quantum well (MQW) avalanche photodiode (APD) structures fabricated by molecular beam epitaxy is investigated. Reliability is examined by accelerated life tests by monitoring dark current and breakdown voltage. Median device lifetime and the activation energy of the degradation mechanism are computed for undoped, doped-barrier, and doped-well APD structures. Lifetimes for each device structure are examined via a statistically designed experiment. Analysis of variance shows that dark-current is affected primarily by device diameter, temperature and stressing time, and breakdown voltage depends on the diameter, stressing time and APD type. It is concluded that the undoped APD has the highest reliability, followed by the doped well and doped barrier devices, respectively. To determine the source of the degradation mechanism for each device structure, failure analysis using the electron-beam induced current method is performed. This analysis reveals some degree of device degradation caused by ionic impurities in the passivation layer, and energy-dispersive spectrometry subsequently verified the presence of ionic sodium as the primary contaminant. However, since all device structures are similarly passivated, sodium contamination alone does not account for the observed variation between the differently doped APDs. This effect is explained by the dopant migration during stressing, which is verified by free carrier concentration measurements using the capacitance-voltage technique.

  13. Silicon avalanche photodiodes on the base of metal-resistor-semiconductor (MRS) structures

    CERN Document Server

    Saveliev, V

    2000-01-01

    The development of a high quantum efficiency, fast photodetector, with internal gain amplification for the wavelength range 450-600 nm is one of the critical issues for experimental physics - registration of low-intensity light photons flux. The new structure of Silicon Avalanche Detectors with high internal amplification (10 sup 5 -10 sup 6) has been designed, manufactured and tested for registration of visible light photons and charge particles. The main features of Metal-Resistor-Semiconductor (MRS) structures are the high charge multiplication in nonuniform electric field near the 'needle' pn-junction and negative feedback for stabilization of avalanche process due to resistive layer.

  14. Development of an integrated four-channel fast avalanche-photodiode detector system with nanosecond time resolution

    Science.gov (United States)

    Li, Zhenjie; Li, Qiuju; Chang, Jinfan; Ma, Yichao; Liu, Peng; Wang, Zheng; Hu, Michael Y.; Zhao, Jiyong; Alp, E. E.; Xu, Wei; Tao, Ye; Wu, Chaoqun; Zhou, Yangfan

    2017-10-01

    A four-channel nanosecond time-resolved avalanche-photodiode (APD) detector system is developed at Beijing Synchrotron Radiation. It uses a single module for signal processing and readout. This integrated system provides better reliability and flexibility for custom improvement. The detector system consists of three parts: (i) four APD sensors, (ii) four fast preamplifiers and (iii) a time-digital-converter (TDC) readout electronics. The C30703FH silicon APD chips fabricated by Excelitas are used as the sensors of the detectors. It has an effective light-sensitive area of 10 × 10 mm2 and an absorption layer thickness of 110 μm. A fast preamplifier with a gain of 59 dB and bandwidth of 2 GHz is designed to readout of the weak signal from the C30703FH APD. The TDC is realized by a Spartan-6 field-programmable-gate-array (FPGA) with multiphase method in a resolution of 1ns. The arrival time of all scattering events between two start triggers can be recorded by the TDC. The detector has been used for nuclear resonant scattering study at both Advanced Photon Source and also at Beijing Synchrotron Radiation Facility. For the X-ray energy of 14.4 keV, the time resolution, the full width of half maximum (FWHM) of the detector (APD sensor + fast amplifier) is 0.86 ns, and the whole detector system (APD sensors + fast amplifiers + TDC readout electronics) achieves a time resolution of 1.4 ns.

  15. Investigation of depth-of-interaction by pulse shape discrimination in multicrystal detectors read out by avalanche photodiodes

    International Nuclear Information System (INIS)

    Saoudi, A.; Pepin, C.M.; Dion, F.; Bentourkia, M.; Lecomte, R.; Dautet, H.

    1999-01-01

    The measurement of depth of interaction (DOI) within detectors is necessary to improve resolution uniformity across the FOV of small diameter PET scanners. DOI encoding by pulse shape discrimination (PSD) has definite advantages as it requires only one readout per pixel and it allows DOI measurement of photoelectric and Compton events. The PSD time characteristics of various scintillators were studied with avalanche photodiodes (APD) and the identification capability was tested in multi-crystal assemblies with up to four scintillators. In the PSD time spectrum of an APD-GSO/LSO/BGO/CsI(Tl) assembly, four distinct time peaks at 45, 26, 88 and 150 ns relative to a fast test pulse, having resolution of 10.6, 5.2, 20 and 27 ns, can be easily separated. Whereas the number and position of scintillators in the multi-crystal assemblies affect detector performance, the ability to identify crystals is not compromised. Compton events have a significant effect on PSD accuracy, suggesting that photopeak energy gating should be used for better crystal identification. However, more sophisticated PSD techniques using parametric time-energy histograms can also improve crystal identification in cases where PSD time or energy discrimination alone is inadequate. These results confirm the feasibility of PSD DOI encoding with APD-based detectors for PET

  16. Optimization of single photon detection model based on GM-APD

    Science.gov (United States)

    Chen, Yu; Yang, Yi; Hao, Peiyu

    2017-11-01

    One hundred kilometers high precision laser ranging hopes the detector has very strong detection ability for very weak light. At present, Geiger-Mode of Avalanche Photodiode has more use. It has high sensitivity and high photoelectric conversion efficiency. Selecting and designing the detector parameters according to the system index is of great importance to the improvement of photon detection efficiency. Design optimization requires a good model. In this paper, we research the existing Poisson distribution model, and consider the important detector parameters of dark count rate, dead time, quantum efficiency and so on. We improve the optimization of detection model, select the appropriate parameters to achieve optimal photon detection efficiency. The simulation is carried out by using Matlab and compared with the actual test results. The rationality of the model is verified. It has certain reference value in engineering applications.

  17. Compact lidar system using laser diode, binary continuous wave power modulation, and an avalanche photodiode-based receiver controlled by a digital signal processor

    Science.gov (United States)

    Ardanuy, Antoni; Comerón, Adolfo

    2018-04-01

    We analyze the practical limits of a lidar system based on the use of a laser diode, random binary continuous wave power modulation, and an avalanche photodiode (APD)-based photereceiver, combined with the control and computing power of the digital signal processors (DSP) currently available. The target is to design a compact portable lidar system made all in semiconductor technology, with a low-power demand and an easy configuration of the system, allowing change in some of its features through software. Unlike many prior works, we emphasize the use of APDs instead of photomultiplier tubes to detect the return signal and the application of the system to measure not only hard targets, but also medium-range aerosols and clouds. We have developed an experimental prototype to evaluate the behavior of the system under different environmental conditions. Experimental results provided by the prototype are presented and discussed.

  18. Updated design for a low-noise, wideband transimpedance photodiode amplifier

    International Nuclear Information System (INIS)

    Paul, S. F.; Marsala, R.

    2006-01-01

    The high-speed rotation diagnostic developed for Columbia's HBT-EP tokamak requires a high quantum efficiency, very low drift detector/amplifier combination. An updated version of the circuit developed originally for the beam emission spectroscopy experiment on TFTR is being used. A low dark current (2 nA at 15 V bias), low input source capacitance (2 pF) FFD-040 N-type Si photodiode is operated in photoconductive mode. It has a quantum efficiency of 40% at the 468.6 nm (He II line that is being observed). A low-noise field-effect transistor (InterFET IFN152 with e Na =1.2 nV/√Hz) is used to reduce the noise in the transimpedance preamplifier (A250 AMPTEK op-amp) and a very high speed (unity-gain bandwidth=200 MHz) voltage feedback amplifier (LM7171) is used to restore the frequency response up to 100 kHz. This type of detector/amplifier is photon-noise limited at this bandwidth for incident light with a power of >∼2 nW. The circuit has been optimized using SIMETRIX 4.0 SPICE software and a prototype circuit has been tested successfully. Though photomultipliers and avalanche photodiodes can detect much lower light levels, for light levels >2 nW and a 10 kHz bandwidth, this detector/amplifier combination is more sensitive because of the absence of excess (internally generated) noise

  19. Avalanche mode of high-voltage overloaded p+–i–n+ diode switching to the conductive state by pulsed illumination

    International Nuclear Information System (INIS)

    Kyuregyan, A. S.

    2015-01-01

    A simple analytical theory of the picosecond switching of high-voltage overloaded p + –i–n + photodiodes to the conductive state by pulsed illumination is presented. The relations between the parameters of structure, light pulse, external circuit, and main process characteristics, i.e., the amplitude of the active load current pulse, delay time, and switching duration, are derived and confirmed by numerical simulation. It is shown that the picosecond light pulse energy required for efficient switching can be decreased by 6–7 orders of magnitude due to the intense avalanche multiplication of electrons and holes. This offers the possibility of using pulsed semiconductor lasers as a control element of optron pairs

  20. Angle sensitive single photon avalanche diode

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Changhyuk, E-mail: cl678@cornell.edu; Johnson, Ben, E-mail: bcj25@cornell.edu; Molnar, Alyosha, E-mail: am699@cornell.edu [Electrical and Computer Engineering, Cornell University, Ithaca, New York 14850 (United States)

    2015-06-08

    An ideal light sensor would provide exact information on intensity, timing, location, and angle of incoming photons. Single photon avalanche diodes (SPADs) provide such desired high (single photon) sensitivity with precise time information and can be implemented at a pixel-scale to form an array to extract spatial information. Furthermore, recent work has demonstrated photodiode-based structures (combined with micro-lenses or diffraction gratings) that are capable of encoding both spatial and angular information of incident light. In this letter, we describe the implementation of such a grating structure on SPADs to realize a pixel-scale angle-sensitive single photon avalanche diode (A-SPAD) built in a standard CMOS process. While the underlying SPAD structure provides high sensitivity, the time information of the two layers of diffraction gratings above offers angle-sensitivity. Such a unique combination of SPAD and diffraction gratings expands the sensing dimensions to pave a path towards lens-less 3-D imaging and light-field time-of-flight imaging.

  1. Performance and simulation of a double-gap resistive plate chamber in the avalanche mode

    CERN Document Server

    Ahn Sung Hwan; Hong Byung Sik; Hong Seong Jong; Ito, M; Kang, T I; Kim, B I; Kim, J H; Kim, Y J; Kim, Y U; Koo, D G; Lee Hyup Woo; Lee, K B; Lee Kyong Sei; Lee Seok Jae; Lim, J K; Moon, D H; Nam, S K; Park, S; Park, W J; Rhee June Tak; Ryu, M S; Sim Kwang Souk

    2004-01-01

    We present a detailed analysis of the time and the charge signals of a prototype double-gap resistive plate chamber for the endcap region of the Compact Muon Solenoid (CMS) detector at the Large Hadron Collider (LHC). The chamber was built with relatively low-resistivity bakelite. The time and the charge results demonstrate that the high- voltage plateau, which satisfies various CMS requirements for the efficiency, the noise cluster rate, the fraction of the large signal, and the streamer probability, can be extended at least up to 400 V with the present design. In addition, a simple avalanche multiplication model is studied in detail. The model can reproduce the experimental charge spectra reasonably well. The charge information enables us to estimate the effective Townsend coefficient in avalanche-mode operation.

  2. Camera Concepts for the Advanced Gamma-Ray Imaging System (AGIS)

    Science.gov (United States)

    Nepomuk Otte, Adam

    2009-05-01

    The Advanced Gamma-Ray Imaging System (AGIS) is a concept for the next generation observatory in ground-based very high energy gamma-ray astronomy. Design goals are ten times better sensitivity, higher angular resolution, and a lower energy threshold than existing Cherenkov telescopes. Each telescope is equipped with a camera that detects and records the Cherenkov-light flashes from air showers. The camera is comprised of a pixelated focal plane of blue sensitive and fast (nanosecond) photon detectors that detect the photon signal and convert it into an electrical one. The incorporation of trigger electronics and signal digitization into the camera are under study. Given the size of AGIS, the camera must be reliable, robust, and cost effective. We are investigating several directions that include innovative technologies such as Geiger-mode avalanche-photodiodes as a possible detector and switched capacitor arrays for the digitization.

  3. Fine-grained hodoscopes based on scintillating optical fibers

    International Nuclear Information System (INIS)

    Borenstein, S.R.; Strand, R.C.

    1981-01-01

    In order to exploit the high event rates at ISABELLE, it will be necessary to have fast detection with fine spatial resolution. The authors are currently constructing a prototype fine-grained hodoscope, the elements of which are scintillating optical fibers. The fibers have been drawn from commercially available plastic scintillator which has been clad with a thin layer of silicone. So far it has been demonstrated with one mm diameter fibers, that with a photodetector at each end, the fibers are more than 99% efficient for lengths of about 60 cm. The readout will be accomplished either with small diameter photomultiplier tubes or avalanche photodiodes used either in the linear or Geiger mode. The program of fiber development and evaluation is described. The status of the APD as a readout element is discussed, and an optical encoding readout scheme is described for events of low multiplicity

  4. Avalanche mode of high-voltage overloaded p{sup +}–i–n{sup +} diode switching to the conductive state by pulsed illumination

    Energy Technology Data Exchange (ETDEWEB)

    Kyuregyan, A. S., E-mail: ask@vei.ru [Lenin All-Russia Electrical Engineering Institute (Russian Federation)

    2015-07-15

    A simple analytical theory of the picosecond switching of high-voltage overloaded p{sup +}–i–n{sup +} photodiodes to the conductive state by pulsed illumination is presented. The relations between the parameters of structure, light pulse, external circuit, and main process characteristics, i.e., the amplitude of the active load current pulse, delay time, and switching duration, are derived and confirmed by numerical simulation. It is shown that the picosecond light pulse energy required for efficient switching can be decreased by 6–7 orders of magnitude due to the intense avalanche multiplication of electrons and holes. This offers the possibility of using pulsed semiconductor lasers as a control element of optron pairs.

  5. Avalanche photoconductive switching

    Science.gov (United States)

    Pocha, M. D.; Druce, R. L.; Wilson, M. J.; Hofer, W. W.

    This paper describes work being done at Lawrence Livermore National Laboratory on the avalanche mode of operation of laser triggered photoconductive switches. We have been able to generate pulses with amplitudes of 2 kV to 35 kV and rise times of 300 to 500 ps, and with a switching gain (energy of output electrical pulse vs energy of trigger optical pulse) of 10(exp 3) to over 10(exp 5). Switches with two very different physical configurations and with two different illumination wavelengths (1.06 micrometer, 890 nm) exhibit very similar behavior. The avalanche switching behavior, therefore, appears to be related to the material parameters rather than the optical wavelength or switch geometry. Considerable further work needs to be done to fully characterize and understand this mode of operation.

  6. Avalanche photoconductive switching

    Energy Technology Data Exchange (ETDEWEB)

    Pocha, M.D.; Druce, R.L.; Wilson, M.J.; Hofer, W.W.

    1989-01-01

    This paper describes work being done at Lawrence Livermore National Laboratory on the avalanche mode of operation of laser triggered photoconductive switches. We have been able to generate pulses with amplitudes of 2 kV--35 kV and rise times of 300--500 ps, and with a switching gain (energy of output electrical pulse vs energy of trigger optical pulse) of 10{sup 3} to over 10{sup 5}. Switches with two very different physical configurations and with two different illumination wavelengths (1.06 {mu}m, 890 nm) exhibit very similar behavior. The avalanche switching behavior, therefore, appears to be related to the material parameters rather than the optical wavelength or switch geometry. Considerable further work needs to be done to fully characterize and understand this mode of operation. 3 refs., 6 figs.

  7. A new CMOS SiGeC avalanche photo-diode pixel for IR sensing

    Science.gov (United States)

    Augusto, Carlos; Forester, Lynn; Diniz, Pedro C.

    2009-05-01

    Near-infra-red sensing with silicon is limited by the bandgap of silicon, corresponding to a maximum wavelength of absorption of 1.1 μm. A new type of CMOS sensor is presented, which uses a SiGeC epitaxial film in conjunction with novel device architecture to extend absorption into the infra-red. The SiGeC film composition and thickness determine the spectrum of absorption; in particular for SiGeC superlattices, the layer ordering to create pseudo direct bandgaps is the critical parameter. In this new device architecture, the p-type SiGeC film is grown on an active region surrounded by STI, linked to the S/D region of an adjacent NMOS, under the STI by a floating N-Well. On a n-type active, a P-I-N device is formed, and on a p-type active, a P-I-P device is formed, each sensing different regions of the spectrum. The SiGeC films can be biased for avalanche operation, as the required vertical electric field is confined to the region near the heterojunction interface, thereby not affecting the gate oxide of the adjacent NMOS. With suitable heterojunction and doping profiles, the avalanche region can also be bandgap engineered, allowing for avalanche breakdown voltages that are compatible with CMOS devices.

  8. Local and global performance of double-gap resistive plate chambers operated in avalanche mode

    Energy Technology Data Exchange (ETDEWEB)

    Abbrescia, M.; Colaleo, A.; Iaselli, G.; Loddo, F.; Maggi, M.; Marangelli, B.; Natali, S.; Nuzzo, S.; Pugliese, G.; Ranieri, A.; Romano, F.; Altieri, S.; Belli, G.; Bruno, G.; Gianini, G.; Ratti, S.P.; Viola, L.; Vitulo, P.; Sergueev, S

    1999-09-21

    Two large double-gap resistive plate chambers, with 2 and 3 mm gap widths, were tested to study their response uniformity when operated in avalanche mode. The effects of mechanical tolerances and the presence of the spacers is thoroughly examined. Results on efficiency and time resolution are presented. We find that average performance and response uniformity over the whole chamber surface are fully adequate to the requirements of future collider experiments. (author)

  9. Four-layer depth-of-interaction PET detector for high resolution PET using a multi-pixel S8550 avalanche photodiode

    Energy Technology Data Exchange (ETDEWEB)

    Nishikido, Fumihiko, E-mail: funis@nirs.go.j [Molecular Imaging Center, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555 (Japan); Inadama, Naoko [Molecular Imaging Center, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555 (Japan); Oda, Ichiro [Shimadzu Corporation, Nishinokyo Kuwabaracho 1 Nakagyo-ku, Kyoto-shi, Kyoto 604-8511 (Japan); Shibuya, Kengo; Yoshida, Eiji; Yamaya, Taiga [Molecular Imaging Center, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555 (Japan); Kitamura, Keishi [Shimadzu Corporation, Nishinokyo Kuwabaracho 1 Nakagyo-ku, Kyoto-shi, Kyoto 604-8511 (Japan); Murayama, Hideo [Molecular Imaging Center, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555 (Japan)

    2010-09-21

    Avalanche photodiodes (APDs) are being used as photodetectors in positron emission tomography (PET) because they have many advantages over photomultipliers (PMTs) typically used in PET detectors. We have developed a PET detector that consists of a multi-pixel APD and a 6x6x4 array of 1.46x1.46 mm{sup 2}x4.5 m LYSO crystals for a small animal PET scanner. The detector can identify four-layer depth of interaction (DOI) with a position-sensitive APD coupled to the backside of a crystal array by just an optimized reflector arrangement. Since scintillation lights are shared among many pixels by the method, weaker signals in APD pixels far from the interacting crystals are affected by noise. To evaluate the performance of the four-layer DOI detector with the APD and the influence of electrical noise on our method, we constructed a prototype DOI detector and tested its performance. We found, except for crystal elements on the edge of the crystal array, all crystal elements could be identified from the 2D position histogram. An energy resolution of 16.9% was obtained for the whole crystal array of the APD detector. The results of noise dependence of detector performances indicated that the DOI detector using the APD could achieve sufficient performance even when using application-specific integrated circuits.

  10. Four-layer depth-of-interaction PET detector for high resolution PET using a multi-pixel S8550 avalanche photodiode

    International Nuclear Information System (INIS)

    Nishikido, Fumihiko; Inadama, Naoko; Oda, Ichiro; Shibuya, Kengo; Yoshida, Eiji; Yamaya, Taiga; Kitamura, Keishi; Murayama, Hideo

    2010-01-01

    Avalanche photodiodes (APDs) are being used as photodetectors in positron emission tomography (PET) because they have many advantages over photomultipliers (PMTs) typically used in PET detectors. We have developed a PET detector that consists of a multi-pixel APD and a 6x6x4 array of 1.46x1.46 mm 2 x4.5 m LYSO crystals for a small animal PET scanner. The detector can identify four-layer depth of interaction (DOI) with a position-sensitive APD coupled to the backside of a crystal array by just an optimized reflector arrangement. Since scintillation lights are shared among many pixels by the method, weaker signals in APD pixels far from the interacting crystals are affected by noise. To evaluate the performance of the four-layer DOI detector with the APD and the influence of electrical noise on our method, we constructed a prototype DOI detector and tested its performance. We found, except for crystal elements on the edge of the crystal array, all crystal elements could be identified from the 2D position histogram. An energy resolution of 16.9% was obtained for the whole crystal array of the APD detector. The results of noise dependence of detector performances indicated that the DOI detector using the APD could achieve sufficient performance even when using application-specific integrated circuits.

  11. Scintillation counter with MRS APD light readout

    International Nuclear Information System (INIS)

    Akindinov, A.; Bondarenko, G.; Golovin, V.; Grigoriev, E.; Grishuk, Yu.; Mal'kevich, D.; Martemiyanov, A.; Ryabinin, M.; Smirnitskiy, A.; Voloshin, K.

    2005-01-01

    START, a high-efficiency and low-noise scintillation detector for ionizing particles, was developed for the purpose of creating a high-granular system for triggering cosmic muons. Scintillation light in START is detected by MRS APDs (Avalanche Photo-Diodes with Metal-Resistance-Semiconductor Structure), operated in the Geiger mode, which have 1mm 2 sensitive areas. START is assembled from a 15x15x1cm 3 scintillating plastic plate, two MRS APDs and two pieces of wavelength-shifting optical fiber stacked in circular coils inside the plastic. The front-end electronic card is mounted directly on the detector. Tests with START have confirmed its operational consistency, over 99% efficiency of MIP registration and good homogeneity. START demonstrates a low intrinsic noise of about 10 -2 Hz. If these detectors are to be mass-produced, the cost of a mosaic array of STARTs is estimated at a moderate level of 2-3kUSD/m 2

  12. Longitudinal density monitor for the LHC

    Science.gov (United States)

    Jeff, A.; Andersen, M.; Boccardi, A.; Bozyigit, S.; Bravin, E.; Lefevre, T.; Rabiller, A.; Roncarolo, F.; Welsch, C. P.; Fisher, A. S.

    2012-03-01

    The longitudinal density monitor (LDM) is primarily intended for the measurement of the particle population in nominally empty rf buckets. These so-called satellite or ghost bunches can cause problems for machine protection as well as influencing the luminosity calibration of the LHC. The high dynamic range of the system allows measurement of ghost bunches with as little as 0.01% of the main bunch population at the same time as characterization of the main bunches. The LDM is a single-photon counting system using visible synchrotron light. The photon detector is a silicon avalanche photodiode operated in Geiger mode, which allows the longitudinal distribution of the LHC beams to be measured with a resolution of 90 ps. Results from the LDM are presented, including a proposed method for constructing a 3-dimensional beam density map by scanning the LDM sensor in the transverse plane. In addition, we present a scheme to improve the sensitivity of the system by using an optical switching technique.

  13. The GAP-TPC

    International Nuclear Information System (INIS)

    Rossi, B.; Anastasio, A.; Boiano, A.; Cocco, A.G.; Meo, P. Di; Vanzanella, A.; Catalanotti, S.; Covone, G.; Longo, G.; Walker, S.; Fiorillo, G.; Wang, H.; Wang, Y.

    2016-01-01

    Several experiments have been conducted worldwide, with the goal of observing low-energy nuclear recoils induced by WIMPs scattering off target nuclei in ultra-sensitive, low-background detectors. In the last few decades noble liquid detectors designed to search for dark matter in the form of WIMPs have been extremely successful in improving their sensitivities and setting the best limits. One of the crucial problems to be faced for the development of large size (multi ton-scale) liquid argon experiments is the lack of reliable and low background cryogenic PMTs: their intrinsic radioactivity, cost, and borderline performance at 87 K rule them out as a possible candidate for photosensors. We propose a brand new concept of liquid argon-based detector for direct dark matter search: the Geiger-mode Avalanche Photodiode Time Projection Chamber (GAP-TPC) optimized in terms of residual radioactivity of the photosensors, energy and spatial resolution, light and charge collection efficiency

  14. 2D Dark-Count-Rate Modeling of PureB Single-Photon Avalanche Diodes in a TCAD Environment

    NARCIS (Netherlands)

    Knežević, Tihomir; Nanver, Lis K.; Suligoj, Tomislav; Witzigmann, Bernd; Osiński, Marek; Arakawa, Yasuhiko

    2018-01-01

    PureB silicon photodiodes have nm-shallow p+n junctions with which photons/electrons with penetration-depths of a few nanometer can be detected. PureB Single-Photon Avalanche Diodes (SPADs) were fabricated and analysed by 2D numerical modeling as an extension to TCAD software. The very shallow

  15. Single-Photon Avalanche Diode with Enhanced NIR-Sensitivity for Automotive LIDAR Systems.

    Science.gov (United States)

    Takai, Isamu; Matsubara, Hiroyuki; Soga, Mineki; Ohta, Mitsuhiko; Ogawa, Masaru; Yamashita, Tatsuya

    2016-03-30

    A single-photon avalanche diode (SPAD) with enhanced near-infrared (NIR) sensitivity has been developed, based on 0.18 μm CMOS technology, for use in future automotive light detection and ranging (LIDAR) systems. The newly proposed SPAD operating in Geiger mode achieves a high NIR photon detection efficiency (PDE) without compromising the fill factor (FF) and a low breakdown voltage of approximately 20.5 V. These properties are obtained by employing two custom layers that are designed to provide a full-depletion layer with a high electric field profile. Experimental evaluation of the proposed SPAD reveals an FF of 33.1% and a PDE of 19.4% at 870 nm, which is the laser wavelength of our LIDAR system. The dark count rate (DCR) measurements shows that DCR levels of the proposed SPAD have a small effect on the ranging performance, even if the worst DCR (12.7 kcps) SPAD among the test samples is used. Furthermore, with an eye toward vehicle installations, the DCR is measured over a wide temperature range of 25-132 °C. The ranging experiment demonstrates that target distances are successfully measured in the distance range of 50-180 cm.

  16. Evaluation of electrical crosstalk in high-density photodiode arrays for X-ray imaging applications

    International Nuclear Information System (INIS)

    Ji Fan; Juntunen, Mikko; Hietanen, Iiro

    2009-01-01

    Electrical crosstalk is one of the important parameters in the photodiode array detector for X-ray imaging applications, and it becomes more important when the density of the photodiode array becomes higher. This paper presents the design of the high-density photodiode array with 250 μm pitch and 50 μm gap. The electrical crosstalk of the demonstrated samples is evaluated and compared with different electrode configurations: cathode bias mode and anode bias mode. The measurement results show good electrical crosstalk, ∼0.23%, in cathode bias mode regardless of the bias voltage, and slightly decreased or increased electrical crosstalk in anode bias mode. Moreover, the quantum efficiency is also evaluated from the same samples, and it behaves similar to the electrical crosstalk. Finally, some design guidance of the high-density photodiode array is given based on the discussion.

  17. Large-area, low-noise, high-speed, photodiode-based fluorescence detectors with fast overdrive recovery

    International Nuclear Information System (INIS)

    Bickman, S.; DeMille, D.

    2005-01-01

    Two large-area, low-noise, high-speed fluorescence detectors have been built. One detector consists of a photodiode with an area of 28 mmx28 mm and a low-noise transimpedance amplifier. This detector has a input light-equivalent spectral noise density of less than 3 pW/√(Hz), can recover from a large scattered light pulse within 10 μs, and has a bandwidth of at least 900 kHz. The second detector consists of a 16-mm-diam avalanche photodiode and a low-noise transimpedance amplifier. This detector has an input light-equivalent spectral noise density of 0.08 pW/√(Hz), also can recover from a large scattered light pulse within 10 μs, and has a bandwidth of 1 MHz

  18. Stretched exponentials and power laws in granular avalanching

    Science.gov (United States)

    Head, D. A.; Rodgers, G. J.

    1999-02-01

    We introduce a model for granular surface flow which exhibits both stretched exponential and power law avalanching over its parameter range. Two modes of transport are incorporated, a rolling layer consisting of individual particles and the overdamped, sliding motion of particle clusters. The crossover in behaviour observed in experiments on piles of rice is attributed to a change in the dominant mode of transport. We predict that power law avalanching will be observed whenever surface flow is dominated by clustered motion.

  19. Current–voltage characteristics of high-voltage 4H-SiC p{sup +}–n{sub 0}–n{sup +} diodes in the avalanche breakdown mode

    Energy Technology Data Exchange (ETDEWEB)

    Ivanov, P. A., E-mail: Pavel.Ivanov@mail.ioffe.ru; Potapov, A. S.; Samsonova, T. P.; Grekhov, I. V. [Ioffe Physical–Technical Institute (Russian Federation)

    2017-03-15

    p{sup +}–n{sub 0}–n{sup +} 4H-SiC diodes with homogeneous avalanche breakdown at 1860 V are fabricated. The pulse current–voltage characteristics are measured in the avalanche-breakdown mode up to a current density of 4000 A/cm{sup 2}. It is shown that the avalanche-breakdown voltage increases with increasing temperature. The following diode parameters are determined: the avalanche resistance (8.6 × 10{sup –2} Ω cm{sup 2}), the electron drift velocity in the n{sub 0} base at electric fields higher than 10{sup 6} V/cm (7.8 × 10{sup 6} cm/s), and the relative temperature coefficient of the breakdown voltage (2.1 × 10{sup –4} K{sup –1}).

  20. An Inexpensive Coincidence Circuit for the Pasco Geiger Sensors

    CERN Document Server

    Fichera, F; Librizzi, F; Riggi, F

    2005-01-01

    A simple coincidence circuit was devised to carry out educational coincidence experiments involving the use of Geiger counters. The system was tested by commercially available Geiger sensors from PASCO, and is intended to be used in collaboration with high school students and teachers

  1. Single-Photon Avalanche Diode with Enhanced NIR-Sensitivity for Automotive LIDAR Systems

    Directory of Open Access Journals (Sweden)

    Isamu Takai

    2016-03-01

    Full Text Available A single-photon avalanche diode (SPAD with enhanced near-infrared (NIR sensitivity has been developed, based on 0.18 μm CMOS technology, for use in future automotive light detection and ranging (LIDAR systems. The newly proposed SPAD operating in Geiger mode achieves a high NIR photon detection efficiency (PDE without compromising the fill factor (FF and a low breakdown voltage of approximately 20.5 V. These properties are obtained by employing two custom layers that are designed to provide a full-depletion layer with a high electric field profile. Experimental evaluation of the proposed SPAD reveals an FF of 33.1% and a PDE of 19.4% at 870 nm, which is the laser wavelength of our LIDAR system. The dark count rate (DCR measurements shows that DCR levels of the proposed SPAD have a small effect on the ranging performance, even if the worst DCR (12.7 kcps SPAD among the test samples is used. Furthermore, with an eye toward vehicle installations, the DCR is measured over a wide temperature range of 25–132 °C. The ranging experiment demonstrates that target distances are successfully measured in the distance range of 50–180 cm.

  2. Development of a gamma dosimeter using a photodiode

    International Nuclear Information System (INIS)

    Melo, F.A. de.

    1988-05-01

    In the last years, the application of semiconductor detectors in radiation spectroscopy and dosimetry has increased. Silicon diodes have found utility in radiation dosimetry principally because a diode produces a current approximately 18000 times larger than of an ionization chamber of an equal sensitive volume. As the characteristics of the semiconductor detectors are the same as the common photodiode, a gamma dosimeter using this type of electronic component was developed. The photodiode SFH206 operating in photovoltaic mode was used. An electrometric unit was constructed to measure the current generated in this detector. The results obtained showed: the response of the photodiode was linear with the dose and that variation of 40 degrees in the incidence angle of the radiation caused a variation of 5% in the dose determination; the response reproducibility of the photodiode was studied, and the results showed that the variation coefficient is smaller than 0,02%; the small dimension of the silicon photodiode recommend its use as a gamma dosimeter for medical applications. (author). 19 refs, 32 figs, 1 tab

  3. Depth of interaction resolution measurements for a high resolution PET detector using position sensitive avalanche photodiodes

    International Nuclear Information System (INIS)

    Yang Yongfeng; Dokhale, Purushottam A; Silverman, Robert W; Shah, Kanai S; McClish, Mickel A; Farrell, Richard; Entine, Gerald; Cherry, Simon R

    2006-01-01

    We explore dual-ended read out of LSO arrays with two position sensitive avalanche photodiodes (PSAPDs) as a high resolution, high efficiency depth-encoding detector for PET applications. Flood histograms, energy resolution and depth of interaction (DOI) resolution were measured for unpolished LSO arrays with individual crystal sizes of 1.0, 1.3 and 1.5 mm, and for a polished LSO array with 1.3 mm pixels. The thickness of the crystal arrays was 20 mm. Good flood histograms were obtained for all four arrays, and crystals in all four arrays can be clearly resolved. Although the amplitude of each PSAPD signal decreases as the interaction depth moves further from the PSAPD, the sum of the two PSAPD signals is essentially constant with irradiation depth for all four arrays. The energy resolutions were similar for all four arrays, ranging from 14.7% to 15.4%. A DOI resolution of 3-4 mm (including the width of the irradiation band which is ∼2 mm) was obtained for all the unpolished arrays. The best DOI resolution was achieved with the unpolished 1 mm array (average 3.5 mm). The DOI resolution for the 1.3 mm and 1.5 mm unpolished arrays was 3.7 and 4.0 mm respectively. For the polished array, the DOI resolution was only 16.5 mm. Summing the DOI profiles across all crystals for the 1 mm array only degraded the DOI resolution from 3.5 mm to 3.9 mm, indicating that it may not be necessary to calibrate the DOI response separately for each crystal within an array. The DOI response of individual crystals in the array confirms this finding. These results provide a detailed characterization of the DOI response of these PSAPD-based PET detectors which will be important in the design and calibration of a PET scanner making use of this detector approach

  4. As the crack in the Geiger counter came. Historical scientific analysis and didactic aspects of the Geiger-Mueller counting tube

    International Nuclear Information System (INIS)

    Korff, Sebastian

    2014-01-01

    This thesis studies the creation and establishment history of this instrument called first electron counting tube in the years 1928 and 1929. It deals thereby with the last two years of the common work of Hans Geiger and Walter Mueller, from which the measuring instrument later renamed to Geiger-Mueller counting tube. The results of this scientific case study are didactically worked out and made usable for the teaching of physics in the school.

  5. Longitudinal density monitor for the LHC

    Directory of Open Access Journals (Sweden)

    A. Jeff

    2012-03-01

    Full Text Available The longitudinal density monitor (LDM is primarily intended for the measurement of the particle population in nominally empty rf buckets. These so-called satellite or ghost bunches can cause problems for machine protection as well as influencing the luminosity calibration of the LHC. The high dynamic range of the system allows measurement of ghost bunches with as little as 0.01% of the main bunch population at the same time as characterization of the main bunches. The LDM is a single-photon counting system using visible synchrotron light. The photon detector is a silicon avalanche photodiode operated in Geiger mode, which allows the longitudinal distribution of the LHC beams to be measured with a resolution of 90 ps. Results from the LDM are presented, including a proposed method for constructing a 3-dimensional beam density map by scanning the LDM sensor in the transverse plane. In addition, we present a scheme to improve the sensitivity of the system by using an optical switching technique.

  6. AX-PET A novel PET detector concept with full 3D reconstruction

    CERN Document Server

    Braem, A; Séguinot, J; Dissertori, G; Djambazov, L; Lustermann, W; Nessi-Tedaldi, F; Pauss, F; Schinzel, D; Solevi, P; Lacasta, C; Oliver, J F; Rafecas, M; De Leo, R; Nappi, E; Vilardi, I; Chesi, E; Cochran, E; Honscheid, K; Kagan, H; Rudge, A; Smith, S; Weilhammer, P; Johnson, I; Renker, D; Clinthorne, N; Huh, S; Bolle, E; Stapnes, S; Meddi, F

    2009-01-01

    We describe the concept and first experimental tests of a novel 3D axial Positron Emission Tomography (PET) geometry. It allows for a new way of measuring the interaction point in the detector with very high precision. It is based on a matrix of long Lutetium-Yttrium OxyorthoSilicate (LYSO) crystals oriented in the axial direction, each coupled to one Geiger Mode Avalanche Photodiode (G-APD) array. To derive the axial coordinate, Wave Length Shifter (WLS) strips are mounted orthogonally and interleaved between the crystals. The light from the WLS strips is read by custom-made G-APDs. The weighted mean of the signals in the WLS strips has proven to give very precise axial resolution. The achievable resolution along the three axes is mainly driven by the dimensions of the LYSO crystals and WLS strips. This concept is inherently free of parallax errors. Furthermore, it will allow identification of Compton interactions in the detector and for reconstruction of a fraction of them, which is expected to enhance imag...

  7. Parameters of the preproduction series SiPMs for the CMS HCAL phase I upgrade

    Energy Technology Data Exchange (ETDEWEB)

    Heering, A., E-mail: Adriaan.Heering@cern.ch [University of Notre Dame, Notre Dame, IN 46556 (United States); Musienko, Yu., E-mail: Iouri.Musienko@cern.ch [University of Notre Dame, Notre Dame, IN 46556 (United States); Institute for Nuclear Research RAS, pr. 60-letiya Oktyabrya 7a, 117312 Moscow (Russian Federation); Ruchti, R.; Wayne, M. [University of Notre Dame, Notre Dame, IN 46556 (United States); Karneyeu, A.; Postoev, V. [Institute for Nuclear Research RAS, pr. 60-letiya Oktyabrya 7a, 117312 Moscow (Russian Federation)

    2016-07-11

    In 2012 the HCAL SiPM photo sensor upgrade was approved for the increased luminosity (5*10{sup 34}) of SLHC. The upgrade will replace the current hybrid photodiodes (HPDs) with multi-pixel Geiger-mode avalanche photodiodes, also known as silicon photomultipliers (SiPMs). A key aspect of the upgrade to SiPMs is to add longitudinal segmentation and improve signal to noise to compensate for scintillator radiation damage. After 5 years of R&D with multiple companies we developed custom large dynamic range SiPMs with large PDE and small ENC. To ensure good mechanical alignment and easy handling of the large number of production channels (>20,000) we have developed a custom ceramic package with a very thin 0.3 mm quartz window with Kyocera. Each package holds 8 channels of SiPMs. Here we report on the final SiPM parameters of the 2014 preproduction run from Hamamatsu (HPK) who has produced a series of 175 arrays with a total of 1400 SiPMs. An overview of our QA results and measurements of the photon detection efficiency, spectral response, crosstalk and cell recovery time will be discussed. - Highlights: • Uniformity of large scale SiPM production. • Small cell size SiPMs with high photo detection efficiency. • Fast recovery time SiPMs. • Custom packaging of SiPMs in High Energy Physics experiments.

  8. High speed photodiodes in standard nanometer scale CMOS technology: a comparative study.

    Science.gov (United States)

    Nakhkoob, Behrooz; Ray, Sagar; Hella, Mona M

    2012-05-07

    This paper compares various techniques for improving the frequency response of silicon photodiodes fabricated in mainstream CMOS technology for fully integrated optical receivers. The three presented photodiodes, Spatially Modulated Light detectors, Double, and Interrupted P-Finger photodiodes, aim at reducing the low speed diffusive component of the photo generated current. For the first photodiode, Spatially Modulated Light (SML) detectors, the low speed current component is canceled out by converting it to a common mode current driving a differential transimpedance amplifier. The Double Photodiode (DP) uses two depletion regions to increase the fast drift component, while the Interrupted-P Finger Photodiode (IPFPD) redirects the low speed component towards a different contact from the main fast terminal of the photodiode. Extensive device simulations using 130 nm CMOS technology-parameters are presented to compare their performance using the same technological platform. Finally a new type of photodiode that uses triple well CMOS technology is introduced that can achieve a bandwidth of roughly 10 GHz without any process modification or high reverse bias voltages that would jeopardize the photodetector and subsequent transimpedance amplifier reliability.

  9. The Effect of Electron versus Hole Photocurrent on Optoelectric Properties of p+-p-n-n+ Wz-GaN Reach-Through Avalanche Photodiodes

    Directory of Open Access Journals (Sweden)

    Moumita Ghosh

    2013-01-01

    Full Text Available The authors have made an attempt to investigate the effect of electron versus hole photocurrent on the optoelectric properties of p+-p-n-n+ structured Wurtzite-GaN (Wz-GaN reach-through avalanche photodiodes (RAPDs. The photo responsivity and optical gain of the devices are obtained within the wavelength range of 300 to 450 nm using a novel modeling and simulation technique developed by the authors. Two optical illumination configurations of the device such as Top Mounted (TM and Flip Chip (FC are considered for the present study to investigate the optoelectric performance of the device separately due to electron dominated and hole dominated photocurrents, respectively, in the visible-blind ultraviolet (UV spectrum. The results show that the peak unity gain responsivity and corresponding optical gain of the device are 555.78 mA W−1 and 9.4144×103, respectively, due to hole dominated photocurrent (i.e., in FC structure; while those are 480.56 mA W−1 and 7.8800×103, respectively, due to electron dominated photocurrent (i.e., in TM structure at the wavelength of 365 nm and for applied reverse bias of 85 V. Thus, better optoelectric performance of Wz-GaN RAPDs can be achieved when the photocurrent is made hole dominated by allowing the UV light to be shined on the n+-layer instead of p+-layer of the device.

  10. As the crack in the Geiger counter came. Historical scientific analysis and didactic aspects of the Geiger-Mueller counting tube; Wie das Knacken in den Geigerzaehler kam. Wissenschaftshistorische Analyse und fachdidaktische Aspekte des Geiger-Mueller Zaehlrohrs

    Energy Technology Data Exchange (ETDEWEB)

    Korff, Sebastian

    2014-11-10

    This thesis studies the creation and establishment history of this instrument called first electron counting tube in the years 1928 and 1929. It deals thereby with the last two years of the common work of Hans Geiger and Walter Mueller, from which the measuring instrument later renamed to Geiger-Mueller counting tube. The results of this scientific case study are didactically worked out and made usable for the teaching of physics in the school.

  11. Dynamic avalanche behavior of power MOSFETs and IGBTs under unclamped inductive switching conditions

    International Nuclear Information System (INIS)

    Lu Jiang; Tian Xiaoli; Lu Shuojin; Zhou Hongyu; Zhu Yangjun; Han Zhengsheng

    2013-01-01

    The ability of high-voltage power MOSFETs and IGBTs to withstand avalanche events under unclamped inductive switching (UIS) conditions is measured. This measurement is to investigate and compare the dynamic avalanche failure behavior of the power MOSFETs and the IGBT, which occur at different current conditions. The UIS measurement results at different current conditions show that the main failure reason of the power MOSFETs is related to the parasitic bipolar transistor, which leads to the deterioration of the avalanche reliability of power MOSFETs. However, the results of the IGBT show two different failure behaviors. At high current mode, the failure behavior is similar to the power MOSFETs situation. But at low current mode, the main failure mechanism is related to the parasitic thyristor activity during the occurrence of the avalanche process and which is in good agreement with the experiment result. (semiconductor devices)

  12. Avalanche weak layer shear fracture parameters from the cohesive crack model

    Science.gov (United States)

    McClung, David

    2014-05-01

    Dry slab avalanches release by mode II shear fracture within thin weak layers under cohesive snow slabs. The important fracture parameters include: nominal shear strength, mode II fracture toughness and mode II fracture energy. Alpine snow is not an elastic material unless the rate of deformation is very high. For natural avalanche release, it would not be possible that the fracture parameters can be considered as from classical fracture mechanics from an elastic framework. The strong rate dependence of alpine snow implies that it is a quasi-brittle material (Bažant et al., 2003) with an important size effect on nominal shear strength. Further, the rate of deformation for release of an avalanche is unknown, so it is not possible to calculate the fracture parameters for avalanche release from any model which requires the effective elastic modulus. The cohesive crack model does not require the modulus to be known to estimate the fracture energy. In this paper, the cohesive crack model was used to calculate the mode II fracture energy as a function of a brittleness number and nominal shear strength values calculated from slab avalanche fracture line data (60 with natural triggers; 191 with a mix of triggers). The brittleness number models the ratio of the approximate peak value of shear strength to nominal shear strength. A high brittleness number (> 10) represents large size relative to fracture process zone (FPZ) size and the implications of LEFM (Linear Elastic Fracture Mechanics). A low brittleness number (e.g. 0.1) represents small sample size and primarily plastic response. An intermediate value (e.g. 5) implies non-linear fracture mechanics with intermediate relative size. The calculations also implied effective values for the modulus and the critical shear fracture toughness as functions of the brittleness number. The results showed that the effective mode II fracture energy may vary by two orders of magnitude for alpine snow with median values ranging from 0

  13. Updated world map of the Köppen-Geiger climate classification

    Directory of Open Access Journals (Sweden)

    M. C. Peel

    2007-10-01

    Full Text Available Although now over 100 years old, the classification of climate originally formulated by Wladimir Köppen and modified by his collaborators and successors, is still in widespread use. It is widely used in teaching school and undergraduate courses on climate. It is also still in regular use by researchers across a range of disciplines as a basis for climatic regionalisation of variables and for assessing the output of global climate models. Here we have produced a new global map of climate using the Köppen-Geiger system based on a large global data set of long-term monthly precipitation and temperature station time series. Climatic variables used in the Köppen-Geiger system were calculated at each station and interpolated between stations using a two-dimensional (latitude and longitude thin-plate spline with tension onto a 0.1°×0.1° grid for each continent. We discuss some problems in dealing with sites that are not uniquely classified into one climate type by the Köppen-Geiger system and assess the outcomes on a continent by continent basis. Globally the most common climate type by land area is BWh (14.2%, Hot desert followed by Aw (11.5%, Tropical savannah. The updated world Köppen-Geiger climate map is freely available electronically in the Supplementary Material Section.

  14. Automation and instrument control applied to an experimental study of electron transport dynamics in an avalanche mode resistive plater chamber

    International Nuclear Information System (INIS)

    Ridenti, Marco A.; Pascholati, Paulo R.

    2009-01-01

    In this work it is presented a computer based instrumentation system which was developed to perform data acquisition and integrate the control of different devices in an experimental study of electron transport dynamics in an avalanche mode resistive plate chamber detector in the Radiation Technology Center (CTR) at IPEN/CNEN-SP. System control and data acquisition was performed by a computer program called RPCLabOperator written in MatLab environment running on a LeCroy WavePro 7000 digital oscilloscope. (author)

  15. STUDY ON SIMULATION METHOD OF AVALANCHE : FLOW ANALYSIS OF AVALANCHE USING PARTICLE METHOD

    OpenAIRE

    塩澤, 孝哉

    2015-01-01

    In this paper, modeling for the simulation of the avalanche by a particle method is discussed. There are two kinds of the snow avalanches, one is the surface avalanche which shows a smoke-like flow, and another is the total-layer avalanche which shows a flow like Bingham fluid. In the simulation of the surface avalanche, the particle method in consideration of a rotation resistance model is used. The particle method by Bingham fluid is used in the simulation of the total-layer avalanche. At t...

  16. Statistical analysis of natural radiation levels inside the UNICAMP campus through the use of Geiger-Muller counter; Analise estatistica dos niveis de radiacao natural dentro da UNICAMP atraves do uso de contador Geiger-Muller

    Energy Technology Data Exchange (ETDEWEB)

    Fontolan, Juliana A.; Biral, Antonio Renato P., E-mail: fontolanjuliana@gmail.com.br, E-mail: biral@ceb.unicamp.br [Hospital das Clinicas (CEB/UNICAMP), Campinas, SP (Brazil). Centro de Engenharia Biomedica

    2013-07-01

    It is known that the distribution at time intervals of random and unrelated events leads to the Poisson distribution . This work aims to study the distribution in time intervals of events resulting from radioactive decay of atoms present in the UNICAMP where activities involving the use of ionizing radiation are performed environments . The proposal is that the distribution surveys at intervals of these events in different locations of the university are carried out through the use of a Geiger-Mueller tube . In a next step , the evaluation of distributions obtained by using non- parametric statistics (Chi- square and Kolmogorov Smirnoff) will be taken . For analyzes involving correlations we intend to use the ANOVA (Analysis of Variance) statistical tool . Measured in six different places within the Campinas , with the use of Geiger- Muller its count mode and a time window of 20 seconds was performed . Through statistical tools chi- square and Kolmogorov Smirnoff tests, using the EXCEL program , it was observed that the distributions actually refer to a Poisson distribution. Finally, the next step is to perform analyzes involving correlations using the statistical tool ANOVA.

  17. Multi-Layer Organic Squaraine-Based Photodiode for Indirect X-Ray Detection

    Science.gov (United States)

    Iacchetti, Antonio; Binda, Maddalena; Natali, Dario; Giussani, Mattia; Beverina, Luca; Fiorini, Carlo; Peloso, Roberta; Sampietro, Marco

    2012-10-01

    The paper presents an organic-based photodiode coupled to a CsI(Tl) scintillator to realize an X-ray detector. A suitable blend of an indolic squaraine derivative and of fullerene derivative has been used for the photodiode, thus allowing external quantum efficiency in excess of 10% at a wavelength of 570 nm, well matching the scintillator output spectrum. Thanks to the additional deposition of a 15 nm thin layer of a suitable low electron affinity polymer, carriers injection from the metal into the organic semiconductor has been suppressed, and dark current density as low as has been obtained, which is comparable to standard Si-based photodiodes. By using a collimated X-ray beam impinging onto the scintillator mounted over the photodiode we have been able to measure current variations in the order of 150 pA on a dark current floor of less than 50 pA when operating the X-ray tube in switching mode, thus proving the feasibility of indirect X-ray detection by means of organic semiconductors.

  18. SWIR HgCdTe avalanche photiode focal plane array performances evaluation

    Science.gov (United States)

    de Borniol, E.; Rothman, J.; Salveti, F.; Feautrier, P.

    2017-11-01

    One of the main challenges of modern astronomical instruments like adaptive optics (AO) systems or fringe trackers is to deal with the very low photons flux detection scenarios. The typical timescale of atmospheric turbulences being in the range of some tens of milliseconds, infrared wavefront sensors for AO systems needs frame rates higher than 1 KHz leading to integration times lower than 1 ms. This integration time associated with a low irradiance results in a few number of integrated photons per frame per pixel. To preserve the information coming from this weak signal, the focal plane array (FPA) has to present a low read out noise, a high quantum efficiency and a low dark current. Up to now, the output noise of high speed near infrared sensors is limited by the silicon read out circuit noise. The use of HgCdTe avalanche photodiodes with high gain at moderate reverse bias and low excess noise seems then a logical way to reduce the impact of the read noise on images signal to noise ratio. These low irradiance passive imaging applications with integration times in the millisecond range needs low photodiode dark current and low background current. These requirements lead to the choice of the photodiode cut off wavelength. The short wave infrared (SWIR) around 3 μm is a good compromise between the gain that can be obtain for a given APD bias and the background and dark current. The CEA LETI HgCdTe APD technology, and a fine analysis of the gain curve characteristic are presented in [1] and won't be detailed here. The response time of the APD is also a key factor for a high frame rate FPA. This parameter has been evaluated in [2] and the results shows cut off frequencies in the GHz range. In this communication we report the performances of a SWIR APD FPA designed and fabricated by CEA LETI and SOFRADIR for astrophysical applications. This development was made in the frame of RAPID, a 4 years R&D project funded by the French FUI (Fond Unique Interministériel). This

  19. Relating rock avalanche morphology to emplacement processes

    Science.gov (United States)

    Dufresne, Anja; Prager, Christoph; Bösmeier, Annette

    2015-04-01

    /limestone sequences to weaker siliciclastic and evaporitic beds (sand-/siltstones, rauhwacken) can be pinpointed on LiDAR shaded relief images of the rock avalanche deposit. Hence, several morphological signatures are clearly related to differences in mechanical behaviour of the involved lithologies, whereas others reflect particular emplacement modes of the same rock unit: e.g. rockslide motion versus rock avalanche spreading. Reference Patzelt G. 2012. The rock avalanches of Tschirgant and Haiming (Upper Inn Valley, Tyrol, Austria), comment on the map supply. (German language only). Jahrbuch der Geologischen Bundesanstalt 152(1-4): 13-24.

  20. Nanomechanics of slip avalanches in amorphous plasticity

    Science.gov (United States)

    Cao, Penghui; Dahmen, Karin A.; Kushima, Akihiro; Wright, Wendelin J.; Park, Harold S.; Short, Michael P.; Yip, Sidney

    2018-05-01

    Discrete stress relaxations (slip avalanches) in a model metallic glass under uniaxial compression are studied using a metadynamics algorithm for molecular simulation at experimental strain rates. The onset of yielding is observed at the first major stress drop, accompanied, upon analysis, by the formation of a single localized shear band region spanning the entire system. During the elastic response prior to yielding, low concentrations of shear transformation deformation events appear intermittently and spatially uncorrelated. During serrated flow following yielding, small stress drops occur interspersed between large drops. The simulation results point to a threshold value of stress dissipation as a characteristic feature separating major and minor avalanches consistent with mean-field modeling analysis and mechanical testing experiments. We further interpret this behavior to be a consequence of a nonlinear interplay of two prevailing mechanisms of amorphous plasticity, thermally activated atomic diffusion and stress-induced shear transformations, originally proposed by Spaepen and Argon, respectively. Probing the atomistic processes at widely separate strain rates gives insight to different modes of shear band formation: percolation of shear transformations versus crack-like propagation. Additionally a focus on crossover avalanche size has implications for nanomechanical modeling of spatially and temporally heterogeneous dynamics.

  1. SiPM based readout system for PbWO4 crystals

    Science.gov (United States)

    Berra, A.; Bolognini, D.; Bonfanti, S.; Bonvicini, V.; Lietti, D.; Penzo, A.; Prest, M.; Stoppani, L.; Vallazza, E.

    2013-08-01

    Silicon PhotoMultipliers (SiPMs) consist of a matrix of small passively quenched silicon avalanche photodiodes operated in limited Geiger-mode (GM-APDs) and read out in parallel from a common output node. Each pixel (with a typical size in the 20-100 μm range) gives the same current response when hit by a photon; the SiPM output signal is the sum of the signals of all the pixels, which depends on the light intensity. The main advantages of SiPMs with respect to photomultiplier tubes (PMTs) are essentially the small dimensions, the insensitivity to magnetic fields and a low bias voltage. This contribution presents the performance of a SiPM based readout system for crystal calorimeters developed in the framework of the FACTOR/TWICE collaboration. The SiPM used for the test is a new device produced by FBK-irst which consists in a matrix of four sensors embedded in the same silicon substrate, called QUAD. The SiPM has been coupled to a lead tungstate crystal, an early-prototype version of the crystals developed for the electromagnetic calorimeter of the CMS experiment. New tests are foreseen using a complete module consisting of nine crystals, each one readout by two QUADs.

  2. SiPM based readout system for PbWO4 crystals

    International Nuclear Information System (INIS)

    Berra, A.; Bolognini, D.; Bonfanti, S.; Bonvicini, V.; Lietti, D.; Penzo, A.; Prest, M.; Stoppani, L.; Vallazza, E.

    2013-01-01

    Silicon PhotoMultipliers (SiPMs) consist of a matrix of small passively quenched silicon avalanche photodiodes operated in limited Geiger-mode (GM-APDs) and read out in parallel from a common output node. Each pixel (with a typical size in the 20–100 μm range) gives the same current response when hit by a photon; the SiPM output signal is the sum of the signals of all the pixels, which depends on the light intensity. The main advantages of SiPMs with respect to photomultiplier tubes (PMTs) are essentially the small dimensions, the insensitivity to magnetic fields and a low bias voltage. This contribution presents the performance of a SiPM based readout system for crystal calorimeters developed in the framework of the FACTOR/TWICE collaboration. The SiPM used for the test is a new device produced by FBK-irst which consists in a matrix of four sensors embedded in the same silicon substrate, called QUAD. The SiPM has been coupled to a lead tungstate crystal, an early-prototype version of the crystals developed for the electromagnetic calorimeter of the CMS experiment. New tests are foreseen using a complete module consisting of nine crystals, each one readout by two QUADs

  3. SiPM based readout system for PbWO{sub 4} crystals

    Energy Technology Data Exchange (ETDEWEB)

    Berra, A., E-mail: alessandro.berra@gmail.com [Università degli Studi dell' Insubria e INFN sezione di Milano Bicocca, Via Valleggio, 11-22100 Como (Italy); Bolognini, D.; Bonfanti, S. [Università degli Studi dell' Insubria e INFN sezione di Milano Bicocca, Via Valleggio, 11-22100 Como (Italy); Bonvicini, V. [INFN sezione di Trieste (Italy); Lietti, D. [Università degli Studi dell' Insubria e INFN sezione di Milano Bicocca, Via Valleggio, 11-22100 Como (Italy); Penzo, A. [INFN sezione di Trieste (Italy); Prest, M.; Stoppani, L. [Università degli Studi dell' Insubria e INFN sezione di Milano Bicocca, Via Valleggio, 11-22100 Como (Italy); Vallazza, E. [INFN sezione di Trieste (Italy)

    2013-08-01

    Silicon PhotoMultipliers (SiPMs) consist of a matrix of small passively quenched silicon avalanche photodiodes operated in limited Geiger-mode (GM-APDs) and read out in parallel from a common output node. Each pixel (with a typical size in the 20–100 μm range) gives the same current response when hit by a photon; the SiPM output signal is the sum of the signals of all the pixels, which depends on the light intensity. The main advantages of SiPMs with respect to photomultiplier tubes (PMTs) are essentially the small dimensions, the insensitivity to magnetic fields and a low bias voltage. This contribution presents the performance of a SiPM based readout system for crystal calorimeters developed in the framework of the FACTOR/TWICE collaboration. The SiPM used for the test is a new device produced by FBK-irst which consists in a matrix of four sensors embedded in the same silicon substrate, called QUAD. The SiPM has been coupled to a lead tungstate crystal, an early-prototype version of the crystals developed for the electromagnetic calorimeter of the CMS experiment. New tests are foreseen using a complete module consisting of nine crystals, each one readout by two QUADs.

  4. Simulation of Silicon Photomultiplier Signals

    Science.gov (United States)

    Seifert, Stefan; van Dam, Herman T.; Huizenga, Jan; Vinke, Ruud; Dendooven, Peter; Lohner, Herbert; Schaart, Dennis R.

    2009-12-01

    In a silicon photomultiplier (SiPM), also referred to as multi-pixel photon counter (MPPC), many Geiger-mode avalanche photodiodes (GM-APDs) are connected in parallel so as to combine the photon counting capabilities of each of these so-called microcells into a proportional light sensor. The discharge of a single microcell is relatively well understood and electronic models exist to simulate this process. In this paper we introduce an extended model that is able to simulate the simultaneous discharge of multiple cells. This model is used to predict the SiPM signal in response to fast light pulses as a function of the number of fired cells, taking into account the influence of the input impedance of the SiPM preamplifier. The model predicts that the electronic signal is not proportional to the number of fired cells if the preamplifier input impedance is not zero. This effect becomes more important for SiPMs with lower parasitic capacitance (which otherwise is a favorable property). The model is validated by comparing its predictions to experimental data obtained with two different SiPMs (Hamamatsu S10362-11-25u and Hamamatsu S10362-33-25c) illuminated with ps laser pulses. The experimental results are in good agreement with the model predictions.

  5. SiPM as photon counter for Cherenkov detectors

    International Nuclear Information System (INIS)

    Roy, B.J.; Orth, H.; Schwarz, C.; Wilms, A.; Peters, K.

    2009-01-01

    Silicon photomultipliers (SiPMs) are very new type of photon counting devices that show great promise to be used as detection device in combination with scintillators/ Cherenkov radiators. SiPM is essentially an avalanche photo-diode operated in limited Geiger mode. They have been considered as potential readout devices for DIRC counter of the PANDA detector which is one of the large experiment at FAIR- the new international facility to be built at GSI, Darmstadt. In addition, the potential use of SiPM includes medical diagnosis, fluorescence measurement and high energy physics experiments. The SiPM module is a photon counting device capable of low light level detection. It is essentially an opto-semiconductor device with excellent photon counting capability and possesses great advantages over the conventional PMTs because of low voltage operation and insensitivity to magnetic fields. In many of the high energy physics experiments, the photon sensors are required to operate in high magnetic fields precluding the use of conventional PMTs. This problem can be over come with the use of SiPMs. With this motivation in mind, we have developed a SiPM test facility and have tested several commercially available SiPM for their performance study and comparison with other photon counting devices

  6. A low-noise, wideband, integrated CMOS transimpedance preamplifier for photodiode applications

    International Nuclear Information System (INIS)

    Binkley, D.M.; Paulus, M.J.; Casey, M.E.; Rochelle, J.M.

    1992-01-01

    In this paper, a low-noise, wideband, integrated CMOS transimpedance preamplifier is presented for silicon avalanche photodiode (APD) applications. The preamplifier, fabricated in a standard 2μ CMOS technology, features a transimpedance gain of 45 kΩ, a risetime of 22 ns, a series noise of 1.6nV/Hz 1/2 , and a wideband equivalent input-noise current of 12 nA for a source capacitance of 12 pF. The measured 22 Na timing resolution of 9.2-ns FWHM and energy resolution of 22.4% FWHM for the RCA C30994 BGO/APD detector module coupled to the preamplifier is comparable to the performance reported using charge-sensitive preamplifiers. This illustrates that transimpedance preamplifiers should be considered for APD applications, especially where APD noise current dominates noise from feedback resistors in the 1--kΩ to 50-kΩ range

  7. Room-temperature broadband InAsSb flip-chip photodiodes with λcutoff = 4.5 μm

    International Nuclear Information System (INIS)

    Zakhgeim, A. L.; Zotova, N. V.; Il'inskaya, N. D.; Karandashev, S. A.; Matveev, B. A.; Remennyi, M. A.; Stus', N. M.; Chernyakov, A. E.

    2009-01-01

    Equilibrium and nonequilibrium IR images of p-InAsSbP/n-InAsSb/n + -InAs photodiodes including the images obtained in the electroluminescence and negative luminescence modes have been analyzed. The contact reflectivity has been evaluated. The influence of the substrate's doping level and mesa depth on the quantum efficiency and sensitivity of a backside illuminated photodiode sensitive in the 2.7-4.5 μm range is discussed.

  8. Statistical analysis of natural radiation levels inside the UNICAMP campus through the use of Geiger-Muller counter

    International Nuclear Information System (INIS)

    Fontolan, Juliana A.; Biral, Antonio Renato P.

    2013-01-01

    It is known that the distribution at time intervals of random and unrelated events leads to the Poisson distribution . This work aims to study the distribution in time intervals of events resulting from radioactive decay of atoms present in the UNICAMP where activities involving the use of ionizing radiation are performed environments . The proposal is that the distribution surveys at intervals of these events in different locations of the university are carried out through the use of a Geiger-Mueller tube . In a next step , the evaluation of distributions obtained by using non- parametric statistics (Chi- square and Kolmogorov Smirnoff) will be taken . For analyzes involving correlations we intend to use the ANOVA (Analysis of Variance) statistical tool . Measured in six different places within the Campinas , with the use of Geiger- Muller its count mode and a time window of 20 seconds was performed . Through statistical tools chi- square and Kolmogorov Smirnoff tests, using the EXCEL program , it was observed that the distributions actually refer to a Poisson distribution. Finally, the next step is to perform analyzes involving correlations using the statistical tool ANOVA

  9. The simulation of resistive plate chambers in avalanche mode: charge spectra and efficiency

    Energy Technology Data Exchange (ETDEWEB)

    Abbrescia, M. E-mail: Marcello.abbrescia@ba.infn.it; Colaleo, A.; Iaselli, G.; Loddo, F.; Maggi, M.; Marangelli, B.; Natali, S.; Nuzzo, S.; Pugliese, G.; Ranieri, A.; Romano, F.; Altieri, S.; Bruno, G.; Gianini, G.; Ratti, S.P.; Viola, L.; Vitulo, P

    1999-07-21

    A model to simulate the avalanche formation process and the induced signal in a Resistive Plate Chamber is presented. A first investigation of the effects of various parameters on the performance of this detector is reported. (author)

  10. Geiger counters of gamma rays with a bismuth cathode; Compteurs de geiger a rayons gamma a cathode de bismuth

    Energy Technology Data Exchange (ETDEWEB)

    Meunier, R; Legrand, J P [Commissariat a l' Energie Atomique, Saclay(France). Centre d' Etudes Nucleaires

    1953-07-01

    Geiger Muller counters present a lake of efficiency of some per cent, for the {gamma} radiations. In the region 0,3 - 1 MeV, a substantial growth of their output can be obtained by a special construction of their cathode. In accordance with previous works, we constructed some counter of formed cathode by a pleated copper wire fencing covered of Bi by electrolysis. The successive modifications brought to a cylindrical conventional cathode in sheet metal of copper, that succeeds to this type of cathode, drive to an improvement of the output. (M.B.) [French] Les compteurs de Geiger Muller presentent une efficacite assez faible de l'ordre de quelques pour cent, pour les rayonnements {gamma}. Dans la region 0,3 - 1 MeV, un accroissement substantiel de leur rendement peut etre obtenu par une construction speciale de leur cathode. Conformement a des travaux anterieurs, nous avons construit des compteurs a cathode formee par un grillage de cuivre plisse recouvert de Bi par electrolyse. Les modifications successives apportees a une cathode conventionnelle cylindrique en tole de cuivre, qui aboutissent a ce type de cathode, conduisent a une amelioration du rendement. (M.B.)

  11. Quantum random number generator based on quantum tunneling effect

    OpenAIRE

    Zhou, Haihan; Li, Junlin; Pan, Dong; Zhang, Weixing; Long, Guilu

    2017-01-01

    In this paper, we proposed an experimental implementation of quantum random number generator(QRNG) with inherent randomness of quantum tunneling effect of electrons. We exploited InGaAs/InP diodes, whose valance band and conduction band shared a quasi-constant energy barrier. We applied a bias voltage on the InGaAs/InP avalanche diode, which made the diode works under Geiger mode, and triggered the tunneling events with a periodic pulse. Finally, after data collection and post-processing, our...

  12. High-Gain Avalanche Rushing amorphous Photoconductor (HARP) detector

    Energy Technology Data Exchange (ETDEWEB)

    Tanioka, K. [NHK Science and Technical Research Laboratories, 1-10-11 Kinuta, Setagaya-ku, Tokyo 157-8510 (Japan)], E-mail: tanioka.k-jg@nhk.or.jp

    2009-09-01

    We have been studying a very sensitive image sensor since the early 1980s. In 1985, the author found for the first time that an experimental pickup tube with an amorphous selenium photoconductive target exhibits high sensitivity with excellent picture quality because of a continuous and stable avalanche multiplication phenomenon. We named the pickup tube with an amorphous photoconductive layer operating in the avalanche-mode 'HARP': High-gain Avalanche Rushing amorphous Photoconductor. A color camera equipped with the HARP pickup tubes has a maximum sensitivity of 11 lx at F8. This means that the HARP camera is about 100 times as sensitive as that of CCD camera for broadcasting. This ultrahigh-sensitivity HARP pickup tube is a powerful tool for reporting breaking news at night and other low-light conditions, the production of scientific programs, and numerous other applications, including medical diagnoses, biotech research, and nighttime surveillance. In addition, since the HARP target can convert X-rays into electrons directly, it should be possible to exploit this capability to produce X-ray imaging devices with unparalleled levels of resolution and sensitivity.

  13. An amorphous silicon photodiode with 2 THz gain-bandwidth product based on cycling excitation process

    Science.gov (United States)

    Yan, Lujiang; Yu, Yugang; Zhang, Alex Ce; Hall, David; Niaz, Iftikhar Ahmad; Raihan Miah, Mohammad Abu; Liu, Yu-Hsin; Lo, Yu-Hwa

    2017-09-01

    Since impact ionization was observed in semiconductors over half a century ago, avalanche photodiodes (APDs) using impact ionization in a fashion of chain reaction have been the most sensitive semiconductor photodetectors. However, APDs have relatively high excess noise, a limited gain-bandwidth product, and high operation voltage, presenting a need for alternative signal amplification mechanisms of superior properties. As an amplification mechanism, the cycling excitation process (CEP) was recently reported in a silicon p-n junction with subtle control and balance of the impurity levels and profiles. Realizing that CEP effect depends on Auger excitation involving localized states, we made the counter intuitive hypothesis that disordered materials, such as amorphous silicon, with their abundant localized states, can produce strong CEP effects with high gain and speed at low noise, despite their extremely low mobility and large number of defects. Here, we demonstrate an amorphous silicon low noise photodiode with gain-bandwidth product of over 2 THz, based on a very simple structure. This work will impact a wide range of applications involving optical detection because amorphous silicon, as the primary gain medium, is a low-cost, easy-to-process material that can be formed on many kinds of rigid or flexible substrates.

  14. Room-temperature broadband InAsSb flip-chip photodiodes with {lambda}{sub cutoff} = 4.5 {mu}m

    Energy Technology Data Exchange (ETDEWEB)

    Zakhgeim, A L [Russian Academy of Sciences, Scientific-Technological Center for Microelectronics and Submicron Heterostructures at Ioffe Physicotechnical Institute (Russian Federation); Zotova, N V; Il' inskaya, N D; Karandashev, S A; Matveev, B. A., E-mail: bmat@iropt3.ioffe.rssi.ru; Remennyi, M A; Stus' , N M [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation); Chernyakov, A E [Russian Academy of Sciences, Scientific-Technological Center for Microelectronics and Submicron Heterostructures at Ioffe Physicotechnical Institute (Russian Federation)

    2009-03-15

    Equilibrium and nonequilibrium IR images of p-InAsSbP/n-InAsSb/n{sup +}-InAs photodiodes including the images obtained in the electroluminescence and negative luminescence modes have been analyzed. The contact reflectivity has been evaluated. The influence of the substrate's doping level and mesa depth on the quantum efficiency and sensitivity of a backside illuminated photodiode sensitive in the 2.7-4.5 {mu}m range is discussed.

  15. Avalanche hazard and control in Kazakhstan

    Directory of Open Access Journals (Sweden)

    V. P. Blagoveshchensky

    2014-01-01

    Full Text Available In Kazakhstan, area of 124 thousand km2 is prone to the avalanche hazard. Avalanches are released down in mountain regions situated along the eastern boundary of Kazakhstan. Systematic studies of avalanches here were started in 1958 by explorer I.S. Sosedov; later on, I.V. Seversky continued these investigations in Institute of Geography of the Kazakh Soviet Republic. Actually, he founded the Kazakh school of the avalanche studies. In 1970–1980s, five snow-avalanche stations operated in Kazakhstan: two in Il’ Alatau, two in Zhetysu Alatau, and one in the Altai. At the present time, only two stations and two snow-avalanche posts operate, and all of them are located in Il’ Alatau.Since 1951 to 2013, 75 avalanches took place in Kazakhstan, releases of them caused significant damages. For this period 172 people happened to be under avalanches, among them 86 perished. Large avalanche catastrophes causing human victims and destructions took place in Altai in 1977 and in Karatau in 1990. In spring of 1966, only in Il’ Alatau avalanches destroyed more 600 ha of mature fir (coniferous forest, and the total area of forest destroyed here by avalanches amounts to 2677 ha or 7% of the total forest area.For 48 years of the avalanche observations, there were 15 winters with increased avalanche activity in the river Almatinka basin when total volume of released snow exceeded annual mean value of 147 thousand m3. During this period, number of days with winter avalanches changed from three (in season of 1973/1974 to 28 (1986/1987, the average for a year is 16 days for a season. Winter with the total volume of snow 1300 thousand m3 occur once in 150 years. Individual avalanches with maximal volume of 350 thousand m3 happen once in 80 years.Preventive avalanche releases aimed at protection of roads and settlements are used in Kazakhstan since 1974. These precautions are taken in Il’ Alatau, Altai, and on Kalbinsky Range. Avalanches are released with the

  16. Development of a gamma dosimeter using a photodiode; Desenvolvimento de um dosimetro para radiacao gama utilizando fotodiodo

    Energy Technology Data Exchange (ETDEWEB)

    Melo, F.A. de

    1988-05-01

    In the last years, the application of semiconductor detectors in radiation spectroscopy and dosimetry has increased. Silicon diodes have found utility in radiation dosimetry principally because a diode produces a current approximately 18000 times larger than of an ionization chamber of an equal sensitive volume. As the characteristics of the semiconductor detectors are the same as the common photodiode, a gamma dosimeter using this type of electronic component was developed. The photodiode SFH206 operating in photovoltaic mode was used. An electrometric unit was constructed to measure the current generated in this detector. The results obtained showed: the response of the photodiode was linear with the dose and that variation of 40 degrees in the incidence angle of the radiation caused a variation of 5% in the dose determination; the response reproducibility of the photodiode was studied, and the results showed that the variation coefficient is smaller than 0,02%; the small dimension of the silicon photodiode recommend its use as a gamma dosimeter for medical applications. (author). 19 refs, 32 figs, 1 tab.

  17. Geiger-Mueller counter for mixed neutron-gamma beam dosimetry

    International Nuclear Information System (INIS)

    McDonald, J.C.; Ma, I.-C.

    1978-01-01

    A Geiger-Mueller (G-M) dosimeter has been constructed and employed to measure the gamma-ray component of absorbed dose in a cyclotron produced fast neutron field. This instrument is waterproof for measurements in a liquid medium, and read-out is accompanied with any standard scaler. (Auth.)

  18. Geiger-Muller with a mica window halogen quenched counters aspects

    International Nuclear Information System (INIS)

    Gorski, M.S.; Bruzinga, W.A.

    1990-09-01

    We present the development of a model of a Geiger-Muller with likeness the model ZP 1410 Phillips. The prototype has a cylindrical shape with 37mm of effective length and a mica window of 1,5 to 2,0mg/cm sup(2) thickness with a useful diam of 19,8mm. For the window preparation and special cutting technique was developed Basically two types of quenching agents, bromine and chlorine were studied. Due to the high corrosive nature of these gases, we work with treatment of surface of the cathode through electropolishment, chemical passiveness, hard chrome and nickel coating. Out main objective was to get a Geiger-Muller detector with an operational plateau over 200V, working voltage above 600V and a sensivity of 320 counts/sec at 10 sup(-1) m Gy/h. (author)

  19. Geiger-Muller (GM) counters. Associated circuits and counting techniques; Les compteurs de Geiger-Muller (GM). Les circuits associes et techniques de comptage

    Energy Technology Data Exchange (ETDEWEB)

    Benoit, A.; Picard, E. [Commissariat a l' Energie Atomique, Centre d' Etudes Nucleaires de Saclay (France)

    1954-07-01

    This article presents the Geiger-Muller counters which present the great benefit of being simple and steady in comparison with other known sensors. The authors propose an overview of problems related to the use of Geiger-Muller counters (GM counters). They first describe their operation (discharge initiation, discharge propagation, collection of positive ions and current in the counter). They discuss their limitations which are related to the migration delay of primary electrons and positive ions. They describe the operation circuit for counters with organic vapour, and for counters associated with counters using halogens. They address the main properties of GM counters, and the different factors to be taken into account when using them to count radioactive sources. The main types of GM counters are then described (they are used to measure different types of radiation). Measurement techniques are discussed for beta radiation (relationship between the number of disintegrations and the noticed counting rate, case of backscattering, absorption and diffusion in the counter window and in the air, influence of absorption and backscattering in the source), for alpha radiation, and for gamma radiation.

  20. Liquid-helium scintillation detection with germanium photodiodes

    International Nuclear Information System (INIS)

    Luke, P.N.; Haller, E.E.; Steiner, H.M.

    1982-05-01

    Special high-purity germanium photodiodes have been developed for the direct detection of vacuum ultraviolet scintillations in liquid helium. The photodiodes are immersed in the liquid helium, and scintillations are detected through one of the bare sides of the photodiodes. Test results with scintillation photons produced by 5.3-MeV α particles are presented. The use of these photodiodes as liquid-helium scintillation detectors may offer substantial improvements over the alternate detection method requiring the use of wavelength shifters and photomultiplier tubes

  1. Avalanche risk assessment in Russia

    Science.gov (United States)

    Komarov, Anton; Seliverstov, Yury; Sokratov, Sergey; Glazovskaya, Tatiana; Turchaniniva, Alla

    2017-04-01

    The avalanche prone area covers about 3 million square kilometers or 18% of total area of Russia and pose a significant problem in most mountain regions of the country. The constant growth of economic activity, especially in the North Caucasus region and therefore the increased avalanche hazard lead to the demand of the large-scale avalanche risk assessment methods development. Such methods are needed for the determination of appropriate avalanche protection measures as well as for economic assessments during all stages of spatial planning of the territory. The requirement of natural hazard risk assessments is determined by the Federal Law of Russian Federation. However, Russian Guidelines (SP 11-103-97; SP 47.13330.2012) are not clearly presented concerning avalanche risk assessment calculations. A great size of Russia territory, vast diversity of natural conditions and large variations in type and level of economic development of different regions cause significant variations in avalanche risk values. At the first stage of research the small scale avalanche risk assessment was performed in order to identify the most common patterns of risk situations and to calculate full social risk and individual risk. The full social avalanche risk for the territory of country was estimated at 91 victims. The area of territory with individual risk values lesser then 1×10(-6) covers more than 92 % of mountain areas of the country. Within these territories the safety of population can be achieved mainly by organizational activities. Approximately 7% of mountain areas have 1×10(-6) - 1×10(-4) individual risk values and require specific mitigation measures to protect people and infrastructure. Territories with individual risk values 1×10(-4) and above covers about 0,1 % of the territory and include the most severe and hazardous mountain areas. The whole specter of mitigation measures is required in order to minimize risk. The future development of such areas is not recommended

  2. A probabilistic model for snow avalanche occurrence

    Science.gov (United States)

    Perona, P.; Miescher, A.; Porporato, A.

    2009-04-01

    Avalanche hazard forecasting is an important issue in relation to the protection of urbanized environments, ski resorts and of ski-touring alpinists. A critical point is to predict the conditions that trigger the snow mass instability determining the onset and the size of avalanches. On steep terrains the risk of avalanches is known to be related to preceding consistent snowfall events and to subsequent changes in the local climatic conditions. Regression analysis has shown that avalanche occurrence indeed correlates to the amount of snow fallen in consecutive three snowing days and to the state of the settled snow at the ground. Moreover, since different type of avalanches may occur as a result of the interactions of different factors, the process of snow avalanche formation is inherently complex and with some degree of unpredictability. For this reason, although several models assess the risk of avalanche by accounting for all the involved processes with a great detail, a high margin of uncertainty invariably remains. In this work, we explicitly describe such an unpredictable behaviour with an intrinsic noise affecting the processes leading snow instability. Eventually, this sets the basis for a minimalist stochastic model, which allows us to investigate the avalanche dynamics and its statistical properties. We employ a continuous time process with stochastic jumps (snowfalls), deterministic decay (snowmelt and compaction) and state dependent avalanche occurrence (renewals) as a minimalist model for the determination of avalanche size and related intertime occurrence. The physics leading to avalanches is simplified to the extent where only meteorological data and terrain data are necessary to estimate avalanche danger. We explore the analytical formulation of the process and the properties of the probability density function of the avalanche process variables. We also discuss what is the probabilistic link between avalanche size and preceding snowfall event and

  3. Spatial shape of avalanches

    Science.gov (United States)

    Zhu, Zhaoxuan; Wiese, Kay Jörg

    2017-12-01

    In disordered elastic systems, driven by displacing a parabolic confining potential adiabatically slowly, all advance of the system is in bursts, termed avalanches. Avalanches have a finite extension in time, which is much smaller than the waiting time between them. Avalanches also have a finite extension ℓ in space, i.e., only a part of the interface of size ℓ moves during an avalanche. Here we study their spatial shape 〈S(x ) 〉 ℓ given ℓ , as well as its fluctuations encoded in the second cumulant 〈S2(x ) 〉 ℓ c. We establish scaling relations governing the behavior close to the boundary. We then give analytic results for the Brownian force model, in which the microscopic disorder for each degree of freedom is a random walk. Finally, we confirm these results with numerical simulations. To do this properly we elucidate the influence of discretization effects, which also confirms the assumptions entering into the scaling ansatz. This allows us to reach the scaling limit already for avalanches of moderate size. We find excellent agreement for the universal shape and its fluctuations, including all amplitudes.

  4. On the basic mechanism of Pixelized Photon Detectors

    Energy Technology Data Exchange (ETDEWEB)

    Otono, H. [Department of Physics, School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)], E-mail: otono@icepp.s.u-tokyo.ac.jp; Oide, H. [Department of Physics, School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Yamashita, S. [International Center for Elementary Particle Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Yoshioka, T. [Neutron Science Laboratory, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan)

    2009-10-21

    A Pixelized Photon Detector (PPD) is a generic name for the semiconductor devices operated in the Geiger-mode, such as Silicon PhotoMultiplier and Multi-Pixel Photon Counter, which has high photon counting capability. While the internal mechanisms of the PPD have been intensively studied in recent years, the existing models do not include the avalanche process. We have simulated the multiplication and quenching of the avalanche process and have succeeded in reproducing the output waveform of the PPD. Furthermore our model predicts the existence of dead-time in the PPD which has never been numerically predicted. For searching the dead-time, we also have developed waveform analysis method using deconvolution which has the potential to distinguish neighboring pulses precisely. In this paper, we discuss our improved model and waveform analysis method.

  5. Development of a Si-PM-based high-resolution PET system for small animals

    International Nuclear Information System (INIS)

    Yamamoto, Seiichi; Imaizumi, Masao; Watabe, Tadashi; Shimosegawa, Eku; Hatazawa, Jun; Watabe, Hiroshi; Kanai, Yasukazu

    2010-01-01

    A Geiger-mode avalanche photodiode (Si-PM) is a promising photodetector for PET, especially for use in a magnetic resonance imaging (MRI) system, because it has high gain and is less sensitive to a static magnetic field. We developed a Si-PM-based depth-of-interaction (DOI) PET system for small animals. Hamamatsu 4 x 4 Si-PM arrays (S11065-025P) were used for its detector blocks. Two types of LGSO scintillator of 0.75 mol% Ce (decay time: ∼45 ns; 1.1 mm x 1.2 mm x 5 mm) and 0.025 mol% Ce (decay time: ∼31 ns; 1.1 mm x 1.2 mm x 6 mm) were optically coupled in the DOI direction to form a DOI detector, arranged in a 11 x 9 matrix, and optically coupled to the Si-PM array. Pulse shape analysis was used for the DOI detection of these two types of LGSOs. Sixteen detector blocks were arranged in a 68 mm diameter ring to form the PET system. Spatial resolution was 1.6 mm FWHM and sensitivity was 0.6% at the center of the field of view. High-resolution mouse and rat images were successfully obtained using the PET system. We confirmed that the developed Si-PM-based PET system is promising for molecular imaging research.

  6. Photodetectors for the Advanced Gamma-ray Imaging System (AGIS)

    Science.gov (United States)

    Wagner, Robert G.; Advanced Gamma-ray Imaging System AGIS Collaboration

    2010-03-01

    The Advanced Gamma-Ray Imaging System (AGIS) is a concept for the next generation very high energy gamma-ray observatory. Design goals include an order of magnitude better sensitivity, better angular resolution, and a lower energy threshold than existing Cherenkov telescopes. Each telescope is equipped with a camera that detects and records the Cherenkov-light flashes from air showers. The camera is comprised of a pixelated focal plane of blue sensitive and fast (nanosecond) photon detectors that detect the photon signal and convert it into an electrical one. Given the scale of AGIS, the camera must be reliable and cost effective. The Schwarzschild-Couder optical design yields a smaller plate scale than present-day Cherenkov telescopes, enabling the use of more compact, multi-pixel devices, including multianode photomultipliers or Geiger avalanche photodiodes. We present the conceptual design of the focal plane for the camera and results from testing candidate! focal plane sensors.

  7. Low Cost silicon photodiodes for alpha spectrometry

    International Nuclear Information System (INIS)

    Khoury, H.; Lopes, A.; Hazin, C.; Lira, C.B.; Silva, E. da

    1998-01-01

    This study was carried out to evaluate the suitability of using commercially available photodiodes for alpha spectrometry, since the principle on which both operate are similar. Photodiodes are low priced compared to the commonly used semiconductor detectors making them potentially useful for research and teaching purposes. Very thin calibrated alpha sources of 2 41 A m, 2 44 C m and 2 35 U , produced at the Metrology Laboratory of IRD/CNEN, were used to test the performance of three photodiodes. The results showed that the responses of the photodiodes were linear with the alpha particle energy and that the energy resolution varied between 0,79% and 0,45%, with an efficiency of 8%. The resolution and efficiency presented by the photodiodes tested are similar to those obtained with other semiconductor detectors, evidencing that they can be used successfully as alpha detectors

  8. Calibration of snow avalanche mathematical models using the data of real avalanches in the Ile (Zailiyskiy Alatau Range

    Directory of Open Access Journals (Sweden)

    V. P. Blagoveshchensky

    2017-01-01

    Full Text Available The calibration of the dry friction and turbulent friction coefficients is necessary for computer simulation of avalanches. The method of back calculation based on data on actual avalanches is used for this purpose. The article presents the results of the calibration of the Eglit’s and RAMMS models for Ile Alatau range condi‑ tions. The range is located in Kazakhstan. The data on six avalanches in the same avalanche site were used. Five avalanches were dry, and one avalanche was wet. Avalanches volume varied from 2000 to 12000  m3. Maximum speed avalanches were between 15 and 30  m/s, the flow height  – from 3 to 10  m. Series of back calculations with different values of the friction coefficients was made to obtain the calibrated coeffi‑ cients. The calibrated coefficients were chosen under condition of the best fit with real avalanches. The cal‑ ibrated coefficients were following. For the Eglit’s model for dry avalanches of the volume 2000–5000  m3 μ = 0.46÷0.48, k = 0.005–0.006, and the volume 8000–12000 m3 μ = 0.38÷0.42, k = 0.002÷0.003. For RAMMS model for dry avalanches of the volume of 2000–5000 m3 μ (dry friction coefficient = 0.35÷0.4, ξ (viscous friction coefficient = 1500÷2000 m/s2, and the volume 8,000–12,000 m3 μ = 0.3÷0.35, ξ = 2000÷3000 m/s2. For wet avalanches of the volume 12,000 m3 μ = 0.35, ξ = 1500 m/s2. The work on the calibration will be con‑ tinued to obtain the friction coefficients for the Eglit’s and RAMMS models. The additional data on real ava‑ lanches will be needed for this purpose.

  9. Avalanches and Criticality in Driven Magnetic Skyrmions

    Science.gov (United States)

    Díaz, S. A.; Reichhardt, C.; Arovas, D. P.; Saxena, A.; Reichhardt, C. J. O.

    2018-03-01

    We show using numerical simulations that slowly driven Skyrmions interacting with random pinning move via correlated jumps or avalanches. The avalanches exhibit power-law distributions in their duration and size, and the average avalanche shape for different avalanche durations can be scaled to a universal function, in agreement with theoretical predictions for systems in a nonequilibrium critical state. A distinctive feature of Skyrmions is the influence of the nondissipative Magnus term. When we increase the ratio of the Magnus term to the damping term, a change in the universality class of the behavior occurs, the average avalanche shape becomes increasingly asymmetric, and individual avalanches exhibit motion in the direction perpendicular to their own density gradient.

  10. Extending the dynamic range of silicon photomultipliers without increasing pixel count

    International Nuclear Information System (INIS)

    Johnson, Kurtis F.

    2010-01-01

    A silicon photomultiplier, sometimes called 'multipixel photon counter', which we here refer to as a 'SiPM', is a photo-sensitive device built from an avalanche photodiode array of pixels on a common silicon substrate, such that it can detect single photon events. The dimensions of a pixel may vary from 20 to 100 μm and their density can be greater than 1000 per square millimeter. Each pixel in a SiPM operates in Geiger mode and is coupled to the output by a quenching resistor. Although each pixel operates in digital mode, the SiPM is an analog device because all the pixels are read in parallel, making it possible to generate signals within a dynamic range from a single photon to a large number of photons, ultimately limited by the number of pixels on the chip. In this note we describe a simple and general method of increasing the dynamic range of a SiPM beyond that one may naively assume from the shape of the cumulative distribution function of the SiPM response to the average number of photons per pixel. We show that by rendering the incoming flux of photons to be non-uniform in a prescribed manner, a significant increase in dynamic range is achievable. Such re-distribution of the incoming flux may be accomplished with simple, non-focusing lenses, prisms, interference films, mirrors or attenuating films. Almost any optically non-inert interceding device can increase the dynamic range of the SiPM.

  11. Avalanches in insulating gases

    International Nuclear Information System (INIS)

    Verhaart, H.F.A.

    1982-01-01

    Avalanches of charged particles in gases are often studied with the ''electrical method'', the measurement of the waveform of the current in the external circuit. In this thesis a substantial improvement of the time resolution of the measuring setup, to be used for the electrical method, is reported. The avalanche is started by an N 2 -laser with a pulse duration of only 0.6 ns. With this laser it is possible to release a high number of primary electrons (some 10 8 ) which makes it possible to obtain sizeable signals, even at low E/p values. With the setup it is possible to analyze current waveforms with a time resolution down to 1.4 ns, determined by both the laser and the measuring system. Furthermore it is possible to distinguish between the current caused by the electrons and the current caused by the ions in the avalanche and to monitor these currents simultaneously. Avalanche currents are measured in N 2 , CO 2 , O 2 , H 2 O, air of varying humidity, SF 6 and SF 6 /N 2 mixtures. Depending on the nature of the gas and the experimental conditions, processes as diffusion, ionization, attachment, detachment, conversion and secondary emission are observed. Values of parameters with which these processes can be described, are derived from an analysis of the current waveforms. For this analysis already published theories and new theories described in this thesis are used. The drift velocity of both the electrons and the ions could be easily determined from measured avalanche currents. Special attention is paid to avalanches in air becasue of the practical importance of air insulation. (Auth.)

  12. Gamma-ray detection with an UV-enhanced photodiode and scintillation crystals emitting at short wavelengths

    International Nuclear Information System (INIS)

    Johansen, G.A.

    1997-01-01

    A low-noise ion implanted photodiode with high spectral response in the deep blue/UV region has been tested as read-out device for scintillation crystals with matching emission spectra (YAP(Ce), GSO(Ce), BGO and CsI(Tl)). This gamma-ray detector concept is attractive in many industrial applications where compactness, reliability and ambient temperature operation are important. The results show that the amount of detected scintillation light energy falls rapidly off as the wavelength of the scintillation light decreases. It is concluded that the dynamic spectral response of the photodiode, due to increasing carrier collection times, is considerably less than the DC response at short wavelengths. The diode is not useful in pulse mode operation with scintillation crystals emitting at wavelengths below about 400 nm. For read-out of CsI(Tl) with 661.6 keV gamma-radiation, however, the photodiode concept shows better energy resolution (7.1%) than other detectors. (orig.)

  13. Diamond photodiodes for x-ray application

    Energy Technology Data Exchange (ETDEWEB)

    Distel, James R [Los Alamos National Laboratory; Smedley, John [BNL; Keister, Jeffrey W [BNL; Muller, Erik [STONY BROOK UNIV.; Jordan - Sweet, Jean [WATSON RESEARCH CENTER; Bohon, Jen [CASE WESTERN RESERVE UNIV.; Dong, Bin [NON LANL

    2009-01-01

    Single crystal high purity CVD diamonds have been metallized and calibrated as photodiodes at the National Synchrotron Light Source (NSLS). Current mode responsivity measurements have been made over a wide range (0.2-28 keV) of photon energies across several beamlines. Linear response has been achieved over ten orders of magnitude of incident flux, along with uniform spatial response. A simple model of responsivity has been used to describe the results, yielding a value of 13.3 {+-} 0.5 eV for the mean pair creation energy. The responsivity vs. photon energy data show a dip for photon energies near the carbon edge (284 eV), indicating incomplete charge collection for carriers created less than one micron from the metallized layer.

  14. Photodiodes utilization as ionizing radiation detectors

    International Nuclear Information System (INIS)

    Khoury, H.J.; Melo, F.A. de

    1987-01-01

    The response of photodiodes to α and γ radiation is studied, using for α spectrometry measures and for γ radiation dosimetry. Therefore, the response of BPY-12 photodiodes as α particle detector is first studied. The results show that the response is linear with the energy of incidence radiation, one resolution 25Kev for energy of 5,4 MeV from 241 Am. For dosimetric measures, the response of SHF-206 photodiodes, when exposed at γ radiation is studied, and the results show taht the response of this detector is linear with the dose ratio, proving its practicability in γ radiation dosimetry. (C.G.C.) [pt

  15. Energy and dissipated work in snow avalanches

    Science.gov (United States)

    Bartelt, P.; Buser, O.

    2004-12-01

    Using the results of large scale avalanche experiments at the Swiss Vallée de la Sionne test site, the energy balance of several snow avalanches is determined. Avalanches convert approximately one-seventh of their potential energy into kinetic energy. The total potential energy depends strongly on the entrained snowcover, indicating that entrainment processes cannot be ignored when predicting terminal velocities and runout distances. We find energy dissipation rates on the order of 1 GW. Fluidization of the fracture slab can be identified in the experiments as an increase in dissipation rate, thereby explaining the initial and rapid acceleration of avalanches after release. Interestingly, the dissipation rates appear to be constant along the track, although large fluctuations in internal velocity exist. Thus, we can demonstrate within the context of non-equilibrium thermodynamics that -- in space -- granular snow avalanches are irreversible, dissipative systems that minimize entropy production because they appear to reach a steady-state non-equilibrium. A thermodynamic analysis reveals that fluctuations in velocity depend on the roughness of the flow surface and viscosity of the granular system. We speculate that this property explains the transition from flowing avalanches to powder avalanches.

  16. Low-cost amplifier for alpha detection with photodiode

    Energy Technology Data Exchange (ETDEWEB)

    Domienikan, Cláudio; Costa, Priscila; Genezini, Frederico A.; Zahn, Guilherme S., E-mail: clanikan@ipen.br, E-mail: pcosta@ipen.br, E-mail: fredzini@ipen.br, E-mail: gzahn@ipen.br [Instituto de Pesquisas Energéticas e Nucleares (IPEN/CNEN-SP), São Paulo, SP (Brazil)

    2017-07-01

    A low-cost amplifier for Hamamatsu S3590-09 PIN photodiode to be used in alpha detection is presented. This amplifier consists basically of two circuits: a pulse preamplifier and a shaper-driver. The PIN photodiode is reverse-biased and connected to a charge preamplifier input. Incident alpha particles generate a small current pulse in the photodiode. The integrating circuit of the low noise preamplifier transforms current pulse into a voltage pulse with amplitude proportional to the charge carried by the current pulse. The shaper-driver consists of a differentiator and an integrator and is responsible for filtering and further amplifying the preamplifier signal, generating a NIM-compatible energy pulse. The performance of the set photodiode-amplifier was successively tested through the use of a {sup 243}Am radioactive source. The low-cost photodiode amplifier was designed and constructed at IPEN - CNEN/SP using national components and expertise. (author)

  17. The photodiodes response in beta dosimetry

    International Nuclear Information System (INIS)

    Khoury, Helen; Amaral, Ademir; Hazin, Clovis; Melo, Francisco

    1996-01-01

    The response of the photodiodes BPY-12, BPW-34 and SFH-206 is tested for use as beta dosimeters. The results obtained show a dose-response relationships as well as less than 1% of coefficient of variation for the reproducibility of their responses. The photodiode BPY-12 has presented a better response in comparison with the others

  18. Imaging findings of avalanche victims

    Energy Technology Data Exchange (ETDEWEB)

    Grosse, Alexandra B.; Grosse, Claudia A.; Anderson, Suzanne [University Hospital of Berne, Inselspital, Department of Diagnostic, Pediatric and Interventional Radiology, Berne (Switzerland); Steinbach, Lynne S. [University of California San Francisco, Department of Radiology, San Francisco, CA (United States); Zimmermann, Heinz [University Hospital of Berne, Inselspital, Department of Trauma and Emergency Medicine, Berne (Switzerland)

    2007-06-15

    Skiing and hiking outside the boundaries remains an attractive wilderness activity despite the danger of avalanches. Avalanches occur on a relatively frequent basis and may be devastating. Musculoskeletal radiologists should be acquainted with these injuries. Fourteen avalanche victims (11 men and 3 women; age range 17-59 years, mean age 37.4 years) were air transported to a high-grade trauma centre over a period of 2 years. Radiographs, CT and MR images were prospectively evaluated by two observers in consensus. Musculoskeletal findings (61%) were more frequent than extraskeletal findings (39%). Fractures were most commonly seen (36.6%), involving the spine (14.6%) more frequently than the extremities (9.8%). Blunt abdominal and thoracic trauma were the most frequent extraskeletal findings. A wide spectrum of injuries can be found in avalanche victims, ranging from extremity fractures to massive polytrauma. Asphyxia remains the main cause of death along with hypoxic brain injury and hypothermia. (orig.)

  19. Formation of the electrical pulse in the SQS mode

    International Nuclear Information System (INIS)

    Han Jiaxiang; Xu Zizong; Li Hongdi; Chen Hongfang

    1994-01-01

    The pulse of the electrical signals from the counter working in SQS mode have been displayed and studied carefully. Some interesting information on the formation of SQS avalanche has been presented. The typical value of the transition time from the primary to the SQS avalanche is 15 ns, that of its spread is 10 ns

  20. On the short-circuit and avalanche ruggedness reliability assessment of SiC MOSFET modules

    DEFF Research Database (Denmark)

    Ionita, Claudiu; Nawaz, Muhammad; Ilves, Kalle

    2017-01-01

    to failure, a gate-source voltage drop has been recorded, which is associated with a high G-S leakage current. The main failure mechanism, however, is the thermal runaway which leads the devices into avalanche breakdown mode. During the UIS tests, multiple samples from the three vendors of the power modules...

  1. New silicon photodiodes for detection of the 1064nm wavelength radiation

    Science.gov (United States)

    Wegrzecki, Maciej; Piotrowski, Tadeusz; Puzewicz, Zbigniew; Bar, Jan; Czarnota, Ryszard; Dobrowolski, Rafal; Klimov, Andrii; Kulawik, Jan; Kłos, Helena; Marchewka, Michał; Nieprzecki, Marek; Panas, Andrzej; Seredyński, Bartłomiej; Sierakowski, Andrzej; Słysz, Wojciech; Synkiewicz, Beata; Szmigiel, Dariusz; Zaborowski, Michał

    2016-12-01

    In this paper a concept of a new bulk structure of p+-υ-n+ silicon photodiodes optimized for the detection of fast-changing radiation at the 1064 nm wavelength is presented. The design and technology for two types of quadrant photodiodes, the 8-segment photodiode and the 32-element linear photodiode array that were developed according to the concept are described. Electric and photoelectric parameters of the photodiodes mentioned above are presented.

  2. Measuring neuronal avalanches in disordered systems with absorbing states

    Science.gov (United States)

    Girardi-Schappo, M.; Tragtenberg, M. H. R.

    2018-04-01

    Power-law-shaped avalanche-size distributions are widely used to probe for critical behavior in many different systems, particularly in neural networks. The definition of avalanche is ambiguous. Usually, theoretical avalanches are defined as the activity between a stimulus and the relaxation to an inactive absorbing state. On the other hand, experimental neuronal avalanches are defined by the activity between consecutive silent states. We claim that the latter definition may be extended to some theoretical models to characterize their power-law avalanches and critical behavior. We study a system in which the separation of driving and relaxation time scales emerges from its structure. We apply both definitions of avalanche to our model. Both yield power-law-distributed avalanches that scale with system size in the critical point as expected. Nevertheless, we find restricted power-law-distributed avalanches outside of the critical region within the experimental procedure, which is not expected by the standard theoretical definition. We remark that these results are dependent on the model details.

  3. X-ray imaging with amorphous selenium: Pulse height measurements of avalanche gain fluctuations

    International Nuclear Information System (INIS)

    Lui, Brian J. M.; Hunt, D. C.; Reznik, A.; Tanioka, K.; Rowlands, J. A.

    2006-01-01

    Avalanche multiplication in amorphous selenium (a-Se) can provide a large, adjustable gain for active matrix flat panel imagers (AMFPI), enabling quantum noise limited x-ray imaging during both radiography and fluoroscopy. In the case of direct conversion AMFPI, the multiplication factor for each x ray is a function of its depth of interaction, and the resulting variations in gain can reduce the detective quantum efficiency (DQE) of the system. An experimental method was developed to measure gain fluctuations by analyzing images of individual x rays that were obtained using a video camera with an a-Se target operated in avalanche mode. Pulse height spectra (PHS) of the charge produced per x ray were recorded for monoenergetic 30.9, 49.4, and 73.8 keV x-ray sources. The rapid initial decay and long tail of each PHS can be explained by a model in which positive charge dominates the initiation of avalanche. The Swank information factor quantifies the effect of gain fluctuation on DQE and was calculated from the PHS. The information factor was found to be 0.5 for a 25 μm a-Se layer with a maximum gain of ∼300. Changing the energy of the incident x ray influenced the range of the primary photoelectron and noticeably affected the tail of the experimental PHS, but did not significantly change the avalanche Swank factor

  4. Spatial determination of magnetic avalanche ignition points

    International Nuclear Information System (INIS)

    Jaafar, Reem; McHugh, S.; Suzuki, Yoko; Sarachik, M.P.; Myasoedov, Y.; Zeldov, E.; Shtrikman, H.; Bagai, R.; Christou, G.

    2008-01-01

    Using time-resolved measurements of local magnetization in the molecular magnet Mn 12 -ac, we report studies of magnetic avalanches (fast magnetization reversals) with non-planar propagating fronts, where the curved nature of the magnetic fronts is reflected in the time-of-arrival at micro-Hall sensors placed at the surface of the sample. Assuming that the avalanche interface is a spherical bubble that grows with a radius proportional to time, we are able to locate the approximate ignition point of each avalanche in a two-dimensional cross-section of the crystal. We find that although in most samples the avalanches ignite at the long ends, as found in earlier studies, there are crystals in which ignition points are distributed throughout an entire weak region near the center, with a few avalanches still originating at the ends

  5. Spatial determination of magnetic avalanche ignition points

    Energy Technology Data Exchange (ETDEWEB)

    Jaafar, Reem; McHugh, S.; Suzuki, Yoko [Physics Department, City College of the City University of New York, New York, NY 10031 (United States); Sarachik, M.P. [Physics Department, City College of the City University of New York, New York, NY 10031 (United States)], E-mail: sarachik@sci.ccny.cuny.edu; Myasoedov, Y.; Zeldov, E.; Shtrikman, H. [Department Condensed Matter Physics, Weizmann Institute of Science, Rehovot 76100 (Israel); Bagai, R.; Christou, G. [Department of Chemistry, University of Florida, Gainesville, FL 32611 (United States)

    2008-03-15

    Using time-resolved measurements of local magnetization in the molecular magnet Mn{sub 12}-ac, we report studies of magnetic avalanches (fast magnetization reversals) with non-planar propagating fronts, where the curved nature of the magnetic fronts is reflected in the time-of-arrival at micro-Hall sensors placed at the surface of the sample. Assuming that the avalanche interface is a spherical bubble that grows with a radius proportional to time, we are able to locate the approximate ignition point of each avalanche in a two-dimensional cross-section of the crystal. We find that although in most samples the avalanches ignite at the long ends, as found in earlier studies, there are crystals in which ignition points are distributed throughout an entire weak region near the center, with a few avalanches still originating at the ends.

  6. Real time avalanche detection for high risk areas.

    Science.gov (United States)

    2014-12-01

    Avalanches routinely occur on State Highway 21 (SH21) between Lowman and Stanley, Idaho each winter. The avalanches pose : a threat to the safety of maintenance workers and the traveling public. A real-time avalanche detection system will allow the :...

  7. Application of a background-compensated Geiger-Mueller counter to a survey meter

    International Nuclear Information System (INIS)

    Mori, C.; Kumanomido, H.; Watanabe, T.

    1984-01-01

    A background-compensated Geiger-Mueller counter was used as a probe for a GM survey meter to obtain a net count rate of β-rays from a radioactive source in a quick survey. Although a background counting ratio between the two parts in the counter, front and rear, varied somewhat depending on the incident direction of background γ-rays, it was possible to compensate the background counts by subtracting a part of the rear counts, which were background counts, from the front counts, which contained β-ray counts and background counts. Undesirable small pulses generated during the recovering time after a full Geiger discharge were eliminated by an anticoincidence gating method. The survey meter with this counter and a differential ratemeter is useful for obtaining a net count rate of β-rays emitted from a surface radioactive-contamination or from a source being put near the window of the counter with nearly the same accuracy in half the measuring time as compared with conventional GM counters. (orig.)

  8. Assessing the importance of terrain parameters on glide avalanche release

    Science.gov (United States)

    Peitzsch, E.; Hendrikx, J.; Fagre, D. B.

    2013-12-01

    Glide snow avalanches are dangerous and difficult to predict. Despite recent research there is still a lack of understanding regarding the controls of glide avalanche release. Glide avalanches often occur in similar terrain or the same locations annually and observations suggest that topography may be critical. Thus, to gain an understanding of the terrain component of these types of avalanches we examined terrain parameters associated with glide avalanche release as well as areas of consistent glide crack formation but no subsequent avalanches. Glide avalanche occurrences visible from the Going-to-the-Sun Road corridor in Glacier National Park, Montana from 2003-2013 were investigated using an avalanche database derived of daily observations each year from April 1 to June 15. This yielded 192 glide avalanches in 53 distinct avalanche paths. Each avalanche occurrence was digitized in a GIS using satellite, oblique, and aerial imagery as reference. Topographical parameters such as area, slope, aspect, elevation and elevation were then derived for the entire dataset utilizing GIS tools and a 10m DEM. Land surface substrate and surface geology were derived from National Park Service Inventory and Monitoring maps and U.S. Geological Survey surface geology maps, respectively. Surface roughness and glide factor were calculated using a four level classification index. . Then, each avalanche occurrence was aggregated to general avalanche release zones and the frequencies were compared. For this study, glide avalanches released in elevations ranging from 1300 to 2700 m with a mean aspect of 98 degrees (east) and a mean slope angle of 38 degrees. The mean profile curvature for all glide avalanches was 0.15 and a plan curvature of -0.01, suggesting a fairly linear surface (i.e. neither convex nor concave). The glide avalanches occurred in mostly bedrock made up of dolomite and limestone slabs and talus deposits with very few occurring in alpine meadows. However, not all glide

  9. Assessing the importance of terrain parameters on glide avalanche release

    Science.gov (United States)

    Peitzsch, Erich H.; Hendrikx, Jordy; Fagre, Daniel B.

    2014-01-01

    Glide snow avalanches are dangerous and difficult to predict. Despite recent research there is still a lack of understanding regarding the controls of glide avalanche release. Glide avalanches often occur in similar terrain or the same locations annually and observations suggest that topography may be critical. Thus, to gain an understanding of the terrain component of these types of avalanches we examined terrain parameters associated with glide avalanche release as well as areas of consistent glide crack formation but no subsequent avalanches. Glide avalanche occurrences visible from the Going-to-the-Sun Road corridor in Glacier National Park, Montana from 2003-2013 were investigated using an avalanche database derived of daily observations each year from April 1 to June 15. This yielded 192 glide avalanches in 53 distinct avalanche paths. Each avalanche occurrence was digitized in a GIS using satellite, oblique, and aerial imagery as reference. Topographical parameters such as area, slope, aspect, elevation and elevation were then derived for the entire dataset utilizing GIS tools and a 10m DEM. Land surface substrate and surface geology were derived from National Park Service Inventory and Monitoring maps and U.S. Geological Survey surface geology maps, respectively. Surface roughness and glide factor were calculated using a four level classification index. . Then, each avalanche occurrence was aggregated to general avalanche release zones and the frequencies were compared. For this study, glide avalanches released in elevations ranging from 1300 to 2700 m with a mean aspect of 98 degrees (east) and a mean slope angle of 38 degrees. The mean profile curvature for all glide avalanches was 0.15 and a plan curvature of -0.01, suggesting a fairly linear surface (i.e. neither convex nor concave). The glide avalanches occurred in mostly bedrock made up of dolomite and limestone slabs and talus deposits with very few occurring in alpine meadows. However, not all glide

  10. Range walk error correction and modeling on Pseudo-random photon counting system

    Science.gov (United States)

    Shen, Shanshan; Chen, Qian; He, Weiji

    2017-08-01

    Signal to noise ratio and depth accuracy are modeled for the pseudo-random ranging system with two random processes. The theoretical results, developed herein, capture the effects of code length and signal energy fluctuation are shown to agree with Monte Carlo simulation measurements. First, the SNR is developed as a function of the code length. Using Geiger-mode avalanche photodiodes (GMAPDs), longer code length is proven to reduce the noise effect and improve SNR. Second, the Cramer-Rao lower bound on range accuracy is derived to justify that longer code length can bring better range accuracy. Combined with the SNR model and CRLB model, it is manifested that the range accuracy can be improved by increasing the code length to reduce the noise-induced error. Third, the Cramer-Rao lower bound on range accuracy is shown to converge to the previously published theories and introduce the Gauss range walk model to range accuracy. Experimental tests also converge to the presented boundary model in this paper. It has been proven that depth error caused by the fluctuation of the number of detected photon counts in the laser echo pulse leads to the depth drift of Time Point Spread Function (TPSF). Finally, numerical fitting function is used to determine the relationship between the depth error and the photon counting ratio. Depth error due to different echo energy is calibrated so that the corrected depth accuracy is improved to 1cm.

  11. 12 GeV detector technology at Jefferson Lab

    Energy Technology Data Exchange (ETDEWEB)

    Leckey, John P. [Indiana University, Bloomington, IN 47405 (United States); Collaboration: GlueX Collaboration

    2013-04-19

    The Thomas Jefferson National Accelerator Facility (JLab) is presently in the middle of an upgrade to increase the energy of its CW electron beam from 6 GeV to 12 GeV along with the addition of a fourth experimental hall. Driven both by necessity and availability, novel detectors and electronics modules have been used in the upgrade. One such sensor is the Silicon Photomultiplier (SiPM), specifically a Multi-Pixel Photon Counter (MPPC), which is an array of avalanche photodiode pixels operating in Geiger mode that are used to sense photons. The SiPMs replace conventional photomultiplier tubes and have several distinct advantages including the safe operation in a magnetic field and the lack of need for high voltage. Another key to 12 GeV success is advanced fast electronics. Jlab will use custom 250 MHz and 125 MHz 12-bit analog to digital converters (ADCs) and time to digital converters (TDCs) all of which take advantage of VME Switched Serial (VXS) bus with its GB/s high bandwidth readout capability. These new technologies will be used to readout drift chambers, calorimeters, spectrometers and other particle detectors at Jlab once the 12 GeV upgrade is complete. The largest experiment at Jlab utilizing these components is GlueX - an experiment in the newly constructed Hall D that will study the photoproduction of light mesons in the search for hybrid mesons. The performance of these components and their respective detectors will be presented.

  12. FACT. New image parameters based on the watershed-algorithm

    Energy Technology Data Exchange (ETDEWEB)

    Linhoff, Lena; Bruegge, Kai Arno; Buss, Jens [TU Dortmund (Germany). Experimentelle Physik 5b; Collaboration: FACT-Collaboration

    2016-07-01

    FACT, the First G-APD Cherenkov Telescope, is the first imaging atmospheric Cherenkov telescope that is using Geiger-mode avalanche photodiodes (G-APDs) as photo sensors. The raw data produced by this telescope are processed in an analysis chain, which leads to a classification of the primary particle that induce a shower and to an estimation of its energy. One important step in this analysis chain is the parameter extraction from shower images. By the application of a watershed algorithm to the camera image, new parameters are computed. Perceiving the brightness of a pixel as height, a set of pixels can be seen as 'landscape' with hills and valleys. A watershed algorithm groups all pixels to a cluster that belongs to the same hill. From the emerging segmented image, one can find new parameters for later analysis steps, e.g. number of clusters, their shape and containing photon charge. For FACT data, the FellWalker algorithm was chosen from the class of watershed algorithms, because it was designed to work on discrete distributions, in this case the pixels of a camera image. The FellWalker algorithm is implemented in FACT-tools, which provides the low level analysis framework for FACT. This talk will focus on the computation of new, FellWalker based, image parameters, which can be used for the gamma-hadron separation. Additionally, their distributions concerning real and Monte Carlo Data are compared.

  13. Neuronal avalanches and learning

    Energy Technology Data Exchange (ETDEWEB)

    Arcangelis, Lucilla de, E-mail: dearcangelis@na.infn.it [Department of Information Engineering and CNISM, Second University of Naples, 81031 Aversa (Italy)

    2011-05-01

    Networks of living neurons represent one of the most fascinating systems of biology. If the physical and chemical mechanisms at the basis of the functioning of a single neuron are quite well understood, the collective behaviour of a system of many neurons is an extremely intriguing subject. Crucial ingredient of this complex behaviour is the plasticity property of the network, namely the capacity to adapt and evolve depending on the level of activity. This plastic ability is believed, nowadays, to be at the basis of learning and memory in real brains. Spontaneous neuronal activity has recently shown features in common to other complex systems. Experimental data have, in fact, shown that electrical information propagates in a cortex slice via an avalanche mode. These avalanches are characterized by a power law distribution for the size and duration, features found in other problems in the context of the physics of complex systems and successful models have been developed to describe their behaviour. In this contribution we discuss a statistical mechanical model for the complex activity in a neuronal network. The model implements the main physiological properties of living neurons and is able to reproduce recent experimental results. Then, we discuss the learning abilities of this neuronal network. Learning occurs via plastic adaptation of synaptic strengths by a non-uniform negative feedback mechanism. The system is able to learn all the tested rules, in particular the exclusive OR (XOR) and a random rule with three inputs. The learning dynamics exhibits universal features as function of the strength of plastic adaptation. Any rule could be learned provided that the plastic adaptation is sufficiently slow.

  14. Neuronal avalanches and learning

    International Nuclear Information System (INIS)

    Arcangelis, Lucilla de

    2011-01-01

    Networks of living neurons represent one of the most fascinating systems of biology. If the physical and chemical mechanisms at the basis of the functioning of a single neuron are quite well understood, the collective behaviour of a system of many neurons is an extremely intriguing subject. Crucial ingredient of this complex behaviour is the plasticity property of the network, namely the capacity to adapt and evolve depending on the level of activity. This plastic ability is believed, nowadays, to be at the basis of learning and memory in real brains. Spontaneous neuronal activity has recently shown features in common to other complex systems. Experimental data have, in fact, shown that electrical information propagates in a cortex slice via an avalanche mode. These avalanches are characterized by a power law distribution for the size and duration, features found in other problems in the context of the physics of complex systems and successful models have been developed to describe their behaviour. In this contribution we discuss a statistical mechanical model for the complex activity in a neuronal network. The model implements the main physiological properties of living neurons and is able to reproduce recent experimental results. Then, we discuss the learning abilities of this neuronal network. Learning occurs via plastic adaptation of synaptic strengths by a non-uniform negative feedback mechanism. The system is able to learn all the tested rules, in particular the exclusive OR (XOR) and a random rule with three inputs. The learning dynamics exhibits universal features as function of the strength of plastic adaptation. Any rule could be learned provided that the plastic adaptation is sufficiently slow.

  15. Thermoluminescent accident dose reader with photodiode; Termoluminiscencni litalnik akcidentnih doz s fotodiodo

    Energy Technology Data Exchange (ETDEWEB)

    Miklavzic, U; Mihelic, M [Institut Jozef Stefan, Ljubljana (Yugoslavia)

    1982-07-01

    The field version of TL reader for accident dose region 0.01-20 Gy is described. For light detection, the thermostated photodiode was used permitting measurements at the ambient temperatures from -20 C degrees to 50 C degrees, and a new mode of the glow curve integration. Results can be presented as integral or peak values of the glow curve. The reader was adapted for dosemeters IJS-TLD08 from sintered CaF2:Mn pellets. (author)

  16. Actinide oxide photodiode and nuclear battery

    Energy Technology Data Exchange (ETDEWEB)

    Sykora, Milan; Usov, Igor

    2017-12-05

    Photodiodes and nuclear batteries may utilize actinide oxides, such a uranium oxide. An actinide oxide photodiode may include a first actinide oxide layer and a second actinide oxide layer deposited on the first actinide oxide layer. The first actinide oxide layer may be n-doped or p-doped. The second actinide oxide layer may be p-doped when the first actinide oxide layer is n-doped, and the second actinide oxide layer may be n-doped when the first actinide oxide layer is p-doped. The first actinide oxide layer and the second actinide oxide layer may form a p/n junction therebetween. Photodiodes including actinide oxides are better light absorbers, can be used in thinner films, and are more thermally stable than silicon, germanium, and gallium arsenide.

  17. General Roy S. Geiger, USMC: Marine Aviator, Joint Force Commander

    Science.gov (United States)

    2007-06-01

    This is a strong assertion, given the significant and better-known contributions of great Marines such as John Lejeune, Smedley Butler, Alexander...While stationed in Panama, Geiger made a favorable impression on Major Smedley Butler, who later earned the Medal of Honor twice and became a...fifth Naval Aviator. 43 Johnson, 5. 44 Robert Sherrod, History of Marine Corps Aviation in World War II (Baltimore, MD: The Nautical and Aviation

  18. Electronic response of a photodiode coupled to a boron thin film

    Energy Technology Data Exchange (ETDEWEB)

    Costa, Priscila; Costa, Fabio E.; Raele, Marcus P.; Zahn, Guilherme S.; Geraldo, Bianca; Vieira Junior, Nilson D.; Samad, Ricardo E.; Genezini, Frederico A., E-mail: priscila3.costa@usp.br, E-mail: fredzini@ipen.br [Instituto de Pesquisas Energéticas e Nucleares (IPEN/CNEN-SP), São Paulo, SP (Brazil)

    2017-07-01

    A portable thermal neutron detector is proposed in this work using a silicon photodiode coupled to a boron thin film. The aim of this work was to verify the effect in the electronic response of this specific photodiode due to boron deposition, since the direct deposition of boron in the semiconductor surface could affect its electrical properties specifically the p-type layer that affects directly the depletion region of the semiconductor reducing the neutron detector efficiency count. Three boron depositions with different thickness were performed in the photodiode (S3590-09) surface by pulsed laser deposition and the photodiode was characterized, before and after the deposition process, using a radioactive americium source. Energy spectra were used to verify the electronic response of the photodiode, due to the fact that it is possible to relate it to the photopeak pulse height and resolution. Spectra from the photodiode without and with boron film deposition were compared and a standard photodiode (S3590-04) that had the electronic signal conserved was used as reference to the pulse height for electronics adjustments. The photopeak energy resolution for the photodiode without boron layer was 10.26%. For the photodiode with boron deposition at different thicknesses, the resolution was: 7.64 % (0.14 μm), 7.30 % (0.44 μm) and 6.80 % (0.63 μm). From these results it is possible to evaluate that there was not any degradation in the silicon photodiode. (author)

  19. Rock-avalanche dynamics revealed by large-scale field mapping and seismic signals at a highly mobile avalanche in the West Salt Creek valley, western Colorado

    Science.gov (United States)

    Coe, Jeffrey A.; Baum, Rex L.; Allstadt, Kate E.; Kochevar, Bernard; Schmitt, Robert G.; Morgan, Matthew L.; White, Jonathan L.; Stratton, Benjamin T.; Hayashi, Timothy A.; Kean, Jason W.

    2016-01-01

    On 25 May 2014, a rain-on-snow–induced rock avalanche occurred in the West Salt Creek valley on the northern flank of Grand Mesa in western Colorado (United States). The avalanche mobilized from a preexisting rock slide in the Green River Formation and traveled 4.6 km down the confined valley, killing three people. The avalanche was rare for the contiguous United States because of its large size (54.5 Mm3) and high mobility (height/length = 0.14). To understand the avalanche failure sequence, mechanisms, and mobility, we conducted a forensic analysis using large-scale (1:1000) structural mapping and seismic data. We used high-resolution, unmanned aircraft system imagery as a base for field mapping, and analyzed seismic data from 22 broadband stations (distances earth and tracked these forces using curves in the avalanche path. Our results revealed that the rock avalanche was a cascade of landslide events, rather than a single massive failure. The sequence began with an early morning landslide/debris flow that started ∼10 h before the main avalanche. The main avalanche lasted ∼3.5 min and traveled at average velocities ranging from 15 to 36 m/s. For at least two hours after the avalanche ceased movement, a central, hummock-rich core continued to move slowly. Since 25 May 2014, numerous shallow landslides, rock slides, and rock falls have created new structures and modified avalanche topography. Mobility of the main avalanche and central core was likely enhanced by valley floor material that liquefied from undrained loading by the overriding avalanche. Although the base was likely at least partially liquefied, our mapping indicates that the overriding avalanche internally deformed predominantly by sliding along discrete shear surfaces in material that was nearly dry and had substantial frictional strength. These results indicate that the West Salt Creek avalanche, and probably other long-traveled avalanches, could be modeled as two layers: a thin, liquefied

  20. High bit rate germanium single photon detectors for 1310nm

    Science.gov (United States)

    Seamons, J. A.; Carroll, M. S.

    2008-04-01

    There is increasing interest in development of high speed, low noise and readily fieldable near infrared (NIR) single photon detectors. InGaAs/InP Avalanche photodiodes (APD) operated in Geiger mode (GM) are a leading choice for NIR due to their preeminence in optical networking. After-pulsing is, however, a primary challenge to operating InGaAs/InP single photon detectors at high frequencies1. After-pulsing is the effect of charge being released from traps that trigger false ("dark") counts. To overcome this problem, hold-off times between detection windows are used to allow the traps to discharge to suppress after-pulsing. The hold-off time represents, however, an upper limit on detection frequency that shows degradation beginning at frequencies of ~100 kHz in InGaAs/InP. Alternatively, germanium (Ge) single photon avalanche photodiodes (SPAD) have been reported to have more than an order of magnitude smaller charge trap densities than InGaAs/InP SPADs2, which allowed them to be successfully operated with passive quenching2 (i.e., no gated hold off times necessary), which is not possible with InGaAs/InP SPADs, indicating a much weaker dark count dependence on hold-off time consistent with fewer charge traps. Despite these encouraging results suggesting a possible higher operating frequency limit for Ge SPADs, little has been reported on Ge SPAD performance at high frequencies presumably because previous work with Ge SPADs has been discouraged by a strong demand to work at 1550 nm. NIR SPADs require cooling, which in the case of Ge SPADs dramatically reduces the quantum efficiency of the Ge at 1550 nm. Recently, however, advantages to working at 1310 nm have been suggested which combined with a need to increase quantum bit rates for quantum key distribution (QKD) motivates examination of Ge detectors performance at very high detection rates where InGaAs/InP does not perform as well. Presented in this paper are measurements of a commercially available Ge APD

  1. Characterizing the nature and variability of avalanche hazard in western Canada

    Science.gov (United States)

    Shandro, Bret; Haegeli, Pascal

    2018-04-01

    The snow and avalanche climate types maritime, continental and transitional are well established and have been used extensively to characterize the general nature of avalanche hazard at a location, study inter-seasonal and large-scale spatial variabilities and provide context for the design of avalanche safety operations. While researchers and practitioners have an experience-based understanding of the avalanche hazard associated with the three climate types, no studies have described the hazard character of an avalanche climate in detail. Since the 2009/2010 winter, the consistent use of Statham et al. (2017) conceptual model of avalanche hazard in public avalanche bulletins in Canada has created a new quantitative record of avalanche hazard that offers novel opportunities for addressing this knowledge gap. We identified typical daily avalanche hazard situations using self-organizing maps (SOMs) and then calculated seasonal prevalence values of these situations. This approach produces a concise characterization that is conducive to statistical analyses, but still provides a comprehensive picture that is informative for avalanche risk management due to its link to avalanche problem types. Hazard situation prevalence values for individual seasons, elevations bands and forecast regions provide unprecedented insight into the inter-seasonal and spatial variability of avalanche hazard in western Canada.

  2. Photodiode measurements in Nucte-II

    International Nuclear Information System (INIS)

    Machida, M.; Aramaki, E.A.; Takahashi, T.; Ohara, M.; Nogi, N.

    1989-01-01

    Direct measurements of light emission from plasma produced by a field reversed theta-pinch NUCTE-II have been performed by using a set of photodiode detectors. The analysis shows that the plasma light emission can be related to the bremsstrahlung radiation and it is used to identify η=2 rotational instability parameters as rotation direction, angular velocity, and radial and axial displacement of the plasma column. A rough estimate for the temporal behaviour of the electro temperature has also been obtained by using the photodiode signal together with He-Ne laser interferometer and flux excluded signals. (author) [pt

  3. Effects of SF$_{6}$ on the avalanche mode operation of a real-sized double-gap resistive plate chamber for the Compact Muon Solenoid experiment

    CERN Document Server

    Ahn Sung Hwan; Hong, B; Hong, S J; Ito, M; Kim, B I; Kim, J H; Kim, Y J; Kim, Y U; Koo, D G; Lee, H W; Lee, K B; Lee, K S; Lee, S J; Lim, J K; Moon, D H; Nam, S K; Park, S; Park, W J; Rhee, J T; Ryu, M S; Shim, H H; Sim, K S; Kang, T I

    2005-01-01

    We present the design and the test, results for a real-sized prototype resistive plate chamber by using cosmic-ray muons for the forward region of the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC). In particular, we investigate the effects of adding SF/sub 6/ to the gas mixture for the avalanche mode operation of a resistive plate chamber. A small fraction of SF/sub 6/ is very effective in suppressing streamer signals in a resistive plate chamber. The shapes of the muon detection efficiency and the muon cluster size remain similar, but are shifted to higher operating voltage by SF/sub 6/. The noise cluster rate and size are not influenced by SF/sub 6/.

  4. 75 MeV boron ion irradiation studies on Si PIN photodiodes

    Energy Technology Data Exchange (ETDEWEB)

    Prabhakara Rao, Y.P.; Praveen, K.C. [Department of Studies in Physics, University of Mysore, Manasagangotri, Mysore 570006 (India); Rejeena Rani, Y. [Integrated Circuits Division, Bharat Electronics Limited, Bangalore 560013, Karnataka (India); Tripathi, Ambuj [Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067 (India); Gnana Prakash, A.P., E-mail: gnanap@hotmail.com [Department of Studies in Physics, University of Mysore, Manasagangotri, Mysore 570006 (India)

    2013-12-01

    The highly sensitive silicon PIN photodiodes were fabricated to use in radiation environments. The Si PIN photodiodes are coated with 150 nm silicon dioxide (SiO{sub 2}) as anti-reflective (AR) coating. The presence of AR coating on the performance of irradiated PIN photodiodes is studied up to a total dose of 10 Mrad. The effects of 75 MeV boron (B{sup 5+}) ions and {sup 60}Co gamma radiation on the I–V, C–V and spectral responses of PIN photodiodes were studied systematically to understand the radiation tolerance of the devices. The 75 MeV B{sup 5+} irradiation results are compared with {sup 60}Co gamma irradiated results in the same dose range for 1 mm × 1 mm and 10 mm × 10 mm active area PIN photodiodes. The irradiation results show that the ion irradiated PIN photodiodes show more degradation when compared {sup 60}Co gamma irradiated devices. The irradiation results are presented in this paper and the possible mechanism behind the degradation of photodiodes is also discussed in the paper.

  5. Criticality and avalanches in neural networks

    International Nuclear Information System (INIS)

    Zare, Marzieh; Grigolini, Paolo

    2013-01-01

    Highlights: • Temporal criticality is used as criticality indicator. • The Mittag–Leffler function is proposed as a proper form of temporal complexity. • The distribution of avalanche size becomes scale free in the supercritical state. • The scale-free distribution of avalanche sizes is an epileptic manifestation. -- Abstract: Experimental work, both in vitro and in vivo, reveals the occurrence of neural avalanches with an inverse power law distribution in size and time duration. These properties are interpreted as an evident manifestation of criticality, thereby suggesting that the brain is an operating near criticality complex system: an attractive theoretical perspective that according to Gerhard Werner may help to shed light on the origin of consciousness. However, a recent experimental observation shows no clear evidence for power-law scaling in awake and sleeping brain of mammals, casting doubts on the assumption that the brain works at criticality. This article rests on a model proposed by our group in earlier publications to generate neural avalanches with the time duration and size distribution matching the experimental results on neural networks. We now refine the analysis of the time distance between consecutive firing bursts and observe the deviation of the corresponding distribution from the Poisson statistics, as the system moves from the non-cooperative to the cooperative regime. In other words, we make the assumption that the genuine signature of criticality may emerge from temporal complexity rather than from the size and time duration of avalanches. We argue that the Mittag–Leffler (ML) exponential function is a satisfactory indicator of temporal complexity, namely of the occurrence of non-Poisson and renewal events. The assumption that the onset of criticality corresponds to the birth of renewal non-Poisson events establishes a neat distinction between the ML function and the power law avalanches generating regime. We find that

  6. Geiger counters of gamma rays with a bismuth cathode

    International Nuclear Information System (INIS)

    Meunier, R.; Legrand, J.P.

    1953-01-01

    Geiger Muller counters present a lake of efficiency of some per cent, for the γ radiations. In the region 0,3 - 1 MeV, a substantial growth of their output can be obtained by a special construction of their cathode. In accordance with previous works, we constructed some counter of formed cathode by a pleated copper wire fencing covered of Bi by electrolysis. The successive modifications brought to a cylindrical conventional cathode in sheet metal of copper, that succeeds to this type of cathode, drive to an improvement of the output. (M.B.) [fr

  7. Wolfgang Geiger (17 July 1921 - 3 July 2000

    Directory of Open Access Journals (Sweden)

    Renata Boucher-Rodoni

    2000-08-01

    Full Text Available Wolfgang Geiger died on the 3rd July 2000, at the age of 79. He was born on July 17th 1921 in Biel; his mother died at his birth. His childhood was spent with his father, a well-known artist, partly in Ligerz, on Lake Biel, and partly in Porto Ronco in Ticino, on Lago Maggiore. After high school in Biel, he began his University studies, first at the Swiss Federal Institute of Technology in Zürich, then in Basel, where he studied under Professor A. Portmann. During his PhD a grant from the Janggen-Pöhn foundation enabled him to work for some months at the Institut des Pêches maritimes du Maroc, in Casablanca, with Dr. J .Furnestin. In 1953 he completed his PhD on teleost fish brain. His career as a biologist began in Bern at the Eidgenossische Inspektion für Fortwesen, Jagd und Fischerei. In 1962 he was appointed head assistant (chef des travaux at the University of Geneva, in the comparative anatomy and physiology laboratory (Dr H. J. Huggel, where he discovered the joys and the limitations of teaching. He was highly regarded as a lecturer and taught in a relaxed atmosphere of mutual respect and trust, much appreciated by his students. Professor Geiger was also the main organiser of field trips to Sète, on the French Mediterranean coast, where he was in his element living on the water. He went out on the trawlers with the students and introduced them enthusiastically to the marvels of sea fauna. He was happy during those field trips and had the knack of communicating his happiness to the students.

  8. Configurable Electronics with Low Noise and 14-bit Dynamic Range for Photodiode-based Photon Detectors

    CERN Document Server

    Müller, H; Yin, Z; Zhou, D; Cao, X; Li, Q; Liu, Y; Zou, F; Skaali, B; Awes, T C

    2006-01-01

    We describe the principles and measured performance characteristics of custom configurable 32-channel shaper/digitizer Front End Electronics (FEE) cards with 14-bit dynamic range for use with gain-adjustable photon detectors. The electronics has been designed for the PHOS calorimeter of ALICE with avalanche photodiode (APD) readout operated at -25 C ambient temperature and a signal shaping time of $1 {\\mu}s$. The electronics has also been adopted by the EMCal detector of ALICE with the same APD readout, but operated at an ambient temperature of +20 C and with a shaping time of 100ns. The CR-RC2 signal shapers on the FEE cards are implemented in discrete logic on a 10-layer board with two shaper sections for each input channel. The two shaper sections with gain ratio of 16:1 are digitized by 10-bit ADCs and provide an effective dynamic range of 14 bits. Gain adjustment for each individual APD is available through 32 bias voltage control registers of 10-bit range. The fixed gains and shaping times of the pole-z...

  9. Cherenkov luminescence measurements with digital silicon photomultipliers: a feasibility study

    Energy Technology Data Exchange (ETDEWEB)

    Ciarrocchi, Esther; Belcari, Nicola; Guerra, Alberto Del [Department of Physics, University of Pisa, Pisa (Italy); INFN, section of Pisa, Pisa (Italy); Cherry, Simon R. [Department of Biomedical Engineering, University of California, Davis, CA (United States); Lehnert, Adrienne; Hunter, William C. J.; McDougald, Wendy; Miyaoka, Robert S.; Kinahan, Paul E. [Department of Radiology, University of Washington, Seattle, WA (United States)

    2015-11-16

    A feasibility study was done to assess the capability of digital silicon photomultipliers to measure the Cherenkov luminescence emitted by a β source. Cherenkov luminescence imaging (CLI) is possible with a charge coupled device (CCD) based technology, but a stand-alone technique for quantitative activity measurements based on Cherenkov luminescence has not yet been developed. Silicon photomultipliers (SiPMs) are photon counting devices with a fast impulse response and can potentially be used to quantify β-emitting radiotracer distributions by CLI. In this study, a Philips digital photon counting (PDPC) silicon photomultiplier detector was evaluated for measuring Cherenkov luminescence. The PDPC detector is a matrix of avalanche photodiodes, which were read one at a time in a dark count map (DCM) measurement mode (much like a CCD). This reduces the device active area but allows the information from a single avalanche photodiode to be preserved, which is not possible with analog SiPMs. An algorithm to reject the noisiest photodiodes and to correct the measured count rate for the dark current was developed. The results show that, in DCM mode and at (10–13) °C, the PDPC has a dynamic response to different levels of Cherenkov luminescence emitted by a β source and transmitted through an opaque medium. This suggests the potential for this approach to provide quantitative activity measurements. Interestingly, the potential use of the PDPC in DCM mode for direct imaging of Cherenkov luminescence, as a opposed to a scalar measurement device, was also apparent. We showed that a PDPC tile in DCM mode is able to detect and image a β source through its Cherenkov radiation emission. The detector’s dynamic response to different levels of radiation suggests its potential quantitative capabilities, and the DCM mode allows imaging with a better spatial resolution than the conventional event-triggered mode. Finally, the same acquisition procedure and data processing could

  10. Cherenkov luminescence measurements with digital silicon photomultipliers: a feasibility study

    International Nuclear Information System (INIS)

    Ciarrocchi, Esther; Belcari, Nicola; Guerra, Alberto Del; Cherry, Simon R.; Lehnert, Adrienne; Hunter, William C. J.; McDougald, Wendy; Miyaoka, Robert S.; Kinahan, Paul E.

    2015-01-01

    A feasibility study was done to assess the capability of digital silicon photomultipliers to measure the Cherenkov luminescence emitted by a β source. Cherenkov luminescence imaging (CLI) is possible with a charge coupled device (CCD) based technology, but a stand-alone technique for quantitative activity measurements based on Cherenkov luminescence has not yet been developed. Silicon photomultipliers (SiPMs) are photon counting devices with a fast impulse response and can potentially be used to quantify β-emitting radiotracer distributions by CLI. In this study, a Philips digital photon counting (PDPC) silicon photomultiplier detector was evaluated for measuring Cherenkov luminescence. The PDPC detector is a matrix of avalanche photodiodes, which were read one at a time in a dark count map (DCM) measurement mode (much like a CCD). This reduces the device active area but allows the information from a single avalanche photodiode to be preserved, which is not possible with analog SiPMs. An algorithm to reject the noisiest photodiodes and to correct the measured count rate for the dark current was developed. The results show that, in DCM mode and at (10–13) °C, the PDPC has a dynamic response to different levels of Cherenkov luminescence emitted by a β source and transmitted through an opaque medium. This suggests the potential for this approach to provide quantitative activity measurements. Interestingly, the potential use of the PDPC in DCM mode for direct imaging of Cherenkov luminescence, as a opposed to a scalar measurement device, was also apparent. We showed that a PDPC tile in DCM mode is able to detect and image a β source through its Cherenkov radiation emission. The detector’s dynamic response to different levels of radiation suggests its potential quantitative capabilities, and the DCM mode allows imaging with a better spatial resolution than the conventional event-triggered mode. Finally, the same acquisition procedure and data processing could

  11. Influence of Temperature Variation on Optical Receiver Sensitivity and its Compensation

    Directory of Open Access Journals (Sweden)

    A. Prokes

    2007-09-01

    Full Text Available In the paper, the influence of temperature variation on the sensitivity of an avalanche-photodiode-based optical receiver applied in the free space optical communication link is discussed. Communication systems of this type are exposed to a wide range of operating temperatures, which markedly affect many photodiode and preamplifier parameters. The paper presents a receiver sensitivity calculation, taking into consideration the temperature dependence of avalanche photodiode gain, excess noise factor, dark current and thermal noise of preamplifier resistances, and describes the compensation of temperature effects on photodiode gain based on a corresponding change in the reverse voltage applied to the diode. The calculations are demonstrated on the connection of a small-area silicon APD operating in the wavelength range from 820 to 1150 nm with a transimpedance preamplifier using a bipolar junction transistor.

  12. A Study of Photoreceivers for Free-Space, Analog, Intensity-Modulated, Direct-Detection Optical Links Operating at Microwave Frequencies

    Science.gov (United States)

    2010-09-10

    photodiode with internal resistor followed by a high-gain RF amplifier , and c) a p-i-n photodiode followed by a transimpedance amplifier (TIA). We...gain, RF electrical amplifier ; and 3) a p-i-n photodiode followed by a transimpedance amplifier . Finally, we perform calculations to predict the...common photoreceiver is a p-i-n or avalanche photodiode with a built-in transimpedance amplifier (TIA) and often incorporating automatic gain control

  13. Analytical models of probability distribution and excess noise factor of solid state photomultiplier signals with crosstalk

    International Nuclear Information System (INIS)

    Vinogradov, S.

    2012-01-01

    Silicon Photomultipliers (SiPM), also called Solid State Photomultipliers (SSPM), are based on Geiger mode avalanche breakdown that is limited by a strong negative feedback. An SSPM can detect and resolve single photons due to the high gain and ultra-low excess noise of avalanche multiplication in this mode. Crosstalk and afterpulsing processes associated with the high gain introduce specific excess noise and deteriorate the photon number resolution of the SSPM. The probabilistic features of these processes are widely studied because of its significance for the SSPM design, characterization, optimization and application, but the process modeling is mostly based on Monte Carlo simulations and numerical methods. In this study, crosstalk is considered to be a branching Poisson process, and analytical models of probability distribution and excess noise factor (ENF) of SSPM signals based on the Borel distribution as an advance on the geometric distribution models are presented and discussed. The models are found to be in a good agreement with the experimental probability distributions for dark counts and a few photon spectrums in a wide range of fired pixels number as well as with observed super-linear behavior of crosstalk ENF.

  14. Indirect flat-panel detector with avalanche gain: Fundamental feasibility investigation for SHARP-AMFPI (scintillator HARP active matrix flat panel imager)

    International Nuclear Information System (INIS)

    Zhao Wei; Li Dan; Reznik, Alla; Lui, B.J.M.; Hunt, D.C.; Rowlands, J.A.; Ohkawa, Yuji; Tanioka, Kenkichi

    2005-01-01

    An indirect flat-panel imager (FPI) with avalanche gain is being investigated for low-dose x-ray imaging. It is made by optically coupling a structured x-ray scintillator CsI(Tl) to an amorphous selenium (a-Se) avalanche photoconductor called HARP (high-gain avalanche rushing photoconductor). The final electronic image is read out using an active matrix array of thin film transistors (TFT). We call the proposed detector SHARP-AMFPI (scintillator HARP active matrix flat panel imager). The advantage of the SHARP-AMFPI is its programmable gain, which can be turned on during low dose fluoroscopy to overcome electronic noise, and turned off during high dose radiography to avoid pixel saturation. The purpose of this paper is to investigate the important design considerations for SHARP-AMFPI such as avalanche gain, which depends on both the thickness d Se and the applied electric field E Se of the HARP layer. To determine the optimal design parameter and operational conditions for HARP, we measured the E Se dependence of both avalanche gain and optical quantum efficiency of an 8 μm HARP layer. The results were used in a physical model of HARP as well as a linear cascaded model of the FPI to determine the following x-ray imaging properties in both the avalanche and nonavalanche modes as a function of E Se : (1) total gain (which is the product of avalanche gain and optical quantum efficiency); (2) linearity; (3) dynamic range; (4) gain nonuniformity resulting from thickness nonuniformity; and (5) effects of direct x-ray interaction in HARP. Our results showed that a HARP layer thickness of 8 μm can provide adequate avalanche gain and sufficient dynamic range for x-ray imaging applications to permit quantum limited operation over the range of exposures needed for radiography and fluoroscopy

  15. First approximations in avalanche model validations using seismic information

    Science.gov (United States)

    Roig Lafon, Pere; Suriñach, Emma; Bartelt, Perry; Pérez-Guillén, Cristina; Tapia, Mar; Sovilla, Betty

    2017-04-01

    Avalanche dynamics modelling is an essential tool for snow hazard management. Scenario based numerical modelling provides quantitative arguments for decision-making. The software tool RAMMS (WSL Institute for Snow and Avalanche Research SLF) is one such tool, often used by government authorities and geotechnical offices. As avalanche models improve, the quality of the numerical results will depend increasingly on user experience on the specification of input (e.g. release and entrainment volumes, secondary releases, snow temperature and quality). New model developments must continue to be validated using real phenomena data, for improving performance and reliability. The avalanches group form University of Barcelona (RISKNAT - UB), has studied the seismic signals generated from avalanches since 1994. Presently, the group manages the seismic installation at SLF's Vallée de la Sionne experimental site (VDLS). At VDLS the recorded seismic signals can be correlated to other avalanche measurement techniques, including both advanced remote sensing methods (radars, videogrammetry) and obstacle based sensors (pressure, capacitance, optical sender-reflector barriers). This comparison between different measurement techniques allows the group to address the question if seismic analysis can be used alone, on more additional avalanche tracks, to gain insight and validate numerical avalanche dynamics models in different terrain conditions. In this study, we aim to add the seismic data as an external record of the phenomena, able to validate RAMMS models. The seismic sensors are considerable easy and cheaper to install than other physical measuring tools, and are able to record data from the phenomena in every atmospheric conditions (e.g. bad weather, low light, freezing make photography, and other kind of sensors not usable). With seismic signals, we record the temporal evolution of the inner and denser parts of the avalanche. We are able to recognize the approximate position

  16. Anthropogenic effect on avalanche and debris flow activity

    OpenAIRE

    S. A. Sokratov; Yu. G. Seliverstov; A. L. Shnyparkov; K. P. Koltermann

    2013-01-01

    The paper presents examples of the change in snow avalanches and debris flows activity due to the anthropogenic pressure on vegetation and relief. The changes in dynamical characteristics of selected snow avalanches and debris flows due to the anthropogenic activity are quantified. The conclusion is made that the anthropogenic effects on the snow avalanches and debris flows activity are more pronounced than the possible effects of the climate change. The necessity is expressed on the unavoida...

  17. Dealing with the white death: avalanche risk management for traffic routes.

    Science.gov (United States)

    Rheinberger, Christoph M; Bründl, Michael; Rhyner, Jakob

    2009-01-01

    This article discusses mitigation strategies to protect traffic routes from snow avalanches. Up to now, mitigation of snow avalanches on many roads and railways in the Alps has relied on avalanche sheds, which require large initial investments resulting in high opportunity costs. Therefore, avalanche risk managers have increasingly adopted organizational mitigation measures such as warning systems and closure policies instead. The effectiveness of these measures is, however, greatly dependent on human decisions. In this article, we present a method for optimizing avalanche mitigation for traffic routes in terms of both their risk reduction impact and their net benefit to society. First, we introduce a generic framework for assessing avalanche risk and for quantifying the impact of mitigation. This allows for sound cost-benefit comparisons between alternative mitigation strategies. Second, we illustrate the framework with a case study from Switzerland. Our findings suggest that site-specific characteristics of avalanche paths, as well as the economic importance of a traffic route, are decisive for the choice of optimal mitigation strategies. On routes endangered by few avalanche paths with frequent avalanche occurrences, structural measures are most efficient, whereas reliance on organizational mitigation is often the most appropriate strategy on routes endangered by many paths with infrequent or fuzzy avalanche risk. Finally, keeping a traffic route open may be very important for tourism or the transport industry. Hence, local economic value may promote the use of a hybrid strategy that combines organizational and structural measures to optimize the resource allocation of avalanche risk mitigation.

  18. Statistics of Electron Avalanches and Streamers

    Directory of Open Access Journals (Sweden)

    T. Ficker

    2007-01-01

    Full Text Available We have studied the severe systematic deviations of populations of electron avalanches from the Furry distribution, which has been held to be the statistical law corresponding to them, and a possible explanation has been sought. A  new theoretical concept based on fractal avalanche multiplication has been proposed and is shown to be a convenient candidate for explaining these deviations from Furry statistics. 

  19. Transient events in bright debris discs: Collisional avalanches revisited

    Science.gov (United States)

    Thebault, P.; Kral, Q.

    2018-01-01

    Context. A collisional avalanche is set off by the breakup of a large planetesimal, releasing vast amounts of small unbound grains that enter a debris disc located further away from the star, triggering there a collisional chain reaction that could potentially create detectable transient structures. Aims: We investigate this mechanism, using for the first time a fully self-consistent code coupling dynamical and collisional evolutions. We also quantify for the first time the photometric evolution of the system and investigate whether or not avalanches could explain the short-term luminosity variations recently observed in some extremely bright debris discs. Methods: We use the state-of-the-art LIDT-DD code. We consider an avalanche-favoring A6V star, and two set-ups: a "cold disc" case, with a dust release at 10 au and an outer disc extending from 50 to 120 au, and a "warm disc" case with the release at 1 au and a 5-12 au outer disc. We explore, in addition, two key parameters: the density (parameterized by its optical depth τ) of the main outer disc and the amount of dust released by the initial breakup. Results: We find that avalanches could leave detectable structures on resolved images, for both "cold" and "warm" disc cases, in discs with τ of a few 10-3, provided that large dust masses (≳1020-5 × 1022 g) are initially released. The integrated photometric excess due to an avalanche is relatively limited, less than 10% for these released dust masses, peaking in the λ 10-20 μm domain and becoming insignificant beyond 40-50 μm. Contrary to earlier studies, we do not obtain stronger avalanches when increasing τ to higher values. Likewise, we do not observe a significant luminosity deficit, as compared to the pre-avalanche level, after the passage of the avalanche. These two results concur to make avalanches an unlikely explanation for the sharp luminosity drops observed in some extremely bright debris discs. The ideal configuration for observing an

  20. Efficient Sub-Bandgap Light Absorption and Signal Amplification in Silicon Photodetectors

    Science.gov (United States)

    Liu, Yu-Hsin

    This thesis focuses on two areas in silicon photodetectors, the first being enhancing the sub-bandgap light absorption of IR wavelenghts in silicon, and the second being intrinsic signal amplification in silicon photodetectors. Both of these are achieved using heavily doped p-n junction devices which create localized states that relax the k-selection rule of indirect bandgap material. The probability of transitions between impurity band and the conduction/valence band would be much more efficient than the one between band-to-band transition. The waveguide-coupled epitaxial p-n photodetector was demonstrated for 1310 nm wavelength detection. Incorporated with the Franz-Keldysh effect and the quasi-confined epitaxial layer design, an absorption coefficient around 10 cm-1 has been measured and internal quantum efficiency nearly 100% at -2.5V. The absorption coefficient is calculated from the wave function of the electron and hole in p-n diode. The heavily doped impurity wave function can be formulated as a delta function, and the quasi-confined conduction band energy states, and the wave function on each level can be obtained from the Silvaco software. The calculated theoretical absorption coefficient increases with the increasing applied bias and the doping concentration, which matches the experimental results. To solve the issues of large excess noise and high operation bias for avalanche photodiodes based on impact ionization, I presented a detector using the Cycling Excitation Process (CEP) for signal amplification. This can be realized in a heavily doped and highly compensated Si p-n junction, showing ultra high gain about 3000 at very low bias (<4 V), and possessing an intrinsic, phonon-mediated regulation process to keep the device stable without any quenching device required in today's Geiger-mode avalanche detectors. The CEP can be formulated with the rate equations in conduction bands and impurity states. The gain expression, which is a function of the

  1. Snow Avalanche Disturbance Ecology: Examples From the San Juan Mountains, Colorado.

    Science.gov (United States)

    Simonson, S.; Fassnacht, S. R.

    2008-12-01

    We evaluated landscape ecology approaches to characterize snow avalanche paths based on patterns of plant species composition and evidence of disturbance. Historical records of avalanche incidents, patterns in the annual growth layers of woody plants, and distributions of plant species can be used to quantify and map the frequency and magnitude of snow slide events. Near Silverton, Colorado, a series of snow storms in January of 2005 resulted in many avalanche paths running full track at 30 and 100 year return frequency. Many avalanches cut fresh trimlines, widening their tracks by uprooting, stripping, and breaking mature trees. Powerful avalanches deposited massive piles of snow, rocks, and woody debris in their runout zones. We used cross-section discs and cores of representative downed trees to detect dendro-ecological signals of past snow avalanche disturbance. Avalanche signals included impact scars from the moving snow and associated wind blast, relative width of annual growth rings, and development of reaction wood in response to tilting. Initial measurements of plant diversity and disturbance along the elevation gradient of an avalanche path near Silverton indicate that avalanche activity influences patterns of forest cover, contributes to the high local plant species diversity, and provides opportunities for new seedling establishment.

  2. SNOW AVALANCHE ACTIVITY IN PARÂNG SKI AREA REVEALED BY TREE-RINGS

    Directory of Open Access Journals (Sweden)

    F. MESEȘAN

    2014-11-01

    Full Text Available Snow Avalanche Activity in Parâng Ski Area Revealed by Tree-Rings. Snow avalanches hold favorable conditions to manifest in Parâng Mountains but only one event is historically known, without destructive impact upon infrastructure or fatalities and this region wasn’t yet the object of avalanche research. The existing ski infrastructure of Parâng resort located in the west of Parâng Mountains is proposed to be extended in the steep slopes of subalpine area. Field evidence pinpoints that these steep slopes were affected by snow avalanches in the past. In this study we analyzed 11 stem discs and 31 increment cores extracted from 22 spruces (Picea abies (L. Karst impacted by avalanches, in order to obtain more information about past avalanches activity. Using the dendrogeomorphological approach we found 13 avalanche events that occurred along Scărița avalanche path, since 1935 until 2012, nine of them produced in the last 20 years. The tree-rings data inferred an intense snow avalanche activity along this avalanche path. This study not only calls for more research in the study area but also proves that snow avalanches could constitute an important restrictive factor for the tourism infrastructure and related activities in the area. It must be taken into consideration by the future extension of tourism infrastructure. Keywords: snow avalanche, Parâng Mountains, dendrogeomorphology, ski area.

  3. A small animal PET based on GAPDs and charge signal transmission approach for hybrid PET-MR imaging

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Jihoon; Choi, Yong; Hong, Key Jo; Hu, Wei; Jung, Jin Ho; Huh, Yoonsuk [Department of Electronic Engineering, Sogang University, 1 Shinsu-Dong, Mapo-Gu, Seoul 121-742 (Korea, Republic of); Kim, Byung-Tae, E-mail: ychoi.image@gmail.com [Department of Nuclear Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, 50 Ilwon-Dong, Gangnam-Gu, Seoul 135-710 (Korea, Republic of)

    2011-08-15

    Positron emission tomography (PET) employing Geiger-mode avalanche photodiodes (GAPDs) and charge signal transmission approach was developed for small animal imaging. Animal PET contained 16 LYSO and GAPD detector modules that were arranged in a 70 mm diameter ring with an axial field of view of 13 mm. The GAPDs charge output signals were transmitted to a preamplifier located remotely using 300 cm flexible flat cables. The position decoder circuits (PDCs) were used to multiplex the PET signals from 256 to 4 channels. The outputs of the PDCs were digitized and further-processed in the data acquisition unit. The cross-compatibilities of the PET detectors and MRI were assessed outside and inside the MRI. Experimental studies of the developed full ring PET were performed to examine the spatial resolution and sensitivity. Phantom and mouse images were acquired to examine the imaging performance. The mean energy and time resolution of the PET detector were 17.6% and 1.5 ns, respectively. No obvious degradation on PET and MRI was observed during simultaneous PET-MRI data acquisition. The measured spatial resolution and sensitivity at the CFOV were 2.8 mm and 0.7%, respectively. In addition, a 3 mm diameter line source was clearly resolved in the hot-sphere phantom images. The reconstructed transaxial PET images of the mouse brain and tumor displaying the glucose metabolism patterns were imaged well. These results demonstrate GAPD and the charge signal transmission approach can allow the development of high performance small animal PET with improved MR compatibility.

  4. A method to stabilize the temperature dependent performance of G-APD arrays

    Energy Technology Data Exchange (ETDEWEB)

    Huh, Yoonsuk [Molecular Imaging Research and Education (MiRe) Laboratory, Department of Electronic Engineering, Sogang University, Seoul (Korea, Republic of); Sungkyunkwan University, School of Medicine, Seoul (Korea, Republic of); Choi, Yong; Ho Jung, Jin; Jung, Jiwoong [Molecular Imaging Research and Education (MiRe) Laboratory, Department of Electronic Engineering, Sogang University, Seoul (Korea, Republic of)

    2015-02-01

    This paper presents a compensation method to stabilize the temperature dependent performance of Geiger-mode Avalanche Photodiode (G-APD) arrays for Positron Emission Tomography (PET). The compensation method is used to identify the bias voltage range that provides stable performance even at different temperatures using the G-APD’s characteristics, and to control the photo-peak variation as a function of temperature using the preamplifier gain within the identified bias voltage range. A pair of G-APD detectors and temperature sensors were located in the temperature chamber and the preamplifiers which can control the gain of the detectors using the digital potentiometer were positioned outside the chamber. The performance of the G-APD detector, especially energy resolution and coincidence timing resolution, was characterized as a function of bias voltage at different temperatures from 20 °C to 40 °C at 5 °C increments; the energy resolution, coincidence timing resolution, and photo-peak position of all channels of G-APD PET detectors before and after the preamplifier gain correction were then measured and compared. The results of this study demonstrated that the optimal bias voltage range providing the good energy and coincidence timing resolution, 12.1±1.2% and 1.30±0.09 ns, respectively, could be identified at the temperature range and the photo-peak variation and the performance at different temperatures could be stabilized by adjusting the preamplifier gain within the identified bias voltage range. We concluded the proposed method to be reliable and useful for the development of the PET system using G-APD arrays.

  5. Investigations of single-electron avalanches in a proportional drift tube

    International Nuclear Information System (INIS)

    Anderson, W.S.; Armitage, J.C.; Chevreau, P.; Heinrich, J.G.; Lu, C.; McDonald, I.; McDonald, K.T.; Miller, B.; Secrest, D.; Weckel, J.

    1990-01-01

    Detailed information on single-electron drift and avalanche behavior has a basic interest in an investigation of gas-chamber performance. Its timing, avalanche distribution, attachment by the working gas mixtures, etc., provide various criteria for choosing the best suitable gas mixture under a specific experimental circumstance. Investigations of single-electron avalanches in a proportional drift tube have been carried out with a pulsed N 2 laser. The study consists of two aspects: timing properties, and fluctuations in the gas avalanche

  6. Computational and experimental progress on laser-activated gas avalanche switches for broadband, high-power electromagnetic pulse generation

    International Nuclear Information System (INIS)

    Mayhall, D.J.; Yee, J.H.; Villa, F.

    1991-01-01

    This paper discusses the gas avalanche switch, a high-voltage, picosecond-speed switch, which has been proposed. The basic switch consists of pulse-charged electrodes, immersed in a high-pressure gas. An avalanche discharge is induced in the gas between the electrodes by ionization from a picosecond-scale laser pulse. The avalanching electrons move toward the anode, causing the applied voltage to collapse in picoseconds. This voltage collapse, if rapid enough, generates electromagnetic waves. A two-dimensional (2D), finite difference computer code solves Maxwell's equations for transverse magnetic modes for rectilinear electrodes between parallel plate conductors, along with electron conservation equations for continuity, momentum, and energy. Collision frequencies for ionization and momentum and energy transfer to neutral molecules are assumed to scale linearly with neutral pressure. Electrode charging and laser-driven electron deposition are assumed to be instantaneous. Code calculations are done for a pulse generator geometry, consisting of an 0.7 mm wide by 0.8 mm high, beveled, rectangular center electrode between grounded parallel plates at 2 mm spacing in air

  7. The Use of Self-scanned Silicon Photodiode Arrays for Astronomical Spectrophotometry

    Science.gov (United States)

    Cochran, A. L.

    1984-01-01

    The use of a Reticon self scanned silicon photodiode array for precision spectrophotometry is discussed. It is shown that internal errors are + or - 0.003 mag. Observations obtained with a photodiode array are compared with observations obtained with other types of detectors with agreement, from 3500 A to 10500 A, of 1%. The photometric properties of self scanned photodiode arrays are discussed. Potential pitfalls are given.

  8. Development and verification of signal processing system of avalanche photo diode for the active shields onboard ASTRO-H

    Energy Technology Data Exchange (ETDEWEB)

    Ohno, M., E-mail: ohno@hep01.hepl.hiroshima-u.ac.jp [Department of Physical Sciences, Hiroshima University, Hiroshima 739-8526 (Japan); Kawano, T.; Edahiro, I.; Shirakawa, H.; Ohashi, N.; Okada, C.; Habata, S.; Katsuta, J.; Tanaka, Y.; Takahashi, H.; Mizuno, T.; Fukazawa, Y. [Department of Physical Sciences, Hiroshima University, Hiroshima 739-8526 (Japan); Murakami, H.; Kobayashi, S.; Miyake, K.; Ono, K.; Kato, Y.; Furuta, Y.; Murota, Y.; Okuda, K. [Department of Physics, University of Tokyo, Tokyo 113-0033 (Japan); and others

    2016-09-21

    The hard X-ray Imager and Soft Gamma-ray Detector onboard ASTRO-H demonstrate high sensitivity to hard X-ray (5–80 keV) and soft gamma-rays (60–600 keV), respectively. To reduce the background, both instruments are actively shielded by large, thick Bismuth Germanate scintillators. We have developed the signal processing system of the avalanche photodiode in the BGO active shields and have demonstrated its effectiveness after assembly in the flight model of the HXI/SGD sensor and after integration into the satellite. The energy threshold achieved is about 150 keV and anti-coincidence efficiency for cosmic-ray events is almost 100%. Installed in the BGO active shield, the developed signal processing system successfully reduces the room background level of the main detector. - Highlights: • A detail of development of signal processing system for ASTRO-H is presented. • Digital filer with FPGA instead of discrete analog circuit is applied. • Expected performance is verified after integration of the satellite.

  9. Terrain Classification of Norwegian Slab Avalanche Accidents

    Science.gov (United States)

    Hallandvik, Linda; Aadland, Eivind; Vikene, Odd Lennart

    2016-01-01

    It is difficult to rely on snow conditions, weather, and human factors when making judgments about avalanche risk because these variables are dynamic and complex; terrain, however, is more easily observed and interpreted. Therefore, this study aimed to investigate (1) the type of terrain in which historical fatal snow avalanche accidents in Norway…

  10. Low-energy X-ray and gamma spectrometry using silicon photodiodes

    International Nuclear Information System (INIS)

    Silva, Iran Jose Oliveira da

    2000-08-01

    The use of semiconductor detectors for radiation detection has increased in recent years due to advantages they present in comparison to other types of detectors. As the working principle of commercially available photodiodes is similar to the semiconductor detector, this study was carried out to evaluate the use of Si photodiodes for low energy x-ray and gamma spectrometry. The photodiodes investigated were SFH-205, SFH-206, BPW-34 and XRA-50 which have the following characteristics: active area of 0,07 cm 2 and 0,25 cm 2 , thickness of the depletion ranging from 100 to 200 μm and junction capacitance of 72 pF. The photodiode was polarized with a reverse bias and connected to a charge sensitive pre-amplifier, followed by a amplifier and multichannel pulse analyzer. Standard radiation source used in this experiment were 241 Am, 109 Cd, 57 Co and 133 Ba. The X-ray fluorescence of lead and silver were also measured through K- and L-lines. All the measurements were made with the photodiodes at room temperature.The results show that the responses of the photodiodes very linear by the x-ray energy and that the energy resolution in FWHM varied between 1.9 keV and 4.4 keV for peaks corresponding to 11.9 keV to 59 keV. The BPW-34 showed the best energy resolution and the lower dark current. The full-energy peak efficiency was also determined and it was observed that the peak efficiency decreases rapidly above 50 keV. The resolution and efficiency are similar to the values obtained with other semiconductor detectors, evidencing that the photodiodes used in that study can be used as a good performance detector for low energy X-ray and gamma spectrometry. (author)

  11. Discrimination capability of avalanche counters detecting different ionizing particles

    International Nuclear Information System (INIS)

    Prete, G.; Viesti, G.; Padua Univ.

    1985-01-01

    The discrimination capability of avalanche counters to detect different ionizing particles has been studied using a 252 Cf source. Pulse height, pulse-height resolution and timing properties have been measured as a function of the reduced applied voltage for parallel-plate and parallel-grid avalanche counters. At the highest applied voltages, space charge effects shift the pulse-height signal of the avalanche counter away from being linearly proportional to the stopping power of the detected particles and cause the pulse-height resolution to deteriorate. To optimize the avalanche counter capability, without loss of time resolution, it appears better to operate the detector at voltages well below the breakdown threshold. Measurements with 32 S ions are also reported. (orig.)

  12. InGaAs/InAlAs single photon avalanche diode for 1550 nm photons.

    Science.gov (United States)

    Meng, Xiao; Xie, Shiyu; Zhou, Xinxin; Calandri, Niccolò; Sanzaro, Mirko; Tosi, Alberto; Tan, Chee Hing; Ng, Jo Shien

    2016-03-01

    A single photon avalanche diode (SPAD) with an InGaAs absorption region, and an InAlAs avalanche region was designed and demonstrated to detect 1550 nm wavelength photons. The characterization included leakage current, dark count rate and single photon detection efficiency as functions of temperature from 210 to 294 K. The SPAD exhibited good temperature stability, with breakdown voltage dependence of approximately 45 mV K(-1). Operating at 210 K and in a gated mode, the SPAD achieved a photon detection probability of 26% at 1550 nm with a dark count rate of 1 × 10(8) Hz. The time response of the SPAD showed decreasing timing jitter (full width at half maximum) with increasing overbias voltage, with 70 ps being the smallest timing jitter measured.

  13. Statistical evaluation of waveform collapse reveals scale-free properties of neuronal avalanches

    Directory of Open Access Journals (Sweden)

    Aleena eShaukat

    2016-04-01

    Full Text Available Neural avalanches are a prominent form of brain activity characterized by network-wide bursts whose statistics follow a power-law distribution with a slope near 3/2. Recent work suggests that avalanches of different durations can be rescaled and thus collapsed together. This collapse mirrors work in statistical physics where it is proposed to form a signature of systems evolving in a critical state. However, no rigorous statistical test has been proposed to examine the degree to which neuronal avalanches collapse together. Here, we describe a statistical test based on functional data analysis, where raw avalanches are first smoothed with a Fourier basis, then rescaled using a time-warping function. Finally, an F ratio test combined with a bootstrap permutation is employed to determine if avalanches collapse together in a statistically reliable fashion. To illustrate this approach, we recorded avalanches from cortical cultures on multielectrode arrays as in previous work. Analyses show that avalanches of various durations can be collapsed together in a statistically robust fashion. However, a principal components analysis revealed that the offset of avalanches resulted in marked variance in the time-warping function, thus arguing for limitations to the strict fractal nature of avalanche dynamics. We compared these results with those obtained from cultures treated with an AMPA/NMDA receptor antagonist (APV/DNQX, which yield a power-law of avalanche durations with a slope greater than 3/2. When collapsed together, these avalanches showed marked misalignments both at onset and offset time-points. In sum, the proposed statistical evaluation suggests the presence of scale-free avalanche waveforms and constitutes an avenue for examining critical dynamics in neuronal systems.

  14. Pulse-periodic generation of supershort avalanche electron beams and X-ray emission

    Science.gov (United States)

    Baksht, E. Kh.; Burachenko, A. G.; Erofeev, M. V.; Tarasenko, V. F.

    2014-05-01

    Pulse-periodic generation of supershort avalanche electron beams (SAEBs) and X-ray emission in nitrogen, as well as the transition from a single-pulse mode to a pulse-periodic mode with a high repetition frequency, was studied experimentally. It is shown that, in the pulse-periodic mode, the full width at halfmaximum of the SAEB is larger and the decrease rate of the gap voltage is lower than those in the single-pulse mode. It is found that, when the front duration of the voltage pulse at a nitrogen pressure of 90 Torr decreases from 2.5 to 0.3 ns, the X-ray exposure dose in the pulse-periodic mode increases by more than one order of magnitude and the number of SAEB electrons also increases. It is shown that, in the pulse-periodic mode of a diffuse discharge, gas heating in the discharge gap results in a severalfold increase in the SAEB amplitude (the number of electrons in the beam). At a generator voltage of 25 kV, nitrogen pressure of 90 Torr, and pulse repetition frequency of 3.5 kHz, a runaway electron beam was detected behind the anode foil.

  15. Avalanche localization and its effects in proportional counters

    International Nuclear Information System (INIS)

    Fischer, J.; Okuno, H.; Walenta, A.H.

    1977-11-01

    Avalanche development around the anode wire in a gas proportional counter is investigated. In the region of proportional gas amplification, the avalanche is found to be well localized on one side of the anode wire, where the electrons arrive along the field lines from the point of primary ionization. Induced signals on electrodes surrounding the anode wire are used to measure the azimuthal position of the avalanche on the anode wire. Practical applications of the phenomena such as left-right assignment in drift chambers and measurement of the angular direction of the primary ionization electrons drifting towards the anode wire are discussed

  16. Automated identification of potential snow avalanche release areas based on digital elevation models

    Directory of Open Access Journals (Sweden)

    Y. Bühler

    2013-05-01

    Full Text Available The identification of snow avalanche release areas is a very difficult task. The release mechanism of snow avalanches depends on many different terrain, meteorological, snowpack and triggering parameters and their interactions, which are very difficult to assess. In many alpine regions such as the Indian Himalaya, nearly no information on avalanche release areas exists mainly due to the very rough and poorly accessible terrain, the vast size of the region and the lack of avalanche records. However avalanche release information is urgently required for numerical simulation of avalanche events to plan mitigation measures, for hazard mapping and to secure important roads. The Rohtang tunnel access road near Manali, Himachal Pradesh, India, is such an example. By far the most reliable way to identify avalanche release areas is using historic avalanche records and field investigations accomplished by avalanche experts in the formation zones. But both methods are not feasible for this area due to the rough terrain, its vast extent and lack of time. Therefore, we develop an operational, easy-to-use automated potential release area (PRA detection tool in Python/ArcGIS which uses high spatial resolution digital elevation models (DEMs and forest cover information derived from airborne remote sensing instruments as input. Such instruments can acquire spatially continuous data even over inaccessible terrain and cover large areas. We validate our tool using a database of historic avalanches acquired over 56 yr in the neighborhood of Davos, Switzerland, and apply this method for the avalanche tracks along the Rohtang tunnel access road. This tool, used by avalanche experts, delivers valuable input to identify focus areas for more-detailed investigations on avalanche release areas in remote regions such as the Indian Himalaya and is a precondition for large-scale avalanche hazard mapping.

  17. Automated identification of potential snow avalanche release areas based on digital elevation models

    Science.gov (United States)

    Bühler, Y.; Kumar, S.; Veitinger, J.; Christen, M.; Stoffel, A.; Snehmani

    2013-05-01

    The identification of snow avalanche release areas is a very difficult task. The release mechanism of snow avalanches depends on many different terrain, meteorological, snowpack and triggering parameters and their interactions, which are very difficult to assess. In many alpine regions such as the Indian Himalaya, nearly no information on avalanche release areas exists mainly due to the very rough and poorly accessible terrain, the vast size of the region and the lack of avalanche records. However avalanche release information is urgently required for numerical simulation of avalanche events to plan mitigation measures, for hazard mapping and to secure important roads. The Rohtang tunnel access road near Manali, Himachal Pradesh, India, is such an example. By far the most reliable way to identify avalanche release areas is using historic avalanche records and field investigations accomplished by avalanche experts in the formation zones. But both methods are not feasible for this area due to the rough terrain, its vast extent and lack of time. Therefore, we develop an operational, easy-to-use automated potential release area (PRA) detection tool in Python/ArcGIS which uses high spatial resolution digital elevation models (DEMs) and forest cover information derived from airborne remote sensing instruments as input. Such instruments can acquire spatially continuous data even over inaccessible terrain and cover large areas. We validate our tool using a database of historic avalanches acquired over 56 yr in the neighborhood of Davos, Switzerland, and apply this method for the avalanche tracks along the Rohtang tunnel access road. This tool, used by avalanche experts, delivers valuable input to identify focus areas for more-detailed investigations on avalanche release areas in remote regions such as the Indian Himalaya and is a precondition for large-scale avalanche hazard mapping.

  18. Femtosecond Laser--Pumped Source of Entangled Photons for Quantum Cryptography Applications

    International Nuclear Information System (INIS)

    Pan, D.; Donaldson, W.; Sobolewski, R.

    2007-01-01

    We present an experimental setup for generation of entangled-photon pairs via spontaneous parametric down-conversion, based on the femtosecond-pulsed laser. Our entangled-photon source utilizes a 76-MHz-repetition-rate, 100-fs-pulse-width, mode-locked, ultrafast femtosecond laser, which can produce, on average, more photon pairs than a cw laser of an equal pump power. The resulting entangled pairs are counted by a pair of high-quantum-efficiency, single-photon, silicon avalanche photodiodes. Our apparatus s intended as an efficient source/receiver system for the quantum communications and quantum cryptography applications

  19. Study of a pure CsI crystal readout by APD for Belle II end cap ECL upgrade

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Y., E-mail: jin@hep.phys.s.u-tokyo.ac.jp [Department of Physics, the University of Tokyo, 7-3-1 Hongo Bunkyo-ku, Tokyo 113-0033 (Japan); Aihara, H. [Department of Physics, the University of Tokyo, 7-3-1 Hongo Bunkyo-ku, Tokyo 113-0033 (Japan); Borshchev, O.V. [Enikolopov Institute of Synthetic Polymeric Materials of the Russian Academy of Sciences, Profsoyuznaya st. 70, Moscow 117393 (Russian Federation); Epifanov, D.A. [Department of Physics, the University of Tokyo, 7-3-1 Hongo Bunkyo-ku, Tokyo 113-0033 (Japan); Ponomarenko, S.A.; Surin, N.M. [Enikolopov Institute of Synthetic Polymeric Materials of the Russian Academy of Sciences, Profsoyuznaya st. 70, Moscow 117393 (Russian Federation)

    2016-07-11

    A scintillation counter consisting of a pure CsI crystal and avalanche photodiodes (Hamamatsu APD S8664-55 and S8664-1010) has been studied for the upgrade of the end cap electromagnetic calorimeter of Belle II detector. An essential increase of the light output was achieved with wavelength shifters based on nanostructured organosilicon luminophores. - Highlights: • A scintillation counter consisting of a pure CsI crystal and avalanche photodiodes has been studied. • The equivalent noise charge and equivalent noise energy of the counter have been measured. • An essential increase of the light output was achieved with wavelength shifters.

  20. On the high gain operation of low-pressure microdot gas avalanche chambers

    International Nuclear Information System (INIS)

    Breskin, A.

    1997-01-01

    Microdot avalanche chambers (MDOT) equipped with thin semitransparent Cr photocathodes, were characterized with UV photons at low gas pressure. Gains superior to 10 4 were reached with gas multiplication at the dots. In a mode where preamplification in the gas volume precedes the additional dot multiplication, gains superior to 10 6 were measured at 30-60 torr of propane. The fast amplification mechanism results in narrow high amplitude pulses with 2-3 ns rise time, visible with no further electronic amplification means. We present here our preliminary results and briefly discuss potential applications. (orig.)

  1. Avalanches near a solid insulator in nitrogen gas at atmospheric pressure

    International Nuclear Information System (INIS)

    Mahajan, S.M.; Sudarshan, T.S.; Department of Electrical and Computer Engineering, University of South Carolina, Columbia, South Carolina 29208)

    1989-01-01

    The pulsed Townsend (PT) technique was used to record the growth of avalanches near a solid insulator in nitrogen gas at 0.1 MPa. Several other nonconventional techniques for releasing initiatory electrons at the cathode are discussed. In this paper, experimental results of avalanches initiated by illuminating a fast (0.6-ns) nitrogen laser onto the cathode triple junction are presented. Data were recorded with plexiglas, Teflon, high-density polyethylene, low-density polyethylene, Delrin, etc. Effect of surface condition, variation of the distance between insulator surface and the avalanche initiation region, and the effect of a large number of previous avalanches on the avalanche characteristics at a particular voltage were studied. The Townsend primary ionization coefficient, hereafter referred to as growth coefficient (α), and drift velocity (V/sub e/) were evaluated through the PT technique. Results indicate that the avalanche growth in the vicinity of a solid insulator is less than that in an identical plain gas gap. Existence of a nonuniform field as a result of surface charges on the insulator and/or field modifications due to the avalanche space charge are believed to be responsible for this behavior

  2. Velocity distribution in snow avalanches

    Science.gov (United States)

    Nishimura, K.; Ito, Y.

    1997-12-01

    In order to investigate the detailed structure of snow avalanches, we have made snow flow experiments at the Miyanomori ski jump in Sapporo and systematic observations in the Shiai-dani, Kurobe Canyon. In the winter of 1995-1996, a new device to measure static pressures was used to estimate velocities in the snow cloud that develops above the flowing layer of avalanches. Measurements during a large avalanche in the Shiai-dani which damaged and destroyed some instruments indicate velocities increased rapidly to more than 50 m/s soon after the front. Velocities decreased gradually in the following 10 s. Velocities of the lower flowing layer were also calculated by differencing measurement of impact pressure. Both recordings in the snow cloud and in the flowing layer changed with a similar trend and suggest a close interaction between the two layers. In addition, the velocity showed a periodic change. Power spectrum analysis of the impact pressure and the static pressure depression showed a strong peak at a frequency between 4 and 6 Hz, which might imply the existence of either ordered structure or a series of surges in the flow.

  3. Evaluation of BPW-34 photodiode answer for 10 MeV electron dosimetry

    International Nuclear Information System (INIS)

    Khoury, H.J.; Melo, F.A.; Hazin, C.A.

    1992-01-01

    The viability of commercial photodiodes used for dosimetry of high energy electron beams was studied. The measures were made in a linear accelerators of 10 MeV, using the BPW-34 photodiode. The average energy of electrons on phantom surface and their average range were determined with the photodiode, and the results were compared with the obtained with a ionization chamber of parallel plate. (C.G.C.)

  4. Predictable quantum efficient detector based on n-type silicon photodiodes

    Science.gov (United States)

    Dönsberg, Timo; Manoocheri, Farshid; Sildoja, Meelis; Juntunen, Mikko; Savin, Hele; Tuovinen, Esa; Ronkainen, Hannu; Prunnila, Mika; Merimaa, Mikko; Tang, Chi Kwong; Gran, Jarle; Müller, Ingmar; Werner, Lutz; Rougié, Bernard; Pons, Alicia; Smîd, Marek; Gál, Péter; Lolli, Lapo; Brida, Giorgio; Rastello, Maria Luisa; Ikonen, Erkki

    2017-12-01

    The predictable quantum efficient detector (PQED) consists of two custom-made induced junction photodiodes that are mounted in a wedged trap configuration for the reduction of reflectance losses. Until now, all manufactured PQED photodiodes have been based on a structure where a SiO2 layer is thermally grown on top of p-type silicon substrate. In this paper, we present the design, manufacturing, modelling and characterization of a new type of PQED, where the photodiodes have an Al2O3 layer on top of n-type silicon substrate. Atomic layer deposition is used to deposit the layer to the desired thickness. Two sets of photodiodes with varying oxide thicknesses and substrate doping concentrations were fabricated. In order to predict recombination losses of charge carriers, a 3D model of the photodiode was built into Cogenda Genius semiconductor simulation software. It is important to note that a novel experimental method was developed to obtain values for the 3D model parameters. This makes the prediction of the PQED responsivity a completely autonomous process. Detectors were characterized for temperature dependence of dark current, spatial uniformity of responsivity, reflectance, linearity and absolute responsivity at the wavelengths of 488 nm and 532 nm. For both sets of photodiodes, the modelled and measured responsivities were generally in agreement within the measurement and modelling uncertainties of around 100 parts per million (ppm). There is, however, an indication that the modelled internal quantum deficiency may be underestimated by a similar amount. Moreover, the responsivities of the detectors were spatially uniform within 30 ppm peak-to-peak variation. The results obtained in this research indicate that the n-type induced junction photodiode is a very promising alternative to the existing p-type detectors, and thus give additional credibility to the concept of modelled quantum detector serving as a primary standard. Furthermore, the manufacturing of

  5. Does Avalanche Shovel Shape Affect Excavation Time: A Pilot Study

    Directory of Open Access Journals (Sweden)

    Kurt Schindelwig

    2017-05-01

    Full Text Available In Europe and North America, approximately 150 fatalities occur as a result of avalanches every year. However, it is unclear whether certain shovel shapes are more effective than others in snow removal during avalanche victim recovery. The objective was to determine the performance parameters with a developed standardized test using different shovel shapes and to determine sex-specific differences. Hence, several parameters were determined for clearing the snow from a snow filled box (15 men, 14 women. A flat (F and a deep (D shovel blade with the shaft connected straight (S or in clearing mode (C were used for the investigation of the shovel shapes FS, DC and the subsequent use of DC&DS. Mean snow mass shifted per unit time increased significantly from 1.50 kg/s with FS to 1.71 kg/s (14% with DS and further to 1.79 kg/s (4% with DC&DS for all participants. Snow mass shifted per unit time was 44% higher (p < 0.05 for men than for women. In excavation operations, the sex-specific physical performance should be taken into account. The results were limited to barely binding snow, because only with this snow did the tests show a high reliability.

  6. Anthropogenic effect on avalanche and debris flow activity

    Directory of Open Access Journals (Sweden)

    S. A. Sokratov

    2013-01-01

    Full Text Available The paper presents examples of the change in snow avalanches and debris flows activity due to the anthropogenic pressure on vegetation and relief. The changes in dynamical characteristics of selected snow avalanches and debris flows due to the anthropogenic activity are quantified. The conclusion is made that the anthropogenic effects on the snow avalanches and debris flows activity are more pronounced than the possible effects of the climate change. The necessity is expressed on the unavoidable changes of the natural environment as the result of a construction and of use of the constructed infrastructure to be account for in corresponding planning of the protection measures.

  7. Beyond Critical Exponents in Neuronal Avalanches

    Science.gov (United States)

    Friedman, Nir; Butler, Tom; Deville, Robert; Beggs, John; Dahmen, Karin

    2011-03-01

    Neurons form a complex network in the brain, where they interact with one another by firing electrical signals. Neurons firing can trigger other neurons to fire, potentially causing avalanches of activity in the network. In many cases these avalanches have been found to be scale independent, similar to critical phenomena in diverse systems such as magnets and earthquakes. We discuss models for neuronal activity that allow for the extraction of testable, statistical predictions. We compare these models to experimental results, and go beyond critical exponents.

  8. Construction techniques and working principles of external cathode Geiger-Mueller counters

    International Nuclear Information System (INIS)

    Sevegnani, Francisco Xavier

    1996-01-01

    In this paper, the construction technique and working principles of the external cathode Geiger-Mueller counter are described in detail. During the analysis of the behavior of these counters a new phenomena was observed, related to an increase int he background rate with the applied voltage. The experiments have also shown that the pulse amplitude of those counters decreases exponentially with the counting rate. The counters built with the techniques described in this paper has shown plateaus of about 1400 V with slope of 0,8%/100 V. (author)

  9. A novel approach to evaluate and compare computational snow avalanche simulation

    Directory of Open Access Journals (Sweden)

    J.-T. Fischer

    2013-06-01

    Full Text Available An innovative approach for the analysis and interpretation of snow avalanche simulation in three dimensional terrain is presented. Snow avalanche simulation software is used as a supporting tool in hazard mapping. When performing a high number of simulation runs the user is confronted with a considerable amount of simulation results. The objective of this work is to establish an objective, model independent framework to evaluate and compare results of different simulation approaches with respect to indicators of practical relevance, providing an answer to the important questions: how far and how destructive does an avalanche move down slope. For this purpose the Automated Indicator based Model Evaluation and Comparison (AIMEC method is introduced. It operates on a coordinate system which follows a given avalanche path. A multitude of simulation runs is performed with the snow avalanche simulation software SamosAT (Snow Avalanche MOdelling and Simulation – Advanced Technology. The variability of pressure-based run out and avalanche destructiveness along the path is investigated for multiple simulation runs, varying release volume and model parameters. With this, results of deterministic simulation software are processed and analysed by means of statistical methods. Uncertainties originating from varying input conditions, model parameters or the different model implementations are assessed. The results show that AIMEC contributes to the interpretation of avalanche simulations with a broad applicability in model evaluation, comparison as well as examination of scenario variations.

  10. Experimental method to predict avalanches based on neural networks

    Directory of Open Access Journals (Sweden)

    V. V. Zhdanov

    2016-01-01

    Full Text Available The article presents results of experimental use of currently available statistical methods to classify the avalanche‑dangerous precipitations and snowfalls in the Kishi Almaty river basin. The avalanche service of Kazakhstan uses graphical methods for prediction of avalanches developed by I.V. Kondrashov and E.I. Kolesnikov. The main objective of this work was to develop a modern model that could be used directly at the avalanche stations. Classification of winter precipitations into dangerous snowfalls and non‑dangerous ones was performed by two following ways: the linear discriminant function (canonical analysis and artificial neural networks. Observational data on weather and avalanches in the gorge Kishi Almaty in the gorge Kishi Almaty were used as a training sample. Coefficients for the canonical variables were calculated by the software «Statistica» (Russian version 6.0, and then the necessary formula had been constructed. The accuracy of the above classification was 96%. Simulator by the authors L.N. Yasnitsky and F.М. Cherepanov was used to learn the neural networks. The trained neural network demonstrated 98% accuracy of the classification. Prepared statistical models are recommended to be tested at the snow‑avalanche stations. Results of the tests will be used for estimation of the model quality and its readiness for the operational work. In future, we plan to apply these models for classification of the avalanche danger by the five‑point international scale.

  11. Spike avalanches exhibit universal dynamics across the sleep-wake cycle.

    Directory of Open Access Journals (Sweden)

    Tiago L Ribeiro

    2010-11-01

    Full Text Available Scale-invariant neuronal avalanches have been observed in cell cultures and slices as well as anesthetized and awake brains, suggesting that the brain operates near criticality, i.e. within a narrow margin between avalanche propagation and extinction. In theory, criticality provides many desirable features for the behaving brain, optimizing computational capabilities, information transmission, sensitivity to sensory stimuli and size of memory repertoires. However, a thorough characterization of neuronal avalanches in freely-behaving (FB animals is still missing, thus raising doubts about their relevance for brain function.To address this issue, we employed chronically implanted multielectrode arrays (MEA to record avalanches of action potentials (spikes from the cerebral cortex and hippocampus of 14 rats, as they spontaneously traversed the wake-sleep cycle, explored novel objects or were subjected to anesthesia (AN. We then modeled spike avalanches to evaluate the impact of sparse MEA sampling on their statistics. We found that the size distribution of spike avalanches are well fit by lognormal distributions in FB animals, and by truncated power laws in the AN group. FB data surrogation markedly decreases the tail of the distribution, i.e. spike shuffling destroys the largest avalanches. The FB data are also characterized by multiple key features compatible with criticality in the temporal domain, such as 1/f spectra and long-term correlations as measured by detrended fluctuation analysis. These signatures are very stable across waking, slow-wave sleep and rapid-eye-movement sleep, but collapse during anesthesia. Likewise, waiting time distributions obey a single scaling function during all natural behavioral states, but not during anesthesia. Results are equivalent for neuronal ensembles recorded from visual and tactile areas of the cerebral cortex, as well as the hippocampus.Altogether, the data provide a comprehensive link between behavior

  12. Performance Analysis of OCDMA Based on AND Detection in FTTH Access Network Using PIN & APD Photodiodes

    Science.gov (United States)

    Aldouri, Muthana; Aljunid, S. A.; Ahmad, R. Badlishah; Fadhil, Hilal A.

    2011-06-01

    In order to comprise between PIN photo detector and avalanche photodiodes in a system used double weight (DW) code to be a performance of the optical spectrum CDMA in FTTH network with point-to-multi-point (P2MP) application. The performance of PIN against APD is compared through simulation by using opt system software version 7. In this paper we used two networks designed as follows one used PIN photo detector and the second using APD photo diode, both two system using with and without erbium doped fiber amplifier (EDFA). It is found that APD photo diode in this system is better than PIN photo detector for all simulation results. The conversion used a Mach-Zehnder interferometer (MZI) wavelength converter. Also we are study, the proposing a detection scheme known as AND subtraction detection technique implemented with fiber Bragg Grating (FBG) act as encoder and decoder. This FBG is used to encode and decode the spectral amplitude coding namely double weight (DW) code in Optical Code Division Multiple Access (OCDMA). The performances are characterized through bit error rate (BER) and bit rate (BR) also the received power at various bit rate.

  13. Direct photon-counting scintillation detector readout using an SSPM

    International Nuclear Information System (INIS)

    Stapels, Christopher J.; Squillante, Michael R.; Lawrence, William G.; Augustine, Frank L.; Christian, James F.

    2007-01-01

    Gamma-ray detector technologies, capable of providing adequate energy information, use photomultiplier tubes (PMTs) or silicon avalanche photodiodes to detect the light pulse from a scintillation crystal. A new approach to detect the light from scintillation materials is to use an array of small photon counting detectors, or a 'detector-on-a-chip' based on a novel 'Solid-state Photomultiplier' (SSPM) concept. A CMOS SSPM coupled to a scintillation crystal uses an array of CMOS Geiger photodiode (GPD) pixels to collect light and produce a signal proportional to the energy of the radiation. Each pixel acts as a binary photon detector, but the summed output is an analog representation of the total photon intensity. We have successfully fabricated arrays of GPD pixels in a CMOS environment, which makes possible the production of miniaturized arrays integrated with the detector electronics in a small silicon chip. This detector technology allows for a substantial cost reduction while preserving the energy resolution needed for radiological measurements. In this work, we compare designs for the SSPM detector. One pixel design achieves maximum detection efficiency (DE) for 632-nm photons approaching 30% with a room temperature dark count rate (DCR) of less than 1 kHz for a 30-μm-diameter pixel. We characterize after pulsing and optical cross talk and discuss their effects on the performance of the SSPM. For 30-μm diameter, passively quenched CMOS GPD pixels, modeling suggests that a pixel spacing of approximately 90 μm optimizes the SSPM performance with respect to DE and cross talk

  14. On the use of single large-area photodiodes in scintillation counters

    International Nuclear Information System (INIS)

    Morrell, C.

    1989-12-01

    The compilation of this review was originally intended to assess the possibility of using photodiode-based scintillation counters in fluorescence EXAFS (or FLEXAFS) systems as a low-cost alternative to photomultiplier-based counters. The X-ray energies encountered in FLEXAFS experiments range from a few keV to a few tens of keV, and detectors are required to have some energy resolution and/or high count-rate capability in order to optimize the quality of data collected. The results presented in the reviewed literature imply strongly that photodiodes do not compete successfully with photomultipliers in scintillation counting systems for X-ray energies below the order of 100keV, at least at the present stage of photodiode technology. Nevertheless it is likely that there are other applications requiring X-ray detectors for which a photodiode-based scintillation counter may be perfectly adequate, and it is therefore felt that such a review is still useful. In addition, large-area single photodiodes have much to offer as X-ray detectors in their own right, and several of the considerations regarding their use in scintillation counters are highly relevant to this application. (author)

  15. Evaluation of gamma dose effect on PIN photodiode using analytical model

    Science.gov (United States)

    Jafari, H.; Feghhi, S. A. H.; Boorboor, S.

    2018-03-01

    The PIN silicon photodiodes are widely used in the applications which may be found in radiation environment such as space mission, medical imaging and non-destructive testing. Radiation-induced damage in these devices causes to degrade the photodiode parameters. In this work, we have used new approach to evaluate gamma dose effects on a commercial PIN photodiode (BPX65) based on an analytical model. In this approach, the NIEL parameter has been calculated for gamma rays from a 60Co source by GEANT4. The radiation damage mechanisms have been considered by solving numerically the Poisson and continuity equations with the appropriate boundary conditions, parameters and physical models. Defects caused by radiation in silicon have been formulated in terms of the damage coefficient for the minority carriers' lifetime. The gamma induced degradation parameters of the silicon PIN photodiode have been analyzed in detail and the results were compared with experimental measurements and as well as the results of ATLAS semiconductor simulator to verify and parameterize the analytical model calculations. The results showed reasonable agreement between them for BPX65 silicon photodiode irradiated by 60Co gamma source at total doses up to 5 kGy under different reverse voltages.

  16. Amplifiers dedicated for large area SiC photodiodes

    Science.gov (United States)

    Doroz, P.; Duk, M.; Korwin-Pawlowski, M. L.; Borecki, M.

    2016-09-01

    Large area SiC photodiodes find applications in optoelectronic sensors working at special conditions. These conditions include detection of UV radiation in harsh environment. Moreover, the mentioned sensors have to be selective and resistant to unwanted signals. For this purpose, the modulation of light at source unit and the rejection of constant current and low frequency component of signal at detector unit are used. The popular frequency used for modulation in such sensor is 1kHz. The large area photodiodes are characterized by a large capacitance and low shunt resistance that varies with polarization of the photodiode and can significantly modify the conditions of signal pre-amplification. In this paper two pre-amplifiers topology are analyzed: the transimpedance amplifier and the non-inverting voltage to voltage amplifier with negative feedback. The feedback loops of both pre-amplifiers are equipped with elements used for initial constant current and low frequency signals rejections. Both circuits are analyzed and compared using simulation and experimental approaches.

  17. Low-Noise Large-Area Photoreceivers with Low Capacitance Photodiodes

    Science.gov (United States)

    Joshi, Abhay M. (Inventor); Datta, Shubhashish (Inventor)

    2013-01-01

    A quad photoreceiver includes a low capacitance quad InGaAs p-i-n photodiode structure formed on an InP (100) substrate. The photodiode includes a substrate providing a buffer layer having a metal contact on its bottom portion serving as a common cathode for receiving a bias voltage, and successive layers deposited on its top portion, the first layer being drift layer, the second being an absorption layer, the third being a cap layer divided into four quarter pie shaped sections spaced apart, with metal contacts being deposited on outermost top portions of each section to provide output terminals, the top portions being active regions for detecting light. Four transimpedance amplifiers have input terminals electrically connected to individual output terminals of each p-i-n photodiode.

  18. Are dragon-king neuronal avalanches dungeons for self-organized brain activity?

    Science.gov (United States)

    de Arcangelis, L.

    2012-05-01

    Recent experiments have detected a novel form of spontaneous neuronal activity both in vitro and in vivo: neuronal avalanches. The statistical properties of this activity are typical of critical phenomena, with power laws characterizing the distributions of avalanche size and duration. A critical behaviour for the spontaneous brain activity has important consequences on stimulated activity and learning. Very interestingly, these statistical properties can be altered in significant ways in epilepsy and by pharmacological manipulations. In particular, there can be an increase in the number of large events anticipated by the power law, referred to herein as dragon-king avalanches. This behaviour, as verified by numerical models, can originate from a number of different mechanisms. For instance, it is observed experimentally that the emergence of a critical behaviour depends on the subtle balance between excitatory and inhibitory mechanisms acting in the system. Perturbing this balance, by increasing either synaptic excitation or the incidence of depolarized neuronal up-states causes frequent dragon-king avalanches. Conversely, an unbalanced GABAergic inhibition or long periods of low activity in the network give rise to sub-critical behaviour. Moreover, the existence of power laws, common to other stochastic processes, like earthquakes or solar flares, suggests that correlations are relevant in these phenomena. The dragon-king avalanches may then also be the expression of pathological correlations leading to frequent avalanches encompassing all neurons. We will review the statistics of neuronal avalanches in experimental systems. We then present numerical simulations of a neuronal network model introducing within the self-organized criticality framework ingredients from the physiology of real neurons, as the refractory period, synaptic plasticity and inhibitory synapses. The avalanche critical behaviour and the role of dragon-king avalanches will be discussed in

  19. Advances in gas avalanche photomultipliers

    CERN Document Server

    Breskin, Amos; Buzulutskov, A F; Chechik, R; Garty, E; Shefer, G; Singh, B K

    2000-01-01

    Gas avalanche detectors, combining solid photocathodes with fast electron multipliers, provide an attractive solution for photon localization over very large sensitive areas and under high illumination flux. They offer single-photon sensitivity and the possibility of operation under very intense magnetic fields. We discuss the principal factors governing the operation of gas avalanche photomultipliers. We summarize the recent progress made in alkali-halide and CVD-diamond UV-photocathodes, capable of operation under gas multiplication, and novel thin-film protected alkali-antimonide photocathodes, providing, for the first time, the possibility of operating gas photomultipliers in the visible range. Electron multipliers, adequate for these photon detectors, are proposed and some applications are briefly discussed.

  20. Catastrophic avalanches and methods of their control

    Directory of Open Access Journals (Sweden)

    N. A. Volodicheva

    2014-01-01

    Full Text Available Definition of such phenomenon as “catastrophic avalanche” is presented in this arti-cle. Several situations with releases of catastrophic avalanches in mountains of Caucasus, Alps, and Central Asia are investigated. Materials of snow-avalanche ob-servations performed since 1960s at the Elbrus station of the Lomonosov Moscow State University (Central Caucasus were used for this work. Complex-valued measures of engineering protection demonstrating different efficiencies are consid-ered.

  1. Design and characterization of single photon avalanche diodes arrays

    Science.gov (United States)

    Neri, L.; Tudisco, S.; Lanzanò, L.; Musumeci, F.; Privitera, S.; Scordino, A.; Condorelli, G.; Fallica, G.; Mazzillo, M.; Sanfilippo, D.; Valvo, G.

    2010-05-01

    During the last years, in collaboration with ST-Microelectronics, we developed a new avalanche photo sensor, single photon avalanche diode (SPAD) see Ref.[S. Privitera, et al., Sensors 8 (2008) 4636 [1];S. Tudisco et al., IEEE Sensors Journal 8 (2008) 1324 [2

  2. Single Photon Avalanche Diodes: Towards the Large Bidimensional Arrays

    Directory of Open Access Journals (Sweden)

    Emilio Sciacca

    2008-08-01

    Full Text Available Single photon detection is one of the most challenging goals of photonics. In recent years, the study of ultra-fast and/or low-intensity phenomena has received renewed attention from the academic and industrial communities. Intense research activity has been focused on bio-imaging applications, bio-luminescence, bio-scattering methods, and, more in general, on several applications requiring high speed operation and high timing resolution. In this paper we present design and characterization of bi-dimensional arrays of a next generation of single photon avalanche diodes (SPADs. Single photon sensitivity, dark noise, afterpulsing and timing resolution of the single SPAD have been examined in several experimental conditions. Moreover, the effects arising from their integration and the readout mode have also been deeply investigated.

  3. Scintillation light read-out by thin photodiodes in silicon wells

    CERN Document Server

    Allier, C P; Sarro, P M; Eijk, C W E

    2000-01-01

    Several applications of X-ray and gamma ray imaging detectors, e.g. in medical diagnostics, require millimeter or sub-millimeter spatial resolution and good energy resolution. In order to achieve such features we have proposed a new type of camera, which takes advantage of micromachining technology. It consists of an array of scintillator crystals encapsulated in silicon wells with photodiodes at the bottom. Several parameters of the photodiode need to be optimised: uniformity and efficiency of the light detection, gain, electronic noise and breakdown voltage. In order to evaluate these parameters we have processed 3x3 arrays of 1.8 mm sup 2 , approx 10 mu m thick photodiodes using (1 0 0) wafers etched in a KOH solution. Their optical response at 675 nm wavelength is comparable to that of a 500 mu m thick silicon PIN diode. Their low light detection efficiency is compensated by internal amplification. Several scintillator materials have been positioned in the wells on top of the thin photodiodes, i.e. a 200 ...

  4. Relation of the runaway avalanche threshold to momentum space topology

    Science.gov (United States)

    McDevitt, Christopher J.; Guo, Zehua; Tang, Xian-Zhu

    2018-02-01

    The underlying physics responsible for the formation of an avalanche instability due to the generation of secondary electrons is studied. A careful examination of the momentum space topology of the runaway electron population is carried out with an eye toward identifying how qualitative changes in the momentum space of the runaway electrons is correlated with the avalanche threshold. It is found that the avalanche threshold is tied to the merger of an O and X point in the momentum space of the primary runaway electron population. Such a change of the momentum space topology is shown to be accurately described by a simple analytic model, thus providing a powerful means of determining the avalanche threshold for a range of model assumptions.

  5. A novel Silicon Photomultiplier with bulk integrated quench resistors: utilization in optical detection and tracking applications for particle physics

    Energy Technology Data Exchange (ETDEWEB)

    Petrovics, Stefan, E-mail: stp@hll.mpg.de [Halbleiterlabor der Max-Planck Gesellschaft, Otto-Hahn-Ring 6, D-81739 Munich (Germany); Andricek, Ladislav [Halbleiterlabor der Max-Planck Gesellschaft, Otto-Hahn-Ring 6, D-81739 Munich (Germany); Diehl, Inge; Hansen, Karsten [DESY, Notkestrasse 85, D-22607 Hamburg (Germany); Jendrysik, Christian [Infineon Technologies AG, Am Campeon 1-12, D-85579 Neubiberg (Germany); Krueger, Katja [DESY, Notkestrasse 85, D-22607 Hamburg (Germany); Lehmann, Raik; Ninkovic, Jelena [Halbleiterlabor der Max-Planck Gesellschaft, Otto-Hahn-Ring 6, D-81739 Munich (Germany); Reckleben, Christian [DESY, Notkestrasse 85, D-22607 Hamburg (Germany); Richter, Rainer; Schaller, Gerhard; Schopper, Florian [Halbleiterlabor der Max-Planck Gesellschaft, Otto-Hahn-Ring 6, D-81739 Munich (Germany); Sefkow, Felix [DESY, Notkestrasse 85, D-22607 Hamburg (Germany)

    2017-02-11

    Silicon Photomultipliers (SiPMs) are a promising candidate for replacing conventional photomultiplier tubes (PMTs) in many applications, thanks to ongoing developments and advances in their technology. Conventional SiPMs are generally an array of avalanche photo diodes, operated in Geiger mode and read out in parallel, thus leading to the necessity of a high ohmic quenching resistor. This resistor enables passive quenching and is usually located on top of the array, limiting the fill factor of the device. In this paper, a novel detector concept with a bulk integrated quenching resistor will be recapped. In addition, due to other advantages of this novel detector design, a new concept, in which these devices will be utilized as tracking detectors for particle physics applications will be introduced, as well as first simulation studies and experimental measurements of this new approach. - Highlights: • A novel SiPM concept with bulk integrated quenching resistor is shown. • First prototypes of these SiPMs as tracking detectors are proposed. • Simulations of the Geiger efficiency suggest feasible operations at low overbias. • First measurements of the electron detection efficiency show promising results. • Measurements are in good agreement with the simulations.

  6. Magnetic avalanches in manganese-acetate, "magnetic deflagration"

    Science.gov (United States)

    Suzuki, Yoko

    Mn12-acetate, first synthesized in 1980 by Lis, is one example of a class of many molecules called single molecule magnets (SMMs) or molecular nanomagnets. These molecules have several atomic spins strongly coupled together within each molecule. They exhibit interesting quantum mechanical phenomena at low temperatures such as quantum tunneling of magnetization, which was first found with Mn12-acetate in 1996 by Friedman, et al. , and Berry phase oscillations which were measured in Fe8 (another SMM) in 1999 by Wernsdorfer, et al. In addition to possible application as memory storage and qubits for quantum computers, these systems provide the means for studies of mesoscopic physics as well as the interactions of the molecules with their environment, such as phonon, photon, nuclear spin, intermolecular dipole, and exchange interactions. Mn12-acetate has twelve Mn ions magnetically coupled in the center of the molecule yielding a giant spin of S = 10 at low temperature. It also has a large uniaxial anisotropy of 65 K. Below 3 K, magnetization curves show strong hysteresis due to the anisotropy barrier. At thesis temperatures, the spin relaxes through the barrier by quantum tunneling of magnetization, which produces regularly-spaced multiple resonant steps in the hysteresis curve. Magnetic avalanches, first detected by Paulsen et al., also occur for some samples only at low temperature, leading to a very fast single-step reversal of the full magnetization, which clearly differs from relaxation by tunneling. In this thesis, I present the results of detailed experimental studies of two aspects of magnetic avalanche phenomenon: "conditions for the triggering of avalanches" and "propagation of the avalanche front". In the first study, we find the magnetic fields at which avalanches occur are stochastically distributed in a particular range of fields. For the second study, we conducted local time-resolved measurements. The results indicate the magnetization avalanches spread

  7. The photodiode of UV-range on the basis of ZnSe

    Directory of Open Access Journals (Sweden)

    Perevertailo V. L.

    2010-03-01

    Full Text Available The construction and technology of Shottky photodiode on the basis of ZnSe, sensible in the ultraviolet region of spectrum are considered. Researches of electrophysical and photo-electric descriptions of photodiodes of Shottky Nі–ZnSe(Te,O–Іn are conducted and it is shown, that they can be applied in devices for radiometry and dissymmetry UV radiations in the ranges UVA, UVB and UVC. Comparison of parameters of developed UV photodiodes based on ZnSe with analogues showed that small capacitance and low value of dark current is their substantial difference of other ones.

  8. La Carte de Localisation Probable des Avalanches (CPLA

    Directory of Open Access Journals (Sweden)

    Gilles BORREL

    1994-12-01

    Full Text Available La Carte de Localisation Probable des Avalanches (CPLA indique l’enveloppe des limites extrêmes connues atteintes par les avalanches, ainsi que les travaux de protection associés. Il s’agit d’un document informatif et non d’une carte de risque. Depuis 1990, les données thématiques sont numérisées.

  9. Phase avalanches in near-adiabatic evolutions

    International Nuclear Information System (INIS)

    Vertesi, T.; Englman, R.

    2006-01-01

    In the course of slow, nearly adiabatic motion of a system, relative changes in the slowness can cause abrupt and high magnitude phase changes, ''phase avalanches,'' superimposed on the ordinary geometric phases. The generality of this effect is examined for arbitrary Hamiltonians and multicomponent (>2) wave packets and is found to be connected (through the Blaschke term in the theory of analytic signals) to amplitude zeros in the lower half of the complex time plane. Motion on a nonmaximal circle on the Poincare-sphere suppresses the effect. A spectroscopic transition experiment can independently verify the phase-avalanche magnitudes

  10. Physical and electrical bandwidths of integrated photodiodes in standard CMOS technology

    NARCIS (Netherlands)

    Radovanovic, S.; Annema, Anne J.; Nauta, Bram

    2003-01-01

    The influence of different geometries (layouts) and structures of high-speed photodiodes in fully standard 0.18 μm CMOS technology on their intrinsic (physical) and electrical bandwidths is analyzed. Three photodiode structures are studied: nwell/p-substrate, p+/nwell/p-substrate and p+/nwell. The

  11. IFKIS - a basis for managing avalanche risk in settlements and on roads in Switzerland

    Directory of Open Access Journals (Sweden)

    M. Bründl

    2004-01-01

    Full Text Available After the avalanche winter of 1999 in Switzerland, which caused 17 deaths and damage of over CHF 600 mill. in buildings and on roads, the project IFKIS, aimed at improving the basics of organizational measures (closure of roads, evacuation etc. in avalanche risk management, was initiated. The three main parts of the project were the development of a compulsory checklist for avalanche safety services, a modular education and training course program and an information system for safety services. The information system was developed in order to improve both the information flux between the national centre for avalanche forecasting, the Swiss Federal Institute for Snow and Avalanche Research SLF, and the local safety services on the one hand and the communication between avalanche safety services in the communities on the other hand. The results of this project make a valuable contribution to strengthening organizational measures in avalanche risk management and to closing the gaps, which became apparent during the avalanche winter of 1999. They are not restricted to snow avalanches but can also be adapted for dealing with other natural hazard processes and catastrophes.

  12. Bio-inspired nano-photodiode for Low Light, High Resolution and crosstalk-free CMOS image sensing

    KAUST Repository

    Saffih, Faycal; Fitzpatrick, Nathaniel N.; Mohammad, Mohammad Ali; Evoy, S.; Cui, Bo

    2011-01-01

    photodiode morphology. The proposed bio-inspired nanorod photodiode puts the depletion region length on the path of the incident photon instead of on its width, as the case is with the planar photodiodes. The depletion region has a revolving volume

  13. Cosmic rays with portable Geiger counters: from sea level to airplane cruise altitudes

    Energy Technology Data Exchange (ETDEWEB)

    Blanco, Francesco; La Rocca, Paola; Riggi, Francesco [Department of Physics and Astronomy, University of Catania, Via S. Sofia 64, I-95123 Catania (Italy)], E-mail: Francesco.Riggi@ct.infn.it

    2009-07-15

    Cosmic ray count rates with a set of portable Geiger counters were measured at different altitudes on the way to a mountain top and aboard an aircraft, between sea level and cruise altitude. Basic measurements may constitute an educational activity even with high school teams. For the understanding of the results obtained, simulations of extensive air showers induced by high-energy primary protons in the atmosphere were also carried out, involving undergraduate and graduate teaching levels.

  14. Radiation level measured by a portable Geiger-Mueller counter at the altitude of commercial air routes

    International Nuclear Information System (INIS)

    Araki, Takashi

    1995-01-01

    The background intensities of naturally occurring radiation were measured aboard scheduled commercial airplanes using a newly developed Geiger-Mueller counter with a pocket computer. The preliminary results show that the radiation at the cruising altitude of a commercial airplane on a transcontinental flight is 40 times higher than the ground-level. (author)

  15. Multiple-Event, Single-Photon Counting Imaging Sensor

    Science.gov (United States)

    Zheng, Xinyu; Cunningham, Thomas J.; Sun, Chao; Wang, Kang L.

    2011-01-01

    The single-photon counting imaging sensor is typically an array of silicon Geiger-mode avalanche photodiodes that are monolithically integrated with CMOS (complementary metal oxide semiconductor) readout, signal processing, and addressing circuits located in each pixel and the peripheral area of the chip. The major problem is its single-event method for photon count number registration. A single-event single-photon counting imaging array only allows registration of up to one photon count in each of its pixels during a frame time, i.e., the interval between two successive pixel reset operations. Since the frame time can t be too short, this will lead to very low dynamic range and make the sensor merely useful for very low flux environments. The second problem of the prior technique is a limited fill factor resulting from consumption of chip area by the monolithically integrated CMOS readout in pixels. The resulting low photon collection efficiency will substantially ruin any benefit gained from the very sensitive single-photon counting detection. The single-photon counting imaging sensor developed in this work has a novel multiple-event architecture, which allows each of its pixels to register as more than one million (or more) photon-counting events during a frame time. Because of a consequently boosted dynamic range, the imaging array of the invention is capable of performing single-photon counting under ultra-low light through high-flux environments. On the other hand, since the multiple-event architecture is implemented in a hybrid structure, back-illumination and close-to-unity fill factor can be realized, and maximized quantum efficiency can also be achieved in the detector array.

  16. Geiger-Mueller haloid counter dead time dependence on counting rate

    International Nuclear Information System (INIS)

    Onishchenko, A.M.; Tsvetkov, A.A.

    1980-01-01

    The experimental dependences of the dead time of Geiger counters (SBM-19, SBM-20, SBM-21 and SGM-19) on the loading, are presented. The method of two sources has been used to determine the dead time counters of increased stability. The counters are switched on according to the usually used circuit of discrete counting with loading resistance of 50 MOhm and the separating capacity of 10 pF. Voltage pulses are given to the counting device with the time of resolution of 100 ns, discrimenation threshold 3 V, input resistance 3.6 Ω and the input capacity-15 pF. The time constant of the counter RC-circuit is 50 μs

  17. Electron temperature structures associated with magnetic tearing modes in the Madison Symmetric Torus

    Science.gov (United States)

    Stephens, Hillary Dianne

    Tearing mode induced magnetic islands have a significant impact on the thermal characteristics of magnetically confined plasmas such as those in the reversed-field-pinch. Using a state-of-the-art Thomson scattering (TS) diagnostic, electron temperature fluctuations correlated with magnetic tearing modes have been observed on the Madison Symmetric Torus reversed-field-pinch. The TS diagnostic consists of two independently triggerable Nd:YAG lasers that can each pulse up to 15 times each plasma discharge and 21 General Atomics polchromators equipped with avalanche photodiode modules. Detailed calibrations focusing on accuracy, ease of use and repeatability and in-situ measurements have been performed on the system. Electron temperature (Te) profiles are acquired at 25 kHz with 2 cm or less resolution along the minor radius, sufficient to measure the effect of an island on the profile as the island rotates by the measurement point. Bayesian data analysis techniques are developed and used to detect fluctuations over an ensemble of shots. Four cases are studied; standard plasmas in quiescent periods, through sawteeth, through core reconnection events and in plasmas where the tearing mode activity is decreased. With a spectrum of unstable tearing modes, remnant islands that tend to flatten the temperature profile are present in the core between sawtooth-like reconnection events. This flattening is characteristic of rapid parallel heat conduction along helical magnetic field lines. The spatial structure of the temperature fluctuations show that the location of the rational surface of the m/n = 1/6 tearing mode is significantly further in than equilibrium suggestions predict. The fluctuations also provide a measurement of the remnant island width which is significantly smaller than the predicted full island width. These correlated fluctuations disappear during both global and core reconnection events. In striking contrast to temperature flattening, a temperature gradient

  18. Post-glacial rock avalanches in the Obersee Valley, Glarner Alps, Switzerland

    Science.gov (United States)

    Nagelisen, Jan; Moore, Jeffrey R.; Vockenhuber, Christoph; Ivy-Ochs, Susan

    2015-06-01

    The geological record of prehistoric rock avalanches provides invaluable data for assessing the hazard posed by these rare but destructive mass movements. Here we investigate two large rock avalanches in the Obersee valley of the Glarner Alps, Switzerland, providing detailed mapping of landslide and related Quaternary phenomena, revised volume estimates for each event, and surface exposure dating of rock avalanche deposits. The Rautispitz rock avalanche originated from the southern flank of the Obersee valley, releasing approximately 91 million m3 of limestone on steeply-dipping bedding planes. Debris had maximum horizontal travel distance of ~ 5000 m, a fahrboeschung angle (relating fall height to length) of 18°, and was responsible for the creation of Lake Obersee; deposits are more than 130 m thick in places. The Platten rock avalanche encompassed a source volume of 11 million m3 sliding from the northern flank of the Obersee valley on similar steeply-dipping limestone beds (bedrock forms a syncline under the valley). Debris had a maximum horizontal travel distance of 1600 m with a fahrboeschung angle of 21°, and is more than 80 m thick in places. Deposits of the Platten rock avalanche are superposed atop those from the Rautispitz event at the end of the Obersee valley where they dam Lake Haslensee. Runout for both events was simulated using the dynamic analysis code DAN3D; results showed excellent match to mapped deposit extents and thickness and helped confirm the hypothesized single-event failure scenarios. 36Cl cosmogenic nuclide surface exposure dating of 13 deposited boulders revealed a Younger Dryas age of 12.6 ± 1.0 ka for the Rautispitz rock avalanche and a mid-Holocene age of 6.1 ± 0.8 ka for the Platten rock avalanche. A seismological trigger is proposed for the former event due to potentially correlated turbidite deposits in nearby Lake Zurich.

  19. Pentacene-based photodiode with Schottky junction

    International Nuclear Information System (INIS)

    Lee, Jiyoul; Hwang, D.K.; Park, C.H.; Kim, S.S.; Im, Seongil

    2004-01-01

    We have fabricated a metal/organic semiconductor Schottky photodiode based on Al/pentacene junction. Since the energy band gap of thin solid pentacene was determined to be 1.82 eV, as characterized by direct absorption spectroscopy, we measured spectral photoresponses on our Schottky photodiode in the monochromatic light illumination range of 325-650 nm applying a reverse bias of -2 V. The main features of photo-response spectra were found to shift from those of direct absorption spectra toward higher photon energies. It is because the direct absorption spectra mainly show exciton level peaks rather than the true highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gaps while the photo-response spectra clearly represents the true HOMO-LUMO gap. Our photo-response spectra reveal 1.97 eV as the HOMO-LUMO gap

  20. Amplitude and timing properties of a Geiger discharge in a SiPM cell

    Energy Technology Data Exchange (ETDEWEB)

    Popova, E., E-mail: elenap73@mail.ru [National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), 115409, Kashirskoe Shosse 31 (Russian Federation); Buzhan, P.; Pleshko, A. [National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), 115409, Kashirskoe Shosse 31 (Russian Federation); Vinogradov, S. [University of Liverpool and Cockcroft Institute, Sci-Tech Daresbury, Keckwick Lane, Warrington WA4 4AD, Cheshire (United Kingdom); P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Leninskiy Prospect 53, Moscow 119991 (Russian Federation); Stifutkin, A.; Ilyin, A. [National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), 115409, Kashirskoe Shosse 31 (Russian Federation); Besson, D. [National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), 115409, Kashirskoe Shosse 31 (Russian Federation); Department of Physics and Astronomy, University of Kansas, Lawrence, KS 66045-2151 (United States); Mirzoyan, R. [Max-Planck-Institute for Physics, Föhringer Ring 6, 80805 München (Germany)

    2015-07-01

    The amplitude and timing properties of a Geiger discharge in a stand-alone SiPM cell have been investigated in detail. Use of a single stand-alone SiPM cell allows us to perform measurements with better accuracy than the multicell structure of conventional SiPMs. We have studied the dependence of the output charge and amplitude from an SiPM cell illuminated by focused light vs the number of primary photoelectrons. We propose a SPICE model which explains the amplitude over saturation (when the SiPM's amplitude is greater than the sum over all cells) characteristics of SiPM signals for more than one initial photoelectrons. The time resolutions of a SiPM cell have been measured for the case of single (SPTR) and multiphoton light pulses. The Full Width Half Max (FWHM) for SPTR has been found to be at the level of 30 ps for focused and 40 ps for unfocused light (100 μm cell size). - Highlights: • A stand-alone SiPM cell has been investigated in detail. • Amplitude and time properties have been measured with femtosecond 660 nm laser. • SPICE model for a Geiger discharge development has been proposed. • SPTR for a stand-alone 100 μm size SiPM cell has been found to be 40 ps FWHM.

  1. Construction and operating characteristics of flexible Geiger counters; Caracteristiques de construction et d'utilisation de compteurs Geiger flexibles; Konstruktsionnaya i operativnaya kharakteristiki gibkikh schetchikov Gejgera; Construccion y caracteristicas de funcionamiento de contadores Geiger flexibles

    Energy Technology Data Exchange (ETDEWEB)

    Richter, H G; Ballard, L F [Research Triangle Institute, Durham, NC (United States)

    1962-04-15

    point une methode de construction de compteurs Geiger flexibles ayant des dimensions tres variees. Les compteurs sont tres flexibles : un compteur de 3 cm de diametre peut etre plie avec un rayon de courbure de 5 cm. En utilisant du gaz Q (98,3% d'helium et 1,7% de n-butane) comme milieu de comptage, les paliers ont une longueur de plusieurs centaines de volts avec une pente de 3% et sont independants de la configuration geometrique du compteur. Les compteurs sont construits avec des tubes en chlorure de polyvinyle (PVC-744 - Alpha Wire Corp.). De courts segments du tube (longueur egale a environ 3 fois le diametre) sont glisses sur un mandrin d'aluminium grossierement filete et entoures d'un fil fortement serre. Le tout est place dans un four a 110{sup o}C pendant 20 minutes. Apres refroidissement, le segment de matiere plastique ainsi cannele est degage du mandrin. Ce traitement du tube empeche sa rupture lorsqu'il est enroule. Un disque de polystyrene, perfore de trous relativement grands a la peripherie pour l'ecoulement du gaz et d'un trou central de 0,6 mm pour le passage de l'anode, est attache a une extremite de chaque segment. En enfilant les segments ainsi prepares sur une anode en tungstene de 3 mm, en glissant une extremite de chaque segment sur le segment adjacent et en les fixant solidement avec un adhesif, on peut construire un compteur d'une longueur quelconque. On attache aux extremites des pieces en verre pour la fixation de l'anode et pour l'admission et l'evacuation du gaz. Un fil de cuivre nu, entoure en spirale dans les cannelures du compteur, donne une cathode externe satisfaisante, qui fonctionne suivant le mode observe par Maze. Un compteur de 3 cm de diametre et de 1 metre de longueur, lineaire ou enroule, possede un palier commencant a 1400 volts et allant jusqu'a 1700 volts avec une pente de 2,9%. On a enregistre des taux de comptage de plus de 300000 coups par minute, avec peu de pertes par coincidences. Comme le compteur est en fait une

  2. Forecasting of wet snow avalanche activity: Proof of concept and operational implementation

    Science.gov (United States)

    Gobiet, Andreas; Jöbstl, Lisa; Rieder, Hannes; Bellaire, Sascha; Mitterer, Christoph

    2017-04-01

    State-of-the-art tools for the operational assessment of avalanche danger include field observations, recordings from automatic weather stations, meteorological analyses and forecasts, and recently also indices derived from snowpack models. In particular, an index for identifying the onset of wet-snow avalanche cycles (LWCindex), has been demonstrated to be useful. However, its value for operational avalanche forecasting is currently limited, since detailed, physically based snowpack models are usually driven by meteorological data from automatic weather stations only and have therefore no prognostic ability. Since avalanche risk management heavily relies on timely information and early warnings, many avalanche services in Europe nowadays start issuing forecasts for the following days, instead of the traditional assessment of the current avalanche danger. In this context, the prognostic operation of detailed snowpack models has recently been objective of extensive research. In this study a new, observationally constrained setup for forecasting the onset of wet-snow avalanche cycles with the detailed snow cover model SNOWPACK is presented and evaluated. Based on data from weather stations and different numerical weather prediction models, we demonstrate that forecasts of the LWCindex as indicator for wet-snow avalanche cycles can be useful for operational warning services, but is so far not reliable enough to be used as single warning tool without considering other factors. Therefore, further development currently focuses on the improvement of the forecasts by applying ensemble techniques and suitable post processing approaches to the output of numerical weather prediction models. In parallel, the prognostic meteo-snow model chain is operationally used by two regional avalanche warning services in Austria since winter 2016/2017 for the first time. Experiences from the first operational season and first results from current model developments will be reported.

  3. Application of statistical and dynamics models for snow avalanche hazard assessment in mountain regions of Russia

    Science.gov (United States)

    Turchaninova, A.

    2012-04-01

    The estimation of extreme avalanche runout distances, flow velocities, impact pressures and volumes is an essential part of snow engineering in mountain regions of Russia. It implies the avalanche hazard assessment and mapping. Russian guidelines accept the application of different avalanche models as well as approaches for the estimation of model input parameters. Consequently different teams of engineers in Russia apply various dynamics and statistical models for engineering practice. However it gives more freedom to avalanche practitioners and experts but causes lots of uncertainties in case of serious limitations of avalanche models. We discuss these problems by presenting the application results of different well known and widely used statistical (developed in Russia) and avalanche dynamics models for several avalanche test sites in the Khibini Mountains (The Kola Peninsula) and the Caucasus. The most accurate and well-documented data from different powder and wet, big rare and small frequent snow avalanche events is collected from 1960th till today in the Khibini Mountains by the Avalanche Safety Center of "Apatit". This data was digitized and is available for use and analysis. Then the detailed digital avalanche database (GIS) was created for the first time. It contains contours of observed avalanches (ESRI shapes, more than 50 years of observations), DEMs, remote sensing data, description of snow pits, photos etc. Thus, the Russian avalanche data is a unique source of information for understanding of an avalanche flow rheology and the future development and calibration of the avalanche dynamics models. GIS database was used to analyze model input parameters and to calibrate and verify avalanche models. Regarding extreme dynamic parameters the outputs using different models can differ significantly. This is unacceptable for the engineering purposes in case of the absence of the well-defined guidelines in Russia. The frequency curves for the runout distance

  4. High voltage short plus generation based on avalanche circuit

    International Nuclear Information System (INIS)

    Hu Yuanfeng; Yu Xiaoqi

    2006-01-01

    Simulate the avalanche circuit in series with PSPICE module, design the high voltage short plus generation circuit by avalanche transistor in series for the sweep deflection circuit of streak camera. The output voltage ranges 1.2 KV into 50 ohm load. The rise time of the circuit is less than 3 ns. (authors)

  5. Electric field distribution and simulation of avalanche formation due ...

    Indian Academy of Sciences (India)

    Electric field distributions and their role in the formation of avalanche due to the passage of heavy ions in parallel grid avalanche type wire chamber detectors are evaluated using a Monte Carlo simulation. The relative merits and demerits of parallel and crossed wire grid configurations are studied. It is found that the crossed ...

  6. 2D dark-count-rate modeling of PureB single-photon avalanche diodes in a TCAD environment

    Science.gov (United States)

    Knežević, Tihomir; Nanver, Lis K.; Suligoj, Tomislav

    2018-02-01

    PureB silicon photodiodes have nm-shallow p+n junctions with which photons/electrons with penetration-depths of a few nanometer can be detected. PureB Single-Photon Avalanche Diodes (SPADs) were fabricated and analysed by 2D numerical modeling as an extension to TCAD software. The very shallow p+ -anode has high perimeter curvature that enhances the electric field. In SPADs, noise is quantified by the dark count rate (DCR) that is a measure for the number of false counts triggered by unwanted processes in the non-illuminated device. Just like for desired events, the probability a dark count increases with increasing electric field and the perimeter conditions are critical. In this work, the DCR was studied by two 2D methods of analysis: the "quasi-2D" (Q-2D) method where vertical 1D cross-sections were assumed for calculating the electron/hole avalanche-probabilities, and the "ionization-integral 2D" (II-2D) method where crosssections were placed where the maximum ionization-integrals were calculated. The Q-2D method gave satisfactory results in structures where the peripheral regions had a small contribution to the DCR, such as in devices with conventional deepjunction guard rings (GRs). Otherwise, the II-2D method proved to be much more precise. The results show that the DCR simulation methods are useful for optimizing the compromise between fill-factor and p-/n-doping profile design in SPAD devices. For the experimentally investigated PureB SPADs, excellent agreement of the measured and simulated DCR was achieved. This shows that although an implicit GR is attractively compact, the very shallow pn-junction gives a risk of having such a low breakdown voltage at the perimeter that the DCR of the device may be negatively impacted.

  7. Properties of the photodiode PiN as neutron detector

    International Nuclear Information System (INIS)

    Adamiec, G.; Iniguez, M.P.; Lorente, A.; Gallego, E.; Voytchev, M.

    2005-01-01

    The photodiode can be used to measure the ambient dose equivalent for an Am-Be source, as well placed in a paraffin sphere with LiF 6 converter as nude with a PE converter. The ratio between the counting rate and the ambient dose equivalent is linear in the two cases. The sensitivity of the diode with the converter 6 LiF is evaluated to 8.4 shocks by micro sievert by square centimeter of active surface of diode. The photodiode with the PE converter has a sensitivity lower of 2.1 shocks by micro sievert by square centimeter (for the Am-Be source) of active surface of diode. About the disadvantages, the disadvantage of photodiode inside the paraffin sphere is its size and weight; the disadvantage of the diode with the PE converter is its sensitivity to the orientation of the neutron flux and the necessity to calibrate for the source type. (N.C.)

  8. On the interplay between neoclassical tearing modes and nonlocal transport in toroidal plasmas

    Science.gov (United States)

    Ji, X. Q.; Xu, Y.; Hidalgo, C.; Diamond, P. H.; Liu, Yi; Pan, O.; Shi, Z. B.; Yu, D. L.

    2016-09-01

    This Letter presents the first observation on the interplay between nonlocal transport and neoclassical tearing modes (NTMs) during transient nonlocal heat transport events in the HL-2A tokamak. The nonlocality is triggered by edge cooling and large-scale, inward propagating avalanches. These lead to a locally enhanced pressure gradient at the q = 3/2 (or 2/1) rational surface and hence the onset of the NTM in relatively low β plasmas (βN < 1). The NTM, in return, regulates the nonlocal transport by truncation of avalanches by local sheared toroidal flows which develop near the magnetic island. These findings have direct implications for understanding the dynamic interaction between turbulence and large-scale mode structures in fusion plasmas.

  9. A new web-based system to improve the monitoring of snow avalanche hazard in France

    Science.gov (United States)

    Bourova, Ekaterina; Maldonado, Eric; Leroy, Jean-Baptiste; Alouani, Rachid; Eckert, Nicolas; Bonnefoy-Demongeot, Mylene; Deschatres, Michael

    2016-05-01

    Snow avalanche data in the French Alps and Pyrenees have been recorded for more than 100 years in several databases. The increasing amount of observed data required a more integrative and automated service. Here we report the comprehensive web-based Snow Avalanche Information System newly developed to this end for three important data sets: an avalanche chronicle (Enquête Permanente sur les Avalanches, EPA), an avalanche map (Carte de Localisation des Phénomènes d'Avalanche, CLPA) and a compilation of hazard and vulnerability data recorded on selected paths endangering human settlements (Sites Habités Sensibles aux Avalanches, SSA). These data sets are now integrated into a common database, enabling full interoperability between all different types of snow avalanche records: digitized geographic data, avalanche descriptive parameters, eyewitness reports, photographs, hazard and risk levels, etc. The new information system is implemented through modular components using Java-based web technologies with Spring and Hibernate frameworks. It automates the manual data entry and improves the process of information collection and sharing, enhancing user experience and data quality, and offering new outlooks to explore and exploit the huge amount of snow avalanche data available for fundamental research and more applied risk assessment.

  10. Evaluation and operationalization of a novel forest detrainment modeling approach for computational snow avalanche simulation

    Science.gov (United States)

    Teich, M.; Feistl, T.; Fischer, J.; Bartelt, P.; Bebi, P.; Christen, M.; Grêt-Regamey, A.

    2013-12-01

    Two-dimensional avalanche simulation software operating in three-dimensional terrain are widely used for hazard zoning and engineering to predict runout distances and impact pressures of snow avalanche events. Mountain forests are an effective biological protection measure; however, the protective capacity of forests to decelerate or even to stop avalanches that start within forested areas or directly above the treeline is seldom considered in this context. In particular, runout distances of small- to medium-scale avalanches are strongly influenced by the structural conditions of forests in the avalanche path. This varying decelerating effect has rarely been addressed or implemented in avalanche simulation. We present an evaluation and operationalization of a novel forest detrainment modeling approach implemented in the avalanche simulation software RAMMS. The new approach accounts for the effect of forests in the avalanche path by detraining mass, which leads to a deceleration and runout shortening of avalanches. The extracted avalanche mass caught behind trees stops immediately and, therefore, is instantly subtracted from the flow and the momentum of the stopped mass is removed from the total momentum of the avalanche flow. This relationship is parameterized by the empirical detrainment coefficient K [Pa] which accounts for the braking power of different forest types per unit area. To define K dependent on specific forest characteristics, we simulated 40 well-documented small- to medium-scale avalanches which released in and ran through forests with varying K-values. Comparing two-dimensional simulation results with one-dimensional field observations for a high number of avalanche events and simulations manually is however time consuming and rather subjective. In order to process simulation results in a comprehensive and standardized way, we used a recently developed automatic evaluation and comparison method defining runout distances based on a pressure

  11. A photodiode based on PbS nanocrystallites for FYTRONIX solar panel automatic tracking controller

    Science.gov (United States)

    Wageh, S.; Farooq, W. A.; Tataroğlu, A.; Dere, A.; Al-Sehemi, Abdullah G.; Al-Ghamdi, Ahmed A.; Yakuphanoglu, F.

    2017-12-01

    The structural, optical and photoelectrical properties of the fabricated Al/PbS/p-Si/Al photodiode based on PbS nanocrystallites were investigated. The PbS nanocrystallites were characterized by X-ray diffraction (XRD), UV-VIS-NIR, Infrared and Raman spectroscopy. The XRD diffraction peaks show that the prepared PbS nanostructure is in high crystalline state. Various electrical parameters of the prepared photodiode were analyzed from the electrical characteristics based on I-V and C-V-G. The photodiode has a high rectification ratio of 5.85×104 at dark and ±4 V. Moreover, The photocurrent results indicate a strong photovoltaic behavior. The frequency dependence of capacitance and conductance characteristics was attributed to depletion region behavior of the photodiode. The diode was used to control solar panel power automatic tracking controller in dual axis. The fabricated photodiode works as a photosensor to control Solar tracking systems.

  12. Rock avalanches clusters along the northern Chile coastal scarp

    Science.gov (United States)

    Crosta, G. B.; Hermanns, R. L.; Dehls, J.; Lari, S.; Sepulveda, S.

    2017-07-01

    Rock avalanche clusters can be relevant indicators of the evolution of specific regions. They can be used to define: the type and intensity of triggering events, their recurrence and potential probability of occurrence, the progressive damage of the rock mass, the mechanisms of transport and deposition, as well as the environmental conditions at the time of occurrence. This paper tackles these subjects by analyzing two main clusters of rock avalanches (each event between 0.6 and 30 Mm3), separated by few kilometers and located along the coastal scarp of Northern Chile, south of Iquique. It lies, hence, within a seismic area characterized by a long seismic gap that ended on April 1st, 2014 with a Mw 8.2 earthquake. The scar position, high along the coastal cliff, supports seismic triggering for these clusters. The deposits' relative positions are used to obtain the sequence of rock avalanching events for each cluster. The progressive decrease of volume in the sequence of rock avalanches forming each cluster fits well the theoretical models for successive slope failures. These sequences seem to agree with those derived by dating the deposits with ages spanning between 4 kyr and 60 kyr. An average uplift rate of 0.2 mm/yr in the last 40 kyr is estimated for the coastal plain giving a further constraint to the rock avalanche deposition considering the absence of reworking of the deposits. Volume estimates and datings allow the estimation of an erosion rate contribution of about 0.098-0.112 mm km- 2 yr- 1 which is well comparable to values presented in the literature for earthquake induced landslides. We have carried out numerical modeling in order to analyze the mobility of the rock avalanches and examine the environmental conditions that controlled the runout. In doing so, we have considered the sequence of individual rock avalanches within the specific clusters, thus including in the models the confining effect caused by the presence of previous deposits. Bingham

  13. Using stereo satellite imagery to account for ablation, entrainment, and compaction in volume calculations for rock avalanches on Glaciers: Application to the 2016 Lamplugh Rock Avalanche in Glacier Bay National Park, Alaska

    Science.gov (United States)

    Bessette-Kirton, Erin; Coe, Jeffrey A.; Zhou, Wendy

    2018-01-01

    The use of preevent and postevent digital elevation models (DEMs) to estimate the volume of rock avalanches on glaciers is complicated by ablation of ice before and after the rock avalanche, scour of material during rock avalanche emplacement, and postevent ablation and compaction of the rock avalanche deposit. We present a model to account for these processes in volume estimates of rock avalanches on glaciers. We applied our model by calculating the volume of the 28 June 2016 Lamplugh rock avalanche in Glacier Bay National Park, Alaska. We derived preevent and postevent 2‐m resolution DEMs from WorldView satellite stereo imagery. Using data from DEM differencing, we reconstructed the rock avalanche and adjacent surfaces at the time of occurrence by accounting for elevation changes due to ablation and scour of the ice surface, and postevent deposit changes. We accounted for uncertainties in our DEMs through precise coregistration and an assessment of relative elevation accuracy in bedrock control areas. The rock avalanche initially displaced 51.7 ± 1.5 Mm3 of intact rock and then scoured and entrained 13.2 ± 2.2 Mm3 of snow and ice during emplacement. We calculated the total deposit volume to be 69.9 ± 7.9 Mm3. Volume estimates that did not account for topographic changes due to ablation, scour, and compaction underestimated the deposit volume by 31.0–46.8 Mm3. Our model provides an improved framework for estimating uncertainties affecting rock avalanche volume measurements in glacial environments. These improvements can contribute to advances in the understanding of rock avalanche hazards and dynamics.

  14. Experimental studies on using silicon photodiode as read-out component of CsI(Tl) crystal

    International Nuclear Information System (INIS)

    He Jingtang; Chen Duanbao; Li Zuhao; Mao Yufang; Dong Xiaoli

    1996-01-01

    Experimental studies on using silicon photodiode as the read-out component of CsI(Tl) crystal are reported. The read-out properties of two different types of silicon photodiode produced by Hamamatsu were measured, including relations between energy resolution and bias, shaping time, sensitive area of photodiode and the dimension of the crystal

  15. Intermittent flow under constant forcing: Acoustic emission from creep avalanches

    Science.gov (United States)

    Salje, Ekhard K. H.; Liu, Hanlong; Jin, Linsen; Jiang, Deyi; Xiao, Yang; Jiang, Xiang

    2018-01-01

    While avalanches in field driven ferroic systems (e.g., Barkhausen noise), domain switching of martensitic nanostructures, and the collapse of porous materials are well documented, creep avalanches (avalanches under constant forcing) were never observed. Collapse avalanches generate particularly large acoustic emission (AE) signals and were hence chosen to investigate crackling noise under creep conditions. Piezoelectric SiO2 has a strong piezoelectric response even at the nanoscale so that we chose weakly bound SiO2 spheres in natural sandstone as a representative for the study of avalanches under time-independent, constant force. We found highly non-stationary crackling noise with four activity periods, each with power law distributed AE emission. Only the period before the final collapse shows the mean field behavior (ɛ near 1.39), in agreement with previous dynamic measurements at a constant stress rate. All earlier event periods show collapse with larger exponents (ɛ = 1.65). The waiting time exponents are classic with τ near 2.2 and 1.32. Creep data generate power law mixing with "effective" exponents for the full dataset with combinations of mean field and non-mean field regimes. We find close agreement with the predicted time-dependent fiber bound simulations, including events and waiting time distributions. Båth's law holds under creep conditions.

  16. Stellar Winds and Dust Avalanches in the AU Mic Debris Disk

    Energy Technology Data Exchange (ETDEWEB)

    Chiang, Eugene; Fung, Jeffrey, E-mail: echiang@astro.berkeley.edu, E-mail: jeffrey.fung@berkeley.edu [Department of Astronomy, University of California at Berkeley, Campbell Hall, Berkeley, CA 94720-3411 (United States)

    2017-10-10

    We explain the fast-moving, ripple-like features in the edge-on debris disk orbiting the young M dwarf AU Mic. The bright features are clouds of submicron dust repelled by the host star’s wind. The clouds are produced by avalanches: radial outflows of dust that gain exponentially more mass as they shatter background disk particles in collisional chain reactions. The avalanches are triggered from a region a few au across—the “avalanche zone”—located on AU Mic’s primary “birth” ring at a true distance of ∼35 au from the star but at a projected distance more than a factor of 10 smaller: the avalanche zone sits directly along the line of sight to the star, on the side of the ring nearest Earth, launching clouds that disk rotation sends wholly to the southeast, as observed. The avalanche zone marks where the primary ring intersects a secondary ring of debris left by the catastrophic disruption of a progenitor up to Varuna in size, less than tens of thousands of years ago. Only where the rings intersect are particle collisions sufficiently violent to spawn the submicron dust needed to seed the avalanches. We show that this picture works quantitatively, reproducing the masses, sizes, and velocities of the observed escaping clouds. The Lorentz force exerted by the wind’s magnetic field, whose polarity reverses periodically according to the stellar magnetic cycle, promises to explain the observed vertical undulations. The timescale between avalanches, about 10 yr, might be set by time variability of the wind mass loss rate or, more speculatively, by some self-regulating limit cycle.

  17. Time lapse photography as an approach to understanding glide avalanche activity

    Science.gov (United States)

    Hendrikx, Jordy; Peitzsch, Erich H.; Fagre, Daniel B.

    2012-01-01

    Avalanches resulting from glide cracks are notoriously difficult to forecast, but are a recurring problem for numerous avalanche forecasting programs. In some cases glide cracks are observed to open and then melt away in situ. In other cases, they open and then fail catastrophically as large, full-depth avalanches. Our understanding and management of these phenomena are currently limited. It is thought that an increase in the rate of snow gliding occurs prior to full-depth avalanche activity so frequent observation of glide crack movement can provide an index of instability. During spring 2011 in Glacier National Park, Montana, USA, we began an approach to track glide crack avalanche activity using a time-lapse camera focused on a southwest facing glide crack. This crack melted in-situ without failing as a glide avalanche, while other nearby glide cracks on north through southeast aspects failed. In spring 2012, a camera was aimed at a large and productive glide crack adjacent to the Going to the Sun Road. We captured three unique glide events in the field of view. Unfortunately, all of them either failed very quickly, or during periods of obscured view, so measurements of glide rate could not be obtained. However, we compared the hourly meteorological variables during the period of glide activity to the same variables prior to glide activity. The variables air temperature, relative humidity, air pressure, incoming and reflected long wave radiation, SWE, total precipitation, and snow depth were found to be statistically different for our cases examined. We propose that these are some of the potential precursors for glide avalanche activity, but do urge caution in their use, due to the simple approach and small data set size. It is hoped that by introducing a workable method to easily record glide crack movement, combined with ongoing analysis of the associated meteorological data, we will improve our understanding of when, or if, glide avalanche activity will ensue.

  18. Avalanches and plastic flow in crystal plasticity: an overview

    Science.gov (United States)

    Papanikolaou, Stefanos; Cui, Yinan; Ghoniem, Nasr

    2018-01-01

    Crystal plasticity is mediated through dislocations, which form knotted configurations in a complex energy landscape. Once they disentangle and move, they may also be impeded by permanent obstacles with finite energy barriers or frustrating long-range interactions. The outcome of such complexity is the emergence of dislocation avalanches as the basic mechanism of plastic flow in solids at the nanoscale. While the deformation behavior of bulk materials appears smooth, a predictive model should clearly be based upon the character of these dislocation avalanches and their associated strain bursts. We provide here a comprehensive overview of experimental observations, theoretical models and computational approaches that have been developed to unravel the multiple aspects of dislocation avalanche physics and the phenomena leading to strain bursts in crystal plasticity.

  19. Theoretical issues in tokamak confinement: (i) Internal/edge transport barriers and (ii) runaway avalanche confinement

    International Nuclear Information System (INIS)

    Connor, J.W.; Helander, P.; Thyagaraja, A.; Andersson, F.; Fueloep, T.; Eriksson, L.-G.; Romanelli, M.

    2001-01-01

    This paper summarises a number of distinct, but related, pieces of work on key confinement issues for tokamaks, in particular the formation of internal and edge transport barriers, both within turbulent and neoclassical models, and radial diffusion of avalanching runaway electrons. First-principle simulations of tokamak turbulence and transport using the two-fluid, electromagnetic, global code CUTIE are described. The code has demonstrated the spontaneous formation of internal transport barriers near mode rational surfaces, in qualitative agreement with observations on JET and RTP. The theory of neoclassical transport in an impure, toroidal plasma has been extended to allow for steeper pressure and temperature gradients than are usually considered, and is then found to become nonlinear under conditions typical of the tokamak edge. For instance, the particle flux is found to be a nonmonotonic function of the gradients, thus allowing for a bifurcation in the ion particle flux. Finally, it is shown that radial diffusion caused by magnetic fluctuations can effectively suppress avalanches of runaway electrons if the fluctuation amplitude exceeds δB/B∼10 -3 . (author)

  20. La carte de localisation des phénomènes d'avalanche (CLPA : enjeux et perspectives The Localization Map of Avalanche Phenomena (CLPA in French: stakes and prospects

    Directory of Open Access Journals (Sweden)

    Mylène Bonnefoy, Gilles Borrel, Didier Richard, Laurent Bélanger et Mohamed Naaim

    2010-09-01

    Full Text Available Après presque quarante ans d’existence, la carte de localisation des phénomènes d'avalanche (CLPA constitue aujourd’hui un outil incontournable pour la prise en compte du risque d’avalanche dans l’aménagement et la gestion des territoires de montagne. Pour optimiser la sécurité des zones urbanisées, ce dispositif a su se rénover par une mise à jour régulière et étendue des données et l'étude de nouvelles zones, mais aussi par une meilleure diffusion auprès des opérationnels et du public concernés. Les auteurs nous rappellent ici l'évolution du fonctionnement de la CLPA et l'intérêt d'élargir la valorisation de ses données dans de nouveaux outils scientifiques.The Localization Map of Avalanche Phenomena (CLPA in French was created in 1971 as a response to the deadly avalanche occurred in Val d’Isère (February 1970, 39 persons killed. The aim is to inventory and to memorize areas where avalanches occurred in the past in order to keep in memory precisely greatest limits of those avalanches. The CLPA was rapidly considered as an essential element for developing plan in mountain areas. After the other catastrophic avalanche, which occurred in the Montroc Village (Chamonix in February 1999, it was recommended “the mutual valuation of the EPA and the CLPA integrated into an information system containing the information on avalanches and the information on the other natural risks in mountain”. The ministry in charge of environment decided therefore to continue and to modernize the CLPA, mission that was assigned to the Cemagref with the ONF collaboration. This modernization was based on the end of maps and testimonies records digitizing, on the compilation of summary notes concerning main avalanches information in reference to a mountain massif, on the institution of a durable updating of the map and on the possibility of having all information on line on the website www.avalanches.fr. Information recorded in the

  1. Reliability studies on Si PIN photodiodes under Co-60 gamma radiation

    Energy Technology Data Exchange (ETDEWEB)

    Prabhakara Rao, Y. P. [Integrated Circuits Division, Bharat Electronics Limited, Bangalore, Karnataka-560013 (India) and Department of Studies in Physics, University of Mysore, Manasagangotri, Mysore, Karnataka-570006 (India); Praveen, K. C.; Gnana Prakash, A. P. [Department of Studies in Physics, University of Mysore, Manasagangotri, Mysore, Karnataka-570006 (India); Rani, Y. Rejeena [Integrated Circuits Division, Bharat Electronics Limited, Bangalore, Karnataka-560013 (India)

    2013-02-05

    Silicon PIN photodiodes were fabricated with 250 nm SiO{sub 2} antireflective coating (ARC). The changes in the electrical characteristics, capacitance-voltage characteristics and spectral response after gamma irradiation are systematically studied to estimate the radiation tolerance up to 10 Mrad. The different characteristics studied in this investigation demonstrate that Si PIN photodiodes are suitable for high radiation environment.

  2. THEORY AND PRACTICE OF INDIVIDUAL SNOW AVALANCHE RISK ASSESSMENT IN THE RUSSIAN ARCTIC

    Directory of Open Access Journals (Sweden)

    Aleksandr Shnyparkov

    2012-01-01

    Full Text Available In recent years, the Government of the Russian Federation considerably increased attention to the exploitation of the Russian Arctic territories. Simultaneously, the evaluation of snow avalanches danger was enhanced with the aim to decrease fatalities and reduce economic losses. However, it turned out that solely reporting the degree of avalanche danger is not sufficient. Instead, quantitative information on probabilistic parameters of natural hazards, the characteristics of their effects on the environment and possibly resulting losses is increasingly needed. Such information allows for the estimation of risk, including risk related to snow avalanches. Here, snow avalanche risk is quantified for the Khibiny Mountains, one of the most industrialized parts of the Russian Arctic: Major parts of the territory have an acceptable degree of individual snow avalanche risk (<1×10-6. The territories with an admissible (10-4–10-6 or unacceptable (>1×10-4 degree of individual snow avalanche risk (0.5 and 2% of the total area correspond to the Southeast of the Khibiny Mountains where settlements and mining industries are situated. Moreover, due to an increase in winter tourism, some traffic infrastructure is located in valleys with an admissible or unacceptable degree of individual snow avalanches risk.

  3. Miniature probe with semiconductor photodiode for measuring dose rates in radiotherapy

    International Nuclear Information System (INIS)

    Burian, A.

    1991-01-01

    The probe is designed for gaining information on the magnitude and spatial distribution of the dose which will be absorbed by the patient's body during radiotherapy. The probe satisfies requirements of high-level miniaturization and requirements on the shape and tissue-equivalence of the casing, as well as on efficient electromagnetic shielding. It is fitted with a miniature photodiode. Conductive carbon cement was used for attaching contacts to the photodiode. Efficient electromagnetic shielding was achieved by means of a carbon-based conductive layer. The photodiode casing was made from a mixture of organic materials whose biogenic elements approximate the standard soft human tissue. The geometry of the casing is adapted to the particular field of application of the probe. (Z.S). 2 figs

  4. High pressure pulsed avalanche discharges: Scaling of required preionization rate for homogeneity

    International Nuclear Information System (INIS)

    Brenning, N.; Axnaes, I.; Nilsson, J.O.; Eninger, J.E.

    1994-01-01

    Homogeneous high-pressure discharges can be formed by pulsed avalanche breakdown, provided that the individual avalanche heads have diffused to a large enough radius to overlap before streamer breakdown occurs. The overlap condition can be met by using an external mechanism to preionize the neutral gas, e.g., x-rays or uv radiation. There are several scenarios, (1) to preionize the gas, and then trigger the discharge by the sudden application of an electric field, (2) to apply an overvoltage over the discharge and trigger the discharge by external ionization, or (3) to have a continuous rate of external ionization and let the E field rise, with a comparatively long time constant τ, across the breakdown value (E/n) 0 . The authors here study the last of these scenarios, which gives a very efficient use of the preionization source because the avalanche startpoint can accumulate during the pre-avalanche phase. The authors have found that the required avalanche startpoint density N st.p , defined as the density of individual single, or clusters of, electrons at the time when the electric field crosses the breakdown value, scales with pressure and rise time as N st.p ∝ p 21/4 τ -3/4 . This pressure scaling disagrees with the p 3/2 scaling found by Levatter and Lin (J. Appl. Phys. 51(1), 210), while the rise time scaling agrees satisfactorily with their results. For an E field which rises slowly across the breakdown value, the pre-avalanche accumulation of electrons must be taken into account, as well as the fact that the density n e of free electrons becomes larger than the density N st.p of independent avalanche heads: when electron impact ionization closely balances attachment, individual electrons are replaced by clusters of electrons which are too close to form individual avalanche heads

  5. Three hydrogenated amorphous silicon photodiodes stacked for an above integrated circuit colour sensor

    Energy Technology Data Exchange (ETDEWEB)

    Gidon, Pierre; Giffard, Benoit; Moussy, Norbert; Parrein, Pascale; Poupinet, Ludovic [CEA-LETI, MINATEC, CEA-Grenoble, 17 rue des Martyrs, 38054 Grenoble Cedex 9 (France)

    2010-03-15

    We present theoretical simulation and experimental results of a new colour pixel structure. This pixel catches the light in three stacked amorphous silicon photodiodes encompassed between transparent electrodes. The optical structure has been simulated for signal optimisation. The thickness of each stacked layer is chosen in order to absorb the maximum of light and the three signals allow to linearly calculate the CIE colour coordinates 1 with minimum error and noise. The whole process is compatible with an above integrated circuit (IC) approach. Each photodiode is an n-i-p structure. For optical reason, the upper diode must be controlled down to 25 nm thickness. The first test pixel structure allows a good recovering of colour coordinates. The measured absorption spectrum of each photodiode is in good agreement with our simulations. This specific stack with three photodiodes per pixel totalises two times more signal than an above IC pixel under a standard Bayer pattern 2,3. In each square of this GretagMacbeth chart is the reference colour on the right and the experimentally measured colour on the left with three amorphous silicon photodiodes per pixel. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  6. Optical and electrical characterization of AlGaN based Schottky photodiodes after annealing at different temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Ngoepe, PNM, E-mail: phuti.ngoepe@up.ac.za; Meyer, WE; Diale, M; Auret, FD; Schalkwyk, L van

    2014-04-15

    In this study a comparison is made between the optical and electrical properties of Ni/Au and Ni/Ir/Au Schottky photodiodes based on Al{sub 0.35}Ga{sub 0.65}N. The effects of inserting Ir between Ni and Au are of particular interest. The comparison in the properties is done after annealing the photodiodes at different temperatures in an argon gas ambient. The reverse current decreased with annealing temperature up to 400 °C for the Ni/Au Schottky photodiode and up to 500 °C for the Ni/Ir/Au photodiode. The Schottky barrier heights increased with increasing annealing temperature. The responsivity of the Ni/Au photodiode was higher than that of the Ni/Ir/Au photodiode. The transmission of the Ni/Au metal layer improved with increasing annealing temperature up to 500 °C and the best transmission of the Ni/Ir/Au metal layer was after 400 °C annealing.

  7. Change of energy dependence for X-rays of photodiode detector

    International Nuclear Information System (INIS)

    Silva, M.F. da; Freitas, L.C. de

    1992-01-01

    The energy dependence of photodiode Siemens SFH-206 for X-rays beams of 24 kV to 50 kV was studied and compared with the ionization chamber of parallel plates. The photodiode presented 450% of maxim change response for the energy band studied. A study was made, using aluminium, acrylic, mylar aluminized and mylar graphitized filters and showed that the two last reduce this maxim change response to 101% and 108%, respectively. (C.G.C.)

  8. Regional snow-avalanche detection using object-based image analysis of near-infrared aerial imagery

    Directory of Open Access Journals (Sweden)

    K. Korzeniowska

    2017-10-01

    Full Text Available Snow avalanches are destructive mass movements in mountain regions that continue to claim lives and cause infrastructural damage and traffic detours. Given that avalanches often occur in remote and poorly accessible steep terrain, their detection and mapping is extensive and time consuming. Nonetheless, systematic avalanche detection over large areas could help to generate more complete and up-to-date inventories (cadastres necessary for validating avalanche forecasting and hazard mapping. In this study, we focused on automatically detecting avalanches and classifying them into release zones, tracks, and run-out zones based on 0.25 m near-infrared (NIR ADS80-SH92 aerial imagery using an object-based image analysis (OBIA approach. Our algorithm takes into account the brightness, the normalised difference vegetation index (NDVI, the normalised difference water index (NDWI, and its standard deviation (SDNDWI to distinguish avalanches from other land-surface elements. Using normalised parameters allows applying this method across large areas. We trained the method by analysing the properties of snow avalanches at three 4 km−2 areas near Davos, Switzerland. We compared the results with manually mapped avalanche polygons and obtained a user's accuracy of > 0.9 and a Cohen's kappa of 0.79–0.85. Testing the method for a larger area of 226.3 km−2, we estimated producer's and user's accuracies of 0.61 and 0.78, respectively, with a Cohen's kappa of 0.67. Detected avalanches that overlapped with reference data by > 80 % occurred randomly throughout the testing area, showing that our method avoids overfitting. Our method has potential for large-scale avalanche mapping, although further investigations into other regions are desirable to verify the robustness of our selected thresholds and the transferability of the method.

  9. Performance Analysis of Si-Based Ultra-Shallow Junction Photodiodes for UV Radiation Detection

    NARCIS (Netherlands)

    Shi, L.

    2013-01-01

    This thesis presents a performance investigation of newly-developed ultra-shallow junction photodiodes (PureB-diodes) for ultraviolet (UV) radiation detection. The photodiodes are fabricated by pure boron chemical vapor deposition (PureB CVD) technology, which can provide nanometer-thin boron

  10. Hydrological Climate Classification: Can We Improve on Köppen-Geiger?

    Science.gov (United States)

    Knoben, W.; Woods, R. A.; Freer, J. E.

    2017-12-01

    Classification is essential in the study of complex natural systems, yet hydrology so far has no formal way to structure the climate forcing which underlies hydrologic response. Various climate classification systems can be borrowed from other disciplines but these are based on different organizing principles than a hydrological classification might use. From gridded global data we calculate a gridded aridity index, an aridity seasonality index and a rain-vs-snow index, which we use to cluster global locations into climate groups. We then define the membership degree of nearly 1100 catchments to each of our climate groups based on each catchment's climate and investigate the extent to which streamflow responses within each climate group are similar. We compare this climate classification approach with the often-used Köppen-Geiger classification, using statistical tests based on streamflow signature values. We find that three climate indices are sufficient to distinguish 18 different climate types world-wide. Climates tend to change gradually in space and catchments can thus belong to multiple climate groups, albeit with different degrees of membership. Streamflow responses within a climate group tend to be similar, regardless of the catchments' geographical proximity. A Wilcoxon two-sample test based on streamflow signature values for each climate group shows that the new classification can distinguish different flow regimes using this classification scheme. The Köppen-Geiger approach uses 29 climate classes but is less able to differentiate streamflow regimes. Climate forcing exerts a strong control on typical hydrologic response and both change gradually in space. This makes arbitrary hard boundaries in any classification scheme difficult to defend. Any hydrological classification should thus acknowledge these gradual changes in forcing. Catchment characteristics (soil or vegetation type, land use, etc) can vary more quickly in space than climate does, which

  11. Novel vertical silicon photodiodes based on salicided polysilicon trenched contacts

    International Nuclear Information System (INIS)

    Kaminski, Yelena; Shauly, Eitan; Paz, Yaron

    2015-01-01

    The classical concept of silicon photodiodes comprises of a planar design characterized by heavily doped emitters. Such geometry has low collection efficiency of the photons absorbed close to the surface. An alternative, promising, approach is to use a vertical design. Nevertheless, realization of such design is technologically challenged, hence hardly explored. Herein, a novel type of silicon photodiodes, based on salicided polysilicon trenched contacts, is presented. These contacts can be prepared up to 10 μm in depth, without showing any leakage current associated with the increase in the contact area. Consequently, the trenched photodiodes revealed better performance than no-trench photodiodes. A simple two dimensional model was developed, allowing to estimate the conditions under which a vertical design has the potential to have better performance than that of a planar design. At large, the deeper the trench is, the better is the vertical design relative to the planar (up to 10 μm for silicon). The vertical design is more advantageous for materials characterized by short diffusion lengths of the carriers. Salicided polysilicon trenched contacts open new opportunities for the design of solar cells and image sensors. For example, these contacts may passivate high contact area buried contacts, by virtue of the conformity of polysilicon interlayer, thus lowering the via resistance induced recombination enhancement effect

  12. Novel vertical silicon photodiodes based on salicided polysilicon trenched contacts

    Energy Technology Data Exchange (ETDEWEB)

    Kaminski, Yelena [Department of Chemical Engineering, Technion, Haifa (Israel); TowerJazz Ltd. Migdal Haemek (Israel); Shauly, Eitan [TowerJazz Ltd. Migdal Haemek (Israel); Paz, Yaron, E-mail: paz@tx.technion.ac.il [Department of Chemical Engineering, Technion, Haifa (Israel)

    2015-12-07

    The classical concept of silicon photodiodes comprises of a planar design characterized by heavily doped emitters. Such geometry has low collection efficiency of the photons absorbed close to the surface. An alternative, promising, approach is to use a vertical design. Nevertheless, realization of such design is technologically challenged, hence hardly explored. Herein, a novel type of silicon photodiodes, based on salicided polysilicon trenched contacts, is presented. These contacts can be prepared up to 10 μm in depth, without showing any leakage current associated with the increase in the contact area. Consequently, the trenched photodiodes revealed better performance than no-trench photodiodes. A simple two dimensional model was developed, allowing to estimate the conditions under which a vertical design has the potential to have better performance than that of a planar design. At large, the deeper the trench is, the better is the vertical design relative to the planar (up to 10 μm for silicon). The vertical design is more advantageous for materials characterized by short diffusion lengths of the carriers. Salicided polysilicon trenched contacts open new opportunities for the design of solar cells and image sensors. For example, these contacts may passivate high contact area buried contacts, by virtue of the conformity of polysilicon interlayer, thus lowering the via resistance induced recombination enhancement effect.

  13. Emplacement of rock avalanche material across saturated sediments, Southern Alp, New Zealand

    Science.gov (United States)

    Dufresne, A.; Davies, T. R.; McSaveney, M. J.

    2012-04-01

    The spreading of material from slope failure events is not only influenced by the volume and nature of the source material and the local topography, but also by the materials encountered in the runout path. In this study, evidence of complex interactions between rock avalanche and sedimentary runout path material were investigated at the 45 x 106 m3 long-runout (L: 4.8 km) Round Top rock avalanche deposit, New Zealand. It was sourced within myolinitic schists of the active strike-slip Alpine Fault. The narrow and in-failure-direction elongate source scarp is deep-seated, indicating slope failure was triggered by strong seismic activity. The most striking morphological deposit features are longitudinal ridges aligned radially to source. Trenching and geophysical surveys show bulldozed and sheared substrate material at ridge termini and laterally displaced sedimentary strata. The substrate failed at a minimum depth of 3 m indicating a ploughing motion of the ridges into the saturated material below. Internal avalanche compression features suggest deceleration behind the bulldozed substrate obstacle. Contorted fabric in material ahead of the ridge document substrate disruption by the overriding avalanche material deposited as the next down-motion hummock. Comparison with rock avalanches of similar volume but different emplacement environments places Round Top between longer runout avalanches emplaced over e.g. playa lake sediments and those with shorter travel distances, whose runout was apparently retarded by topographic obstacles or that entrained high-friction debris. These empirical observations indicate the importance of runout path materials on tentative trends in rock avalanche emplacement dynamics and runout behaviour.

  14. Bio-inspired nano-photodiode for Low Light, High Resolution and crosstalk-free CMOS image sensing

    KAUST Repository

    Saffih, Faycal

    2011-05-01

    Previous attempts have been devoted to mimic biological vision intelligence at the architectural system level. In this paper, a novel imitation of biological visual system intelligence is suggested, at the device level with the introduction of novel photodiode morphology. The proposed bio-inspired nanorod photodiode puts the depletion region length on the path of the incident photon instead of on its width, as the case is with the planar photodiodes. The depletion region has a revolving volume to increase the photodiode responsivity, and thus its photosensitivity. In addition, it can virtually boost the pixel fill factor (FF) above the 100% classical limit due to decoupling of its vertical sensing area from its limited planar circuitry area. Furthermore, the suggested nanorod photodiode photosensitivity is analytically proven to be higher than that of the planar photodiode. We also show semi-empirically that the responsivity of the suggested device varies linearly with its height; this important feature has been confirmed using Sentaurus simulation. The proposed nano-photorod is believed to meet the increasingly stringent High-Resolution-Low-Light (HRLL) detection requirements of the camera-phone and biomedical imaging markets. © 2011 IEEE.

  15. High quantum efficiency annular backside silicon photodiodes for reflectance pulse oximetry in wearable wireless body sensors

    International Nuclear Information System (INIS)

    Duun, Sune; Haahr, Rasmus G; Hansen, Ole; Birkelund, Karen; Thomsen, Erik V

    2010-01-01

    The development of annular photodiodes for use in a reflectance pulse oximetry sensor is presented. Wearable and wireless body sensor systems for long-term monitoring require sensors that minimize power consumption. We have fabricated large area 2D ring-shaped silicon photodiodes optimized for minimizing the optical power needed in reflectance pulse oximetry. To simplify packaging, backside photodiodes are made which are compatible with assembly using surface mounting technology without pre-packaging. Quantum efficiencies up to 95% and area-specific noise equivalent powers down to 30 fW Hz -1/2 cm -1 are achieved. The photodiodes are incorporated into a wireless pulse oximetry sensor system embedded in an adhesive patch presented elsewhere as 'The Electronic Patch'. The annular photodiodes are fabricated using two masked diffusions of first boron and subsequently phosphor. The surface is passivated with a layer of silicon nitride also serving as an optical filter. As the final process, after metallization, a hole in the center of the photodiode is etched using deep reactive ion etch.

  16. Theory of suppressing avalanche process of carrier in short pulse laser irradiated dielectrics

    Energy Technology Data Exchange (ETDEWEB)

    Deng, H. X., E-mail: hxdeng@uestc.edu.cn, E-mail: xtzu@uestc.edu.cn, E-mail: kaisun@umich.edu; Zu, X. T., E-mail: hxdeng@uestc.edu.cn, E-mail: xtzu@uestc.edu.cn, E-mail: kaisun@umich.edu; Xiang, X. [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China); Zheng, W. G.; Yuan, X. D. [Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900 (China); Sun, K., E-mail: hxdeng@uestc.edu.cn, E-mail: xtzu@uestc.edu.cn, E-mail: kaisun@umich.edu [Department of Materials Engineering and Sciences, University of Michigan, 413B Space Research Building, Ann Arbor, Michigan 48109-2143 (United States); Gao, F. [Pacific Northwest National Laboratory, P. O. Box 999, Richland, Washington 99352 (United States)

    2014-05-28

    A theory for controlling avalanche process of carrier during short pulse laser irradiation is proposed. We show that avalanche process of conduction band electrons (CBEs) is determined by the occupation number of phonons in dielectrics. The theory provides a way to suppress avalanche process and a direct judgment for the contribution of avalanche process and photon ionization process to the generation of CBEs. The obtained temperature dependent rate equation shows that the laser induced damage threshold of dielectrics, e.g., fused silica, increase nonlinearly with the decreases of temperature. Present theory predicts a new approach to improve the laser induced damage threshold of dielectrics.

  17. The December 2008 Crammont rock avalanche, Mont Blanc massif area, Italy

    Directory of Open Access Journals (Sweden)

    P. Deline

    2011-12-01

    Full Text Available We describe a 0.5 Mm3 rock avalanche that occurred in 2008 in the western Alps and discuss possible roles of controlling factors in the context of current climate change. The source is located between 2410 m and 2653 m a.s.l. on Mont Crammont and is controlled by a densely fractured rock structure. The main part of the collapsed rock mass deposited at the foot of the rock wall. A smaller part travelled much farther, reaching horizontal and vertical travel distances of 3050 m and 1560 m, respectively. The mobility of the rock mass was enhanced by channelization and snow. The rock-avalanche volume was calculated by comparison of pre- and post-event DTMs, and geomechanical characterization of the detachment zone was extracted from LiDAR point cloud processing. Back analysis of the rock-avalanche runout suggests a two stage event.

    There was no previous rock avalanche activity from the Mont Crammont ridge during the Holocene. The 2008 rock avalanche may have resulted from permafrost degradation in the steep rock wall, as suggested by seepage water in the scar after the collapse in spite of negative air temperatures, and modelling of rock temperatures that indicate warm permafrost (T > −2 °C.

  18. A Ring-shaped photodiode designed for use in a reflectance pulse oximetry sensor in wireless health monitoring applications

    DEFF Research Database (Denmark)

    Duun, Sune; Haahr, Rasmus Grønbek; Birkelund, Karen

    2010-01-01

    We report a photodiode for use in a reflectance pulse oximeter for use in autonomous and low-power homecare applications. The novelty of the reflectance pulse oximeter is a large ring shaped backside silicon pn photodiode. The ring-shaped photodiode gives optimal gathering of light and thereby...... enable very low light-emitting diode (LED) driving currents for the pulse oximeter. The photodiode also have a two layer SiO2/SiN interference filter yielding 98% transmission at the measuring wavelengths, 660 nm and 940 nm, and suppressing other wavelengths down to 50% transmission. The photodiode has...

  19. Performance test of Si PIN photodiode line scanner for thermal neutron detection

    Energy Technology Data Exchange (ETDEWEB)

    Totsuka, Daisuke, E-mail: totsuka@imr.tohoku.ac.jp [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); Nihon Kessho Kogaku Co., Ltd., 810-5 Nobe-cho Tatebayashi, Gunma 374-0047 (Japan); Yanagida, Takayuki [New Industry Creation Hatchery Center (NICHe) 6-6-10 Aoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-8579 (Japan); Fukuda, Kentaro; Kawaguchi, Noriaki [Tokuyama Corp., 3 Shibuya Shibuya-ku, Tokyo 150-8383 (Japan); Fujimoto, Yutaka [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); Pejchal, Jan [Institute of Physics AS CR, Cukrovarnicka 10, Prague 6, 162-53 (Czech Republic); Yokota, Yuui [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); Yoshikawa, Akira [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); New Industry Creation Hatchery Center (NICHe) 6-6-10 Aoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-8579 (Japan)

    2011-12-11

    Thermal neutron imaging using Si PIN photodiode line scanner and Eu-doped LiCaAlF{sub 6} crystal scintillator has been developed. The pixel dimensions of photodiode are 1.18 mm (width) Multiplication-Sign 3.8 mm (length) with 0.4 mm gap and the module has 192 channels in linear array. The emission peaks of Eu-doped LiCaAlF{sub 6} after thermal neutron excitation are placed at 370 and 590 nm, and the corresponding photon sensitivities of photodiode are 0.04 and 0.34 A/W, respectively. Polished scintillator blocks with a size of 1.18 mm (width) Multiplication-Sign 3.8 mm (length) Multiplication-Sign 5.0 mm (thickness) were wrapped by several layers of Teflon tapes as a reflector and optically coupled to the photodiodes by silicone grease. JRR-3 MUSASI beam line emitting 13.5 meV thermal neutrons with the flux of 8 Multiplication-Sign 10{sup 5} n/cm{sup 2} s was used for the imaging test. As a subject for imaging, a Cd plate was moved at the speed of 50 mm/s perpendicular to the thermal neutron beam. Analog integration time was set to be 416.6 {mu}s, then signals were converted by a delta-sigma A/D converter. After the image processing, we successfully obtained moving Cd plate image under thermal neutron irradiation using PIN photodiode line scanner coupled with Eu-doped LiCaAlF{sub 6} scintillator.

  20. Performance test of Si PIN photodiode line scanner for thermal neutron detection

    International Nuclear Information System (INIS)

    Totsuka, Daisuke; Yanagida, Takayuki; Fukuda, Kentaro; Kawaguchi, Noriaki; Fujimoto, Yutaka; Pejchal, Jan; Yokota, Yuui; Yoshikawa, Akira

    2011-01-01

    Thermal neutron imaging using Si PIN photodiode line scanner and Eu-doped LiCaAlF 6 crystal scintillator has been developed. The pixel dimensions of photodiode are 1.18 mm (width)×3.8 mm (length) with 0.4 mm gap and the module has 192 channels in linear array. The emission peaks of Eu-doped LiCaAlF 6 after thermal neutron excitation are placed at 370 and 590 nm, and the corresponding photon sensitivities of photodiode are 0.04 and 0.34 A/W, respectively. Polished scintillator blocks with a size of 1.18 mm (width)×3.8 mm (length)×5.0 mm (thickness) were wrapped by several layers of Teflon tapes as a reflector and optically coupled to the photodiodes by silicone grease. JRR-3 MUSASI beam line emitting 13.5 meV thermal neutrons with the flux of 8×10 5 n/cm 2 s was used for the imaging test. As a subject for imaging, a Cd plate was moved at the speed of 50 mm/s perpendicular to the thermal neutron beam. Analog integration time was set to be 416.6 μs, then signals were converted by a delta-sigma A/D converter. After the image processing, we successfully obtained moving Cd plate image under thermal neutron irradiation using PIN photodiode line scanner coupled with Eu-doped LiCaAlF 6 scintillator.

  1. Avalanches in functional materials and geophysics

    CERN Document Server

    Saxena, Avadh; Planes, Antoni

    2017-01-01

    This book provides the state-of-the art of the present understanding of avalanche phenomena in both functional materials and geophysics. The main emphasis of the book is analyzing these apparently different problems within the common perspective of out-of-equilibrium phenomena displaying spatial and temporal complexity that occur in a broad range of scales. Many systems, when subjected to an external force, respond intermittently in the form of avalanches that often span over a wide range of sizes, energies and durations. This is often related to a class of critical behavior characterized by the absence of characteristic scales. Typical examples are magnetization processes, plastic deformation and failure occuring in functional materials. These phenomena share many similarities with seismicity arising from the earth crust failure due to stresses that originate from plate tectonics.

  2. Rockslide-debris avalanche of May 18, 1980, Mount St. Helens Volcano, Washington

    Science.gov (United States)

    Glicken, Harry

    1996-01-01

    This report provides a detailed picture of the rockslide-debris avalanche of the May 18, 1980, eruption of Mount St. Helens volcano. It provides a characterization of the deposit, a reinterpretation of the details of the first minutes of the eruption of May 18, and insight into the transport mechanism of the mass movement. Details of the rockslide event, as revealed by eyewitness photographs, are correlated with features of the deposit. The photographs show three slide blocks in the rockslide movement. Slide block I was triggered by a magnitude 5.1 earthquake at 8:32 a.m. Pacific Daylight Time (P.D.T.). An exploding cryptodome burst through slide block II to produce the 'blast surge.' Slide block III consisted of many discrete failures that were carried out in continuing pyroclastic currents generated from the exploding cryptodome. The cryptodome continued to depressurize after slide block III, producing a blast deposit that rests on top of the debris-avalanche deposit. The hummocky 2.5 cubic kilometer debris-avalanche deposit consists of block facies (pieces of the pre-eruption Mount St. Helens transported relatively intact) and matrix facies (a mixture of rocks from the old mountain and cryptodome dacite). Block facies is divided into five lithologic units. Matrix facies was derived from the explosively generated current of slide block III as well as from disaggregation and mixing of debris-avalanche blocks. The mean density of the old cone was measured to be abut 20 percent greater than the mean density of the avalanche deposit. Density in the deposit does not decrease with distance which suggests that debris-avalanche blocks were dilated at the mountain, rather than during transport. Various grain-size parameters that show that clast size converges about a mean with distance suggest mixing during transport. The debris-avalanche flow can be considered a grain flow, where particles -- either debris-avalanche blocks or the clasts within the blocks -- collided and

  3. Laser damage helps the eavesdropper in quantum cryptography.

    Science.gov (United States)

    Bugge, Audun Nystad; Sauge, Sebastien; Ghazali, Aina Mardhiyah M; Skaar, Johannes; Lydersen, Lars; Makarov, Vadim

    2014-02-21

    We propose a class of attacks on quantum key distribution (QKD) systems where an eavesdropper actively engineers new loopholes by using damaging laser illumination to permanently change properties of system components. This can turn a perfect QKD system into a completely insecure system. A proof-of-principle experiment performed on an avalanche photodiode-based detector shows that laser damage can be used to create loopholes. After ∼1  W illumination, the detectors' dark count rate reduces 2-5 times, permanently improving single-photon counting performance. After ∼1.5  W, the detectors switch permanently into the linear photodetection mode and become completely insecure for QKD applications.

  4. ALS-based hummock size-distance relationship assessment of Mt Shasta debris avalanche deposit, Northern California, USA

    Science.gov (United States)

    Tortini, Riccardo; Carn, Simon; van Wyk de Vries, Benjamin

    2015-04-01

    deformation along a north south tending fault and a comparison with the NED-derived DTM. This work aims to improve our understanding of the Shasta DAD morphology and dynamics, and provide insight into the cause and timing of events as well as the mode of emplacement of the DAD. The Cascade range includes numerous large extinct, dormant or active stratovolcanoes. Size-distance relationships will enable us to estimate the volume of the collapsed mass and the travel distance of the avalanche, and the knowledge of the link between basement structures and the Shasta DAD will elucidate the causes of edifice instability and may be used to target priority areas for volcanic hazard mapping.

  5. Statistical analysis and trends of wet snow avalanches in the French Alps over the period 1959-2010

    Science.gov (United States)

    Naaim, Mohamed

    2017-04-01

    Since an avalanche contains a significant proportion of wet snow, its characteristics and its behavior change significantly (heterogeneous and polydisperse). Even if on a steep given slope, wet snow avalanches are slow. They can flow over gentle slopes and reach the same extensions as dry avalanches. To highlight the link between climate warming and the proliferation of wet snow avlanches, we crossed two well-documented avalanche databases: the permanent avalanche chronicle (EPA) and the meteorological re-analyzes. For each avalanche referenced in EPA, a moisture index I is buit. It represents the ratio of the thickness of the wet snow layer to the total snow thickness, at the date of the avalanche on the concerned massif at 2400 m.a.s.l. The daily and annual proportion of avalanches exceeding a given threshold of I are calculated for each massif of the French alps. The statistical distribution of wet avalanches per massif is calculated over the period 1959-2009. The statistical quantities are also calculated over two successive periods of the same duration 1959-1984 and 1984-2009, and the annual evolution of the proportion of wet avalanches is studied using time-series tools to detect potential rupture or trends. This study showed that about 77% of avalanches on the French alpine massif mobilize dry snow. The probability of having an avalanche of a moisture index greater than 10 % in a given year is 0.2. This value varies from one massif to another. The analysis between the two successive periods showed a significant growth of wet avalanches on 20 massifs and a decrease on 3 massifs. The study of time-series confirmed these trends, which are of the inter-annual variability level.

  6. Geiger Muller (GM) detector as online monitor: an experimental study

    International Nuclear Information System (INIS)

    Jayan, M.P.; Pawar, V.J.; Krishnakumar, P.; Sureshkumar, M.

    2014-01-01

    Monitoring the inadvertent release of radioactivity into otherwise inactive liquid streams is a common requirement in nuclear industry. In addition to conventional off-line sampling and measurement methods, nuclear facilities usually uses online methods to get real-time detection of activity contents in process cooling water lines and steam condensate lines. Due to its simplicity, ruggedness and cost effectiveness, Geiger Muller counter is obviously the first choice for online application. Though GM based monitors for such online application were in industrial use for a long time, practical data on the response of the detector with respect low level activities in the effluents is scarce in literature. This work was carried out to fill this information gap. The data generated in these experiments may be useful in giving a realistic interpretation of the response of the existing monitors and setting up their alarm limits

  7. Potassium analysis by beta counting using a Geiger-Mueller system

    International Nuclear Information System (INIS)

    Espana, E.; Beneitez, P.; Calderon, T.

    1993-01-01

    A technique for quantitative analysis of different soils, ceramics, feldspars and natural halide samples is presented, based on the measurement of β-activities using a Geiger-Mueller system. The system was calibrated with KCl, KC 8 H 5 O 4 , KNO 3 and K 2 SO 4 standards and a potassium content of 1% yields a net β-count rate (background subtracted) of about 55 cph. Precision values of less than ±0.4% K can be achieved in counting times of about 4 hours. The results agree with those obtained by means of other more common analytical methods such as flame photometry, atomic absorption and γ-spectrometry. In comparison with these methods, this approach is direct, precise and non-destructive, because the samples do not require prior treatment. (author) 16 refs.; 2 figs.; 6 tabs

  8. Lumped transmission line avalanche pulser

    Science.gov (United States)

    Booth, Rex

    1995-01-01

    A lumped linear avalanche transistor pulse generator utilizes stacked transistors in parallel within a stage and couples a plurality of said stages, in series with increasing zener diode limited voltages per stage and decreasing balanced capacitance load per stage to yield a high voltage, high and constant current, very short pulse.

  9. An AC modulated near infrared gain calibration system for a "Violin-Mode" transimpedance amplifier, intended for advanced LIGO suspensions

    Science.gov (United States)

    Lockerbie, N. A.; Tokmakov, K. V.

    2016-07-01

    The background to this work was a prototype shadow sensor, which was designed for retro-fitting to an advanced LIGO (Laser Interferometer Gravitational wave Observatory) test-mass/mirror suspension, in which a 40 kg test-mass/mirror is suspended by four approximately 600 mm long by 0.4 mm diameter fused-silica suspension fibres. The shadow sensor comprised a LED source of Near InfraRed (NIR) radiation, and a "tall-thin" rectangular silicon photodiode detector, which together were to bracket the fibre under test. The photodiode was positioned so as to be sensitive (primarily) to transverse "Violin-Mode" vibrations of such a fibre, via the oscillatory movement of the shadow cast by the fibre, as this moved across the face of the detector. In this prototype shadow sensing system the photodiode was interfaced to a purpose-built transimpedance amplifier, this having both AC and DC outputs. A quasi-static calibration was made of the sensor's DC responsivity, i.e., incremental rate of change of output voltage versus fibre position, by slowly scanning a fused-silica fibre sample transversely through the illuminating beam. The work reported here concerns the determination of the sensor's more important AC (Violin-Mode) responsivity. Recognition of the correspondence between direct AC modulation of the source, and actual Violin-Mode signals, and of the transformative role of the AC/DC gain ratio for the amplifier, at any modulation frequency, f, resulted in the construction of the AC/DC calibration source described here. A method for determining in practice the transimpedance AC/DC gain ratio of the photodiode and amplifier, using this source, is illustrated by a specific numerical example, and the gain ratio for the prototype sensing system is reported over the frequency range 1 Hz-300 kHz. In fact, a maximum DC responsivity of 1.26 kV.m-1 was measured using the prototype photodiode sensor and amplifier discussed here. Therefore, the measured AC/DC transimpedance gain ratio

  10. An AC modulated near infrared gain calibration system for a "Violin-Mode" transimpedance amplifier, intended for advanced LIGO suspensions.

    Science.gov (United States)

    Lockerbie, N A; Tokmakov, K V

    2016-07-01

    The background to this work was a prototype shadow sensor, which was designed for retro-fitting to an advanced LIGO (Laser Interferometer Gravitational wave Observatory) test-mass/mirror suspension, in which a 40 kg test-mass/mirror is suspended by four approximately 600 mm long by 0.4 mm diameter fused-silica suspension fibres. The shadow sensor comprised a LED source of Near InfraRed (NIR) radiation, and a "tall-thin" rectangular silicon photodiode detector, which together were to bracket the fibre under test. The photodiode was positioned so as to be sensitive (primarily) to transverse "Violin-Mode" vibrations of such a fibre, via the oscillatory movement of the shadow cast by the fibre, as this moved across the face of the detector. In this prototype shadow sensing system the photodiode was interfaced to a purpose-built transimpedance amplifier, this having both AC and DC outputs. A quasi-static calibration was made of the sensor's DC responsivity, i.e., incremental rate of change of output voltage versus fibre position, by slowly scanning a fused-silica fibre sample transversely through the illuminating beam. The work reported here concerns the determination of the sensor's more important AC (Violin-Mode) responsivity. Recognition of the correspondence between direct AC modulation of the source, and actual Violin-Mode signals, and of the transformative role of the AC/DC gain ratio for the amplifier, at any modulation frequency, f, resulted in the construction of the AC/DC calibration source described here. A method for determining in practice the transimpedance AC/DC gain ratio of the photodiode and amplifier, using this source, is illustrated by a specific numerical example, and the gain ratio for the prototype sensing system is reported over the frequency range 1 Hz-300 kHz. In fact, a maximum DC responsivity of 1.26 kV.m(-1) was measured using the prototype photodiode sensor and amplifier discussed here. Therefore, the measured AC/DC transimpedance gain

  11. Information processing occurs via critical avalanches in a model of the primary visual cortex

    International Nuclear Information System (INIS)

    Bortolotto, G. S.; Girardi-Schappo, M.; Gonsalves, J. J.; Tragtenberg, M. H. R.; Pinto, L. T.

    2016-01-01

    We study a new biologically motivated model for the Macaque monkey primary visual cortex which presents power-law avalanches after a visual stimulus. The signal propagates through all the layers of the model via avalanches that depend on network structure and synaptic parameter. We identify four different avalanche profiles as a function of the excitatory postsynaptic potential. The avalanches follow a size-duration scaling relation and present critical exponents that match experiments. The structure of the network gives rise to a regime of two characteristic spatial scales, one of which vanishes in the thermodynamic limit. (paper)

  12. Avalanches in the Bean critical-state model

    International Nuclear Information System (INIS)

    Barford, W.

    1997-01-01

    A macroscopic equation of motion for the flux density in dirty type-II superconductors is introduced. The flux density is subject to various types of spatially varying pinning force. When there is no stick-slip dynamics, i.e., when the static pinning force equals the dynamic pinning force, it is shown that in both one and two dimensions an increase in the surface magnetic field leads to an overall height change and hence to a change in magnetization equal to the change in the surface magnetic field. More interesting behavior occurs on introducing stick-slip dynamics, i.e., when the static pinning force exceeds the dynamic pinning force. In this limit a distribution of avalanche sizes over four orders of magnitude is found for a 100x100 lattice. Apart from the anomalous behavior at large sizes, this is shown to fit a distribution of the form P(s)∼s -ν exp(-s/α), where s is the avalanche size. The anomalous behavior for large sizes corresponds to avalanches which involve most of the lattice and, hence, cause the flux to open-quotes slide over the edge,close quotes as detected by a change in the edge magnetization. copyright 1997 The American Physical Society

  13. Das Thema “Altern” in Arno Geigers Roman «Alles über Sally»

    Directory of Open Access Journals (Sweden)

    Meike Dackweiler

    2013-11-01

    Full Text Available Alles über Sally (All about Sally is the fifth novel of the successful Austrian author Arno Geiger. While it was both praised and criticized for being a contemporary adaption of the adultery novel, little importance was attached to the theme of ageing, which pervades the whole novel. Moreover, adulterous female characters over fifty are rare in contemporary German literature. Given these premises, this essay examines the composition of the ageing characters in the novel and provides a discussion of the social construction of images of ageing.

  14. Hybrid amplifier for calorimetry with photodiode readout

    Energy Technology Data Exchange (ETDEWEB)

    Sushkov, V V

    1994-12-31

    A hybrid surface mounted amplifier for the photodiode readout of the EM calorimeter has been developed. The main technical characteristics of the design are presented. The design able to math readout constraints for a high luminosity collider experiment is discussed. 10 refs., 2 tabs., 8 figs.

  15. Crystal Clear - New crystals for LHC experiments help to improve PET scanners Exhibition LEPFest 2000

    CERN Multimedia

    2000-01-01

    Better resolution through smaller crystals Better images through higher light yieldHigh efficiency, stability and gain by using avalanche photodiodes and low noise electronics Reduced cost of crystals (1/10) through mass production

  16. Snow-avalanche impact craters in southern Norway: Their morphology and dynamics compared with small terrestrial meteorite craters

    Science.gov (United States)

    Matthews, John A.; Owen, Geraint; McEwen, Lindsey J.; Shakesby, Richard A.; Hill, Jennifer L.; Vater, Amber E.; Ratcliffe, Anna C.

    2017-11-01

    This regional inventory and study of a globally uncommon landform type reveals similarities in form and process between craters produced by snow-avalanche and meteorite impacts. Fifty-two snow-avalanche impact craters (mean diameter 85 m, range 10-185 m) were investigated through field research, aerial photographic interpretation and analysis of topographic maps. The craters are sited on valley bottoms or lake margins at the foot of steep avalanche paths (α = 28-59°), generally with an easterly aspect, where the slope of the final 200 m of the avalanche path (β) typically exceeds 15°. Crater diameter correlates with the area of the avalanche start zone, which points to snow-avalanche volume as the main control on crater size. Proximal erosional scars ('blast zones') up to 40 m high indicate up-range ejection of material from the crater, assisted by air-launch of the avalanches and impulse waves generated by their impact into water-filled craters. Formation of distal mounds up to 12 m high of variable shape is favoured by more dispersed down-range deposition of ejecta. Key to the development of snow-avalanche impact craters is the repeated occurrence of topographically-focused snow avalanches that impact with a steep angle on unconsolidated sediment. Secondary craters or pits, a few metres in diameter, are attributed to the impact of individual boulders or smaller bodies of snow ejected from the main avalanche. The process of crater formation by low-density, low-velocity, large-volume snow flows occurring as multiple events is broadly comparable with cratering by single-event, high-density, high-velocity, small-volume projectiles such as small meteorites. Simple comparative modelling of snow-avalanche events associated with a crater of average size (diameter 85 m) indicates that the kinetic energy of a single snow-avalanche impact event is two orders of magnitude less than that of a single meteorite-impact event capable of producing a crater of similar size

  17. Panoramic irradiator dose mapping with pin photodiodes

    International Nuclear Information System (INIS)

    Ferreira, Danilo Cardenuto; Napolitano, Celia Marina; Bueno, Carmen Cecilia

    2011-01-01

    In this work we study the possibility of using commercial silicon PIN photodiodes (Siemens, SFH 00206) for dose mapping in the Panoramic Irradiator facility at IPEN-CNEN/SP. The chosen photodiode, that is encased in 1.2 mm thickness polymer layer, displays promising dosimetric characteristics such as small size (sensitive area of 7.00 mm 2 ), high sensitivity and low dark current (≅ 300 pA, at 0 V) together with low-cost and wide availability. The Panoramic facility is an irradiator Type II with absorbed dose certificated by International Dose Assurance Service (IDAS) offered by the International Agency Energy Atomic (IAEA). The charge registered by the diode as a function of the absorbed dose was in excellent agreement with that one calibrated by IDAS. Besides this, the easy handling and fast response of the SFH00206 diode compared to Fricke chemical dosimeters encouraged us to perform dose mapping around the source. (author)

  18. Validating numerical simulations of snow avalanches using dendrochronology: the Cerro Ventana event in Northern Patagonia, Argentina

    Directory of Open Access Journals (Sweden)

    A. Casteller

    2008-05-01

    Full Text Available The damage caused by snow avalanches to property and human lives is underestimated in many regions around the world, especially where this natural hazard remains poorly documented. One such region is the Argentinean Andes, where numerous settlements are threatened almost every winter by large snow avalanches. On 1 September 2002, the largest tragedy in the history of Argentinean mountaineering took place at Cerro Ventana, Northern Patagonia: nine persons were killed and seven others injured by a snow avalanche. In this paper, we combine both numerical modeling and dendrochronological investigations to reconstruct this event. Using information released by local governmental authorities and compiled in the field, the avalanche event was numerically simulated using the avalanche dynamics programs AVAL-1D and RAMMS. Avalanche characteristics, such as extent and date were determined using dendrochronological techniques. Model simulation results were compared with documentary and tree-ring evidences for the 2002 event. Our results show a good agreement between the simulated projection of the avalanche and its reconstructed extent using tree-ring records. Differences between the observed and the simulated avalanche, principally related to the snow height deposition in the run-out zone, are mostly attributed to the low resolution of the digital elevation model used to represent the valley topography. The main contributions of this study are (1 to provide the first calibration of numerical avalanche models for the Patagonian Andes and (2 to highlight the potential of Nothofagus pumilio tree-ring records to reconstruct past snow-avalanche events in time and space. Future research should focus on testing this combined approach in other forested regions of the Andes.

  19. Electrical and optical 3D modelling of light-trapping single-photon avalanche diode

    Science.gov (United States)

    Zheng, Tianzhe; Zang, Kai; Morea, Matthew; Xue, Muyu; Lu, Ching-Ying; Jiang, Xiao; Zhang, Qiang; Kamins, Theodore I.; Harris, James S.

    2018-02-01

    Single-photon avalanche diodes (SPADs) have been widely used to push the frontier of scientific research (e.g., quantum science and single-molecule fluorescence) and practical applications (e.g., Lidar). However, there is a typical compromise between photon detection efficiency and jitter distribution. The light-trapping SPAD has been proposed to break this trade-off by coupling the vertically incoming photons into a laterally propagating mode while maintaining a small jitter and a thin Si device layer. In this work, we provide a 3D-based optical and electrical model based on practical fabrication conditions and discuss about design parameters, which include surface texturing, photon injection position, device area, and other features.

  20. Performances of photodiode detectors for top and bottom counting detectors of ISS-CREAM experiment

    International Nuclear Information System (INIS)

    Hyun, H.J.; Anderson, T.; Angelaszek, D.; Baek, S.J.; Copley, M.; Coutu, S.; Han, J.H.; Huh, H.G.; Hwang, Y.S.; Im, S.; Jeon, H.B.; Kah, D.H.; Kang, K.H.; Kim, H.J.; Kim, K.C.; Kwashnak, K.; Lee, J.; Lee, M.H.; Link, J.T.; Lutz, L.

    2015-01-01

    The Cosmic Ray Energetics and Mass (CREAM) experiment at the International Space Station (ISS) aims to elucidate the source and acceleration mechanisms of high-energy cosmic rays by measuring the energy spectra from protons to iron. The instrument is planned for launch in 2015 at the ISS, and it comprises a silicon charge detector, a carbon target, top and bottom counting detectors, a calorimeter, and a boronated scintillator detector. The top and bottom counting detectors are developed for separating the electrons from the protons, and each of them comprises a plastic scintillator and a 20×20 silicon photodiode array. Each photodiode is 2.3 cm×2.3 cm in size and exhibits good electrical characteristics. The leakage current is measured to be less than 20 nA/cm 2 at an operating voltage. The signal-to-noise ratio is measured to be better than 70 using commercial electronics, and the radiation hardness is tested using a proton beam. A signal from the photodiode is amplified by VLSI (very-large-scale integration) charge amp/hold circuits, the VA-TA viking chip. Environmental tests are performed using whole assembled photodiode detectors of a flight version. Herein, we present the characteristics of the developed photodiode along with the results of the environmental tests

  1. Performances of photodiode detectors for top and bottom counting detectors of ISS-CREAM experiment

    Energy Technology Data Exchange (ETDEWEB)

    Hyun, H.J. [Kyungpook National University, Daegu 702-701 (Korea, Republic of); Anderson, T. [Pennsylvania State University, University Park, PA 16802 (United States); Angelaszek, D. [University of Maryland, College Park, MD 20740 (United States); Baek, S.J. [Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Copley, M. [University of Maryland, College Park, MD 20740 (United States); Coutu, S. [Pennsylvania State University, University Park, PA 16802 (United States); Han, J.H.; Huh, H.G. [University of Maryland, College Park, MD 20740 (United States); Hwang, Y.S. [Kyungpook National University, Daegu 702-701 (Korea, Republic of); Im, S. [Pennsylvania State University, University Park, PA 16802 (United States); Jeon, H.B.; Kah, D.H.; Kang, K.H.; Kim, H.J. [Kyungpook National University, Daegu 702-701 (Korea, Republic of); Kim, K.C.; Kwashnak, K. [University of Maryland, College Park, MD 20740 (United States); Lee, J. [Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Lee, M.H. [University of Maryland, College Park, MD 20740 (United States); Link, J.T. [NASA GSFC, Greenbelt, MD 20771 (United States); CRESST(USRA), Columbia, MD 21044 (United States); Lutz, L. [University of Maryland, College Park, MD 20740 (United States); and others

    2015-07-01

    The Cosmic Ray Energetics and Mass (CREAM) experiment at the International Space Station (ISS) aims to elucidate the source and acceleration mechanisms of high-energy cosmic rays by measuring the energy spectra from protons to iron. The instrument is planned for launch in 2015 at the ISS, and it comprises a silicon charge detector, a carbon target, top and bottom counting detectors, a calorimeter, and a boronated scintillator detector. The top and bottom counting detectors are developed for separating the electrons from the protons, and each of them comprises a plastic scintillator and a 20×20 silicon photodiode array. Each photodiode is 2.3 cm×2.3 cm in size and exhibits good electrical characteristics. The leakage current is measured to be less than 20 nA/cm{sup 2} at an operating voltage. The signal-to-noise ratio is measured to be better than 70 using commercial electronics, and the radiation hardness is tested using a proton beam. A signal from the photodiode is amplified by VLSI (very-large-scale integration) charge amp/hold circuits, the VA-TA viking chip. Environmental tests are performed using whole assembled photodiode detectors of a flight version. Herein, we present the characteristics of the developed photodiode along with the results of the environmental tests.

  2. Massive Formation of Equiaxed Crystals by Avalanches of Mushy Zone Segments

    Science.gov (United States)

    Ludwig, A.; Stefan-Kharicha, M.; Kharicha, A.; Wu, M.

    2017-06-01

    It is well known that the growth and motion of equiaxed crystals govern important microstructural features, especially in larger castings such as heavy ingots. To determine the origin of the equiaxed crystals, heterogeneous nucleation, and/or fragmentation of dendrite arms from columnar regions are often discussed. In the present study, we demonstrate that under certain conditions relatively large areas of mushy regions slide downward and form spectacular crystal avalanches. These avalanches crumble into thousands of dendritic fragments, whereby the larger fragments immediately sediment and the smaller proceed to behave as equiaxed crystals. Traces of such crystal avalanches can be seen by conspicuous equiaxed layers in the lower part of the casting. From the arguments in the discussion, it is believed that such a phenomenon may occur in alloys which reveal an upward solutal buoyancy in the interdendritic mush. This would include certain steels and other alloys such as Cu-Al, Pb-Sn, or Ni-Al-alloys. Moreover, the occurrence of crystal avalanches contribute to the formation of V-segregations.

  3. Visible light photodiodes and photovoltages from detonation nanodiamonds

    Czech Academy of Sciences Publication Activity Database

    Rezek, Bohuslav; Stehlík, Štěpán; Kromka, Alexander; Arnault, J.-C.; Weis, M.; Jakabovič, J.

    2016-01-01

    Roč. 1, č. 14 (2016), s. 971-975 ISSN 2059-8521 R&D Projects: GA ČR GA15-01809S Institutional support: RVO:68378271 Keywords : nanodiamond * photodiode Subject RIV: BM - Solid Matter Physics ; Magnetism

  4. Study of a silicon photodetector thermal stabilization using a Peltier cell

    International Nuclear Information System (INIS)

    Foschi, E.; Levi, G.; Quadrani, L.; Sbarra, C.; Guandalini, C.; Zuffa, M.; Sbarra, C.

    2007-01-01

    In recent years a new type of silicon photon detection device (SiPM) has been developed by many groups. These devices have strong advantages in comparison to normal photomultipliers tubes (PMT) but, being made by an array of avalanche photo diodes operated in Geiger mode, are much more sensitive to temperature changes than standard PMTs. Typical SiPM gain, in fact, varies from 3 to 5 percent per Celsius degree. In space environment, where operative temperature can change from -40 deg.C to 50 deg.C, a definitive temperature stabilization is needed. In order to use SiPMs in space we have developed a thermoelectric model of a Peltier cell that allows us to simulate the final detector circuit assembly predicting the operative temperatures and the adsorbed powers. The characteristics of the model and the obtained results are shown. (authors)

  5. Performance of a PET detector module utilizing an array of silicon photodiodes to identify the crystal of interaction

    International Nuclear Information System (INIS)

    Moses, W.W.; Derenzo, S.E.; Nutt, R.; Digby, W.M.; Williams, C.W.; Andreaco, M.

    1993-01-01

    The authors initial performance results for a new multi-layer PET detector module consisting of an array of 3 mm square by 30 mm deep BGO crystals coupled on one end to a single photomultiplier tube and on the opposite end to an array of 3 mm square silicon photodiodes. The photomultiplier tube provides an accurate timing pulse and energy discrimination for all the crystals in the module, while the silicon photodiodes identify the crystal of interaction. When a single BGO crystal at +25 C is excited with 511 keV photons, the authors measure a photodiode signal centered at 700 electrons (e - ) with noise of 375 e - fwhm. When a four crystal/photodiode module is excited with a collimated line source of 511 keV photons, the crystal of interaction is correctly identified 82% of the time. The misidentification rate can be greatly reduced and an 8 x 8 crystal/photodiode module constructed by using thicker depletion layer photodiodes or cooling to 0 C

  6. A concept for optimizing avalanche rescue strategies using a Monte Carlo simulation approach.

    Directory of Open Access Journals (Sweden)

    Ingrid Reiweger

    Full Text Available Recent technical and strategical developments have increased the survival chances for avalanche victims. Still hundreds of people, primarily recreationists, get caught and buried by snow avalanches every year. About 100 die each year in the European Alps-and many more worldwide. Refining concepts for avalanche rescue means to optimize the procedures such that the survival chances are maximized in order to save the greatest possible number of lives. Avalanche rescue includes several parameters related to terrain, natural hazards, the people affected by the event, the rescuers, and the applied search and rescue equipment. The numerous parameters and their complex interaction make it unrealistic for a rescuer to take, in the urgency of the situation, the best possible decisions without clearly structured, easily applicable decision support systems. In order to analyse which measures lead to the best possible survival outcome in the complex environment of an avalanche accident, we present a numerical approach, namely a Monte Carlo simulation. We demonstrate the application of Monte Carlo simulations for two typical, yet tricky questions in avalanche rescue: (1 calculating how deep one should probe in the first passage of a probe line depending on search area, and (2 determining for how long resuscitation should be performed on a specific patient while others are still buried. In both cases, we demonstrate that optimized strategies can be calculated with the Monte Carlo method, provided that the necessary input data are available. Our Monte Carlo simulations also suggest that with a strict focus on the "greatest good for the greatest number", today's rescue strategies can be further optimized in the best interest of patients involved in an avalanche accident.

  7. Modeling the influence of snow cover temperature and water content on wet-snow avalanche runout

    Directory of Open Access Journals (Sweden)

    C. Vera Valero

    2018-03-01

    Full Text Available Snow avalanche motion is strongly dependent on the temperature and water content of the snow cover. In this paper we use a snow cover model, driven by measured meteorological data, to set the initial and boundary conditions for wet-snow avalanche calculations. The snow cover model provides estimates of snow height, density, temperature and liquid water content. This information is used to prescribe fracture heights and erosion heights for an avalanche dynamics model. We compare simulated runout distances with observed avalanche deposition fields using a contingency table analysis. Our analysis of the simulations reveals a large variability in predicted runout for tracks with flat terraces and gradual slope transitions to the runout zone. Reliable estimates of avalanche mass (height and density in the release and erosion zones are identified to be more important than an exact specification of temperature and water content. For wet-snow avalanches, this implies that the layers where meltwater accumulates in the release zone must be identified accurately as this defines the height of the fracture slab and therefore the release mass. Advanced thermomechanical models appear to be better suited to simulate wet-snow avalanche inundation areas than existing guideline procedures if and only if accurate snow cover information is available.

  8. Hybrid phase transition into an absorbing state: Percolation and avalanches

    Science.gov (United States)

    Lee, Deokjae; Choi, S.; Stippinger, M.; Kertész, J.; Kahng, B.

    2016-04-01

    Interdependent networks are more fragile under random attacks than simplex networks, because interlayer dependencies lead to cascading failures and finally to a sudden collapse. This is a hybrid phase transition (HPT), meaning that at the transition point the order parameter has a jump but there are also critical phenomena related to it. Here we study these phenomena on the Erdős-Rényi and the two-dimensional interdependent networks and show that the hybrid percolation transition exhibits two kinds of critical behaviors: divergence of the fluctuations of the order parameter and power-law size distribution of finite avalanches at a transition point. At the transition point global or "infinite" avalanches occur, while the finite ones have a power law size distribution; thus the avalanche statistics also has the nature of a HPT. The exponent βm of the order parameter is 1 /2 under general conditions, while the value of the exponent γm characterizing the fluctuations of the order parameter depends on the system. The critical behavior of the finite avalanches can be described by another set of exponents, βa and γa. These two critical behaviors are coupled by a scaling law: 1 -βm=γa .

  9. Photodiode area effect on performance of X-ray CMOS active pixel sensors

    Science.gov (United States)

    Kim, M. S.; Kim, Y.; Kim, G.; Lim, K. T.; Cho, G.; Kim, D.

    2018-02-01

    Compared to conventional TFT-based X-ray imaging devices, CMOS-based X-ray imaging sensors are considered next generation because they can be manufactured in very small pixel pitches and can acquire high-speed images. In addition, CMOS-based sensors have the advantage of integration of various functional circuits within the sensor. The image quality can also be improved by the high fill-factor in large pixels. If the size of the subject is small, the size of the pixel must be reduced as a consequence. In addition, the fill factor must be reduced to aggregate various functional circuits within the pixel. In this study, 3T-APS (active pixel sensor) with photodiodes of four different sizes were fabricated and evaluated. It is well known that a larger photodiode leads to improved overall performance. Nonetheless, if the size of the photodiode is > 1000 μm2, the degree to which the sensor performance increases as the photodiode size increases, is reduced. As a result, considering the fill factor, pixel-pitch > 32 μm is not necessary to achieve high-efficiency image quality. In addition, poor image quality is to be expected unless special sensor-design techniques are included for sensors with a pixel pitch of 25 μm or less.

  10. Radon measurements with a PIN photodiode

    International Nuclear Information System (INIS)

    Martin-Martin, A.; Gutierrez-Villanueva, J.L.; Munoz, J.M.; Garcia-Talavera, M.; Adamiec, G.; Iniguez, M.P.

    2006-01-01

    Silicon photodiodes are well suited to detect alphas coming from different sources as neutron reactions or radon daughters. In this work a radon in air detecting device, using an 18x18 mm silicon PIN photodiode is studied. The ionized airborne decay products formed during radon diffusion were focused by an accelerating high voltage to the PIN surface. Several conducting rings were disposed inside a cylindrical PVC vessel in such a way that they reproduced the electric field created by a punctual charge located behind PIN position. Alpha spectra coming from the neutral and ionized species deposited on the PIN surface, dominated by 218 Po and 214 Po progeny peaks, were recorded for varying conditions. Those include radon concentration from a Pylon source, high voltage (thousands of volts) and PIN inverse bias voltage. Different parameters such as temperature and humidity were also registered during data acquisition. The increase in the particle collection efficiency with respect to zero electric field was compared with the corresponding to a parallel plates configuration. A discussion is made in terms of the most appropriate voltages for different radon concentrations

  11. Particle and photon detection for a neutron radiative decay experiment

    Energy Technology Data Exchange (ETDEWEB)

    Gentile, T.R. [National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States)], E-mail: thomas.gentile@nist.gov; Dewey, M.S.; Mumm, H.P.; Nico, J.S.; Thompson, A.K. [National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States); Chupp, T.E. [University of Michigan, Ann Arbor, MI 48109 (United States); Cooper, R.L. [University of Michigan, Ann Arbor, MI 48109 (United States)], E-mail: cooperrl@umich.edu; Fisher, B.M.; Kremsky, I.; Wietfeldt, F.E. [Tulane University, New Orleans, LA 70118 (United States); Kiriluk, K.G.; Beise, E.J. [University of Maryland, College Park, MD 20742 (United States)

    2007-08-21

    We present the particle and photon detection methods employed in a program to observe neutron radiative beta-decay. The experiment is located at the NG-6 beam line at the National Institute of Standards and Technology Center for Neutron Research. Electrons and protons are guided by a 4.6 T magnetic field and detected by a silicon surface barrier detector. Photons with energies between 15 and 750 keV are registered by a detector consisting of a bismuth germanate scintillator coupled to a large area avalanche photodiode. The photon detector operates at a temperature near 80 K in the bore of a superconducting magnet. We discuss CsI as an alternative scintillator, and avalanche photodiodes for direct detection of photons in the 0.1-10 keV range.

  12. Single-photon compressive imaging with some performance benefits over raster scanning

    International Nuclear Information System (INIS)

    Yu, Wen-Kai; Liu, Xue-Feng; Yao, Xu-Ri; Wang, Chao; Zhai, Guang-Jie; Zhao, Qing

    2014-01-01

    A single-photon imaging system based on compressed sensing has been developed to image objects under ultra-low illumination. With this system, we have successfully realized imaging at the single-photon level with a single-pixel avalanche photodiode without point-by-point raster scanning. From analysis of the signal-to-noise ratio in the measurement we find that our system has much higher sensitivity than conventional ones based on point-by-point raster scanning, while the measurement time is also reduced. - Highlights: • We design a single photon imaging system with compressed sensing. • A single point avalanche photodiode is used without raster scanning. • The Poisson shot noise in the measurement is analyzed. • The sensitivity of our system is proved to be higher than that of raster scanning

  13. Dose determination on buildup region using photodiodes

    International Nuclear Information System (INIS)

    Khoury, H.J.; Lopes, F.J.; Melo, F. de A.

    1989-01-01

    A clinical dosemeter using photodiode BPW-34 was developed, allowing the determination of dose on buildup region. The measures were made with X-rays beam of linear accelerator and with gamma radiation of cobalt 60. The results were compared with others made in a ionization chamber. (C.G.C.) [pt

  14. Indium phosphide-based monolithically integrated PIN waveguide photodiode readout for resonant cantilever sensors

    Energy Technology Data Exchange (ETDEWEB)

    Siwak, N. P. [Department of Electrical and Computer Engineering, Institute for Systems Research, University of Maryland, College Park, Maryland 20742 (United States); Laboratory for the Physical Sciences, 8050 Greenmead Drive, College Park, Maryland 20740 (United States); Fan, X. Z.; Ghodssi, R. [Department of Electrical and Computer Engineering, Institute for Systems Research, University of Maryland, College Park, Maryland 20742 (United States); Kanakaraju, S.; Richardson, C. J. K. [Laboratory for the Physical Sciences, 8050 Greenmead Drive, College Park, Maryland 20740 (United States)

    2014-10-06

    An integrated photodiode displacement readout scheme for a microelectromechanical cantilever waveguide resonator sensing platform is presented. III-V semiconductors are used to enable the monolithic integration of passive waveguides with active optical components. This work builds upon previously demonstrated results by measuring the displacement of cantilever waveguide resonators with on-chip waveguide PIN photodiodes. The on-chip integration of the readout provides an additional 70% improvement in mass sensitivity compared to off-chip photodetector designs due to measurement stability and minimized coupling loss. In addition to increased measurement stability, reduced packaging complexity is achieved due to the simplicity of the readout design. We have fabricated cantilever waveguides with integrated photodetectors and experimentally characterized these cantilever sensors with monolithically integrated PIN photodiodes.

  15. Avalanche outbreaks emerging in cooperative contagions

    Science.gov (United States)

    Cai, Weiran; Chen, Li; Ghanbarnejad, Fakhteh; Grassberger, Peter

    2015-11-01

    The spreading of contagions can exhibit a percolation transition, which separates transitory prevalence from outbreaks that reach a finite fraction of the population. Such transitions are commonly believed to be continuous, but empirical studies have shown more violent spreading modes when the participating agents are not limited to one type. Striking examples include the co-epidemic of the Spanish flu and pneumonia that occurred in 1918 (refs , ), and, more recently, the concurrent prevalence of HIV/AIDS and a host of diseases. It remains unclear to what extent an outbreak in the presence of interacting pathogens differs from that due to an ordinary single-agent process. Here we study a mechanistic model for understanding contagion processes involving inter-agent cooperation. Our stochastic simulations reveal the possible emergence of a massive avalanche-like outbreak right at the threshold, which is manifested as a discontinuous phase transition. Such an abrupt change arises only if the underlying network topology supports a bottleneck for cascaded mutual infections. Surprisingly, all these discontinuous transitions are accompanied by non-trivial critical behaviours, presenting a rare case of hybrid transition. The findings may imply the origin of catastrophic occurrences in many realistic systems, from co-epidemics to financial contagions.

  16. High gain multigap avalanche detectors for Cerenkov ring imaging

    Energy Technology Data Exchange (ETDEWEB)

    Gilmore, R.S.; Lavender, W.M.; Leith, D.W.G.S.; Williams, S.H.

    1980-10-01

    We report on a continuing study of multigap parallel plate avalanche chambers, primarily as photoelectron detectors for use with Cerenkov ring imaging counters. By suitable control of the fields in successive gaps and by introducing screens to reduce photon feedback to the cathode the gain many be increased considerably. We have obtained gains in excess of 6 x 10/sup 7/ for photoelectrons with a good pulse height spectrum and expect to increase this further. We discuss the use of resistive anodes to give avalanche positions in two dimensions by charge division.

  17. A room temperature LSO/PIN photodiode PET detector module that measures depth of interaction

    International Nuclear Information System (INIS)

    Moses, W.W.; Derenzo, S.E.; Melcher, C.L.; Manente, R.A.

    1994-11-01

    We present measurements of a 4 element PET detector module that uses a 2x2 array of 3 mm square PIN photodiodes to both measure the depth of interaction (DOI) and identify the crystal of interaction. Each photodiode is coupled to one end of a 3x3x25 mm LSO crystal, with the opposite ends of all 4 crystals attached to a single PMT that provides a timing signal and initial energy discrimination. Each LSO crystal is coated with a open-quotes lossyclose quotes reflector, so the ratio of light detected in the photodiode and PMT depends on the position of interaction in the crystal, and is used to determine this position on an event by event basis. This module is operated at +25 degrees C with a photodiode amplifier peaking time of 2 μs. When excited by a collimated beam of 511 keV photons at the photodiode end of the module (i.e. closest to the patient), the DOI resolution is 4 mm fwhm and the crystal of interaction is identified correctly 95% of the time. When excited at the opposite end of the module, the DOI resolution is 13 mm fwhm and the crystal of interaction is identified correctly 73% of the time. The channel to channel variations in performance are minimal

  18. New advances for modelling the debris avalanches

    Science.gov (United States)

    Cuomo, Sabatino; Cascini, Leonardo; Pastor, Manuel; Castorino, Giuseppe Claudio

    2013-04-01

    Flow-like landslides are a major global hazard and they occur worldwide causing a large number of casualties, significant structural damages to property and infrastructures as well as economic losses. When involving open slopes, these landslides often occur in triangular source areas where initial slides turn into avalanches through further failures and/or eventual soil entrainment. This paper deals with the numerical modelling of the propagation stage of debris avalanches which provides information such as the propagation pattern of the mobilized material, its velocity, thickness and run-out distance. In the paper, a "depth integrated" model is used which allows: i) adequately taking into account the irregular topography of real slopes which greatly affect the propagation stage and ii) using a less time consuming model than fully 3D approaches. The used model is named "GeoFlow_SPH" and it was formerly applied to theoretical, experimental and real case histories (Pastor et al., 2009; Cascini et al., 2012). In this work the behavior of debris avalanches is analyzed with special emphasis on the apical angle, one of the main features of this type of landslide, in relation to soil rheology, hillslope geometry and features of triggering area. Furthermore, the role of erosion has been investigated with reference to the uppermost parts of open slopes with a different steepness. These analyses are firstly carried out for simplified benchmark slopes, using both water-like materials (with no shear strength) and debris type materials. Then, three important case studies of Campania region (Cervinara, Nocera Inferiore e Sarno) are analyzed where debris avalanches involved pyroclastic soils originated from the eruptive products of Vesusius volcano. The results achieved for both benchmark slopes and real case histories outline the key role played by the erosion on the whole propagation stage of debris avalanches. The results are particularly satisfactory since they indicate the

  19. The μs and ns mode modulation system for grid controlled gun of the HESYRL linac

    International Nuclear Information System (INIS)

    Wang, Guicheng; Hong, Jun; Pei, Yuanji

    1988-01-01

    A μs and ns mode modulation system has been developed for the grid-controlled gun in the HESYRL. The gun drived by this system generated 1A and 500 MA pulse current for μs and ns mode respectively. In the ns mode modulation pulse formulation system, the sharper was built up using one transistor 3DA87D as avalanche switch and a shortcircuit coaxal cable as waveform sharp element. Outline of the μs mode system and details of the ns mode system are presented. (author)

  20. Scaling behavior of individual barkhausen avalanches in nucleation-mediated magnetization reversal processes

    Energy Technology Data Exchange (ETDEWEB)

    Im, Mi-Young; Fischer, Peter; Kim, Dong-Hyun; Shin, Sung-Chul

    2009-11-09

    We report the scaling behavior of Barkhausen avalanches along the hysteresis loop of a CoCrPt alloy film with perpendicular magnetic anisotropy for every field step of 200 Oe. Individual Barkhausen avalanches are directly observed via high-resolution soft X-ray microscopy with a spatial resolution of 15 nm. The Barkhausen avalanches exhibit a power-law scaling behavior, where the scaling exponent of the power-law distribution drastically changes from 1 {+-} 0.04 to 1.47 {+-} 0.03 as the applied magnetic field approaches the coercivity of the CoCrPt film. We infer that this is due to the coupling of adjacent domains.

  1. Geiger-Nuttall Law for Nuclei in Strong Electromagnetic Fields

    Science.gov (United States)

    Delion, D. S.; Ghinescu, S. A.

    2017-11-01

    We investigate the influence of a strong laser electromagnetic field on the α -decay rate by using the Hennenberger frame of reference. We introduce an adimensional parameter D =S0/R0, where R0 is the geometrical nuclear radius and S0˜√{I }/ω2 is a length parameter depending on the laser intensity I and frequency ω . We show that the barrier penetrability has a strong increase for intensities corresponding to D >Dcrit=1 , due to the fact that the resulting Coulomb potential becomes strongly anisotropic even for spherical nuclei. As a consequence, the contribution of the monopole term increases the barrier penetrability by 2 orders of magnitude, while the total contribution has an effect of 6 orders of magnitude at D ˜3 Dcrit. In the case of deformed nuclei, the electromagnetic field increases the penetrability by an additional order of magnitude for a quadrupole deformation β2˜0.3 . The influence of the electromagnetic field can be expressed in terms of a shifted Geiger-Nuttal law by a term depending on S0 and deformation.

  2. First Townsend coefficient of organic vapour in avalanche counters

    International Nuclear Information System (INIS)

    Sernicki, J.

    1990-01-01

    A new concept is presented in the paper for implementing the proven method of determining the first Townsend coefficient (α) of gases using an avalanche counter. The A and B gas constants, interrelated by the expression α/p=A exp[-B/(K/p)], are analyzed. Parallel-plate avalanche counters (PPAC) with an electrode spacing d from 0.1 to 0.4 cm have been employed for the investigation, arranged to register low-energy alpha particles at n-heptane vapour pressures of p≥5 Torr. An in-depth discussion is given, covering the veracity and the behaviour vs K/p, of the n-heptane A and B constants determined at reduced electric-field intensity values ranging from 173.5 to 940 V/cm Torr; the constants have been found to depend upon d. The results of the investigation are compared to available data of the α coefficient of organic vapours used in avalanche counters. The PPAC method of determining α reveals some imperfections at very low values of the pd product. (orig.)

  3. AN MHD AVALANCHE IN A MULTI-THREADED CORONAL LOOP

    Energy Technology Data Exchange (ETDEWEB)

    Hood, A. W.; Cargill, P. J.; Tam, K. V. [School of Mathematics and Statistics, University of St Andrews, St Andrews, Fife, KY16 9SS (United Kingdom); Browning, P. K., E-mail: awh@st-andrews.ac.uk [School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester, M13 9PL (United Kingdom)

    2016-01-20

    For the first time, we demonstrate how an MHD avalanche might occur in a multithreaded coronal loop. Considering 23 non-potential magnetic threads within a loop, we use 3D MHD simulations to show that only one thread needs to be unstable in order to start an avalanche even when the others are below marginal stability. This has significant implications for coronal heating in that it provides for energy dissipation with a trigger mechanism. The instability of the unstable thread follows the evolution determined in many earlier investigations. However, once one stable thread is disrupted, it coalesces with a neighboring thread and this process disrupts other nearby threads. Coalescence with these disrupted threads then occurs leading to the disruption of yet more threads as the avalanche develops. Magnetic energy is released in discrete bursts as the surrounding stable threads are disrupted. The volume integrated heating, as a function of time, shows short spikes suggesting that the temporal form of the heating is more like that of nanoflares than of constant heating.

  4. Observation of the Avalanche of Runaway Electrons in Air in a Strong Electric Field

    Science.gov (United States)

    Gurevich, A. V.; Mesyats, G. A.; Zybin, K. P.; Yalandin, M. I.; Reutova, A. G.; Shpak, V. G.; Shunailov, S. A.

    2012-08-01

    The generation of an avalanche of runaway electrons is demonstrated for the first time in a laboratory experiment. Two flows of runaway electrons are formed sequentially in an extended air discharge gap at the stage of delay of a pulsed breakdown. The first, picosecond, runaway electron flow is emitted in the cathode region where the field is enhanced. Being accelerated in the gap, this beam generates electrons due to impact ionization. These secondary electrons form a delayed avalanche of runaway electrons if the field is strong enough. The properties of the avalanche correspond to the existing notions about the runaway breakdown in air. The measured current of the avalanche exceeds up to an order the current of the initiating electron beam.

  5. CsI(Tl)-photodiode detectors for gamma-ray spectroscopy

    CERN Document Server

    Fioretto, E; Viesti, G; Cinausero, M; Zuin, L; Fabris, D; Lunardon, M; Nebbia, G; Prete, G

    2000-01-01

    We report on the performances of CsI(Tl)-photodiode detectors for gamma-ray spectroscopy applications. Light output yield and energy resolution have been measured for different crystals and read-out configurations.

  6. Evaluating terrain based criteria for snow avalanche exposure ratings using GIS

    Science.gov (United States)

    Delparte, Donna; Jamieson, Bruce; Waters, Nigel

    2010-05-01

    Snow avalanche terrain in backcountry regions of Canada is increasingly being assessed based upon the Avalanche Terrain Exposure Scale (ATES). ATES is a terrain based classification introduced in 2004 by Parks Canada to identify "simple", "challenging" and "complex" backcountry areas. The ATES rating system has been applied to well over 200 backcountry routes, has been used in guidebooks, trailhead signs and maps and is part of the trip planning component of the AVALUATOR™, a simple decision-support tool for backcountry users. Geographic Information Systems (GIS) offers a means to model and visualize terrain based criteria through the use of digital elevation model (DEM) and land cover data. Primary topographic variables such as slope, aspect and curvature are easily derived from a DEM and are compatible with the equivalent evaluation criteria in ATES. Other components of the ATES classification are difficult to extract from a DEM as they are not strictly terrain based. An overview is provided of the terrain variables that can be generated from DEM and land cover data; criteria from ATES which are not clearly terrain based are identified for further study or revision. The second component of this investigation was the development of an algorithm for inputting suitable ATES criteria into a GIS, thereby mimicking the process avalanche experts use when applying the ATES classification to snow avalanche terrain. GIS based classifications were compared to existing expert assessments for validity. The advantage of automating the ATES classification process through GIS is to assist avalanche experts with categorizing and mapping remote backcountry terrain.

  7. Response of commercial photodiodes for application in alpha spectrometry

    International Nuclear Information System (INIS)

    Ferreira Filho, Alfredo Lopes

    1998-06-01

    The use of semiconductor detector for ionizing radiations spectrometry and dosimetry has been growing in the last years due to its characteristics of fast response, good efficiency for unit of volume and excellent resolution. Since the working principle of a semiconductor detector is identical to that of the semiconductor junctions of commercial electronic devices, a study was carried out on the PIN-photodiodes response, aiming at set up an alpha spectrometry system of low cost and easy acquisition. The tested components have the following characteristics: active area varying between 13.2 and 25 mm 2 , window of thickness equal or lower than 57 mg/cm 2 , depletion area with depth ranging from 10 to 300 μm and junction capacitance of 16 to 20 pF.Am-241, Cm-244, U-233 and Np-237 alpha sources produced by electrodeposition were used to evaluate the response of the devices as a function of the radiation energy. The results have shown a linear response of the photodiodes with the incident alpha particle energy. The resolution varied from 1.6% to 0.45% and the better detection efficiency found was about 7.2. The low cost of the photodiodes and the excellent results obtained at room temperature make such components very attractive for teaching purposes for environmental monitoring. (author)

  8. A mineralogical and granulometric study of Cayambe volcano debris avalanche deposit

    Science.gov (United States)

    Detienne, M.; Delmelle, P.; Guevara, A.; Samaniego, P.; Bustillos, J.; Sonnet, P.; Opfergelt, S.

    2013-12-01

    Volcano flank/sector collapse represents one of the most catastrophic volcanic hazards. Various volcanic and non-volcanic processes are known to decrease the stability of a volcanic cone, eventually precipitating its gravitational failure. Among them, hydrothermal alteration of volcanic rocks leading to clay mineral formation is recognized as having a large negative impact on rock strength properties. Furthermore, the presence of hydrothermal clays in the collapsing mass influences the behavior of the associated volcanic debris avalanche. In particular, clay-containing debris avalanches seem to travel farther and spread more widely than avalanches of similar volume but which do not incorporate hydrothermally-altered materials. However, the relationship between hydrothermal alteration, flank collapse and debris avalanche behavior is not well understood. The objective of this study is to better determine the volume and composition of hydrothermal clay minerals in the poorly characterized debris avalanche deposit (DAD) of Cayambe composite volcano, located in a densely populated area ~70 km northeast of Quito, Ecuador. Cayambe DAD originated from a sector collapse, which occurred less than 200 ka ago. The DAD is 10-20 m thick and has an estimated total volume of ~0.85 Km3. The H/L ratio (where H is the vertical drop and L is the travel distance of the avalanche) for Cayambe DAD is ~0.095, suggesting a high mobility. In the medial-distal zone, at 9-20 km from its source, the DAD consists of an unstratified and unsorted matrix supporting millimetric to metric clasts. It has a matrix facies (i.e. rich in particles DAD behaved as a cohesive debris flow. Analysis of 13 matrix samples reveals a large variability in particle size distribution. This may reflect poor mixing of the collapsed material during transport. The clay fraction content in the matrix ranges from 15 to 30 wt.%, and does not show a relationship with the sample position in the DAD. Mineralogical

  9. Critical state transformation in hard superconductors resulting from thermomagnetic avalanches

    International Nuclear Information System (INIS)

    Chabanenko, V.V.; Kuchuk, E.I.; Rusakov, V.F.; Abaloszewa, I.; Nabialek, A.; Perez-Rodriguez, F.

    2016-01-01

    The results of experimental investigations of magnetic flux dynamics in finite superconductors, obtained using integral and local measurements methods, are presented. Local methods were aimed at clarifying the role of demagnetizing factor in dynamic formation of a complex magnetic structure of the critical state of hard superconductors. To understand the reasons for cardinal restructuring of the induction, we further analyzed the literature data of flux dynamics visualization during avalanches, obtained by magneto-optical methods. New features in the behavior of the magnetic flux during and after the avalanche were discovered. Two stages of the formation of the induction structures in the avalanche area were established, i.e. of homogeneous and heterogeneous filling with the magnetic flux. The mechanism of the inversion of the induction profile was considered. Oscillations in the speed of the front of the magnetic flux were revealed. Transformation of the critical state near the edge of the sample was analyzed. The role of thermal effects and of de-magnetizing factor in the dissipative flux dynamics was shown. Generalized information allowed, in the framework of the Bean concept, to present a model the transformation of the picture of the induction of the critical state and of the superconducting currents of a finite superconductor as a result of flux avalanches for two regimes - of screening and trapping of the magnetic flux.

  10. Avalanches in a Bose-Einstein condensate

    NARCIS (Netherlands)

    Schuster, J.; Marte, A.; Amtage, S.; Sang, B.; Rempe, G.; Beijerinck, H.C.W.

    2001-01-01

    Collisional avalanches are identified to be responsible for an 8-fold increase of the initial loss rate of a large 87Rb condensate. We show that the collisional opacity of an ultracold gas exhibits a critical value. When exceeded, losses due to inelastic collisions are substantially enhanced. Under

  11. On-chip integrated functional near infra-red spectroscopy (fNIRS) photoreceiver for portable brain imaging

    Science.gov (United States)

    Kamrani, Ehsan

    Optical brain imaging using functional near infra-red spectroscopy (fNIRS) offers a direct and noninvasive tool for monitoring of blood oxygenation. fNIRS is a noninvasive, safe, minimally intrusive, and high temporal-resolution technique for real-time and long-term brain imaging. It allows detecting both fast-neuronal and slow-hemodynamic signals. Besides the significant advantages of fNIRS systems, they still suffer from few drawbacks including low spatial-resolution, moderately high-level noise and high-sensitivity to movement. In order to overcome the limitations of currently available non-portable fNIRS systems, we have introduced a new low-power, miniaturized on-chip photodetector front-end intended for portable fNIRS systems. It includes silicon avalanche photodiode (SiAPD), Transimpedance amplifier (TIA), and Quench- Reset circuitry implemented using standard CMOS technologies to operate in both linear and Geiger modes. So it can be applied for both continuous-wave fNIRS (CW-fNIRS) and also single-photon counting applications. Several SiAPDs have been implemented in novel structures and shapes (Rectangular, Octagonal, Dual, Nested, Netted, Quadratic and Hexadecagonal) using different premature edge breakdown prevention techniques. The main characteristics of the SiAPDs are validated and the impact of each parameter and the device simulators (TCAD, COMSOL, etc.) have been studied based on the simulation and measurement results. Proposed techniques exhibit SiAPDs with high avalanche-gain (up to 119), low breakdown-voltage (around 12V) and high photon-detection efficiency (up to 72% in NIR region) in additional to a low dark-count rate (down to 30Hz at 1V excess bias voltage). Three new high gain-bandwidth product (GBW) and low-noise TIAs are introduced and implemented based on distributed-gain concept, logarithmic-amplification and automatic noise-rejection and have been applied in linear-mode of operation. The implemented TIAs offer a power

  12. The AX-PET demonstrator-Design, construction and characterization

    International Nuclear Information System (INIS)

    Beltrame, P.; Bolle, E.; Braem, A.; Casella, C.; Chesi, E.; Clinthorne, N.; De Leo, R.; Dissertori, G.; Djambazov, L.; Fanti, V.; Heller, M.; Joram, C.; Kagan, H.; Lustermann, W.; Meddi, F.; Nappi, E.; Nessi-Tedaldi, F.; Oliver, J.F.; Pauss, F.; Rafecas, M.

    2011-01-01

    Axial PET is a novel geometrical concept for Positron Emission Tomography (PET), based on layers of long scintillating crystals axially aligned with the bore axis. The axial coordinate is obtained from arrays of wavelength shifting (WLS) plastic strips placed orthogonally to the crystals. This article describes the design, construction and performance evaluation of a demonstrator set-up which consists of two identical detector modules, used in coincidence. Each module comprises 48 LYSO crystals of 100 mm length and 156 WLS strips. Crystals and strips are readout by Geiger-mode Avalanche Photo Diodes (G-APDs). The signals from the two modules are processed by fully analog front-end electronics and recorded in coincidence by a VME-based data acquisition system. Measurements with point-like 22 Na sources, with the modules used both individually and in coincidence mode, allowed for a complete performance evaluation up to the focal plane reconstruction of point sources. The results obtained are in good agreement with expectations and proved the set-up to be ready for the next evaluation phase with PET phantoms filled with radiotracers.

  13. PEP-4 geiger-mode hexagonal calorimeter

    International Nuclear Information System (INIS)

    Wenzel, W.A.

    1982-01-01

    The design and performance of the calorimeter are briefly described. Design aspects include illustrations of the active volume of the detector, edge connections, module assembly and analog electronics. Performance data for cosmic rays and radiation sources, including efficiency and channel sensitivity are discussed

  14. Avalanche effect in the planar array of superheated superconductors

    International Nuclear Information System (INIS)

    Meagher, G.; Pond, J.; Kotlicki, A.; Turrell, B.G.; Eska, G.; Drukier, A.K.

    1996-01-01

    An avalanche effect has been observed in a cryogenic detector based on the planar array of superheated superconductors (PASS). The indium PASS, fabricated by photolithography on a mylar substrate, consisted of 40 well-separated lines each containing about 175 spheres of diameter 18 μm and separation 20 μm with those at the end being shielded by superconducting wire. The magnetic field was applied in the PASS plane parallel to the lines. Avalanche events in which several granules changed their state from superconducting to normal were triggered by the nucleation of the transition in a single grain by an alpha particle. (author)

  15. Avalanche size scaling in sheared three-dimensional amorphous solid

    DEFF Research Database (Denmark)

    Bailey, Nicholas; Schiøtz, Jakob; Lemaître, A.

    2007-01-01

    We study the statistics of plastic rearrangement events in a simulated amorphous solid at T=0. Events are characterized by the energy release and the "slip volume", the product of plastic strain and system volume. Their distributions for a given system size L appear to be exponential......, but a characteristic event size cannot be inferred, because the mean values of these quantities increase as L-alpha with alpha similar to 3/2. In contrast with results obtained in 2D models, we do not see simply connected avalanches. The exponent suggests a fractal shape of the avalanches, which is also evidenced...

  16. Analysis of avalanche risk factors in backcountry terrain based on usage frequency and accident data in Switzerland

    Science.gov (United States)

    Techel, F.; Zweifel, B.; Winkler, K.

    2015-09-01

    Recreational activities in snow-covered mountainous terrain in the backcountry account for the vast majority of avalanche accidents. Studies analyzing avalanche risk mostly rely on accident statistics without considering exposure (or the elements at risk), i.e., how many, when and where people are recreating, as data on recreational activity in the winter mountains are scarce. To fill this gap, we explored volunteered geographic information on two social media mountaineering websites - bergportal.ch and camptocamp.org. Based on these data, we present a spatiotemporal pattern of winter backcountry touring activity in the Swiss Alps and compare this with accident statistics. Geographically, activity was concentrated in Alpine regions relatively close to the main Swiss population centers in the west and north. In contrast, accidents occurred equally often in the less-frequented inner-alpine regions. Weekends, weather and avalanche conditions influenced the number of recreationists, while the odds to be involved in a severe avalanche accident did not depend on weekends or weather conditions. However, the likelihood of being involved in an accident increased with increasing avalanche danger level, but also with a more unfavorable snowpack containing persistent weak layers (also referred to as an old snow problem). In fact, the most critical situation for backcountry recreationists and professionals occurred on days and in regions when both the avalanche danger was critical and when the snowpack contained persistent weak layers. The frequently occurring geographical pattern of a more unfavorable snowpack structure also explains the relatively high proportion of accidents in the less-frequented inner-alpine regions. These results have practical implications: avalanche forecasters should clearly communicate the avalanche danger and the avalanche problem to the backcountry user, particularly if persistent weak layers are of concern. Professionals and recreationists, on the

  17. Long-wavelength photonic integrated circuits and avalanche photodetectors

    Science.gov (United States)

    Tsou, Yi-Jen D.; Zaytsev, Sergey; Pauchard, Alexandre; Hummel, Steve; Lo, Yu-Hwa

    2001-10-01

    Fast-growing internet traffic volume require high data communication bandwidth over longer distances. Access network bottlenecks put pressure on short-range (SR) telecommunication systems. To effectively address these datacom and telecom market needs, low-cost, high-speed laser modules at 1310 to 1550 nm wavelengths and avalanche photodetectors are required. The great success of GaAs 850nm VCSEls for Gb/s Ethernet has motivated efforts to extend VCSEL technology to longer wavelengths in the 1310 and 1550 nm regimes. However, the technological challenges associated with materials for long wavelength VCSELs are tremendous. Even with recent advances in this area, it is believed that significant additional development is necessary before long wavelength VCSELs that meet commercial specifications will be widely available. In addition, the more stringent OC192 and OC768 specifications for single-mode fiber (SMF) datacom may require more than just a long wavelength laser diode, VCSEL or not, to address numerous cost and performance issues. We believe that photonic integrated circuits (PICs), which compactly integrate surface-emitting lasers with additional active and passive optical components with extended functionality, will provide the best solutions to today's problems. Photonic integrated circuits have been investigated for more than a decade. However, they have produced limited commercial impact to date primarily because the highly complicated fabrication processes produce significant yield and device performance issues. In this presentation, we will discuss a new technology platform of InP-based PICs compatible with surface-emitting laser technology, as well as a high data rate externally modulated laser module. Avalanche photodetectors (APDs) are the key component in the receiver to achieve high data rate over long transmission distance because of their high sensitivity and large gain- bandwidth product. We have used wafer fusion technology to achieve In

  18. Fractal multiplication of electron avalanches and streamers: new mechanism of electrical breakdown?

    International Nuclear Information System (INIS)

    Ficker, T

    2007-01-01

    Long-lasting problems concerning peculiar statistical behaviour of high populated electron avalanches have been analysed. These avalanches are precursors of streamer breakdown in gases. The present streamer theory fails in explaining severe systematic deviations from the Furry statistics that is believed to be a governing statistical law. Such a deviated behaviour of high populated avalanches seems to be a consequence of a special pre-breakdown mechanism that is rather different from that known so far in discharge physics. This analysis tends towards formulating a modified theoretical concept supplementing the streamer theory by a new statistical view of pre-streamer states. The correctness of the concept is corroborated by a series of experiments

  19. Alpha- and gamma-detection by the avalanche detectors with metal-resistor-semiconductor structure

    International Nuclear Information System (INIS)

    Vetokhin, S.S.; Evtushenko, V.P.; Zalesskij, V.B.; Malyshev, S.A.; Chudakov, V.A.; Shunevich, S.A.

    1992-01-01

    Possibility to use silicon avalanche photodetectors with metal-resistor-semiconductor structure with 0.12 cm 2 photosensitive area as detectors of α-particles, as well as, photodetector of γ-quanta scintillation detector is shown. When detection of α-particles the energy resolution reaches 10%. R energy resolution for avalanche photodetector-CsI(Tl) scintillator system cooled up to - 60 deg C at 59 keV ( 241 Am) and 662 keV ( 137 Cs) energy of γ-quanta constitutes 60% and 80%, respectively. R minimal value in the conducted experiments is determined by the degree of irregularity of avalanche amplification along the photodetector area

  20. Lowering effect of radioactive irradiation on breakdown voltage and electron avalanche pulse characteristics

    International Nuclear Information System (INIS)

    Kawahashi, Akira; Nakano, Toru; Hosokawa, Tatsuzo; Miyoshi, Yosinori.

    1976-01-01

    In the time resolving measurement of the growing process and breakdown of electron avalanche in a gap of uniform electric field, the phenomenon that DC breakdown voltage slightly lowered was observed when β ray was irradiated as the initial electron source, as compared with unirradiated condition. Beta source used is 90 Sr- 90 Y of 2 mCi in radiative equilibrium. The experimental results and the examination are described in detail. In brief, the remarkable superposition of succeeding avalanche pulse over the preceeding avalanche pulse waveform was observed under the gap condition in which the breakdown voltage decreased in β-ray irradiation. Thus this superposition of avalanche pulses is considered as one of the causes of the breakdown voltage reduction. When β source is used as the initial electron source, the number of supplied initial electrons is very large as compared with unity, and at the same time, a great number of initial electrons can be supplied within the diffusion radius r of avalanche. Then the effect of initial electron number n 0 was considered by employing a diagram for breakdown scheme. The transition from Townsend type breakdown to streamer type breakdown occurs owing to increasing n 0 , and in that condition, the breakdown voltage lowers slightly. (Wakatsuki, Y)

  1. Volcanic avalanche fault zone with pseudotachylite and gouge in French Massif Central

    Science.gov (United States)

    Bernard, Karine; van Wyk de Vries, Benjamin

    2017-11-01

    Structures and textures with sedimentological variations at different scales of the lithofacies assemblage help us to constrain the basal kinematic transition from non-depositional to depositional conditions during volcanic avalanche emplacement. In the well-exposed impact-sheared contact along volcanic avalanche fault zone in the French Massif Central, we observe how the granular textures of the pseudotachylite and fault gouge have recorded the propagation of shock wave with granular oscillatory stress. Sequential events of basal aggradation along avalanche fault zone have been established related to fractal D-values, temperature pressure regime and oscillatory stress during slow wave velocity. A typical lithofacies assemblage with a reverse grading shows the pseudotachylite and fault gouge. A cataclastic gradient is characterised by the fractal D-values from 2.7 in jigsaw breccias with pseudotachylite partial melt, to 2.6 in the polymodal gouge. Shock, brecciation and comminution produce cataclastic shear bands in the pseudotachylite and quartz microstructures along the basal contact of the volcanic debris-avalanche deposit. Gouge microstructures show granular segregation, cataclasis with antithetic rotational Riedel shear, and an arching effect between the Riedel shear bands. X-ray microtomography provided 3D microfabrics along the clastic vein in the sandy-gouge. From the available statistical dataset, a few equations have been developed implicating the same cataclastic origin with a co-genetic evolution of lithofacies. An impact wave during primary shear propagation may contribute to produce hydroclastic matrix, pseudotachylite partial melt and proximal gouge thixotropy with v 50m/s and a T < 654 °C. The interseismic period with oscillatory stress is related to crushed clasts and basaltic melt around 800 °C, Riedel shear bands with granular segregation along the fault gouge. The secondary shock by matrix-rich avalanche (ΔP = 10GPa, T ≥ 1000-1500

  2. Development of high performance readout ASICs for silicon photomultipliers (SiPMs)

    International Nuclear Information System (INIS)

    Shen, Wei

    2012-01-01

    Silicon Photomultipliers (SiPMs) are novel kind of solid state photon detectors with extremely high photon detection resolution. They are composed of hundreds or thousands of avalanche photon diode pixels connected in parallel. These avalanche photon diodes are operated in Geiger Mode. SiPMs have the same magnitude of multiplication gain compared to the conventional photomultipliers (PMTs). Moreover, they have a lot of advantages such as compactness, relatively low bias voltage and magnetic field immunity etc. Special readout electronics are required to preserve the high performance of the detector. KLauS and STiC are two CMOS ASIC chips designed in particular for SiPMs. KLauS is used for SiPM charge readout applications. Since SiPMs have a much larger detector capacitance compared to other solid state photon detectors such as PIN diodes and APDs, a few special techniques are used inside the chip to make sure a descent signal to noise ratio for pixel charge signal can be obtained. STiC is a chip dedicated to SiPM time-of-flight applications. High bandwidth and low jitter design schemes are mandatory for such applications where time jitter less than tens of picoseconds is required. Design schemes and error analysis as well as measurement results are presented in the thesis.

  3. Prediction of picosecond voltage collapse and electromagnetic wave generation in gas avalanche switches

    International Nuclear Information System (INIS)

    Mayhall, D.J.; Yee, J.H.; Duong-Van, M.; Villa, F.

    1988-01-01

    A picosecond speed switch, the Gas Avalanche Switch (GAS), has been proposed for GeV linear accelerators. The medium is gas at high pressure (100 - 700 atm). An avalanche discharge is induced between pulse-charged high voltage electrodes by electron deposition from a fast laser pulse. Avalanche electrons move to the positive electrode, causing the applied voltage to collapse in picoseconds. A two-dimensional (2D) electromagnetic electron fluid computer code calculates the avalanche evolution and voltage collapse in air for an infinite parallel plate capacitor with a 0.1 mm spacing. Calculations are done for an accelerator switch geometry consisting of a 0.7 mm wide by 0.8 mm high, rectangular, high voltage center electrode (CE) between the grounded plates of a parallel plate line of 2 mm spacing. Several variations of CE elevation and initial electron deposition are investigated The 2D character of the outgoing TEM waves is shown

  4. Pin-photodiode array for the measurement of fan-beam energy and air kerma distributions of X-ray CT scanners.

    Science.gov (United States)

    Haba, Tomonobu; Koyama, Shuji; Aoyama, Takahiko; Kinomura, Yutaka; Ida, Yoshihiro; Kobayashi, Masanao; Kameyama, Hiroshi; Tsutsumi, Yoshinori

    2016-07-01

    Patient dose estimation in X-ray computed tomography (CT) is generally performed by Monte Carlo simulation of photon interactions within anthropomorphic or cylindrical phantoms. An accurate Monte Carlo simulation requires an understanding of the effects of the bow-tie filter equipped in a CT scanner, i.e. the change of X-ray energy and air kerma along the fan-beam arc of the CT scanner. To measure the effective energy and air kerma distributions, we devised a pin-photodiode array utilizing eight channels of X-ray sensors arranged at regular intervals along the fan-beam arc of the CT scanner. Each X-ray sensor consisted of two plate type of pin silicon photodiodes in tandem - front and rear photodiodes - and of a lead collimator, which only allowed X-rays to impinge vertically to the silicon surface of the photodiodes. The effective energy of the X-rays was calculated from the ratio of the output voltages of the photodiodes and the dose was calculated from the output voltage of the front photodiode using the energy and dose calibration curves respectively. The pin-photodiode array allowed the calculation of X-ray effective energies and relative doses, at eight points simultaneously along the fan-beam arc of a CT scanner during a single rotation of the scanner. The fan-beam energy and air kerma distributions of CT scanners can be effectively measured using this pin-photodiode array. Copyright © 2016 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

  5. Infrasound array criteria for automatic detection and front velocity estimation of snow avalanches: towards a real-time early-warning system

    Science.gov (United States)

    Marchetti, E.; Ripepe, M.; Ulivieri, G.; Kogelnig, A.

    2015-11-01

    Avalanche risk management is strongly related to the ability to identify and timely report the occurrence of snow avalanches. Infrasound has been applied to avalanche research and monitoring for the last 20 years but it never turned into an operational tool to identify clear signals related to avalanches. We present here a method based on the analysis of infrasound signals recorded by a small aperture array in Ischgl (Austria), which provides a significant improvement to overcome this limit. The method is based on array-derived wave parameters, such as back azimuth and apparent velocity. The method defines threshold criteria for automatic avalanche identification by considering avalanches as a moving source of infrasound. We validate the efficiency of the automatic infrasound detection with continuous observations with Doppler radar and we show how the velocity of a snow avalanche in any given path around the array can be efficiently derived. Our results indicate that a proper infrasound array analysis allows a robust, real-time, remote detection of snow avalanches that is able to provide the number and the time of occurrence of snow avalanches occurring all around the array, which represent key information for a proper validation of avalanche forecast models and risk management in a given area.

  6. HgCdTe e-avalanche photodiode detector arrays

    Directory of Open Access Journals (Sweden)

    Anand Singh

    2015-08-01

    Full Text Available Initial results on the MWIR e-APD detector arrays with 30 μm pitch fabricated on LPE grown compositionally graded p-HgCdTe epilayers are presented. High dynamic resistance times active area (R0A product 2 × 106 Ω-cm2, low dark current density 4 nA/cm2 and high gain 5500 at -8 V were achieved in the n+-υ-p+ HgCdTe e-APD at 80 K. LPE based HgCdTe e-APD development makes this technology amenable for adoption in the foundries established for the conventional HgCdTe photovoltaic detector arrays without any additional investment.

  7. High quantum efficiency annular backside silicon photodiodes for reflectance pulse oximetry in wearable wireless body sensors

    DEFF Research Database (Denmark)

    Duun, Sune Bro; Haahr, Rasmus Grønbek; Hansen, Ole

    2010-01-01

    The development of annular photodiodes for use in a reflectance pulse oximetry sensor is presented. Wearable and wireless body sensor systems for long-term monitoring require sensors that minimize power consumption. We have fabricated large area 2D ring-shaped silicon photodiodes optimized...

  8. Spatial redistribution of radiation in flip-chip photodiodes based on InAsSbP/InAs double heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Zakgeim, A. L. [Russian Academy of Sciences, Scientific and Technological Center for Microelectronics (Russian Federation); Il’inskaya, N. D.; Karandashev, S. A.; Lavrov, A. A., E-mail: ioffeled@mail.ru; Matveev, B. A.; Remennyy, M. A.; Stus’, N. M.; Usikova, A. A. [Russian Academy of Sciences, Ioffe Institute (Russian Federation); Cherniakov, A. E. [Russian Academy of Sciences, Scientific and Technological Center for Microelectronics (Russian Federation)

    2017-02-15

    The spatial distribution of equilibrium and nonequilibrium (including luminescent) IR (infrared) radiation in flip-chip photodiodes based on InAsSbP/InAs double heterostructures (λ{sub max} = 3.4 μm) is measured and analyzed; the structural features of the photodiodes, including the reflective properties of the ohmic contacts, are taken into account. Optical area enhancement due to multiple internal reflection in photodiodes with different geometric characteristics is estimated.

  9. Spatially Extended Avalanches in a Hysteretic Capillary Condensation System: Superfluid 4He in Nuclepore

    International Nuclear Information System (INIS)

    Lilly, M.P.; Wootters, A.H.; Hallock, R.B.

    1996-01-01

    Capacitive studies of hysteretic capillary condensation of superfluid 4 He in Nuclepore have shown that the initial draining of the pores occurs over a small range of the chemical potential with avalanches present as groups of pores drain. In the work reported here, the avalanches in this system are shown to be nonlocal events which involve pores distributed at low density across the entire sample. The nonlocal avalanche behavior is shown to be enabled by the presence of a superfluid film connection among the pores. copyright 1996 The American Physical Society

  10. Mirror position determination for the alignment of Cherenkov Telescopes

    Energy Technology Data Exchange (ETDEWEB)

    Adam, J. [TU Dortmund, Experimental Physics 5 Otto-Hahn-Str. 4, 44221 Dortmund (Germany); Ahnen, M.L. [ETH Zurich, Institute for Particle Physics Otto-Stern-Weg 5, 8093 Zurich (Switzerland); Baack, D. [TU Dortmund, Experimental Physics 5 Otto-Hahn-Str. 4, 44221 Dortmund (Germany); Balbo, M. [University of Geneva, ISDC Data Center for Astrophysics Chemin Ecogia 16, 1290 Versoix (Switzerland); Bergmann, M. [Universität Würzburg, Institute for Theoretical Physics and Astrophysics Emil-Fischer-Str. 31, 97074 Würzburg (Germany); Biland, A. [ETH Zurich, Institute for Particle Physics Otto-Stern-Weg 5, 8093 Zurich (Switzerland); Blank, M. [Universität Würzburg, Institute for Theoretical Physics and Astrophysics Emil-Fischer-Str. 31, 97074 Würzburg (Germany); Bretz, T. [ETH Zurich, Institute for Particle Physics Otto-Stern-Weg 5, 8093 Zurich (Switzerland); RWTH Aachen (Germany); Bruegge, K.A.; Buss, J. [TU Dortmund, Experimental Physics 5 Otto-Hahn-Str. 4, 44221 Dortmund (Germany); Dmytriiev, A. [University of Geneva, ISDC Data Center for Astrophysics Chemin Ecogia 16, 1290 Versoix (Switzerland); Domke, M. [TU Dortmund, Experimental Physics 5 Otto-Hahn-Str. 4, 44221 Dortmund (Germany); Dorner, D. [Universität Würzburg, Institute for Theoretical Physics and Astrophysics Emil-Fischer-Str. 31, 97074 Würzburg (Germany); FAU Erlangen (Germany); Einecke, S. [TU Dortmund, Experimental Physics 5 Otto-Hahn-Str. 4, 44221 Dortmund (Germany); Hempfling, C. [Universität Würzburg, Institute for Theoretical Physics and Astrophysics Emil-Fischer-Str. 31, 97074 Würzburg (Germany); and others

    2017-07-11

    Imaging Atmospheric Cherenkov Telescopes (IACTs) need imaging optics with large apertures to map the faint Cherenkov light emitted in extensive air showers onto their image sensors. Segmented reflectors fulfill these needs using mass produced and light weight mirror facets. However, as the overall image is the sum of the individual mirror facet images, alignment is important. Here we present a method to determine the mirror facet positions on a segmented reflector in a very direct way. Our method reconstructs the mirror facet positions from photographs and a laser distance meter measurement which goes from the center of the image sensor plane to the center of each mirror facet. We use our method to both align the mirror facet positions and to feed the measured positions into our IACT simulation. We demonstrate our implementation on the 4 m First Geiger-mode Avalanche Cherenkov Telescope (FACT).

  11. A new detector concept for silicon photomultipliers

    Energy Technology Data Exchange (ETDEWEB)

    Sadigov, A., E-mail: saazik@yandex.ru [National Nuclear Research Center, Baku (Azerbaijan); Ahmadov, F.; Ahmadov, G. [National Nuclear Research Center, Baku (Azerbaijan); Ariffin, A.; Khorev, S. [Zecotek Photonics Inc., Vancouver (Canada); Sadygov, Z. [National Nuclear Research Center, Baku (Azerbaijan); Joint Institute for Nuclear Research, Dubna (Russian Federation); Suleymanov, S. [National Nuclear Research Center, Baku (Azerbaijan); Zerrouk, F. [Zecotek Photonics Inc., Vancouver (Canada); Madatov, R. [Institute of Radiation Problems, Baku (Azerbaijan)

    2016-07-11

    A new design and principle of operation of silicon photomultipliers are presented. The new design comprises a semiconductor substrate and an array of independent micro-phototransistors formed on the substrate. Each micro-phototransistor comprises a photosensitive base operating in Geiger mode and an individual micro-emitter covering a small part of the base layer, thereby creating, together with this latter, a micro-transistor. Both micro-emitters and photosensitive base layers are connected with two respective independent metal grids via their individual micro-resistors. The total value of signal gain in the proposed silicon photomultiplier is a result of both the avalanche gain in the base layer and the corresponding gain in the micro-transistor. The main goals of the new design are: significantly lower both optical crosstalk and after-pulse effects at high signal amplification, improve speed of single photoelectron pulse formation, and significantly reduce the device capacitance.

  12. On the relativistic large-angle electron collision operator for runaway avalanches in plasmas

    Science.gov (United States)

    Embréus, O.; Stahl, A.; Fülöp, T.

    2018-02-01

    Large-angle Coulomb collisions lead to an avalanching generation of runaway electrons in a plasma. We present the first fully conservative large-angle collision operator, derived from the relativistic Boltzmann operator. The relation to previous models for large-angle collisions is investigated, and their validity assessed. We present a form of the generalized collision operator which is suitable for implementation in a numerical kinetic equation solver, and demonstrate the effect on the runaway-electron growth rate. Finally we consider the reverse avalanche effect, where runaways are slowed down by large-angle collisions, and show that the choice of operator is important if the electric field is close to the avalanche threshold.

  13. Reducing financial avalanches by random investments

    Science.gov (United States)

    Biondo, Alessio Emanuele; Pluchino, Alessandro; Rapisarda, Andrea; Helbing, Dirk

    2013-12-01

    Building on similarities between earthquakes and extreme financial events, we use a self-organized criticality-generating model to study herding and avalanche dynamics in financial markets. We consider a community of interacting investors, distributed in a small-world network, who bet on the bullish (increasing) or bearish (decreasing) behavior of the market which has been specified according to the S&P 500 historical time series. Remarkably, we find that the size of herding-related avalanches in the community can be strongly reduced by the presence of a relatively small percentage of traders, randomly distributed inside the network, who adopt a random investment strategy. Our findings suggest a promising strategy to limit the size of financial bubbles and crashes. We also obtain that the resulting wealth distribution of all traders corresponds to the well-known Pareto power law, while that of random traders is exponential. In other words, for technical traders, the risk of losses is much greater than the probability of gains compared to those of random traders.

  14. Radiated power measurement with AXUV photodiodes in EAST tokamak

    International Nuclear Information System (INIS)

    Duan Yanmin; Hu Liqun; Du Wei; Mao Songtao; Chen Kaiyun; Zhang Jizhong

    2013-01-01

    The fast bolometer diagnostic system for absolute radiated power measurement on EAST tokamak is introduced, which is based on the absolute extreme ultraviolet (AXUV) photodiodes. The relative calibration of AXUV detectors is carried out using X-ray tube and standard luminance source in order to evaluate the sensitivity degradation caused by cumulative radiation damage during experiments. The calibration result shows a 23% sensitivity decrease in the X-ray range for the detector suffering ∼27000 discharges, but the sensitivity for the visible light changes little. The radiated power measured by AXUV photodiodes is compared with that measured by resistive bolometer. The total radiated power in main plasma deduced from AXUV detector is lower a factor of 1∼4 than that deduced from resistive bolometer. Some typical measurement results are also shown in this article. (author)

  15. Avalanches in Mn12-Acetate: ``Magnetic Burning"

    Science.gov (United States)

    McHugh, Sean; Suzuki, Y.; Graybill, D.; Sarachik, M. P.; Avraham, N.; Myasoedov, Y.; Shtrikman, H.; Zeldov, E.; Bagai, R.; Chakov, N. E.; Christou, G.

    2006-03-01

    From local time-resolved measurements of fast reversal of the magnetization in single crystals of the molecular magnet Mn12-acetate, we have shown[1] that the magnetization avalanche spreads as a narrow interface that propagates through the crystal at a constant velocity roughly two orders of magnitude smaller than the speed of sound. This phenomenon is closely analogous to the propagation of a flame front (deflagration) through a flammable chemical substance. The propagation speed of the avalanche depends on the energy stored in each molecule, which can be controlled and tuned using an external magnetic field. We report studies of propagation speed with different external fields in Mn12-acetate. [1] Yoko Suzuki, M.P. Sarachik, E.M. Chudnovsky, S. McHugh, R. Gonzalez-Rubio, N. Avraham, Y. Myasoedov, H. Shtrikman, E. Zeldov, N.E. Chakov and G. Christou, Phys. Rev. Lett. 95, 147201 (2005).

  16. Using GIS and Google Earth for the creation of the Going-to-the-Sun Road Avalanche Atlas, Glacier National Park, Montana, USA

    Science.gov (United States)

    Peitzsch, Erich H.; Fagre, Daniel B.; Dundas, Mark

    2010-01-01

    Snow avalanche paths are key geomorphologic features in Glacier National Park, Montana, and an important component of mountain ecosystems: they are isolated within a larger ecosystem, they are continuously disturbed, and they contain unique physical characteristics (Malanson and Butler, 1984). Avalanches impact subalpine forest structure and function, as well as overall biodiversity (Bebi et al., 2009). Because avalanches are dynamic phenomena, avalanche path geometry and spatial extent depend upon climatic regimes. The USGS/GNP Avalanche Program formally began in 2003 as an avalanche forecasting program for the spring opening of the ever-popular Going-to-the-Sun Road (GTSR), which crosses through 37 identified avalanche paths. Avalanche safety and forecasting is a necessary part of the GTSR spring opening procedures. An avalanche atlas detailing topographic parameters and oblique photographs was completed for the GTSR corridor in response to a request from GNP personnel for planning and resource management. Using ArcMap 9.2 GIS software, polygons were created for every avalanche path affecting the GTSR using aerial imagery, field-based observations, and GPS measurements of sub-meter accuracy. Spatial attributes for each path were derived within the GIS. Resulting products include an avalanche atlas book for operational use, a geoPDF of the atlas, and a Google Earth flyover illustrating each path and associated photographs. The avalanche atlas aids park management in worker safety, infrastructure planning, and natural resource protection by identifying avalanche path patterns and location. The atlas was created for operational and planning purposes and is also used as a foundation for research such as avalanche ecology projects and avalanche path runout modeling.

  17. The development of structures in analogue and natural debris avalanches

    Science.gov (United States)

    Paguican, Engielle Mae; van Wyk de Vries, Benjamin; Mahar Francisco Lagmay, Alfredo; Grosse, Pablo

    2010-05-01

    All types of rockslide-debris avalanches present a plethora of internal structures that are also well observed on the surface. Many of these are seen as faults and folds that can be used to determine deformation history and kinematics. We present two sets of simple and well-constrained experiments of reduced basal friction laboratory rockslides, equivalent to a highly deformed simple shear layer, with plug-flow. These follow the original ramp-slide work of Shea and van Wyk de Vries (Geosphere, 2008). The experiments used a curved ramp where materials accelerate until reaching a gently-sloped depositional surface and a constantly inclined ramp with a more regular slope and longer slides. A detailed description of deposit structures, their sequential formation and morphology is then used to investigate the transport type and deformation chronology from slide initiation to runout stopping of avalanches. Results using a curved ramp show accumulation and thickening at where the slope decreases. The thickened mass then further remobilises and advances by secondary collapse of the mass. Such a stop-start process may be important in many mountainous avalanches where there are rapid changes in slope. The constantly inclined ramp shows shearing and extensional structures at the levees and a set of compression and extension structures in the middle. We noted that frontal accumulation during flow occurs as materials at the front move slower relative to those in the medial and proximal zones. This also leads to secondary frontal collapse, and helps to maintain a thicker mass that can flow further. Descriptions and analyses of these structures are then applied to the kinematics and dynamics of natural examples. We study the 2006 Guinsaugon Rockslide event in the Philippines and find that frontal accumulation and secondary avalanching had also occurred and were important in determining the distribution and runout of the mass. Frontal bulking and collapse may also have occurred at

  18. Ultra compact 45 GHz CMOS compatible Germanium waveguide photodiode with low dark current.

    Science.gov (United States)

    DeRose, Christopher T; Trotter, Douglas C; Zortman, William A; Starbuck, Andrew L; Fisher, Moz; Watts, Michael R; Davids, Paul S

    2011-12-05

    We present a compact 1.3 × 4 μm2 Germanium waveguide photodiode, integrated in a CMOS compatible silicon photonics process flow. This photodiode has a best-in-class 3 dB cutoff frequency of 45 GHz, responsivity of 0.8 A/W and dark current of 3 nA. The low intrinsic capacitance of this device may enable the elimination of transimpedance amplifiers in future optical data communication receivers, creating ultra low power consumption optical communications.

  19. A sensitive ultraviolet light photodiode based on graphene-on-zinc oxide Schottky junction

    Science.gov (United States)

    Zhang, Teng-Fei; Wu, Guo-An; Wang, Jiu-Zhen; Yu, Yong-Qiang; Zhang, Deng-Yue; Wang, Dan-Dan; Jiang, Jing-Bo; Wang, Jia-Mu; Luo, Lin-Bao

    2017-08-01

    In this study, we present a simple ultraviolet (UV) light photodiode by transferring a layer of graphene film on single-crystal ZnO substrate. The as-fabricated heterojunction exhibited typical rectifying behavior, with a Schottky barrier height of 0.623 eV. Further optoelectronic characterization revealed that the graphene-ZnO Schottky junction photodiode displayed obvious sensitivity to 365-nm light illumination with good reproducibility. The responsivity and photoconductive gain were estimated to be 3×104 A/W and 105, respectively, which were much higher than other ZnO nanostructure-based devices. In addition, it was found that the on/off ratio of the present device can be considerably improved from 2.09 to 12.1, when the device was passivated by a layer of AlOx film. These results suggest that the present simply structured graphene-ZnO UV photodiode may find potential application in future optoelectronic devices.

  20. Some n-p (Hg,Cd)Te photodiodes for 8-14 micrometer heterodyne applications

    Science.gov (United States)

    Shanley, J. F.; Flanagan, C. T.

    1980-01-01

    The results describing the dc and CO2 laser heterodyne characteristics of a three element photodiode array and single element and four element photodiode arrays are presented. The measured data shows that the n(+)-p configuration is capable of achieving bandwidths of 475 to 725 MHz and noise equivalent powers of 3.2 x 10 to the minus 20th power W/Hz at 77 K and 1.0 x 10 to the minus 19th power W/Hz at 145 K. The n(+)-n(-)-p photodiodes exhibited wide bandwidths (approximately 2.0 GHz) and fairly good effective heterodyne quantum efficiencies (approximately 13-30 percent at 2.0 GHz). Noise equivalent powers ranging from 1.44 x 10 to the minus 19th power W/Hz to 6.23 x 10 to the minus 20th power W/Hz were measured at 2.0 GHz.

  1. Photoresponse analysis of the CMOS photodiodes for CMOS x-ray image sensor

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Young Soo; Ha, Jang Ho; Kim, Han Soo; Yeo, Sun Mok [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2012-11-15

    Although in the short term CMOS active pixel sensors (APSs) cannot compete with the conventionally used charge coupled devices (CCDs) for high quality scientific imaging, recent development in CMOS APSs indicate that CMOS performance level of CCDs in several domains. CMOS APSs possess thereby a number of advantages such as simpler driving requirements and low power operation. CMOS image sensors can be processed in standard CMOS technologies and the potential of on-chip integration of analog and digital circuitry makes them more suitable for several vision systems where system cost is of importance. Moreover, CMOS imagers can directly benefit from on-going technological progress in the field of CMOS technologies. Due to these advantages, the CMOS APSs are currently being investigated actively for various applications such as star tracker, navigation camera and X-ray imaging etc. In most detection systems, it is thought that the sensor is most important, since this decides the signal and noise level. So, in CMOS APSs, the pixel is very important compared to other functional blocks. In order to predict the performance of such image sensor, a detailed understanding of the photocurrent generation in the photodiodes that comprise the CMOS APS is required. In this work, we developed the analytical model that can calculate the photocurrent generated in CMOS photodiode comprising CMOS APSs. The photocurrent calculations and photo response simulations with respect to the wavelength of the incident photon were performed using this model for four types of photodiodes that can be fabricated in standard CMOS process. n{sup +}/p{sup -}sub and n{sup +}/p{sup -}epi/p{sup -}sub photodiode show better performance compared to n{sup -}well/p{sup -}sub and n{sup -}well/p{sup -}epi/p{sup -}sub due to the wider depletion width. Comparing n{sup +}/p{sup -}sub and n{sup +}/p{sup -}epi/p{sup -}sub photodiode, n{sup +}/p{sup -}sub has higher photo-responsivity in longer wavelength because of

  2. Photoresponse analysis of the CMOS photodiodes for CMOS x-ray image sensor

    International Nuclear Information System (INIS)

    Kim, Young Soo; Ha, Jang Ho; Kim, Han Soo; Yeo, Sun Mok

    2012-01-01

    Although in the short term CMOS active pixel sensors (APSs) cannot compete with the conventionally used charge coupled devices (CCDs) for high quality scientific imaging, recent development in CMOS APSs indicate that CMOS performance level of CCDs in several domains. CMOS APSs possess thereby a number of advantages such as simpler driving requirements and low power operation. CMOS image sensors can be processed in standard CMOS technologies and the potential of on-chip integration of analog and digital circuitry makes them more suitable for several vision systems where system cost is of importance. Moreover, CMOS imagers can directly benefit from on-going technological progress in the field of CMOS technologies. Due to these advantages, the CMOS APSs are currently being investigated actively for various applications such as star tracker, navigation camera and X-ray imaging etc. In most detection systems, it is thought that the sensor is most important, since this decides the signal and noise level. So, in CMOS APSs, the pixel is very important compared to other functional blocks. In order to predict the performance of such image sensor, a detailed understanding of the photocurrent generation in the photodiodes that comprise the CMOS APS is required. In this work, we developed the analytical model that can calculate the photocurrent generated in CMOS photodiode comprising CMOS APSs. The photocurrent calculations and photo response simulations with respect to the wavelength of the incident photon were performed using this model for four types of photodiodes that can be fabricated in standard CMOS process. n + /p - sub and n + /p - epi/p - sub photodiode show better performance compared to n - well/p - sub and n - well/p - epi/p - sub due to the wider depletion width. Comparing n + /p - sub and n + /p - epi/p - sub photodiode, n + /p - sub has higher photo-responsivity in longer wavelength because of the higher electron diffusion current

  3. Multiwire proportional chamber and multistage avalanche chamber with low concentration photoionization gas

    International Nuclear Information System (INIS)

    Zhao Pingde; Xu Zhiqing; Tang Xiaowei

    1986-01-01

    The characteristics of multiwire proportional chamber and multistage avalanche chamber filled with argon and photoionization gas (C 2 H 5 ) 3 N were measured. The spatial resolution curves and output pulse height spectra were measured as well. Low concentration (C 2 H 5 ) 3 N can play an effective part in quenching. At very low concentration, the phenomena of avalanche transverse expansion was observed obviously

  4. Tunneling Current Probe for Noncontract Wafer-Level Photodiode Array Testing

    National Research Council Canada - National Science Library

    Verdun, Horacio

    1999-01-01

    The Tunneling Current Probe (TCP) is an automated picometer-sensitive proximity sensor and current measurement system which measures the current through a photodiode detector array element by establishing a tunneling current...

  5. The Vaigat Rock Avalanche Laboratory, west-central Greenland

    Science.gov (United States)

    Dunning, S.; Rosser, N. J.; Szczucinski, W.; Norman, E. C.; Benjamin, J.; Strzelecki, M.; Long, A. J.; Drewniak, M.

    2013-12-01

    Rock avalanches have unusually high mobility and pose both an immediate hazard, but also produce far-field impacts associated with dam breach, glacier collapse and where they run-out into water, tsunami. Such secondary hazards can often pose higher risks than the original landslide. The prediction of future threats posed by potential rock avalanches is heavily reliant upon understanding of the physics derived from an interpretation of deposits left by previous events, yet drawing comparisons between multiple events is normally challenging as interactions with complex mountainous terrain makes deposits from each event unique. As such numerical models and the interpretation of the underlying physics which govern landslide mobility is commonly case-specific and poorly suited to extrapolation beyond the single events the model is tuned to. Here we present a high-resolution LiDAR and hyperspectral dataset captured across a unique cluster of large rock avalanche source areas and deposits in the Vaigat straight, west central Greenland. Vaigat offers the unprecedented opportunity to model a sample of > 15 rock avalanches of various age sourced from an 80 km coastal escarpment. At Vaigat many of the key variables (topography, geology, post-glacial history) are held constant across all landslides providing the chance to investigate the variations in dynamics and emplacement style related to variable landslide volume, drop-heights, and thinning/spreading over relatively simple, unrestricted run-out zones both onto land and into water. Our data suggest that this region represents excellent preservation of landslide deposits, and hence is well suited to calibrate numerical models of run out dynamics. We use this data to aid the interpretation of deposit morphology, structure lithology and run-out characteristics in more complex settings. Uniquely, we are also able to calibrate our models using a far-field dataset of well-preserved tsunami run-up deposits, resulting from the 21

  6. Comparative study of various pixel photodiodes for digital radiography: Junction structure, corner shape and noble window opening

    Science.gov (United States)

    Kang, Dong-Uk; Cho, Minsik; Lee, Dae Hee; Yoo, Hyunjun; Kim, Myung Soo; Bae, Jun Hyung; Kim, Hyoungtaek; Kim, Jongyul; Kim, Hyunduk; Cho, Gyuseong

    2012-05-01

    Recently, large-size 3-transistors (3-Tr) active pixel complementary metal-oxide silicon (CMOS) image sensors have been being used for medium-size digital X-ray radiography, such as dental computed tomography (CT), mammography and nondestructive testing (NDT) for consumer products. We designed and fabricated 50 µm × 50 µm 3-Tr test pixels having a pixel photodiode with various structures and shapes by using the TSMC 0.25-m standard CMOS process to compare their optical characteristics. The pixel photodiode output was continuously sampled while a test pixel was continuously illuminated by using 550-nm light at a constant intensity. The measurement was repeated 300 times for each test pixel to obtain reliable results on the mean and the variance of the pixel output at each sampling time. The sampling rate was 50 kHz, and the reset period was 200 msec. To estimate the conversion gain, we used the mean-variance method. From the measured results, the n-well/p-substrate photodiode, among 3 photodiode structures available in a standard CMOS process, showed the best performance at a low illumination equivalent to the typical X-ray signal range. The quantum efficiencies of the n+/p-well, n-well/p-substrate, and n+/p-substrate photodiodes were 18.5%, 62.1%, and 51.5%, respectively. From a comparison of pixels with rounded and rectangular corners, we found that a rounded corner structure could reduce the dark current in large-size pixels. A pixel with four rounded corners showed a reduced dark current of about 200fA compared to a pixel with four rectangular corners in our pixel sample size. Photodiodes with round p-implant openings showed about 5% higher dark current, but about 34% higher sensitivities, than the conventional photodiodes.

  7. Comparative study of various pixel photodiodes for digital radiography: junction structure, corner shape and noble window opening

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Dong-Uk; Cho, Min-Sik; Lee, Dae-Hee; Yoo, Hyun-Jun; Kim, Myung-Soo; Bae, Jun-Hyung; Kim, Hyoung-Taek; Kim, Jong-Yul; Kim, Hyun-Duk; Cho, Gyu-Seong [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of)

    2012-05-15

    Recently, large-size 3-transistors (3-Tr) active pixel complementary metal-oxide silicon (CMOS) image sensors have been being used for medium-size digital X-ray radiography, such as dental computed tomography (CT), mammography and nondestructive testing (NDT) for consumer products. We designed and fabricated 50 μm x 50 μm 3-Tr test pixels having a pixel photodiode with various structures and shapes by using the TSMC 0.25-m standard CMOS process to compare their optical characteristics. The pixel photodiode output was continuously sampled while a test pixel was continuously illuminated by using 550-nm light at a constant intensity. The measurement was repeated 300 times for each test pixel to obtain reliable results on the mean and the variance of the pixel output at each sampling time. The sampling rate was 50 kHz, and the reset period was 200 msec. To estimate the conversion gain, we used the mean-variance method. From the measured results, the n-well/p-substrate photodiode, among 3 photodiode structures available in a standard CMOS process, showed the best performance at a low illumination equivalent to the typical X-ray signal range. The quantum efficiencies of the n+/p-well, n-well/p-substrate, and n+/p-substrate photodiodes were 18.5%, 62.1%, and 51.5%, respectively. From a comparison of pixels with rounded and rectangular corners, we found that a rounded corner structure could reduce the dark current in large-size pixels. A pixel with four rounded corners showed a reduced dark current of about 200 fA compared to a pixel with four rectangular corners in our pixel sample size. Photodiodes with round p-implant openings showed about 5% higher dark current, but about 34% higher sensitivities, than the conventional photodiodes.

  8. A method to harness global crowd-sourced data to understand travel behavior in avalanche terrain.

    Science.gov (United States)

    Hendrikx, J.; Johnson, J.

    2015-12-01

    To date, most studies of the human dimensions of decision making in avalanche terrain has focused on two areas - post-accident analysis using accident reports/interviews and, the development of tools as decision forcing aids. We present an alternate method using crowd-sourced citizen science, for understanding decision-making in avalanche terrain. Our project combines real-time GPS tracking via a smartphone application, with internet based surveys of winter backcountry users as a method to describe and quantify travel practices in concert with group decision-making dynamics, and demographic data of participants during excursions. Effectively, we use the recorded GPS track taken within the landscape as an expression of the decision making processes and terrain usage by the group. Preliminary data analysis shows that individual experience levels, gender, avalanche hazard, and group composition all influence the ways in which people travel in avalanche terrain. Our results provide the first analysis of coupled real-time GPS tracking of the crowd while moving in avalanche terrain combined with psychographic and demographic correlates. This research will lead to an improved understanding of real-time decision making in avalanche terrain. In this paper we will specifically focus on the presentation of the methods used to solicit, and then harness the crowd to obtain data in a unique and innovative application of citizen science where the movements within the terrain are the desired output data (Figure 1). Figure 1: Example GPS tracks sourced from backcountry winter users in the Teton Pass area (Wyoming), from the 2014-15 winter season, where tracks in red represent those recorded as self-assessed experts (as per our survey), and where tracks in blue represent those recorded as self-assessed intermediates. All tracks shown were obtained under similar avalanche conditions. Statistical analysis of terrain metrics showed that the experts used steeper terrain than the

  9. A 75 GHz silicon metal-semiconductor-metal Schottky photodiode

    International Nuclear Information System (INIS)

    Alexandrou, S.; Wang, C.; Hsiang, T.Y.; Liu, M.Y.; Chou, S.Y.

    1993-01-01

    The ultrafast characteristics of crystalline-silicon metal-semiconductor-metal (MSM) photodiodes with 300 nm finger width and spacing were measured with a subpicosecond electro-optic sampling system. Electrical responses with full width at half maximum as short as 5.5 and 11 ps, at corresponding 3 dB bandwidths of 75 and 38 GHz, were generated by violet and red photons, respectively. The difference is attributed to the photon penetration depth which is much larger than the diode finger spacing at red, but smaller at violet. Light-intensity dependence was also examined at different wavelengths, indicating a linear relation and a higher sensitivity in the violet. These results not only demonstrated the fastest silicon photodetector reported to date, but also pinpointed the dominant speed-limiting factor of silicon MSM photodiodes. A configuration is suggested to improve the speed of these detectors at long wavelengths

  10. Athermal avalanche in bilayer superconducting nanowire single-photon detectors

    Energy Technology Data Exchange (ETDEWEB)

    Verma, V. B., E-mail: verma@nist.gov; Lita, A. E.; Stevens, M. J.; Mirin, R. P.; Nam, S. W. [National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305 (United States)

    2016-03-28

    We demonstrate that two superconducting nanowires separated by a thin insulating barrier can undergo an avalanche process. In this process, Joule heating caused by a photodetection event in one nanowire and the associated production of athermal phonons which are transmitted through the barrier cause the transition of the adjacent nanowire from the superconducting to the normal state. We show that this process can be utilized in the fabrication of superconducting nanowire single photon detectors to improve the signal-to-noise ratio, reduce system jitter, maximize device area, and increase the external efficiency over a very broad range of wavelengths. Furthermore, the avalanche mechanism may provide a path towards a superconducting logic element based on athermal gating.

  11. A sensitive ultraviolet light photodiode based on graphene-on-zinc oxide Schottky junction

    Directory of Open Access Journals (Sweden)

    Zhang Teng-Fei

    2016-11-01

    Full Text Available In this study, we present a simple ultraviolet (UV light photodiode by transferring a layer of graphene film on single-crystal ZnO substrate. The as-fabricated heterojunction exhibited typical rectifying behavior, with a Schottky barrier height of 0.623 eV. Further optoelectronic characterization revealed that the graphene-ZnO Schottky junction photodiode displayed obvious sensitivity to 365-nm light illumination with good reproducibility. The responsivity and photoconductive gain were estimated to be 3×104 A/W and 105, respectively, which were much higher than other ZnO nanostructure-based devices. In addition, it was found that the on/off ratio of the present device can be considerably improved from 2.09 to 12.1, when the device was passivated by a layer of AlOx film. These results suggest that the present simply structured graphene-ZnO UV photodiode may find potential application in future optoelectronic devices.

  12. Compact multispectral photodiode arrays using micropatterned dichroic filters

    Science.gov (United States)

    Chandler, Eric V.; Fish, David E.

    2014-05-01

    The next generation of multispectral instruments requires significant improvements in both spectral band customization and portability to support the widespread deployment of application-specific optical sensors. The benefits of spectroscopy are well established for numerous applications including biomedical instrumentation, industrial sorting and sensing, chemical detection, and environmental monitoring. In this paper, spectroscopic (and by extension hyperspectral) and multispectral measurements are considered. The technology, tradeoffs, and application fits of each are evaluated. In the majority of applications, monitoring 4-8 targeted spectral bands of optimized wavelength and bandwidth provides the necessary spectral contrast and correlation. An innovative approach integrates precision spectral filters at the photodetector level to enable smaller sensors, simplify optical designs, and reduce device integration costs. This method supports user-defined spectral bands to create application-specific sensors in a small footprint with scalable cost efficiencies. A range of design configurations, filter options and combinations are presented together with typical applications ranging from basic multi-band detection to stringent multi-channel fluorescence measurement. An example implementation packages 8 narrowband silicon photodiodes into a 9x9mm ceramic LCC (leadless chip carrier) footprint. This package is designed for multispectral applications ranging from portable color monitors to purpose- built OEM industrial and scientific instruments. Use of an eight-channel multispectral photodiode array typically eliminates 10-20 components from a device bill-of-materials (BOM), streamlining the optical path and shrinking the footprint by 50% or more. A stepwise design approach for multispectral sensors is discussed - including spectral band definition, optical design tradeoffs and constraints, and device integration from prototype through scalable volume production

  13. Oscillatory regime of avalanche particle detectors

    International Nuclear Information System (INIS)

    Lukin, K.A.; Cerdeira, H.A.; Colavita, A.A.

    1995-06-01

    We describe the model of an avalanche high energy particle detector consisting of two pn-junctions, connected through an intrinsic semiconductor with a reverse biased voltage applied. We show that this detector is able to generate the oscillatory response on the single particle passage through the structure. The possibility of oscillations leading to chaotic behaviour is pointed out. (author). 15 refs, 7 figs

  14. Silicon photodiode with selective Zr/Si coating for extreme ultraviolet spectral range

    International Nuclear Information System (INIS)

    Aruev, P N; Barysheva, Mariya M; Ber, B Ya; Zabrodskaya, N V; Zabrodskii, V V; Lopatin, A Ya; Pestov, Alexey E; Petrenko, M V; Polkovnikov, V N; Salashchenko, Nikolai N; Sukhanov, V L; Chkhalo, Nikolai I

    2012-01-01

    The procedure of manufacturing silicon photodiodes with an integrated Zr/Si filter for extreme ultraviolet (EUV) spectral range is developed. A setup for measuring the sensitivity profile of detectors with spatial resolution better than 100 μm is fabricated. The optical properties of silicon photodiodes in the EUV and visible spectral ranges are investigated. Some characteristics of SPD-100UV diodes with Zr/Si coating and without it, as well as of AXUV-100 diodes, are compared. In all types of detectors a narrow region beyond the operating aperture is found to be sensitive to the visible light. (photodetectors)

  15. Electrical crosstalk in front-illuminated photodiode array with different guard ring designs for medical CT applications

    International Nuclear Information System (INIS)

    Ji Fan; Juntunen, Mikko; Hietanen, Iiro

    2009-01-01

    This paper presents electrical crosstalk studies on front-illuminated photodiode arrays for medical computed tomography (CT) applications. Crosstalk is an important factor to the system noise and image quality. The electrical crosstalk depends on silicon substrate properties and photodiode structures. The photodiode samples employed in this paper are planar processed on high-resistivity n-type silicon substrate, resulting in a p+/n-/n+ diode structure. Two types of guard ring structures are designed and applied to the same geometry of two-dimensional photodiode arrays. One structure is an n guard ring in the gap area between pixels, and the other structure is an additional p+ guard ring around each pixel together with the n guard ring. A 10 μm light spot with wavelength of 525 nm is used to scan across the surface of the photodiode array in the electrical crosstalk measurements. The electrical currents of two neighbor pixels are measured and the results are compared between two guard ring designs. The design with the p+ guard ring structure gives better electrical crosstalk suppression. Moreover, the measurement results show much smaller influence on surrounding pixels with the p+ guard ring structure in the case of disconnected pixel. Besides the electrical crosstalk, the light sensitivity within the gap area is also discussed between two guard ring designs.

  16. Time and positioning characteristics of the SQS mode

    International Nuclear Information System (INIS)

    Fraga, F.A.F. de; Ferreira Marques, R.; Policarpo, A.J.P.L.; Coimbra Univ.; Coimbra Univ.

    1989-01-01

    Previous results on the azimuthal localization of punctual interactions using the self-quenching streamer (SQS) mode, as given by the direction of the SQS avalanche, have shown a marked improvement in resolution when the current pulses are integrated for short times. In this work, data concerning the position resolution along the wire in the SQS mode for the argon-48% isobutane mixture, using a 55 Fe source, are presented. Essentially the same effect was detected: The FWHM, larger than 500 μm for the total signal duration, is reduced to about 300 μm for a 10 ns gate. This improvement in position resolution is practically independent of the anode voltage, all along the plateau. (orig.)

  17. Study of a PIN photodiode as an ionizing radiation detector for aerospace use

    International Nuclear Information System (INIS)

    Nogueira, S.F.L.; Claro, L.H.; Santos, J.A.; Junior, J.R.; Federico, C.A.

    2017-01-01

    This work aims to study the use of the COTS PIN photodiode with an active area of 7.5 mm 2 as an ionizing radiation detector. The tests were performed with a 60 Co source and with low activity radioisotopic sources of 60 Co, 152 Eu, 137 Cs and 241 Am. The results were obtained by analyzing the current response generated by the photodiodes as a function of an attenuated dose rate in silicon in the range of 0.55 to 11.54 Gy / h

  18. Smartphone applications for communicating avalanche risk information - a review of existing practices

    Science.gov (United States)

    Charrière, M. K. M.; Bogaard, T. A.

    2015-11-01

    Every year, in all mountainous regions, people are victims of avalanches. One way to decrease those losses is believed to be informing about danger levels. The paper presents a study on current practices in the development of smartphones applications that are dedicated to avalanche risk communication. The analysis based on semi-structured interviews with developers of smartphone apps highlights the context of their development, how choices of content and visualization were made as well as how their effectiveness is evaluated. It appears that although the communicators agree on the message to disseminate, its representation triggers debate. Moreover, only simple evaluation processes are conducted but there is a clear awareness that further scientific efforts are needed to analyze the effectiveness of the smartphone apps. Finally, the current or planned possibility for non-experts users to report feedback on the snow and avalanches conditions open the doors to a transition of these apps from one-way communication tools to two-ways communication platforms. This paper also indicates the remaining challenges that avalanche risk communication is facing, although it is disputably the most advanced and standardized practice compared to other natural hazards. Therefore, this research is of interest for the entire field of natural hazards related risk communication.

  19. Parameters of an avalanche of runaway electrons in air under atmospheric pressure

    Science.gov (United States)

    Oreshkin, E. V.

    2018-01-01

    The features of runaway-electron avalanches developing in air under atmospheric pressures are investigated in the framework of a three-dimensional numerical simulation. The simulation results indicate that an avalanche of this type can be characterized, besides the time and length of its exponential growth, by the propagation velocity and by the average kinetic energy of the runaway electrons. It is shown that these parameters obey the similarity laws applied to gas discharges.

  20. Highly Sensitive Switchable Heterojunction Photodiode Based on Epitaxial Bi2FeCrO6 Multiferroic Thin Films.

    Science.gov (United States)

    Huang, Wei; Chakrabartty, Joyprokash; Harnagea, Catalin; Gedamu, Dawit; Ka, Ibrahima; Chaker, Mohamed; Rosei, Federico; Nechache, Riad

    2018-04-18

    Perovskite multiferroic oxides are promising materials for the realization of sensitive and switchable photodiodes because of their favorable band gap (heterojunction was fabricated by pulsed laser deposition. The heterojunction photodiode exhibits a large ideality factor ( n = ∼5.0) and a response time as fast as 68 ms, thanks to the effective charge carrier transport and collection at the BFCO/SRO interface. The diode can switch direction when the electric polarization is reversed by an external voltage pulse. The time-resolved photoluminescence decay of the device measured at ∼500 nm demonstrates an ultrafast charge transfer (lifetime = ∼6.4 ns) in BFCO/SRO heteroepitaxial structures. The estimated responsivity value at 500 nm and zero bias is 0.38 mA W -1 , which is so far the highest reported for any FE thin film photodiode. Our work highlights the huge potential for using multiferroic oxides to fabricate highly sensitive and switchable photodiodes.

  1. Universal Critical Dynamics in High Resolution Neuronal Avalanche Data

    Science.gov (United States)

    Friedman, Nir; Ito, Shinya; Brinkman, Braden A. W.; Shimono, Masanori; DeVille, R. E. Lee; Dahmen, Karin A.; Beggs, John M.; Butler, Thomas C.

    2012-05-01

    The tasks of neural computation are remarkably diverse. To function optimally, neuronal networks have been hypothesized to operate near a nonequilibrium critical point. However, experimental evidence for critical dynamics has been inconclusive. Here, we show that the dynamics of cultured cortical networks are critical. We analyze neuronal network data collected at the individual neuron level using the framework of nonequilibrium phase transitions. Among the most striking predictions confirmed is that the mean temporal profiles of avalanches of widely varying durations are quantitatively described by a single universal scaling function. We also show that the data have three additional features predicted by critical phenomena: approximate power law distributions of avalanche sizes and durations, samples in subcritical and supercritical phases, and scaling laws between anomalous exponents.

  2. An InP/Si heterojunction photodiode fabricated by self-aligned corrugated epitaxial lateral overgrowth

    International Nuclear Information System (INIS)

    Sun, Y. T.; Omanakuttan, G.; Lourdudoss, S.

    2015-01-01

    An n-InP/p-Si heterojunction photodiode fabricated by corrugated epitaxial lateral overgrowth (CELOG) method is presented. N-InP/p-Si heterojunction has been achieved from a suitable pattern containing circular shaped openings in a triangular lattice on the InP seed layer on p-Si substrate and subsequent CELOG of completely coalesced n-InP. To avoid current path through the seed layer in the final photodiode, semi-insulating InP:Fe was grown with adequate thickness prior to n-InP growth in a low pressure hydride vapor phase epitaxy reactor. The n-InP/p-Si heterointerface was analyzed by scanning electron microscopy and Raman spectroscopy. Room temperature cross-sectional photoluminescence (PL) mapping illustrates the defect reduction effect in InP grown on Si by CELOG method. The InP PL intensity measured above the InP/Si heterojunction is comparable to that of InP grown on a native planar substrate indicating low interface defect density of CELOG InP despite of 8% lattice mismatch with Si. The processed n-InP/p-Si heterojunction photodiodes show diode characteristics from the current-voltage (I-V) measurements with a dark current density of 0.324 mA/cm 2 at a reverse voltage of −1 V. Under the illumination of AM1.5 conditions, the InP/Si heterojunction photodiode exhibited photovoltaic effect with an open circuit voltage of 180 mV, a short circuit current density of 1.89 mA/cm 2 , an external quantum efficiency of 4.3%, and an internal quantum efficiency of 6.4%. This demonstration of epitaxially grown InP/Si heterojunction photodiode will open the door for low cost and high efficiency solar cells and photonic integration of III-Vs on silicon

  3. Avalanche transistor pulser for fast-gated operation of micro-channel plate image-intensifiers

    International Nuclear Information System (INIS)

    Lundy, A.; Parker, J.R.; Lunsford, J.S.; Martin, A.D.

    1977-01-01

    Transistors operated in the avalanche mode are employed to generate a 1000 volt 10 to 30 nsec wide pulse with less than 4 nsec rise and fall times. This pulse is resistively attenuated to approximately equal to 270 volts and drives the image intensifier tube which is a load of approximately equal to 200 pf. To reduce stray inductance and capacitance, transistor chips were assembled on a thick-film hybrid substrate. Circuit parameters, operating conditions, and coupling to the microchannel plate image-intensifier (MCPI 2 ) tube are described. To provide dc operating voltages and control of transient voltages on the MCPI 2 tube a resistance-capacitance network has been developed which (a) places the MCPI 2 output phosphor at ground, (b) provides programmable gains in ''f-stop'' steps, and (c) minimizes voltage transients on the MCPI 2 tube

  4. Radiation tests of photodiodes for the ATLAS SCT and PIXEL opto- links

    CERN Document Server

    Hou, L S; Lee, S C; Su, D S; Teng, P K

    2005-01-01

    In previous research, epitaxial Si PIN photodiodes produced by Centronic which will be used in the ATLAS semiconductor tracker have been irradiated with 1 MeV neutrons and 24 GeV protons with fluences up to an equivalent of $10^{15}$ 1 MeV neutrons (1,2) . In this work 30 MeV proton beams were used to irradiate Centronic and Truelight epitaxial Si PIN diodes with accumulated fluences of up to 2.1 multiplied by $10^{14}$-30 MeV p $cm^{-2}$, an equivalent of 5.7 multiplied by $10^{14} cm^{-2}$ 1 MeV neutrons, to reach the pixel radiation environment. The responsivity was measured with different levels of fluence in order to study the responsivity behaviour of two different types of photodiodes. The responsivity behaviour of these two photodiodes was similar: a linear degradation at large fluences, greater than $10^{14}$ 30 MeV p $cm^{-2}$, but with different slopes. The response of the Centronic PIN diode showed a degradation to 73% after a proton fluence of $10^{13}$ p $cm^{-2}$ of 30 MeV and a linear degradat...

  5. Frequency and amplitude modulation of ultra-compact terahertz quantum cascade lasers using an integrated avalanche diode oscillator.

    Science.gov (United States)

    Castellano, Fabrizio; Li, Lianhe; Linfield, Edmund H; Davies, A Giles; Vitiello, Miriam S

    2016-03-15

    Mode-locked comb sources operating at optical frequencies underpin applications ranging from spectroscopy and ultrafast physics, through to absolute frequency measurements and atomic clocks. Extending their operation into the terahertz frequency range would greatly benefit from the availability of compact semiconductor-based sources. However, the development of any compact mode-locked THz laser, which itself is inherently a frequency comb, has yet to be achieved without the use of an external stimulus. High-power, electrically pumped quantum cascade lasers (QCLs) have recently emerged as a promising solution, owing to their octave spanning bandwidths, the ability to achieve group-velocity dispersion compensation and the possibility of obtaining active mode-locking. Here, we propose an unprecedented compact architecture to induce both frequency and amplitude self-modulation in a THz QCL. By engineering a microwave avalanche oscillator into the laser cavity, which provides a 10 GHz self-modulation of the bias current and output power, we demonstrate multimode laser emission centered around 3 THz, with distinct multiple sidebands. The resulting microwave amplitude and frequency self-modulation of THz QCLs opens up intriguing perspectives, for engineering integrated self-mode-locked THz lasers, with impact in fields such as nano- and ultrafast photonics and optical metrology.

  6. Surface passivation of GaInAsSb photodiodes with thioacetamide

    Energy Technology Data Exchange (ETDEWEB)

    Salesse, A.; Joullie, A.; Chevrier, F.; Cuminal, Y.; Ferblantier, G.; Christol, P. [Institut d' Electronique du Sud (IES-CEM2), UMR CNRS 5507, Case 067, Universite Montpellier 2, 34 095 Montpellier Cedex 05 (France); Calas, P. [UMR CNRS 5073 CHIMIE, Case 017, Universite Montpellier 2, 34 095 Montpellier Cedex 05 (France); Nieto, J. [Instituto de Investigacion en Comunicacion Optica (IICO), Universidad Autonoma de San Luis Potosi, Alvaro Obregon 64, San Luis Potosi (Mexico)

    2007-04-15

    AlGaAsSb/GaInAsSb heterojunction mesa photodiodes having 2.2 {mu}m cutoff wavelength, grown by MBE on (p) GaSb substrates, have been passivated using thioacetamide CH{sub 4}CSNH{sub 2} and ammonium sulphide (NH{sub 4}){sub 2}S. Superior characteristics were obtained from devices processed with thioacetamide in acid medium (pH=2.4). At room temperature the surface leakage currents were suppressed, and the photodiodes showed R{sub 0}A product as high as 16 {omega}cm{sup 2} and detectivity D{sup *}(2 {mu}m,0 V){proportional_to}10{sup 10} cmHz{sup 1/2}W{sup -1}. A model explaining sulfuration mechanisms with thioacetamide and (NH{sub 4}){sub 2}S is proposed. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  7. Responses of the multi-photodiode readout

    International Nuclear Information System (INIS)

    Tamai, K.

    2000-01-01

    The responses for a signal in various configurations of photodiodes (PDs) and preamplifiers are analyzed by Laplace transformation. The electronic noise in the configuration is derived using the Fourier transformation. The responses and noise are obtained by an analogical extension of the impedance from a single-PD configuration to the multi-PD configuration; however, the noise is not so simple when connected in series. Using the results, we evaluate the energy resolution of the configurations. A series PD connection realizes a better resolution than a parallel connection in the fast shaping

  8. A low-noise transimpedance amplifier for the detection of "Violin-Mode" resonances in advanced Laser Interferometer Gravitational wave Observatory suspensions

    Science.gov (United States)

    Lockerbie, N. A.; Tokmakov, K. V.

    2014-11-01

    This paper describes the design and performance of an extremely low-noise differential transimpedance amplifier, which takes its two inputs from separate photodiodes. The amplifier was planned to serve as the front-end electronics for a highly sensitive shadow-displacement sensing system, aimed at detecting very low-level "Violin-Mode" (VM) oscillations in 0.4 mm diameter by 600 mm long fused-silica suspension fibres. Four such highly tensioned fibres support the 40 kg test-masses/mirrors of the Advanced Laser Interferometer Gravitational wave Observatory interferometers. This novel design of amplifier incorporates features which prevent "noise-gain peaking" arising from large area photodiode (and cable) capacitances, and which also usefully separate the DC and AC photocurrents coming from the photodiodes. In consequence, the differential amplifier was able to generate straightforwardly two DC outputs, one per photodiode, as well as a single high-gain output for monitoring the VM oscillations—this output being derived from the difference of the photodiodes' two, naturally anti-phase, AC photocurrents. Following a displacement calibration, the amplifier's final VM signal output was found to have an AC displacement responsivity at 500 Hz of (9.43 ± 1.20) MV(rms) m-1(rms), and, therefore, a shot-noise limited sensitivity to such AC shadow- (i.e., fibre-) displacements of (69 ± 13) picometres/√Hz at this frequency, over a measuring span of ±0.1 mm.

  9. A low-noise transimpedance amplifier for the detection of "Violin-Mode" resonances in Advanced Laser Interferometer Gravitational wave Observatory suspensions.

    Science.gov (United States)

    Lockerbie, N A; Tokmakov, K V

    2014-11-01

    This paper describes the design and performance of an extremely low-noise differential transimpedance amplifier, which takes its two inputs from separate photodiodes. The amplifier was planned to serve as the front-end electronics for a highly sensitive shadow-displacement sensing system, aimed at detecting very low-level "Violin-Mode" (VM) oscillations in 0.4 mm diameter by 600 mm long fused-silica suspension fibres. Four such highly tensioned fibres support the 40 kg test-masses/mirrors of the Advanced Laser Interferometer Gravitational wave Observatory interferometers. This novel design of amplifier incorporates features which prevent "noise-gain peaking" arising from large area photodiode (and cable) capacitances, and which also usefully separate the DC and AC photocurrents coming from the photodiodes. In consequence, the differential amplifier was able to generate straightforwardly two DC outputs, one per photodiode, as well as a single high-gain output for monitoring the VM oscillations-this output being derived from the difference of the photodiodes' two, naturally anti-phase, AC photocurrents. Following a displacement calibration, the amplifier's final VM signal output was found to have an AC displacement responsivity at 500 Hz of (9.43 ± 1.20) MV(rms) m(-1)(rms), and, therefore, a shot-noise limited sensitivity to such AC shadow- (i.e., fibre-) displacements of (69 ± 13) picometres/√Hz at this frequency, over a measuring span of ±0.1 mm.

  10. Positron camera with high-density avalanche chambers

    International Nuclear Information System (INIS)

    Manfrass, D.; Enghardt, W.; Fromm, W.D.; Wohlfarth, D.; Hennig, K.

    1988-01-01

    The results of an extensive investigation of the properties of high-density avalanche chambers (HIDAC) are presented. This study has been performed in order to optimize the layout of HIDAC detectors, since they are intended to be applied as position sensitive detectors for annihilation radiation in a positron emission tomograph being under construction. (author)

  11. AX-PET: A novel PET concept with G-APD readout

    CERN Document Server

    Heller, M; Casella, C; Chesi, E; De Leo, R; Dissertori, G; Fanti, V; Gillam, J E; Joram, C; Lustermann, W; Nappi, E; Oliver, J F; Pauss, F; Rafecas, M; Rudge, A; Ruotsalainen, U; Schinzel, D; Schneider, T; Seguinot, J; Solevi, P; Stapnes, S; Tuna, U; Weilhammer, P

    2012-01-01

    The AX-PET collaboration has developed a novel concept for high resolution PET imaging to overcome some of the performance limitations of classical PET cameras, in particular the compromise between spatial resolution and sensitivity introduced by the parallax error. The detector consists of an arrangement of long LYSO scintillating crystals axially oriented around the field of view together with arrays of wave length shifter strips orthogonal to the crystals. This matrix allows a precise 3D measurement of the photon interaction point. This is valid both for photoelectric absorption at 511 key and for Compton scattering down to deposited energies of about 100 keV. Crystals and WLS strips are individually read out using Geiger-mode Avalanche Photo Diodes (G-APDs). The sensitivity of such a detector can be adjusted by changing the number of layers and the resolution is defined by the crystal and strip dimensions. Two AX-PET modules were built and fully characterized in dedicated test set-ups at CERN, with point-...

  12. FACT. Normalized and asynchronous mirror alignment for Cherenkov telescopes

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, Sebastian Achim [ETH Zurich (Switzerland); Buss, Jens [TU Dortmund (Germany)

    2016-07-01

    Imaging Atmospheric Cherenkov Telescopes (IACTs) need fast and large imaging optics to map the faint Cherenkov light emitted in cosmic ray air showers onto their image sensors. Segmented reflectors are inexpensive, lightweight and offer good image quality. However, alignment of the mirror facets remains a challenge. A good alignment is crucial in IACT observations to separate gamma rays from hadronic cosmic rays. We present a star tracking alignment method which is not restricted to clear nights. It normalizes the mirror facet reflections to be independent of the reference star or the cloud coverage. It records asynchronously of the telescope drive which makes the method easy to integrate in existing telescopes. It can be combined with remote facet actuation, but it does not need one to work. Furthermore, it can reconstruct all individual mirror facet point spread functions. We present the method and alignment results on the First Geiger-mode Photo Diode Avalanche Cherenkov Telescope (FACT) on the Canary Island of La Palma, Spain.

  13. Tests of gas sampling electromagnetic shower calorimeter

    International Nuclear Information System (INIS)

    Barbaro-Galtieri, A.; Carithers, W.; Day, C.; Johnson, K.J.; Wenzel, W.A.; Videau, H.

    1983-01-01

    An electromagnetic shower gas-sampling calorimeter has been tested in both Geiger and proportional discharge modes for incident electron energies in the range 0.125-16 GeV. The 0.2 radiation length-thick layers were lead-fiberglass laminates with cathode strips normal to the sense wires. The 5x10 mm 2 Geiger cells were formed with uniformly spaced nylon fibers perpendicular to the wires. Proportional mode measurements were carried out in the pressure range 1-10 atm. A Monte Carlo simulation is in good agreement with measured shower characteristics and has been used to predict the behavior for oblique of incidence and for various Geiger cell dimensions. (orig.)

  14. Developing an Experimental Simulation Method for Rock Avalanches: Fragmentation Behavior of Brittle Analogue Material

    Science.gov (United States)

    Thordén Haug, Øystein; Rosenau, Matthias; Leever, Karen; Oncken, Onno

    2013-04-01

    Gravitational mass movement on earth and other planets show a scale dependent behavior, of which the physics is not fully understood. In particular, the runout distance for small to medium sized landslides (volume dynamics control small and large landslides/rock avalanches. Several mechanisms have been proposed to explain this scale dependent behavior, but no consensus has been reached. Experimental simulations of rock avalanches usually involve transport of loose granular material down a chute. Though such granular avalanche models provide important insights into avalanche dynamics, they imply that the material fully disintegrate instantaneously. Observations from nature, however, suggests that a transition from solid to "liquid" occurs over some finite distance downhill, critically controlling the mobility and energy budget of the avalanche. Few experimental studies simulated more realistically the material failing during sliding and those were realized in a labscale centrifuge, where the range of volumes/scales is limited. To develop a new modeling technique to study the scale dependent runout behavior of rock avalanches, we designed, tested and verified several brittle materials allowing fragmentation to occur under normal gravity conditions. According to the model similarity theory, the analogue material must behave dynamically similar to the rocks in natural rock avalanches. Ideally, the material should therefore deform in a brittle manner with limited elastic and ductile strains up to a certain critical stress, beyond which the material breaks and deforms irreversibly. According to scaling relations derived from dimensional analysis and for a model-to-prototype length ratio of 1/1000, the appropriate yield strength for an analogue material is in the order of 10 kPa, friction coefficient around 0.8 and stiffness in the order of MPa. We used different sand (garnet, quartz) in combination with different matrix materials (sugar, salt, starch, plaster) to cement

  15. A new solver for granular avalanche simulation: Indoor experiment verification and field scale case study

    Science.gov (United States)

    Wang, XiaoLiang; Li, JiaChun

    2017-12-01

    A new solver based on the high-resolution scheme with novel treatments of source terms and interface capture for the Savage-Hutter model is developed to simulate granular avalanche flows. The capability to simulate flow spread and deposit processes is verified through indoor experiments of a two-dimensional granular avalanche. Parameter studies show that reduction in bed friction enhances runout efficiency, and that lower earth pressure restraints enlarge the deposit spread. The April 9, 2000, Yigong avalanche in Tibet, China, is simulated as a case study by this new solver. The predicted results, including evolution process, deposit spread, and hazard impacts, generally agree with site observations. It is concluded that the new solver for the Savage-Hutter equation provides a comprehensive software platform for granular avalanche simulation at both experimental and field scales. In particular, the solver can be a valuable tool for providing necessary information for hazard forecasts, disaster mitigation, and countermeasure decisions in mountainous areas.

  16. Swedish skiers knowledge, experience and attitudes towards off-piste skiing and avalanches

    OpenAIRE

    Mårtensson, Stefan; Wikberg, Per-Olov; Palmgren, Petter

    2013-01-01

    The winter of 2012/2013 was the most accident-prone season in the Swedish avalanche history with a total of seven dead Swedes. In April 2013 the Swedish Mountain Safety Council initiated a web-based survey aimed towards Swedish skiers. The aim was to identify the target group's knowledge, experience and attitudes towards off-piste skiing and avalanches. Respondents were asked to answer a total of 28 questions. 1047 Swedish off-piste skiers answered, and we analysed them in more detail. The Sw...

  17. Simulations of Si-PIN photodiode based detectors for underground explosives enhanced by ammonium nitrate

    Science.gov (United States)

    Yücel, Mete; Bayrak, Ahmet; Yücel, Esra Barlas; Ozben, Cenap S.

    2018-02-01

    Massive Ammonium Nitrate (NH4-NO3) based explosives buried underground are commonly used in terror attacks. These explosives can be detected using neutron scattering method with some limitations. Simulations are very useful tools for designing a possible detection system for these kind of explosives. Geant4 simulations were used for generating neutrons at 14 MeV energy and tracking them through the scattering off the explosive embedded in soil. Si-PIN photodiodes were used as detector elements in the design for their low costs and simplicity for signal readout electronics. Various neutron-charge particle converters were applied on to the surface of the photodiodes to increase the detection efficiency. Si-PIN photodiodes coated with 6LiF provided the best result for a certain energy interval. Energy depositions in silicon detector from all secondary particles generated including photons were taken into account to generate a realistic background. Humidity of soil, one of the most important parameter for limiting the detection, was also studied.

  18. Analysis of the snow-atmosphere energy balance during wet-snow instabilities and implications for avalanche prediction

    Directory of Open Access Journals (Sweden)

    C. Mitterer

    2013-02-01

    Full Text Available Wet-snow avalanches are notoriously difficult to predict; their formation mechanism is poorly understood since in situ measurements representing the thermal and mechanical evolution are difficult to perform. Instead, air temperature is commonly used as a predictor variable for days with high wet-snow avalanche danger – often with limited success. As melt water is a major driver of wet-snow instability and snow melt depends on the energy input into the snow cover, we computed the energy balance for predicting periods with high wet-snow avalanche activity. The energy balance was partly measured and partly modelled for virtual slopes at different elevations for the aspects south and north using the 1-D snow cover model SNOWPACK. We used measured meteorological variables and computed energy balance and its components to compare wet-snow avalanche days to non-avalanche days for four consecutive winter seasons in the surroundings of Davos, Switzerland. Air temperature, the net shortwave radiation and the energy input integrated over 3 or 5 days showed best results in discriminating event from non-event days. Multivariate statistics, however, revealed that for better predicting avalanche days, information on the cold content of the snowpack is necessary. Wet-snow avalanche activity was closely related to periods when large parts of the snowpack reached an isothermal state (0 °C and energy input exceeded a maximum value of 200 kJ m−2 in one day, or the 3-day sum of positive energy input was larger than 1.2 MJ m−2. Prediction accuracy with measured meteorological variables was as good as with computed energy balance parameters, but simulated energy balance variables accounted better for different aspects, slopes and elevations than meteorological data.

  19. Recalculation of an artificially released avalanche with SAMOS and validation with measurements from a pulsed Doppler radar

    Directory of Open Access Journals (Sweden)

    R. Sailer

    2002-01-01

    Full Text Available A joint experiment was carried out on 10 February 1999 by the Swiss Federal Institute for Snow and Avalanche Research (SFISAR and the Austrian Institute for Avalanche and Torrent Research (AIATR, of the Federal Office and Re-search Centre for Forests, BFW to measure forces and velocities at the full scale experimental site CRÊTA BESSE in VALLÉE DE LA SIONNE, Canton du Valais, Switzerland. A huge avalanche could be released artificially, which permitted extensive investigations (dynamic measurements, im-provement of measurement systems, simulation model verification, design of protective measures, etc.. The results of the velocity measurements from the dual frequency pulsed Doppler avalanche radar of the AIATR and the recalculation with the numerical simulation model SAMOS are explained in this paper.

  20. Plasma simulation of electron avalanche in a linear thyratron

    International Nuclear Information System (INIS)

    Kushner, M.J.

    1985-01-01

    Thyratrons typically operate at sufficiently small PD (pressure x electrode separation) that holdoff is obtained by operating on the near side of the Paschen curve, and by shielding the slot in the control grid so there is no straight line path for electrons to reach the anode from the cathode. Electron avalanche is initiated by pulsing the control grid to a high voltage. Upon collapse of voltage in the cathode-control grid space, the discharge is sustained by penetration of potential through the control grid slot into the cathode-control grid region. To better understand the electron avalanche process in multi-grid and slotted structures such as thyratrons, a plasma simulation code has been constructed. This effort is in support of a companion program in which a linear thyratron is being electrically and spectroscopically characterized