WorldWideScience

Sample records for area avalanche photodiodes

  1. Uniformity Measurements Across the Area of the CMS ECAL Avalanche Photodiodes

    CERN Document Server

    Godinovic, Nikola; Soric, Ivica; Antunovic, Zeljko; Dzelalija, Mile; Deiters, Konrad; Ingram, Quentin; Renker, Dieter; Musienko, Yuri

    2004-01-01

    The photodetectors which will read out the scintillation light generated in the lead tungstate crystals in the barrel part of the CMS electromagnetic calorimeter are avalanche photodiodes (APDs). Scanning the APD's active area with a collimated light spot, the spatial uniformity of their quantum efficiency and gain has been measured at four different operating gains. Details of the APD surface structure are examined by scanning with a fine light spot. These details help to explain the difference between the bias voltage for a given gain when the full APD area is illuminated and when only the central part is illuminated.

  2. Gallium-based avalanche photodiode optical crosstalk

    Science.gov (United States)

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

    2006-11-01

    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.

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

    International Nuclear Information System (INIS)

    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

  4. Performance of a Large Area Avalanche Photodiode in a Liquid Xenon Ionization and Scintillation Chamber

    CERN Document Server

    Ni, K; Day, D; Giboni, K L; Lopes, J A M; Majewski, P; Yamashita, M

    2005-01-01

    Scintillation light produced in liquid xenon (LXe) by alpha particles, electrons and gamma-rays was detected with a large area avalanche photodiode (LAAPD) immersed in the liquid. The alpha scintillation yield was measured as a function of applied electric field. We estimate the quantum efficiency of the LAAPD to be 45%. The best energy resolution from the light measurement at zero electric field is 7.5%(sigma) for 976 keV internal conversion electrons from Bi-207 and 2.6%(sigma) for 5.5 MeV alpha particles from Am-241. The detector used for these measurements was also operated as a gridded ionization chamber to measure the charge yield. We confirm that using a LAAPD in LXe does not introduce impurities which inhibit the drifting of free electrons.

  5. Silicon Geiger mode avalanche photodiodes

    Institute of Scientific and Technical Information of China (English)

    M. Mazzillo; S. Billotta; G. Bonanno; A. Campisi; L. Cosentino; P. Finocchiaro; F. Musumeci; S.Privitera; S. Tudisco; G. Condorelli; D. Sanfilippo; G. Fallica; E. Sciacca; S. Aurite; S. Lombardo; E. Rlmini; M. Belluso

    2007-01-01

    In this letter we present the results regarding the electrical and optical characterization of Geiger mode silicon avalanche photodiodes (GMAP) fabricated by silicon standard planar technology. Low dark count rates, negligible afterpulsing effects,good timing resolution and high quantum detection efficiency in all the visible range have been measured. The very good electro-optical performances of our photodiodes make them attractive for the fabrication of arrays with a large number of GMAP to be used both in the commercial and the scientific fields, as telecommunications and nuclear medical imaging.

  6. Integrated avalanche photodiode arrays

    Energy Technology Data Exchange (ETDEWEB)

    Harmon, Eric S.

    2015-07-07

    The present disclosure includes devices for detecting photons, including avalanche photon detectors, arrays of such detectors, and circuits including such arrays. In some aspects, the detectors and arrays include a virtual beveled edge mesa structure surrounded by resistive material damaged by ion implantation and having side wall profiles that taper inwardly towards the top of the mesa structures, or towards the direction from which the ion implantation occurred. Other aspects are directed to masking and multiple implantation and/or annealing steps. Furthermore, methods for fabricating and using such devices, circuits and arrays are disclosed.

  7. Response of large area avalanche photodiodes to low energy x rays

    Energy Technology Data Exchange (ETDEWEB)

    Gentile, T. R. [Stop 8461, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Bales, M. [University of Michigan, Ann Arbor, Michigan 48104 (United States); Arp, U. [Stop 8410, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Dong, B. [Sotera Defense Solutions, Inc., Brookhaven National Laboratory, Upton, New York 11973 (United States); Farrell, R. [RMD Inc., Watertown, Massachusetts 02472 (United States)

    2012-05-15

    For an experiment to study neutron radiative beta-decay, we operated large area avalanche photodiodes (APDs) near liquid nitrogen temperature to detect x rays with energies between 0.2 keV and 20 keV. Whereas there are numerous reports of x ray spectrometry using APDs at energies above 1 keV, operation near liquid nitrogen temperature allowed us to reach a nominal threshold of 0.1 keV. However, due to the short penetration depth of x rays below 1 keV, the pulse height spectrum of the APD become complex. We studied the response using monochromatic x ray beams and employed phenomenological fits of the pulse height spectrum to model the measurement of a continuum spectrum from a synchrotron. In addition, the measured pulse height spectrum was modelled using a profile for the variation in efficiency of collection of photoelectrons with depth into the APD. The best results are obtained with the collection efficiency model.

  8. Energy resolution and light yield non-proportionality of ZnSe Te scintillator studied by large area avalanche photodiodes and photomultipliers

    CERN Document Server

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

    2002-01-01

    The ZnSe : Te scintillator has been studied by means of a photomultiplier with an extended bialkali photocathode, a large area avalanche photodiode (LAAPD) and a PIN photodiode. The light output was determined to be 28 300+-1700 photons/MeV. Results indicate good proportionality for light output versus gamma-ray energy. Measurements of the 662 keV gamma-ray energy spectrum recorded using a LAAPD resulted in an energy resolution of 5.4+-0.3%. Based on these results, an intrinsic energy resolution of 3.3+-0.7% has been calculated.

  9. 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.

  10. Readout of a LaCl sub 3 (Ce sup 3 sup +) scintillation crystal with a large area avalanche photodiode

    CERN Document Server

    Allier, C P; Dorenbos, P; Hollander, R W; Eijk, C W E; Kraemer, K W; Güdel, H U

    2002-01-01

    A high-resolution gamma-ray detector consisting of an 8 mm diameter and 5 mm thick LaCl sub 3 (Ce sup 3 sup +) scintillation crystal coupled to a 16 mm diameter APD from Advanced Photonix Inc is presented. The energy resolution R obtained at 662 keV is about 3.7% (full-width at half maximum). The low intrinsic resolution of about 2%, the high light yield of the crystal (46 000+-5000 photons per MeV) and the high quantum efficiency of the avalanche photodiode make this gamma-ray detector an excellent choice for applications were a high energy resolution is required.

  11. A high-speed avalanche photodiode

    International Nuclear Information System (INIS)

    High-speed avalanche photodiodes are widely used in optical communication systems. Nowadays, separate absorption charge and multiplication structure is widely adopted. In this article, a structure with higher speed than separate absorption charge and multiplication structure is reported. Besides the traditional absorption layer, charge layer and multiplication layer, this structure introduces an additional charge layer and transit layer and thus can be referred to as separate absorption, charge, multiplication, charge and transit structure. The introduction of the new charge layer and transit layer brings additional freedom in device structure design. The benefit of this structure is that the carrier transit time and device capacitance can be reduced independently, thus the 3 dB bandwidth could be improved by more than 50% in contrast to the separate absorption charge and multiplication structure with the same size. (semiconductor devices)

  12. Avalanche photodiodes for the CMS detector

    CERN Document Server

    Deiters, K; Ingram, Q; Nicol, S; Musienko, I; Patel, B; Renker, D; Reucroft, S; Rusack, R W; Sakhelashvili, T M; Singovsky, A V; Swain, J D; Vikas, P

    2000-01-01

    The CERN LHC experiment CMS has selected for the readout of the barrel crystal calorimeter a 5*5 mm/sup 2/ avalanche photodiode (APD) manufactured by Hamamatsu Photonics. In the detector we will equip each crystal with two APDs for a total of 122400 diodes. As the calorimeter will be almost completely inaccessible during the life of the detector, the assurance that they will survive with a high probability in the intense radiation field is an essential part of the of the APD qualification process. In this paper the properties of the APD selected will be described, as well as the procedures we have developed to assure their radiation hardness and reliability. (2 refs).

  13. SiC Avalanche Photodiodes and Arrays Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Aymont Technology, Inc. (Aymont) will demonstrate the feasibility of SiC p-i-n avalanche photodiodes (APD) arrays. Aymont will demonstrate 4 x 4 arrays of 2 mm2...

  14. Investigation of a photon counting avalanche photodiode from Hamamatsu photonics

    Science.gov (United States)

    Britvitch, I.; Musienko, Y.; Renker, D.

    2006-11-01

    Multi-cell avalanche photodiodes (APDs) operating in Geiger mode have been shown to be a very promising alternative to photomultiplier tubes for the detection of single photons at room temperature. Like a photomultiplier they have high gain and a fast rise time and they are insensitive to pickup. Beyond it they operate in high magnetic fields, are compact and need a relatively low bias voltage. It is expected that the MOS production technique makes them cheap. Recently PSI and Hamamatsu Photonics worked together for the development of a radiation-hard APD for CMS ECAL and had very good success. The development continued based on a similar design for a photon counting multielement Geiger-mode APD with an area of 1×1 mm 2. The properties of this device have been measured and will be reported.

  15. Investigation of a photon counting avalanche photodiode from Hamamatsu photonics

    Energy Technology Data Exchange (ETDEWEB)

    Britvitch, I. [ETH Zuerich (Switzerland); Musienko, Y. [Northeastern University, Boston (United States); Renker, D. [Paul Scherrer Institute, Villigen PSI, 5232 Villigen (Switzerland)]. E-mail: dieter.renker@psi.ch

    2006-11-01

    Multi-cell avalanche photodiodes (APDs) operating in Geiger mode have been shown to be a very promising alternative to photomultiplier tubes for the detection of single photons at room temperature. Like a photomultiplier they have high gain and a fast rise time and they are insensitive to pickup. Beyond it they operate in high magnetic fields, are compact and need a relatively low bias voltage. It is expected that the MOS production technique makes them cheap. Recently PSI and Hamamatsu Photonics worked together for the development of a radiation-hard APD for CMS ECAL and had very good success. The development continued based on a similar design for a photon counting multielement Geiger-mode APD with an area of 1x1 mm{sup 2}. The properties of this device have been measured and will be reported.

  16. Properties of the avalanche photodiodes for the CMS electromagnetic calorimeter

    CERN Document Server

    Deiters, K; Musienko, Yu V; Nicol, S; Patel, P; Renker, D; Reucroft, S; Rusack, R W; Sakhelashvili, T M; Swain, J D; Vikas, P

    2000-01-01

    The electromagnetic calorimeter of the CMS experiment at CERN's Large Hadron Collider will use 122400 avalanche photodiodes from Hamamatsu Photonics. The design of this APD type is the result of a long R&D program performed by Hamamatsu photonics and the CMS Collaboration. The APD parameters including the behavior under irradiation are discussed in view of our application. (4 refs).

  17. Performance of new Micro-pixel Avalanche Photodiodes from Zecotek Photonics

    Energy Technology Data Exchange (ETDEWEB)

    Sadygov, Z. [Institute of Physics, Javid Ave. 33, AZ 1143 Baku (Azerbaijan); Zecotek Photonics Inc., Vancouver, BC V6T 1Z3 (Canada); Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation)], E-mail: zsadygov@physics.ab.az; Zerrouk, A.F.; Ariffin, A.; Khorev, S.; Sasam, J. [Zecotek Photonics Inc., Vancouver, BC V6T 1Z3 (Canada); Zhezher, V.; Anphimov, N. [Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation); Dovlatov, A.; Musaev, M.; Muxtarov, R.; Safarov, N. [Institute of Physics, Javid Ave. 33, AZ 1143 Baku (Azerbaijan)

    2009-10-21

    Two new types of Micro-pixel Avalanche Photodiodes (MAPD) with sensitive area 3x3 mm{sup 2} and pixel densities of 15 000 and 40 000/mm{sup 2}, respectively, were designed and produced by Zecotek Photonics, Inc. Design and operation principles of these devices are described in this work. Measurement results of basic parameters are given as well.

  18. Novel radiation detectors based on multi pixels avalanche photodiodes: their status and perspectives of application

    International Nuclear Information System (INIS)

    Full text: Different versions of silicon avalanche photodiodes (APD), as well as new multi pixel avalanche photodiodes (MAPD) have been discussed widely during the last decade as an advanced photon counter for various applications. The sensitive area of a MAPD contains a matrix of independent micro-pixels with individual passive elements, which are created on a common silicon wafer. The individual passive elements provide local suppression of the avalanche process and discharge each micro-pixel to a common conducting or metal electrode. The advanced properties of a MAPD are connected with a local negative feedback (LNF) effect, which result in a local self-suppression of the avalanche gain due to individual passive elements with necessary resistivity and capacitance and, consequently, significantly reduces the influence of crystal non-uniformities on the characteristics of the avalanche multiplication process. The LNF effect is achieved by forming a specific matrix in the multilayer silicon structure which ensures a localisation of the avalanche processes and limits them in frames of independent micro-regions of 3-50 m in size, depending of the MAPD design. Thus, the micro-pixel structure in a MAPD results in a unique combination of high signal amplification and uniform avalanche multiplication over the entire sensitive area of the device. Each pixel has a sandwich like structure like a metal-resistive layer-semiconductor (MRS). This device is made in a very simple technology and it may demonstrate very good parameters in the red and near infrared regions of spectrum.

  19. Signal and Noise Properties of Position-Sensitive Avalanche Photodiodes

    OpenAIRE

    Yang, Yongfeng; Wu, Yibao; Farrell, Richard; Dokhale, Purushottam A.; Shah, Kanai S.; Cherry, Simon R.

    2011-01-01

    After many years of development, position-sensitive avalanche photodiodes (PSAPDs) are now being incorporated into a range of scintillation detector systems, including those used in high-resolution small-animal PET and PET/MR scanners. In this work, the signal, noise, signal-to-noise ratio (SNR), flood histogram and timing resolution were measured for lutetium oxyorthosilicate (LSO) scintillator arrays coupled to PSAPDs ranging in size from 10–20 mm, and the optimum bias voltage and working t...

  20. Simulation of neutron radiation effects in silicon avalanche photodiodes

    OpenAIRE

    Osborne, Mark David

    2000-01-01

    This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University. A new one-dimensional device simulation package developed for the simulation of neutron radiatiol! effects in silicon avalanche photodiodes is described. The software uses a finite difference technique to solve the time-independent semiconductor equations across a user specified structure. Impact ionisation and illumination are included, allowing accurate simulation with minimal assumptions a...

  1. Numerical simulation of neutron radiation effects in avalanche photodiodes

    OpenAIRE

    Osborne, M.; Hobson, PR; Watts, SJ

    2000-01-01

    A new one-dimensional (1-D) device model developed for the simulation of neutron radiation effects in silicon avalanche photodiodes is described. The model uses a finite difference technique to solve the time-independent semiconductor equations across a user specified structure. The model includes impact ionization and illumination allowing accurate simulation with minimal assumptions. The effect of neutron radiation damage is incorporated via the introduction of deep acceptor levels subject ...

  2. A New Positioning Algorithm for Position-Sensitive Avalanche Photodiodes

    OpenAIRE

    Zhang, Jin; Olcott, Peter D.; Levin, Craig S

    2007-01-01

    We are using a novel position sensitive avalanche photodiode (PSAPD) for the construction of a high resolution positron emission tomography (PET) camera. Up to now most researchers working with PSAPDs have been using an Anger-like positioning algorithm involving the four corner readout signals of the PSAPD. This algorithm yields a significant non-linear spatial “pin-cushion” distortion in raw crystal positioning histograms. In this paper, we report an improved positioning algorithm, which com...

  3. Investigation of avalanche photodiodes radiation hardness for baryonic matter studies

    International Nuclear Information System (INIS)

    Modern avalanche photodiodes (APDs) with high gain are good device candidates for light readout from detectors applied in relativistic heavy-ion collision experiments. The results of the investigations of the APDs properties from Zecotek, Ketek, and Hamamatsu manufacturers after irradiation using secondary neutrons from U120M cyclotron facility at NPI of ASCR in Rez are presented. The results of the investigations can be used for the design of the detectors for the experiments at NICA and FAIR

  4. Radiation hard avalanche photodiodes for the CMS detector

    CERN Document Server

    Antunovic, Z; Deiters, K; Godinovic, N; Ingram, Q; Kuznetsov, A; Musienko, Y; Puljak, I; Renker, D; Reucroft, S; Rusack, R; Sakhelashvili, T M; Singovsky, A V; Soric, I; Swain, J

    2005-01-01

    The avalanche photodiodes, developed by Hamamatsu Photonics in collaboration with CMS, which are to be used to read out the lead tungstate crystals in the barrel part of the CMS electromagnetic calorimeter, are described. The procedures taken to ensure their long-term reliability in the radiation environment expected in CMS are outlined, as well as the studies made to verify the very high reliability required.

  5. Radiation Hard Avalanche Photo-Diodes for the CMS detector

    CERN Document Server

    Antunovic, Z; Deiters, K; Godinovic, N; Ingram, Q; Kuznetsov, A; Musienko, Y; Puljak, I; Reucroft, S; Rusack, R W; Sakhelashvili, T M; Singovsky, A V; Soric, I; Swain, J D

    2003-01-01

    The avalanche photo-diodes, developed by Hamamatsu Photonics in collaboration with CMS, which are to be used to read out the lead tungstate crystals in the barrel part of the CMS electromagnetic calorimeter, are described. The procedures taken to ensure their long term reliability in the radiation environment expected in CMS are outlined, as well as the studies made to verify the very high reliability required.

  6. Investigation of avalanche photodiodes radiation hardness for baryonic matter studies

    CERN Document Server

    Kushpil, V; Ladygin, V P; Kugler, A; Kushpil, S; Svoboda, O; Tlustý, P

    2015-01-01

    Modern avalanche photodiodes (APDs) with high gain are good device candidates for light readout from detectors applied in relativistic heavy ion collisions experiments. The results of the investigations of the APDs properties from Zecotek, Ketek and Hamamatsu manufacturers after irradiation using secondary neutrons from cyclotron facility U120M at NPI of ASCR in \\v{R}e\\v{z} are presented. The results of the investigations can be used for the design of the detectors for the experiments at NICA and FAIR.

  7. Model of single-electron performance of micropixel avalanche photodiodes

    CERN Document Server

    Sadygov, Z; Akhmedov, G; Akhmedov, F; Khorev, S; Mukhtarov, R; Sadigov, A; Sidelev, A; Titov, A; Zerrouk, F; Zhezher, V

    2014-01-01

    An approximate iterative model of avalanche process in a pixel of micropixel avalanche photodiode initiated by a single photoelectron is presented. The model describes development of the avalanche process in time, taking into account change of electric field within the depleted region caused by internal discharge and external recharge currents. Conclusions obtained as a result of modelling are compared with experimental data. Simulations show that typical durations of the front and rear edges of the discharge current have the same magnitude of less than 50 ps. The front of the external recharge current has the same duration, however duration of the rear edge depends on value of the quenching micro-resistor. It was found that effective capacitance of the pixel calculated as the slope of linear dependence of the pulse charge on bias voltage exceeds its real capacitance by a factor of two.

  8. Radiation hard avalanche photodiodes for CMS ECAL

    CERN Document Server

    Kuznetsov, A; Britvitch, A; Deiters, K; Egeland, R; Gilbert, B; Godinovic, N; Ingram, Q; Lester, E; Musienko, Y; Puljak, I; Renker, D; Reucroft, S; Rusack, R W; Sakhelashvili, T M; Singovsky, A V; Soric, I; Swain, J D

    2003-01-01

    The photo detectors of the CMS electromagnetic calorimeter have to operate in a rather hostile environment, in a strong magnetic field of 4T and under unprecedented radiation levels. Avalanche Photo Diodes (APDs) have been chosen to detect the scintillation light of the 62,000 lead tungstate crystals in the barrel part of the calorimeter. After a 6 year long R&D work Hamamatsu Photonics produces APDs with a structure that is basically radiation hard. Only a few percent of the delivered APDs are weak due to defects at the surface caused by dust particles in the production process. Since a reliability of 99.9% is required, a method to detect weak APDs before they are built into the detector had to be developed. The described screening method is a combination of **6**0Co irradiations and annealing under bias of all APDs and irradiations with hadrons on a sampling basis.

  9. On possibilities of application of Miller formula for determination of parameters of Micropixel Avalanche Photodiodes

    CERN Document Server

    Sadygov, Z; Akhmedov, G; Akhmedov, F; Mukhtarov, R; Sadygov, A; Titov, A; Zhezher, V

    2014-01-01

    Miller formula modified to take into account voltage drop on serial resistor of an avalanche photodiode is considered. It is proven by experimental data that modified Miller formula can describe operation of both regular and micropixel avalanche photodiodes with good enough precision. It is shown that operation parameters of the devices can be determined using a linear extrapolation of the voltage-current curve for both regular avalanche photodiode and the one operating in Geiger mode.

  10. Characterization of midwave infrared InSb avalanche photodiode

    Science.gov (United States)

    Abautret, J.; Perez, J. P.; Evirgen, A.; Rothman, J.; Cordat, A.; Christol, P.

    2015-06-01

    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/cm2 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.

  11. Breakdown voltage in thin III-V avalanche photodiodes

    Science.gov (United States)

    Saleh, Mohammad A.; Hayat, Majeed M.; Kwon, Oh-Hyun; Holmes, Archie L.; Campbell, Joe C.; Saleh, Bahaa E. A.; Teich, Malvin C.

    2001-12-01

    The dead-space multiplication theory of Hayat and Saleh [J. Lightwave Technol. 10, 1415 (1992)], in conjunction with the multiplication-width-independent ionization-coefficient model developed by Saleh et al. [IEEE Trans. Electron Devices 47, 625 (2000)], are shown to accurately predict breakdown voltages for thin avalanche photodiodes of GaAs, InP, In0.52Al0.48As, and Al0.2Ga0.8As, over a broad range of device widths. The breakdown voltage is determined from the analytical expression for the impulse-response-function decay rate.

  12. Correcting for accidental correlations in saturated avalanche photodiodes

    CERN Document Server

    Grieve, James A; Tang, Zhongkan; Ling, Alexander

    2015-01-01

    In this paper we present a high-level numerical model for estimating rates of accidental correlations between a pair of passively quenched Geiger mode avalanche photodiodes operating in the saturated regime. By considering the recovery time of both the diodes and the detection circuit we introduce the concept of an "effective duty cycle" and show that it may be estimated by numeric simulation. The impact of effective duty cycle on the observed accidental rate is examined and we demonstrate that the updated model leads to an improved correction factor in actual experiments. This will improve the signal-to-noise ratio in applications depending on correlation measurements.

  13. Double Screening Tests of the CMS ECAL Avalanche Photodiodes

    CERN Document Server

    Deiters, Konrad; Renker, Dieter; Sakhelashvili, Tariel; Britvitch, Ilia; Kuznetsov, Andrey; Musienko, Yuri; Singovsky, Alexander

    2005-01-01

    Specially developed avalanche photo-diodes (APDs) will be used to measure the light from the 61,200 lead tungstate crystals in the barrel part of the CMS electromagnetic calorimeter. To ensure the reliability over the lifetime of the detector, every APD is screened by irradiation and burn-in before it is accepted for CMS. As part of the establishment of the screening procedure and to determine its effectiveness, a large number of APDs were screened twice. The results of these tests suggest that the required reliability will be achieved.

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

    International Nuclear Information System (INIS)

    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

  15. Design and characterization of avalanche photodiodes in submicron CMOS technologies

    Science.gov (United States)

    Pancheri, L.; Bendib, T.; Dalla Betta, G.-F.; Stoppa, D.

    2014-03-01

    The fabrication of Avalanche Photodiodes (APDs) in CMOS processes can be exploited in several application domains, including telecommunications, time-resolved optical detection and scintillation detection. CMOS integration allows the realization of systems with a high degree of parallelization which are competitive with hybrid solutions in terms of cost and complexity. In this work, we present a linear-mode APD fabricated in a 0.15μm process, and report its gain and noise characterization. The experimental observations can be accurately predicted using Hayat dead-space noise model. Device simulations based on dead-space model are then used to discuss the current status and the perspectives for the integration of high-performance low-noise devices in standard CMOS processes.

  16. Correcting for accidental correlations in saturated avalanche photodiodes.

    Science.gov (United States)

    Grieve, J A; Chandrasekara, R; Tang, Z; Cheng, C; Ling, A

    2016-02-22

    In this paper we present a general method for estimating rates of accidental coincidence between a pair of single photon detectors operated within their saturation regimes. By folding the effects of recovery time of both detectors and the detection circuit into an "effective duty cycle" we are able to accomodate complex recovery behaviour at high event rates. As an example, we provide a detailed high-level model for the behaviour of passively quenched avalanche photodiodes, and demonstrate effective background subtraction at rates commonly associated with detector saturation. We show that by post-processing using the updated model, we observe an improvement in polarization correlation visibility from 88.7% to 96.9% in our experimental dataset. This technique will be useful in improving the signal-to-noise ratio in applications which depend on coincidence measurements, especially in situations where rapid changes in flux may cause detector saturation. PMID:26907016

  17. 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.

  18. Systematic afterpulsing-estimation algorithms for gated avalanche photodiodes

    CERN Document Server

    Wiechers, Carlos; Muñiz-Sánchez, Oscar R; Yépiz, Pablo Daniel; Arredondo-Santos, Alejandro; Hirsch, Jorge G; U'Ren, Alfred B

    2016-01-01

    We present a method designed to efficiently extract optical signals from InGaAs avalanche photodiodes (APDs) operated in gated mode. In particular, our method permits an estimation of the fraction of counts which actually results from the signal being measured, as opposed to being produced by noise mechanisms, specifically by afterpulsing. Our method in principle allows the use of InGaAs APDs at high detection efficiencies, with the full operation bandwidth, either with or without resorting to the application of a dead time. As we show below, our method can be used in configurations where afterpulsing exceeds the genuine signal by orders of magnitude, even near saturation. The algorithms which we have developed are suitable to be used either in real-time processing of raw detection probabilities or in post-processing applications, after a calibration step has been performed. The algorithms which we propose here can complement technologies designed for the reduction of afterpulsing.

  19. 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.

  20. GaN-Based, Low-Voltage Avalanche Photodiodes for Robust and Compact UV Imagers Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This Phase I SBIR program is directed toward the development of a novel low-voltage (~10V) AlGaN-based multi-quantum well (MQW) avalanche photodiode (APD) on...

  1. 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.

  2. Investigation of the avalanche photodiodes for the CMS electromagnetic calorimeter operated at high gain

    CERN Document Server

    Deiters, K; Godinovic, N; Ingram, Q; Longo, E; Montecchi, M; Musienko, Yu V; Nicol, S; Patel, B; Renker, D; Reucroft, S; Rusack, R W; Sakhelashvili, T M; Singovsky, A V; Soric, I; Swain, J D; Vikas, P

    2001-01-01

    Avalanche photodiodes (APD) with improved characteristics were developed by Hamamatsu Photonics for the electromagnetic calorimeter of the CMS experiment. This report presents measurements of the latest generation of APDs, which are capable to operate at high gains (~2000). (5 refs).

  3. Single Photon Sensitive HgCdTe Avalanche Photodiode Detector (APD) Project

    Data.gov (United States)

    National Aeronautics and Space Administration — A linear mode HgCdT electron-initiated avalanche photodiode (EAPD) capable of 1570nm photon detection efficiency (PDE) at >10 MHz will be developed. The Phase I...

  4. Advanced active quenching circuits for single-photon avalanche photodiodes

    Science.gov (United States)

    Stipčević, M.; Christensen, B. G.; Kwiat, P. G.; Gauthier, D. J.

    2016-05-01

    Commercial photon-counting modules, often based on actively quenched solid-state avalanche photodiode sensors, are used in wide variety of applications. Manufacturers characterize their detectors by specifying a small set of parameters, such as detection efficiency, dead time, dark counts rate, afterpulsing probability and single photon arrival time resolution (jitter), however they usually do not specify the conditions under which these parameters are constant or present a sufficient description. In this work, we present an in-depth analysis of the active quenching process and identify intrinsic limitations and engineering challenges. Based on that, we investigate the range of validity of the typical parameters used by two commercial detectors. We identify an additional set of imperfections that must be specified in order to sufficiently characterize the behavior of single-photon counting detectors in realistic applications. The additional imperfections include rate-dependence of the dead time, jitter, detection delay shift, and "twilighting." Also, the temporal distribution of afterpulsing and various artifacts of the electronics are important. We find that these additional non-ideal behaviors can lead to unexpected effects or strong deterioration of the system's performance. Specifically, we discuss implications of these new findings in a few applications in which single-photon detectors play a major role: the security of a quantum cryptographic protocol, the quality of single-photon-based random number generators and a few other applications. Finally, we describe an example of an optimized avalanche quenching circuit for a high-rate quantum key distribution system based on time-bin entangled photons.

  5. A New Positioning Algorithm for Position-Sensitive Avalanche Photodiodes.

    Science.gov (United States)

    Zhang, Jin; Olcott, Peter D; Levin, Craig S

    2007-06-01

    We are using a novel position sensitive avalanche photodiode (PSAPD) for the construction of a high resolution positron emission tomography (PET) camera. Up to now most researchers working with PSAPDs have been using an Anger-like positioning algorithm involving the four corner readout signals of the PSAPD. This algorithm yields a significant non-linear spatial "pin-cushion" distortion in raw crystal positioning histograms. In this paper, we report an improved positioning algorithm, which combines two diagonal corner signals of the PSAPD followed by a 45° rotation to determine the X or Y position of the interaction. We present flood positioning histogram data generated with the old and new positioning algorithms using a 3 × 4 array of 2 × 2 × 3 mm(3) and a 3 × 8 array of 1 × 1 × 3 mm(3) of LSO crystals coupled to 8 × 8 mm(2) PSAPDs. This new algorithm significantly reduces the pin-cushion distortion in raw flood histogram image. PMID:24307743

  6. Interaction of Avalanche Photodiodes (APDs Devices With Thermal Irradiation Environments

    Directory of Open Access Journals (Sweden)

    Ahmed Nabih Zaki Rashed

    2012-04-01

    Full Text Available This paper has been examined the high temperature irradiation variations testing in order to be used to determine avalanche photodiode lifetime, even though APD failure mechanisms are more sensitive to increases in current density. As a measured parameter of degradation, the current density is of great significance when searching for failure modes in APD. Raising the current density however, is not really indicative of lifetime since it is more likely a situation to be avoided than one that simulates normal lifetime degradation. The reliability of semiconductor detectors is very dependent on the degradation modes. This paper has investigated deeply some of the degradation performance and capabilities of typical APDs currently used in many communication and sensing systems over wide range of the affecting parameters. APDs are used in systems that require coherent and often single mode light such as high data rate communications and sensing applications. APDs are an attractive receiver choice for photon-starved (low signal applications, because their internal gain mechanism can improve signal to noise ratio. An optical receiver must also be appropriate for the laser wavelength being used. The near infrared is the preferred wavelength regime for deep space optical communications largely due to the wavelengths of available laser technologies that meet the optical power requirements of a deep space optical link

  7. Nano-Multiplication-Region Avalanche Photodiodes and Arrays

    Science.gov (United States)

    Zheng, Xinyu; Pain, Bedabrata; Cunningham, Thomas

    2008-01-01

    Nano-multiplication-region avalanche photodiodes (NAPDs), and imaging arrays of NAPDs integrated with complementary metal oxide/semiconductor (CMOS) active-pixel-sensor integrated circuitry, are being developed for applications in which there are requirements for high-sensitivity (including photoncounting) detection and imaging at wavelengths from about 250 to 950 nm. With respect to sensitivity and to such other characteristics as speed, geometric array format, radiation hardness, power demand of associated circuitry, size, weight, and robustness, NAPDs and arrays thereof are expected to be superior to prior photodetectors and arrays including CMOS active-pixel sensors (APSs), charge-coupled devices (CCDs), traditional APDs, and microchannelplate/ CCD combinations. Figure 1 depicts a conceptual NAPD array, integrated with APS circuitry, fabricated on a thick silicon-on-insulator wafer (SOI). Figure 2 presents selected aspects of the structure of a typical single pixel, which would include a metal oxide/semiconductor field-effect transistor (MOSFET) integrated with the NAPD. The NAPDs would reside in silicon islands formed on the buried oxide (BOX) layer of the SOI wafer. The silicon islands would be surrounded by oxide-filled insulation trenches, which, together with the BOX layer, would constitute an oxide embedding structure. There would be two kinds of silicon islands: NAPD islands for the NAPDs and MOSFET islands for in-pixel and global CMOS circuits. Typically, the silicon islands would be made between 5 and 10 m thick, but, if necessary, the thickness could be chosen outside this range. The side walls of the silicon islands would be heavily doped with electron-acceptor impurities (p+-doped) to form anodes for the photodiodes and guard layers for the MOSFETs. A nanoscale reach-through structure at the front (top in the figures) central position of each NAPD island would contain the APD multiplication region. Typically, the reach-through structure would be

  8. Studies of neutron irradiation of avalanche photodiodes using sup 2 sup 5 sup 2 Cf

    CERN Document Server

    Musienko, Y; Ruuska, D; Swain, J D

    2000-01-01

    Results on the radiation hardness of photodiodes to fast neutrons are presented. Four photodiodes (three avalanche photodiodes from two manufacturers, and one PIN photodiode) were exposed to neutrons from a sup 2 sup 5 sup 2 Cf source at Oak Ridge National Laboratory. The effects of this radiation on many parameters such as gain, intrinsic dark current, quantum efficiency, noise, capacitance, and voltage and temperature coefficients of the gain for these devices for fluences up to approx 2x10 sup 1 sup 3 neutrons/cm sup 2 are shown and discussed. While degradation of APDs occurred during neutron irradiation, they remained photosensitive devices with gain.

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

    International Nuclear Information System (INIS)

    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 232Th and 4.2% (240 keV FWHM) for 236Pu. 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)

  10. Development of Fuses for Protection of Geiger-Mode Avalanche Photodiode Arrays

    Science.gov (United States)

    Grzesik, Michael; Bailey, Robert; Mahan, Joe; Ampe, Jim

    2015-11-01

    Current-limiting fuses composed of Ti/Al/Ni were developed for use in Geiger-mode avalanche photodiode arrays for each individual pixel in the array. The fuses were designed to burn out at ˜4.5 × 10-3 A and maintain post-burnout leakage currents less than 10-7 A at 70 V sustained for several minutes. Experimental fuse data are presented and successful incorporation of the fuses into a 256 × 64 pixel InP-based Geiger-mode avalanche photodiode array is reported.

  11. Low dark count geiger mode avalanche photodiodes fabricated in conventional CMOS technologies

    OpenAIRE

    Vilella Figueras, Eva; Arbat Casas, Anna; Alonso Casanovas, Oscar; Comerma Montells, Albert; Trenado, J.; Vilà i Arbonès, Anna Maria; Casanova Mohr, Raimon; Garrido Beltrán, Lluís; Diéguez Barrientos, Àngel

    2011-01-01

    Avalanche photodiodes operated in the Geiger mode present very high intrinsic gain and fast time response, which make the sensor an ideal option for those applications in which detectors with high sensitivity and velocity are required. Moreover, they are compatible with conventional CMOS technologies, allowing sensor and front-end electronics integration within the pixel cell. Despite these excellent qualities, the photodiode suffers from high intrinsic noise, which degrades the performance o...

  12. InAlAs/InGaAs avalanche photodiode arrays for free space optical communication.

    Science.gov (United States)

    Ferraro, Mike S; Clark, William R; Rabinovich, William S; Mahon, Rita; Murphy, James L; Goetz, Peter G; Thomas, Linda M; Burris, Harris R; Moore, Christopher I; Waters, William D; Vaccaro, Kenneth; Krejca, Brian D

    2015-11-01

    In free space optical communication, photodetectors serve not only as communications receivers but also as position sensitive detectors (PSDs) for pointing, tracking, and stabilization. Typically, two separate detectors are utilized to perform these tasks, but recent advances in the fabrication and development of large-area, low-noise avalanche photodiode (APD) arrays have enabled these devices to be used both as PSDs and as communications receivers. This combined functionality allows for more flexibility and simplicity in optical system design without sacrificing the sensitivity and bandwidth performance of smaller, single-element data receivers. This work presents the development of APD arrays rated for bandwidths beyond 1 GHz with measured carrier ionization ratios of approximately 0.2 at moderate APD gains. We discuss the fabrication and characterization of three types of APD arrays along with their performance as high-speed photodetectors. PMID:26560607

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

    Science.gov (United States)

    Aull, Brian

    2016-01-01

    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. PMID:27070609

  14. Photoionization of Trapped Carriers in Avalanche Photodiodes to Reduce Afterpulsing During Geiger-Mode Photon Counting

    Science.gov (United States)

    Krainak, Michael A.

    2005-01-01

    We reduced the afterpulsing probability by a factor of five in a Geiger-mode photon-counting InGaAs avalanche photodiode by using sub-band-gap (lambda = 1.95 micron) laser diode illumination, which we believe photoionizes the trapped carriers.

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

    OpenAIRE

    Brian Aull

    2016-01-01

    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.

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

    Directory of Open Access Journals (Sweden)

    Brian Aull

    2016-04-01

    Full Text Available 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.

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

    Science.gov (United States)

    Aull, Brian

    2016-01-01

    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. PMID:27070609

  18. HgCdTe Infrared Avalanche Photodiode Single Photon Detector Arrays for the LIST and Other Decadal Missions Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Develop a HgCdTe avalanche photodiode (APD)  SWIR/IR linear mode photon counting (LMPC) array detector system in support of the LIST lidar. Provide a new type...

  19. High-Speed Radiation Tolerant Avalanche Photodiodes Based on InGaN for Space Altimeter Systems Project

    Data.gov (United States)

    National Aeronautics and Space Administration — High-performance, radiation-tolerant detectors are required for the time-of-flight laser based rangefinders. Avalanche photodiodes (APDs) are conventionally chosen...

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

    International Nuclear Information System (INIS)

    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.

  1. Commercially available Geiger mode single-photon avalanche photodiode with a very low afterpulsing probability

    CERN Document Server

    Stipčević, Mario

    2015-01-01

    Afterpulsing is one of the main technological flaws present in photon counting detectors based on solid-state semiconductor avalanche photodiodes operated in Geiger mode. Level of afterpulsing depends mainly on type of the semiconductor, doping concentrations and temperature and presents an additional source of noise, along with dark counts. Unlike dark counts which appear randomly in time, aterpulses and are time-correlated with the previous detections. For measurements that rely on timing information afterpulsing can create fake signals and diminish the sensitivity. In this work we test a novel broadband sensitive APD that was designed for sub-Geiger avalanche gain operation. We find that this APD, which has a reach-through geometry typical of single-photon detection photodiodes, can also operate in Geiger mode with usable detection sensitivity and acceptable dark counts level while exhibiting uniquely low afterpulsing. The afterpulsing of tested samples was systematically less than 0.05 percent at 10V exce...

  2. Avoiding sensor blindness in Geiger mode avalanche photodiode arrays fabricated in a conventional CMOS process

    OpenAIRE

    Vilella Figueras, Eva; Diéguez Barrientos, Àngel

    2011-01-01

    The need to move forward in the knowledge of the subatomic world has stimulated the development of new particle colliders. However, the objectives of the next generation of colliders sets unprecedented challenges to the detector performance. The purpose of this contribution is to present a bidimensional array based on avalanche photodiodes operated in the Geiger mode to track high energy particles in future linear colliders. The bidimensional array can function in a gated mode to reduce the p...

  3. Silicon Geiger-mode avalanche photodiode arrays for photon-starved imaging

    Science.gov (United States)

    Aull, Brian F.

    2015-05-01

    Geiger-mode avalanche photodiodes (GMAPDs) are capable of detecting single photons. They can be operated to directly trigger all-digital circuits, so that detection events are digitally counted or time stamped in each pixel. An imager based on an array of GMAPDs therefore has zero readout noise, enabling quantum-limited sensitivity for photon-starved imaging applications. In this review, we discuss devices developed for 3D imaging, wavefront sensing, and passive imaging.

  4. Al0.52In0.48P avalanche photodiodes for soft X-ray spectroscopy

    International Nuclear Information System (INIS)

    The performance of Al0.52In0.48P avalanche photodiodes was assessed as soft X-ray detectors at room temperature. The effect of the avalanche gain improved the energy resolution and an energy resolution (FWHM) of 682 eV is reported for 5.9 keV X-rays

  5. Avalanche photodiode with high responsivity in 0.35 μm CMOS

    Science.gov (United States)

    Gaberl, Wolfgang; Schneider-Hornstein, Kerstin; Enne, Reinhard; Steindl, Bernhard; Zimmermann, Horst

    2014-04-01

    The presented linear mode avalanche photodiode (APD) uses the standard layers and process steps available in the 0.35-μm Si bulk CMOS process. Due to a low-doped epitaxial layer with a resistivity of 664 Ω cm, a deep intrinsic zone is realized to enable a large depleted absorption region at already moderate bias voltages and therefore ensures a high low-voltage responsivity. In combination with avalanche gain at high bias voltages, this leads to an overall responsivity of 1.7×105 A/W at 1.1 nW optical input power and 670-nm wavelength. The maximum achieved avalanche gain was 4.94×105. The maximum -3 dB frequency of 700 MHz was measured at a reverse bias voltage of 30 V and an optical input power of 14.7 μW.

  6. Plasmonic field confinement for separate absorption-multiplication in InGaAs nanopillar avalanche photodiodes

    Science.gov (United States)

    Farrell, Alan C.; Senanayake, Pradeep; Hung, Chung-Hong; El-Howayek, Georges; Rajagopal, Abhejit; Currie, Marc; Hayat, Majeed M.; Huffaker, Diana L.

    2015-12-01

    Avalanche photodiodes (APDs) are essential components in quantum key distribution systems and active imaging systems requiring both ultrafast response time to measure photon time of flight and high gain to detect low photon flux. The internal gain of an APD can improve system signal-to-noise ratio (SNR). Excess noise is typically kept low through the selection of material with intrinsically low excess noise, using separate-absorption-multiplication (SAM) heterostructures, or taking advantage of the dead-space effect using thin multiplication regions. In this work we demonstrate the first measurement of excess noise and gain-bandwidth product in III-V nanopillars exhibiting substantially lower excess noise factors compared to bulk and gain-bandwidth products greater than 200 GHz. The nanopillar optical antenna avalanche detector (NOAAD) architecture is utilized for spatially separating the absorption region from the avalanche region via the NOA resulting in single carrier injection without the use of a traditional SAM heterostructure.

  7. Impact ionisation measurement and modelling of long wavelength avalanche photodiodes

    CERN Document Server

    Ng, J S

    2003-01-01

    Impact ionisation coefficients are measured in In sub 0 sub . sub 5 sub 3 Ga sub 0 sub . sub 4 sub 7 As and excess noise characteristics are measured in sub-micron ln sub 0 sub . sub 5 sub 2 Al sub 0 sub . sub 4 sub 8 As. Photomultiplication measurements performed on a series of In sub 0 sub . sub 5 sub 3 Ga sub 0 sub . sub 4 sub 7 As p-i-n diodes are reported. Taking careful account of factors which could give rise to erroneous results at low fields, ln sub 0 sub . sub 5 sub 3 Ga sub 0 sub . sub 4 sub 7 As ionisation coefficients are deduced at room temperature as a function of electric field. The results confirm the low field ionisation behaviour of alpha and the conventional field dependence of beta. Excess avalanche noise factors of In sub 0 sub . sub 5 sub 2 Al sub 0 sub . sub 4 sub 8 As p-i-n diodes, with i-region thicknesses ranging from 1.0 mu m to 0.1 mu m, are reported. The results indicate effective beta/alpha values lying between 0.15 and 0.23, comparable with or lower than the values reported in ...

  8. 3D integration of Geiger-mode avalanche photodiodes aimed to very high fill-factor pixels for future linear colliders 

    CERN Document Server

    Vilella, E; Dieguez, A

    2013-01-01

    This paper presents an analysis of the maximum achievable fill-factor by a pixel detector of Geiger-mode avalanche photodiodes with the Chartered 130 nm/Tezzaron 3D process. The analysis shows that fillfactors between 66% and 96% can be obtained with different array architectures and a time-gated readout circuit of minimum area. The maximum fill-factor is achieved when the two-layer vertical stack is used to overlap the non-sensitive areas of one layer with the sensitive areas of the other one. Moreover, different sensor areas are used to further increase the fill-factor. A chip containing a pixel detector of the Geigermode avalanche photodiodes and aimed to future linear colliders has been designed with the Chartered 130 nm/Tezzaron 3D process to increase the fill-factor.

  9. Development of Gated Pinned Avalanche Photodiode Pixels for High-Speed Low-Light Imaging

    Directory of Open Access Journals (Sweden)

    Tomislav Resetar

    2016-08-01

    Full Text Available This work explores the benefits of linear-mode avalanche photodiodes (APDs in high-speed CMOS imaging as compared to different approaches present in literature. Analysis of APDs biased below their breakdown voltage employed in single-photon counting mode is also discussed, showing a potentially interesting alternative to existing Geiger-mode APDs. An overview of the recently presented gated pinned avalanche photodiode pixel concept is provided, as well as the first experimental results on a 8 × 16 pixel test array. Full feasibility of the proposed pixel concept is not demonstrated; however, informative data is obtained from the sensor operating under −32 V substrate bias and clearly exhibiting wavelength-dependent gain in frontside illumination. The readout of the chip designed in standard 130 nm CMOS technology shows no dependence on the high-voltage bias. Readout noise level of 15 e - rms, full well capacity of 8000 e - , and the conversion gain of 75 µV / e - are extracted from the photon-transfer measurements. The gain characteristics of the avalanche junction are characterized on separate test diodes showing a multiplication factor of 1.6 for red light in frontside illumination.

  10. Development of Gated Pinned Avalanche Photodiode Pixels for High-Speed Low-Light Imaging.

    Science.gov (United States)

    Resetar, Tomislav; De Munck, Koen; Haspeslagh, Luc; Rosmeulen, Maarten; Süss, Andreas; Puers, Robert; Van Hoof, Chris

    2016-01-01

    This work explores the benefits of linear-mode avalanche photodiodes (APDs) in high-speed CMOS imaging as compared to different approaches present in literature. Analysis of APDs biased below their breakdown voltage employed in single-photon counting mode is also discussed, showing a potentially interesting alternative to existing Geiger-mode APDs. An overview of the recently presented gated pinned avalanche photodiode pixel concept is provided, as well as the first experimental results on a 8 × 16 pixel test array. Full feasibility of the proposed pixel concept is not demonstrated; however, informative data is obtained from the sensor operating under -32 V substrate bias and clearly exhibiting wavelength-dependent gain in frontside illumination. The readout of the chip designed in standard 130 nm CMOS technology shows no dependence on the high-voltage bias. Readout noise level of 15 e - rms, full well capacity of 8000 e - , and the conversion gain of 75 µV / e - are extracted from the photon-transfer measurements. The gain characteristics of the avalanche junction are characterized on separate test diodes showing a multiplication factor of 1.6 for red light in frontside illumination. PMID:27537882

  11. Pixelated Geiger-Mode Avalanche Photo-Diode Characterization through Dark Current Measurement

    CERN Document Server

    Amaudruz, Pierre-André; Gilhully, Colleen; Goertzen, Andrew; James, Lloyd; Kozlowski, Piotr; Retière, Fabrice; Shams, Ehsan; Sossi, Vesna; Stortz, Greg; Thiessen, Jonathan D; Thompson, Christopher J

    2013-01-01

    PIXELATED geiger-mode avalanche photodiodes(PPDs), often called silicon photomultipliers (SiPMs) are emerging as an excellent replacement for traditional photomultiplier tubes (PMTs) in a variety of detectors, especially those for subatomic physics experiments, which requires extensive test and operation procedures in order to achieve uniform responses from all the devices. In this paper, we show for two PPD brands, Hamamatsu MPPC and SensL SPM, that the dark noise rate, breakdown voltage and rate of correlated avalanches can be inferred from the sole measure of dark current as a function of operating voltage, hence greatly simplifying the characterization procedure. We introduce a custom electronics system that allows measurement for many devices concurrently, hence allowing rapid testing and monitoring of many devices at low cost. Finally, we show that the dark current of Hamamastu Multi-Pixel Photon Counter (MPPC) is rather independent of temperature at constant operating voltage, hence the current measure...

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

    Science.gov (United States)

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

    2012-01-01

    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. PMID:22273682

  13. Germanium-tin multiple quantum well on silicon avalanche photodiode for photodetection at two micron wavelength

    Science.gov (United States)

    Dong, Yuan; Wang, Wei; Lee, Shuh Ying; Lei, Dian; Gong, Xiao; Khai Loke, Wan; Yoon, Soon-Fatt; Liang, Gengchiau; Yeo, Yee-Chia

    2016-09-01

    We report the demonstration of a germanium-tin multiple quantum well (Ge0.9Sn0.1 MQW)-on-Si avalanche photodiode (APD) for light detection near the 2 μm wavelength range. The measured spectral response covers wavelengths from 1510 to 2003 nm. An optical responsivity of 0.33 A W-1 is achieved at 2003 nm due to the internal avalanche gain. In addition, a thermal coefficient of breakdown voltage is extracted to be 0.053% K-1 based on the temperature-dependent dark current measurement. As compared to the traditional 2 μm wavelength APDs, the Si-based APD is promising for its small excess noise factor, less stringent demand on temperature stability, and its compatibility with silicon technology.

  14. Germanium-tin multiple quantum well on silicon avalanche photodiode for photodetection at two micron wavelength

    Science.gov (United States)

    Dong, Yuan; Wang, Wei; Lee, Shuh Ying; Lei, Dian; Gong, Xiao; Khai Loke, Wan; Yoon, Soon-Fatt; Liang, Gengchiau; Yeo, Yee-Chia

    2016-09-01

    We report the demonstration of a germanium-tin multiple quantum well (Ge0.9Sn0.1 MQW)-on-Si avalanche photodiode (APD) for light detection near the 2 μm wavelength range. The measured spectral response covers wavelengths from 1510 to 2003 nm. An optical responsivity of 0.33 A W‑1 is achieved at 2003 nm due to the internal avalanche gain. In addition, a thermal coefficient of breakdown voltage is extracted to be 0.053% K‑1 based on the temperature-dependent dark current measurement. As compared to the traditional 2 μm wavelength APDs, the Si-based APD is promising for its small excess noise factor, less stringent demand on temperature stability, and its compatibility with silicon technology.

  15. Improved X-ray detection and particle identification with avalanche photodiodes

    CERN Document Server

    Diepold, Marc; Machado, Jorge; Amaro, Pedro; Abdou-Ahmed, Marwan; Amaro, Fernando D; Antognini, Aldo; Biraben, François; Chen, Tzu-Ling; Covita, Daniel S; Dax, Andreas J; Franke, Beatrice; Galtier, Sandrine; Gouvea, Andrea L; Götzfried, Johannes; Graf, Thomas; Hänsch, Theodor W; Hildebrandt, Malte; Indelicato, Paul; Julien, Lucile; Kirch, Klaus; Knecht, Andreas; Kottmann, Franz; Krauth, Julian J; Liu, Yi-Wei; Monteiro, Cristina M B; Mulhauser, Françoise; Naar, Boris; Nebel, Tobias; Nez, François; Santos, José Paulo; Santos, Joaquim M F dos; Schuhmann, Karsten; Szabo, Csilla I; Taqqu, David; Veloso, João F C A; Voss, Andreas; Weichelt, Birgit; Pohl, Randolf

    2015-01-01

    Avalanche photodiodes are commonly used as detectors for low energy x-rays. In this work we report on a fitting technique used to account for different detector responses resulting from photo absorption in the various APD layers. The use of this technique results in an improvement of the energy resolution at 8.2 keV by up to a factor of 2, and corrects the timing information by up to 25 ns to account for space dependent electron drift time. In addition, this waveform analysis is used for particle identification, e.g. to distinguish between x-rays and MeV electrons in our experiment.

  16. Resilience of gated avalanche photodiodes against bright illumination attacks in quantum cryptography

    CERN Document Server

    Yuan, Z L; Shields, A J; 10.1063/1.3597221

    2011-01-01

    Semiconductor avalanche photodiodes (APDs) are commonly used for single photon detection in quantum key distribution. Recently, many attacks using bright illumination have been proposed to manipulate gated InGaAs APDs. In order to devise effective counter-measures, careful analysis of these attacks must be carried out to distinguish between incorrect operation and genuine loopholes. Here, we show that correctly-operated, gated APDs are immune to continuous-wave illumination attacks, while monitoring the photocurrent for anomalously high values is a straightforward counter-measure against attacks using temporally tailored light.

  17. Properties of the most recent avalanche photodiodes for the CMS electromagnetic calorimeter

    CERN Document Server

    Deiters, K; Nicol, S; Patel, B; Renker, D; Reucroft, S; Rusack, R W; Sakhelashvili, T M; Swain, J D; Vikas, P

    2000-01-01

    Avalanche photodiodes (APDs) with improved characteristics are being developed by Hamamatsu Photonics for the electromagnetic calorimeter of the CMS experiment. More than 30 prototypes have been made and investigated during the last 3 years in a development program, that showed significant progress. The parameters of the most recent APDs including the long-term stability and the effect of high radiation levels with a neutron fluence of 2*10/sup 13/ n/cm/sup 2/ have been studied and are presented. (4 refs).

  18. HgCdTe e-avalanche photodiode detector arrays

    OpenAIRE

    Anand Singh; Shukla, A. K.; Ravinder Pal

    2015-01-01

    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 w...

  19. Interplanetary space weather effects on Lunar Reconnaissance Orbiter avalanche photodiode performance

    Science.gov (United States)

    Clements, E. B.; Carlton, A. K.; Joyce, C. J.; Schwadron, N. A.; Spence, H. E.; Sun, X.; Cahoy, K.

    2016-05-01

    Space weather is a major concern for radiation-sensitive space systems, particularly for interplanetary missions, which operate outside of the protection of Earth's magnetic field. We examine and quantify the effects of space weather on silicon avalanche photodiodes (SiAPDs), which are used for interplanetary laser altimeters and communications systems and can be sensitive to even low levels of radiation (less than 50 cGy). While ground-based radiation testing has been performed on avalanche photodiode (APDs) for space missions, in-space measurements of SiAPD response to interplanetary space weather have not been previously reported. We compare noise data from the Lunar Reconnaissance Orbiter (LRO) Lunar Orbiter Laser Altimeter (LOLA) SiAPDs with radiation measurements from the onboard Cosmic Ray Telescope for the Effects of Radiation (CRaTER) instrument. We did not find any evidence to support radiation as the cause of changes in detector threshold voltage during radiation storms, both for transient detector noise and long-term average detector noise, suggesting that the approximately 1.3 cm thick shielding (a combination of titanium and beryllium) of the LOLA detectors is sufficient for SiAPDs on interplanetary missions with radiation environments similar to what the LRO experienced (559 cGy of radiation over 4 years).

  20. High-speed imaging and wavefront sensing with an infrared avalanche photodiode array

    CERN Document Server

    Baranec, Christoph; Riddle, Reed; Hall, Donald; Jacobson, Shane; Law, Nicholas M; Chun, Mark

    2015-01-01

    Infrared avalanche photodiode 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 avalanche photodiode array that achieves a correlated double sampling read noise of 0.73 e- in the lab, and a total noise of 2.52 e- on sky, and supports simultaneous high-speed imaging and tip-tilt wavefront sensing with the Robo-AO visible-light laser adaptive optics system at the Palomar Observatory 1.5-m telescope. We report here on the improved image quality achieved simultaneously at visible and infrared wavelengths by using the array as part of an image stabilization control-loop with adaptive-optics 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 adaptive optics and high-contrast imaging applications.

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

    International Nuclear Information System (INIS)

    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

  2. Noise Temperature Characteristics and Gain-control of Avalanche Photodiodes for Laser Radar

    Institute of Scientific and Technical Information of China (English)

    CAI Xi-ping; SHANG Hong-Bo; BAI Ji-yuan; YANG Shuang; WANG Li-na

    2008-01-01

    Avalanche photodiodes(APDs) are promising light sensors with high quantum efficiency and low noise. It has been extensively used in radiation detection, laser radar and other weak signal detection fields. Unlike other photodiodes, APD is a very sensitive light detector with very high internal gain. The basic theory shows that the gain of APD is related to the temperature. The internal gain fluctuates with the variation of temperature. Investigated was the influence of the variation of the gain induced by the fluctuation of temperature on the output from APD for a very weak laser pulse input in laser radar. An active reverse-biased voltage compensation method is used to stabilize the gain of APD. An APD model is setup to simulate the detection of light pulse signal. The avalanche process, various noises and temperature's effect are all included in the model. Our results show that for the detection of weak light signal such as in laser radar, even a very small fluctuation of temperature could cause a great effect on APD's gain. The results show that the signal-to-noise ratio of the APD's output could be improved effectively with the active gain-control system.

  3. Linear mode photon counting with the noiseless gain HgCdTe e-avalanche photodiode

    Science.gov (United States)

    Beck, Jeffrey D.; Scritchfield, Richard; Mitra, Pradip; Sullivan, William W.; Gleckler, Anthony D.; Strittmatter, Robert; Martin, Robert J.

    2014-08-01

    A linear mode photon counting focal plane array using HgCdTe mid-wave infrared (MWIR) cutoff electron initiated avalanche photodiodes (e-APDs) has been designed, fabricated, and characterized. The broad spectral range (0.4 to 4.3 μm) is unique among photon counters, making this a "first of its kind" system spanning the visible to the MWIR. The low excess noise [F(M)≈1] of the e-APDs allows for robust photon detection while operating at a stable linear avalanche gain in the range of 500-1000. The readout integrated circuit (ROIC) design included a very high gain-bandwidth product resistive transimpedance amplifier (3×1013 Ω-Hz) and a 4 ns output digital pulse width comparator. The ROIC had 16 high-bandwidth analogs and 16 low-voltage differential signaling digital outputs. The 2×8 array was integrated into an LN2 Dewar with a custom leadless chip carrier and daughter board design that preserved high-bandwidth analog and digital signal integrity. The 2×8 e-APD arrays were fabricated on 4.3 μm cutoff HgCdTe and operated at 84 K. The measured dark currents were approximately 1 pA at 13 V bias where the measured avalanche photodiode gain was 500. This translates to a predicted dark current induced dark count rate of less than 20 KHz. Single photon detection was achieved with a photon pulse signal-to-noise ratio of 13.7 above the amplifier noise floor. A photon detection efficiency of 50% was measured at a photon background limited false event rate of about 1 MHz. The measured jitter was in the range of 550-800 ps. The demonstrated minimum time between distinguishable events was less than 10 ns.

  4. 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.

  5. InAs/InAsSb Avalanche Photodiode (APD) for applicaions in long-wavelength infrared region

    Institute of Scientific and Technical Information of China (English)

    P.K.Maurya; H.Agarwal; A.Singh; P.Chakrabarti

    2008-01-01

    A generic numerical model of a long-wavelength Avalanche Photodiode (APD) based on narrow bandgap semiconductor InAsSb on lnAs substrate is reported for the first time. This model has been applied for theoretical characterization of a proposed N+ InAS/P-InAsSb avalanche photodiode structure for possible application in 2-5 μm wavelength region. The parameters such as gain, excess noise factor and their trade-offwith variation of doping concentration and bias voltage have been estimated for the APD taking into account history-dependent theory of avalanche multiplication process. The LWIR APD is expected to find application in optical gas sensor and in future generation of optical communication system.

  6. A method to precisely identify the afterpulses when using the S9717 avalanche photodiode

    Science.gov (United States)

    Rusu, Alexandru; Rusu, Lucian

    2015-12-01

    The detection ratio of an avalanche photodiode (APD) biased in Geiger-mode increases versus the excess voltage; the afterpulsing rate increases too. The last one can be reduced by inserting an artificial dead time and accepting a lower measuring top rate. So, in order to tune a single-photon detector system, it is necessary to exactly identify afterpulses and measure their rate; the experimental results are presented. When using the S9717 APD in Geiger-mode, the cathode to ground voltage waveform reveals the existence of a particular sequence of pulses: a usual one followed, within 1μs, by a least one appearing to have been generated for negative excess voltage values. All these characteristics are the signature of the afterpulsing generation. Based on this observation, we were able to precisely measure the afterpulsing rate.

  7. A method to precisely identify the afterpulses when using the S9717 avalanche photodiode

    Energy Technology Data Exchange (ETDEWEB)

    Rusu, Alexandru, E-mail: alrusu@nipne.ro; Rusu, Lucian [“Horia Hulubei” National Institute for Physics and Nuclear Engineering, Reactorului Street, No. 34, City Măgurele, jud. Ilfov, POB 077125 (Romania)

    2015-12-07

    The detection ratio of an avalanche photodiode (APD) biased in Geiger-mode increases versus the excess voltage; the afterpulsing rate increases too. The last one can be reduced by inserting an artificial dead time and accepting a lower measuring top rate. So, in order to tune a single-photon detector system, it is necessary to exactly identify afterpulses and measure their rate; the experimental results are presented. When using the S9717 APD in Geiger-mode, the cathode to ground voltage waveform reveals the existence of a particular sequence of pulses: a usual one followed, within 1μs, by a least one appearing to have been generated for negative excess voltage values. All these characteristics are the signature of the afterpulsing generation. Based on this observation, we were able to precisely measure the afterpulsing rate.

  8. Numerical analysis of single photon detection avalanche photodiodes operated in the Geiger mode

    Science.gov (United States)

    Sugihara, K.; Yagyu, E.; Tokuda, Y.

    2006-06-01

    For a wide range of the thicknesses of the charge and the multiplication layers, detection efficiency and dark count probability are numerically investigated for GaInAs/InP single photon detection avalanche photodiodes (APD's) which are operated in the Geiger mode. Breakdown probability and dark currents are calculated to evaluate detection efficiency and dark count probability. The result shows that dark count probability can be significantly reduced by increasing the thickness of the charge layer, whereas detection efficiency is expected to decline steeply at some thickness of the charge layer. Moreover, increasing the thickness of the multiplication layer does not continue to reduce dark count probability, which increases when the multiplication layer is thicker than a critical thickness. Finally, we show a design guideline of single photon detection APD's with higher detection efficiency and lower dark count probability.

  9. A cooled avalanche photodiode detector for X-ray magnetic diffraction experiments

    CERN Document Server

    Kishimoto, S; Ito, M

    2001-01-01

    A cooled avalanche photodiode (APD) detector was developed for X-ray magnetic diffraction experiments. A stack of four silicon APDs was cooled down to 243 K by a thermoelectric cooler. The energy widths of 0.89 and 1.55 keV (FWHM) were obtained for 8.05 keV X-rays at 1x10 sup 6 s sup - sup 1 and for 16.53 keV X-rays at 2x10 sup 6 s sup - sup 1 , respectively. Test measurements of X-ray magnetic diffraction were executed using a terbium single crystal and white synchrotron radiation. A peak width of (1 0 3) reflection (5.4 keV) was roughly three times wider than that with a high-purity germanium detector.

  10. 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...

  11. Application of PN and avalanche silicon photodiodes to low-level optical

    Science.gov (United States)

    Eppeldauer, G.; Schaefer, A. R.

    1988-01-01

    New approaches to the discovery of other planetary systems require very sensitive and stable detection techniques in order to succeed. Two methods in particular, the astrometric and the photometric methods, require this. To begin understanding the problems and limitations of solid state detectors regarding this application, preliminary experiments were performed at the National Bureau of Standards and a low light level detector characterization facility was built. This facility is briefly described, and the results of tests conducted in it are outlined. A breadboard photometer that was used to obtain stellar brightness ratio precision data is described. The design principles of PN and avalanche silicon photodiodes based on low light level measuring circuits are discussed.

  12. 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).

  13. Dark-current characteristics of GaN-based UV avalanche photodiodes

    Science.gov (United States)

    Xu, Jintong; Chang, Chao; Li, Xiangyang

    2015-04-01

    For UV detecting, it needs high ratio of signal to noise, which means high responsibility and low noise. GaN-based avalanche photodiodes can provide a high internal photocurrent gain. In this paper, we report the testing and characterization of GaN based thin film materials, optimization design of device structure, the device etching and passivation technology, and the photoelectric characteristics of the devices. Also, uniformity of the device was obtained. The relationship between dark current and material quality or device processes was the focus of this study. GaN based material with high aluminum components have high density defects. Scanning electron microscope, cathodoluminescence spectra, X-ray double crystal diffraction and transmission spectroscopy testing were employed to evaluate the quality of GaN-based material. It shows that patterned sapphire substrate or thick AlN buffer layer is more effective to get high quality materials. GaN-based materials have larger hole ionization coefficient, so back incident structure were adopted to maximize the hole-derived multiplication course and it was helped to get a smaller multiplication noise. The device with separate absorption and multiplication regions is also prospective to reduce the avalanche noise. According to AlGaN based material characteristics and actual device fabrication, device structure was optimized further. Low physical damage inductively coupled plasma (ICP) etching method was used to etch mesa and wet etching method was employed to treat mesa damage. Silica is passivation material of device mesa. For solar-blind ultraviolet device, it is necessary to adopt a wider bandgap material than AlGaN material. The current-voltage characteristics under reverse bias were measured in darkness and under UV illumination. The distribution of dark current and response of different devices was obtained. In short, for GaN-based UV avalanche photodiode, dark current was related to high density dislocation of

  14. A test beam set-up for the characterization of the Geiger-mode avalanche photodiode technology for particle tracking

    CERN Document Server

    Vilella, A; Trenado, J; Vila, A; Casanova, R; Vos, M; Garrido, L; Dieguez, A

    2012-01-01

    It is well known that avalanche photodiodes operated in the Geiger mode above the breakdown voltage offer a virtually infinite gain and time accuracy in the picosecond range that can be used for single photon detection. However, their performance in particle detection still remains unexplored. In this contribution, we are going to expose different steps that we have taken in order to prove the efficiency of the Geiger mode avalanche photodiodes in the aforementioned field. In particular, we will present a setup for the characterization of these sensors in a test beam. The expected results of the test beam at DESY and CERN have been simulated with Geant4 and will also be exposed.

  15. A PMT-like high gain avalanche photodiode based on GaN/AlN periodical stacked structure

    CERN Document Server

    Zheng, Ji-yuan; Yang, Di; Yu, Jia-dong; Meng, Xiao; E, Yan-xiong; Wu, Chao; Hao, Zhi-biao; Sun, Chang-zheng; Xiong, Bing; Luo, Yi; Han, Yan-jian; Wang, Jian; Li, Hong-tao; Brault, Julien; Matta, Samuel; Khalfioui, Mohamed Al; Yan, Jian-chang; Wei, Tong-bo; Zhang, Yun; Wang, Jun-xi

    2016-01-01

    Avalanche photodiode (APD) has been intensively investigated as a promising candidate to replace photomultiplier tubes (PMT) for weak light detection. However, in conventional APDs, a large portion of carrier energy drawn from the electric field is thermalized, and the multiplication efficiencies of electron and hole are low and close. In order to achieve high gain, the device should work under breakdown bias, where carrier multiplication proceeds bi-directionally to form a positive feedback multiplication circle. However, breakdown is hard to control, in practice, APDs should work under Geiger mode as a compromise between sustainable detection and high gain. The complexity of system seriously restricts the application. Here, we demonstrate an avalanche photodiode holding high gain without breakdown, which means no quenching circuit is needed for sustainable detection. The device is based on a GaN/AlN periodically-stacked-structure (PSS), wherein electron holds much higher efficiency than hole to draw energy ...

  16. Development of novel technologies to enhance performance and reliability of III-Nitride avalanche photodiodes

    Science.gov (United States)

    Suvarna, Puneet Harischandra

    Solar-blind ultraviolet avalanche photodiodes are an enabling technology for applications in the fields of astronomy, communication, missile warning systems, biological agent detection and particle physics research. Avalanche photodiodes (APDs) are capable of detecting low-intensity light with high quantum efficiency and signal-to-noise ratio without the need for external amplification. The properties of III-N materials (GaN and AlGaN) are promising for UV photodetectors that are highly efficient, radiation-hard and capable of visible-blind or solar-blind operation without the need for external filters. However, the realization of reliable and high performance III-N APDs and imaging arrays has several technological challenges. The high price and lack of availability of bulk III-N substrates necessitates the growth of III-Ns on lattice mismatched substrates leading to a high density of dislocations in the material that can cause high leakage currents, noise and premature breakdown in APDs. The etched sidewalls of III-N APDs and high electric fields at contact edges are also detrimental to APD performance and reliability. In this work, novel technologies have been developed and implemented that address the issues of performance and reliability in III-Nitride based APDs. To address the issue of extended defects in the bulk of the material, a novel pulsed MOCVD process was developed for the growth of AlGaN. This process enables growth of high crystal quality AlxGa1-xN with excellent control over composition, doping and thickness. The process has also been adapted for the growth of high quality III-N materials on silicon substrate for devices such as high electron mobility transistors (HEMTs). A novel post-growth defect isolation technique is also discussed that can isolate the impact of conductive defects from devices. A new sidewall passivation technique using atomic layer deposition (ALD) of dielectric materials was developed for III-N APDs that is effective in

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

    International Nuclear Information System (INIS)

    In this paper, we discuss results of avalanche photodiodes radiation tests for Projectile Spectator Detector at future Compressed Baryonic Matter experiment. The tests were carried out in Nuclear Physics Institute of ASCR in Řež using the cyclotron facility. Secondary neutron beam was used for irradiation because the main radiation damage in the Projectile Spectator Detector is caused by neutrons. Two types of the avalanche photodiodes from Zecotek and Ketek manufacturers were investigated. Special attention was given to the noise investigation and self-annealing after the irradiation. We have irradiated two Ketek PM3375 diodes with equivalent dose for 1 MeV neutrons equal to 2.5±0.2×1012 n/cm2, and single Zecotek MAPD-3N diode with equivalent dose for 1 MeV neutrons equal to 3.4±0.2×1012 n/cm2. All the types of the diodes have shown an increasing level of the noise after the irradiation. From that we can conclude that those avalanche photodiodes are not able to detect single photons anymore due to high noise levels

  18. High-speed bridge circuit for InGaAs avalanche photodiode single-photon detector

    Science.gov (United States)

    Hashimoto, Hirofumi; Tomita, Akihisa; Okamoto, Atsushi

    2014-02-01

    Because of low power consumption and small footprint, avalanche photodiodes (APD) have been commonly applied to photon detection. Recently, high speed quantum communication has been demonstrated for high bit-rate quantum key distribution. For the high speed quantum communication, photon detectors should operate at GHz-clock frequencies. We propose balanced detection circuits for GHz-clock operation of InGaAs-APD photon detectors. The balanced single photon detector operates with sinusoidal wave gating. The sinusoidal wave appearing in the output is removed by the subtraction from APD signal without sharp band-elimination filters. Omission of the sharp filters removes the constraint on the operating frequency of the single photon detector. We present two designs, one works with two identical APDs, the other with one APD and a low-pass filter. The sinusoidal gating enables to eliminate the gating noise even with the simple configuration of the latter design. We demonstrated the balanced single photon detector operating with 1.020GHz clock at 233 K, 193 K, and 186.5 K. The dark count probability was 4.0 x 10-4 counts/pulse with the quantum efficiency of 10% at 233K, and 1.6 x 10-4 counts/pulse at 186.5 K. These results were obtained with easily available APDs (NR8300FP-C.C, RENESASS) originally developed for optical time-domain reflectmeters.

  19. 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.

  20. 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...

  1. A bismuth germanate-avalanche photodiode module designed for use in high resolution positron emission tomography

    International Nuclear Information System (INIS)

    A light-tight, hermetically sealed module for use in high resolution positron emission tomography systems is described. The module has external dimensions 3.8 x 13.2 x 33 mm and contains two 3 x 5 x 20 Bismuth Germanate (BGO) scintillators, each with its own 3 x 3 mm silicon avalanche photodiode. When stacked, the vertical packing fraction is 80%. As measured with a 137Cs (662 keV) source, the typical energy resolution is 20% at 220C, reducing to 16% at 00C. The single detector time resolution for the 22Na gamma at 511 keV is typically less 20 ns at 220C, reducing to less than 15 ns at 00C. Further cooling does not improve the performance since the emission time of light from BGO increases at lower temperature. Preliminary results with Gadolinium Orthosilicate show similar energy resolution, better timing resolution (under 10 ns), but as is known, a slightly poorer photofraction and stopping power

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

    International Nuclear Information System (INIS)

    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

  3. Recent progress of avalanche photodiodes in high-resolution X-rays and Gamma-rays detection

    CERN Document Server

    Kataoka, J; Kuramoto, Y; Ikagawa, T; Yatsu, Y; Kotoku, J; Arimoto, M; Kawai, N; Ishikawa, Y; Kawabata, N

    2005-01-01

    We have studied the performance of large area avalanche photodiodes (APDs) recently developed by Hamamatsu Photonics K.K, in high-resolution X-rays and Gamma-rays detections. We show that reach-through APD can be an excellent soft X-ray detector operating at room temperature or moderately cooled environment. We obtain the best energy resolution ever achieved with APDs, 6.4 % for 5.9 keV X-rays, and obtain the energy threshold as low as 0.5 keV measured at -20deg. Thanks to its fast timing response, signal carriers in the APD device are collected within a short time interval of 1.9 nsec (FWHM). This type of APDs can therefore be used as a low-energy, high-counting particle monitor onboard the forthcoming Pico-satellite Cute1.7. As a scintillation photon detector, reverse-type APDs have a good advantage of reducing the dark noise significantly. The best FWHM energy resolutions of 9.4+-0.3 % and 4.9+-0.2 % were obtained for 59.5 keV and 662 keV Gamma-rays, respectively, as measured with a CsI(Tl) crystal. Combin...

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

    CERN Document Server

    Anderhub, H; Biland, A; Boller, A; Braun, I; Bretz, T; Commichau, S; Commichau, V; Dorner, D; Gendotti, A; Grimm, O; von Gunten, H; Hildebrand, D; Horisberger, U; Krähenbühl, T; Kranich, D; Lorenz, E; Lustermann, W; Mannheim, K; Neise, D; Pauss, F; Renker, D; Rhode, W; Rissi, M; Röser, U; Rollke, S; Stark, L S; Stucki, J -P; Viertel, G; Vogler, P; Weitzel, Q

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    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 [Institute for Particle Physics, ETH Zurich, Schafmattstr. 20, 8093 Zurich (Switzerland); Backes, M; Neise, D [TU Dortmund University, Otto-Hahn-Str. 4, 44227 Dortmund (Germany); Bretz, T; Mannheim, K [University of Wuerzburg Am Hubland, 97074 Wuerzburg (Germany)], E-mail: qweitzel@phys.ethz.ch (and others)

    2009-10-15

    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.

  6. Optimization of a guard ring structure in Geiger-mode avalanche photodiodes fabricated at National NanoFab Center

    Science.gov (United States)

    Lim, K. T.; Kim, H.; Cho, M.; Kim, Y.; Kim, C.; Kim, M.; Lee, D.; Kang, D.; Yoo, H.; Park, K.; Sul, W. S.; Cho, G.

    2016-01-01

    A typical Geiger-mode avalanche photodiode (G-APD) contains a guard ring that protects the structure from having an edge breakdown due to the lowering of electric fields at junction curvatures. In this contribution, G-APDs with a virtual guard ring (vGR) merged with n-type diffused guard ring (nGR) in various sizes were studied to find the optimal design for G-APDs fabricated at National NanoFab Center (NNFC) . The sensors were fabricated via a customized CMOS process with a micro-cell size of 65× 65 μm2 on a 200 mm p-type epitaxial layer wafer. I-V characteristic curves for proposed structures were measured on a wafer-level with an auto probing system and plotted together to compare their performance. A vGR width of 1.5 μm and a nGR width of 1.5 μm with an overlapping between vGR and nGR of 1.5 μm showed the lowest leakage current before the breakdown voltage while suppressing the edge breakdown. Furthermore, the current level of the lowest-leakage-current structure was as low as that of only vGR with a width of 2.0 μm, indicating that the structure is also area efficient. Based on these results, the design with vGR, nGR, and OL with width of 1.5 μm is determined to be the optimal structure for G-APDs fabricated at NNFC.

  7. A test beam setup for the characterization of the Geiger-mode avalanche photodiode technology for particle tracking

    Energy Technology Data Exchange (ETDEWEB)

    Vilella, E., E-mail: evilella@el.ub.es [Department of Electronics, University of Barcelona (UB), C/Marti i Franques 1, 08028 Barcelona (Spain); Alonso, O. [Department of Electronics, University of Barcelona (UB), C/Marti i Franques 1, 08028 Barcelona (Spain); Trenado, J. [Department of Structure and Constituents of Matter, University of Barcelona (UB), C/Marti i Franques 1, 08028 Barcelona (Spain); Vila, A.; Casanova, R. [Department of Electronics, University of Barcelona (UB), C/Marti i Franques 1, 08028 Barcelona (Spain); Vos, M. [Instituto de Fisica Corpuscular (IFIC), C/Catedratico Jose Beltran 2, 46980 Paterna (Spain); Garrido, L. [Department of Structure and Constituents of Matter, University of Barcelona (UB), C/Marti i Franques 1, 08028 Barcelona (Spain); Dieguez, A. [Department of Electronics, University of Barcelona (UB), C/Marti i Franques 1, 08028 Barcelona (Spain)

    2012-12-01

    It is well known that avalanche photodiodes operated in the Geiger mode above the breakdown voltage offer a virtually infinite gain and time accuracy in the picosecond range that can be used for single photon detection. However, their performance in particle detection still remains unexplored. In this contribution, we are going to expose different steps that we have taken in order to prove the efficiency of the Geiger mode avalanche photodiodes in the aforementioned field. In particular, we will present a setup for the characterization of these sensors in a test beam. The expected results of the test beam at DESY and CERN have been simulated with Geant4 and will also be exposed. -- Highlights: Black-Right-Pointing-Pointer A Setup for characterization of the GAPD technology in a test beam is presented. Black-Right-Pointing-Pointer Two test beams at DESY (6 GeV) and CERN (120 GeV) are already planned at current time. Black-Right-Pointing-Pointer A GAPD array has been designed and fabricated to fit the test beam requirements. Black-Right-Pointing-Pointer We have prepared a test beam setup to minimize the particle multiscattering. Black-Right-Pointing-Pointer The Expected results at DESY and CERN have been simulated with Geant4.

  8. Conception d'un circuit d'etouffement pour photodiodes a avalanche en mode geiger pour integration heterogene 3d

    Science.gov (United States)

    Boisvert, Alexandre

    Le Groupe de Recherche en Appareillage Medical de Sherbrooke (GRAMS) travaille actuellement sur un programme de recherche portant sur des photodiodes a avalanche mono-photoniques (PAMP) operees en mode Geiger en vue d'une application a la tomographie d'emission par positrons (TEP). Pour operer dans ce mode; la PAMP, ou SPAD selon l'acronyme anglais (Single Photon Avalanche Diode), requiert un circuit d'etouffement (CE) pour, d'une part, arreter l'avalanche pouvant causer sa destruction et, d'autre part. la reinitialiser en mode d'attente d'un nouveau photon. Le role de ce CE comprend egalement une electronique de communication vers les etages de traitement avance de signaux. La performance temporelle optimale du CE est realisee lorsqu'il est juxtapose a la PAMP. Cependant, cela entraine une reduction de la surface photosensible ; un element crucial en imagerie. L'integration 3D, a base d'interconnexions verticales, offre une solution elegante et performante a cette problematique par l'empilement de circuits integres possedant differentes fonctions (PAMP, CE et traitement avance de signaux). Dans l'approche proposee, des circuits d'etouffement de 50 pm x 50 pm realises sur une technologie CMOS 130 mn 3D Tezzaron, contenant chacun 112 transistors, sont matrices afin de correspondre a une matrice de PAMP localisee sur une couche electronique superieure. Chaque circuit d'etouffement possede une gigue temporelle de 7,47 ps RMS selon des simulations faites avec le logiciel Cadence. Le CE a la flexibilite d'ajuster les temps d'etouffement et de recharge pour la PAMP tout en presentant une faible consommation de puissance (~ 0,33 mW a 33 Mcps). La conception du PAMP necessite de supporter des tensions superieures aux 3,3 V de la technologie. Pour repondre a ce probleme, des transistors a drain etendu (DEMOS) ont ete realises. En raison de retards de production par Ies fabricants, les circuits n'ont pu etre testes physiquement par des mesures. Les resultats de ce memoire

  9. Ultra-fast time-correlated single photon counting avalanche photodiodes for time-domain non-contact fluorescence diffuse optical tomography

    Science.gov (United States)

    Robichaud, Vincent; Lapointe, Éric; Bérubé-Lauzière, Yves

    2007-06-01

    Recent advances in the design and fabrication of avalanche photodiodes (APDs) and quenching circuits for timecorrelated single photon counting (TCSPC) have made available detectors with timing resolutions comparable to microchannel plate photomultiplier tubes (MCP-PMTs). The latter, were until recently the best TCSPC detectors in terms of temporal resolution (standard electronics fabrication processes in a near future. This will contribute to further decrease their price and ease their integration in complex multi-channel detection systems, as required in diuse optical imaging (DOI) and tomography (DOT). We present, to our knowledge for the first time, results which demonstrate that, despite their small sensitive area, TCSPC APDs can be used in time-domain (TD) DOT and more generally in TD DOI. With appropriate optical design of the detection channel, our experiments show that it is possible to obtain comparable measurements with APDs as with PMTs.

  10. Epitaxial growth of HgCdTe 1.55-um avalanche photodiodes by molecular beam epitaxy

    Science.gov (United States)

    de Lyon, Terence J.; Baumgratz, B.; Chapman, G. R.; Gordon, E.; Hunter, Andrew T.; Jack, Michael D.; Jensen, John E.; Johnson, W.; Johs, Blaine D.; Kosai, K.; Larsen, W.; Olson, G. L.; Sen, M.; Walker, B.

    1999-04-01

    Separate absorption and multiplication avalanche photodiode (SAM-APD) device structures, operating in the 1.1 - 1.6 micrometer spectral range, have been fabricated in the HgCdTe material system by molecular-beam epitaxy. These HgCdTe device structures, which offer an alternative technology to existing III-V APD detectors, were grown on CdZnTe(211)B substrates using CdTe, Te, and Hg sources with in situ In and As doping. The alloy composition of the HgCdTe layers was adjusted to achieve both efficient absorption of IR radiation in the 1.1 - 1.6 micrometer spectral range and low excess-noise avalanche multiplication. To achieve resonant enhancement of hole impact ionization from the split-off valence band, the Hg(subscript 1-x)Cd(subscript x)Te alloy composition in the gain region of the device, x equals 0.73, was chosen to achieve equality between the bandgap energy and spin-orbit splitting. The appropriate value of this alloy composition was determined from analysis of the 300 K bandgap and spin-orbit splitting energies of a set of calibration layers, using a combination of IR transmission and spectroscopic ellipsometry measurements. MBE-grown APD epitaxial wafers were processed into passivated mesa-type discrete device structures and diode mini-arrays using conventional HgCdTe process technology. Device spectral response, dark current density, and avalanche gain measurements were performed on discrete diodes and diode mini- arrays on the processed wafers. Avalanche gains in the range of 30 - 40 at reverse bias of 85 - 90 V and array-median dark current density below 2 X 10(superscript -4) A/cm(superscript 2) at 40 V reverse bias have been demonstrated.

  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. Active quench and reset integrated circuit with novel hold-off time control logic for Geiger-mode avalanche photodiodes.

    Science.gov (United States)

    Deng, Shijie; Morrison, Alan P

    2012-09-15

    This Letter presents an active quench-and-reset circuit for Geiger-mode avalanche photodiodes (GM-APDs). The integrated circuit was fabricated using a conventional 0.35 μm complementary metal oxide semiconductor process. Experimental results show that the circuit is capable of linearly setting the hold-off time from several nanoseconds to microseconds with a resolution of 6.5 ns. This allows the selection of the optimal afterpulse-free hold-off time for the GM-APD via external digital inputs or additional signal processing circuitry. Moreover, this circuit resets the APD automatically following the end of the hold-off period, thus simplifying the control for the end user. Results also show that a minimum dead time of 28.4 ns is achieved, demonstrating a saturated photon-counting rate of 35.2 Mcounts/s.

  13. Model of turn-on characteristics of InP-based Geiger-mode avalanche photodiodes suitable for circuit simulations

    Science.gov (United States)

    Jordy, George; Donnelly, Joseph

    2015-05-01

    A model for the turn-on characteristics of separate-absorber-multiplier InP-based Geiger-mode Avalanche Photodiodes (APDs) has been developed. Verilog-A was used to implement the model in a manner that can be incorporated into circuit simulations. Rather than using SPICE elements to mimic the voltage and current characteristics of the APD, Verilog-A can represent the first order nonlinear differential equations that govern the avalanche current of the APD. This continuous time representation is fundamentally different than the piecewise linear characteristics of other models. The model is based on a driving term for the differential current, which is given by the voltage overbias minus the voltage drop across the device's space-charge resistance RSC. This drop is primarily due to electrons transiting the separate absorber. RSC starts off high and decreases with time as the initial breakdown filament spreads laterally to fill the APD. With constant bias voltage, the initial current grows exponentially until space charge effects reduce the driving function. With increasing current the driving term eventually goes to zero and the APD current saturates. On the other hand, if the APD is biased with a capacitor, the driving term becomes negative as the capacitor discharges, reducing the current and driving the voltage below breakdown. The model parameters depend on device design and are obtained from fitting the model to Monte-Carlo turn-on simulations that include lateral spreading of the carriers of the relevant structure. The Monte-Carlo simulations also provide information on the probability of avalanche, and jitter due to where the photon is absorbed in the APD.

  14. First Avalanche-photodiode camera test (FACT): A novel camera using G-APDs for the observation of very high-energy {gamma}-rays with Cherenkov telescopes

    Energy Technology Data Exchange (ETDEWEB)

    Braun, I. [ETH Zurich, CH-8093 Zurich (Switzerland); Commichau, S.C. [ETH Zurich, CH-8093 Zurich (Switzerland)], E-mail: commichau@phys.ethz.ch; Rissi, M. [ETH Zurich, CH-8093 Zurich (Switzerland); Backes, M. [Dortmund University of Technology, D-44221 Dortmund (Germany); Biland, A. [ETH Zurich, CH-8093 Zurich (Switzerland); Bretz, T. [University of Wuerzburg, D-97074 Wuerzburg (Germany); Britvitch, I.; Commichau, V.; Gunten, H. von; Hildebrand, D.; Horisberger, U.; Kranich, D. [ETH Zurich, CH-8093 Zurich (Switzerland); Lorenz, E. [ETH Zurich, CH-8093 Zurich (Switzerland); Max-Planck-Institut fuer Physik, D-80805 Muenchen (Germany); Lustermann, W. [ETH Zurich, CH-8093 Zurich (Switzerland); Mannheim, K. [University of Wuerzburg, D-97074 Wuerzburg (Germany); Neise, D. [Dortmund University of Technology, D-44221 Dortmund (Germany); Pauss, F. [ETH Zurich, CH-8093 Zurich (Switzerland); Pohl, M. [University of Geneva, CH-1211 Geneva (Switzerland); Renker, D. [Paul Scherrer Institut (PSI) Villigen, CH-5232 Villigen (Switzerland); Rhode, W. [Dortmund University of Technology, D-44221 Dortmund (Germany)] (and others)

    2009-10-21

    We present a project for a novel camera using Geiger-mode Avalanche Photodiodes (G-APDs), to be installed in a small telescope (former HEGRA CT3) on the MAGIC site in La Palma (Canary Island, Spain). This novel type of semiconductor photon detector provides several superior features compared to conventional photomultiplier tubes (PMTs). The most promising one is a much higher Photon Detection Efficiency.

  15. 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.

  16. Readout circuitry for continuous high-rate photon detection with arrays of InP Geiger-mode avalanche photodiodes

    Science.gov (United States)

    Frechette, Jonathan; Grossmann, Peter J.; Busacker, David E.; Jordy, George J.; Duerr, Erik K.; McIntosh, K. Alexander; Oakley, Douglas C.; Bailey, Robert J.; Ruff, Albert C.; Brattain, Michael A.; Funk, Joseph E.; MacDonald, Jason G.; Verghese, Simon

    2012-06-01

    An asynchronous readout integrated circuit (ROIC) has been developed for hybridization to a 32x32 array of single-photon sensitive avalanche photodiodes (APDs). The asynchronous ROIC is capable of simultaneous detection and readout of photon times of arrival, with no array blind time. Each pixel in the array is independently operated by a finite state machine that actively quenches an APD upon a photon detection event, and re-biases the device into Geiger mode after a programmable hold-off time. While an individual APD is in hold-off mode, other elements in the array are biased and available to detect photons. This approach enables high pixel refresh frequency (PRF), making the device suitable for applications including optical communications and frequency-agile ladar. A built-in electronic shutter that de-biases the whole array allows the detector to operate in a gated mode or allows for detection to be temporarily disabled. On-chip data reduction reduces the high bandwidth requirements of simultaneous detection and readout. Additional features include programmable single-pixel disable, region of interest processing, and programmable output data rates. State-based on-chip clock gating reduces overall power draw. ROIC operation has been demonstrated with hybridized InP APDs sensitive to 1.06-μm and 1.55-μm wavelength, and fully packaged focal plane arrays (FPAs) have been assembled and characterized.

  17. 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.

  18. Monolithically integrated avalanche photodiode receiver in 0.35 μm bipolar complementary metal oxide semiconductor

    Science.gov (United States)

    Jukić, Tomislav; Steindl, Bernhard; Enne, Reinhard; Zimmermann, Horst

    2015-11-01

    We present the first optoelectronic integrated bipolar complementary metal oxide semiconductor (BiCMOS) receiver chip with an avalanche photodiode (APD). A large 200-μm-diameter APD connected to a high-speed transimpedance amplifier designed for a 2-Gbps optical wireless communication system is proposed. The complete chip was realized in a 0.35-μm silicon BiCMOS technology. Due to the thick intrinsic zone and multiplication gain, the responsivity of the APD reaches a value of up to 120 A/W for a wavelength of 675 nm. Furthermore, the capacitance of the APD is <500 fF for reverse bias voltages above 18 V. The receiver has a supply voltage of 3.3 V with a current consumption of 76 mA. The delivered 50-Ω single-ended output swing is 550 mVpp and the overall transimpedance is 260 kΩ with 1.02-GHz bandwidth. The achieved data rate is 2 Gbps with a sensitivity of -30.3 dBm at a bit error rate <10-9.

  19. Design and performance testing of an avalanche photodiode receiver with multiplication gain control algorithm for intersatellite laser communication

    Science.gov (United States)

    Yu, Xiaonan; Tong, Shoufeng; Dong, Yan; Song, Yansong; Hao, Shicong; Lu, Jing

    2016-06-01

    An avalanche photodiode (APD) receiver for intersatellite laser communication links is proposed and its performance is experimentally demonstrated. In the proposed system, a series of analog circuits are used not only to adjust the temperature and control the bias voltage but also to monitor the current and recover the clock from the communication data. In addition, the temperature compensation and multiplication gain control algorithm are embedded in the microcontroller to improve the performance of the receiver. As shown in the experiment, with the change of communication rate from 10 to 2000 Mbps, the detection sensitivity of the APD receiver varies from -47 to -34 dBm. Moreover, due to the existence of the multiplication gain control algorithm, the dynamic range of the APD receiver is effectively improved, while the dynamic range at 10, 100, and 1000 Mbps is 38.7, 37.7, and 32.8 dB, respectively. As a result, the experimental results agree well with the theoretical predictions, and the receiver will improve the flexibility of the intersatellite links without increasing the cost.

  20. Temporal dependence of transient dark counts in an avalanche photodiode: A solution for power-law behavior of afterpulsing

    Science.gov (United States)

    Akiba, M.; Tsujino, K.

    2016-08-01

    This paper offers a theoretical explanation of the temperature and temporal dependencies of transient dark count rates (DCRs) measured for a linear-mode silicon avalanche photodiode (APD) and the dependencies of afterpulsing that were measured in Geiger-mode Si and InGaAs/InP APDs. The temporal dependencies exhibit power-law behavior, at least to some extent. For the transient DCR, the value of the DCR for a given time period increases with decreases in temperature, while the power-law behavior remains unchanged. The transient DCR is attributed to electron emissions from traps in the multiplication layer of the APD with a high electric field, and its temporal dependence is explained by a continuous change in the electron emission rate as a function of the electric field strength. The electron emission rate is calculated using a quantum model for phonon-assisted tunnel emission. We applied the theory to the temporal dependence of afterpulsing that was measured for Si and InGaAs/InP APDs. The power-law temporal dependence is attributed to the power-law function of the electron emission rate from the traps as a function of their position across the p-n junction of the APD. Deviations from the power-law temporal dependence can be derived from the upper and lower limits of the electric field strength.

  1. Characterization of a CsI(Tl) array coupled to avalanche photodiodes for the Barrel of the CALIFA calorimeter at the NEPTUN tagged gamma beam facility

    Science.gov (United States)

    Gascón, M.; Schnorrenberger, L.; Pietras, B.; Álvarez-Pol, H.; Cortina-Gil, D.; Díaz Fernández, P.; Duran, I.; Glorius, J.; González, D.; Perez-Loureiro, D.; Pietralla, N.; Savran, D.; Sonnabend, K.

    2013-10-01

    Among the variety of crystal calorimeters recently designed for several physics facilities, CALIFA (CALorimeter for In-Flight emitted gAmmas and light-charged particles) has especially demanding requirements since it must perform within a very complicated energy domain (gamma-ray energies from 0.1 to 20 MeV and up to 300 MeV protons). As part of the R&D program for the Barrel section of CALIFA, a reduced geometry prototype was constructed. This prototype consisted of a 3 × 5 array of CsI(Tl) crystals of varying dimensions, coupled to large area avalanche photodiodes. Here reported are the details regarding the construction of the prototype and the experimental results obtained at the NEPTUN tagged gamma beam facility, reconstructing gamma energies up to 10 MeV. Dedicated Monte Carlo simulations of the setup were also performed, enabling a deeper understanding of the experimental data. The experimental results demonstrate the effectiveness of the reconstruction method and helped to establish the most suitable crystal geometry to be employed within the forthcoming calorimeter.

  2. Time-resolved non-contact fluorescence diffuse optical tomography measurements with ultra-fast time-correlated single photon counting avalanche photodiodes

    Science.gov (United States)

    Bérubé-Lauzière, Yves; Robichaud, Vincent; Lapointe, Éric

    2007-07-01

    The design and fabrication of time-correlated single photon counting (TCSPC) avalanche photodiodes (APDs) and associated quenching circuits have made significant progresses in recent years. APDs with temporal resolutions comparable to microchannel plate photomultiplier tubes (MCP-PMTs) are now available. MCP-PMTs were until these progresses the best TCSPC detectors with timing resolutions down to 30ps. APDs can now achieve these resolutions at a fraction of the cost. Work is under way to make the manufacturing of TCSPC APDs compatible with standard electronics fabrication practices. This should allow to further reduce their cost and render them easier to integrate in complex multi-channel TCSPC electronics, as needed in diffuse optical tomography (DOT) systems. Even if their sensitive area is much smaller than that of the ubiquitous PMT used in TCSPC, we show that with appropriate selection of optical components, TCSPC APDs can be used in time-domain DOT. To support this, we present experimental data and calculations clearly demonstrating that comparable measurements can be obtained with APDs and PMTs. We are, to our knowledge, the first group using APDs in TD DOT, in particular in non-contact TD fluorescence DOT.

  3. Participation to the study of the electromagnetic calorimeter calibration for the CMS experiment and to the study of avalanche photodiodes; Participation a l'etude de la calibration du calorimetre electromagnetique de l'experience CMS et a l'etude de photodiodes a avalanche

    Energy Technology Data Exchange (ETDEWEB)

    Da Ponte Puill, V

    1999-12-13

    The electromagnetic calorimeter CMS (Compact Muon Solenoid) has been chosen to study the Higgs boson production. This calorimeter will be constituted of more than 80000 lead tungstate scintillating crystals radiation resistant. Photodiodes have been especially optimized to detect the scintillating light of these crystals: avalanche photodiodes (APD). This thesis includes two separate parts. A first part deals with the APD submitted to high rate of radiations and tested in the Ulysse reactor of the Cea. The second part deals with the calorimeter calibration. (A.L.B.)

  4. Optimization and application of cooled avalanche photodiodes for spectroscopic fluctuation measurements with ultra-fast charge exchange recombination spectroscopy

    Science.gov (United States)

    Truong, D. D.; Fonck, R. J.; McKee, G. R.

    2016-11-01

    The Ultra-Fast Charge Exchange Recombination Spectroscopy (UF-CHERS) diagnostic is a highly specialized spectroscopic instrument with 2 spatial channels consisting of 8 spectral channels each and a resolution of ˜0.25 nm deployed at DIII-D to measure turbulent ion temperature fluctuations. Charge exchange emissions are obtained between 528 and 530 nm with 1 μs time resolution to study plasma instabilities. A primary challenge of extracting fluctuation measurements from raw UF-CHERS signals is photon and electronic noise. In order to reduce dark current, the Avalanche Photodiode (APD) detectors are thermo-electrically cooled. State-of-the-art components are used for the signal amplifiers and conditioners to minimize electronic noise. Due to the low incident photon power (≤1 nW), APDs with a gain of up to 300 are used to optimize the signal to noise ratio. Maximizing the APDs' gain while minimizing the excess noise factor (ENF) is essential since the total noise of the diagnostic sets a floor for the minimum level of detectable broadband fluctuations. The APDs' gain should be high enough that photon noise dominates electronic noise, but not excessive so that the ENF overwhelms plasma fluctuations. A new generation of cooled APDs and optimized preamplifiers exhibits significantly enhanced signal-to-noise compared to a previous generation. Experiments at DIII-D have allowed for characterization and optimization of the ENF vs. gain. A gain of ˜100 at 1700 V is found to be near optimal for most plasma conditions. Ion temperature and toroidal velocity fluctuations due to the edge harmonic oscillation in quiescent H-mode plasmas are presented to demonstrate UF-CHERS' capabilities.

  5. In Orbit Performance of Si Avalanche Photodiode Single Photon Counting Modules in the Geoscience Laser Altimeter System on ICESat

    Science.gov (United States)

    Sun, X.; Jester, P. L.; Palm, S. P.; Abshire, J. B.; Spinhime, J. D.; Krainak, M. A.

    2006-01-01

    Si avalanche photodiode (APD) single photon counting modules (SPCMs) are used in the Geoscience Laser Altimeter System (GLAS) on Ice, Cloud, anti land Elevation Satellite (ICESat), currently in orbit measuring Earth surface elevation and atmosphere backscattering. These SPCMs are used to measure cloud and aerosol backscatterings to the GLAS laser light at 532-nm wavelength with 60-70% quantum efficiencies and up to 15 millions/s maximum count rates. The performance of the SPCMs has been closely monitored since ICESat launch on January 12, 2003. There has been no measurable change in the quantum efficiency, as indicated by the average photon count rates in response to the background light from the sunlit earth. The linearity and the afterpulsing seen from the cloud and surface backscatterings profiles have been the same as those during ground testing. The detector dark count rates monitored while the spacecraft was in the dark side of the globe have increased almost linearly at about 60 counts/s per day due to space radiation damage. The radiation damage appeared to be independent of the device temperature and power states. There was also an abrupt increase in radiation damage during the solar storm in 28-30 October 2003. The observed radiation damage is a factor of two to three lower than the expected and sufficiently low to provide useful atmosphere backscattering measurements through the end of the ICESat mission. To date, these SPCMs have been in orbit for more than three years. The accumulated operating time to date has reached 290 days (7000 hours). These SPCMs have provided unprecedented receiver sensitivity and dynamic range in ICESat atmosphere backscattering measurements.

  6. Linear mode photon counting from visible to MWIR with HgCdTe avalanche photodiode focal plane arrays

    Science.gov (United States)

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

    2015-05-01

    Results of characterization data on linear mode photon counting (LMPC) HgCdTe electron-initiated avalanche photodiode (e-APD)focal plane arrays (FPA) are presented that reveal an improved understanding and the growing maturity of the technology. The first successful 2x8 LMPC FPA was fabricated in 2010 [1]. Since then a process validation lot of 2x8 arrays was fabricated. Five arrays from this lot were characterized that replicated the previous 2x8 LMPC array performance. In addition, it was unambiguously verified that readout integrated circuit (ROIC) glow was responsible for most of the false event rate (FER) of the 2010 array. The application of a single layer metal blocking layer between the ROIC and the detector array and optimization of the ROIC biases reduced the FER by an order of magnitude. Photon detection efficiencies (PDEs) of greater than 50% were routinely demonstrated across 5 arrays, with one array reaching a PDE of 70%. High resolution pixel-surface spot scans were performed and the junction diameters of the diodes were measured. The junction diameter was decreased from 31 μm to 25 μm resulting in a 2x increase in E-APD gain from 470 on the 2010 array to 1100 on one of the 2013 FPAs. Mean single photon signal to noise ratios of >12 were demonstrated at excess noise factors of 1.2-1.3. NASA Goddard Space Flight Center (GSFC) performed measurements on the delivered FPA that verified the PDE and FER data.

  7. Restraint of range walk error in a Geiger-mode avalanche photodiode lidar to acquire high-precision depth and intensity information.

    Science.gov (United States)

    Xu, Lu; Zhang, Yu; Zhang, Yong; Yang, Chenghua; Yang, Xu; Zhao, Yuan

    2016-03-01

    There exists a range walk error in a Geiger-mode avalanche photodiode (Gm-APD) lidar because of the fluctuation in the number of signal photoelectrons. To restrain this range walk error, we propose a new returning-wave signal processing technique based on the Poisson probability response model and the Gaussian functions fitting method. High-precision depth and intensity information of the target at the distance of 5 m is obtained by a Gm-APD lidar using a 6 ns wide pulsed laser. The experiment results show that the range and intensity precisions are 1.2 cm and 0.015 photoelectrons, respectively. PMID:26974630

  8. Development of high performance Avalanche Photodiodes and dedicated analog systems for HXI/SGD detectors onboard the Astro-H mission

    International Nuclear Information System (INIS)

    Hard X-ray Imager and Soft Gamma-ray Detector are being developed as onboard instruments for the Astro-H mission, which is scheduled for launch in 2014. In both detectors, BGO scintillators play key roles in achieving high sensitivity in low Earth orbit (LEO), by generating active veto signals to reject cosmic-ray events and gamma-ray backgrounds from radio-activated detector materials. In order to maximize background rejection power, it is also important to minimize the energy threshold of this shield. As a readout sensor of weak scintillation light from a number of BGO crystals in a complicated detector system, high performance, reverse-type Avalanche Photodiodes (APDs), with an effective area of 10×10mm2 are being employed, instead of bulky photomultiplier tubes (PMTs).Another advantage of using APDs is their low power consumption, although the relatively low gain of APDs (compared to conventional PMTs) requires dedicated analog circuits for noise suppression. In this paper, we report on the development and performance of APD detectors specifically designed for the Astro-H mission. In addition to APD performance, various environmental tests, including radiation hardness and qualification thermal cycling, will be described in detail. Moreover, a dedicated charge sensitive amplifier and analog filters are newly developed and tested here to optimize the performance of APDs to activate fast veto signals within a few μs from the BGO trigger. We will also report on overall performance testing of a prototype BGO detector system that mimics the data acquisition system onboard Astro-H.

  9. Next-Generation Active-Pixel Sensor Devices With CMOS-avalanche photodiodes

    International Nuclear Information System (INIS)

    Modern high-energy physics experiments that explore the fundamental properties of matter rely on large, sophisticated instruments for tracking particle decay events with large detector arrays. The performance of these instruments is limited by the available detector technology. Future progress depends on breakthroughs in the sensitivity, speed and signal-to-noise performance of the detectors. Phase I research successfully developed and tested many different pixel designs. Several different pixel and circuit applications were designed based on previously manufactured chips, but with the vertex detector application in mind. We have characterized the noise performance and sensitivity of CMOS APD pixels using several different types of radiation and selected the best designs. Phase II will were are concerned with transforming our test structures into fully functional detector elements with the appropriate processing and readout electronics integrated with large arrays of pixels. We investigated methods to increase the active area and reduce the noise while implementing an event-driven readout scheme to drastically increase the readout speed and simplify the data stream

  10. 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.

  11. MBE growth of HgCdTe avalanche photodiode structures for low-noise 1.55 μm photodetection

    Science.gov (United States)

    de Lyon, T. J.; Baumgratz, B.; Chapman, G.; Gordon, E.; Hunter, A. T.; Jack, M.; Jensen, J. E.; Johnson, W.; Johs, B.; Kosai, K.; Larsen, W.; Olson, G. L.; Sen, M.; Walker, B.; Wu, O. K.

    1999-05-01

    Molecular-beam epitaxy (MBE) has been utilized to fabricate HgCdTe heterostructure separate absorption and multiplication avalanche photodiodes (SAM-APD) sensitive to infrared radiation in the 1.1-1.6 μm spectral range, as an alternative technology to existing III-V APD detectors. Device structures were grown on CdZnTe(211)B substrates using CdTe, Te, and Hg sources with in situ In and As doping. The composition of the HgCdTe alloy layers was adjusted to achieve both efficient absorption of IR radiation in the 1.1-1.6 μm spectral range and low excess-noise avalanche multiplication. The Hg 1- xCd xTe alloy composition in the gain region of the device, x=0.73, was selected to achieve equality between the bandgap energy and spin-orbit splitting to resonantly enhance the impact ionization of holes in the split-off valence band. The appropriate value of this alloy composition was determined from analysis of the 300 K bandgap and spin-orbit splitting energies of a set of calibration layers, using a combination of IR transmission and spectroscopic ellipsometry measurements. MBE-grown APD epitaxial wafers were processed into passivated mesa-type discrete device structures and diode mini-arrays using conventional HgCdTe process technology. Device spectral response, dark current density, and avalanche gain measurements were performed on the processed wafers. Avalanche gains in the range of 30-40 at reverse bias of 85-90 V and array-median dark current density below 2×10 -4 A/cm 2 at 40 V reverse bias have been demonstrated.

  12. 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.

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

    International Nuclear Information System (INIS)

    In this work, the direct-bandgap compound semiconductor materials are irradiated by α particles emitted from 241Am 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 PbI2 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)

  14. Count rate studies of a box-shaped PET breast imaging system comprised of position sensitive avalanche photodiodes utilizing monte carlo simulation.

    Science.gov (United States)

    Foudray, Angela M K; Habte, Frezghi; Chinn, Garry; Zhang, Jin; Levin, Craig S

    2006-01-01

    We are investigating a high-sensitivity, high-resolution positron emission tomography (PET) system for clinical use in the detection, diagnosis and staging of breast cancer. Using conventional figures of merit, design parameters were evaluated for count rate performance, module dead time, and construction complexity. The detector system modeled comprises extremely thin position-sensitive avalanche photodiodes coupled to lutetium oxy-orthosilicate scintillation crystals. Previous investigations of detector geometries with Monte Carlo indicated that one of the largest impacts on sensitivity is local scintillation crystal density when considering systems having the same average scintillation crystal densities (same crystal packing fraction and system solid-angle coverage). Our results show the system has very good scatter and randoms rejection at clinical activity ranges ( approximately 200 muCi). PMID:17645997

  15. Development of long-wavelength avalanche photodiodes and vertical-cavity lasers for epitaxial integration as a vertical-cavity photon number amplifier

    Science.gov (United States)

    Huntington, Andrew Sumika

    The goal of this research was to develop technology for building a vertical-geometry photon number amplifier (vertical PNA) that operates at a wavelength in the low-absorption window for optical fibers near 1.55 mum. An optical amplifier of this design would provide electrically-tappable low-noise polarization-independent optical amplification of laser pulses and serve as a stepping stone toward development of a tunable amplifying wavelength converter. The vertical PNA design consists of a multiple active region (MAR) VCSEL integrated with an avalanche photodiode of the separate absorption, charge, and multiplication layer design (SACM APD): the VCSEL is intended to operate continuous wave (CW), modulated by the APD. Both components were selected for their high gain: in excess of 10 electrons out per photon in for the APD, and slightly more than 1 photon out per electron in for the MAR VCSEL under ideal circumstances. In working toward the vertical PNA, significant technical challenges were addressed: (1) Development of a long-wavelength MAR VCSEL capable of high-temperature CW operation. Although this goal was never achieved, efforts directed to this end resulted in an investigation of basic material science issues that are vital to future improvements of the device. Better DBR and active region designs were developed, the overall thermal impedance of the structure was reduced significantly, a rudimentary optical aperture compatible with InP-based materials was tested, and loss estimates for the device were put on solid ground. (2) Development of a low-noise SACM APD capable of modulating the MAR VCSEL at high speed. Here the vital relationships between growth conditions, material quality, and APD performance were established. Other achievements include demonstration of highly uniform arrays of these devices, extremely low-noise operation, and the largest area long-wavelength APDs ever reported. (3) Successful demonstration of the epitaxial integration of these

  16. Negative feedback avalanche diode

    Science.gov (United States)

    Itzler, Mark Allen (Inventor)

    2010-01-01

    A single-photon avalanche detector is disclosed that is operable at wavelengths greater than 1000 nm and at operating speeds greater than 10 MHz. The single-photon avalanche detector comprises a thin-film resistor and avalanche photodiode that are monolithically integrated such that little or no additional capacitance is associated with the addition of the resistor.

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

    Science.gov (United States)

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

    2010-09-01

    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 6×6×4 array of 1.46×1.46 mm 2×4.5 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.

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

    Science.gov (United States)

    Xu, Fan; Wang, Yuanqing; Li, Fenfang

    2016-03-01

    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.

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

    Science.gov (United States)

    Xu, Fan; Wang, Yuanqing; Li, Fenfang

    2016-03-01

    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. PMID:27036763

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

    Science.gov (United States)

    Xu, Fan; Wang, Yuanqing; Li, Fenfang

    2016-03-01

    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.

  1. 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.

  2. A liquid-helium cooled large-area silicon PIN photodiode X-ray detector

    International Nuclear Information System (INIS)

    An X-ray detector using a liquid-helium cooled large-area silicon PIN photodiode has been developed along with a tailor-made charge sensitive preamplifier whose first-stage JFET has been cooled. The operating temperature of the JFET has been varied separately and optimized. The X- and γ-ray energy spectra for an 241Am source have been measured with the photodiode operated at 13 K. An energy resolution of 1.60 keV (FWHM) has been obtained for 60-keV γ rays and 1.30 keV (FWHM) for the pulser. The energy threshold could be set as low as 3 keV. It has been shown that a silicon PIN photodiode serves as a low-cost excellent X-ray detector which covers a large area at 13 K. (orig.)

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

    International Nuclear Information System (INIS)

    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)

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

    International Nuclear Information System (INIS)

    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)

  5. 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.

  6. Development of the HgCdTe Avalanche Photodiode Detectors and the Improvement in the CO2 Lidar Performance for the ASCENDS Mission

    Science.gov (United States)

    Sun, X.; Abshire, J. B.; Chen, J. R.; Ramanathan, A. K.; Mao, J.

    2015-12-01

    NASA Goddard Space Flight Center (GSFC) is developing the CO2 lidar as a candidate for the NASA's planned ASCENDS mission under the support of Earth Science Technology Office (ESTO) IIP and ATI-QRS programs. A new type of HgCdTe avalanche photodiode (APD) detector has been developed by the DRS Technologies under the IIP program. The new detectors achieved >70% quantum efficiency, including the effect of the fill factor, over the spectral range from 0.4 to 4.3 μm, which significantly improves the receiver performance of our CO2 lidar and enabled other remote sending measurements. The HgCdTe APD arrays have 80 μm square pixels in a 4x4 array along with a bank of 16 preamplifiers on the same chip carrier. Test results at both DRS and GSFC showed the HgCdTe APD array has achieved, an APD gain of 500-1000, 8-10 MHz electrical bandwidth, and an average noise equivalent power (NEP) of performance for at least a year. We have also updated the performance analysis of a space-based version of our CO2 lidar with the new HgCdTe APD detector. For the retrievals, a least-square-error method is used to fit the measured transmittances to a predetermined line shape function using 8 to 16 sampling wavelengths. The error in the derived total optical depth and the CO2 mixing ratio are estimated via the standard error propagation method. The error in the resultant CO2 mixing ratio is calculated as a function of the received optical signal power, including the effects of the laser energy, receiver telescope size, and solar background radiation noise. The presentation will give more details about the detector and its impact on our CO2 lidar for the ASCENDS mission.

  7. Different Avalanche Behaviors in Different Specific Areas of a System Based on Neural Networks

    Institute of Scientific and Technical Information of China (English)

    ZHAO Xiao-Wei; CHEN Tian-Lun

    2003-01-01

    Based on the standard self-organizing map (SOM) neural network model and an integrate-and-fire mecha-nism, we introduce a kind of coupled map lattice system to investigate scale-invariance behavior in the activity of modelneural populations. We find power-law distribution behavior of avalanche size in our model. But more importantly, wefind there are different avalanche distribution behaviors in different specific areas of our system, which are formed by thetopological learning process of the SOM net.

  8. Influence of temperature and bias voltage on the performance of a high resolution PET detector built with position sensitive avalanche photodiodes

    Science.gov (United States)

    Vandenbroucke, A.; McLaughlin, T. J.; Levin, C. S.

    2012-08-01

    We evaluate the performance of an 8 × 8 array of 0.9 × 0.9 × 1 mm3 cerium doped lutetium oxyothosilicate (LSO) crystals coupled to a position sensitive avalanche photodiode (PSAPD) as a function of bias voltage and temperature. We use this detector to develop a general methodology to optimize bias voltage, temperature, and gain for PET detectors using semiconductor photodetectors. This detector module will be used in a novel high resolution positron emission tomography (PET) camera dedicated to breast imaging under construction in our lab. Due to the tight packing of many PSAPDs in the system a thermal gradient is expected across the imaging heads. Data were collected for 11 PSAPD temperatures between 5°C and 40°C using a thermo-electric (Peltier) device. At each temperature the bias voltage was varied in steps of 5 V over a 50 V range. We present three methods to predict the optimal bias voltage at every temperature: one based on optimizing the coincidence time resolution, the others based on the relative change in PSAPD gain and leakage current due to the onset of hole multiplication. Optimal gain could also be predicted based on the quality of the flood histogram. At optimal bias voltage, the energy resolution degrades as (10.5±0.1)+((0.038±0.006)/ °C·T)%. Time resolution stays constant at 2.37±0.02 ns below 15°C. Above this temperature, time resolution deteriorates as (1.67±0.06)+((0.042±0.002)/°C·T)ns. Even at high temperatures, all 64 crystal position peaks in the flood histogram are still clearly visible. The width of the peaks in the flood histogram show a quadratic degradation with temperature: (2.6±0.1)·10-2+(1.6±0.2)·10-5/(°C)2·T2. We conclude that both the quality of the flood histogram as well as the coincidence time resolution are better parameters to estimate the optimal bias voltage, than energy resolution. Optimal bias voltage is found to be dependent on the value of k, the ratio between hole and electron multiplication. We

  9. Linking snow depth to avalanche release area size: measurements from the Vallée de la Sionne field site

    Science.gov (United States)

    Veitinger, Jochen; Sovilla, Betty

    2016-08-01

    One of the major challenges in avalanche hazard assessment is the correct estimation of avalanche release area size, which is of crucial importance to evaluate the potential danger that avalanches pose to roads, railways or infrastructure. Terrain analysis plays an important role in assessing the potential size of avalanche releases areas and is commonly based on digital terrain models (DTMs) of a snow-free summer terrain. However, a snow-covered winter terrain can significantly differ from its underlying, snow-free terrain. This may lead to different, and/or potentially larger release areas. To investigate this hypothesis, the relation between avalanche release area size, snow depth and surface roughness was investigated using avalanche observations of artificially triggered slab avalanches over a period of 15 years in a high-alpine field site. High-resolution, continuous snow depth measurements at times of avalanche release showed a decrease of mean surface roughness with increasing release area size, both for the bed surface and the snow surface before avalanche release. Further, surface roughness patterns in snow-covered winter terrain appeared to be well suited to demarcate release areas, suggesting an increase of potential release area size with greater snow depth. In this context, snow depth around terrain features that serve as potential delineation borders, such as ridges or trenches, appeared to be particularly relevant for release area size. Furthermore, snow depth measured at a nearby weather station was, to a considerable extent, related to potential release area size, as it was often representative of snow depth around those critical features where snow can accumulate over a long period before becoming susceptible to avalanche release. Snow depth - due to its link to surface roughness - could therefore serve as a highly useful variable with regard to potential release area definition for varying snow cover scenarios, as, for example, the avalanche

  10. Different Avalanche Behaviors in Different Specific Areas of a System Based on Neural Networks

    Institute of Scientific and Technical Information of China (English)

    ZHAOXiao-Wei; CHENTian-Lun

    2003-01-01

    Based on the standard self-organizing map (SOM) neural network model and an integrate-and-fire mecha-nism, we introduce a kind of coupled map lattice system to investigate scale-invariance behavior in the activity of model neural populations. We find power-law distribution behavior of avalanche size in our model. But more importantly, we find there are different avalanche distribution behaviors in different specific areas of our system, which are formed by the topological learning process of the SOM net.

  11. Performance assessment of simulated 3D laser images using Geiger-mode avalanche photo-diode: tests on simple synthetic scenarios

    Science.gov (United States)

    Coyac, Antoine; Hespel, Laurent; Riviere, Nicolas; Briottet, Xavier

    2015-10-01

    In the past few decades, laser imaging has demonstrated its potential in delivering accurate range images of objects or scenes, even at long range or under bad weather conditions (rain, fog, day and night vision). We note great improvements in the conception and development of single and multi infrared sensors, concerning embedability, circuitry reading capacity, or pixel resolution and sensitivity, allowing a wide diversity of applications (i.e. enhanced vision, long distance target detection and reconnaissance, 3D DSM generation). Unfortunately, it is often difficult to dispose of all the instruments to compare their performance for a given application. Laser imaging simulation has shown to be an interesting alternative to acquire real data, offering a higher flexibility to perform this sensors comparison, plus being time and cost efficient. In this paper, we present a 3D laser imaging end-to-end simulator using a focal plane array with Geiger mode detection, named LANGDOC. This work aims to highlight the interest and capability of this new generation of photo-diodes arrays, especially for airborne mapping and surveillance of high risk areas.

  12. 具有抑制边缘击穿的层叠结结构的平面型InGaAs/InP盖革雪崩光电二极管的设计%A Planar InGaAs/InP Geiger Mode Avalanche Photodiode with Cascade Edge Breakdown Suppression

    Institute of Scientific and Technical Information of China (English)

    吴孟; 林峰; 杨富华; 曹延名

    2008-01-01

    通过有限元分析设计了具有抑制边缘击穿的层叠边缘结结构的平面型InGaAs/InP盖革雪崩光电二极管.通过仔细地控制中央区域结的深度,光电二极管的击穿电压降至54.3V;同时通过调整InP倍增层的掺杂浓度和厚度,沿器件中轴的电场分布也得到了控制.在有源区的边缘采用层叠pn结结构有效地抑制了过早边缘击穿现象.仿真模拟显示四层层叠结构是边缘击穿抑制效果和制造工艺复杂度的一个好的折衷方案,该结构中峰值电场强度为5.2×105kV/cm,空穴离化积分最大值为1.201.本文提供了一种设计高性能的InGaAs/InP光子汁数雪崩光电二极管的有效方法.%A Geiger mode planar InGaAs/InP avalanche photodiode (APD) with a cascade peripheral junction structure to suppress edge breakdowns is designed by finite-element analysis. The photodiode breakdown voltage is reduced to 54.3V by controlling the central junction depth ,while the electric field distribution along the device central axis is controlled by adjusting doping level and thickness of the InP field control layer. Using a cascade junction structure at the periphery of the active area, premature edge breakdowns are effectively suppressed. The simulations show that the quadra-cascade structure is a good trade-off between suppression performance and fabrication complexity, with a reduced peak electric field of 5. 2 ×105 kV/cm and a maximum hole ionization integral of 1. 201. Work presented in this paper provides'an effective way to design high performance photon counting InGaAs/InP avalanche photodiodes.

  13. Snow Avalanches

    Science.gov (United States)

    Ancey, C.

    Over the last century, mountain ranges in Europe and North America have seen substantial development due to the increase in recreational activities, transportation, construction in high altitude areas, etc. In these mountain ranges, avalanches often threaten man's activities and life. Typical examples include recent disasters, such as the avalanche at Val d'Isère in 1970 (39 people were killed in a hostel) or the series of catastrophic avalanches throughout the Northern Alps in February 1999 (62 residents killed). The rising demand for higher safety measures has given new impetus to the development of mitigation technology and has given rise to a new scientific area entirely devoted to snow and avalanches. This paper summarises the paramount features of avalanches (formation and motion) and outlines the main approaches used for describing their movement. We do not tackle specific problems related to snow mechanics and avalanche forecasting. For more information on the subject, the reader is referred to the main textbooks published in Alpine countries [1-8].

  14. Characterization of a commercially available large area, high detection efficiency single-photon avalanche diode

    CERN Document Server

    Stipčević, Mario; Ursin, Rupert

    2013-01-01

    We characterize a new commercial, back-illuminated reach-through silicon single-photon avalanche photo diode (SPAD) SAP500 (Laser Components. Inc.), operated in Geiger-mode for purpose of photon counting. We show that for this sensor a significant interplay exists between dark counts, detection efficiency, afterpulsing, excess voltage and operating temperature, sometimes requiring a careful optimization tailored for a specific application. We find that a large flat plateau of sensitive area of about 0.5 mm in diameter, a peak quantum efficiency of 73% at 560 nm and timing precision down to 150 ps FWHM are the main distinguishing characteristics of this SPAD.

  15. Potential slab avalanche release area identification from estimated winter terrain: a multi-scale, fuzzy logic approach

    Science.gov (United States)

    Veitinger, Jochen; Purves, Ross Stuart; Sovilla, Betty

    2016-10-01

    Avalanche hazard assessment requires a very precise estimation of the release area, which still depends, to a large extent, on expert judgement of avalanche specialists. Therefore, a new algorithm for automated identification of potential avalanche release areas was developed. It overcomes some of the limitations of previous tools, which are currently not often applied in hazard mitigation practice. By introducing a multi-scale roughness parameter, fine-scale topography and its attenuation under snow influence is captured. This allows the assessment of snow influence on terrain morphology and, consequently, potential release area size and location. The integration of a wind shelter index enables the user to define release area scenarios as a function of the prevailing wind direction or single storm events. A case study illustrates the practical usefulness of this approach for the definition of release area scenarios under varying snow cover and wind conditions. A validation with historical data demonstrated an improved estimation of avalanche release areas. Our method outperforms a slope-based approach, in particular for more frequent avalanches; however, the application of the algorithm as a forecasting tool remains limited, as snowpack stability is not integrated. Future research activity should therefore focus on the coupling of the algorithm with snowpack conditions.

  16. 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.

  17. 室内可见光通信APD探测电路的设计与实现%Design and implementation of indoor visible light communication avalanche photodiode detecting circuit

    Institute of Scientific and Technical Information of China (English)

    郭倩; 蓝天; 朱祺; 倪国强

    2015-01-01

    室内可见光无线通信技术是随着白光LED照明技术的发展而兴起的无线光通信技术。在分析目前的可见光通信技术基础上,针对室内可见光通信系统的应用需求,设计了雪崩光电二极管(APD)探测电路组件。首先阐述了APD探测电路的工作原理,其次详细设计并分析了系统各组成部分的电路结构及其功能,最后对所设计的用于室内可见光通信接收子系统的探测组件进行了相关实验测试。实验结果表明:设计有效可行,APD探测电路具有增益高、带宽宽、温控可靠、稳定性好等优点,对室内可见光通信系统有很好的应用价值,为室内可见光通信系统进一步研究提供依据。%Recently, the indoor visible light wireless communications technology is emerged companied with the blooming white light- emitting diode (LED) lighting technology. In this thesis, the current visible light communication system was analyzed and aiming at the request of application in indoor visible light communication system, an avalanche photodiode (APD) detecting circuit was designed. Firstly, the work principle of the APD detecting circuit was described. Secondly, a detailed design and analysis of the system structure and their function of the circuit components was presented. Finally, a detecting circuit component of the indoor visible light wireless communications receivers was designed, and related experiment tests were tested. Experimental results show that the design is effective and feasible, the APD detecting circuit has high gain, wide bandwidth, stable temperature control and high stability etc, therefore the detecting circuit is capable of meeting the needs of indoor visible light communication systems, provides a basis for further study on indoor visible light communication systems.

  18. 一种基于雪崩二极管电容特性提取通讯波段单光子信号的方法%A Feasible Method for Detecting 1.5 μm Single Photon Based on Capacitance Nature of Avalanche Photodiode

    Institute of Scientific and Technical Information of China (English)

    齐兰; 杨磊; 郭学石; 李小英

    2013-01-01

    InGaAs/InP雪崩二极管(APD)可用于探测光通讯波段的单光子.APD工作于门模盖革模式时,单个光子引起的雪崩电流信号通常淹没在电容瞬时充放电脉冲中,光电流信号提取困难.本文通过调整实验参数和APD的寄生电容,使雪崩信号与放电脉冲在时域上有效叠加,并由高速比较器将光电流信号直接甄别出来.本文设计的基于InGaAs/InP APD的单光子探测系统,运行稳定,方法简单可靠,说明这种利用APD的电容特性提取单光子信号是一种有效的方法.%InGaAs/InP avalanche photodiode(APD) working in gated Geiger mode can be used to measure single photons in the 1550 nm telecom-band.However,it is difficult to extract the photon induced avalanche current,which is usually buried in the charge and discharge pulses due to junction capacitance.When the avalanche signal and discharge pulse are properly overlaped in the time domain,the avalanche photocurrent is directly discriminated by high-speed comparator.The single photon detection system is simple and stable,which proves that it is efficient to extract the photon with this feature.

  19. Geomorphological analysis, monitoring and modeling of large rock avalanches in northern Chile (Iquique area) for regional hazard assessment.

    Science.gov (United States)

    Yugsi Molina, F. X.; Hermanns, R. L.; Crosta, G. B.; Dehls, J.; Sosio, R.; Sepúlveda, S. A.

    2012-04-01

    Iquique is a city of about 215,000 inhabitants (Chilean national census 2002) settled on one of the seismic gaps in the South American subduction zone, where a M >8 earthquake with overdue return periods of ca. 100 yr is expected in the near future. The city has only two access roads coming from the east and south. The road to the east comes down along the escarpment that connects the Coastal Cordillera to the Coastal Plain. The road has been blocked by small magnitude earthquake-triggered landslides at least once in recent years. The second road, coming from the south, crosses along the Coastal Plain and connects the city to the airport where at least ten ancient debris deposits related to rock avalanches are found. These facts show the importance of determining the effects of a future high magnitude earthquake on the stability of the slopes in the area and the impact of possible slope failures on people, infrastructure and emergency management. The present work covers an area of approximately 130 km2 parallel to the coastline to the south of Iquique, divided into the two main morphological units briefly mentioned above. The eastern part corresponds to the Coastal Cordillera, a set of smoothed hills and shallow valleys that reaches up to 1200 m asl. This sector is limited to the west by a steep escarpment followed by the Coastal Plain and a narrow emerged marine plateau (1-3 km wide) locally overlaid by deposits of recent rock avalanches. Rock avalanche events have recurrently occurred at two sites to the north and center of the study area on the Coastal Cordillera escarpment. Another major single event has been mapped to the south. Marls, red and black shales, and shallow marine glauconitic deposits from Jurassic constitute the source rock for the rock avalanches in all sites. Clusters of deposits are found in the first two sites (retrogressive advance) with younger events running shorter distances and partially overlaying the older ones. Multiple lobes have been

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

    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...

  1. On the influence of topographic, geological and cryospheric factors on rock avalanches and rockfalls in high-mountain areas

    Directory of Open Access Journals (Sweden)

    L. Fischer

    2012-01-01

    Full Text Available The ongoing debate about the effects of changes in the high-mountain cryosphere on rockfalls and rock avalanches suggests a need for more knowledge about characteristics and distribution of recent rock-slope instabilities. This paper investigates 56 sites with slope failures between 1900 and 2007 in the central European Alps with respect to their geological and topographical settings and zones of possible permafrost degradation and glacial recession. Analyses of the temporal distribution show an increase in frequency within the last decades. A large proportion of the slope failures (60% originated from a relatively small area above 3000 m a.s.l. (i.e. 10% of the entire investigation area. This increased proportion of detachment zones above 3000 m a.s.l. is postulated to be a result of a combination of factors, namely a larger proportion of high slope angles, high periglacial weathering due to recent glacier retreat (almost half of the slope failures having occurred in areas with recent deglaciation, and widespread permafrost occurrence. The lithological setting appears to influence volume rather than frequency of a slope failure. However, our analyses show that not only the changes in cryosphere, but also other factors which remain constant over long periods play an important role in slope failures.

  2. Influence of weak layer heterogeneity and slab properties on slab tensile failure propensity and avalanche release area

    Directory of Open Access Journals (Sweden)

    J. Gaume

    2014-12-01

    Full Text Available Dry-snow slab avalanches are generally caused by a sequence of fracture processes including failure initiation in a weak snow layer underlying a cohesive slab followed by crack propagation within the weak layer (WL and tensile fracture through the slab. During past decades, theoretical and experimental work has gradually improved our knowledge of the fracture process in snow. However, our limited understanding of crack propagation and fracture arrest propensity prevents the evaluation of avalanche release sizes and thus impedes hazard assessment. To address this issue, slab tensile failure propensity is examined using a mechanically-based statistical model of the slab–WL system based on the finite element method. This model accounts for WL heterogeneity, stress redistribution by elasticity of the slab and the slab possible tensile failure. Two types of avalanche release are distinguished in the simulations: (1 full-slope release if the heterogeneity is not sufficient to stop crack propagation and to trigger a tensile failure within the slab, (2 partial-slope release if fracture arrest and slab tensile failure occurs due to the WL heterogeneity. The probability of these two release types is presented as a function of the characteristics of WL heterogeneity and of the slab. One of the main outcomes is that, for realistic values of the parameters, the tensile failure propensity is mainly influenced by slab properties. Hard and thick snow slabs are more prone to wide-scale crack propagation and thus lead to larger avalanches (full-slope release. In this case, the avalanche size is mainly influenced by topographical and morphological features such as rocks, trees, slope curvature and the spatial variability of the snow depth as it is often claimed in the literature.

  3. Characterization of Large Area APDs for the EXO-200 Detector

    Energy Technology Data Exchange (ETDEWEB)

    Neilson, R.; LePort, F.; Pocar, A.; /Stanford U., Phys. Dept.; Kumar, K.; /Massachusetts U., Amherst; Odian, A.; Prescott, C.Y.; /SLAC; Tenev, V.; /Stanford U., Phys. Dept.; Ackerman, N.; /SLAC; Akimov, D.; /Moscow, ITEP; Auger, M.; /Bern U., LHEP; Benitez-Medina, C.; /Colorado State U.; Breidenbach, M.; /SLAC; Burenkov, A.; /Moscow, ITEP; Conley, R.; /SLAC; Cook, S.; /Colorado State U.; deVoe, R.; Dolinski, M.J.; /Stanford U., Phys. Dept.; Fairbank, W., Jr.; /Colorado State U.; Farine, J.; /Laurentian U.; Fierlinger, P.; Flatt, B.; /Stanford U., Phys. Dept. /Bern U., LHEP /Stanford U., Phys. Dept. /Maryland U. /Colorado State U. /Laurentian U. /Carleton U. /SLAC /Maryland U. /Moscow, ITEP /Alabama U. /SLAC /Colorado State U. /Stanford U., Phys. Dept. /Alabama U. /Stanford U., Phys. Dept. /Alabama U. /SLAC /Carleton U. /SLAC /Maryland U. /Moscow, ITEP /Carleton U. /Stanford U., Phys. Dept. /Bern U., LHEP /SLAC /Laurentian U. /SLAC /Maryland U.

    2011-12-02

    EXO-200 uses 468 large area avalanche photodiodes (LAAPDs) for detection of scintillation light in an ultra-low-background liquid xenon (LXe) detector. We describe initial measurements of dark noise, gain and response to xenon scintillation light of LAAPDs at temperatures from room temperature to 169 K - the temperature of liquid xenon. We also describe the individual characterization of more than 800 LAAPDs for selective installation in the EXO-200 detector.

  4. SiC Avalanche Photodiodes and Arrays Project

    Data.gov (United States)

    National Aeronautics and Space Administration — In this Phase 2 SBIR program submitted to National Aeronautics and Space Administration (NASA) in response to Topic S1.05 (Detector Technologies for UV, X-Ray,...

  5. High Efficiency UV Photodiodes fabricated on p-type Substrate

    NARCIS (Netherlands)

    Ramachandra Rao, P.; Milosavljevic, S.; Kroth, U.; Laubis, C.; Nihtianov, S.

    2014-01-01

    Newly developed “pure-boron” photodiodes, with high sensitivity and stability in the whole ultraviolet range (UV), are described. The main purpose of this work is to create and characterize a large-area UV photodiode, representing a structure of a pixel in a backside illuminated CMOS image sensor, f

  6. In0.53Ga0.47As/In0.52Al0.48As雪崩光电二极管的数值模拟研究%Numerical simulation study on In0.53Ga0.47As/In0.52Al0.48As avalanche photodiode

    Institute of Scientific and Technical Information of China (English)

    李慧梅; 胡晓斌; 白霖; 李晓敏; 于海龙; 徐云; 宋国峰

    2016-01-01

    An analytical modeling of In0.53Ga0.47As/In0.52Al0.48As avalanche photodiode (APD) was proposed with In0.52Al0.48As charge layer between the absorption and multiplication region (SACM). Numerical study and theoretical analysis were performed to design a high performance In0.53Ga0.47As/In0.52Al0.48As APD. An In0.52Al0.48As barrier layer was adopted to block minority carriers originated from contact regions in our APD. Simultaneously, double-doped multiplication layer was used to improve the electric field gradient change of the multiplication region and reduce the dark current. In addition, the influence of different doping level and different thickness of every layer on the energy band, the electric field distribution, breakdown voltage and current-voltage characteristics were also investigated by using device simulation software ATLAS from SILVACO international. The photodetector exhibits a high responsivity of 0.9 A/W at the unity gain. The gain is 23.4 at the operating voltage(0.9 Vb). Furthermore, the dark current is only in the nano-ampere orders of magnitude at 0.9 Vb.%建立了SACM型In0.53Ga0.47As/In0.52Al0.48As雪崩光电二极管(APD)的分析模型,通过数值研究和理论分析设计出高性能的In0.53Ga0.47As/In0.52Al0.48As APD。器件设计中,一方面添加了In0.52Al0.48As势垒层来阻挡接触层的少数载流子的扩散,进而减小暗电流的产生;另一方面,雪崩倍增区采用双层掺杂结构设计,优化了器件倍增区的电场梯度分布。最后,利用ATLAS软件较系统地研究并分析了雪崩倍增层、电荷层以及吸收层的掺杂水平和厚度对器件电场分布、击穿电压、IV特性和直流增益的影响。优化后APD的单位增益可以达到0.9 A/W,在工作电压(0.9 Vb)下增益为23.4,工作暗电流也仅是纳安级别(@0.9 Vb)。由于In0.52Al0.48As材料的电子与空穴的碰撞离化率比InP材料的差异更大,因此器件的噪声因子也较低。

  7. 高分辨率高效率三维正电子发射断层扫描成像探测器研发%High Spatial Resolution and High Sensitivity Three Dimensional PET Detector Development with Position-sensitive Avalanche Photodiode and Silicon Photomultiplier Readout

    Institute of Scientific and Technical Information of China (English)

    李成; 邝忠华; 都军伟; 白晓薇; Simon R. Cherry; 梁栋; 刘新; 郑海荣; 杨永峰

    2016-01-01

    Small animal positron emission tomography (PET) is a well-established imaging modality in preclinical biomedical research. But depth encoding detectors are required to simultaneously achieve high spatial resolution and high sensitivity for a small animal PET scanner. In this work, we evaluated several dual-ended readout detector modules using lutetium oxyorthosilicate (LSO) arrays with crystal sizes ranging from 0.70 mm to 0.44 mm, read out by either position-sensitive avalanche photodiodes (PSAPDs) or position-sensitive silicon photomultipliers (PS-SiPMs). A new type of PS-SiPM was developed recently and was evaluated for the ifrst time in this work. First, the signal-to-noise ratio (SNR) of both PSAPDs and PS-SiPMs was measured, and then the lfood histograms, energy resolution and depth of interaction (DOI) resolution of dual-ended readout detector modules by using both PSAPDs and PS-SiPMs were measured. The PSAPD has much better SNR as compared with PS-SiPM. For the detectors using PSAPDs, crystals as small as 0.44 mm can be resolved and a DOI resolution as good as 1.4 mm was obtained. For the detectors using PS-SiPMs, 0.7 mm crystals can be resolved and a DOI resolution of 2.9 mm was obtained. Based on the results of the lfood histograms, energy resolution and DOI resolution the detector modules using PSAPD are better than those using PS-SiPMs. The SNR of the PS-SiPM would need to be improved to resolve even smaller crystals and the number of SiPM cells also need to be increased to reduce the saturation effect to improve the DOI resolution. The performance of the three dimensional depth encoding PET detectors using PSAPDs is much better because the SNR of PSAPD is much higher than PS-SiPM. In the future, high resolution depth encoding PET detectors will be developed by using both new PS-SiPMs and SiPM arrays.%小动物正电子发射断层扫描成像(Positron Emission Tomography,PET)是临床前生物医学研究的重要工具,但小动物 PET要同时

  8. A silicon drift photodiode

    Energy Technology Data Exchange (ETDEWEB)

    Avset, B.S.; Evensen, L.; Ellison, J.A.; Hall, G.; Roe, S.; Wheadon, R.; Hansen, T.E.

    1989-02-01

    A low capacitance photodiode based on the principle of the solid state drift chamber has been constructed and tested. The device is based on a cellular design with an anode at the centre of each of five cells allowing electrons liberated by ionisation to drift up to 1mm to the read out strip. Results on the performance of the detector, including leakage current, capacitance and drift properties, are presented and compared with simulations.

  9. Inkjet-printed organic photodiodes

    International Nuclear Information System (INIS)

    Inkjet-printed organic photodiodes are reported, which eliminate the need for photodiode patterning as compared to other solution-based fabrication techniques. Both interlayer and bulk heterojunction ink formulations are optimized to fabricate diodes with low dark currents of 2 μA/cm2 and high external quantum efficiencies of 68.5% at - 5 V reverse bias. The current-voltage characteristics of the printed devices are competitive with photodiodes fabricated with established solution based technologies, such as spray-coating or blading. A comparison of photodiodes fabricated with a variety of solution processes showed that dark current densities are not related to microscale bulk heterojunction roughness.

  10. Avalanche effects near nanojunctions

    Science.gov (United States)

    Nandigana, Vishal V. R.; Aluru, N. R.

    2016-07-01

    In this article, we perform a computational investigation of a nanopore connected to external fluidic reservoirs of asymmetric geometries. The asymmetry between the reservoirs is achieved by changing the cross-sectional areas, and the reservoirs are designated as the micropore reservoir and macropore reservoir. When an electric field is applied, which is directed from the macropore towards the micropore reservoir, we observe local nonequilibrium chaotic current oscillations. The current oscillations originate at the micropore-nanopore interface owing to the local cascade of ions; we refer to this phenomenon as the "avalanche effects." We mathematically quantify chaos in terms of the maximum Lyapunov exponent. The maximum Lyapunov exponent exhibits a monotonic increase with the applied voltage and the macropore reservoir diameter. The temporal power spectra maps of the chaotic currents depict a low-frequency "1 /f "-type dynamics for the voltage chaos and "1 /f2 "-type dynamics for the macropore reservoir chaos. The results presented here offer avenues to manipulate ionic diodes and fluidic pumps.

  11. 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

  12. Fast silicon drift photodiodes free from bias connections on the light entering side

    CERN Document Server

    Castoldi, A; Gatti, E; Holl, P; Rehak, P

    2000-01-01

    A new type of silicon drift photodiode intended to be coupled to large area scintillators is described. The diodes have a relatively large area (1 cm sup 2) and a short maximal drift time (300 ns). They operate without requiring any external electrical connection at the side of the photodiode coupled to the scintillating crystal. These new photodiodes have almost identical ring structures on both sides with individual rings being at linearly increasing potentials providing the required high electric drift field. A new feature of the presented photodiodes is a small modification of the electrode structure near the signal collecting anode. It allows a full depletion of the photodiode and the highest drift field. Advantages and drawbacks of this kind of photodiodes are described.

  13. Rock avalanches: significance and progress (Invited)

    Science.gov (United States)

    Davies, T. R.

    2013-12-01

    1. The probability distribution of landslide volumes follows a power-law indicating that large rock avalanches dominate the terrestrial sediment supply from mountains, and that their source area morphologies dominate mountain topography. 2. Large rock slope failures (~ 106 m3 or greater) often mobilise into rock avalanches, which can travel extraordinarily long distances with devastating effect. This hypermobility has been the subject of many investigations; we have demonstrated that it can be explained quantitatively and accurately by considering the energetics of the intense rock fragmentation that always occurs during motion of a large rock mass. 3. Study of rock avalanche debris psd shows that the energy used in creating new rock surface area during fragmentation is not lost to surface energy, but is recycled generating a high-frequency elastic energy field that reduces the frictional resistance to motion during runout. 4. Rock avalanches that deposit on glaciers can eventually form large terminal moraines that have no connection with any climatic event; unless these are identified as rock-avalanche-influenced they can confuse palaeoclimatic inferences drawn from moraine ages. Rock-avalanche-derived fines, however, can be identified in moraine debris up to ten thousand years old by the characteristic micron-scale agglomerates that form during intense fragmentation, and which are absent from purely climatically-induced moraines; there is thus a strong case for re-examining existing palaeoclimatic databases to eliminate potentially rock-avalanche-influenced moraine ages. 5. Rock avalanches (especially coseismic ones) are a serious hazard, being very destructive in their own right; they also block river valleys, forming landslide dams and potentially devastating dambreak floods, and subsequent severe decade-scale aggradation of downstream fans and floodplains. Rock avalanches falling into lakes or fiords can cause catastrophic tsunami that pose a serious risk to

  14. Contribution of generation-recombination processes at inner interface of MBE-grown Hg1-xCdxTe heterostucture to dark current of small active area photodiode

    Science.gov (United States)

    Chekanova, Galina V.; Drugova, Albina A.; Kholodnov, Viacheslav; Nikitin, Mikhail S.

    2009-09-01

    Multilayer heterostructures of Hg1-xCdxTe alloy grown by Molecular Beam Epitaxy (MBE) on large size alternative substrates Si, GaAs and Ge are considered as one of productive alternative materials for issue of large format photovoltaic (PV) infrared (IR) focal plane arrays. However reaching of ultimate performance of small-pitched photodiode's (PD) covering spectral range from 8 to 12 μm depends on electronic properties of both individual layers and heterostructure interfaces. Due to small thickness of heterostructure layers, interfaces are located close to active regions of p-n junction and hence generation-recombination processes at interfaces will contribute to value of current flowing through junction. As usual measured dark current value of small-sized PD is higher than estimated from calculation and cannot be explained by discrepancy between real and estimated charge carriers concentration in absorption layers where p-n junction is formed. Objective of the present work was to calculate the contribution of recombination of charge carriers via electronic states on nearby inner interface to dark current of Hg1-xCdxTe LWIR PD (λco equals to 9.5-10.3 μm at Top=77 K) and its variation with absorption layer parameters and compare it to measured data on small-pitched arrays. We have concluded previously that at high recombination rate dark current can grow in orders of value.

  15. Non-Markovian property of afterpulsing effect in single-photon avalanche detector

    CERN Document Server

    Wang, Fang-Xiang; Li, Ya-Ping; He, De-Yong; Wang, Chao; Han, Yun-Guang; Wang, Shuang; Yin, Zhen-Qiang; Han, Zheng-Fu

    2016-01-01

    The single-photon avalanche photodiode(SPAD) has been widely used in research on quantum optics. The afterpulsing effect, which is an intrinsic character of SPAD, affects the system performance in most experiments and needs to be carefully handled. For a long time, afterpulsing has been presumed to be determined by the pre-ignition avalanche. We studied the afterpulsing effect of a commercial InGaAs/InP SPAD (The avalanche photodiode model is: Princeton Lightwave PGA-300) and demonstrated that its afterpulsing is non-Markovian, with a memory effect in the avalanching history. Theoretical analysis and experimental results clearly indicate that the embodiment of this memory effect is the afterpulsing probability, which increases as the number of ignition-avalanche pulses increase. This conclusion makes the principle of the afterpulsing effect clearer and is instructive to the manufacturing processes and afterpulsing evaluation of high-count-rate SPADs. It can also be regarded as a fundamental premise to handle ...

  16. Practical methods for using vegetation patterns to estimate avalanche frequency and magnitude

    Science.gov (United States)

    Simonson, S.; Fassnacht, S. R.

    2011-12-01

    Practitioners working in avalanche terrain may never witness an extreme event, but understanding extreme events is important for categorizing avalanches that occur within a given season. Historical records of avalanche incidents and direct observations are the most reliable evidence of avalanche activity, but patterns in vegetation can be used to further quantify and map the frequency and magnitude of past events. We surveyed published literature to synthesize approaches for using vegetation sampling to characterize avalanche terrain, and developed examples to identify the benefits and caveats of using different practical field methods to estimate avalanche frequency and magnitude. Powerful avalanches can deposit massive piles of snow, rocks, and woody debris in runout zones. Large avalanches (relative to the path) can cut fresh trimlines, widening their tracks by uprooting, stripping, and breaking trees. Discs and cores can be collected from downed trees to detect signals of past avalanche disturbance recorded in woody plant tissue. Signals of disturbance events recorded in tree rings can include direct impact scars from the moving snow and wind blast, development of reaction wood in response to tilting, and abrupt variation in the relative width of annual growth rings. The relative ages of trees in avalanche paths and the surrounding landscape can be an indicator of the area impacted by past avalanches. Repeat photography can also be useful to track changes in vegetation over time. For Colorado, and perhaps elsewhere, several vegetation ecology methods can be used in combination to accurately characterize local avalanche frequency and magnitude.

  17. 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...

  18. Small Signal Circuit Model of Double Photodiodes

    Institute of Scientific and Technical Information of China (English)

    HAN Jian-zhong; Ni Guo-qiang; MAO Lu-hong

    2004-01-01

    The transmission delay of photogenerated carriers in a CMOS-process-compatible double photodiode (DPD) is analyzed by using device simulation. The DPD small signal equivalent circuit model which includes transmission delay of photogenerated carriers is given. From analysis on the frequency domain of the circuit model the device has two poles. One has the relationship with junction capacitance and the DPD's load,the other with the depth and the doping concentration of the N-well in the DPD. Different depth of the Nwell and different area of the DPDs with bandwidth were compared. The analysis results are important to design the high speed DPDs.

  19. Measuring acoustic emissions in an avalanche slope

    Science.gov (United States)

    Reiweger, Ingrid; Schweizer, Jürg

    2014-05-01

    Measurements of acoustic emissions are a common technique for monitoring damage and predicting imminent failure of a material. Within natural hazards it has already been used to successfully predict the break-off of a hanging glacier. To explore the applicability of the acoustic emission (AE) technique for avalanche prediction, we installed two acoustic sensors (with 30 kHz and 60 kHz resonance frequency) in an avalanche prone slope at the Mittelgrat in the Parsenn ski area above Davos, Switzerland. The slope is north-east facing, frequently wind loaded, and approximately 35° steep. The AE signals - in particular the event energy and waiting time distributions - were compared with slope stability. The latter was determined by observing avalanche activity. The results of two winter's measurements yielded that the exponent β of the inverse cumulative distribution of event energy showed a significant drop (from a value of 3.5 to roughly 2.5) at very unstable conditions, i.e. on the three days during our measurement periods when spontaneous avalanches released on our study slope.

  20. DUE AvalRS: Remote Sensing Derive Avalanche Inventory Data for Decision Support and Hind-Cast After Avalanche Events

    Science.gov (United States)

    Frauenfelder, Regula; Kronholm, Kalle; Solberg, Rune; Larsen, Siri Oyen; Salberg, Arnt-Borre; Larsen, Jan Otto; Bjordal, Heidi

    2010-12-01

    Each year, snow avalanches hit populated areas and parts of the transport network in the Norwegian mountain regions, leading to loss of lives and the damaging of buildings and infrastructure. We present the results of a feasibility study on the operation of a service providing the National Public Roads Administration (NPRA) with hind-cast avalanche inventory data on a local-to-regional scale during the course of the winter season, and as soon as possible after major avalanche events. We have explored the use of imagery from high-resolution and very-high-resolution space-borne satellites applying manual mapping and automated image segmentation.

  1. Avalanche Debris Detection Using Satellite- and Drone Based Radar and Optical Remote Sensing

    Science.gov (United States)

    Eckerstorfer, M.; Malnes, E.; Vickers, H.; Solbø, S. A.; Tøllefsen, A.

    2014-12-01

    The mountainous fjord landscape in the county of Troms, around its capital Tromsø in Northern Norway is prone to high avalanche activity during the snow season. Large avalanches pose a hazard to infrastructure, such as buildings and roads, located between the steep mountainsides and the fjords. A prolonged cold spell during January and February 2014 was followed by rapid new-snow loading during March 2014, inducing a significant avalanche cycle with many spontaneous, size D4 avalanches that affected major transport veins. During and shortly after the avalanche cycle of March 2014, we obtained 11 Radarsat-2 Ultrafine mode scenes, chosen according to reported avalanche activity. We further collected four Radarsat-2 ScanSAR mode scenes and two Landsat-8 scenes covering the entire county of Troms. For one particular avalanche, we obtained a drone-based orthophoto, from which a DEM of the avalanche debris surface was derived, using structure-from-motion photogrammetry. This enabled us to calculate the debris volume accurately. We detected avalanche debris in the radar images visually, by applying two detection algorithms that make use of the increased backscatter in avalanche debris. This backscatter increase is a product of increased snow water equivalent and surface roughness, roughly of the order of 3 dB. In addition, we applied a multi-temporal approach by repeatedly detecting avalanche debris at different acquisition times, as well as a multi-sensor approach, covering similar areas with different sensors. This multi-temporal and multi-sensor approach enabled us to map the spatial extent and magnitude of the March 2014 avalanche cycle in the county Troms. With ESA's Sentinel-1 satellite, providing high-resolution, large swath radar images with a short repeat cycle, a complete avalanche record for a forecasting region could become feasible. In this first test season, we detected more than 550 avalanches that were released during a one-month period over an area of

  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. Characteristics of avalanche accidents and a overview of avalanche equipment

    Directory of Open Access Journals (Sweden)

    Mateusz Biela

    2015-12-01

    Full Text Available Avalanches are one of the most spectacular phenomena which may occur in the mountains. Unfortunately they are often caused by humans and pose for him a big danger. In the Polish Tatras alone they represent 18% of all causes of death among 1996-2013. One fourth of the people caught by an avalanche dies, and their chances of survival depends on the depth of burial, burial time, the presence of an air pocket and the degree of injuries. The most common cause of death is asphyxiation, the next is injuries and hypothermia is the rarest cause of death. The fate of the buried people depends on their equipment such as avalanche transceiver, ABS backpack and AvaLung, and also from the equipment of the people who are seeking (avalanche probes, avalanche transceiver and shovels, which has been proven in practice and research.

  4. A revision of the Haiming rock avalanche (Eastern Alps)

    Science.gov (United States)

    Dufresne, Anja; Ostermann, Marc; Kelfoun, Karim; Ring, Max; Asam, Dario; Prager, Christoph

    2016-04-01

    The carbonate Haiming rock avalanche is directly neighbouring the larger Tschirgant rock avalanche deposit, both located in the upper Inn valley (Tyrol, Austria). Based on detailed morpho-lithologic mapping of the deposit, which has not been done at Haiming before, the sedimentology of the Holocene landslide debris is characterised. Structural-tectonic elements of the bedrock units at the scarp area are supplemented with borehole data from drillings at the source area giving valuable insights into the complex geological bedrock composition and structure. New source and runout reconstructions allow updated volumetric calculations, which are subsequently integrated into numerical runout modelling. Haiming is one of few topographically unobstructed rock avalanches, yet its morphology was greatly influenced by fluvial terraces, which are still discernible through the deposit on LiDAR hillshade images. We also address the influence of the rock avalanche on the valley floor and local river system as a short-lived dam and its interaction with fluvial incision. Finally, we discuss the Haiming rock avalanche in view of the other massive rock slope failures in the area ("Fernpass cluster"), their spatio-temporal distribution, and point out further highlights of this simple(?) rock avalanche deposit.

  5. The Marocche rock avalanches (Trentino, Italy)

    Science.gov (United States)

    Ivy-Ochs, Susan; Martin, Silvana; Campedel, Paolo; Viganò, Alfio; Alberti, Silvio; Rigo, Manuel; Vockenhuber, Christof

    2015-04-01

    The floors of the Adige and Sarca River valleys are punctuated by numerous rock avalanche deposits of undetermined age. With a view to understanding predisposition and triggering factors, thus ultimately paleoseismicity in the region, we are studying the geomorphology and timing of the largest rock avalanches of the River Sarca-Lake Garda area (e.g., Marocche, Monte Spinale, Lago di Tovel, Lago di Molveno, San Giovanni and Torbole). Among the most extensive of these deposits, with an area of 13 km2 and a volume of about 109 m3, are the Marocche. Marocche deposits cover the lower Sarca valley north of Lake Garda for a length of more than 8 km with 200 m of debris. Both collapse and bedding parallel sliding are a consequence of dip slopes and the extreme relief on the right side of the valley of nearly 2000 m from the bedrock below the valley floor to the peaks combined with the zones of structural weakness. The rock avalanches developed within carbonate rocks of Mesozoic age, mainly limestones of the Jurassic Calcari Grigi Group. The main scarps are located on the western side of the lower Sarca Valley, along the steep faces of Mt. Brento and Mt. Casale. The presence of these scarps is strictly related to the Southern Giudicarie and the Ballino fault systems. The former is here constituted by regular NNE-directed ESE-vergent thrust faults. The latter has been reactivated as normal faults. These complicated structural relationships favored complex failure mechanisms, including rock slide and massive collapse. At the Marocche itself, based on field relationships and analysis of lidar imagery, we differentiated two large rock avalanches: the Marocca di Kas in the south which overlies and in part buries the Marocche (s.s.) in the northern sector. Previous mapping had suggested up to five rock avalanches in the area where we differentiate two. In spite of hypotheses suggesting failure of the rock avalanches onto stagnating late Pleistocene glaciers, preliminary 36Cl

  6. La carte de localisation des phénomènes d'avalanche (CLPA) : enjeux et perspectives

    OpenAIRE

    Bonnefoy, M.; Borrel, G.; Richard, D.; Bélanger, L; Naaïm, M.

    2010-01-01

    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 Mon...

  7. Symmetric two-coordinate photodiode

    Directory of Open Access Journals (Sweden)

    Dobrovolskiy Yu. G.

    2008-12-01

    Full Text Available The two-coordinate photodiode is developed and explored on the longitudinal photoeffect, which allows to get the coordinate descriptions symmetric on the steepness and longitudinal resistance great exactness. It was shown, that the best type of the coordinate description is observed in the case of scanning by the optical probe on the central part of the photosensitive element. The ways of improvement of steepness and linear of its coordinate description were analyzed.

  8. Novel vertical silicon photodiodes based on salicided polysilicon trenched contacts

    International Nuclear Information System (INIS)

    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

  9. 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.

  10. Utilization of photodiodes for ionizing radiation dosimetry

    International Nuclear Information System (INIS)

    The behaviour of silicon photodiodes as detector, for gama and x-ray dosimetry is discussed. Measurements were realized with photodiodes operating in the photovoltaic mode, the current produzed was detected in the eletrometer constructed in the DEN/UFPE. The results obtained showed that the photodiode response is linear with the dose and that variation of 40 degrees in the incidence angule of the radiation caused a variation of 5% in the dose determination. (author)

  11. Development of high gain photodiode array based on commercial CMOS process

    International Nuclear Information System (INIS)

    Developing photodiodes in commercial CMOS process and integrating it with readout electronics without any process modification involves formidable challenges. Due to low resistivity of the wafer used in commercial CMOS process, the junction capacitance per area of the PN junction is quite large thereby limiting the size of the active area of the photodiode leading to degradation in high speed response. On the contrary, the sensitivity and quantum efficiency of the optical detector tends to improve with increase in active area of the detector. The major challenge in designing high gain photodiode in sub micron CMOS technology is to avoid the premature perimeter edge breakdown or the soft breakdown. This paper reports two different design approaches of high gain photodiode arrays in commercial 0.35 um CMOS technology and HV CMOS process

  12. Avalanche multiplication and ionization coefficient in AlGaAs/InGaAs p-n-p heterojunction bipolar transistors

    OpenAIRE

    B. Yan; Yang, ES

    1999-01-01

    The hole-initiated impact ionization multiplication factor Mp -1 and the ionization coefficient αp in AlGaAs/InGaAs p-n-p heterojunction bipolar transistors are presented. A large departure is observed at low electric field when comparison is made between the measured data and those obtained from avalanche photodiode measurements. The results show that the conventional impact ionization models, based on local electric field, substantially overestimate the hole impact ionization multiplication...

  13. Neuronal avalanches and coherence potentials

    Science.gov (United States)

    Plenz, D.

    2012-05-01

    The mammalian cortex consists of a vast network of weakly interacting excitable cells called neurons. Neurons must synchronize their activities in order to trigger activity in neighboring neurons. Moreover, interactions must be carefully regulated to remain weak (but not too weak) such that cascades of active neuronal groups avoid explosive growth yet allow for activity propagation over long-distances. Such a balance is robustly realized for neuronal avalanches, which are defined as cortical activity cascades that follow precise power laws. In experiments, scale-invariant neuronal avalanche dynamics have been observed during spontaneous cortical activity in isolated preparations in vitro as well as in the ongoing cortical activity of awake animals and in humans. Theory, models, and experiments suggest that neuronal avalanches are the signature of brain function near criticality at which the cortex optimally responds to inputs and maximizes its information capacity. Importantly, avalanche dynamics allow for the emergence of a subset of avalanches, the coherence potentials. They emerge when the synchronization of a local neuronal group exceeds a local threshold, at which the system spawns replicas of the local group activity at distant network sites. The functional importance of coherence potentials will be discussed in the context of propagating structures, such as gliders in balanced cellular automata. Gliders constitute local population dynamics that replicate in space after a finite number of generations and are thought to provide cellular automata with universal computation. Avalanches and coherence potentials are proposed to constitute a modern framework of cortical synchronization dynamics that underlies brain function.

  14. Sediment Transport by Spring Avalanches in the Southern Swiss Alps

    Science.gov (United States)

    Egloff, J. M.; Hunziker, M.; Moore, J. R.; Christen, M.

    2010-12-01

    Dense wet-snow avalanches breaking through to the base of the snow pack or overriding snow-free surfaces can entrain basal material and act as important agents of sediment transport in steep Alpine catchments. As part of an ongoing study, we investigated two debris fans in the Matter Valley of southern Switzerland during spring 2009 and 2010, with emphasis on quantifying avalanche sediment transport. Deposited debris ranged from soil parcels and plant material to cobbles and boulders greater than 1 m3. Large boulders were generally angular and fresh with clear signs of recent impacts. The seasonal sediment load transported by avalanches was estimated at one fan by sampling the debris content within a number of representative areas, and then extrapolating the cumulative volume. Results reveal a total transported sediment volume of ~150 m3 in 2009 and ~15 m3 in 2010, which likely reflects varying snowfall and avalanche frequency between years. When distributed over the deposition area on the fan, these results imply an average accumulated sediment thickness of 12 mm in 2009 and 3 mm in 2010. Calculated catchment-wide erosion rates are ~0.1 mm/yr for 2009 and ~0.01 mm/yr for 2010. Cross-sections through avalanche debris revealed that transported sediment generally resides on top of the snow surface. As the avalanches melt, entrained sediment is set down gently, often resulting in precariously balanced boulders and rows of blocks perched on the walls of the fan’s channels. In flat lying areas, snowmelt resulted in sparse sediment deposits with no clear structure or sorting. Observations show that the fan surface is usually protected from erosion by snow and older avalanche deposits, which provide a smooth gliding plane for new events. Within the bedrock gulley adjacent to the fan, and in the avalanche source region above, signs of abrasive wear were evident on exposed bedrock surfaces. These include rounded and scoured bedrock, fresh signs of boulder impacts, and

  15. InGaAsP Avalanche Photodetectors for Non-Gated 1.06 micrometer Photon-Counting Receivers

    Science.gov (United States)

    Itzler, Mark A.; Jiang, Xudong; Ben-Michael, Rafael; Slomkowski, Krystyna; Krainak, Michael A.

    2007-01-01

    The efficient detection of single photons at 1.06 micron is of considerable interest for lidar/ladar systems designed for remote sensing an d ranging as well as for free-space optical transmission in photon-st arved applications. However, silicon-based single photon avalanche diodes (SPADs) used at shorter wavelengths have very low single photon d etection efficiency (approximately 1 - 2%) at 1.06 micron, and InP/In GaAs SPADs designed for telecommunications wavelengths near 1.5 micro n exhibit high dark count rates that generally inhibit non-gated (free-running) operation. To bridge this "single photon detection gap" for wavelengths just beyond 1 micron, we have developed high performance , large area (80 - 200 micron diameter) InP-based InGaAsP quaternary absorber SPADs optimized for operation at 1.06 micron and based on a highly reliable planar geometry avalanche photodiode structure. We wil l show that dark count rates are sufficiently low to allow for non-ga ted operation while achieving detection efficiencies far surpassing t hose found for Si SPADs. At a detection efficiency of 10%, 80 micron diameter devices exhibit dark count rates below 1000 Hz and count rate s of at least 3 MHz when operated at -40 C. Significantly higher dete ction efficiencies (30 - 50%) are achievable with acceptable tradeoff s in dark count rate. In this paper, we will also discuss performance modeling for these devices and compare their behavior with longer wav elength InP-based InGaAs ternary absorber SPADs fabricated on a relat ed device design platform.

  16. Photodiodes based on fullerene semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Voz, C. [Micro and Nano Technology Group (MNT), Departament Enginyeria Electronica, Universitat Politecnica Catalunya, c/ Jordi Girona 1-3 Campus Nord C4, 08034-Barcelona (Spain)], E-mail: cvoz@eel.upc.edu; Puigdollers, J. [Micro and Nano Technology Group (MNT), Departament Enginyeria Electronica, Universitat Politecnica Catalunya, c/ Jordi Girona 1-3 Campus Nord C4, 08034-Barcelona (Spain); Cheylan, S. [ICFO- Institut de Ciencies Fotoniques, Mediterranean Technology Park, Av. del Canal Olimpic s/n, 08860-Castelldefels (Spain); Fonrodona, M.; Stella, M.; Andreu, J. [Solar Energy Group, Departament Fisica Aplicada i Optica, Universitat de Barcelona, Avda. Diagonal 647, 08028-Barcelona (Spain); Alcubilla, R. [Micro and Nano Technology Group (MNT), Departament Enginyeria Electronica, Universitat Politecnica Catalunya, c/ Jordi Girona 1-3 Campus Nord C4, 08034-Barcelona (Spain)

    2007-07-16

    Fullerene thin films have been deposited by thermal evaporation on glass substrates at room temperature. A comprehensive optical characterization was performed, including low-level optical absorption measured by photothermal deflection spectroscopy. The optical absorption spectrum reveals a direct bandgap of 2.3 eV and absorption bands at 2.8 and 3.6 eV, which are related to the creation of charge-transfer excitons. Various photodiodes on indium-tin-oxide coated glass substrates were also fabricated, using different metallic contacts in order to compare their respective electrical characteristics. The influence of a poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) buffer layer between the indium-tin-oxide electrode and the fullerene semiconductor is also demonstrated. These results are discussed in terms of the workfunction for each electrode. Finally, the behaviour of the external quantum efficiency is analyzed for the whole wavelength spectrum.

  17. X-ray spectroscopy with silicon pin and avalanche photo diodes

    Science.gov (United States)

    Desai, U. D.

    1992-01-01

    Results of an evaluation of silicon P-Intrinsic-N (PIN) photodiodes and Avalanche Photodiodes (APD) for the direct detection of soft x rays from 1 to 20 keV and for the detection of scintillation light output from CsI(TI) for higher x ray energies (30 to 1000 keV) are presented. About one keV resolution was achieved at room temperature for both the PIN and APD detectors for soft x rays (1 to 20 keV). Commercially available, low power (18 mV), low noise, hybrid preamplifiers, were used. These photodiodes were also coupled to CsI(TI) scintillator and obtained about 6 resolution at 662 keV. The photodiode frequency response matches well with the emission spectrum of the CsI(TI) scintillator providing good spectral resolution and a higher signal than NaI(TI) when viewed by conventional photomultipliers. A PIN-CsI(TI) combination provides a low energy threshold of around 60 keV while for the APD-CsI(TI) it is 15 keV.

  18. Response of commercial photodiodes for application in alpha spectrometry

    International Nuclear Information System (INIS)

    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 mm2, window of thickness equal or lower than 57 mg/cm2, 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)

  19. A Simple Numerical Approach To Avalanche Forecasting: Chowkibal-tangdhar Axis, Kashmir, India

    Science.gov (United States)

    Singh, Amreek; Joshi, J. C.; Ganju, Ashwagosha

    Chowkibal-Tangdhar axis of Kashmir region in India is a stretch of about 36 kms with 26 major avalanche sites. It falls in Pir Panjal range and crosses Nastachun pass cutting across Shamsabari Mountains, at an altitude of 3120m. Snow-meteorological data of 10 years recorded at two different altitude zones in the axis were statistically analyzed in the backdrop of the avalanche occurrences observed during the same period on the axis. The results show primary significance towards avalanching for certain variables e.g. fresh snow depth, snowfall rate, standing snow, water equivalent of fresh precipitation, recorded at either observatory. But for others, especially wind parameters, trend of significance is different for the two observatories. The results have also been compared with one similar study conducted for the data from Kooteny pass, British Columbia, Canada. The comparison shows a similar significance trend for most of the variables for the two areas. The attempt has also been made to identify the ranges of variables responsible for the formation of loose snow, slab, dry or wet avalanches with their avalanche size. The overall study provides an objective criterion to assess the significance of individual snow-met variables from avalanching point of view. The significance criterion thus evolved has been further implemented in the development of a simple numerical model to assess the probability, type and size of avalanching in the axis. For a particular day, the significance level of individual parameters is first determined according to the developed criterion. The average level of significance then indicates the probability of avalanching in the axis on that day. A critical limit of probability based on the data of past occurrences, helps to put that particular day in the class of avalanche or non-avalanche day. The values of the individual variables, then predict the likely nature of avalanche in terms of type and size based on the pre-identified ranges.

  20. Non-Markov property of afterpulsing effect in single-photon avalanche detector

    CERN Document Server

    Wang, Fang-Xiang; Li, Ya-Ping; He, De-Yong; Wang, Chao; Han, Yun-Guang; Wang, Shuang; Yin, Zhen-Qiang; Han, Zheng-Fu

    2016-01-01

    Single-photon avalanche photodiode(SPAD) has been widely used in researching of quantum optics. Afterpulsing effect, which is an intrinsic character of SPAD, affects the system performance in most of the experiments and needs to be carefully handled. For a long time, afterpulsing has been presumed to be determined by the pre-ignition avalanche. We studied the afterpulsing effect of a commercial InGaAs/InP SPAD (APD: Princeton Lightwave PGA-300) and demonstrated that its afterpulsing is non-Markov, which has memory effect of the avalanching history. Theoretical analysis and the experimental results clearly indicate that the embodiment of this memory effect is the afterpulsing probability, which increases as the number of ignition-avalanche pulses increase. The conclusion makes the principle of afterpulsing effect clearer and is instructive to the manufacturing processes and afterpulsing evaluation of high-count-rate SPADs. It can also be regarded as an fundamental premise to handle the afterpulsing signals in ...

  1. X-ray spectrometry with Si photodiodes

    International Nuclear Information System (INIS)

    This work envisages the development of a high resolution electromagnetic radiation spectrometry system, based on the use of low cost commercial silicon photodiodes (Siemens SFH00206 and Hamamatsu S2506-02). In order to improve the performance of these photodiodes for high resolution X-ray spectrometry, a cooling system using Peltier cells was developed to decrease the temperature of both photodiode and preamplifier's FET. The best values of the resolution for the 59.5 keV 241 Am γ-ray line, at 9 deg C, were found to be 2.10 keV and 1.82 keV for the Siemens SFH00206 and Hamamatsu S250602 photodiodes respectively. (author)

  2. Electromagnetic radiation spectrometer with Si photodiodes

    International Nuclear Information System (INIS)

    This work envisages the development of a high resolution electromagnetic radiation spectrometry system, based on the use of low cost commercial silicon photodiodes (Siemens SFH00206 and Hamamatsu S2506-02). In order to improve the performance of these photodiodes for high resolution x-ray spectrometry, a cooling system using Peltier cells was developed to decrease the temperature of both photodiode and preamplifier's FET. The best values of the resolution for the 59,5 keV 241Am γ-ray line, at 9 deg C, were found to be 2,10 keV and 1,82 keV for the Siemens SFH00206 and Hamamatsu S2506-02 photodiodes respectively. (author)

  3. Comparison of pulse height spectra on CsI(T1)/PIN photodiode radiation detector due to surface encapsulant

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Han Soo; Ha, Jang Ho; Jeong, Man Hee; Kim, Young Soo; Kim, Dong Jin; Cho, Woo Jin; Choi, Hyo Jeong [Korea Atomic Energy Research Institute, Seoul (Korea, Republic of); Cho, Seung Yeon [Environmental Health Center, Yonsei University, Seoul (Korea, Republic of)

    2014-04-15

    Scintillation crystal converts the energy deposited by an X-ray or gamma ray to light. Usually this scintillation light is collected, converted to electrons and amplified by an photomultiplier tube (PMT). The PMT has the drawbacks of being bulky and requiring a high voltage (HV) to operate it. This scinitllation light can also be collected in a solid state photo-detector, such as a silicon PIN photodiode and an avanlanche photodiode. PIN photodiode, which have 10 mm X 10 mm{sup 2} active area, were fabricated with anti-reflective coating and match with CsI(Tl) scintillator. In this study, radiation reasonabilities were compared with and without surface encapsulant epoxy. Silicon PIN Photodiodes were fabricated with AR coating. To match with CsI(Tl) scintillator, surface encapsulant was applied on the PIN photodiodes. Leakage currents for all the PIN photodiodes show several nA up to 100 V. The pulse height spectra and comparison of the CsI(Tl)PIN photodiode in case of surface encapsulation on PIN photodiode will be presented at the conference.

  4. Geometrical properties of avalanches in self-organized critical models of solar flares

    International Nuclear Information System (INIS)

    We investigate the geometrical properties of avalanches in self-organized critical models of solar flares. Traditionally, such models differ from the classical sandpile model in their formulation of stability criteria in terms of the curvature of the nodal field, and belong to a distinct universality class. With a view toward comparing these properties to those inferred from spatially and temporally resolved flare observations, we consider the properties of avalanche peak snapshots, time-integrated avalanches in two and three dimensions, and the two-dimensional projections of the latter. The nature of the relationship between the avalanching volume and its projected area is an issue of particular interest in the solar flare context. Using our simulation results we investigate this relationship, and demonstrate that proper accounting of the fractal nature of avalanches can bring into agreement hitherto discrepant results of observational analyses based on simple, nonfractal geometries for the flaring volume

  5. Airborne Geiger-Mode LiDAR for Large-Scale, High-Resolution Wide-Area Mapping . GI_Forum|GI_Forum 2016, Volume 1 – open:spatial:interfaces|

    OpenAIRE

    Smith, Philip; Bahr, Thomas

    2016-01-01

    This presentation describes a new solution for geospatial Geiger-mode Avalanche Photodiode (GmAPD) LiDAR – a suite of sensors, processing tools and analytics born from a 15-year GmAPD legacy within certain DoD environments that will bring a significant increase in production efficiency to the commercial market. The objective of the sensor design was to support USGS LiDAR Quality Level 1 (and higher) data production over large areas from pressurized, fixed-wing aircrafts flying at altitudes of...

  6. 3D Camera Based on Gain-Modulated CMOS Avalanche Photodiodes

    OpenAIRE

    Shcherbakova, Olga

    2013-01-01

    In the last several years, both scientific and industrial community have shown an increasing interest in range imaging due to its potential use in various application domains such as robotics, vehicle safety, gaming, mobile applications as well as many others. Among the diversity of techniques available for range detection, Time-of-Flight (TOF) offers advantages in terms of compact system realization, good performance and low required computational power. Recent works have shown a trend towar...

  7. Feasibility of Geiger-mode avalanche photodiodes in CMOS standard technologies for tracker detectors

    OpenAIRE

    Vilella Figueras, Eva

    2013-01-01

    The next generation of particle colliders will be characterized by linear lepton colliders, where the collisions between electrons and positrons will allow to study in great detail the new particle discovered at CERN in 2012 (presumably the Higgs boson). At present time, there are two alternative projects underway, namely the ILC (International Linear Collider) and CLIC (Compact LInear Collider). From the detector point of view, the physics aims at these particle colliders impose such extreme...

  8. Maximum detection range limitation of pulse laser radar with Geiger-mode avalanche photodiode array

    Science.gov (United States)

    Luo, Hanjun; Xu, Benlian; Xu, Huigang; Chen, Jingbo; Fu, Yadan

    2015-05-01

    When designing and evaluating the performance of laser radar system, maximum detection range achievable is an essential parameter. The purpose of this paper is to propose a theoretical model of maximum detection range for simulating the Geiger-mode laser radar's ranging performance. Based on the laser radar equation and the requirement of the minimum acceptable detection probability, and assuming the primary electrons triggered by the echo photons obey Poisson statistics, the maximum range theoretical model is established. By using the system design parameters, the influence of five main factors, namely emitted pulse energy, noise, echo position, atmospheric attenuation coefficient, and target reflectivity on the maximum detection range are investigated. The results show that stronger emitted pulse energy, lower noise level, more front echo position in the range gate, higher atmospheric attenuation coefficient, and higher target reflectivity can result in greater maximum detection range. It is also shown that it's important to select the minimum acceptable detection probability, which is equivalent to the system signal-to-noise ratio for producing greater maximum detection range and lower false-alarm probability.

  9. Passive Quenching Electronics for Geiger Mode 4H-SiC Avalanche Photodiodes

    Science.gov (United States)

    Liu, Fei; Zhou, Dong; Lu, Hai; Chen, Dun-Jun; Ren, Fang-Fang; Zhang, Rong; Zheng, You-Dou

    2015-12-01

    Not Available Supported by the National Basic Research Program of China under Grant Nos 2011CB301900 and 2011CB922100, and the Priority Academic Program Development of Jiangsu Higher Education Institutions.

  10. High Sensitivity Indium Phosphide Based Avalanche Photodiode Focal Plane Arrays Project

    Data.gov (United States)

    National Aeronautics and Space Administration — nLight has demonstrated highly-uniform APD arrays based on the highly sensitive InGaAs/InP material system. These results provide great promise for achieving the...

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

    Science.gov (United States)

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

    2016-03-01

    Not Available Supported by the Chinese Academy of Sciences Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, Shanghai Branch, University of Science and Technology of China, and the National Natural Science Foundation of China under Grant No 11405172.

  12. High-Performance, Radiation-Hard, 2-D, Near-Infrared, Avalanche Photodiode Arrays Project

    Data.gov (United States)

    National Aeronautics and Space Administration — AdTech Photonics, in collaboration with the Center for Advanced Studies in Photonics Research (CASPR) at UMBC, is pleased to submit this Phase II proposal entitled...

  13. Single Photon Sensitive HgCdTe Avalanche Photodiode Detector (APD) Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Leveraging Phase I SBIR successes, in Phase II, a single photon sensitive LIDAR receiver will be fabricated and delivered to NASA. In Phase I, high-gain,...

  14. High Performance Avalanche Photodiodes for Photon Counting at 1064 nm Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The need for higher performance fiber optic telecommunications receivers has provided the impetus for substantial progress during the last decade in the...

  15. High Sensitivity Indium Phosphide Based Avalanche Photodiode Focal Plane Arrays Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to build a monolithically integrated FPA of densely packed APDs (70-um pitch) operating at or around 1500 nm wavelength that is suitable for the...

  16. High-Performance, Radiation-Hard, 2-D, Near-Infrared, Avalanche Photodiode Arrays Project

    Data.gov (United States)

    National Aeronautics and Space Administration — In this STTR project we will address the radiation hardness issues using radiation hard (RH) materials. We will based on the RH material to develop our photon...

  17. Neuronal avalanches and brain plasticity

    Science.gov (United States)

    de Arcangelis, L.; Herrmann, H. J.; Perrone-Capano, C.

    2007-12-01

    Networks of living neurons exhibit an avalanche mode of activity, experimentally found in organotypic cultures. Moreover, experimental studies of morphology indicate that neurons develop a network of small-world-like connections, with the possibility of a very high connectivity degree. Here we discuss a recent model based on self-organized criticality, which consists of an electrical network with threshold firing and activity-dependent synapse strengths. The model is implemented on regular and small world lattices and on a scale-free network, the Apollonian network. The system exhibits an avalanche activity with a power law distribution of sizes and durations. The analysis of the power spectra of the electrical signal reproduces very robustly the power law behaviour with the exponent 0.8, experimentally measured in electroencephalogram (EEG) spectra. The exponents are found to be quite stable with respect to initial configurations and strength of plastic remodelling, indicating that universality holds for a wide class of neural network models.

  18. Supersensitive avalanche silicon drift photodetector

    International Nuclear Information System (INIS)

    Physical principles of performance and main characteristics of a novel avalanche photodetector developed on the basis of MOS (metal-oxide-silicon) technology are presented. The photodetector contains a semitransparent gate electrode and a drain contact to provide a drift of multiplied charge carriers along the semiconductor surface. A high gain (more than 104) of the photocurrent was achieved due to the local negative feedback effect realized on the Si -- SiO2 boundary. Special attention is paid to the possibilities of the development of a supersensitive avalanche CCD (charge-coupled device) for the detection of individual photons in visible and ultraviolet spectral regions. The experimental results obtained with a two-element CCD prototype are discussed. (author)

  19. Avalanches, Scaling and Coherent Noise

    OpenAIRE

    Newman, M. E. J.; Sneppen, Kim

    1996-01-01

    We present a simple model of a dynamical system driven by externally-imposed coherent noise. Although the system never becomes critical in the sense of possessing spatial correlations of arbitrarily long range, it does organize into a stationary state characterized by avalanches with a power-law size distribution. We explain the behavior of the model within a time-averaged approximation, and discuss its potential connection to the dynamics of earthquakes, the Gutenberg-Richter law, and to rec...

  20. Avalanche ecology and large magnitude avalanche events: Glacier National Park, Montana, USA

    Science.gov (United States)

    Fagre, Daniel B.; Peitzsch, Erich H.

    2010-01-01

    Large magnitude snow avalanches play an important role ecologically in terms of wildlife habitat, vegetation diversity, and sediment transport within a watershed. Ecological effects from these infrequent avalanches can last for decades. Understanding the frequency of such large magnitude avalanches is also critical to avalanche forecasting for the Going-to-the-Sun Road (GTSR). In January 2009, a large magnitude avalanche cycle occurred in and around Glacier National Park, Montana. The study site is the Little Granite avalanche path located along the GTSR. The study is designed to quantify change in vegetative cover immediately after a large magnitude event and document ecological response over a multi-year period. GPS field mapping was completed to determine the redefined perimeter of the avalanche path. Vegetation was inventoried using modified U.S. Forest Service Forest Inventory and Analysis plots, cross sections were taken from over 100 dead trees throughout the avalanche path, and an avalanche chronology was developed. Initial results indicate that the perimeter of this path was expanded by 30%. The avalanche travelled approximately 1200 vertical meters and 3 linear kilometers. Stands of large conifers as old as 150 years were decimated by the avalanche, causing a shift in dominant vegetation types in many parts of the avalanche path. Woody debris is a major ground cover up to 3 m in depth on lower portions of the avalanche path and will likely affect tree regrowth. Monitoring and measuring the post-avalanche vegetation recovery of this particular avalanche path provides a unique dataset for determining the ecological role of avalanches in mountain landscapes.

  1. Avalanche Dynamics in Wet Granular Materials

    OpenAIRE

    Tegzes, P.; Vicsek, T.; P. Schiffer

    2002-01-01

    We have studied the dynamics of avalanching wet granular media in a rotating drum apparatus. Quantitative measurements of the flow velocity and the granular flux during avalanches allow us to characterize novel avalanche types unique to wet media. We also explore the details of viscoplastic flow (observed at the highest liquid contents) in which there are lasting contacts during flow, leading to coherence across the entire sample. This coherence leads to a velocity independent flow depth at h...

  2. Effect of temperature on silicon PIN photodiode radiation detector

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Han Soo; Jeong, Man Hee; Kim, Young Soo; HA, Jang Ho [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Cho, Seong Yeon [Yonsei University, Wonju (Korea, Republic of)

    2014-03-15

    One of the noise sources of a semiconductor radiation detector is thermal noise, which degrades the performance, such as the energy resolution and unexpected random pulse signals. In this study, PIN photodiode radiation detectors, with different active areas were designed and fabricated for an experimental comparison of the energy resolutions for different temperatures and capacitances by using a Ba-133 calibration gamma-ray source. The experimental temperature was approximately in the range from -7 to 24 .deg. C and was controlled by using a peltier device. The design considerations and the electrical characteristics, such as the I-V and the C-V characteristics, are also addressed.

  3. Landsat Thematic Mapper observations of debris avalanche deposits in the Central Andes

    Science.gov (United States)

    Francis, P. W.; Wells, G. L.

    1988-01-01

    Remote sensing with the Landsat Thematic Mapper of debris avalanche deposits in the Central Andes between 18 and 27 deg S revealed, for the first time, the presence of 28 breached volcanic cones and 11 major volcanic debris avalanche deposits, several of which cover areas in excess of 100 sq km. It is concluded that such avalanche deposits are normal products of the evolution of large composite volcanoes, comparable with lava and pyroclastic flow deposits. A statistical survey of 578 composite volcanoes in the same area indicated that a majority of cones which achieve edifice heights between 2000 and 3000 m may undergo sector collapse. The paper describes morphological criteria for identifying breached composite cones and volcanic debris avalanches using orbital images.

  4. Application of a New Rheological Model to Rock Avalanches: An SPH Approach

    Science.gov (United States)

    Manzanal, D.; Drempetic, V.; Haddad, B.; Pastor, M.; Martin Stickle, M.; Mira, P.

    2016-06-01

    Rock avalanches move large volumes of material causing a highly destructive power over large areas. In these events, it is possible to monitor the evolution of slopes but failure cannot be always prevented. For this reason, modelling of the propagation phase provides engineers with fundamental information regarding speed, track, runout and depth. From these data, it is possible to perform a better risk assessment and propose mitigation measures to reduce the potential hazard of specific area. The purpose of this paper is to present a depth integrated, SPH model, which can be used to simulate real rock avalanches and to assess the influence of the rheology on the avalanche properties. The paper compares the performance of different rheological models to reproduce the track, runout and depth of the final deposit for both, scale test and real events such as Frank and Thurwiesier rock avalanches. These sets of benchmarks provide information on the proposed model accuracy and limitations.

  5. Photodiode and photomultiplier areal sensitivity anomalies

    Science.gov (United States)

    Youngbluth, O., Jr.

    1977-01-01

    Several silicon photodiodes and photomultipliers were tested to determine signal variations as a light spot was scanned over the photosensitive surface of these detectors. Qualitative and quantitative data is presented to demonstrate the areal sensitivity anomalies. These anomalies are related back to the fabrication techniques of the manufacturers.

  6. Production networks and failure avalanches

    CERN Document Server

    Weisbuch, G; Weisbuch, Gerard; Battiston, Stefano

    2005-01-01

    Although standard economics textbooks are seldom interested in production networks, modern economies are more and more based upon suppliers/customers interactions. One can consider entire sectors of the economy as generalised supply chains. We will take this view in the present paper and study under which conditions local failures to produce or simply to deliver can result in avalanches of shortage and bankruptcies across the network. We will show that a large class of models exhibit scale free distributions of production and wealth among firms and that metastable regions of high production are highly localised.

  7. 4H-SiC Schottky photodiodes for ultraviolet flame detection

    Science.gov (United States)

    Mazzillo, M.; Sciuto, A.

    2015-10-01

    In the last few years silicon carbide (SiC) has emerged as an appropriate material for the detection of very low ultraviolet photon fluxes even at elevated temperatures. In this paper we report on the electro-optical characteristics of large area interdigit Ni2Si/4H-SiC photodiodes in TO metal can package with a suitable molded cap quartz window with high transmission in the ultraviolet wavelength range. The detectors have been tested for the detection of the ultraviolet component of the yellow flame emitted by a small candle, showing good sensitivity for very weak photon fluxes notwithstanding the linear operation condition of the photodiodes.

  8. 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.

  9. Performance of a-Si:H photodiode technology-based advanced CMOS active pixel sensor imagers

    Science.gov (United States)

    Theil, Jeremy A.; Haddad, Homayoon; Snyder, Rick D.; Zelman, Mike; Hula, David; Lindahl, Kirk A.

    2001-12-01

    Amorphous silicon photodiode technology is a very attractive option for image array integrated circuits because it enables large die-size reduction and higher light collection efficiency than c-Si arrays. The concept behind the technology is to place the photosensing element directly above the rest of the circuit, thus eliminating the need to make areal tradeoffs between photodiode and pixel circuit. We have developed an photodiode array technology that is fully compatible with a 0.35 um CMOS process to produce image sensors arrays with 10-bit dynamic range that are 30% smaller than comparable c-Si photodiode arrays. The work presented here will discuss performance issues and solutions to lend itself to cost-effective high-volume manufacturing. The various methods of interconnection of the diode to the array and their advantages will be presented. The effect of doped layer thickness and concentration on quantum efficiency, and the effect of a-Si:H defect concentration on diode performance will be discussed. The photodiode dark leakage current density is about 80 pA/cm2, and its absolute quantum efficiency peaks about 85% at 550 nm. These sensors have 50% higher sensitivity, and 2x lower dark current when compared to bulk silicon sensors of the same design. The cell utilizes a 3 FET design, but allows for 100% photodiode area due to the elevated nature of the design. The VGA (640 X 480), array demonstrated here uses common intrinsic and p-type contact layers, and makes reliable contact to those layers by use of a monolithic transparent conductor strap tied to vias in the interconnect.

  10. Temporal correlations in neuronal avalanche occurrence

    Science.gov (United States)

    Lombardi, F.; Herrmann, H. J.; Plenz, D.; de Arcangelis, L.

    2016-04-01

    Ongoing cortical activity consists of sequences of synchronized bursts, named neuronal avalanches, whose size and duration are power law distributed. These features have been observed in a variety of systems and conditions, at all spatial scales, supporting scale invariance, universality and therefore criticality. However, the mechanisms leading to burst triggering, as well as the relationship between bursts and quiescence, are still unclear. The analysis of temporal correlations constitutes a major step towards a deeper understanding of burst dynamics. Here, we investigate the relation between avalanche sizes and quiet times, as well as between sizes of consecutive avalanches recorded in cortex slice cultures. We show that quiet times depend on the size of preceding avalanches and, at the same time, influence the size of the following one. Moreover we evidence that sizes of consecutive avalanches are correlated. In particular, we show that an avalanche tends to be larger or smaller than the following one for short or long time separation, respectively. Our analysis represents the first attempt to provide a quantitative estimate of correlations between activity and quiescence in the framework of neuronal avalanches and will help to enlighten the mechanisms underlying spontaneous activity.

  11. Spatial aspects of vulnerability and risk resulting from snow avalanches

    Science.gov (United States)

    Fuchs, S.; Koltermann, P.; Sokratov, S.; Seliverstov, Y.; Shnyparkov, A.

    2012-04-01

    Mountain regions provide a significant proportion of areas used for human settlements, economic purpose, and recreation. Simultaneously, due to steep vertical gradients mountain areas are prone to mass movement processes. The intersection of such processes with areas used by human action turns them into hazards. In particular in arctic regions, which show a greater susceptibility to disturbances than many landscapes, considerable efforts have been undertaken in recent decades to reduce the adverse effects of mountain hazards. The concept of risk supplemented the traditional engineering approaches of technical mitigation since the 1990s to comprehensively manage these threats, and to develop strategies for a sustainable use of these areas. The concept of risk is based on a mathematical combination of hazards and consequences, but is static over time. However, three major dynamic systems interact in the field of mountain hazard risk management: the physical environment, which includes hazardous events; the social and demographic characteristics of the communities that experience them; and the values at risk such as buildings, roads, and other components of the built environment. These dynamics have not sufficiently been taken into account so far in natural hazard risk management, in particular with respect to industrialised artic regions. Within the city of Kirovsk, Kola Peninsula, Russian Federation, these dynamics were assessed by taking snow avalanche risk as an example. The test site is exposed to multiple avalanche tracks with repeated releases during individual winter seasons, endangering the built environment and any kind of infrastructure lines. The aim was to contribute to the development of a spatial risk model for mountain regions on different temporal scales. The spatial characteristics of the long-term avalanche risk, as a result of the evolution of the built environment, was analysed on an annual as well as inter-annual level. This long-term development

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

    Directory of Open Access Journals (Sweden)

    Tiago L Ribeiro

    Full Text Available BACKGROUND: 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. METHODOLOGY/PRINCIPAL FINDINGS: 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. CONCLUSIONS

  13. Monitoring of full-depth avalanches contaminated by soil and rocks - their origin and consequences, (Krkonose/Karkonosze Mts.- High Sudetes)

    Science.gov (United States)

    Kocianova, M.

    2009-04-01

    Monitoring of full-depth avalanches contaminated by soil and rocks - their origin and consequences, (Krkonose/Karkonosze Mts.- High Sudetes) Milena Kocianova Valerian Spusta, Irena Spatenkova, Alena Tondrova, Igor Jan Dvorak, Vlastimil Pilous Krkonoše National Park Administration, Dobrovskeho 3, 543 01 Vrchlabi, Czech republic Monitoring of snow avalanches is provided in Czech part of the Krkonose/Karkonosze Mountains since the winter season 1961/62. The full-depth avalanches contaminated by soil and rocks represent about 4% of the monitored number. There are six bigger avalanches of this type recorded during last 10 years. The areas of snutched weathering mantles reached at about 3000 - 23 000 m2 per individual avalanche track. In deposit zones the areas from 2600 to 18700 m2 were covered by soil, sods and small rock fragments whose volume ranged from about 130 to 880 m3 per individual avalanche track. The volume of large rock fragments in one concrete track was counted up to 144 m3. The great influence of full depth avalanches on relief and slope development is evident. Based on monitoring the speed of snutched areas overgrowing by vegetation and on comparison of space design of plant communities out off and on the avalanche tracks respectively, it would be possible to estimate the period of such bigger events. Very important thing is that four avalanche events were triggered by water, which infiltrated the base of snowpack within upper or central parts of avalanche slopes. Water origin was probably either a) in mires on adjacent summit plateau (ground water flown on inclined bedrock layers to the avalanche slopes) and b) in thawing water of snow patches situated on the cryoplanation terraces above the avalanche slopes. More detailed study of these phenomena is needed in the future.

  14. Cartographic modeling of snow avalanche path location within Glacier National Park, Montana

    Science.gov (United States)

    Walsh, Stephen J.; Brown, Daniel G.; Bian, Ling; Butler, David R.

    1990-01-01

    Geographic information system (GIS) techniques were applied to the study of snow-avalanche path location within Glacier National Park, Montana. Aerial photointerpretation and field surveys confirmed the location of 121 avalanche paths within the selected study area. Spatial and nonspatial information on each path were integrated using the ARC/INFO GIS. Lithologic, structural, hydrographic, topographic, and land-cover impacts on path location were analyzed. All path frequencies within variable classes were normalized by the area of class occurrence relative to the total area of the study area and were added to the morphometric information contained within INFO tables. The normalized values for each GIS coverage were used to cartographically model, by means of composite factor weightings, avalanche path locations.

  15. Cartographic modeling of snow avalanche path location within Glacier National Park, Montana

    Science.gov (United States)

    Walsh, Stephen J.; Brown, Daniel G.; Bian, Ling; Butler, David R.

    1990-05-01

    Geographic information system (GIS) techniques were applied to the study of snow-avalanche path location within Glacier National Park, Montana. Aerial photointerpretation and field surveys confirmed the location of 121 avalanche paths within the selected study area. Spatial and nonspatial information on each path were integrated using the ARC/INFO GIS. Lithologic, structural, hydrographic, topographic, and land-cover impacts on path location were analyzed. All path frequencies within variable classes were normalized by the area of class occurrence relative to the total area of the study area and were added to the morphometric information contained within INFO tables. The normalized values for each GIS coverage were used to cartographically model, by means of composite factor weightings, avalanche path locations.

  16. Silicon photodiode as the two-color detector

    Science.gov (United States)

    Ponomarev, D. B.; Zakharenko, V. A.

    2015-11-01

    This paper describes a silicon photodiode as the two-color photodetector. The work of one photodiode in two spectral ranges is achieved due to the changes of the spectral sensitivity of the photodiodes in the transition from photodiode mode for photovoltaic in the short circuit mode. On the basis of silicon photodiode FD-256 the layout of the spectral ratio pyrometer was assembled and the results of theoretical calculations was confirmed experimentally. The calculated dependences of the coefficient of error of the spectral ratio pyrometer from temperature reverse voltage 10 and 100 V was presented. The calculated dependence of the instrumental error and the assessment of methodological errors of the proposed photodetector spectral ratio was done. According to the results of the presented research was set the task of development photodiode detectors which change the spectral sensitivity depending on the applied voltage.

  17. Differences of silicon photodiode spectral reflectance among the same batch

    Institute of Scientific and Technical Information of China (English)

    A.L.Mu(n)oz Zurita; J.Campos Acosta; A.Pons Aglio; A.Shcherbakov

    2008-01-01

    Photodiode's reflectance plays an important role regarding the relation between responsivity and the incident flux. In this work we analyze how the spectral reflectance changes among photodiodes from the same manufacturer and batch and how the reflectance of three standard photodiodes has drifted during six years. The results show that the reflectance changes from diode to diode within the same batch and also show th.at the reflectance ofphotodiodes changes on time. This ageing is spectrally dependent.

  18. 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.

  19. Avalanche Hazard Mapping with Satellite Data and a Digital Elevation Model

    Directory of Open Access Journals (Sweden)

    Urs Gruber

    1995-04-01

    Full Text Available Today avalanche hazard mapping is a very time-consuming affair. To map large remote areas, a method based on satellite imagery and digital elevation model has been developed. For this purpose, two test-sites in the Swiss Apls were selected. To simulate the avalanche hazard, the existing Salm-Voellmy model was modified to the computer environment and extended to the characteristics of avalanches within forested terrain. The forests were classified with Landsat-TM data. So far, only a single forest-class was established. The separation of forest, shrub, and non-forested area along the timberline poses a problem. On the other hand, a classification of small openings and avalanche tracks within the forest could be achieved. A comparison with the existing avalanche cadastral map revealed that 85 per cent of the risk areas were correctly classified. On the other hand, the separation into the defined red and blue danger zones was not satisfactory. For the model's application to become operational, further improvements are needed. However, the general approach is very promising, and should lead to more reliable hazard maps for planning purposes, as well as to new and better insights into the mutual effects between snow and forest.

  20. A Real Two-Phase Mechanical Model for Rock-Ice Avalanches

    Science.gov (United States)

    Pudasaini, S. P.; Krautblatter, M.

    2012-04-01

    gradients and the virtual mass. The source in the solid momentum includes gravity, the Coulomb friction, slope gradient, buoyancy, and the generalized drag. The source term for the fluid momentum includes gravity, fluid pressure and topographic gradients, enhanced non-Newtonian viscous stresses, and the drag. There are strong couplings between the solid and fluid momentum transfer. The new enhanced two-phase model can better explain dynamically changing frictional properties of rock-ice avalanches that occur internally and along the flow path. Both mass and momentum exchanges allow for a much more realistic simulation, especially during the critical initial and final stages of avalanche propagation. Benchmark numerical simulations demonstrate that the dynamics of permafrost rock-ice avalanche is fundamentally different form that of pure rock avalanches. The model simulations reveal special features of rock-ice avalanche propagation form and dynamics, similar to those observed, e.g., in the 2007 Bliggspitze rock-ice avalanche event. Numerical results also reveal that mass and momentum exchange between the phases and the associated internal and basal strength weakening offer a new explanation for the exceptionally long run-out distances leading to higher flow mobility typical for high-mountain rock-ice avalanches. These new results substantially improve modelling run-out distances and inundation areas, and could significantly contribute to hazard prediction and mitigation in high-mountain permafrost environments. Here we show that the new two-phase rock-ice avalanche model can yield a novel and enhanced representation of multiple processes that lead to the high and changing mobility of rock-ice-avalanches.

  1. Combined performance of photodiode matrices with electron-optical converters

    International Nuclear Information System (INIS)

    As applied to plasma diagnostics using the methods of laser scattering, a necessity to use an electron-optical converter aheat of photodiode matrices is pointed out. Investigation results of the MF-16 integrated photodiode matrix performance in combination with various electron-optical convertes are presented. The possibility to use the system for recording weak pulse optical signals is shown

  2. Advances in Cryogenic Avalanche Detectors (review)

    CERN Document Server

    Buzulutskov, A

    2011-01-01

    Cryogenic Avalanche Detectors (CRADs) are referred to as a new class of noble-gas detectors operated at cryogenic temperatures with electron avalanching performed directly in the detection medium, the latter being in gaseous, liquid or two-phase (liquid-gas) state. Electron avalanching is provided by Micro-Pattern Gas Detector (MPGD) multipliers, in particular GEMs and THGEMs, operated at cryogenic temperatures in dense noble gases. The final goal for this kind of detectors is the development of large-volume detectors of ultimate sensitivity for rare-event experiments and medical applications, such as coherent neutrino-nucleus scattering, direct dark matter search, astrophysical (solar and supernova) neutrino detection experiments and Positron Emission Tomography technique. This review is the first attempt to summarize the results on CRAD performances obtained by different groups. A brief overview of the available CRAD concepts is also given and the most remarkable CRAD physics effects are discussed.

  3. Maximal avalanches in the Bak-Sneppen model

    OpenAIRE

    Gillett, Alexis; Meester, Ronald; van der Wal, Peter

    2006-01-01

    We study the durations of the avalanches in the maximal avalanche decomposition of the Bak-Sneppen evolution model. We show that all the avalanches in this maximal decomposition have infinite expectation, but only `barely', in the sense that if we made the appropriate threshold a tiny amount smaller (in a certain sense), then the avalanches would have finite expectation. The first of these results is somewhat surprising, since simulations suggest finite expectations.

  4. Relating rock avalanche morphology to emplacement processes

    Science.gov (United States)

    Dufresne, Anja; Prager, Christoph; Bösmeier, Annette

    2015-04-01

    The morphology, structure and sedimentological characteristics of rock avalanche deposits reflect both internal emplacement processes and external influences, such as runout path characteristics. The latter is mainly predisposed by topography, substrate types, and hydrogeological conditions. Additionally, the geological setting at the source slope controls, e.g. the spatial distribution of accumulated lithologies and hence material property-related changes in morphology, or the maximum clast size and amount of fines of different lithological units. The Holocene Tschirgant rock avalanche (Tyrol, Austria) resulted from failure of an intensely deformed carbonate rock mass on the southeast face of a 2,370-m-high mountain ridge. The initially sliding rock mass rapidly fragmented as it moved towards the floor of the Inn River valley. Part of the 200-250 x 106 m3 (Patzelt 2012) rock avalanche debris collided with and moved around an opposing bedrock ridge and flowed into the Ötz valley, reaching up to 6.3 km from source. Where the Tschirgant rock avalanche spread freely it formed longitudinal ridges aligned along motion direction as well as smaller hummocks. Encountering high topography, it left runup ridges, fallback patterns (i.e. secondary collapse), and compressional morphology (successively elevated, transverse ridges). Further evidence for the mechanical landslide behaviour is given by large volumes of mobilized valley-fill sediments (polymict gravels and sands). These sediments indicate both shearing and compressional faulting within the rock avalanche mass (forming their own morphological units through, e.g. in situ bulldozing or as distinctly different hummocky terrain), but also indicate extension of the spreading landslide mass (i.e. intercalated/injected gravels encountered mainly in morphological depressions between hummocks). Further influences on its morphology are given by the different lithological units. E.g. the transition from massive dolomite

  5. Full-depth avalanches and soil erosion: an experimental site in NW Italy

    Science.gov (United States)

    Ceaglio, Elisabetta; Freppaz, Michele; Maggioni, Margherita; Filippa, Gianluca; Godone, Danilo; Zanini, Ermanno

    2010-05-01

    In the future the combined effect of changes in climate and land use could contribute to the intensification of soil erosion, related to snowpack movements as snow gliding and full-depth avalanches. Often, with particular meteorological conditions, the snow movement along a slope is associated with erosion and transport of the upper soil horizons, with the release of significant amount of material in the runout zone. Moreover the chemical composition of the snow in the deposition zone is usually different from the snow in the starting zone, revealing a potential release of ionic species mainly by the organic debris transported by the avalanche itself. The aim of this work is to characterize the quantity and quality of the material released by full-depth avalanches in the deposition zone. The study area is located in Aosta Valley (NW-Italy), on a SW exposed avalanche path, running from 2000 m a.s.l. of the triggering zone to 1200 m a.s.l. of the deposition zone. At this site, snow gliding and glide cracks, generally followed by full-depth avalanches, have been frequently observed. In the starting area, two plots located at the same elevation, slope and aspect, but with different soil moisture content, are equipped with moisture and temperature sensors, located at different depth in the soil, at the snow-soil interface and in the basal snowpack layer, and with glide shoes. The recorded data are related to the snow physical properties, measured by periodical investigations. In the deposition area, after a full-depth avalanche event occurred in March 2009, the mixed material was collected through snow avalanche coring, and a snow pit was dug in the deposit, in order to evaluate the quantity and the distribution of the material transported by the avalanche. First results show that the average density of the snow in the deposition zone was 624 kg m-3. The solid material was distributed mainly in the upper 5 cm of the avalanche deposit, with a mean concentration of the

  6. Metal frame as local protection of superconducting films from thermomagnetic avalanches

    Science.gov (United States)

    Mikheenko, P.; Vestgârden, J. I.; Chaudhuri, S.; Maasilta, I. J.; Galperin, Y. M.; Johansen, T. H.

    2016-03-01

    Thermomagnetic avalanches in superconducting films propagating extremely fast while forming unpredictable patterns, represent a serious threat for the performance of devices based on such materials. It is shown here that a normal-metal frame surrounding a selected region inside the film area can provide efficient protection from the avalanches during their propagation stage. Protective behavior is confirmed by magneto-optical imaging experiments on NbN films equipped with Cu and Al frames, and also by performing numerical simulations. Experimentally, it is found that while conventional flux creep is not affected by the frames, the dendritic avalanches are partially or fully screened by them. The level of screening depends on the ratio of the sheet conductance of the metal and the superconductor in the resistive state, and for ratios much larger than unity the screening is very efficient.

  7. Metal frame as local protection of superconducting films from thermomagnetic avalanches

    Directory of Open Access Journals (Sweden)

    P. Mikheenko

    2016-03-01

    Full Text Available Thermomagnetic avalanches in superconducting films propagating extremely fast while forming unpredictable patterns, represent a serious threat for the performance of devices based on such materials. It is shown here that a normal-metal frame surrounding a selected region inside the film area can provide efficient protection from the avalanches during their propagation stage. Protective behavior is confirmed by magneto-optical imaging experiments on NbN films equipped with Cu and Al frames, and also by performing numerical simulations. Experimentally, it is found that while conventional flux creep is not affected by the frames, the dendritic avalanches are partially or fully screened by them. The level of screening depends on the ratio of the sheet conductance of the metal and the superconductor in the resistive state, and for ratios much larger than unity the screening is very efficient.

  8. Ground-based LiDAR integration with avalanche control operations: target planning and assessment of control effectiveness

    Science.gov (United States)

    Deems, J. S.; LeWinter, A.; Gadomski, P. J.; Finnegan, D. C.

    2015-12-01

    The varying distribution of snow depth in avalanche starting zones exerts a strong influence on avalanche potential and character. Extreme depth changes over short distances are common, especially in wind-affected, above-treeline environments. Snow depth also affects the ease of avalanche triggering. Experience shows that avalanche reduction efforts are often more successful when targeting shallow trigger point areas near deeper slabs with explosives or ski cutting. We are exploring the use of high resolution snow depth and depth change maps from differential LiDAR scans to quantify loading patterns for use in both pre-control planning and in post-control assessment. We present results from our ongoing work at the Arapahoe Basin and Aspen Highlands ski areas in Colorado, USA, and from a new collaboration with the Colorado Department of Transportation. At Arapahoe Basin we have tested rapid snow depth product generation for use in planning placement of explosives for artificial avalanche triggering. At Aspen Highlands we have explored measurement of minimum disturbance depth from bootpacking. In a new application, we are assessing avalanche hazard reduction with new Gazex exploder arrays on Loveland and Berthoud Passes.

  9. Design and TCAD simulation of double-sided pixelated low gain avalanche detectors

    Energy Technology Data Exchange (ETDEWEB)

    Dalla Betta, Gian-Franco, E-mail: gianfranco.dallabetta@unitn.it [Dipartimento di Ingegneria Industriale, Università di Trento, Via Sommarive 9, 38123 Trento (Italy); TIFPA INFN, Via Sommarive 14, 38123 Trento (Italy); Pancheri, Lucio [Dipartimento di Ingegneria Industriale, Università di Trento, Via Sommarive 9, 38123 Trento (Italy); TIFPA INFN, Via Sommarive 14, 38123 Trento (Italy); Boscardin, Maurizio [Fondazione Bruno Kessler, Via Sommarive 18, 38123 Trento (Italy); TIFPA INFN, Via Sommarive 14, 38123 Trento (Italy); Paternoster, Giovanni [Fondazione Bruno Kessler, Via Sommarive 18, 38123 Trento (Italy); Piemonte, Claudio [Fondazione Bruno Kessler, Via Sommarive 18, 38123 Trento (Italy); TIFPA INFN, Via Sommarive 14, 38123 Trento (Italy); Cartiglia, Nicolo; Cenna, Francesca [INFN Sezione di Torino, Via P. Giuria 2, 10125 Torino (Italy); Bruzzi, Mara [Dipartimento di FIsica e Astronomia, Università di Firenze, and INFN Sezione di Firenze, Via Giovanni Sansone 1, 50019 Sesto Fiorentino (Italy)

    2015-10-01

    We introduce a double-sided variant of low gain avalanche detector, suitable for pixel arrays without dead-area in between the different read-out elements. TCAD simulations were used to validate the device concept and predict its performance. Different design options and selected simulation results are presented, along with the proposed fabrication process.

  10. X-ray imager using solution processed organic transistor arrays and bulk heterojunction photodiodes on thin, flexible plastic substrate

    NARCIS (Netherlands)

    Gelinck, G.H.; Kumar, A.; Moet, D.; Steen, J.L. van der; Shafique, U.; Malinowski, P.E.; Myny, K.; Rand, B.P.; Simon, M.; Rütten, W.; Douglas, A.; Jorritsma, J.; Heremans, P.L.; Andriessen, H.A.J.M.

    2013-01-01

    We describe the fabrication and characterization of large-area active-matrix X-ray/photodetector array of high quality using organic photodiodes and organic transistors. All layers with the exception of the electrodes are solution processed. Because it is processed on a very thin plastic substrate o

  11. Avalanches in a Bose-Einstein condensate

    OpenAIRE

    Schuster, J; A. Marte; Amtage, S; Sang, B.; Rempe, G.; Beijerinck, HCW Herman

    2001-01-01

    Collisional avalanches are identified to be responsible for an 8-fold increase of the initial loss rate of a large 87-Rb condensate. We show that the collisional opacity of an ultra-cold gas exhibits a critical value. When exceeded, losses due to inelastic collisions are substantially enhanced. Under these circumstances, reaching the hydrodynamic regime in conventional BEC experiments is highly questionable.

  12. Characterization of Al0.8Ga0.2As geiger photodiode

    Science.gov (United States)

    Chen, X. J.; Ren, Min; Chen, Yaojia; Johnson, E. B.; Campbell, Joe C.; Christian, James F.

    2015-08-01

    Solid-state photomultipliers (SSPM) are high gain photodetectors composed of Geiger photodiodes (GPD) operating above device breakdown voltage. In scintillation based radiation detection applications, SSPMs fabricated using silicon (SiPMs, MPPCs, etc) provide a compact, low cost alternative to photomultiplier tubes (PMTs), however, the high dark count rate due to its low band-gap (1.1eV) limits the signal-to-noise performance as the silicon SSPM is scaled to large areas. SSPMs fabricated in materials with a larger band-gap have the potential to surmount the performance limitations experienced by silicon. AlGaAs is a material that provides a bandgap from 1.55eV to 2.13 eV, depending on Al concentration. Using high Al concentration AlGaAs to engineer a wideband- gap (>2eV) SSPM is very desirable in terms of reducing dark noise, which promises better signal-to-noise performances when large detector areas is needed. This work describes the development of Geiger photodiodes (GPDs), the individual elements of a SSPM, fabricated in AlGaAs with 80% Al concentration. We present the design of the GPDs, the fabrication process, along with characterization data of fabricated GPD samples. To the best of our knowledge, we have demonstrated for the first time, a passively quenched Geiger photodiode in Al0.8Ga0.2As.

  13. Modular design for narrow scintillating cells with MRS photodiodes in strong magnetic field for ILC detector

    Science.gov (United States)

    Beznosko, D.; Blazey, G.; Dyshkant, A.; Rykalin, V.; Schellpffer, J.; Zutshi, V.

    2006-08-01

    The experimental results for the narrow scintillating elements with effective area about 20 cm 2 are reported. The elements were formed from the single piece of scintillator and were read out via wavelength shifting (WLS) fibers with the Metal/Resistor/Semiconductor (MRS) photodiodes on both ends of each fiber. The count rates were obtained using radioactive source 90Sr, with threshold at about three photoelectrons in each channel and quad coincidences (double coincidences between sensors on each fiber and double coincidences between two neighboring fibers). The formation of the cells from the piece of scintillator by using grooves is discussed, and their performances were tested using the radioactive source by measuring the photomutiplier current using the same WLS fiber. Because effective cell area can be readily enlarged or reduced, this module may be used as an active element for calorimeter or muon system for the design of the future electron-positron linear collider detector. Experimental verification of the performance of the MRS photodiode in a strong magnetic field of 9 T, and the impact a magnet quench at 9.5 T are reported. The measurement method used is described. The results confirm the expectations that the MRS photodiode is insensitive to a strong magnetic field and therefore applicable to calorimetry in the presence of magnetic field. The overall result is of high importance for large multi-channel systems.

  14. 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

  15. The net benefit of public expenditures on avalanche defence structures in the municipality of Davos, Switzerland

    Science.gov (United States)

    Fuchs, S.; McAlpin, M. C.

    2005-04-01

    Avalanches pose a threat to settlements as well as industrial and recreational areas in the Alps. As a counter measure, technical mitigation measures have been implemented since the 19th century, resulting in a raise in value of formerly endangered areas. This increase in value can be considered as a benefit due to prevented damage. This paper compares the total costs and benefits of technical mitigation measures in the municipality of Davos, Switzerland as a basis for evaluating their net social benefit. The benefit of avalanche defence structures is determined using two different approaches. First, the replacement value of buildings protected by mitigation measures is quantified. Second, the number of protected persons is monetarily assessed by means of a human capital approach. The quantified benefit is compared with the present value of cumulative capital expenditures on avalanche mitigation measures. In addition, distributional effects of the public expenditures on technical mitigation measures are discussed based on the average future tax revenues within protected areas. Depending on whether benefits are calculated in terms of protected buildings or protected persons, the results show a large range of cost-benefit ratios. Critical issues of cost-benefit analyses in the context of alpine natural hazards are highlighted, including problems related to the human capital approach and the sensitivity of results to how benefits are calculated. The applicability of cost-benefit analyses for evaluating avalanche mitigation measures is discussed.

  16. A concept for a hadron calorimeter with photodiode readout

    International Nuclear Information System (INIS)

    A concept for a hadron calorimeter will be described. The calorimeter is a scintillator sandwich type with WLS-bars and photodiode readout. Emphasis is put on compactness, high stability, easy fabrication, and safety. (orig.)

  17. Design and optimization of evanescently coupled waveguide photodiodes

    Institute of Scientific and Technical Information of China (English)

    Yao Chen; Cheng Yuanbing; Wu Jian; Xu Kun; Qiu Jifang; Zhao Lingjuan; Wang Wei; Lin Jintong

    2011-01-01

    We present the design and optimization of evanescently coupled waveguide photodiodes (EC-WPDs) based on the coupling modes theory and the beam propagation method.Efficient focalization of the optical power in the absorber is achieved by an appropriate choice of index matching layers of EC-WPDs.Numerical simulation shows that high-speed (40 GHz),high quantum efficiency (81%) and high linearity photodiodes can be achieved,and EC-WPDs are promising devices for future optical communication systems.

  18. Infrared vertically-illuminated photodiode for chip alignment feedback

    Science.gov (United States)

    Alloatti, L.; Ram, R. J.

    2016-08-01

    We report on vertically-illuminated photodiodes fabricated in the GlobalFoundries 45nm 12SOI node and on a packaging concept for optically-interconnected chips. The photodiodes are responsive at 1180 nm -a wavelength currently used in chip-to-chip communications. They have further a wide field-of-view which enables chip-to-board positional feedback in chip-board assemblies. Monolithic integration enables on-chip processing of the positional data.

  19. Infrared vertically-illuminated photodiode for chip alignment feedback

    CERN Document Server

    Alloatti, Luca

    2016-01-01

    We report on vertically-illuminated photodiodes fabricated in the GlobalFoundries 45nm 12SOI node and on a packaging concept for optically-interconnected chips. The photodiodes are responsive at 1180 nm, a wavelength currently used in chip-to-chip communications. They have further a wide field-of-view which enables chip-to-board positional feedback in chip-board assemblies. Monolithic integration enables on-chip processing of the positional data.

  20. Photodiode Circuit Macro-model for SPICE Simulation

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    An accurate photodiode circuit macro-model is proposed for SPICE simulation. The definition and implementation of the macro-model is based on carrier stationary continuity equation. In this macro-model, the photodiode is a device of three pins, one for light intensity input and the other two for photocurrent output, which represent the relationship between photocurrent and incident light. The validity of the proposed macro-model is demonstrated with its PSPICE simulation result compared with reported experimental data.

  1. 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

  2. Low-temperature-dependent property in an avalanche photodiode based on GaN/AlN periodically-stacked structure

    Science.gov (United States)

    Zheng, Jiyuan; Wang, Lai; Yang, Di; Yu, Jiadong; Meng, Xiao; Hao, Zhibiao; Sun, Changzheng; Xiong, Bing; Luo, Yi; Han, Yanjun; Wang, Jian; Li, Hongtao; Li, Mo; Li, Qian

    2016-01-01

    In ultra-high sensitive APDs, a vibrate of temperature might bring a fatal decline of the multiplication performance. Conventional method to realize a temperature-stable APD focuses on the optimization of device structure, which has limited effects. While in this paper, a solution by reducing the carrier scattering rate based on an GaN/AlN periodically-stacked structure (PSS) APD is brought out to improve temperature stability essentially. Transport property is systematically investigated. Compared with conventional GaN homojunction (HJ) APDs, electron suffers much less phonon scatterings before it achieves ionization threshold energy and more electrons occupy high energy states in PSS APD. The temperature dependence of ionization coefficient and energy distribution is greatly reduced. As a result, temperature stability on gain is significantly improved when the ionization happens with high efficiency. The change of gain for GaN (10 nm)/AlN (10 nm) PSS APD from 300 K to 310 K is about 20% lower than that for HJ APD. Additionally, thicker period length is found favorable to ionization coefficient ratio but a bit harmful to temperature stability, while increasing the proportion of AlN at each period in a specific range is found favorable to both ionization coefficient ratio and temperature stability. PMID:27775088

  3. Single electron multiplication distribution in GEM avalanches

    CERN Document Server

    Laszlo, Andras; Kiss, Gabor; Varga, Dezso

    2016-01-01

    In this paper measurement results and experimental methodology is presented on the determination of multiplication distributions of avalanches in GEM foils initiated by a single electron. The measurement relies on the amplification of photoelectrons by the GEM under study, which is subsequently amplified in an MWPC. The intrinsic detector resolution, namely the sigma over mean ratio of this distribution is also elaborated. Small gain dependence of the avalanche size is observed in the range of net effective gain of 15 to 100. The distribution has an exponentially decaying tail at large amplitudes, whereas the applied working gas is seen to have a well visible effect on the shape of the multiplication distribution at low amplitudes; or equivalently, the working gas has an influence on the intrinsic detector resolution of GEMs via suppression of the low amplitude responses. A sigma over mean ratio down to 0.75 was reached using neon based mixture, whereas other gases provided an intrinsic detector resolution cl...

  4. Avalanche dynamics of radio pulsar glitches

    CERN Document Server

    Melatos, A; Wyithe, J S B

    2007-01-01

    We test statistically the hypothesis that radio pulsar glitches result from an avalanche process, in which angular momentum is transferred erratically from the flywheel-like superfluid in the star to the slowly decelerating, solid crust via spatially connected chains of local, impulsive, threshold-activated events, so that the system fluctuates around a self-organised critical state. Analysis of the glitch population (currently 285 events from 101 pulsars) demonstrates that the size distribution in individual pulsars is consistent with being scale invariant, as expected for an avalanche process. The waiting-time distribution is consistent with being exponential in seven out of nine pulsars where it can be measured reliably, after adjusting for observational limits on the minimum waiting time, as for a constant-rate Poisson process. PSR J0537$-$6910 and PSR J0835$-$4510 are the exceptions; their waiting-time distributions show evidence of quasiperiodicity. In each object, stationarity requires that the rate $\\...

  5. Do Neural Avalanches Indicate Criticality After All?

    CERN Document Server

    Dehghani, Mohammad; Shahbazi, Farhad

    2016-01-01

    Neural avalanches in size and duration exhibit a power law distribution illustrating as a straight line when plotted on the logarithmic scales. The power-law exponent is interpreted as the signature of criticality and it is assumed that the resting brain operates near criticality. However, there is no clear evidence that supports this assumption, and even there are extensive research studies conflicting one another. The model of the current paper is an extension of a previous publication wherein we used an integrate-and-fire model on a regular lattice with periodic boundary conditions and introduced the temporal complexity as a genuine signature of criticality. However, in that model the power-law distribution of neural avalanches were manifestation of super-criticality rather than criticality. Here, however, we show that replacing the discrete noise in the model with a Gaussian noise and continuous time solution of the equation leads to coincidence of temporal complexity and spatiotemporal patterns of neural...

  6. Snow Avalanche Release, Scale Invariance and Criticallity

    Science.gov (United States)

    Dendievel, R.; Faillettaz, J.; Daudon, D.; Louchet, F.

    It is widely recognised that a number of geophysical phenomena as volcanic eruptions, landslides, etc, obey the so-called Gutenberg-Richter relation, first established for the frequency-magnitude statistics of earthquakes, where is the occurence frequency of earthquakes with a magnitude greater than m. This power law behaviour, character- istic of critical phenomena, is usually evidenced in the form of a linear distribution in a double logarithmic plot, in a way similar to the self organised criticality of a sand pile (2). We have shown very recently and for the first time that snow avalanche release exhibited such a behaviour (3). The only reliable parameter we had at that time was the amplitude of the acoustic emission associated with the avalanche release. Since it was not possible to record several events in the same gully, data were taken in sev- eral gullys of the same mountain range. Yet, the data aligned quite well on a unique straight line, with a critical exponent of about 1.6. This observation suggests that the very nature of the release mechanism is independent of the average slope and mor- phology of the gully. In order to understand the origin of this critical behaviour and to further investigate the mechanisms responsible for avalanche release, the avalanche release is studied in the present paper both by discrete elements simulations and cel- lular automata, and compared to further field data. The discrete elements simulations deal with a population of spheres on a slope, experiencing both a gravitational stress, interactions with the substrate, and mutual contact interactions. A gradual increase of the slope or a gradual change in contact forces (accounting for thermal snow mi- crostructure evolution) eventually result in avalanche release. The conditions are ad- justed until the frequency-magnitude of avalanches exhibit a critical behaviour. The cellular automaton is more or less similar to a game of life: a 2-d grid of boxes repre- sents the

  7. Avalanche-to-streamer transition near hydrometeors in thunderstorms

    Science.gov (United States)

    Rutjes, Casper; Dubinova, Anna; Ebert, Ute; Buitink, Stijn; Scholten, Olaf; Trinh, Gia

    2016-04-01

    In the early phase of lightning initiation, streamers must form near water droplets and or ice crystals, collectively called hydrometeors, as it is generally believed that the electric fields in a thunderstorm are below classical breakdown [1]. The hydrometeors, due to their dielectric property, electrically polarize and will enhance the thunderstorm electric field in localized areas just outside the surface, potentially above breakdown. Available electrons, from for example a cosmic ray event, are drawn towards the positive side of the polarized hydrometeor. Some electrons reach the localized area above breakdown, while oxygen molecules have absorbed others. In the area above breakdown electrons begin to multiply in number, creating electron avalanches towards the surface, leaving positive ions behind. This results in a charge separation, which potentially can initiate a positive streamer. The final outcome however strongly depends on several parameters, such as the strength of the thunderstorm electric field, the size and shape of the hydrometeor and the initial amount of electrons. In our letter [1] we introduced a dimensionless quantity M that we call the Meek number, based on the historical and well-used Reather-Meek criterion [2], as a measure of how likely it is to create an avalanche-to-streamer transition near a hydrometeor. Results from simulations showed that streamers can start in a field of only 15% of breakdown from large elongated shaped hydrometeors. Now we extended and generalized our method to arbitrary shaped hydrometeors and we take into account that potentially several electrons can reach the area above breakdown. Due to these effects we can predict smaller hydrometeors to be able to start streamers. We will present the latest results. [1] Dubinova, A., Rutjes, C., Ebert, U., Buitink, S., Scholten, O., & Trinh, G. T. N. (2015). Prediction of lightning inception by large ice particles and extensive air showers. Physical review letters, 115

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

    Science.gov (United States)

    Ohno, M.; Kawano, T.; Edahiro, I.; Shirakawa, H.; Ohashi, N.; Okada, C.; Habata, S.; Katsuta, J.; Tanaka, Y.; Takahashi, H.; Mizuno, T.; Fukazawa, Y.; Murakami, H.; Kobayashi, S.; Miyake, K.; Ono, K.; Kato, Y.; Furuta, Y.; Murota, Y.; Okuda, K.; Wada, Y.; Nakazawa, K.; Mimura, T.; Kataoka, J.; Ichinohe, Y.; Uchida, Y.; Katsuragawa, M.; Yoneda, H.; Sato, G.; Sato, R.; Kawaharada, M.; Harayama, A.; Odaka, H.; Hayashi, K.; Ohta, M.; Watanabe, S.; Kokubun, M.; Takahashi, T.; Takeda, S.; Kinoshita, M.; Yamaoka, K.; Tajima, H.; Yatsu, Y.; Uchiyama, H.; Saito, S.; Yuasa, T.; Makishima, K.

    2016-09-01

    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.

  9. Basic characteristics of the avalanche transistor

    International Nuclear Information System (INIS)

    The avalanche transistor is a useful device for a short-pulse generator of the thermionic electron-gun. However, some properties of the transistor have not been clear experimentally until now. In this report the following properties are presented: the thermal characteristics of the primary breakdown voltage, variations of the output pulse waveform according to the power supply voltage, and the estimated V-I curve of the secondary breakdown voltage. (author)

  10. Unjamming and jamming transitions of granular avalanches

    Science.gov (United States)

    Zhang, Jie; Wang, Ziwei

    2014-03-01

    Study of the jamming transitions of granular materials has become an active field of research in recent years. A closely related inverse process is the unjamming transition, where granular systems may suddenly lose rigidity and start to flow freely. Understanding such a process is of crucial implication towards the understanding of natural disasters such as snow avalanches, landslides and earthquakes. Recent work by Banigan and colleagues (Nature Physics 2013) has provided a new perspective in the study of unjamming and jamming transitions by applying nonlinear dynamical methods. To test their proposition experimentally, we have designed a rotating drum filled with bidisperse photo-elastic disks to create particle avalanches. In unjamming transition, Lyapunov vector and velocity fields are indeed strongly correlated in spatial domain, whereas in jamming transition no such a strong correlation is observed. The Lyapunov exponents are positive in unjamming transition and negative in jamming transition. In addition, the total stress variation, kinetic energy, and non-affine motion of particles all show strong correlations in the time domain during avalanches. Their spatial correlations have also been analyzed.

  11. Mathematical modeling of powder-snow avalanche flows

    OpenAIRE

    Dutykh, Denys; Acary-Robert, Céline; Bresch, Didier

    2009-01-01

    Powder-snow avalanches are violent natural disasters which represent a major risk for infrastructures and populations in mountain regions. In this study we present a novel model for the simulation of avalanches in the aerosol regime. The second scope of this study is to get more insight into the interaction process between an avalanche and a rigid obstacle. An incompressible model of two miscible fluids can be successfully employed in this type of problems. We allow for mass diffusion between...

  12. Analysis and simulatin of rock avalanche sequence in the Cerro Caquilluco landslide (Tacna, Peru)

    Science.gov (United States)

    Crosta, Giovanni B.; Frattini, Paolo; Valbuzzi, Elena; Hermanns, Reginald L.

    2014-05-01

    The Cerro Caquilluco (Tacna, Peru) rock avalanche complex has a total volume of about 15 km3 and a length of 43 km, extending from 3900 m a.s.l to 530 m a.s.l.. Based on geomorphological interpretation and lithological evidences, we reconstructed a possible rock-avalanches sequence consisting of at least nine major events. For each event, we calculated the mobilized volumes through the comparison of pre- and post-failure morphology. We argue that the first rock avalanche event corresponds to the Cerrillos Negros rock avalanche, characterized by a distal tongue shaped lobe, 11 km long, 3 km wide and 25 to 60 m thick (rough volume estimate 1.15 km3), deposited along the piedmont surface (average slope: 2° ). The reconstruction of pristine pre-failure morphology was accomplished by mimicking the preserved morphology close to the source area, and by removing the deposited volumes from the rock avalanche path. For this, we made the hypothesis that the old paleosurface was already eroded by valleys progressively moving upstream during a wetter climate, as suggested by Hoke et al (2007) for similar conditions in northern Chile. The reconstruction of the pre-event morphology required several attempts to fit the eroded and the deposited volumes. Finally, a total mobilized volume of about 10.2 km2 was obtained for this event. For the successive scenarios of slide retrogression, we used the morphologies obtained by previous scenarios as pre-failure morphologies, and we calculated, by difference with current topography, the lobe volumes. The volumes of single rock avalanche episodes decrease from the first to the last event, roughly following a power-law decay. This behavior is comparable to that described by Utili and Crosta (2011) for retrogressive instabilities in rocky cliffs. The rock-avalanche events have been simulated, to verify the different scenarios in terms of spreading area and maximum runout, by using SPH (Smooth Particle Hydrodynamics) and Finite Element codes

  13. Development of a gamma dosimeter using a photodiode

    International Nuclear Information System (INIS)

    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

  14. Hybrid UV Imager Containing Face-Up AlGaN/GaN Photodiodes

    Science.gov (United States)

    Zheng, Xinyu; Pain, Bedabrata

    2005-01-01

    A proposed hybrid ultraviolet (UV) image sensor would comprise a planar membrane array of face-up AlGaN/GaN photodiodes integrated with a complementary metal oxide/semiconductor (CMOS) readout-circuit chip. Each pixel in the hybrid image sensor would contain a UV photodiode on the AlGaN/GaN membrane, metal oxide/semiconductor field-effect transistor (MOSFET) readout circuitry on the CMOS chip underneath the photodiode, and a metal via connection between the photodiode and the readout circuitry (see figure). The proposed sensor design would offer all the advantages of comparable prior CMOS active-pixel sensors and AlGaN UV detectors while overcoming some of the limitations of prior (AlGaN/sapphire)/CMOS hybrid image sensors that have been designed and fabricated according to the methodology of flip-chip integration. AlGaN is a nearly ideal UV-detector material because its bandgap is wide and adjustable and it offers the potential to attain extremely low dark current. Integration of AlGaN with CMOS is necessary because at present there are no practical means of realizing readout circuitry in the AlGaN/GaN material system, whereas the means of realizing readout circuitry in CMOS are well established. In one variant of the flip-chip approach to integration, an AlGaN chip on a sapphire substrate is inverted (flipped) and then bump-bonded to a CMOS readout circuit chip; this variant results in poor quantum efficiency. In another variant of the flip-chip approach, an AlGaN chip on a crystalline AlN substrate would be bonded to a CMOS readout circuit chip; this variant is expected to result in narrow spectral response, which would be undesirable in many applications. Two other major disadvantages of flip-chip integration are large pixel size (a consequence of the need to devote sufficient area to each bump bond) and severe restriction on the photodetector structure. The membrane array of AlGaN/GaN photodiodes and the CMOS readout circuit for the proposed image sensor would

  15. High-density avalanche chambers for positron emission tomography

    Energy Technology Data Exchange (ETDEWEB)

    Manfrass, P.; Enghardt, W.; Fromm, W.D.; Wohlfarth, D.; Hohmuth, K.

    1988-12-15

    A positron tomograph for radiopharmaceutical and medical research is under construction. In its final stage it will cover six high-density avalanche chambers (HIDAC) in a hexagonal arrangement. Each detector with a sensitive area of 50x28 cm/sup 2/ will consist of a stack of four pairs of multihole photon-to-electron converters with a multiwire proportional counter (MWPC) in between. An experimental investigation of detector properties as time and spatial resolutions as well as detector efficiency in dependence to converter structure, electric field strength and counting gas mixture preceded the final design of these detectors. Results of these studies are outlined. Furthermore, longitudinal tomograms taken with a stationary test camera are presented.

  16. PbS colloidal quantum dot photodiodes for SWIR detection

    OpenAIRE

    Heves, Emre; Gürbüz, Yaşar; Gurbuz, Yasar

    2012-01-01

    In this work, PbS colloidal quantum dot based photodiodes are realized compatible for the integration on ROIC's. Schottky photodiode architecture is selected for its fast response and moderate sensitivity. The device is formed from Indium tin oxide (ITO) anode, the photosensitive PbS layer and a schottky contact formed of titanium and gold. Pinhole-free uniform PbS quantum dots film achieved by optimized layer by layer spin coating process. Solid-state ligand change procedure applied during f...

  17. Low-energy X-ray and gamma spectrometry using silicon photodiodes; Espectrometria de raios X e gama de baixa energia utilizando fotodiodos de silicio

    Energy Technology Data Exchange (ETDEWEB)

    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{sup 2} and 0,25 cm{sup 2}, thickness of the depletion ranging from 100 to 200 {mu}m 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 {sup 241} Am, {sup 109} Cd, {sup 57} Co and {sup 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)

  18. Lifetime of bubble rafts: cooperativity and avalanches.

    Science.gov (United States)

    Ritacco, Hernán; Kiefer, Flavien; Langevin, Dominique

    2007-06-15

    We have studied the collapse of pseudo-bi-dimensional foams. These foams are made of uniformly sized soap bubbles packed in an hexagonal lattice sitting at the top of a liquid surface. The collapse process follows the sequence: (1) rupture of a first bubble, driven by thermal fluctuations and (2) a cascade of bursting bubbles. We present a simple numerical model which captures the main characteristics of the dynamics of foam collapse. We show that in a certain range of viscosities of the foaming solutions, the size distribution of the avalanches follows power laws as in self-organized criticality processes. PMID:17677967

  19. TCAD simulation of Low Gain Avalanche Detectors

    Science.gov (United States)

    Dalal, Ranjeet; Jain, Geetika; Bhardwaj, Ashutosh; Ranjan, Kirti

    2016-11-01

    In the present work, detailed simulation using Technology Computer Aided Design (TCAD) tool, Silvaco for non-irradiated and irradiated LGAD (Low Gain Avalanche Detector) devices has been carried out. The effects of different design parameters and proton irradiation on LGAD operation are discussed in detail. An already published effective two trap bulk damage model is used to simulate the radiation damage without implementing any acceptor removal term. The TCAD simulation for irradiated LGAD devices produce decreasing gain with increasing fluence, similar to the measurement results. The space charge density and electric field distribution are used to illustrate the possible reasons for the degradation of gain of the irradiated LGAD devices.

  20. Bilayer avalanche spin-diode logic

    International Nuclear Information System (INIS)

    A novel spintronic computing paradigm is proposed and analyzed in which InSb p-n bilayer avalanche spin-diodes are cascaded to efficiently perform complex logic operations. This spin-diode logic family uses control wires to generate magnetic fields that modulate the resistance of the spin-diodes, and currents through these devices control the resistance of cascaded devices. Electromagnetic simulations are performed to demonstrate the cascading mechanism, and guidelines are provided for the development of this innovative computing technology. This cascading scheme permits compact logic circuits with switching speeds determined by electromagnetic wave propagation rather than electron motion, enabling high-performance spintronic computing

  1. High voltage short plus generation based on avalanche circuit

    International Nuclear Information System (INIS)

    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)

  2. Avalanche size scaling in sheared three-dimensional amorphous solid

    DEFF Research Database (Denmark)

    Bailey, Nicholas; Schiøtz, Jakob; Lemaître, A.;

    2007-01-01

    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 by...... the mean fractal dimension and participation ratio....

  3. Structural Measures for Controlling Avalanches in Formation Zone

    Directory of Open Access Journals (Sweden)

    Vinay Chaudhary

    2006-11-01

    Full Text Available Jammu-Srinagar national highway (NH-1A, a lifeline of the Kashmir valley, gains considerableimportance as being the only link between the Kashmir valley and the rest of the country. Astretch of 15 km is marred by 15 major avalanche sites, out of that D-10 avalanche site takes aheavy toll of life and property, besides bringing the busiest highway to a standstill for daystogether, year after year. Therefore, this avalanche site was selected for installation of avalanchecontrolstructures in formation zone and demonstration of technology thereof. A combinationof wind-control structures, supporting structures, and controlled release of avalanches usingexplosive, has been adopted to mitigate avalanche hazard. As a result, the D-10 site can boastof having become a school for live demonstration of the avalanche-control methods on themighty Pir Panjal range at more than 3200 m above the sea level. This paper deals with themethods used for control of avalanches in formation zone of D-10 avalanche site and brings outtheir effectiveness and site-specific applications.

  4. An evaluation of the new compact hybrid photodiodes R7110U-07/40 from Hamamatsu in high-speed light detection mode

    International Nuclear Information System (INIS)

    The main parameters of hybrid photodiodes (HPD) are constantly improving. In the new 20 mm diameter HPDs from Hamamatsu an avalanche diode (AD) serves as anode. Due to high gain of the used ADs the HPDs show a total gain of 6-8x104 at nominal HV. This allows one to use HPDs with very fast low-noise voltage amplifiers and to detect fast pulses (down to the single photoelectron level) with very good amplitude resolution. Of special interest are HPDs of the type R7110U-40 with GaAsP photocathode which provide a quantum efficiency of ∼40% in maximum at ∼500 nm. Results on the evaluation of the above-mentioned HPDs and their comparison with HPDs from INTEVAC will be presented

  5. Avalanche behavior of power MOSFETs under different temperature conditions

    Institute of Scientific and Technical Information of China (English)

    Lu Jiang; Wang Lixin; Lu Shuojin; Wang Xuesheng; Han Zhengsheng

    2011-01-01

    The ability of high-voltage power MOSFETs to withstand avalanche events under different temperature conditions are studied by experiment and two-dimensional device simulation. The experiment is performed to investigate dynamic avalanche failure behavior of the domestic power MOSFETs which can occur at the rated maximum operation temperature range (-55 to 150 ℃). An advanced ISE TCAD two-dimensional mixed mode simulator with thermodynamic non-isothermal model is used to analyze the avalanche failure mechanism. The unclamped inductive switching measurement and simulation results show that the parasitic components and thermal effect inside the device will lead to the deterioration of the avalanche reliability of power MOSFETs with increasing temperature. The main failure mechanism is related to the parasitic bipolar transistor activity during the occurrence of the avalanche behavior.

  6. 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

  7. Townsend coefficients of gases in avalanche counters

    International Nuclear Information System (INIS)

    Though much work has been done by many authors in the last few years in the development and application of avalanche counters for ion radiation, it is based upon values of the Townsend coefficients as the essential gas parameter, which were determined many years ago for much lower reduced field strengths F/p than prevail in such counters. Therefore absolute determinations of α in vapours of methyl alcohol, cyclohexane, acetone, and n-heptene were performed under original conditions of avalanche counters. The values obtained do not differ by more than 30%-50% from the former values indeed, extrapolated over F/p for the first three mentioned substances, but the amounts of A and B in the usual representation α/p=A exp(-B(F/p)) are much greater for the stronger reduced fields. This is of importance for such counter properties as the dependence of pulse heights on pressure, voltage, electrode distance etc., which are governed by other combinations of A and B than α/p itself. A comparison of results for different ionic radiations shows a marked influence of the primary ionization density along the particle tracks which is hard to explain. (Auth.)

  8. Similar Hamiltonian Between Avalanche-effect & Sociophysics

    Science.gov (United States)

    Maksoed, Ssi, Wh-

    2016-05-01

    Of similar Hamiltonian concerned in ``sociophysics'', there were RandomFieldIsingModel/RFIM in external field retrieved in S. Sabhapandit:``Hysteresis & Avalanche in RandomFieldIsingModel'',2002:'' ..in earthquake, it is an energy release and in case of ferromagnet, it is the size of the domain flips''. Following the extremes & compromises curve in Serge Galam: ``Sociophysics: a Review of Galam Model'', 2008 fig. 12, h 9 whereas it seems similar with ``heating curve''-Prof. Ir. Abdul Kadir: ``Mesin Arus Searah'', h 192 when the heat sources are continuous denote continuous opinion dynamics. Further, hysteresis as duties in ``Kajian Analisis Model Mikromagnetik dari Struktur Magnet Nanokomposit'', 2007 [ UI file no. S29286 ] also sought:'' calculate the probability that `one more site became unstable' causes an avalanche of the spin flips...'' usually found in Per Bak sand-pile fractal characters experiment exhibits. Great acknowledgment to HE. Mr. LieutGen-TNI[rtd]. H. TUK SETYOHADI, +62-21-7220385, Jl. Sriwijaya Raya 3, Kebayoran Baru, South-Jakarta.

  9. Modelisation de photodetecteurs a base de matrices de diodes avalanche monophotoniques pour tomographie d'emission par positrons

    Science.gov (United States)

    Corbeil Therrien, Audrey

    La tomographie d'emission par positrons (TEP) est un outil precieux en recherche preclinique et pour le diagnostic medical. Cette technique permet d'obtenir une image quantitative de fonctions metaboliques specifiques par la detection de photons d'annihilation. La detection des ces photons se fait a l'aide de deux composantes. D'abord, un scintillateur convertit l'energie du photon 511 keV en photons du spectre visible. Ensuite, un photodetecteur convertit l'energie lumineuse en signal electrique. Recemment, les photodiodes avalanche monophotoniques (PAMP) disposees en matrice suscitent beaucoup d'interet pour la TEP. Ces matrices forment des detecteurs sensibles, robustes, compacts et avec une resolution en temps hors pair. Ces qualites en font un photodetecteur prometteur pour la TEP, mais il faut optimiser les parametres de la matrice et de l'electronique de lecture afin d'atteindre les performances optimales pour la TEP. L'optimisation de la matrice devient rapidement une operation difficile, car les differents parametres interagissent de maniere complexe avec les processus d'avalanche et de generation de bruit. Enfin, l'electronique de lecture pour les matrices de PAMP demeure encore rudimentaire et il serait profitable d'analyser differentes strategies de lecture. Pour repondre a cette question, la solution la plus economique est d'utiliser un simulateur pour converger vers la configuration donnant les meilleures performances. Les travaux de ce memoire presentent le developpement d'un tel simulateur. Celui-ci modelise le comportement d'une matrice de PAMP en se basant sur les equations de physique des semiconducteurs et des modeles probabilistes. Il inclut les trois principales sources de bruit, soit le bruit thermique, les declenchements intempestifs correles et la diaphonie optique. Le simulateur permet aussi de tester et de comparer de nouvelles approches pour l'electronique de lecture plus adaptees a ce type de detecteur. Au final, le simulateur vise a

  10. BiCMOS-integrated photodiode exploiting drift enhancement

    Science.gov (United States)

    Swoboda, Robert; Schneider-Hornstein, Kerstin; Wille, Holger; Langguth, Gernot; Zimmermann, Horst

    2014-08-01

    A vertical pin photodiode with a thick intrinsic layer is integrated in a 0.5-μm BiCMOS process. The reverse bias of the photodiode can be increased far above the circuit supply voltage, enabling a high-drift velocity. Therefore, a highly efficient and very fast photodiode is achieved. Rise/fall times down to 94 ps/141 ps at a bias of 17 V were measured for a wavelength of 660 nm. The bandwidth was increased from 1.1 GHz at 3 V to 2.9 GHz at 17 V due to the drift enhancement. A quantum efficiency of 85% with a 660-nm light was verified. The technological measures to avoid negative effects on an NPN transistor due to the Kirk effect caused by the low-doped I-layer epitaxy are described. With a high-energy collector implant, the NPN transit frequency is held above 20 GHz. CMOS devices are unaffected. This photodiode is suitable for a wide variety of high-sensitivity optical sensor applications, for optical communications, for fiber-in-the-home applications, and for optical interconnects.

  11. Fundamental Characteristics of a Pinned Photodiode CMOS Pixels

    NARCIS (Netherlands)

    Xu, Y.

    2015-01-01

    This thesis gives an insightful analysis of the pinned photodiode 4T CMOS pixel from three different aspects. Firstly, from the charge accumulated aspect, the PPD full well capacity and related parameters of influence are investigated such as the pinning voltage, and transfer gate potential barrier.

  12. Snow avalanche history in Parâng Mountains (Southern Carpathians revealed by dendrogeomorphic analyses

    Directory of Open Access Journals (Sweden)

    Flaviu MESEȘAN

    2014-11-01

    Full Text Available Parâng Mountains belong to Southern Carpathians, having the maximum altitude in Parângul Mare Peak (2519 m a.s.l.. The geology is dominated by crystalline schists, due to whom the relief is characterized by steep slopes. Between 1400 – 1700 m the average annual temperature is around 2-3ᴼC and the total precipitation about 1000-1200 mm/year. Coniferous belt extends roughly at the mentioned altitudes, being dominated by Norway spruce (Picea abies forests. Above 1800 m the average annual temperature drops below 2ᴼC and the average rainfalls reach 1200 mm/year, allowing the development of alpine shrubs and alpine grassland (Oancea et al., 1987. Crests and steep slopes in these subalpine areas are prone to snow accumulation and avalanche release. Despite the favorable conditions for avalanche trigger in this area, only one avalanche event is historically recorded, with severe impact on forest areas, but no destructive impact on infrastructure or fatalities.

  13. Linear array of photodiodes to track a human speaker for video recording

    Science.gov (United States)

    DeTone, D.; Neal, H.; Lougheed, R.

    2012-12-01

    Communication and collaboration using stored digital media has garnered more interest by many areas of business, government and education in recent years. This is due primarily to improvements in the quality of cameras and speed of computers. An advantage of digital media is that it can serve as an effective alternative when physical interaction is not possible. Video recordings that allow for viewers to discern a presenter's facial features, lips and hand motions are more effective than videos that do not. To attain this, one must maintain a video capture in which the speaker occupies a significant portion of the captured pixels. However, camera operators are costly, and often do an imperfect job of tracking presenters in unrehearsed situations. This creates motivation for a robust, automated system that directs a video camera to follow a presenter as he or she walks anywhere in the front of a lecture hall or large conference room. Such a system is presented. The system consists of a commercial, off-the-shelf pan/tilt/zoom (PTZ) color video camera, a necklace of infrared LEDs and a linear photodiode array detector. Electronic output from the photodiode array is processed to generate the location of the LED necklace, which is worn by a human speaker. The computer controls the video camera movements to record video of the speaker. The speaker's vertical position and depth are assumed to remain relatively constant- the video camera is sent only panning (horizontal) movement commands. The LED necklace is flashed at 70Hz at a 50% duty cycle to provide noise-filtering capability. The benefit to using a photodiode array versus a standard video camera is its higher frame rate (4kHz vs. 60Hz). The higher frame rate allows for the filtering of infrared noise such as sunlight and indoor lighting-a capability absent from other tracking technologies. The system has been tested in a large lecture hall and is shown to be effective.

  14. Disordered artificial spin ices: Avalanches and criticality (invited)

    Energy Technology Data Exchange (ETDEWEB)

    Reichhardt, Cynthia J. Olson, E-mail: cjrx@lanl.gov; Chern, Gia-Wei; Reichhardt, Charles [Center for Nonlinear Studies and Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Libál, Andras [Faculty of Mathematics and Computer Science, Babes-Bolyai University, RO-400591 Cluj-Napoca (Romania)

    2015-05-07

    We show that square and kagome artificial spin ices with disconnected islands exhibit disorder-induced nonequilibrium phase transitions. The critical point of the transition is characterized by a diverging length scale and the effective spin reconfiguration avalanche sizes are power-law distributed. For weak disorder, the magnetization reversal is dominated by system-spanning avalanche events characteristic of a supercritical regime, while at strong disorder, the avalanche distributions have subcritical behavior and are cut off above a length scale that decreases with increasing disorder. The different type of geometrical frustration in the two lattices produces distinct forms of critical avalanche behavior. Avalanches in the square ice consist of the propagation of locally stable domain walls separating the two polarized ground states, and we find a scaling collapse consistent with an interface depinning mechanism. In the fully frustrated kagome ice, however, the avalanches branch strongly in a manner reminiscent of directed percolation. We also observe an interesting crossover in the power-law scaling of the kagome ice avalanches at low disorder. Our results show that artificial spin ices are ideal systems in which to study a variety of nonequilibrium critical point phenomena as the microscopic degrees of freedom can be accessed directly in experiments.

  15. Investigation and modeling of the avalanche effect in MOSFETs with non-uniform finger spacing

    Institute of Scientific and Technical Information of China (English)

    Liu Jun; Sun Lingling; Marissa Condon

    2011-01-01

    This paper investigates the effect of a non-uniform gate-finger spacing layout structure on the avalanche breakdown performance of RF CMOS technology.Compared with a standard multi-finger device with uniform gate-finger spacing,a device with non-uniform gate-finger spacing represents an improvement of 8.5% for the drain-source breakdown voltage(BVds)and of 20% for the thermally-related drain conductance.A novel compact model is proposed to accurately predict the variation of BVds with the total area of devices,which is dependent on the different finger spacing sizes.The model is verified and validated by the excellent match between the measured and simulated avalanche breakdown characteristics for a set of uniform and non-uniform gate-finger spacing arranged nMOSFETs.

  16. Statistical analyses support power law distributions found in neuronal avalanches.

    Directory of Open Access Journals (Sweden)

    Andreas Klaus

    Full Text Available The size distribution of neuronal avalanches in cortical networks has been reported to follow a power law distribution with exponent close to -1.5, which is a reflection of long-range spatial correlations in spontaneous neuronal activity. However, identifying power law scaling in empirical data can be difficult and sometimes controversial. In the present study, we tested the power law hypothesis for neuronal avalanches by using more stringent statistical analyses. In particular, we performed the following steps: (i analysis of finite-size scaling to identify scale-free dynamics in neuronal avalanches, (ii model parameter estimation to determine the specific exponent of the power law, and (iii comparison of the power law to alternative model distributions. Consistent with critical state dynamics, avalanche size distributions exhibited robust scaling behavior in which the maximum avalanche size was limited only by the spatial extent of sampling ("finite size" effect. This scale-free dynamics suggests the power law as a model for the distribution of avalanche sizes. Using both the Kolmogorov-Smirnov statistic and a maximum likelihood approach, we found the slope to be close to -1.5, which is in line with previous reports. Finally, the power law model for neuronal avalanches was compared to the exponential and to various heavy-tail distributions based on the Kolmogorov-Smirnov distance and by using a log-likelihood ratio test. Both the power law distribution without and with exponential cut-off provided significantly better fits to the cluster size distributions in neuronal avalanches than the exponential, the lognormal and the gamma distribution. In summary, our findings strongly support the power law scaling in neuronal avalanches, providing further evidence for critical state dynamics in superficial layers of cortex.

  17. Geological history and within-island diversity: a debris avalanche and the Tenerife lizard Gallotia galloti.

    Science.gov (United States)

    Brown, Richard P; Hoskisson, Paul A; Welton, John-Henry; Báez, Marcos

    2006-10-01

    Several processes have been described that could explain geographical variation and speciation within small islands, including fragmentation of populations through volcanic eruptions. Massive landslides, or debris avalanches, could cause similar effects. Here we analyse the potential impact of the 0.8 million-year-ago (Ma) Güimar valley debris avalanche on the phylogeography of the lizard Gallotia galloti on the Canary Island of Tenerife. Distributions of mitochondrial DNA lineages (based on cytochrome b sequences) were analysed on a 60-km southeastern coast transect centred on this area. Three main clades were detected, which can be divided into northern (one clade) and southern (two clades) groups that introgress across the valley. Maximum-likelihood estimates of migration rates (scaled for mutation rate) revealed highly asymmetric patterns, indicating that long-term gene flow into this region from both the northern and the southern populations greatly exceeded that in the opposite directions, consistent with recolonization of the area. The ancestral Tenerife node on the G. galloti tree is estimated at 0.80 Ma, matching closely with the geological estimate for the debris avalanche. Morphological variation (body dimensions and scalation) was also analysed and indicated a stepped cline in female scalation across the valley, although the patterns for male scalation and male and female body dimensions were not as clear. Together these findings provide support for the hypothesis that the debris avalanche has shaped the phylogeography of G. galloti and may even have been a primary cause of the within-island cladogenesis through population fragmentation and isolation. Current estimates of timing of island unification mean that the original hypothesis that within-island diversity is explained by the secondary contact of populations from the two ancient precursor islands of Teno and Anaga is less plausible for this and some other Tenerife species. Large-scale landslides

  18. Snow Mass Quantification and Avalanche Victim Search By Ground Penetrating Radar

    Science.gov (United States)

    Jaedicke, C.

    Ground penetrating radar (GPR) systems can be used in many applications of snow and ice research. The information from the GPR is interpreted to identify layers, ob- ject and different structures in the snow. A commercially available GPR system was further developed to work in the rough environment of snow and ice. The applied GPR is a 900 MHz system that easily reaches snow depths of ten meters. The system is cal- ibrated by several manual snow depth measurements during each survey. The depth resolution is depending on the snow type and ranges around +/- 0.1 m. The GPR sys- tem carried along a line of interest and is triggered by an odometer wheel at regular adjustable steps. All equipment is mounted in a sledge and is moved by a snow mo- bile over the surface. This setup allows the efficient coverage of several kilometers of profiles. The radar profiles give a real time two-dimensional impression of structures and objects and the interface between snow and underlying ground. The actual radar profile is shown on a screen on the sledge allowing the immediate marking of objects and structures. During the past three years the instrument was successfully used for the study of snow distributions, for the detection of glacier crevasses under the snow cover and for the search of avalanche victims in avalanche debris. The results show the capability of the instrument to detect persons and objects in the snow cover. In the future this could be new tool for avalanche rescue operations. Today the size and weight of the system prevents the access to very steep slopes and areas not accessible for snowmobile. Further development will decrease the size of the system and make it a valuable tool to quantify the snow mass in avalanche release zones and run out areas.

  19. Modelling rock-avalanche induced impact waves: Sensitivity of the model chains to model parameters

    Science.gov (United States)

    Schaub, Yvonne; Huggel, Christian

    2014-05-01

    New lakes are forming in high-mountain areas all over the world due to glacier recession. Often they will be located below steep, destabilized flanks and are therefore exposed to impacts from rock-/ice-avalanches. Several events worldwide are known, where an outburst flood has been triggered by such an impact. In regions such as in the European Alps or in the Cordillera Blanca in Peru, where valley bottoms are densely populated, these far-travelling, high-magnitude events can result in major disasters. Usually natural hazards are assessed as single hazardous processes, for the above mentioned reasons, however, development of assessment and reproduction methods of the hazardous process chain for the purpose of hazard map generation have to be brought forward. A combination of physical process models have already been suggested and illustrated by means of lake outburst in the Cordillera Blanca, Peru, where on April 11th 2010 an ice-avalanche of approx. 300'000m3 triggered an impact wave, which overtopped the 22m freeboard of the rock-dam for 5 meters and caused and outburst flood which travelled 23 km to the city of Carhuaz. We here present a study, where we assessed the sensitivity of the model chain from ice-avalanche and impact wave to single parameters considering rock-/ice-avalanche modeling by RAMMS and impact wave modeling by IBER. Assumptions on the initial rock-/ice-avalanche volume, calibration of the friction parameters in RAMMS and assumptions on erosion considered in RAMMS were parameters tested regarding their influence on overtopping parameters that are crucial for outburst flood modeling. Further the transformation of the RAMMS-output (flow height and flow velocities on the shoreline of the lake) into an inflow-hydrograph for IBER was also considered a possible source of uncertainties. Overtopping time, volume, and wave height as much as mean and maximum discharge were considered decisive parameters for the outburst flood modeling and were therewith

  20. The mobility of rock avalanches: disintegration, entrainment and deposition - a conceptual approach

    Science.gov (United States)

    Knapp, Sibylle; Mamot, Philipp; Krautblatter, Michael

    2015-04-01

    Massive rock slope failures cause more than 60% of all catastrophic landslide disasters. Failures usually progress through three consecutive phases: detachment, disintegration and flow. While significant advances have been achieved in modelling Rock Avalanche Phase 1 "Detachment" and Phase 3 "Flow", the crucial link between both during Phase 2 "Disintegration", is still poorly understood. Disintegration of the detached rock mass is often initiated by its first major impact with the ground surface. This is a preliminary setup of a PhD project in which we aim at understanding the importance of disintegration and on site conditions at the impact site on fluidization and mobilization. The TUM Landslides Group is experienced in near surface geophysics of rockwalls and under Alpine conditions and has also developed laboratory experience in testing resistivity and P-/S-wave velocity of anisotropic and fractured rocks in the laboratory. In addition, there is a more than ten year experience in the analysis of different magnitudes of rock slope failure. Many of these studies took part in the Wetterstein Mountains and close to the Zugspitze. In this project we plan to compare one very small (Steingerümpel, Rein valley, Germany, with 0.003 km³) and two larger test sites (Eibsee, Zugspitze area, Germany, with 0.3 km³ and Flims, Grisons, Switzerland, with 12 km³) situated in limestone rocks. From our preliminary work we know that the Steingerümpel bergsturz shows a low degree of fracturing in spite of a high impact; the latter ones are high-magnitude rock slope failures which both partially collapsed into a lake and were highly disintegrated and fluidized. We intend to use the smaller Eibsee rock avalanche as a training site where we can try to understand the full dynamics of the flow using sedimentology, geophysics and surface geomorphology which indicated compressive and extensional flow, superelevation and runups. Regarding entrainment processes, we will carry out a

  1. A simulated avalanche search and rescue mission induces temporary physiological and behavioural changes in military dogs.

    Science.gov (United States)

    Diverio, Silvana; Barbato, Olimpia; Cavallina, Roberta; Guelfi, Gabriella; Iaboni, Martina; Zasso, Renato; Di Mari, Walter; Santoro, Michele Matteo; Knowles, Toby G

    2016-09-01

    Saving human lives is of paramount importance in avalanche rescue missions. Avalanche military dogs represent an invaluable resource in these operations. However, their performance can be influenced by several environmental, social and transport challenges. If too severe, these are likely to activate a range of responses to stress, which might put at risk the dogs' welfare. The aim of this study was to assess the physiological and behavioural responses of a group of military dogs to a Simulated Avalanche Search and Rescue mission (SASR). Seventeen avalanche dogs from the Italian Military Force Guardia di Finanza (SAGF dogs) were monitored during a simulated search for a buried operator in an artificial avalanche area (SASR). Heart rate (HR), body temperature (RBT) and blood samples were collected at rest the day before the trial (T0), immediately after helicopter transport at the onset of the SASR (T1), after the discovery of the buried operator (T2) and 2h later (T3). Heart rate (HR), rectal body temperature (RBT), cortisol, aspartate aminotransferase (AST), creatine kinase (CK), non-esterified fatty acids (NEFA) and lactate dehydrogenase (LDH) were measured. During the search mission the behaviour of each SAGF dog was measured by focal animal sampling and qualitatively assessed by its handler and two observers. Inter-rater agreement was evaluated. Snow and environmental variables were also measured. All dogs successfully completed their search for the buried, simulated victim within 10min. The SASR was shown to exert significant increases on RBT, NEFA and cortisol (Ptransport, disembarking, and the search and rescue exercise. However, changes were moderate and limited over time, progressively decreasing with complete recovery at T3 except for sera cortisol that showed a slightly slower decline. More time walking within the search was related to lower RBT, conversely to walking. Standing still with head up and exploring with head-up were inversely related with HR

  2. A simulated avalanche search and rescue mission induces temporary physiological and behavioural changes in military dogs.

    Science.gov (United States)

    Diverio, Silvana; Barbato, Olimpia; Cavallina, Roberta; Guelfi, Gabriella; Iaboni, Martina; Zasso, Renato; Di Mari, Walter; Santoro, Michele Matteo; Knowles, Toby G

    2016-09-01

    Saving human lives is of paramount importance in avalanche rescue missions. Avalanche military dogs represent an invaluable resource in these operations. However, their performance can be influenced by several environmental, social and transport challenges. If too severe, these are likely to activate a range of responses to stress, which might put at risk the dogs' welfare. The aim of this study was to assess the physiological and behavioural responses of a group of military dogs to a Simulated Avalanche Search and Rescue mission (SASR). Seventeen avalanche dogs from the Italian Military Force Guardia di Finanza (SAGF dogs) were monitored during a simulated search for a buried operator in an artificial avalanche area (SASR). Heart rate (HR), body temperature (RBT) and blood samples were collected at rest the day before the trial (T0), immediately after helicopter transport at the onset of the SASR (T1), after the discovery of the buried operator (T2) and 2h later (T3). Heart rate (HR), rectal body temperature (RBT), cortisol, aspartate aminotransferase (AST), creatine kinase (CK), non-esterified fatty acids (NEFA) and lactate dehydrogenase (LDH) were measured. During the search mission the behaviour of each SAGF dog was measured by focal animal sampling and qualitatively assessed by its handler and two observers. Inter-rater agreement was evaluated. Snow and environmental variables were also measured. All dogs successfully completed their search for the buried, simulated victim within 10min. The SASR was shown to exert significant increases on RBT, NEFA and cortisol (Pstress probably induced by the addition of factors such as helicopter transport, disembarking, and the search and rescue exercise. However, changes were moderate and limited over time, progressively decreasing with complete recovery at T3 except for sera cortisol that showed a slightly slower decline. More time walking within the search was related to lower RBT, conversely to walking. Standing still

  3. Anthropogenic effect on avalanche and debris flow activity

    Directory of Open Access Journals (Sweden)

    S. A. Sokratov

    2015-04-01

    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.

  4. Seeded excitation avalanches in off-resonantly driven Rydberg gases

    CERN Document Server

    Simonelli, Cristiano; Masella, Guido; Asteria, Luca; Arimondo, Ennio; Ciampini, Donatella; Morsch, Oliver

    2016-01-01

    We report an experimental investigation of the facilitated excitation dynamics in off-resonantly driven Rydberg gases by separating the initial off-resonant excitation phase from the facilitation phase, in which successive facilitation events lead to excitation avalanches. We achieve this by creating a controlled number of initial seed excitations. Greater insight into the avalanche mechanism is obtained from an analysis of the full counting distributions. We also present simple mathematical models and numerical simulations of the excitation avalanches that agree well with our experimental results.

  5. Seeded excitation avalanches in off-resonantly driven Rydberg gases

    Science.gov (United States)

    Simonelli, C.; Valado, M. M.; Masella, G.; Asteria, L.; Arimondo, E.; Ciampini, D.; Morsch, O.

    2016-08-01

    We report an experimental investigation of the facilitated excitation dynamics in off-resonantly driven Rydberg gases by separating the initial off-resonant excitation phase from the facilitation phase, in which successive facilitation events lead to excitation avalanches. We achieve this by creating a controlled number of initial seed excitations. Greater insight into the avalanche mechanism is obtained from an analysis of the full counting distributions. We also present simple mathematical models and numerical simulations of the excitation avalanches that agree well with our experimental results.

  6. Avalanche of particles in evaporating coffee drops

    CERN Document Server

    Marin, Alvaro G; Snoeijer, Jacco; Lohse, Detlef

    2010-01-01

    The pioneering work of Deegan et al. [Nature 389, (1997)] showed how a drying sessile droplet suspension of particles presents a maximum evaporating flux at its contact line which drags liquid and particles creating the well known coffee stain ring. In this Fluid Dynamics Video, measurements using micro Particle Image Velocimetry and Particle Tracking clearly show an avalanche of particles being dragged in the last moments, for vanishing contact angles and droplet height. This explains the different characteristic packing of the particles in the layers of the ring: the outer one resembles a crystalline array, while the inner one looks more like a jammed granular fluid. Using the basic hydrodynamic model used by Deegan et al. [Phys. Rev. E 62, (2000)] it will be shown how the liquid radial velocity diverges as the droplet life comes to an end, yielding a good comparison with the experimental data.

  7. Scaling crossover for the average avalanche shape

    Science.gov (United States)

    Papanikolaou, Stefanos; Bohn, Felipe; Sommer, Rubem L.; Durin, Gianfranco; Zapperi, Stefano; Sethna, James P.

    2010-03-01

    Universality and the renormalization group claim to predict all behavior on long length and time scales asymptotically close to critical points. In practice, large simulations and heroic experiments have been needed to unambiguously test and measure the critical exponents and scaling functions. We announce here the measurement and prediction of universal corrections to scaling, applied to the temporal average shape of Barkhausen noise avalanches. We bypass the confounding factors of time-retarded interactions (eddy currents) by measuring thin permalloy films, and bypass thresholding effects and amplifier distortions by applying Wiener deconvolution. We show experimental shapes that are approximately symmetric, and measure the leading corrections to scaling. We solve a mean-field theory for the magnetization dynamics and calculate the relevant demagnetizing-field correction to scaling, showing qualitative agreement with the experiment. In this way, we move toward a quantitative theory useful at smaller time and length scales and farther from the critical point.

  8. Overspill avalanching in a dense reservoir network

    CERN Document Server

    Mamede, G L; Schneider, C M; de Araújo, J C; Herrmann, H J

    2012-01-01

    Sustainability of communities, agriculture, and industry is strongly dependent on an effective storage and supply of water resources. In some regions the economic growth has led to a level of water demand which can only be accomplished through efficient reservoir networks. Such infrastructures are not always planned at larger scale but rather made by farmers according to their local needs of irrigation during droughts. Based on extensive data from the upper Jaguaribe basin, one of the world's largest system of reservoirs, located in the Brazilian semiarid northeast, we reveal that surprisingly it self-organizes into a scale-free network exhibiting also a power-law in the distribution of the lakes and avalanches of discharges. With a new self-organized-criticality-type model we manage to explain the novel critical exponents. Implementing a flow model we are able to reproduce the measured overspill evolution providing a tool for catastrophe mitigation and future planning.

  9. Quantitative Analysis of Spectral Impacts on Silicon Photodiode Radiometers: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Myers, D. R.

    2011-04-01

    Inexpensive broadband pyranometers with silicon photodiode detectors have a non-uniform spectral response over the spectral range of 300-1100 nm. The response region includes only about 70% to 75% of the total energy in the terrestrial solar spectral distribution from 300 nm to 4000 nm. The solar spectrum constantly changes with solar position and atmospheric conditions. Relative spectral distributions of diffuse hemispherical irradiance sky radiation and total global hemispherical irradiance are drastically different. This analysis convolves a typical photodiode response with SMARTS 2.9.5 spectral model spectra for different sites and atmospheric conditions. Differences in solar component spectra lead to differences on the order of 2% in global hemispherical and 5% or more in diffuse hemispherical irradiances from silicon radiometers. The result is that errors of more than 7% can occur in the computation of direct normal irradiance from global hemispherical irradiance and diffuse hemispherical irradiance using these radiometers.

  10. CsI(Tl) with photodiodes for identifying subsurface radionuclide contamination

    International Nuclear Information System (INIS)

    At the US Department of Energy's Hanford Site near Richland, Washington, underground radioactive contamination exists as the result of leaks, spills, and intentional disposal of waste products from plutonium-production operations. Characterizing these contaminants in preparation for environmental remediation is a major effort now in progress. In this paper, a cylindrical (15 x 61 mm) CsI(Tl) scintillation detector with two side-mounted photodiodes has been developed to collect spectral gamma-ray data in subsurface contaminated formations at the U.S. Department of Energy's Hanford Site. It operates inside small-diameter, thick-wall steel pipes pushed into the ground to depths up to 20 m by a cone penetrometer. The detector provides a rugged, efficient, magnetic-field-insensitive means for identifying gamma-ray-emitting contaminants (mainly 137Cs and 60Co). Mounting two 3 x 30-mm photodiodes end-to-end on a flat area along the detector's side provides efficient light collection over the length of the detector

  11. Discrimination capability of avalanche counters detecting different ionizing particles

    International Nuclear Information System (INIS)

    The discrimination capability of avalanche counters to detect different ionizing particles has been studied using a 252Cf 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 32S ions are also reported. (orig.)

  12. UNIQUENESS OF SOLUTIONS FOR SEMICONDUCTOR EQUATIONS WITH AVALANCHE TERM

    Institute of Scientific and Technical Information of China (English)

    Xing Jiasheng; Wang Yuanming

    2000-01-01

    In this paper, we consider the initial and mixed boundary value problems for the semiconductor equations with avalanche term, the uniqueness of the weak solution for the semiconductor equation has been proved.

  13. Time performances of a scintillator-photodiode system

    International Nuclear Information System (INIS)

    Time characteristics of the system with surface-barrier photodiode are investigated by calculations on the example of photodiodes made of semiconductor with electron conductivity. The forms of charge pulses of scintillator-surface-barrier photodiode system are obtained at different values of the relation of scintillator luminescence time constant to the time of electron flight and holes. It is shown, that the charge pulse form of the system with surface-barrier photodiode is determined by silicon specific resistance and the constant of the scintillator luminescence time. The pulse form also depends on the diode side, where scintillator optical coupling is carried out: either from the side of golden contact or back contact side. The time of charge pulse increasing is determined by luminescence time for great constants of the scintillator luminescence time. Besides, an essential difference is observed in the time of pulse increasing in the case of generating nonequilibrium carriers by photons of scintillations and in the case of uniform generation by the depth of sensitive region. It is noted, that during generating the current carriers from the side of back contact a time delay from generation moment up to the moment of pulse occurrence, is observed. It is explained by the fact, that nonequilibrium carriers are generated in this case in the region of weak field intensity, and therefore the rate of their movement is inessential. The value of the potential slightly changes with the coordinate change in this region, i.e. the charge on a collecting electrode is not practically guided up to a certain moment of time during the movement of nonequilibrium carriers

  14. Radiation effects in ultraviolet sensitive SiC photodiodes

    International Nuclear Information System (INIS)

    We tested SiC photodiodes with Co-60 gamma rays up to a total dose of 22 Mrad(SiC) and 32 MeV protons up to a fluence of 9 x 1012 cm-2. They showed a decrease in sensitivity of about 50% at a dose of 1 Mrad. The same decrease or somewhat less was observed during proton irradiations when the fluence is converted to an applied dose. (authors)

  15. Flood avalanches in a semiarid basin with a dense reservoir network

    CERN Document Server

    Peter, Samuel J; Araújo, N A M; Herrmann, H J

    2014-01-01

    This study investigates flood avalanches in a dense reservoir network in the semiarid north-eastern Brazil. The population living in this area strongly depends on the availability of the water from this network. Water is stored during intense wet-season rainfall events and evaporates from the reservoir surface during the dry season. These seasonal changes are the driving forces behind the water dynamics in the network. The reservoir network and its connectivity properties during flood avalanches are investigated with a model called ResNetM, which simulates each reservoir explicitly. It runs on the basis of daily calculated water balances for each reservoir. A spilling reservoir contributes with water to the reservoir downstream, which can trigger avalanches affecting, in some cases, large fractions of the network. The main focus is on the study of the relation between the total amount of water stored and the largest observable cluster of connected reservoirs that overspill in the same day. It is shown that th...

  16. Effect of volume fraction on granular avalanche dynamics.

    Science.gov (United States)

    Gravish, Nick; Goldman, Daniel I

    2014-09-01

    We study the evolution and failure of a granular slope as a function of prepared volume fraction, ϕ(0). We rotated an initially horizontal layer of granular material (0.3-mm-diam glass spheres) to a 45° angle while we monitor the motion of grains from the side and top with high-speed video cameras. The dynamics of grain motion during the tilt process depended sensitively on ϕ(0)∈[0.58-0.63] and differed above or below the granular critical state, ϕ(c), defined as the onset of dilation as a function of increasing volume fraction. For ϕ(0)-ϕ(c)slopes experienced short, rapid, precursor compaction events prior to the onset of a sustained avalanche. Precursor compaction events began at an initial angle θ(0)=7.7±1.4° and occurred intermittently prior to the onset of an avalanche. Avalanches occurred at the maximal slope angle θ(m)=28.5±1.0°. Granular material at ϕ(0)-ϕ(c)>0 did not experience precursor compaction prior to avalanche flow, and instead experienced a single dilational motion at θ(0)=32.1±1.5° prior to the onset of an avalanche at θ(m)=35.9±0.7°. Both θ(0) and θ(m) increased with ϕ(0) and approached the same value in the limit of random close packing. The angle at which avalanching grains came to rest, θ(R)=22±2°, was independent of ϕ(0). From side-view high-speed video, we measured the velocity field of intermittent and avalanching flow. We found that flow direction, depth, and duration were affected by ϕ(0), with ϕ(0)-ϕ(c)0. Our study elucidates how initial conditions-including volume fraction-are important determinants of granular slope stability and the onset of avalanches. PMID:25314432

  17. Avalanche dynamics in evolution, growth, and depinning models

    Science.gov (United States)

    Paczuski, Maya; Maslov, Sergei; Bak, Per

    1996-01-01

    The dynamics of complex systems in nature often occurs in terms of punctuations, or avalanches, rather than following a smooth, gradual path. A comprehensive theory of avalanche dynamics in models of growth, interface depinning, and evolution is presented. Specifically, we include the Bak-Sneppen evolution model, the Sneppen interface depinning model, the Zaitsev flux creep model, invasion percolation, and several other depinning models into a unified treatment encompassing a large class of far from equilibrium processes. The formation of fractal structures, the appearance of 1/f noise, diffusion with anomalous Hurst exponents, Lévy flights, and punctuated equilibria can all be related to the same underlying avalanche dynamics. This dynamics can be represented as a fractal in d spatial plus one temporal dimension. The complex state can be reached either by tuning a parameter, or it can be self-organized. We present two exact equations for the avalanche behavior in the latter case. (1) The slow approach to the critical attractor, i.e., the process of self-organization, is governed by a ``gap'' equation for the divergence of avalanche sizes. (2) The hierarchical structure of avalanches is described by an equation for the average number of sites covered by an avalanche. The exponent γ governing the approach to the critical state appears as a constant rather than as a critical exponent. In addition, the conservation of activity in the stationary state manifests itself through the superuniversal result η=0. The exponent π for the Lévy flight jumps between subsequent active sites can be related to other critical exponents through a study of ``backward avalanches.'' We develop a scaling theory that relates many of the critical exponents in this broad category of extremal models, representing different universality classes, to two basic exponents characterizing the fractal attractor. The exact equations and the derived set of scaling relations are consistent with

  18. Avalanche dynamics in evolution, growth, and depinning models

    Energy Technology Data Exchange (ETDEWEB)

    Paczuski, M.; Maslov, S.; Bak, P. [Department of Physics, Brookhaven National Laboratory, Upton, New York 11973 (United States)]|[Department of Physics, State University of New York at Stony Brook, Stony Brook, New York 11794 (United States)

    1996-01-01

    Dynamics of complex systems in nature often occurs in terms of punctuations, or avalanches, rather than following a smooth, gradual path. Theory of avalanche dynamics in models of growth, interface depinning, and evolution is presented. Specifically, we include the Bak-Sneppen evolution model, Sneppen interface depinning model, Zaitsev flux creep model, invasion percolation, and several other depinning models into a unified treatment encompassing a large class of far from equilibrium processes. The formation of fractal structures, the appearance of 1/{ital f} noise, diffusion with anomalous Hurst exponents, L{acute e}vy flights, and punctuated equilibria can all be related to the same underlying avalanche dynamics. This dynamics can be represented as a fractal in {ital d} spatial plus one temporal dimension. The complex state can be reached either by tuning a parameter, or it can be self-organized. We present two {ital exact} equations for the avalanche behavior in the latter case. (1) The slow approach to the critical attractor, i.e., the process of self-organization, is governed by a ``gap`` equation for divergence of avalanche sizes. (2) The hierarchical structure of avalanches is described by an equation for the average number of sites covered by an avalanche. The exponent {gamma} governing the approach to the critical state appears as a constant rather than as a critical exponent. In addition, the conservation of activity in the stationary state manifests itself through the superuniversal result {eta}=0. The exponent {pi} for the L{acute e}vy flight jumps between subsequent active sites can be related to other critical exponents through a study of {open_quote}{open_quote}backward avalanches.{close_quote}{close_quote} We develop a scaling theory that relates many of the critical exponents in this broad category of extremal models, representing different universality classes, to two basic exponents characterizing the fractal attractor. (Abstract Truncated)

  19. Seeded excitation avalanches in off-resonantly driven Rydberg gases

    OpenAIRE

    Simonelli, Cristiano; Valado, Maria Martinez; Masella, Guido; Asteria, Luca; Arimondo, Ennio; Ciampini, Donatella; Morsch, Oliver

    2016-01-01

    We report an experimental investigation of the facilitated excitation dynamics in off-resonantly driven Rydberg gases by separating the initial off-resonant excitation phase from the facilitation phase, in which successive facilitation events lead to excitation avalanches. We achieve this by creating a controlled number of initial seed excitations. Greater insight into the avalanche mechanism is obtained from an analysis of the full counting distributions. We also present simple mathematical ...

  20. Vertically illuminated TW-UTC photodiodes for terahertz generation

    Science.gov (United States)

    Barrientos Z., Claudio M.; Calle G., Victor H.; Alvarez, Jaime A.; Mena, F. Patricio; Vukusic, Josip; Stake, Jan; Michael, Ernest A.

    2012-09-01

    More efficient and powerful continuous-wave photonic mixers as terahertz sources are motivated by the need of more versatile local oscillators for submillimeter/terahertz receiver systems. Uni-Travelling Carrier (UTC) photodiodes are very prospective candidates for reaching this objective, but so far only have been reported as lumped-elements or as edge-illuminated optical-waveguide travelling-wave (TW) devices. To overcome the associated power limitations of those implementations, we are developing a novel implementation of the UTC photodiodes which combines a travelingwave photomixer with vertical velocity-matched illumination in a distributed structure. In this implementation called velocity-matched travelling-wave uni-travelling carrier photodiode, it is possible to obtain in-situ velocity matching of the beat-fringes of the two angled laser beams with the submm/THz-wave on the stripline. In this way, minimum frequency roll-off is achieved by tuning the angle between the two laser beams. A first design of these TW-UTC PDs from our Terahertz Photonics Laboratory at University of Chile has been micro-fabricated at the MC2 cleanroom facility at Chalmers Technical University.

  1. Avalanches, plasticity, and ordering in colloidal crystals under compression

    Science.gov (United States)

    McDermott, D.; Reichhardt, C. J. Olson; Reichhardt, C.

    2016-06-01

    Using numerical simulations we examine colloids with a long-range Coulomb interaction confined in a two-dimensional trough potential undergoing dynamical compression. As the depth of the confining well is increased, the colloids move via elastic distortions interspersed with intermittent bursts or avalanches of plastic motion. In these avalanches, the colloids rearrange to minimize their colloid-colloid repulsive interaction energy by adopting an average lattice constant that is isotropic despite the anisotropic nature of the compression. The avalanches take the form of shear banding events that decrease or increase the structural order of the system. At larger compression, the avalanches are associated with a reduction of the number of rows of colloids that fit within the confining potential, and between avalanches the colloids can exhibit partially crystalline or anisotropic ordering. The colloid velocity distributions during the avalanches have a non-Gaussian form with power-law tails and exponents that are consistent with those found for the velocity distributions of gliding dislocations. We observe similar behavior when we subsequently decompress the system, and find a partially hysteretic response reflecting the irreversibility of the plastic events.

  2. Avalanche risk assessment for the link Osh - Bishkek, Kyrgyzstan

    Science.gov (United States)

    Nazarkulova, Kydyr

    2015-04-01

    The Bishkek-Osh road is main North-South ground transportation connection between the two major cities of Kyrgyzstan. One of the causes for frequent interruptions and closures between November and May is the avalanche risk due to local terrain characteristics and orographically induced precipitation maxima during winter. As a first step towards more effective prediction and implementation of mitigating measures the development of a digital avalanche inventory ('avalanche cadastre') has been initiated. This is aiming at modeling regional risk, and prioritizes the implementation of protective infrastructures in the most avalanche-prone zones. In addition, this helps with continuous monitoring of avalanche behaviour and the assessment of potential influence of climate change. For the parameterisation of models and support of decisions, details about avalanche incidences need to be collected. Historical data collected during Soviet time serve as an important baseline, complemented by more recent data. Overall, developing such a geo database shall be useful and effective for future planning at the Ministry of Emergency Services. This paper demonstrates important parameters to be collected and critical role of historical data as a baseline. Geodatabases are being developed on ArcGIS and used locally for planning preventive measures.

  3. Spatio-temporal avalanche forecasting with Support Vector Machines

    Directory of Open Access Journals (Sweden)

    A. Pozdnoukhov

    2011-02-01

    Full Text Available This paper explores the use of the Support Vector Machine (SVM as a data exploration tool and a predictive engine for spatio-temporal forecasting of snow avalanches. Based on the historical observations of avalanche activity, meteorological conditions and snowpack observations in the field, an SVM is used to build a data-driven spatio-temporal forecast for the local mountain region. It incorporates the outputs of simple physics-based and statistical approaches used to interpolate meteorological and snowpack-related data over a digital elevation model of the region. The interpretation of the produced forecast is discussed, and the quality of the model is validated using observations and avalanche bulletins of the recent years. The insight into the model behaviour is presented to highlight the interpretability of the model, its abilities to produce reliable forecasts for individual avalanche paths and sensitivity to input data. Estimates of prediction uncertainty are obtained with ensemble forecasting. The case study was carried out using data from the avalanche forecasting service in the Locaber region of Scotland, where avalanches are forecast on a daily basis during the winter months.

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

    International Nuclear Information System (INIS)

    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

  5. 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.

  6. On the complementariness of infrasound and seismic sensors for monitoring snow avalanches

    Directory of Open Access Journals (Sweden)

    A. Kogelnig

    2011-08-01

    Full Text Available The paper analyses and compares infrasonic and seismic data from snow avalanches monitored at the Vallée de la Sionne test site in Switzerland from 2009 to 2010. Using a combination of seismic and infrasound sensors, it is possible not only to detect a snow avalanche but also to distinguish between the different flow regimes and to analyse duration, average speed (for sections of the avalanche path and avalanche size. Different sensitiveness of the seismic and infrasound sensors to the avalanche regimes is shown. Furthermore, the high amplitudes observed in the infrasound signal for one avalanche were modelled assuming that the suspension layer of the avalanche acts as a moving turbulent sound source. Our results show reproducibility for similar avalanches on the same avalanche path.

  7. Use of silicon photodiode optically connected to scintillator in measurement of gamma dose rates

    Energy Technology Data Exchange (ETDEWEB)

    Gilar, O. (Tesla, Premysleni (Czechoslovakia). Vyzkumny Ustav Pristroju Jaderne Techniky); Petr, I. (Ceske Vysoke Uceni Technicke, Prague (Czechoslovakia). Fakulta Jaderna a Fysikalne Inzenyrska)

    1984-06-01

    Contributing to the signal which is produced in the photodiode by direct interaction with radiation may also be light photons produced by scintillation in the scintillator which is in optical contact with the photodiode. The scintillator/photodiode combination may increase sensitivity in comparison with the photodiode alone. The energy dependence of the detector will change according to the scintillator material and size. The configuration is described of a detector with CsI(Tl) scintillator. The detector is suitable for medium and large dose rates, the limiting factor for measuring small dose rates is the intensity of the photodiode dark current and its temperature dependence. A higher sensitivity of the designed detector configuration may be achieved by selecting a scintillator with a more suitable emission spectrum or by technological modifications of the photodiode.

  8. Guided-wave photodiode using through-absorber quantum-well-intermixing and methods thereof

    Energy Technology Data Exchange (ETDEWEB)

    Skogen, Erik J.

    2016-10-25

    The present invention includes a high-speed, high-saturation power detector (e.g., a photodiode) compatible with a relatively simple monolithic integration process. In particular embodiments, the photodiode includes an intrinsic bulk absorption region, which is grown above a main waveguide core including a number of quantum wells (QWs) that are used as the active region of a phase modulator. The invention also includes methods of fabricating integrated photodiode and waveguide assemblies using a monolithic, simplified process.

  9. Characterization methods for silicon photodiode and silicon sub-surface properties

    OpenAIRE

    Haapalinna, Atte

    2004-01-01

    This thesis considers the characterization of silicon photodiode and the applications of silicon photodiodes in precision metrology, and some aspects of the silicon material characterizations. Such material characterizations are required in the process of semiconductor device manufacturing, one example of which is the silicon photodiode manufacturing. The motivation for the research on radiometry reported in this thesis has been the development of optical metrology at the Helsinki Univers...

  10. High power high linearity waveguide photodiodes : measurement, modeling, and characterization for analog optical links

    OpenAIRE

    Draa, Meredith Nicole

    2010-01-01

    As analog optical links continue to mature and fulfill communication needs, the requirements for output power and linearity continue to be a main focus. The receiver end of a link is a limiting factor for such applications, and therefore photodiode research continues to be at the forefront of these issues. In order to compete, photodiodes need to be able to maintain high bandwidth, high power and high linearity simultaneously. The study of photodiodes for analog links has focused on linearity...

  11. Solution-based PbS photodiodes, integrable on ROIC, for SWIR detector applications

    OpenAIRE

    Heves, Emre; Öztürk, Cem; Ozturk, Cem; Özgüz, Volkan Hüsnü; Ozguz, Volkan Husnu; Gürbüz, Yaşar; Gurbuz, Yasar

    2013-01-01

    Photodiodes, based on PbS colloidal quantum dots (CQD), are realized on both silicon substrates and the replicas of the read-out integrated circuits (ROICs) to demonstrate the first, fully integrated focal plane arrays. Careful optimization of PbS CQD film formation and ligand exchange process, together with optimized process steps, resulted in high performance, monolithically integrable photodiodes. High quantum efficiencies of 32% are achieved for photodiodes on Si substrates and high respo...

  12. Distribution of joint local and total size and of extension for avalanches in the Brownian force model.

    Science.gov (United States)

    Delorme, Mathieu; Le Doussal, Pierre; Wiese, Kay Jörg

    2016-05-01

    The Brownian force model is a mean-field model for local velocities during avalanches in elastic interfaces of internal space dimension d, driven in a random medium. It is exactly solvable via a nonlinear differential equation. We study avalanches following a kick, i.e., a step in the driving force. We first recall the calculation of the distributions of the global size (total swept area) and of the local jump size for an arbitrary kick amplitude. We extend this calculation to the joint density of local and global sizes within a single avalanche in the limit of an infinitesimal kick. When the interface is driven by a single point, we find new exponents τ_{0}=5/3 and τ=7/4, depending on whether the force or the displacement is imposed. We show that the extension of a "single avalanche" along one internal direction (i.e., the total length in d=1) is finite, and we calculate its distribution following either a local or a global kick. In all cases, it exhibits a divergence P(ℓ)∼ℓ^{-3} at small ℓ. Most of our results are tested in a numerical simulation in dimension d=1. PMID:27300864

  13. Functioning of the avalanche starting zones which undergo snow-transport by wind: Field observations and computer modeling

    Science.gov (United States)

    Sivardière, F.; Castelle, T.; Guyomarc'h, G.; Mérindol, L.; Buisson, L.

    1995-11-01

    For two years, three French and Swiss laboratories have been making field observations and measurements on two high altitude slopes in a Northern French Alps site. The aim of this work is to study the functioning of the avalanche sites which, in their starting zones, undergo snow-transport by wind. The experimental site is located in the French Alps, at 2,800 m, above Grenoble. It is an open area, equipped with an automatic meteorological station and an altitude laboratory. The two slopes that are studied face East. One of them is artificially released but the other has a natural avalanche activity. The investigations concern: -snow deposition in avalanche starting zones; -temporal evolution of the snowpack characteristics; -avalanche release. For the field observations and measurements, continuous recording of the meteorological conditions on the site, photogrammetrical techniques and two snow depth profiles, as well as stratigraphical snow profiles and video are used. The computer modeling is based on existing computer models developed by the CEMAGREF-Nivologie (ELSA) and the CEN/Météo-France (SAFRAN-CROCUS-MEPRA), which analyse the snowpack and its stability. The field observations and measurements aim at improving snow-transport by wind modeling modules, in order to improve their whole analysis.

  14. Avalanche breakdown of the quantum hall effects

    CERN Document Server

    Komiyama, S

    1999-01-01

    Heat stability of two-dimensional electron gas (2DEG) systems in the integer quantum hall effect (IQHE) regime is discussed, and a heat instability is suggested to be the intrinsic mechanism behind the breakdown of the IQHE. Phenomenological argument is provided to suggest that the 2DEG system in the IQHE state becomes thermally unstable when the Hall electric field E sub y reaches a threshold value E sub b. Above E sub b , excited nonequilibrium electrons (holes), which are initially present in the conductor as the temperature fluctuation, are accelerated by E sub y and the 2DEG thereby undergoes a transition to a warm dissipative state. The critical field, E sub b , of this abrupt transition is theoretically estimated and shown to be in fare agreement with experimentally reported values. Consideration of the dynamics of electrons suggests that the transition is a process of avalanche electron-hole pair multiplication, in which a small number of non-equilibrium carriers, gains kinetic energy within a Landau ...

  15. Granular avalanches down inclined and vibrated planes

    Science.gov (United States)

    Gaudel, Naïma; Kiesgen de Richter, Sébastien; Louvet, Nicolas; Jenny, Mathieu; Skali-Lami, Salaheddine

    2016-09-01

    In this article, we study granular avalanches when external mechanical vibrations are applied. We identify conditions of flow arrest and compare with the ones classically observed for nonvibrating granular flows down inclines [Phys. Fluids 11, 542 (1999), 10.1063/1.869928]. We propose an empirical law to describe the thickness of the deposits with the inclination angle and the vibration intensity. The link between the surface velocity and the depth of the flow highlights a competition between gravity and vibrations induced flows. We identify two distinct regimes: (a) gravity-driven flows at large angles where vibrations do not modify dynamical properties but the deposits (scaling laws in this regime are in agreement with the literature for nonvibrating granular flows) and (b) vibrations-driven flows at small angles where no flow is possible without applied vibrations (in this last regime, the flow behavior can be properly described by a vibration induced activated process). We show, in this study, that granular flows down inclined planes can be finely tuned by external mechanical vibrations.

  16. OPTIMIZING THROUGH CO-EVOLUTIONARY AVALANCHES

    Energy Technology Data Exchange (ETDEWEB)

    S. BOETTCHER; A. PERCUS

    2000-08-01

    We explore a new general-purpose heuristic for finding high-quality solutions to hard optimization problems. The method, called extremal optimization, is inspired by ''self-organized critically,'' a concept introduced to describe emergent complexity in many physical systems. In contrast to Genetic Algorithms which operate on an entire ''gene-pool'' of possible solutions, extremal optimization successively replaces extremely undesirable elements of a sub-optimal solution with new, random ones. Large fluctuations, called ''avalanches,'' ensue that efficiently explore many local optima. Drawing upon models used to simulate far-from-equilibrium dynamics, extremal optimization complements approximation methods inspired by equilibrium statistical physics, such as simulated annealing. With only one adjustable parameter, its performance has proved competitive with more elaborate methods, especially near phase transitions. Those phase transitions are found in the parameter space of most optimization problems, and have recently been conjectured to be the origin of some of the hardest instances in computational complexity. We will demonstrate how extremal optimization can be implemented for a variety of combinatorial optimization problems. We believe that extremal optimization will be a useful tool in the investigation of phase transitions in combinatorial optimization problems, hence valuable in elucidating the origin of computational complexity.

  17. 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.

  18. A Novel Photodiode for Reflectance Pulse Oximetry in low-power applications

    DEFF Research Database (Denmark)

    Haahr, Rasmus Grønbek; Duun, Sune; Birkelund, Karen;

    2007-01-01

    The amount of light collected is crucial for low-power applications of pulse oximetry. In this work a novel ring-shaped backside photodiode has been developed for a wearable reflectance pulse oximeter. The photodiode is proven to work with a dual LED with wavelengths of 660 nm and 940 nm. For the......The amount of light collected is crucial for low-power applications of pulse oximetry. In this work a novel ring-shaped backside photodiode has been developed for a wearable reflectance pulse oximeter. The photodiode is proven to work with a dual LED with wavelengths of 660 nm and 940 nm...

  19. Combination of a silicon photodiode and a scintillator as a dose rate detector

    Energy Technology Data Exchange (ETDEWEB)

    Gilar, O. (Tesla, Premysleni (Czechoslovakia). Vyzkumny Ustav Pristroju Jaderne Techniky); Petr, I. (Ceske Vysoke Uceni Technicke, Prague (Czechoslovakia). Fakulta Jaderna a Fysikalne Inzenyrska)

    1985-03-16

    The combination of a silicon photodiode adjacent to a CsI(Tl) scintillator as a detector of ..gamma..-rays is described. Theoretical conclusions are verified by an experiment and prove that the photodiode absorption spectrum as well as the quantum efficiency can be varied by an appropriate photodiode technology. The contribution of scintillation photons emitted by the CsI(Tl) scintillator in the photon field can enhance the total photocurrent more than an order of magnitude compared to the current response of the photodiode alone, placed in a photon field of equal exposure rate.

  20. Infrasonic monitoring of snow avalanches in the Alps

    Science.gov (United States)

    Marchetti, E.; Ulivieri, G.; Ripepe, M.; Chiambretti, I.; Segor, V.

    2012-04-01

    Risk assessment of snow avalanches is mostly related to weather conditions and snow cover. However a robust risk validation requires to identify all avalanches occurring, in order to compare predictions to real effects. For this purpose on December 2010 we installed a permanent 4-element, small aperture (100 m), infrasound array in the Alps, after a pilot experiment carried out in Gressonay during the 2009-2010 winter season. The array has been deployed in the Ayas Valley, at an elevation of 2000 m a.s.l., where natural avalanches are expected and controlled events are regularly performed. The array consists into 4 Optimic 2180 infrasonic microphones, with a sensitivity of 10-3 Pa in the 0.5-50 Hz frequency band and a 4 channel Guralp CMG-DM24 A/D converter, sampling at 100 Hz. Timing is achieved with a GPS receiver. Data are transmitted to the Department of Earth Sciences of the University of Firenze, where data is recorded and processed in real-time. A multi-channel semblance is carried out on the continuous data set as a function of slowness, back-azimuth and frequency of recorded infrasound in order to detect all avalanches occurring from the back-ground signal, strongly affected by microbarom and mountain induced gravity waves. This permanent installation in Italy will allow to verify the efficiency of the system in short-to-medium range (2-8 km) avalanche detection, and might represent an important validation to model avalanches activity during this winter season. Moreover, the real-time processing of infrasonic array data, might strongly contribute to avalanche risk assessments providing an up-to-description of ongoing events.

  1. Epitaxial InGaAsP/InP photodiode for registration of InP scintillation

    Science.gov (United States)

    Luryi, S.; Kastalsky, A.; Gouzman, M.; Lifshitz, N.; Semyonov, O.; Stanacevic, M.; Subashiev, A.; Kuzminsky, V.; Cheng, W.; Smagin, V.; Chen, Z.; Abeles, J. H.; Chan, W. K.; Shellenbarger, Z. A.

    2010-10-01

    Operation of semiconductor scintillators requires optically tight integration of the photoreceiver system on the surface of the scintillator slab. We have implemented an efficient and fast quaternary InGaAsP pin photodiode, epitaxially grown on the surface of an InP scintillator wafer and sensitive to InP luminescence. The diode is characterized by an extremely low room-temperature dark current, about 1 nA/cm2 at the reverse bias of 2 V. The low leakage makes possible a sensitive readout circuitry even though the diode has a large area (1×1 mm2) and therefore large capacitance (50 pF). Results of electrical, optical and radiation testing of the diodes are presented. Detection of individual α-particles and γ-photons is demonstrated.

  2. Hard disk drive based microsecond x-ray chopper for characterization of ionization chambers and photodiodes

    Science.gov (United States)

    Müller, O.; Lützenkirchen-Hecht, D.; Frahm, R.

    2015-03-01

    A fast X-ray chopper capable of producing ms long X-ray pulses with a typical rise time of few μs was realized. It is ideally suited to investigate the temporal response of X-ray detectors with response times of the order of μs to ms, in particular, any kind of ionization chambers and large area photo diodes. The drive mechanism consists of a brushless DC motor and driver electronics from a common hard disk drive, keeping the cost at an absolute minimum. Due to its simple construction and small dimensions, this chopper operates at home lab based X-ray tubes and synchrotron radiation sources as well. The dynamics of the most important detectors used in time resolved X-ray absorption spectroscopy, namely, ionization chambers and Passivated Implanted Planar Silicon photodiodes, were investigated in detail. The results emphasize the applicability of this X-ray chopper.

  3. Hard disk drive based microsecond x-ray chopper for characterization of ionization chambers and photodiodes

    Energy Technology Data Exchange (ETDEWEB)

    Müller, O., E-mail: o.mueller@uni-wuppertal.de; Lützenkirchen-Hecht, D.; Frahm, R. [Bergische Universität Wuppertal, Gaußstraße 20, Wuppertal 42119 (Germany)

    2015-03-15

    A fast X-ray chopper capable of producing ms long X-ray pulses with a typical rise time of few μs was realized. It is ideally suited to investigate the temporal response of X-ray detectors with response times of the order of μs to ms, in particular, any kind of ionization chambers and large area photo diodes. The drive mechanism consists of a brushless DC motor and driver electronics from a common hard disk drive, keeping the cost at an absolute minimum. Due to its simple construction and small dimensions, this chopper operates at home lab based X-ray tubes and synchrotron radiation sources as well. The dynamics of the most important detectors used in time resolved X-ray absorption spectroscopy, namely, ionization chambers and Passivated Implanted Planar Silicon photodiodes, were investigated in detail. The results emphasize the applicability of this X-ray chopper.

  4. Identification of radiation induced dark current sources in pinned photodiode CMOS image sensors

    International Nuclear Information System (INIS)

    This paper presents an investigation of Total Ionizing Dose (TID) induced dark current sources in Pinned Photodiodes (PPD) CMOS Image Sensors based on pixel design variations. The influence of several layout parameters is studied. Only one parameter is changed at a time enabling the direct evaluation of its contribution to the observed device degradation. By this approach, the origin of radiation induced dark current in PPD is localized on the pixel layout. The PPD peripheral shallow trench isolation does not seem to play a role in the degradation. The PPD area and a transfer gate contribution independent of the pixel dimensions appear to be the main sources of the TID induced dark current increase. This study also demonstrates that applying a negative voltage on the transfer gate during integration strongly reduces the radiation induced dark current. (authors)

  5. Arrest of Avalanche Propagation by Discontinuities on Snow Cover

    Science.gov (United States)

    Frigo, B.; Chiaia, B.

    2009-04-01

    Considering the spatial variability of the snow cover, the paper analyses, in the framework of Fracture Mechanics, the Mode II fracture propagation on snow cover that leads to large dry slab avalanches. Under the hypothesis of a perfectly brittle phenomenon, avalanche triggering is usually investigated numerically by means of Linear Elastic Fracture Mechanics (McClung, 1979; Chiaia et al., 2008). Since, however, the real phenomenon is intrinsically dynamical, another aspect to investigate is represented by dynamic fracture propagation. In this paper, we model dynamic crack propagation into a dry snow slab, to assess the possibility of crack arrest due to the presence of weak zones distributed along the snow slope. As a consequence of the first triggering mechanism (the Mode II fracture propagation on the weak plane), the secondary Mode I crack propagation in the crown is studied by means of numerical simulations based on Dynamic Elastic Fracture Mechanics and on the theory of crack arresters. By taking into account kinetic energy and using the FEM software FRANC 2D (Wawrzynek and Ingraffea, 1993), several paths of crown fracture propagation and their stability have been investigated. The snowpack is considered as a linear-elastic plate (2D problem), whose physical and mechanical parameters are chosen according to classical literature values. To investigate the possible arrest of crown fracture, we apply the theory of crack arresters, usually adopted for pipelines and perforated steel sheets fracture problems. To study crack arrest, different crack paths are simulated, in discontinuous (equipped with different shapes and geometries of artificial voids) snowpacks. The simulations show the effectiveness of these weak zones, to reduce substantially the crack driving force of the propagating fracture. This means that, increasing spatial variability tends to stabilize the snow slope, eventually splitting a major avalanche event into smaller, independent avalanches. Our

  6. Crosstalk properties of the CMS HCAL hybrid photodiode

    CERN Document Server

    Cushman, P B; Pearson, N; Elias, J; Freeman, J; Green, D; Los, S; Ronzhin, A

    2003-01-01

    The requirements of large dynamic range, 40 MHz readout and 4T magnetic field of the CMS Hadronic calorimeter have led to the development of a custom Hybrid PhotoDiode (HPD). In the last 5 years many improvements have been made in cooperation with DEP B.V. Delft Electronische Producten, Roden, Netherlands. and Canberra Semiconductor N.V., Olen, Belgium. to the basic HPD concept to improve the performance. A 200-mum thick 19-channel PIN diode array with various surface treatments has been developed to ensure fast pulse behavior and low optical and capacitive crosstalk.

  7. Laser and photodiode environmental evaluation for the Versatile Link project

    CERN Document Server

    Troska, Jan; Detraz, S; Olanterä, L; Stejskal, P; Sigaud, C; Soos, C; Vasey, F

    2013-01-01

    We summarize the results obtained in a series of radiation tests of candidate laser and photodiode components for use in the Versatile Transceiver (VTRx), the front-end component of the Versatile Link. We have carried out radiation testing at a full spectrum of sources (neutrons, pions, gammas) and can now compare the results and show that the range of components that meet the radiation tolerance requirements is rather large. In addition, devices have been operated in a high magnetic field to qualify them for use in (HL-) LHC detectors.

  8. Displacement damage effects in pinned photodiode CMOS image sensors

    International Nuclear Information System (INIS)

    This paper investigates the effects of displacement damage in Pinned Photodiode (PPD) CMOS Image Sensors (CIS) using proton and neutron irradiations. The DDD ranges from 12 TeV/g to 1.2 * 106 TeV/g. Particle fluence up to 5 * 1014 n.cm-2 is investigated to observe electro-optic degradation in harsh environments. The dark current is also investigated and it would appear that it is possible to use the dark current spectroscopy in PPD CIS. The dark current random telegraph signal is also observed and characterized using the maximum transition amplitude. (authors)

  9. Innovative Detection System of Ochratoxin A by Thin Film Photodiodes

    OpenAIRE

    Riccardo Scipinotti; Alessandra Ricelli; Augusto Nascetti; Corrado Fanelli; Gianpiero de Cesare; Domenico Caputo

    2007-01-01

    In this work we present, for the first time, a rapid, compact and innovative method for detection of Ochratoxin A (OTA) based on hydrogenated amorphous silicon (a-Si:H) sensors. 2 μl of acidified toluene containing OTA at different concentrations were spotted on the silica side of a High Performance Thin Layer Cromatography plate and aligned with a a-Si:H p-i-n photodiode deposited by Plasma Enhanced Chemical Vapor Deposition on a different glass substrate. As an UV radiation excites the myco...

  10. Development of a testbed for flexible a-Si:H photodiode sensing arrays

    Science.gov (United States)

    Dominguez, Alfonso; Kunnen, George; Vetrano, Michael; Smith, Joseph; Marrs, Michael; Allee, David R.

    2013-05-01

    Large area, flexible sensing arrays for imaging, biochemical sensing and radiation detection are now possible with the development of flexible active matrix display technology. In particular, large-area flexible imaging arrays can provide considerable advancement in defense and security industries because of their inherent low manufacturing costs and physical plasticity that allows for increased adaptability to non-planar mounting surfaces. For example, a flexible array of photodetectors and lenslets formed into a cylinder could image simultaneously with a 360 degree view without the need for expensive bulky optics or a gimbaled mount. Here we report the design and development of a scalable 16x16 pixel testbed for flexible sensor arrays using commercial-off-the-shelf (COTS) parts and demonstrate the capture of a shadow image with an array of photodiodes and active pixel sensors on a plastic substrate. The image capture system makes use of an array of low-noise, InGaZnO active pixel amplifiers to detect changes in current in 2.4 μm-thick reverse-biased a-Si:H PIN diodes. A thorough characterization of the responsivity, detectivity, and optical gain of an a- Si:H photodiode is also provided. At the back end, analog capture circuitry progressively scans the array and constructs an image based on the electrical activity in each pixel. The use of correlated-double-sampling to remove fixed pattern noise is shown to significantly improve spatial resolution due to process variations. The testbed can be readily adapted for the development of neutron, alpha-particle, or X-ray detection arrays given an appropriate conversion layer.

  11. Numerical modeling of debris avalanches at Nevado de Toluca (Mexico): implications for hazard evaluation and mapping

    Science.gov (United States)

    Grieco, F.; Capra, L.; Groppelli, G.; Norini, G.

    2007-05-01

    The present study concerns the numerical modeling of debris avalanches on the Nevado de Toluca Volcano (Mexico) using TITAN2D simulation software, and its application to create hazard maps. Nevado de Toluca is an andesitic to dacitic stratovolcano of Late Pliocene-Holocene age, located in central México near to the cities of Toluca and México City; its past activity has endangered an area with more than 25 million inhabitants today. The present work is based upon the data collected during extensive field work finalized to the realization of the geological map of Nevado de Toluca at 1:25,000 scale. The activity of the volcano has developed from 2.6 Ma until 10.5 ka with both effusive and explosive events; the Nevado de Toluca has presented long phases of inactivity characterized by erosion and emplacement of debris flow and debris avalanche deposits on its flanks. The largest epiclastic events in the history of the volcano are wide debris flows and debris avalanches, occurred between 1 Ma and 50 ka, during a prolonged hiatus in eruptive activity. Other minor events happened mainly during the most recent volcanic activity (less than 50 ka), characterized by magmatic and tectonic-induced instability of the summit dome complex. According to the most recent tectonic analysis, the active transtensive kinematics of the E-W Tenango Fault System had a strong influence on the preferential directions of the last three documented lateral collapses, which generated the Arroyo Grande and Zaguàn debris avalanche deposits towards E and Nopal debris avalanche deposit towards W. The analysis of the data collected during the field work permitted to create a detailed GIS database of the spatial and temporal distribution of debris avalanche deposits on the volcano. Flow models, that have been performed with the software TITAN2D, developed by GMFG at Buffalo, were entirely based upon the information stored in the geological database. The modeling software is built upon equations

  12. Dynamic rock fragmentation: thresholds for long runout rock avalanches

    Directory of Open Access Journals (Sweden)

    E.T. Bowman

    2014-10-01

    Full Text Available The dynamic fragmentation of rock within rock avalanches is examined using the fragmentation concepts introduced by Grady and co-workers. The analyses use typical material values for weak chalk and limestone in order to determine theoretical strain rate thresholds for dynamic fragmentation and resulting fragment sizes. These are found to compare favourably with data obtained from field observations of long runout rock avalanches and chalk cliff collapses in spite of the simplicity of the approach used. The results provide insight as to the energy requirements to develop long runout behaviour and hence may help to explain the observed similarities between large rock avalanches and much smaller scale chalk cliff collapses as seen in Europe.

  13. Universality in the mean spatial shape of avalanches

    Science.gov (United States)

    Thiery, Thimothée; Le Doussal, Pierre

    2016-05-01

    Quantifying the universality of avalanche observables beyond critical exponents is of current great interest in theory and experiments. Here, we compute the spatial shape of avalanches in the universality class of the depinning of elastic interfaces in random media. We provide for the first time an analytically tractable definition of the spatial shape, accessible in experiments, and study the mean spatial shape of avalanches at fixed size centered around their starting point (seed). We calculate the associated universal scaling functions, both in a mean-field model and beyond. Notably, they are predicted to exhibit a cusp singularity near the seed. The results are in good agreement with a numerical simulation of an elastic line.

  14. Avalanche dynamics in evolution, growth, and depinning models

    CERN Document Server

    Paczuski, M; Bak, P

    1995-01-01

    The dynamics of complex systems in nature often occurs in terms of punctuations, or avalanches, rather than following a smooth, gradual path. A comprehensive theory of avalanche dynamics in models of growth, interface depinning, and evolution is presented. Specifically, we include the Bak-Sneppen evolution model, the Sneppen interface depinning model, the Zaitsev flux creep model, invasion percolation, and several other depinning models into a unified treatment encompassing a large class of far from equilibrium processes. The formation of fractal structures, the appearance of 1/f noise, diffusion with anomalous Hurst exponents, Levy flights, and punctuated equilibria can all be related to the same underlying avalanche dynamics. This dynamics can be represented as a fractal in d spatial plus one temporal dimension. We develop a scaling theory that relates many of the critical exponents in this broad category of extremal models, representing different universality classes, to two basic exponents characterizing ...

  15. Different hierarchy of avalanches observed in the Bak-Sneppen evolution model

    CERN Document Server

    Li, W

    2000-01-01

    We introduce a new quantity, average fitness, into the Bak-Sneppen evolution model. Through the new quantity, a different hierarchy of avalanches is observed. The gap equation, in terms of the average fitness, is presented to describe the self-organization of the model. It is found that the critical value of the average fitness can be exactly obtained. Based on the simulations, two critical exponents, avalanche distribution and avalanche dimension, of the new avalanches are given.

  16. Modeling and monitoring avalanches caused by rain-on-snow events

    Science.gov (United States)

    Havens, S.; Marshall, H. P.; Trisca, G. O.; Johnson, J. B.; Nicholson, B.

    2014-12-01

    Direct-action avalanches occur during large storm cycles in mountainous regions, when stresses on the snowpack increase rapidly due to the load of new snow and outpace snow strengthening due to compaction. If temperatures rise above freezing during the storm and snowfall turns to rain, the near-surface snow undergoes rapid densification caused by the introduction of liquid water. This shock to the snowpack, if stability is near critical, can cause widespread immediate avalanching due to the large induced strain rates in the slab, followed by secondary delayed avalanches due to both the increased load as well as water percolation to the depth of a weak layer. We use the semi-empirical SNOow Slope Stability model (SNOSS) to estimate the evolution of stability prior to large avalanches during rain-on-snow events on Highway 21 north of Boise, Idaho. We have continuously monitored avalanche activity using arrays of infrasound sensors in the avalanche-prone section of HW21 near Stanley, in collaboration with the Idaho Transportation Department's avalanche forecasting program. The autonomous infrasound avalanche monitoring system provides accurate timing of avalanche events, in addition to capturing avalanche dynamics during some major releases adjacent to the array. Due to the remote location and low winter traffic volume, the highway is typically closed for multiple days during major avalanche cycles. Many major avalanches typically release naturally and reach the road, but due the complex terrain and poor visibility, manual observations are often not possible until several days later. Since most avalanche programs typically use explosives on a regular basis to control slope stability, the infrasound record of avalanche activity we have recorded on HW21 provides a unique opportunity to study large naturally triggered avalanches. We use a first-order physically based stability model to estimate the importance of precipitation phase, amount, and rate during major rain

  17. A Novel Ring Shaped Photodiode for Reflectance Pulse Oximetry in Wireless Applications

    DEFF Research Database (Denmark)

    Duun, Sune; Haahr, Rasmus Grønbek; Birkelund, Karen;

    2007-01-01

    We present a pulse oximeter for use in home-care applications in a sticking patch with integrated electronics. The core in the pulse oximeter is a large ring shaped backside silicon pn photodiode placed around a Ledtronics dual LED with wavelengths of 660 nm and 940 nm. The concentric photodiode...

  18. 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 cappin

  19. Study on the formation of current characteristics of a silicon photodiode with rectifying barriers

    Directory of Open Access Journals (Sweden)

    Karimov A. V.

    2013-02-01

    Full Text Available The article presents the results of studies on silicon photodiode double-barrier structure with back-to-back rectifying junctions «metal — semiconductor» in the photodiode and photovoltaic modes. Such structures are of interest for the development of input devices for weak optical signals.

  20. Avalanche shape and exponents beyond mean-field theory

    Science.gov (United States)

    Dobrinevski, Alexander; Le Doussal, Pierre; Jörg Wiese, Kay

    2014-12-01

    Elastic systems, such as magnetic domain walls, density waves, contact lines, and cracks, are pinned by substrate disorder. When driven, they move via avalanches, with power law distributions of size, duration and velocity. Their exponents, and the shape of an avalanche, defined as its mean velocity as a function of time, were studied. They are known approximatively from experiments and simulations, and were predicted from mean-field models, such as the Brownian force model (BFM), where each point of the elastic interface sees a force field which itself is a random walk. As we showed in EPL, 97 (2012) 46004, the BFM is the starting point for an \\varepsilon = d\\text{c}-d expansion around the upper critical dimension, with d\\text{c}=4 for short-ranged elasticity, and d\\text{c}=2 for long-ranged elasticity. Here we calculate analytically the O}(\\varepsilon) , i.e. 1-loop, correction to the avalanche shape at fixed duration T, for both types of elasticity. The exact expression, though different from the phenomenological form presented by Laurson et al. in Nat. Commun., 4 (2013) 2927, is well approximated by ≤ft_T≃ [ Tx(1-x)]γ-1 \\exp≤ft( A}≤ft[\\frac12-x\\right]\\right) , 0 < x < 1. The asymmetry A}≈ - 0.336 (1-d/d\\text{c}) is negative for d close to d\\text{c} , skewing the avalanche towards its end, as observed in numerical simulations in d = 2 and 3. The exponent γ=(d+\\zeta)/z is given by the two independent exponents at depinning, the roughness ζ and the dynamical exponent z. We propose a general procedure to predict other avalanche exponents in terms of ζ and z. We finally introduce and calculate the shape at fixed avalanche size, not yet measured in experiments or simulations.

  1. Fast microprogrammed fields sensing with photodiode matrix array

    International Nuclear Information System (INIS)

    For higher speed image processing, it is better to output solely lines that store information and to skip the others than to read out all the pixels and then to select out large store of video data. In order to have the two-dimensional spectroscopic measurments timeresolved, the principle of video data reduction was realized by means of modular camera with photodiode matrix. A Reticon matrix array of 256 x 256 photodiodes with access and reset switches as well as x and y readout shift registers on chip has been chosen. Camera control and programmed row clock operation, as well as remote programming and transfer of control words to the camera is described. The analogue video data that are controlled by this system are converted by a 10 MHz A/D converter into 12 bit-words. Using a very rapid accumulation device, a programmed number of digitized pixel data of the same row but of different neighbouring columns can be added on-line. This will limit the volume of data and raise the signal-to-noise ratio but decrease the local resolution

  2. Linearity of P-N junction photodiodes under pulsed irradiation

    CERN Document Server

    Stuik, R

    2002-01-01

    The dependence of the sensitivity on the radiation pulse length for a P-N junction photodiode has been investigated over an extended range of pulse lengths, from 170 ns to 1.2 ms. The power incident on the diode surface was varied between 1.6 and 118 mW. A novel method was used to generate the light pulses with variable length, while keeping the temporal pulse shape and the intensity constant. The method consists of using a rotating mirror in combination with a DC light source, in our case at 633 and 532 nm. In this way, the pulse shape only depends on the geometry of the setup, with the pulse length solely determined by the rotation frequency of the mirror. No further calibration is needed for determination of the pulse intensity and shape. Accuracies obtained are better than 2%, mainly determined by instabilities in the setup. The sensitivity of an IRD AXUV-100 photodiode was studied, both with and without a reverse bias voltage applied. At unbiased conditions and irradiation levels well below the saturatio...

  3. Modeling Scintillator-photodiodes As Detectors For Megavoltage Computed Tomography

    CERN Document Server

    Monajemi, T T

    2004-01-01

    The imaging characteristics of a cadmium tungstate, CdWO 4, detector was modeled and measured in 1.25 MeV and 6 MV beams. The detector includes eight CdWO4 crystals, each 2.75 x 8 x 10 mm 3, bonded together and in contact with sixteen silicon photodiodes such that, each crystal covers two photodiodes. The characteristics investigated are the frequency dependent modulation transfer function, MTF (f), noise power spectrum, NPS (f), and detective quantum efficiency, DQE (f). The tools used in modeling these characteristics include the Monte Carlo simulation codes, EGSnrc and DETECT2000, for high energy and optical photons, respectively. The DQE of the detector was found to be approximately constant at 26% and 19% for 1.25 MeV and 6 MV photons up to a spatial frequency of 0.16 cycles/mm, respectively. Due to pulse to pulse fluctuations in the output of the linear accelerator, the NPS(f) and DQE(f) were not verified experimentally in a 6 MV beam.

  4. Metal-diamond semiconductor interface and photodiode application

    International Nuclear Information System (INIS)

    Carrier transport mechanism at p-diamond/metal interfaces are studied by analyzing dependencies of specific contact resistance (ρc) on measurement temperature and acceptor concentration (NA). A variety of metals, such as Ti, Mo, Cr (carbide-forming metals), Pd, and Co (carbon-soluble metals), are deposited on boron-doped polycrystalline diamond layers, and the ρc values are measured by a transmission line method. Thermal annealing which produces metallurgical reactions between diamond and metal reduces Schottky barrier heights of the contact metals to a constant value. It is found that use of a metal compound which does not react with diamond at elevated temperatures is the key to develop the thermally stable Schottky contact material for p-diamond. Along this guideline, we test the suitability of tungsten carbide (WC) and hafnium nitride (HfN) as thermally stable Schottky contacts to develop a thermally stable, deep-ultraviolet (DUV) photodiode using a boron-doped homoepitaxial p-diamond epilayer. Thermal annealing at 500 deg. C improves the rectifying current-voltage characteristics of the photodiode, resulting in the excellent thermal stability. The discrimination ratio between DUV and visible light is measured to be as large as 106 at a reverse bias voltage as small as 2 V, and it remains almost constant after annealing at 500 deg. C for 5 h. Metal carbide and nitride contacts for diamond are thus useful for developing a thermally stable diamond DUV photodetector

  5. Magnetar Outbursts from Avalanches of Hall Waves and Crustal Failures

    CERN Document Server

    Li, Xinyu; Belovorodov, Andrei M

    2016-01-01

    We explore the interaction between Hall waves and mechanical failures inside a magnetar crust, using detailed one-dimentional models that consider temperature-sensitive plastic flow, heat transport and cooling by neutrino emission, as well as the coupling of the crustal motion to the magnetosphere. We find that the dynamics is enriched and accelerated by the fast, short-wavelength Hall waves that are emitted by each failure. The waves propagate and cause failures elsewhere, triggering avalanches. We argue that these avalanches are the likely sources of outbursts in transient magnetars.

  6. Assessing risk based on uncertain avalanche activity patterns

    Science.gov (United States)

    Zeidler, Antonia; Fromm, Reinhard

    2015-04-01

    Avalanches may affect critical infrastructure and may cause great economic losses. The planning horizon of infrastructures, e.g. hydropower generation facilities, reaches well into the future. Based on the results of previous studies on the effect of changing meteorological parameters (precipitation, temperature) and the effect on avalanche activity we assume that there will be a change of the risk pattern in future. The decision makers need to understand what the future might bring to best formulate their mitigation strategies. Therefore, we explore a commercial risk software to calculate risk for the coming years that might help in decision processes. The software @risk, is known to many larger companies, and therefore we explore its capabilities to include avalanche risk simulations in order to guarantee a comparability of different risks. In a first step, we develop a model for a hydropower generation facility that reflects the problem of changing avalanche activity patterns in future by selecting relevant input parameters and assigning likely probability distributions. The uncertain input variables include the probability of avalanches affecting an object, the vulnerability of an object, the expected costs for repairing the object and the expected cost due to interruption. The crux is to find the distribution that best represents the input variables under changing meteorological conditions. Our focus is on including the uncertain probability of avalanches based on the analysis of past avalanche data and expert knowledge. In order to explore different likely outcomes we base the analysis on three different climate scenarios (likely, worst case, baseline). For some variables, it is possible to fit a distribution to historical data, whereas in cases where the past dataset is insufficient or not available the software allows to select from over 30 different distribution types. The Monte Carlo simulation uses the probability distribution of uncertain variables

  7. Test of BESⅢ RPC in the avalanche mode

    Institute of Scientific and Technical Information of China (English)

    HAN Ji-Feng; ZHANG Jia-Wen; CHEN Jin; ZHANG Qing-Min; LIU Qian; XIE Yu-Guang; QIAN Sen; MA Lie-Hua

    2008-01-01

    The installation of the BESⅢ RPC system has been completed.Cosmic ray test results show that they perform very well in streamer mode and meet the BESⅢ requirements.We have tested several RPCs in the avalanche mode with the addition of extra SF6 in the gas mixture.We find an efficiency plateau that reaches~95%.and a time resolution of 1.8 ns.This demonstrates that the BESⅢ-type RPC can work in the avalanche mode as well.

  8. Simulacija ogroženosti površja zaradi snežnih plazov v slovenskih alpah = Simulation of avalanche threat in the Slovene Alps

    Directory of Open Access Journals (Sweden)

    Miha Pavšek

    2002-01-01

    Full Text Available According to its relief, Slovenia is highly variegated and its landscape diverse, andfor this reason it is threatened by numerous natural accidents, among which areavalanches. On the basis of previous findings and with the help of data fromSlovenia’s Geographical Information System, we undertook to determine potentialavalanche surfaces in the Slovene Alps. In so doing, we considered the results ofdata processing on avalanches in the Julian Alps from the avalanche cadastre,other similar studies, and data layers on natural and geographical elements inhigh-mountain regions. In conclusion, we compared simulated and actual potentialavalanche threat areas to assess the validity of our model.

  9. Si/Ge photodiodes for coherent and analog communication

    Science.gov (United States)

    Piels, Molly

    High-speed photodiodes have diverse applications in wireless and fiber communications. They can be used as output stages for antenna systems as well as receivers for fiber optic networks. Silicon is an attractive substrate material for photonic components for a number of reasons. Low cost manufacturing in CMOS fabrication facilities, low material loss at telecommunications wavelengths, and relatively simple co-packaging with electronics are all driving interest in silicon photonic devices. Since silicon does not absorb light at telecommunications wavelengths, photodetector fabrication requires the integration of either III-V materials or germanium. Recent work on germanium photodetectors has focused on low-capacitance devices suitable for integration with silicon electronics. These devices have excellent bandwidth and efficiency, but have not been designed for the levels of photocurrent required by coherent and analog systems. This thesis explores the design, fabrication, and measurement of photodetectors fabricated on silicon with germanium absorbing regions for high speed and high power performance. There are numerous design trade-offs between speed, efficiency, and output power. Designing for high bandwidth favors small devices for low capacitance. Small devices require abrupt absorption profiles for good efficiency, but design for high output power favors large devices with dilute absorption. The absorption profile can be controlled by the absorber layer thickness, but this will also affect the bandwidth and power handling. This work quantifies the trade-offs between high speed, high efficiency, and high power design. Intrinsic region thickness and absorption profile are identified as the most important design variables. For PIN structures, the absorption profile and intrinsic region thickness are both functions of the Ge thickness, but in uni-traveling carrier (UTC) structures the absorption profile and intrinsic region can be designed independently. This

  10. Electric field distribution and simulation of avalanche formation due to the passage of heavy ions in a parallel grid avalanche counter

    Indian Academy of Sciences (India)

    D Kanjilal; S Saha

    2009-05-01

    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 grid geometry has marginally higher gain at larger electric fields close to the avalanche region. The spatial uniformity of response in the two wire grid configurations is also compared.

  11. Avalanches in dry and saturated disordered media at fracture

    Science.gov (United States)

    Milanese, Enrico; Yılmaz, Okan; Molinari, Jean-François; Schrefler, Bernhard

    2016-04-01

    This paper analyzes fracturing in inhomogeneous media under dry and fully saturated conditions. We adopt a central force model with continuous damage to study avalanche behavior in a two-dimensional truss lattice undergoing dilation. Multiple fractures can develop at once and a power-law distribution of the avalanche size is observed. The values for the power-law exponent are compared with the ones found in the literature and scale-free behavior is suggested. The fracture evolves intermittently in time because only some avalanches correspond to fracture advancement. A fully saturated model with continuous damage based on the extended Biot's theory is developed and avalanche behavior is studied in the presence of fluid, varying the fluid boundary conditions. We show that power-law behavior is destroyed when the fluid flux governs the problem. Fluid pressure behavior during intermittent crack tip advancement is studied for the continuous-damage fully saturated model. It is found that when mechanical loading prevails, the pressure rises when the crack advances, while when fluid loading prevails, the pressure drops when the crack advances.

  12. Positron camera with high-density avalanche chambers

    International Nuclear Information System (INIS)

    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)

  13. A high current, high speed pulser using avalanche transistors

    International Nuclear Information System (INIS)

    A high current, high speed pulser for the beam pulsing of a linear accelerator is described. It uses seven avalanche transistors in cascade. Design of a trigger circuit to obtain fast rise time is discussed. The characteristics of the pulser are : (a) Rise time = 0.9 ns (FWHM) and (d) Life time asymptotically equals 2000 -- 3000 hr (at 50 Hz). (author)

  14. Catastrophic debris avalanche deposit of Socompa volcano, northern Chile

    Science.gov (United States)

    Francis, P. W.; Gardeweg, M.; Ramirez, C. F.; Rothery, D. A.

    1985-01-01

    Between 10,000 and 500 yr ago the Socompa volcano in northern Chile experienced a catastrophic collapse of a 70 deg sector of the original cone, causing a debris avalanche that descended nearly 3000 m vertically and traveled more than 35 km from the volcano. The deposits cover some 490 sq km and have a minimum volume of 15 cu km. Parts of the original cone slumped in a nearly coherent form and are now preserved as large blocks more than 400 m high. The primary avalanche traveled northwestward over sloping ground before coming to rest transiently, forming a prominent marginal ridge, and then slid away northeastward to form a secondary flow, overriding much of the primary avalanche deposit. Abundant, prismatic, jointed dacite blocks within the debris avalanche deposit and a thin, fine-grained pumiceous deposit beneath it suggest that the collapse was triggered by magmatic activity and may have been accompanied by a violent lateral blast. Collapse was followed by eruption of pumiceous pyroclastic flows and extrusion of voluminous dacite domes.

  15. Avalanches in dry and saturated disordered media at fracture.

    Science.gov (United States)

    Milanese, Enrico; Yılmaz, Okan; Molinari, Jean-François; Schrefler, Bernhard

    2016-04-01

    This paper analyzes fracturing in inhomogeneous media under dry and fully saturated conditions. We adopt a central force model with continuous damage to study avalanche behavior in a two-dimensional truss lattice undergoing dilation. Multiple fractures can develop at once and a power-law distribution of the avalanche size is observed. The values for the power-law exponent are compared with the ones found in the literature and scale-free behavior is suggested. The fracture evolves intermittently in time because only some avalanches correspond to fracture advancement. A fully saturated model with continuous damage based on the extended Biot's theory is developed and avalanche behavior is studied in the presence of fluid, varying the fluid boundary conditions. We show that power-law behavior is destroyed when the fluid flux governs the problem. Fluid pressure behavior during intermittent crack tip advancement is studied for the continuous-damage fully saturated model. It is found that when mechanical loading prevails, the pressure rises when the crack advances, while when fluid loading prevails, the pressure drops when the crack advances. PMID:27176380

  16. 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. PMID:18808393

  17. Detection of charged particles through a photodiode: design and analysis

    International Nuclear Information System (INIS)

    This project develops and construct an charge particle detector mean a pin photodiode array, design and analysis using a silicon pin Fotodiodo that generally is used to detect visible light, its good efficiency, size compact and reduced cost specifically allows to its use in the radiation monitoring and alpha particle detection. Here, so much, appears the design of the system of detection like its characterization for alpha particles where one is reported as alpha energy resolution and detection efficiency. The equipment used in the development of work consists of alpha particle a triple source composed of Am-241, Pu-239 and Cm-244 with 5,55 KBq as total activity, Maestro 32 software made by ORTEC, a multi-channel card Triumph from ORTEC and one low activity electroplated uranium sample. (Author)

  18. Innovative Detection System of Ochratoxin A by Thin Film Photodiodes

    Science.gov (United States)

    Caputo, Domenico; de Cesare, Giampiero; Fanelli, Corrado; Nascetti, Augusto; Ricelli, Alessandra; Scipinotti, Riccardo

    2007-01-01

    In this work we present, for the first time, a rapid, compact and innovative method for detection of Ochratoxin A (OTA) based on hydrogenated amorphous silicon (a-Si:H) sensors. 2 μl of acidified toluene containing OTA at different concentrations were spotted on the silica side of a High Performance Thin Layer Cromatography plate and aligned with a a-Si:H p-i-n photodiode deposited by Plasma Enhanced Chemical Vapor Deposition on a different glass substrate. As an UV radiation excites the mycotoxin, the re-emitted light is detected by the a-Si:H sensor. Results show a very good linearity between OTA concentration and the sensor photocurrent over almost three orders of magnitude. The minimum detected OTA concentration is equal to 0.1ng, showing that the presented system has the potential for a low cost system suitable for the early detection of toxins in foods.

  19. Innovative Detection System of Ochratoxin A by Thin Film Photodiodes

    Directory of Open Access Journals (Sweden)

    Riccardo Scipinotti

    2007-07-01

    Full Text Available In this work we present, for the first time, a rapid, compact and innovativemethod for detection of Ochratoxin A (OTA based on hydrogenated amorphous silicon (a-Si:H sensors. 2 μl of acidified toluene containing OTA at different concentrations werespotted on the silica side of a High Performance Thin Layer Cromatography plate andaligned with a a-Si:H p-i-n photodiode deposited by Plasma Enhanced Chemical VaporDeposition on a different glass substrate. As an UV radiation excites the mycotoxin, the re-emitted light is detected by the a-Si:H sensor. Results show a very good linearity betweenOTA concentration and the sensor photocurrent over almost three orders of magnitude. Theminimum detected OTA concentration is equal to 0.1ng, showing that the presented systemhas the potential for a low cost system suitable for the early detection of toxins in foods.

  20. Soil erosion and organic carbon export by wet snow avalanches

    Directory of Open Access Journals (Sweden)

    O. Korup

    2014-01-01

    Full Text Available Many mountain belts sustain prolonged snow cover for parts of the year, although enquiries into rates of erosion in these landscapes have focused almost exclusively on the snow-free periods. This raises the question of whether annual snow cover contributes significantly to modulating rates of erosion in high-relief terrain. In this context, the sudden release of snow avalanches is a frequent and potentially relevant process, judging from the physical damage to subalpine forest ecosystems, and the amount of debris contained in avalanche deposits. To quantitatively constrain this visual impression and to expand the sparse existing literature, we sampled sediment concentrations of n = 28 river-spanning snow-avalanche deposits (snow bridges in the eastern Swiss Alps, and infer an orders-of-magnitude variability in specific fine sediment and organic carbon yields (1.8 to 830 t km−2 yr−1, and 0.04 to 131 t C km−2 yr−1, respectively. A Monte Carlo simulation demonstrates that, with a minimum of free parameters, such variability is inherent to the geometric scaling used for computing specific yields. Moreover, the widely applied method of linearly extrapolating plot-scale sample data may be prone to substantial under- or over-estimates. A comparison of our inferred yields with previously published work demonstrates the relevance of wet snow avalanches as prominent agents of soil erosion and transporters of biogeochemical constituents to mountain rivers. Given that a number of snow bridges persisted below the insulating debris cover well into the summer months, snow-avalanche deposits also contribute to regulating in-channel sediment and organic debris storage on seasonal timescales. Finally, our results underline the potential shortcomings of neglecting erosional processes in the winter and spring months in mountainous terrain subjected to prominent snow cover.

  1. Forensic Analysis of the May 2014 West Salt Creek Rock Avalanche in Western Colorado

    Science.gov (United States)

    Coe, J. A.; Baum, R. L.; Allstadt, K.; Kochevar, B. F.; Schmitt, R. G.; Morgan, M. L.; White, J. L.; Stratton, B. T.; Hayashi, T. A.; Kean, J. W.

    2015-12-01

    The rain-on-snow induced West Salt Creek rock avalanche occurred on May 25, 2014 on the northern flank of Grand Mesa. The avalanche was rare for the contiguous U.S. because of its large size (59 M m3) and high mobility (Length/Height=7.2). 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 (UAS) imagery as a base for our field mapping and analyzed seismic data from 22 broadband stations (distances <656 km) and one short-period network. We inverted broadband data to derive a time series of forces that the avalanche exerted on the 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 a landslide/debris flow that started about 10 hours before the main avalanche. The main avalanche lasted just over 3 minutes 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, strike-slip bound core continued to move slowly. Following movement of the core, numerous shallow landslides, rock slides, and rock falls created new structures and modified topography. Mobility of the main avalanche and central core were 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 liquefied basal layer; and a thicker and stronger overriding layer.

  2. Combined detectors of charged particles based on zinc selenide scintillators and silicon photodiodes

    CERN Document Server

    Ryzhikov, V D; Starzhinskij, N G

    2001-01-01

    combined detectors of charged particles are described based on zinc selenide (Zn Se(Te)) crystals,silicon photodiodes and charges-sensitive amplifiers. Zn Se(Te) scintillators are characterized by high alpha to beta ratio (approx 1.0), good scintillation efficiency (up to 22%),and high radiation stability (up to 100 Mrad),together with good spectral matching with silicon PIN photodiodes. The signal coming from the photodiode in the two modes (photoreceiver and semiconductor detector) differ in the amplitude values and pulse duration, which opens new possibilities for development and application of such combined detectors.

  3. 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.

  4. El reconocimiento de avalanchas de rocas y deslizamientos de bloques rocosos prehistoricos en el área andina de Neuquén (37°15´ - 37°30´S Reconnaissance of prehistoric rock-avalanches and rock blocks slides in the Andean area of Neuquén (37°15´- 37°30´S

    Directory of Open Access Journals (Sweden)

    E.F. González Díaz

    2005-09-01

    pendientes, proceso que se interpreta promovido por un inductor sísmico, el que mostraría una relación adecuada con el marco sismotectónico y estructural de la región. Se destaca la influencia que pudo alcanzar la disposición periclinal de las acumulaciones volcánicas en el desprendimiento del flanco de una depresión caldérica. La consiguiente ameliorización climática postglaciaria, caracterizada por mayor humedad y precipitaciones, contribuyó a una disminución de la fricción y cohesión de los componentes de las pendientes. La edad de estos fenómenos no ha sido determinada, pero se la considerara posterior al englazamiento local cuaternario.Five prehistoric rock-avalanches are described in the northern cordilleran region of Neuquén Province, between 37º15' and 37º30'S and between 70º55' and 71º05'W. These slides and their deposits were not previously identified and moreover they were classified as glacial and glaciofluvial in origin. All of them are developed on volcanic-sedimentary deposits. They are named after local places: Cerro Piche Moncol, Cerro Guañaco, Cerro Coronal, Laguna Negra and Laguna Lauquen Mallín avalanches. The first three form a group of avalanches situated north of Reñileuvú creek, in the vicinity of the previously described Moncol rockavalanche. Their break-away zones are located on the lateral slopes of a pre-existing deep glacial valley. The biggest rock-avalanche is the Cerro Piche Moncol and its deposits are due to the collapse of the southern flank of a volcanic edifice with a small caldera. The Cerro Guañaco, Cerro Coronal and Laguna Negra rock-avalanches began as a slump slide to evolving distally into a flow. The slides of Laguna Lauquen Mallín are big rock-block slides. Some local factors, principally contrasting lithology and physical properties, structural factors and more humid conditions during postglacial times favourable conditions for the loss of slope equilibrium. The authors suggest that these gravitational

  5. A view on progress of silicon single-photon avalanche diodes and quenching circuits

    Science.gov (United States)

    Cova, Sergio; Ghioni, Massimo; Zappa, Franco; Rech, Ivan; Gulinatti, Angelo

    2006-10-01

    Silicon Single-Photon Avalanche-Diodes (SPAD) are nowadays considered a solid-state alternative to Photomultiplier Tubes (PMT) in single photon counting (SPC) and time-correlated single photon-counting (TCSPC) over the visible spectral range up to 1 micron wavelength. SPADs implemented in planar epitaxial technology compatible with CMOS circuits offer the typical advantages of microelectronic devices (small size, ruggedness, low voltage and low power, etc.). Furthermore, they have inherently higher photon detection efficiency, since they do not rely on electron emission in vacuum from a photocathode as PMT, but instead on the internal photoelectric effect. However, PMTs offer much wider sensitive area, which greatly simplifies the design of optical systems; they provide position-sensitive photon detection and imaging capability; they attain remarkable performance at high counting rate and offer picosecond timing resolution with Micro-Channel Plate (MCP) models. In order to make SPADs more competitive in a broader range of SPC and TCPC applications it is necessary to face both semiconductor technology issues and circuit design issues, which will be here dealt with. Technology issues will be discussed in the context of two possible approaches: employing a standard industrial high-voltage compatible CMOS technology or developing a dedicated CMOS-compatible technology. Circuit design issues will be discussed taking into account problems arising from conflicting requirements set by various required features, such as fast and efficient avalanche quenching and reset, high resolution photon timing, etc.

  6. The parallel plate avalanche counter: a simple, rugged, imaging X-ray counter

    International Nuclear Information System (INIS)

    A two-dimensional parallel gap proportional counter has been developed at the Danish Space Research Institute. Imaging over the 120 mm diameter active area is obtained using the positive ion component of the avalanche signals as recorded by a system of wedge- and strip-electrodes. An electronically simple, but very effective background rejection is obtained by using the fast electron component of the avalanche signal. Gas gains up to 8x105 have been achieved. An energy-resolution of 16% and a sub-millimeter spatial resolution have been measured at 5.9 keV for an operating gas gain of 105. In principle, the position coordinates are linear functions of electronic readouts. The present model, however, exhibits non-linearities, caused by imperfections in the wedge and strip-electrode pattern. These non-linearities are corrected by using a bilinear correction algorithm. We conclude that the rugged construction, the simple electronics, the effectiveness of the background rejection and the actual imaging performance makes this a very attractive laboratory detector for low and intermediate count rate imaging applications. ((orig.))

  7. High performance x-ray imaging detectors on foil using solution-processed organic photodiodes with extremely low dark leakage current (Presentation Recording)

    Science.gov (United States)

    Kumar, Abhishek; Moet, Date; van der Steen, Jan Laurens; van Breemen, Albert; Shanmugam, Santhosh; Gilot, Jan; Andriessen, Ronn; Simon, Matthias; Ruetten, Walter; Douglas, Alexander; Raaijmakers, Rob; Malinowski, Pawel E.; Myny, Kris; Gelinck, Gerwin

    2015-10-01

    High performance X-ray imaging detectors on foil using solution-processed organic photodiodes with extremely low dark leakage current Abhishek Kumara, Date Moeta, Albert van Breemena, Santhosh Shanmugama, Jan-Laurens van der Steena, Jan Gilota, Ronn Andriessena, Matthias Simonb, Walter Ruettenb, Alexander U. Douglasb, Rob Raaijmakersc, Pawel E. Malinowskid, Kris Mynyd and Gerwin H. Gelincka,e a. Holst Centre/TNO, High Tech Campus 31, Eindhoven 5656 AE, The Netherlands b. Philips Research, High Tech Campus 34, 5656 AE Eindhoven, The Netherlands c. Philips Healthcare, Veenpluis 6-8, 5684 PC Best, The Netherlands d. Department of Large Area Electronics, imec vzw, Kapeldreef 75, Leuven B3001, Belgium e. Applied Physics Department, TU Eindhoven, Eindhoven, The Netherlands We demonstrate high performance X-ray imaging detectors on foil suitable for medical grade X-ray imaging applications. The detectors are based on solution-processed organic photodiodes forming bulk-heterojunctions from photovoltaic donor and acceptor blend. The organic photodiodes are deposited using an industrially compatible slot die coating technique with end of line processing temperature below 100°C. These photodiodes have extremely low dark leakage current density of 10-7 mA/cm2 at -2V bias with very high yield and have peak absorption around 550 nm wavelength. We combine these organic photodiodes with high mobility metal oxide semiconductor based thin film transistor arrays with high pixel resolution of 200ppi on thin plastic substrate. When combined with a typical CsI(TI) scintillator material on top, they are well suited for low dose X-ray imaging applications. The optical crosstalk is insignificant upto resolution of 200 ppi despite the fact that the photodiode layer is one continuous layer and is non-pixelated. Low processing temperatures are another key advantage since they can be fabricated on plastic substrate. This implies that we can make X-ray detectors on flexible foil. Those

  8. 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.

  9. Characterization of a Photodiode Coupled with a Si Nanowire-FET on a Plastic Substrate

    Directory of Open Access Journals (Sweden)

    Kiyeol Kwak

    2010-10-01

    Full Text Available In this study, a laterally coupled device composed of a photodiode and a Si nanowires-field-effect transistor (NWs-FET is constructed on a plastic substrate and the coupled device is characterized. The photodiode is made of p-type Si NWs and an n-type ZnO film. The Si NWs-FET is connected electrically to the photodiode in order to enhance the latter’s photocurrent efficiency by adjusting the gate voltage of the FET. When the FET is switched on by biasing a gate voltage of −9 V, the photocurrent efficiency of the photodiode is three times higher than that when the FET is switched off by biasing a gate voltage of 0 V.

  10. InGaAs p-i-n Photodiodes for Microwave Applications

    OpenAIRE

    Malyshev, Sergei; Chizh, A.; Andrievski, Vatslav

    2004-01-01

    The experimental and theoretical study of the surface-illuminated InGaAs p-i-n photodiodes for such microwave applications as photonic microwave generation, optical control of microwave circuits and optoelectronic mixing is presented.

  11. AN INVESTIGATION ON PHOTODIODE SWITCHING TIMES FOR PULSED HIGH RADIANT POWERS

    Directory of Open Access Journals (Sweden)

    Erdem ÖZÜTÜRK

    2004-02-01

    Full Text Available In many applications the light impinging on photodiode surface is pulsed. The change in parameter values in the equivalent circuit of photodiode is important if the amplitude of light pulses are large. In this situation, the change of parameter values with the amplitude of light pulse is nonlinear. Because of this, the nonlinear model of photodiode has been used in this search. By the reasons of photoconductive operation mode is a fast operation, the photoconductive circuit has been examined. In this study, according to the nonlinear behavior of photodiode at pulsed high radiant powers the changes of switching times have been investigated by using SPICE program and the changing of switching times with increasing radiant power has been showed.

  12. Characterization of Power-to-Phase Conversion in High-Speed P-I-N Photodiodes

    CERN Document Server

    Taylor, J; Hati, A; Nelson, C; Quinlan, F; Joshi, A; Diddams, S

    2011-01-01

    Fluctuations of the optical power incident on a photodiode can be converted into phase fluctuations of the resulting electronic signal due to nonlinear saturation in the semiconductor. This impacts overall timing stability (phase noise) of microwave signals generated from a photodetected optical pulse train. In this paper, we describe and utilize techniques to characterize this conversion of amplitude noise to phase noise for several high-speed (>10 GHz) InGaAs P-I-N photodiodes operated at 900 nm. We focus on the impact of this effect on the photonic generation of low phase noise 10 GHz microwave signals and show that a combination of low laser amplitude noise, appropriate photodiode design, and optimum average photocurrent is required to achieve phase noise at or below -100 dBc/Hz at 1 Hz offset a 10 GHz carrier. In some photodiodes we find specific photocurrents where the power-to-phase conversion factor is observed to go to zero.

  13. Rad Tolerant CMOS Image Sensor Based on Hole Collection 4T Pixel Pinned Photodiode

    OpenAIRE

    Place, Sébastien; Carrere, Jean-Pierre; Allegret, Stephane; Magnan, Pierre; Goiffon, Vincent; Roy, François

    2012-01-01

    1.4μm pixel pitch CMOS Image sensors based on hole collection pinned photodiode (HPD) have been irradiated with 60Co source. The HPD sensors exhibit much lower dark current degradation than equivalent commercial sensors using an Electron collection Pinned Photodiode (EPD). This hardness improvement is mainly attributed to carrier accumulation near the interfaces induced by the generated positive charges in dielectrics. The pre-eminence of this image sensor based on hole collection pinned phot...

  14. Soft X-ray detection and photon counting spectroscopy with commercial 4H-SiC Schottky photodiodes

    Science.gov (United States)

    Zhao, S.; Gohil, T.; Lioliou, G.; Barnett, A. M.

    2016-09-01

    The results of electrical characterisation and X-ray detection measurements of two different active area (0.06 mm2 and 0.5 mm2) commercial 4H-SiC Schottky photodiodes at room temperature are reported. The devices exhibited low dark currents (less than 10 pA) even at a high electric field strengths (403 kV/cm for 0.06 mm2 diodes; 227 kV/cm for 0.5 mm2 diodes). The results of the X-ray measurements indicate that the diodes can be used as photon counting spectroscopic X-ray detectors with modest energy resolutions: FWHM at 5.9 keV of 1.8 keV and 3.3 keV, for the 0.06 mm2 and 0.5 mm2 devices, respectively. Noise analysis of the photodiodes coupled to a custom low noise charge sensitive preamplifier is also presented.

  15. Plasma simulation of electron avalanche in a linear thyratron

    International Nuclear Information System (INIS)

    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

  16. A compact gas-filled avalanche counter for DANCE

    Science.gov (United States)

    Wu, C. Y.; Chyzh, A.; Kwan, E.; Henderson, R. A.; Gostic, J. M.; Carter, D.; Bredeweg, T. A.; Couture, A.; Jandel, M.; Ullmann, J. L.

    2012-12-01

    A compact gas-filled avalanche counter for the detection of fission fragments was developed for a highly segmented 4π γ-ray calorimeter, namely the Detector for Advanced Neutron Capture Experiments located at the Lujan Center of the Los Alamos Neutron Science Center. It has been used successfully for experiments with 235U, 238Pu, 239Pu, and 241Pu isotopes to provide a unique signature to differentiate the fission from the competing neutron-capture reaction channel. It was also used to study the spontaneous fission in 252Cf. The design and performance of this avalanche counter for targets with extreme α-decay rate up to ˜2.4×108/s are described.

  17. A compact gas-filled avalanche counter for DANCE

    Energy Technology Data Exchange (ETDEWEB)

    Wu, C.Y., E-mail: wu24@llnl.gov [Lawrence Livermore National Laboratory, Livermore, CA 94551 (United States); Chyzh, A.; Kwan, E.; Henderson, R.A.; Gostic, J.M.; Carter, D. [Lawrence Livermore National Laboratory, Livermore, CA 94551 (United States); Bredeweg, T.A.; Couture, A.; Jandel, M.; Ullmann, J.L. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

    2012-12-01

    A compact gas-filled avalanche counter for the detection of fission fragments was developed for a highly segmented 4{pi} {gamma}-ray calorimeter, namely the Detector for Advanced Neutron Capture Experiments located at the Lujan Center of the Los Alamos Neutron Science Center. It has been used successfully for experiments with {sup 235}U, {sup 238}Pu, {sup 239}Pu, and {sup 241}Pu isotopes to provide a unique signature to differentiate the fission from the competing neutron-capture reaction channel. It was also used to study the spontaneous fission in {sup 252}Cf. The design and performance of this avalanche counter for targets with extreme {alpha}-decay rate up to {approx}2.4 Multiplication-Sign 10{sup 8}/s are described.

  18. Avalanche effect and gain saturation in high harmonic generation

    CERN Document Server

    Serrat, Carles; Budesca, Josep M; Seres, Jozsef; Seres, Enikoe; Aurand, Bastian; Hoffmann, Andreas; Namba, Shinichi; Kuehl, Thomas; Spielmann, Christian

    2015-01-01

    Optical amplifiers in all ranges of the electromagnetic spectrum exhibit two essential characteristics: i) the input signal during the propagation in the medium is multiplied by the avalanche effect of the stimulated emission to produce exponential growth and ii) the amplification saturates at increasing input signal. We demonstrate that the strong-field theory in the frame of high harmonic generation fully supports the appearance of both the avalanche and saturation effects in the amplification of extreme ultraviolet attosecond pulse trains. We confirm that the amplification takes place only if the seed pulses are perfectly synchronized with the driving strong field in the amplifier. We performed an experimental study and subsequent model calculation on He gas driven by intense 30-fs-long laser pulses, which was seeded with an attosecond pulse train at 110 eV generated in a separated Ne gas jet. The comparison of the performed calculations with the measurements clearly demonstrates that the pumped He gas med...

  19. A compact gas-filled avalanche counter for DANCE

    International Nuclear Information System (INIS)

    A compact gas-filled avalanche counter for the detection of fission fragments was developed for a highly segmented 4π γ-ray calorimeter, namely the Detector for Advanced Neutron Capture Experiments located at the Lujan Center of the Los Alamos Neutron Science Center. It has been used successfully for experiments with 235U, 238Pu, 239Pu, and 241Pu isotopes to provide a unique signature to differentiate the fission from the competing neutron-capture reaction channel. It was also used to study the spontaneous fission in 252Cf. The design and performance of this avalanche counter for targets with extreme α-decay rate up to ∼2.4×108/s are described.

  20. Stability of the discretization of the electron avalanche phenomenon

    International Nuclear Information System (INIS)

    The numerical simulation of the discharge inception is an active field of applied physics with many industrial applications. In this work we focus on the drift-reaction equation that describes the electron avalanche. This phenomenon is one of the basic building blocks of the streamer model. The main difficulty of the electron avalanche equation lies in the fact that the reaction term is positive when a high electric field is applied. It leads to exponentially growing solutions and this has a major impact on the behavior of numerical schemes. We analyze the stability of a reference finite volume scheme applied to this latter problem. The stability of the method may impose a strict mesh spacing, therefore a proper stabilized scheme, which is stable whatever spacing is used, has been developed. The convergence of the scheme is treated as well as some numerical experiments

  1. Stability of the discretization of the electron avalanche phenomenon

    Energy Technology Data Exchange (ETDEWEB)

    Villa, Andrea, E-mail: andrea.villa@rse-web.it [Ricerca Sul Sistema Energetico (RSE), Via Rubattino 50, 20134, Milano (Italy); Barbieri, Luca, E-mail: luca.barbieri@rse-web.it [Ricerca Sul Sistema Energetico (RSE), Via Rubattino 50, 20134, Milano (Italy); Gondola, Marco, E-mail: marco.gondola@rse-web.it [Ricerca Sul Sistema Energetico (RSE), Via Rubattino 50, 20134, Milano (Italy); Leon-Garzon, Andres R., E-mail: andresricardo.leon@polimi.it [CMIC Department “Giulio Natta”, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133, Milano (Italy); Malgesini, Roberto, E-mail: roberto.malgesini@rse-web.it [Ricerca Sul Sistema Energetico (RSE), Via Rubattino 50, 20134, Milano (Italy)

    2015-09-01

    The numerical simulation of the discharge inception is an active field of applied physics with many industrial applications. In this work we focus on the drift-reaction equation that describes the electron avalanche. This phenomenon is one of the basic building blocks of the streamer model. The main difficulty of the electron avalanche equation lies in the fact that the reaction term is positive when a high electric field is applied. It leads to exponentially growing solutions and this has a major impact on the behavior of numerical schemes. We analyze the stability of a reference finite volume scheme applied to this latter problem. The stability of the method may impose a strict mesh spacing, therefore a proper stabilized scheme, which is stable whatever spacing is used, has been developed. The convergence of the scheme is treated as well as some numerical experiments.

  2. Design of HgCdTe heterojunction photodiodes on Si substrate

    Science.gov (United States)

    Zhang, P.; Ye, Z. H.; Chen, Y. Y.; Lin, C.; Hu, X. N.; Ding, R. J.; He, L.

    2014-05-01

    An innovative heterojunction photodiode structure in HgCdTe-on-Si long-wavelength (LW) infrared focal plane array (IRFPA) detector is investigated in this paper. The quantum efficiency and the photoresponse of devices have been numerically simulated, using Crosslight Technology Computer Aided Design (TCAD) software. Simulation results indicate that in contrast to the p+-on-n homojunction photodiode, the heterojunction photodiode effectively suppresses the crosstalk between adjacent pixels and interface recombination between HgCdTe active region and buffer layer on Si substrate. And in the range of the LW-band, the quantum efficiency of the heterojunction photodiode increases by 35.5%. Furthermore, the heterojunction photodiode acquires the narrow-band response spectrum desired in the application of the LW IRFPA detectors as the p+-on-n homojunction photodiode with the optical filter. Finally, the smaller bulk resistance of its heavily doped N-type layer ensures the uniformity of the pixel series resistance in the large format IRFPAs.

  3. Avalanche multiplication of electrons and holes in cadmium telluride

    CERN Document Server

    Demich, N V

    2001-01-01

    Determination of the ratio of the coefficients of the electrons and holes of the diode structures impact ionization is carried out with the purpose of optimizing the parameters of the avalanche diodes from the cadmium telluride. It is shown experimentally, that the process of the impact ionization in the cadmium telluride is stimulated by holes. The ratio of the coefficients of the holes and electrons impact ionization constitutes approx = 30-40

  4. Sixteen-year follow-up of childhood avalanche survivors

    Science.gov (United States)

    Thordardottir, Edda Bjork; Valdimarsdottir, Unnur Anna; Hansdottir, Ingunn; Hauksdóttir, Arna; Dyregrov, Atle; Shipherd, Jillian C.; Elklit, Ask; Resnick, Heidi; Gudmundsdottir, Berglind

    2016-01-01

    Background Every year a substantial number of children are affected by natural disasters worldwide. However, data are scarce on long-term psychological impact of natural disasters on children's health. Identifying risk factors and outcomes associated with the long-term sequelae of posttraumatic stress disorder (PTSD) can provide a gateway to recovery as well as enhancement of preventive measures. Objective Among childhood avalanche survivors, we aimed to investigate risk factors for PTSD symptoms and the relationship between socioeconomic status (SES) and PTSD symptoms in adulthood. Methods Childhood survivors (aged 2–19 at the time of exposure) of two avalanches were identified through nationwide registers 16 years later. The Posttraumatic Diagnostic Scale was used to assess current PTSD symptoms. One-way ANOVA was used to explore PTSD symptoms by background and trauma-specific factors, as well as associations with current SES. Predictors of PTSD symptoms were examined by multivariable regression analysis. Results Response rate was 66% (108/163). Results from univariate ANOVA analysis revealed that female sex was associated with PTSD symptoms (F=5.96, punemployment and/or disability (F=3.04, p<0.05). In a multivariable regression model, when adjusting for age and sex, lack of social support (t=4.22, p<0.001) and traumatic reactions of caregivers (t=2.49, p<0.05) in the aftermath of the disaster independently predicted PTSD 16 years post-trauma. Conclusions Lingering PTSD symptoms after childhood exposure to a disaster may negatively influence socioeconomic development in adulthood. Strengthening children's support systems post-disaster may prevent the long-term sequelae of symptoms. Highlights of the article PTSD symptoms following avalanche exposure during childhood were associated with poorer socioeconomic status in adulthood. Lack of social support and traumatic reactions of caregivers in the aftermath of avalanches predicted PTSD symptoms among childhood

  5. Azimuthal spread of the avalanche in proportional chambers

    International Nuclear Information System (INIS)

    The angular distribution of the avalanche around the anode wire in the gas proportional counter is determined by measuring the distribution of positive ions arriving on cathode strips surrounding the anode wire for each single event. The shape and width of the distribution depend on such factors as the gas gain, the anode diameter, the counting gas and the primary ionization density. Effects of these factors are studied systematically, and their importance for practical counter applications is discussed

  6. First Townsend coefficient of organic vapour in avalanche counters

    International Nuclear Information System (INIS)

    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.)

  7. Local to global avalanches in sheared granular materials

    Science.gov (United States)

    Weng, Dengming; Wang, Dong; Bertrand, Thibault; Bares, Jonathan; Berhinger, Bob

    2015-11-01

    Commonly, granular materials yield or flow if sufficiently large shear stress is applied, leading to avalanche-like behavior. Rearrangement phenomenon can produce dramatic events like snow avalanches, land-slides or earthquakes. For experimentally sheared media, we seek to understand the dynamics of the grain rearrangements from the local to the global scale. In this work, force networks and displacement fields are measured on two-dimensional sheared material for cyclically sheared photoelastic circular particles. Avalanches, their size, location and duration are extracted at the global scale from the rapid variation of the macroscopic energy stored in the system whereas at the local scale they are measured from the energy drop, displacement and rotation of each particle. Statistics of those different quantities are computed and correlated to test their intrinsic entanglement and analyze their universal dynamics. These results are quantitatively different from what has been observed for different analytic coarse-grained approaches and permit a clear measurement of the effect of the packing fraction and inter-particle friction coefficient on the statistical behavior.

  8. 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.

  9. Measurement of Radiation - Light Field Congruence using a Photodiode Array

    Science.gov (United States)

    Balderson, Michael J.

    Improved treatment techniques in radiation therapy provide incentive to reduce treatment margins, thereby increasing the necessity for more accurate geometrical setup of the linear accelerator and accompanying components. In this thesis, we describe the development of a novel device that enables precise and automated measurement of radiation-light field congruence of medical linear accelerators for the purpose of improving setup accuracy, and standardizing repeated quality control activities. The device consists of a silicon photodiode array, an evaluation board, a data acquisition card, and a laptop. Using the device, we show that the radiation-light field congruence for both 6 and 15 MV beams is within 2 mm on a Varian Clinac 21 EX medical linear accelerator. Because measurements are automated, ambiguities resulting from observer variability are removed, greatly improving the reproducibility of measurements over time and across observers. We expect the device to be useful in providing consistent measurements on linear accelerators used for stereotactic radiosurgery, during the commissioning of new linear accelerators, and as an alternative to film or other commercially available devices for performing monthly or annual quality control checks.

  10. High Response in a Tellurium-Supersaturated Silicon Photodiode

    Science.gov (United States)

    Wang, Xi-Yuan; Huang, Yong-Guang; Liu, De-Wei; Zhu, Xiao-Ning; Zhu, Hong-Liang

    2013-03-01

    Single crystalline silicon supersaturated with tellurium are formed by ion implantation followed by excimer nanosecond pulsed laser melting (PLM). The lattice damaged by ion implantation is restored during the PLM process, and dopants are effectively activated. The hyperdoped layer exhibits high and broad optical absorption from 400 to 2500nm. The n+ p photodiodes fabricated from these materials show high response (6.9A/W at 1000nm) with reverse bias 12 V at room temperature. The corresponding cut-off wavelength is 1258nm. The amount of gain and extended cut-off wavelength both increase with increasing reverse bias voltage; above 100% external quantum efficiency is observed even at a reverse bias of 1 V. The cut-off wavelength with 0 V bias is shorter than the commercial silicon detector. This implies that the Burstein-Moss shift is due to hyperdoping. The amount of the extended cut-off wavelength increases with increasing reverse bias voltage, suggesting existence of the Franz—Keldysh effect.

  11. Continuous Holdup Measurements with Silicon P-I-N Photodiodes

    Energy Technology Data Exchange (ETDEWEB)

    Bell, Z.W.; Oberer, R.B.; Williams, J.A.; Smith, D.E.; Paulus, M.J.

    2002-05-01

    We report on the behavior of silicon P-I-N photodiodes used to perform holdup measurements on plumbing. These detectors differ from traditional scintillation detectors in that no high-voltage is required, no scintillator is used (gamma and X rays are converted directly by the diode), and they are considerably more compact. Although the small size of the diodes means they are not nearly as efficient as scintillation detectors, the diodes' size does mean that a detector module, including one or more diodes, pulse shaping electronics, analog-to-digital converter, embedded microprocessor, and digital interface can be realized in a package (excluding shielding) the size of a pocket calculator. This small size, coupled with only low-voltage power requirement, completely solid-state realization, and internal control functions allows these detectors to be strategically deployed on a permanent basis, thereby reducing or eliminating the need for manual holdup measurements. In this paper, we report on the measurement of gamma and X rays from {sup 235}U and {sup 238}U contained in steel pipe. We describe the features of the spectra, the electronics of the device and show how a network of them may be used to improve estimates of inventory in holdup.

  12. Avalanche dynamics in Bak-Sneppen evolution model observed with standard distribution width of fitness

    OpenAIRE

    Lee, Chaohong; Zhu, Xiwen; Gao, Kelin

    2001-01-01

    We introduce the standard distribution width of fitness to characterize the global and individual features of a ecosystem in the Bak-Sneppen evolution model. Through tracking this quantity in evolution, a different hierarchy of avalanche dynamics, $w_{0}$ avalanche is observed. The corresponding gap equation and the self-organized threshold $w_{c}$ are obtained. The critical exponents $\\tau ,$ $\\gamma $and $\\rho $, which describe the behavior of the avalanche size distribution, the average av...

  13. Estimating the avalanche contribution to the mass balance of debris covered glaciers

    OpenAIRE

    Banerjee, A.; Shankar, R.

    2014-01-01

    Avalanche from high head walls dominates the net accumulation in many debris covered glaciers in the Himalaya. These avalanche contributions are difficult to directly measure and may cause a systematic bias in glaciological mass balance measurements. In this paper we develop a method to estimate the avalanche contribution using available data, within the context of an idealised flowline model of the glacier. We focus on Hamtah glacier in Western Himalaya ...

  14. Determination of snow avalanche return periods using a tree-ring based reconstruction in the French Alps: cross validation with the predictions of a statistical-dynamical model

    Science.gov (United States)

    Schläppy, Romain; Eckert, Nicolas; Jomelli, Vincent; Grancher, Delphine; Brunstein, Daniel; Stoffel, Markus; Naaim, Mohamed

    2013-04-01

    Documenting past avalanche activity represents an indispensable step in avalanche hazard assessment. Nevertheless, (i) archival records of past avalanche events do not normally yield data with satisfying spatial and temporal resolution and (ii) precision concerning runout distance is generally poorly defined. In addition, historic documentation is most often (iii) biased toward events that caused damage to structure or loss of life on the one hand and (iv) undersampled in unpopulated areas on the other hand. On forested paths dendrogeomorphology has been demonstrated to represent a powerful tool to reconstruct past activity of avalanches with annual resolution and for periods covering the past decades to centuries. This method is based on the fact that living trees may be affected by snow avalanches during their flow and deposition phases. Affected trees will react upon these disturbances with a certain growth response. An analysis of the responses recorded in tree rings coupled with an evaluation of the position of reacting trees within the path allows the dendrogeomorphic expert to identify past snow avalanche events and deduced their minimum runout distance. The objective of the work presented here is firstly to dendrochronogically -reconstruct snow avalanche activity in the Château Jouan path located near Montgenèvre in the French Alps. Minimal runout distances are then determined for each reconstructed event by considering the point of further reach along the topographic profile. Related empirical return intervals are evaluated, combining the extent of each event with the average local frequency of the dendrological record. In a second step, the runout distance distribution derived from dendrochronological reconstruction is compared to the one derived from historical archives and to high return period avalanches predicted by an up-to-date locally calibrated statistical-numerical model. It appears that dendrochronological reconstructions correspond mostly to

  15. Non-invasive assessment of animal exercise stress: real-time PCR of GLUT4, COX2, SOD1 and HSP70 in avalanche military dog saliva.

    Science.gov (United States)

    Diverio, S; Guelfi, G; Barbato, O; Di Mari, W; Egidi, M G; Santoro, M M

    2015-01-01

    Exercise has been shown to increase mRNA expression of a growing number of genes. The aim of this study was to assess if mRNA expression of the metabolism- and oxidative stress-related genes GLUT4 (glucose transporter 4), COX2 (cyclooxygenase 2), SOD1 (superoxide dismutase 1) and HSP70 (heat shock protein 70) in saliva changes following acute exercise stress in dogs. For this purpose, 12 avalanche dogs of the Italian Military Force Guardia di Finanza were monitored during simulation of a search for a buried person in an artificial avalanche area. Rectal temperature (RT) and saliva samples were collected the day before the trial (T0), immediately after the descent from a helicopter at the onset of a simulated avalanche search and rescue operation (T1), after the discovery of the buried person (T2) and 2 h later (T3). Expressions of GLUT4, SOD1, COX2 and HSP70 were measured by real-time PCR. The simulated avalanche search and rescue operation was shown to exert a significant effect on RT, as well as on the expression of all metabolism- and oxidative stress-related genes investigated, which peaked at T2. The observed expression patterns indicate an acute exercise stress-induced upregulation, as confirmed by the reductions in expression at T3. Moreover, our findings indicate that saliva is useful for assessing metabolism- and oxidative stress-related genes without the need for restraint, which could affect working dog performance. PMID:25245143

  16. 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.

  17. Highly efficient avalanche multiphoton luminescence from coupled Au nanowires in the visible region

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    We report highly efficient avalanche multiphoton luminescence(MPL)from ordered-arrayed gold nanowires(NWs).The time-average excitation intensity I_(exc) is as low as 5.0-9.1 kW/cm~2.The intensity of avalanche MPL I_(MPL) is about 10~4 times larger than that of three-photon luminescence,the slope ■logI_(MPL)/■logI_(exc) of avalanche MPL reaches as high as 18.3 and the corresponding polarization dependence of I_(MPL) has a form of cos~(50)■_p.The emission dynamics of avalanche MPL and three-photon luminesc...

  18. Ultra-low Noise, High Bandwidth, 1550nm HgCdTe APD Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Voxtel Inc. proposes to optimize the design of a large area, 1.55?m sensitive HgCdTe avalanche photodiode (APD) that achieves high gain with nearly no excess noise....

  19. Low-Noise Analog APDs with Impact Ionization Engineering and Negative Feedback Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Future NASA LIDAR missions require low noise and large area photodetectors operated at short-wave infrared (SWIR) wavelengths. Silicon avalanche photodiodes have...

  20. Turn-key Near-Infrared Photon-Counting Detector Module for LIDAR Applications Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to design and deliver a turn-key photon counting detector module for near-infrared wavelengths, based on large-area InGaAs/InP avalanche photodiodes...

  1. Photodiode read-out of the ALICE photon spectrometer $PbWO_{4}$ crystals

    CERN Document Server

    Man'ko, V I; Sibiryak, Yu; Volkov, M; Klovning, A; Maeland, O A; Odland, O H; Rongved, R; Skaali, B

    1999-01-01

    Proposal of abstract for LEB99, Snowmass, Colorado, 20-24 September 1999The PHOton Spectrometer of the ALICE experiment is an electromagnetic calorimeter of high granularity consisting of 17280 lead-tungstate (PWO) crystals of dimensions 22x22x180 mm3, read out by large-area PIN-diodes with very low-noise front-end electronics. The crystal assembly is operated at -25C to increase the PWO light yield. A 16.1x17.1 mm2 photodiode, optimized for the PWO emissio spectrum at 400-500 nm, has been developed. The 20x20 mm2 preamplifier PCB is attached to the back side of the diode ceramic frame. The charge sensitive preamplifier is built in discrete logic with two input JFETs for optimum matching with the ~150pF PIN-diode. A prototype shaper has been designed and built in discrete logic. For a detector matrix of 64 units the measured ENCs are between 450-550e at -25C. Beam tests demonstrate that the required energy resolution is reached.Summary:The PHOton Spectrometer of the ALICE experiment is an electromagnetic calo...

  2. Organic Photodiodes: The Future of Full Color Detection and Image Sensing.

    Science.gov (United States)

    Jansen-van Vuuren, Ross D; Armin, Ardalan; Pandey, Ajay K; Burn, Paul L; Meredith, Paul

    2016-06-01

    Major growth in the image sensor market is largely as a result of the expansion of digital imaging into cameras, whether stand-alone or integrated within smart cellular phones or automotive vehicles. Applications in biomedicine, education, environmental monitoring, optical communications, pharmaceutics and machine vision are also driving the development of imaging technologies. Organic photodiodes (OPDs) are now being investigated for existing imaging technologies, as their properties make them interesting candidates for these applications. OPDs offer cheaper processing methods, devices that are light, flexible and compatible with large (or small) areas, and the ability to tune the photophysical and optoelectronic properties - both at a material and device level. Although the concept of OPDs has been around for some time, it is only relatively recently that significant progress has been made, with their performance now reaching the point that they are beginning to rival their inorganic counterparts in a number of performance criteria including the linear dynamic range, detectivity, and color selectivity. This review covers the progress made in the OPD field, describing their development as well as the challenges and opportunities. PMID:27111541

  3. r.avaflow, the GIS simulation model for avalanche and debris flows: new developments and challenges

    Science.gov (United States)

    Mergili, Martin; Queiroz de Oliveira, Gustavo; Fischer, Jan-Thomas; Krenn, Julia; Kulisch, Helmut; Malcherek, Andreas; Pudasaini, Shiva P.

    2016-04-01

    We present the latest developments and discuss some of the key challenges with regard to the novel and unified computational tool r.avaflow, representing an advanced, comprehensive, GIS-based open source simulation environment for two-phase geophysical mass flows such as avalanches of snow or rock, flows of debris or mud, and related process chains. r.avaflow is freely available and adoptable as a raster module of the GRASS GIS software (http://www.avaflow.org). We focus on the following issues: (1) We back-calculate a laboratory-scale debris flow experiment with r.avaflow and thereby show that different types of drag may govern the evolving flow dynamics, depending on the initial flow configuratiuon. In particular, it appears necessary to consider viscous ambient drag in order to achieve simulation results in line with experimentally measurements. (2) We employ a set of well-documented rock avalanche events to illustrate the use of a built-in functionality for parameter sensitivity analysis and optimization. To do so, we demonstrate possible strategies going beyond the deficient one-at-a-time simulation approach. They allow us to test three or more parameters at once with a limited number of model runs. Computational times are kept at an acceptable level by multi-core processing strategies and use of the Vienna Scientific Cluster. We further discuss a number of key issues with regard to (i) arbitrary mountain topography; and (ii) entrainment and deposition of material. Most tests indicate a good model performance when the affected areas predicted for a late stage of the flow simulation are compared with observed affected areas. However, we note that such a validation is not fully justified without the implementation of a physically correct model for the deposition process. Acknowledgement: The work was conducted as part of the international cooperation project "A GIS simulation model for avalanche and debris flows (avaflow)" supported by the Austrian Science Fund

  4. Wavelength-band-tuning photodiodes by using various metallic nanoparticles.

    Science.gov (United States)

    Hwang, J D; Chan, Y D; Chou, T C

    2015-11-20

    Wavelength-band tuning was easily achieved in this work by depositing various metallic nanoparticles (NPs) on silicon p-n junction photodiodes (PDs). The normalization spectrum of the PDs deposited with gold (Au) NPs reveals a high-wavelength pass characteristic; the PDs with silver (Ag) NPs coating behave as a low-wavelength pass, and the PDs with Au/Ag bimetallic NPs appear as a band-wavelength pass PD with a full width at half maximum of 450 ∼ 630 nm. The issue of wavelength-band tuning is due to the different plasmonic resonance wavelengths associated with various metallic NPs. The extinction plot shows the Au NPs have a longer resonant wavelength of about 545 nm, leading to the incident light with a wavelength near or longer than 545 nm scattered by the Au NPs, hence a high-wavelength pass PD. The PDs with Ag NPs, due to the Ag NPs, exhibit a short resonant wavelength of 430 nm, and the short-wavelength incident light is absorbed near the silicon (Si) surface, where the Ag NPs is atop it. The shorter-wavelength incident light is enhanced by the plasmonic resonance of Ag NPs, making a low-wavelength PD. The Au/Ag NPs presents a resonant wavelength of 500 nm between the Au and Ag NPs. For the incident light with a wavelength close to 500 nm, a constructive interference causes a substantial increase in the local electromagnetic field, hence leading to a band-wavelength pass PD.

  5. A room temperature LSO/PIN photodiode PET detector module that measures depth of interaction

    International Nuclear Information System (INIS)

    The authors present measurements of a 4 element PET detector module that uses a 2 x 2 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 3 x 3 x 25 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 ''lossy'' 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 C with a photodiode amplifier peaking time of 2 micros. 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

  6. 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.)

  7. Gamma-ray spectroscopy using CsI and silicon Pine photodiodes

    Energy Technology Data Exchange (ETDEWEB)

    Jeon, Taehoon; Jeong, Sungyeop; Kwon, Soocheon [Sungwoo E and T, Seoul (Korea, Republic of)

    2010-07-01

    The Finger generally uses two detector modules which are parallel for each other. They are all scintillator coupled photodiode detectors and the thickness of coupled photodiode detectors and the thickness of each scintillator is designed to absorb about 80% of radiations entering the scintillator. In order to acquire more detail information and reduce the error of measuring the ratio, the sensitivity of each detector should be improved. In this study, we proposed a new idea to increase the sensitivity of each detector by using two parallel detector modules for gamma-ray radiography. The aim of this work was to evaluate the ability of the new detector to improve the signal to noise ration, and to establish the methodology for counting in the new detector module with coincidence spectroscopy circuit. For this purpose, we optimized the scintillator thickness for {sup 60}Co by the Monte Carlo simulation code and the characteristics of operation and noise tests were accomplished after Scintillator coupling. We fabricated the Pine photodiode coupled with crystal for the Finger. We performed experiments and analyzed the results concentrating on the characteristics of signal and noise with Pine photodiode and CSR to detect high energy gamma and dominant factors to minimize system noise were capacitance than dark current of photodiode. As a result of measurement using the two parallel detector modules in this study, the sensitivity was considerably improved. We proved that our detector system is reliable for Finger.

  8. Subsampling effects in neuronal avalanche distributions recorded in vivo

    Directory of Open Access Journals (Sweden)

    Munk Matthias HJ

    2009-04-01

    Full Text Available Abstract Background Many systems in nature are characterized by complex behaviour where large cascades of events, or avalanches, unpredictably alternate with periods of little activity. Snow avalanches are an example. Often the size distribution f(s of a system's avalanches follows a power law, and the branching parameter sigma, the average number of events triggered by a single preceding event, is unity. A power law for f(s, and sigma = 1, are hallmark features of self-organized critical (SOC systems, and both have been found for neuronal activity in vitro. Therefore, and since SOC systems and neuronal activity both show large variability, long-term stability and memory capabilities, SOC has been proposed to govern neuronal dynamics in vivo. Testing this hypothesis is difficult because neuronal activity is spatially or temporally subsampled, while theories of SOC systems assume full sampling. To close this gap, we investigated how subsampling affects f(s and sigma by imposing subsampling on three different SOC models. We then compared f(s and sigma of the subsampled models with those of multielectrode local field potential (LFP activity recorded in three macaque monkeys performing a short term memory task. Results Neither the LFP nor the subsampled SOC models showed a power law for f(s. Both, f(s and sigma, depended sensitively on the subsampling geometry and the dynamics of the model. Only one of the SOC models, the Abelian Sandpile Model, exhibited f(s and sigma similar to those calculated from LFP activity. Conclusion Since subsampling can prevent the observation of the characteristic power law and sigma in SOC systems, misclassifications of critical systems as sub- or supercritical are possible. Nevertheless, the system specific scaling of f(s and sigma under subsampling conditions may prove useful to select physiologically motivated models of brain function. Models that better reproduce f(s and sigma calculated from the physiological

  9. Electron-avalanche amplifier based on the electronic Venturi effect

    Science.gov (United States)

    Taubert, D.; Schinner, G. J.; Tranitz, H. P.; Wegscheider, W.; Tomaras, C.; Kehrein, S.; Ludwig, S.

    2010-10-01

    Scattering of otherwise ballistic electrons far from equilibrium is investigated in a cold two-dimensional electron system. The interaction between excited electrons and the degenerate Fermi liquid induces a positive charge in a nanoscale region which would be negatively charged for diffusive transport at local thermal equilibrium. In a three-terminal device we observe avalanche amplification of electrical current, resulting in a situation comparable to the Venturi effect in hydrodynamics. Numerical calculations using a random-phase approximation are in agreement with our data and suggest Coulomb interaction as the dominant scattering mechanism.

  10. Simulation of a flowing snow avalanche using molecular dynamics

    OpenAIRE

    Güçer, Denizhan; ÖZGÜÇ, Halil Bülent

    2014-01-01

    This paper presents an approach for the modeling and simulation of a flowing snow avalanche, which is formed of dry and liquefied snow that slides down a slope, using molecular dynamics and the discrete element method. A particle system is utilized as a base method for the simulation and marching cubes with real-time shaders are employed for rendering. A uniform grid-based neighbor search algorithm is used for collision detection for interparticle and particle-terrain interactions. A mass-spr...

  11. Comment on "Avalanche dynamics in evolution, growth and depinning models"

    CERN Document Server

    Dahlbom, M; Dahlbom, Mats; Irback, Anders

    1996-01-01

    In a recent paper Paczuski, Maslov and Bak present a comprehensive theory of avalanche dynamics in models of growth, interface depinning and evolution. One of their main results is the so-called gamma equation, which is claimed to be exact. In this note it is shown that this equation requires a numerical correction factor in order to become exact. The exactness is needed when using the equation to determine the exponent \\gamma. The correct equation is tested against numerical results for the Bak-Sneppen evolution model and two closely related models, and it turns out that it improves the description of data in a statistically significant way.

  12. Avalanche proton-boron fusion based on elastic nuclear collisions

    Science.gov (United States)

    Eliezer, Shalom; Hora, Heinrich; Korn, Georg; Nissim, Noaz; Martinez Val, Josè Maria

    2016-05-01

    Recent experiments done at Prague with the 600 J/0.2 ns PALS laser interacting with a layer of boron dopants in a hydrogen enriched target have produced around 109 alphas. We suggest that these unexpected very high fusion reactions of proton with 11B indicate an avalanche multiplication for the measured anomalously high nuclear reaction yields. This can be explained by elastic nuclear collisions in the broad 600 keV energy band, which is coincident with the high nuclear p-11B fusion cross section, by the way of multiplication through generation of three secondary alpha particles from a single primarily produced alpha particle.

  13. GaN/InGaN avalanche phototransistors

    Science.gov (United States)

    Shen, Shyh-Chiang; Kao, Tsung-Ting; Kim, Hee-Jin; Lee, Yi-Che; Kim, Jeomoh; Ji, Mi-Hee; Ryou, Jae-Hyun; Detchprohm, Theeradetch; Dupuis, Russell D.

    2015-03-01

    We report on III-nitride (III-N) avalanche phototransistor (APT) action by illuminating ultraviolet (UV) photons onto a GaN/InGaN npn heterojunction bipolar transistor in an open-base configuration. A high responsivity of >1 A/W was measured for the device operating at a collector-to-emitter voltage (VCE) of 68 A/W at VCE = 95 V. The InGaN APT demonstrates the feasibility of using III-N bipolar transistor structures for high-sensitivity UV photodetection applications.

  14. AvaDrone: An Autonomous Drone for Avalanche Victim Recovery

    OpenAIRE

    Dickensheets, Benjamin D.

    2015-01-01

    For the 179 Americans that are caught in avalanches each year, timely recovery often means the difference between life and death. The goal of this project was to design and build a prototype drone for a system to quickly and automatically locate a buried victim, using an on-board antenna to receive a signal from industry standard transmitting beacons. The design was based on a quad-rotor platform and uses Arduino hardware to receive a beacon signal and navigate the craft. In broad strokes...

  15. Avalanche risk assessment for mountain roads - a comparison of case studies from Iceland and the Alps

    Science.gov (United States)

    Wastl, M.; Stötter, J.

    2009-04-01

    While the management of alpine natural hazards in settlements follows highly developed operational standardised procedures in many countries, there are very few approaches for a systematic survey and assessment of these natural hazard processes and the related risks and for a sustainable planning of measures for roads. This is even more surprising against the background of the ongoing increase of traffic in Europe and its economic importance. This contribution compares the results of a regional scale assessment of the avalanche risk on mountain roads for case studies from Austria, Italy and Iceland. It provides the first assessment of the natural hazard situation for roads outside closed settlements in Iceland and discusses the applicability of regional scale risk based approaches developed in the Alps to the specific natural, economic and social situation. It also compares the role of risk in the assessment and management of natural hazards in these countries. The assessment of the risk by natural hazard processes for roads follows approaches developed by Wilhelm (1997, 1998, 1999) and Borter (1999a, 1999b) in the Alps adapted to comply with the data availability of the regional scale. These approaches distinguish between the individual risk on the one hand and the collective risk for the society on the other hand for each process area as well as the cumulative risk for the investigated road section. As the spatial and temporal distribution of avalanches is relatively well documented in some of the Alpine countries practical approaches have been developed for the assessment of this natural hazard process. These have been successfully applied e.g. to roads in inner Oetz and inner Stubai Valley, Tyrol, Austria by Huttenlau (2004) and Gufler (2007) and Sulden road, Ortles Alps, Southern Tyrol, Italy by Zischg et al. (2004). On the basis of these investigations the individual, collective and cumulative death risk for avalanches was determined for Siglufjar

  16. The geomorphological effect of cornice fall avalanches in the Longyeardalen valley, Svalbard

    Science.gov (United States)

    Eckerstorfer, M.; Christiansen, H. H.; Rubensdotter, L.; Vogel, S.

    2013-09-01

    The study of snow avalanches and their geomorphological effect in the periglacial parts of the cryosphere is important for enhanced geomorphological process understanding as well as hazard-related studies. Only a few field studies, and particularly few in the High Arctic, have quantified avalanche sedimentation. Snow avalanches are traditionally ranked behind rockfall in terms of their significance for mass-wasting processes of rockslopes. Cornice fall avalanches are at present the most dominant snow avalanche type at two slope systems, called Nybyen and Larsbreen, in the valley Longyeardalen in central Svalbard. Both slope systems are on northwest-facing lee slopes underneath a large summit plateau, with annual cornices forming on the top. High-frequency and magnitude cornice fall avalanching is observed by daily automatic time-lapse photography. In addition, rock debris sedimentation by cornice fall avalanches was measured directly in permanent sediment traps or by snow inventories. The results from a maximum of seven years of measurements in a total of 13 catchments show maximum mean rock debris sedimentation rates ranging from 8.2 to 38.7 kg m-2 at Nybyen, and from 0.8 to 55.4 kg m-2 at Larsbreen. Correspondingly, avalanche fan surfaces accreted from 2.6 to 8.8 mm yr-1 at Nybyen, and from 0.2 to 13.9 mm yr-1 at Larsbreen. This comparably efficient rockslope mass wasting is due to collapsing cornices producing cornice fall avalanches containing large amounts of rock debris throughout the entire winter. The rock debris of different origin stems from the plateau crests, the adjacent free rock face and the transport pathway, accumulating distinct avalanche fans at both slope systems. Cornice fall avalanche sedimentation also contributed to the development of a rock glacier at the Larsbreen site during the Holocene. We have recorded present maximum rockwall retreat rates of 0.9 mm yr-1 at Nybyen, but as much as 6.7 mm yr-1 at Larsbreen, while average Holocene

  17. Two examples of expert knowledge based system for avalanche forecasting and protection

    Science.gov (United States)

    Buisson, Laurent; Giraud, Gérald

    1995-11-01

    In avalanche modelling and control and in avalanche forecasting, most of the knowledge is based on scientific theory but the experience of specialists (field practitioners, forecasters...) plays a large role. This paper presents two French computer-based systems dedicated to avalanche modelling and control and to avalanche forecasting. They are both based on expert knowledge. ELSA (Etude et Limites de Sites d'Avalanches), is a computer system dedicated to the modelling of the knowledge of avalanche experts and to the integration of new symbolic computer models with classical numerical models. The basic aim of integration is to build a unique computer system incorporating all these models. After a description of the terrain representation, we present the different scenarios that ELSA takes into account. Then, the methods which deal with some phenomena occurring in avalanches are described. The problems involved in the integration of these methods close this first part. MEPRA is an expert system built to create an objective tool in avalanche risk forecasting. This development allowed us to imagine a processing system for 2 of the most important problems in avalanche risk forecasting: representation of the present snow cover characteristics and evaluation of avalanche instability and risk. In this way, mechanics and thermodynamics play a major role in the system. After a punctual validation at the location of a snow weather station and in order to describe the great variability of the snow pack and the avalanche risk in a massif, the MEPRA expert system was connected with a meteorological analysis system, SAFRAN and a numerical model to simulate the snow cover CROCUS. Then, every day, a MEPRA expert analysis is carried out in different locations with different orientations, slopes and altitudes. Its results were used successfully during the Winter Olympic Games of Albertville and by avalanche forecasters during the 92/93 winter season. The daily avalanche risks

  18. Morphological analysis of hummocks in debris avalanche deposits using UAS-derived high-definition topographic data

    Science.gov (United States)

    Hayakawa, Yuichi S.; Obanawa, Hiroyuki; Yoshida, Hidetsugu; Naruhashi, Ryutaro; Okumura, Koji; Zaiki, Masumi

    2016-04-01

    Debris avalanche caused by sector collapse of a volcanic mountain often forms depositional landforms with characteristic surface morphology comprising hummocks. Geomorphological and sedimentological analyses of debris avalanche deposits (DAD) at the northeastern face of Mt. Erciyes in central Turkey have been performed to investigate the mechanisms and processes of the debris avalanche. The morphometry of hummocks provides an opportunity to examine the volumetric and kinematic characteristics of the DAD. Although the exact age has been unknown, the sector collapse of this DAD was supposed to have occurred in the late Pleistocene (sometime during 90-20 ka), and subsequent sediment supply from the DAD could have affected ancient human activities in the downstream basin areas. In order to measure detailed surface morphology and depositional structures of the DAD, we apply structure-from-motion multi-view stereo (SfM-MVS) photogrammetry using unmanned aerial system (UAS) and a handheld camera. The UAS, including small unmanned aerial vehicle (sUAV) and a digital camera, provides low-altitude aerial photographs to capture surface morphology for an area of several square kilometers. A high-resolution topographic data, as well as an orthorectified image, of the hummocks were then obtained from the digital elevation model (DEM), and the geometric features of the hummocks were examined. A handheld camera is also used to obtain photographs of outcrop face of the DAD along a road to support the seimentological investigation. The three-dimensional topographic models of the outcrop, with a panoramic orthorectified image projected on a vertical plane, were obtained. This data enables to effectively describe sedimentological structure of the hummock in DAD. The detailed map of the DAD is also further examined with a regional geomorphological map to be compared with other geomorphological features including fluvial valleys, terraces, lakes and active faults.

  19. An absorption detection approach for multiplexed capillary electrophoresis using a linear photodiode array.

    Science.gov (United States)

    Gong, X; Yeung, E S

    1999-11-01

    A novel absorption detection method for highly multiplexed capillary electrophoresis is presented for zone electrophoresis and for micellar electrokinetic chromatography. The approach involves the use of a linear photodiode array on which a capillary array is imaged by a camera lens. Either a tungsten lamp or a mercury lamp can be used as the light source such that all common wavelengths for absorption detection are accessible by simply interchanging narrow-band filters. Each capillary spans several diodes in the photodiode array for absorption measurements. Over 100 densely packed capillaries can be monitored by a single photodiode array element with 1024 diodes. The detection limit for rhodamine 6G for each capillary in the multiplexed array is ∼1.8 × 10(-)(8) M injected (S/N = 2). The cross-talk between adjacent capillaries is less than 0.2%. Simultaneous analysis of 96 samples is demonstrated. PMID:21662842

  20. Fast, Deep-Record-Length, Fiber-Coupled Photodiode Imaging Array for Plasma Diagnostics

    Science.gov (United States)

    Brockington, Samuel; Case, Andrew; Witherspoon, F. Douglas

    2015-11-01

    HyperV Technologies has been developing an imaging diagnostic comprised of an array of fast, low-cost, long-record-length, fiber-optically-coupled photodiode channels to investigate plasma dynamics and other fast, bright events. By coupling an imaging fiber bundle to a bank of amplified photodiode channels, imagers and streak imagers can be constructed. By interfacing analog photodiode systems directly to commercial analog-to-digital converters and modern memory chips, a scalable solution for 100 to 1000 pixel systems with 14 bit resolution and record-lengths of 128k frames has been developed. HyperV is applying these techniques to construct a prototype 1000 Pixel framing camera with up to 100 Msamples/sec rate and 10 to 14 bit depth. Preliminary experimental results as well as future plans will be discussed. Work supported by USDOE Phase 2 SBIR Grant DE-SC0009492.

  1. Reverse current reduction of Ge photodiodes on Si without post-growth annealing Invited Paper

    Institute of Scientific and Technical Information of China (English)

    Sungbong Park; Shinya Takita; Yasuhiko; Ishikawa; Jiro Osaka; Kazumi Wada

    2009-01-01

    A new approach to reduce the reverse current of Ge pin photodiodes on Si is presented, in which an i-Si layer is inserted between Ge and top Si layers to reduce the electric field in the Ge layer. Without post- growth annealing, the reverse current density is reduced to ~10 mA/cm2 at -1 V, i.e., over one order of magnitude lower than that of the reference photodiode without i-Si layer. However, the responsivity of the photodiodes is not severely compromised. This lowered-reverse-current is explained by band-pinning at the i-Si/i-Ge interface. Barrier lowering mechanism induced by E-field is also discussed. The presented "non-thermal" approach to reduce reverse current should accelerate electronics-photonics convergence by using Ge on the Si complementary metal oxide semiconductor (CMOS) platform.

  2. Study of commercial Si-PIN photodiode as an x-ray detector

    International Nuclear Information System (INIS)

    Two commercial Si-PIN photodiode were evaluated as a low cost X-ray detector in conjunction with forward biased FET preamplifiers. Evaluation was done at room temperature and at a temperature of about -10degC using X-ray spectroscopy amplifier with 241Am radio active source. The results shows 700 eV full width at half maximum for 241Am γ-ray (59.5 keV) with S5821-02 from Hamamatsu Photonics at low temperature and 800 eV with S1722-02 at the same conditions. The S1722-02 photodiode showed almost flat response up to 20 keV X-ray energy. The improvement of photodiode and FET cooling system and proper selection of FET will be expected to show better resolution. (author)

  3. High-performance evanescently-coupled uni-traveling-carrier photodiodes

    Institute of Scientific and Technical Information of China (English)

    Zhang Yun-Xiao; Liao Zai-Yi; Wang Wei

    2009-01-01

    A new evanescently-coupled uni-traveling-carrier photodiode (EC-UTC PD) based on a multimode diluted waveguide (MDW) structure is fabricated, analysed and characterized. Optical and electrical characteristics of the device are investigated. The excellent characteristics are demonstrated such as a responsivity of 0.36 A/W, a bandwidth of 11.5 GHz and a small-signal 1-dB compression current greater than 18 mA at 10 GHz. The saturation current is significantly improved compared with those of similar evanescently-coupled pin photodiodes. The radio frequency (RF)bandwidth can be further improved by eliminating RF losses induced by the cables, the probe and the bias tee between the photodiode and the spectrum analyzer.

  4. Studies Supporting PMT Characterization for the IceCube Collaboration: Precise Photodiode Calibration

    CERN Document Server

    Van De Pontseele, Wouter

    2015-01-01

    A laboratory set-up has been developed to more precisely measure the DOM optical sensitivity as a function of angle and wavelength. DOMs are calibrated in water using a broad beam of light whose intensity is measured with a NIST calibrated photodiode. This study will refine the current knowledge of the IceCube response and lay a foundation for future precision upgrades to the detector. Good understanding of the photodiode readout is indispensable for the DOM calibration. Corrections to the photodiode measurements due to the amplifier circuit were investigated. To accomplish this, a general software structure has been added to the existing framework. Because the set of parameters in the source sector is still growing, modularity and a high level of automation were important objectives. The software features a large array of graphical tools to intercept problems at low level while the analysis can be easily adapted to the needs of foreseeable situations.

  5. Assessing wet snow avalanche activity using detailed physics based snowpack simulations

    Science.gov (United States)

    Wever, N.; Vera Valero, C.; Fierz, C.

    2016-06-01

    Water accumulating on microstructural transitions inside a snowpack is often considered a prerequisite for wet snow avalanches. Recent advances in numerical snowpack modeling allow for an explicit simulation of this process. We analyze detailed snowpack simulations driven by meteorological stations in three different climate regimes (Alps, Central Andes, and Pyrenees), with accompanying wet snow avalanche activity observations. Predicting wet snow avalanche activity based on whether modeled water accumulations inside the snowpack locally exceed 5-6% volumetric liquid water content is providing a higher prediction skill than using thresholds for daily mean air temperature, or the daily sum of the positive snow energy balance. Additionally, the depth of the maximum water accumulation in the simulations showed a significant correlation with observed avalanche size. Direct output from detailed snow cover models thereby is able to provide a better regional assessment of dangerous slope aspects and potential avalanche size than traditional methods.

  6. SWAD: inherent photon counting performance of amorphous selenium multi-well avalanche detector

    Science.gov (United States)

    Stavro, Jann; Goldan, Amir H.; Zhao, Wei

    2016-03-01

    Photon counting detectors (PCDs) have the potential to improve x-ray imaging, however they are still hindered by several performance limitations and high production cost. By using amorphous Selenium (a-Se) the cost of PCDs can be significantly reduced compared to crystalline materials and enable large area detector fabrication. To overcome the problem of low carrier mobility and low charge conversion gain in a-Se, we are developing a novel direct conversion a- Se field-Shaping multi-Well Avalanche Detector (SWAD). SWAD circumvents the charge transport limitation by using a Frisch grid built within the readout circuit, reducing charge collection time to ~200 ns. Field shaping permits depth independent avalanche gain in wells, resulting in total conversion gain that is comparable to Si and CdTe. In the present work we investigate the effects of charge sharing and energy loss to understand the inherent photon counting performance for SWAD at x-ray energies used in breast imaging applications (20-50keV). The energy deposition profile for each interacting x-ray was determined with Monte Carlo simulation. For the energy ranges we are interested in, photoelectric interaction dominates, with a k-fluorescence yield of approximately 60%. Using a monoenergetic 45 keV beam incident on a target pixel in 400um of a-Se, our results show that only 20.42 % and 22.4 % of primary interacting photons have kfluorescence emissions which escape the target pixel for 100um and 85um pixel sizes respectively, demonstrating SWAD's potential for high spatial resolution applications.

  7. Validating numerical simulations of snow avalanches using dendrochronology: the Cerro Ventana event in Northern Patagonia, Argentina

    Science.gov (United States)

    Casteller, A.; Christen, M.; Villalba, R.; Martínez, H.; Stöckli, V.; Leiva, J. C.; Bartelt, P.

    2008-05-01

    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 textit{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.

  8. Comparison of seismic and infrasound wave fields generated by snow avalanches

    Science.gov (United States)

    Suriñach, Emma; Tapia, Mar; Pérez-Guillén, Cristina; Khazaradze, Giorgi; Roig, Pere

    2016-04-01

    Snow avalanches are a source of waves that are transmitted through the ground and the air. These wave fields are detected by seismic and infrasound sensors. During the winter seasons 2008 -2016, a good quality database of avalanches was obtained at the VdlS test site with an accurate instrumentation. These avalanches were both natural and artificially triggered and were of varying types and sizes. Distances involved were 0.5 -3 km. Seismic signals were acquired using three seismometers (3-components, 1Hz) spaced 600 m apart along the avalanche track. One infrasound sensor (0.1Hz) and one seismometer (3-components, 1Hz) were placed one next to the other with a common base of time on the slope opposite the path. The database obtained enables us to compare the different signals generated. Differences in the frequency content and shape of the signals depending on the type and size of the avalanche are detected. A clear evolution of the recorded seismic signals along the path is observed. The cross correlation of the infrasound and seismic signals generated by the avalanches allows us to determine different characteristics for powder, transitional and wet avalanches concerning their wave fields. The joint analysis of infrasound and seismic waves enables us to obtain valuable information about the internal parts of the avalanche as a source of each wave field. This study has repercussions on avalanche dynamics and on the selection of the appropriate avalanche detection system. This study is supported by the Spanish Ministry of Science and Innovation project CHARMA: CHAracterization and ContRol of MAss Movements. A Challenge for Geohazard Mitigation (CGL2013-40828-R), and RISKNAT group (2014GR/1243).

  9. 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.

  10. An Atomically Layered InSe Avalanche Photodetector.

    Science.gov (United States)

    Lei, Sidong; Wen, Fangfang; Ge, Liehui; Najmaei, Sina; George, Antony; Gong, Yongji; Gao, Weilu; Jin, Zehua; Li, Bo; Lou, Jun; Kono, Junichiro; Vajtai, Robert; Ajayan, Pulickel; Halas, Naomi J

    2015-05-13

    Atomically thin photodetectors based on 2D materials have attracted great interest due to their potential as highly energy-efficient integrated devices. However, photoinduced carrier generation in these media is relatively poor due to low optical absorption, limiting device performance. Current methods for overcoming this problem, such as reducing contact resistances or back gating, tend to increase dark current and suffer slow response times. Here, we realize the avalanche effect in a 2D material-based photodetector and show that avalanche multiplication can greatly enhance the device response of an ultrathin InSe-based photodetector. This is achieved by exploiting the large Schottky barrier formed between InSe and Al electrodes, enabling the application of a large bias voltage. Plasmonic enhancement of the photosensitivity, achieved by patterning arrays of Al nanodisks onto the InSe layer, further improves device efficiency. With an external quantum efficiency approaching 866%, a dark current in the picoamp range, and a fast response time of 87 μs, this atomic layer device exhibits multiple significant advances in overall performance for this class of devices.

  11. Supershort avalanche electron beam in SF6 and krypton

    Science.gov (United States)

    Zhang, Cheng; Tarasenko, Victor F.; Gu, Jianwei; Baksht, Evgeni Kh.; Beloplotov, Dmitry V.; Burachenko, Alexander G.; Yan, Ping; Lomaev, Mikhail I.; Shao, Tao

    2016-03-01

    Runaway electrons play an important role in the avalanche formation in nanosecond- and subnanosecond- pulse discharges. In this paper, characteristics of a supershort avalanche electron beam (SAEB) generated at the subnanosecond and nanosecond breakdown in sulfur hexafluoride (SF6 ) in an inhomogeneous electric field were studied. One pulser operated at negative polarity with voltage pulse amplitude of ˜130 kV and rise time of 0.3 ns. The other pulser operated at negative polarity with voltage pulse amplitude of 70 kV and rise time of ˜1.6 ns . SAEB parameters in SF6 are compared with those obtained in krypton (Kr), nitrogen (N2 ), air, and mixtures of SF6 with krypton or nitrogen. Experimental results showed that SAEB currents appeared during the rise-time of the voltage pulse for both pulsers. Moreover, amplitudes of the SAEB current in SF6 and Kr approximately ranged from several to tens of milliamps at atmospheric pressure, which were smaller than those in N2 and air (ranging from hundreds of milliamps to several amperes). Furthermore, the concentration of SF6 additive could significantly reduce the SAEB current in N2-SF6 mixture, but it slightly affected the SAEB current in Kr -SF6 mixture because of the atomic/molecular ionization cross section of the gas had a much greater impact on the SAEB current rather than the electronegativity.

  12. Enhanced Avalanche Ionization by RF Fields Creating an Ultracold Plasma

    Science.gov (United States)

    Robinson, M. P.; Gallagher, T. F.; Laburthe Tolra, B.; Pillet, P.

    2001-05-01

    Ultracold plasmas have been shown to evolve from initially frozen Rydberg gases held in magneto-optical traps.(M.P. Robinson, B. Laburthe Tolra, Michael W. Noel, T.F. Gallagher, and P. Pillet, Phys. Rev. Lett. 85), 4466 (2000) We report the enhancement of the avalanche ionization process by application of radiofrequency fields. An initial slow ionization rate is observed in the Rydberg sample due to black body ionization and ionizing collisions with hot Rydberg atoms. This produces an overall posititve space charge of cold ions as the hot electrons leave the sample. Once a threshold density of positive charges is built up, the hot electrons become trapped to the sample, leading to avalance ionization due to electron-Rydberg collisions. The mechanism of the ionization remains unclear. However, the application of radiofrequency fields, in the 1 V/cm, 100 MHz range, dramatically enhances the rate of avalanche ionization without changing the threshold density at which it occurs. Apparently, the limiting parameter is the rate of collisional ionization of Rydberg atoms by electrons.

  13. Scaling of avalanche queues in directed dissipative sandpiles

    Science.gov (United States)

    Tadic; Priezzhev

    2000-09-01

    Using numerical simulations and analytical methods we study a two-dimensional directed sandpile automaton with nonconservative random defects (concentration c) and varying driving rate r. The automaton is driven only at the top row and driving rate is measured by the number of added particles per time step of avalanche evolution. The probability distribution of duration of elementary avalanches at zero driving rate is exactly given by P1(t,c)=t(-3/2) exp[t ln(1-c)]. For driving rates in the interval 0 server queue in the queue theory. We study scaling properties of the busy period and dissipated energy of sequences of noninterrupted activity. In the limit c-->0 and varying linear system size Lqueues are characterized by a multifractal scaling and we determine the corresponding spectral functions. For L>1/c increasing the driving rate somewhat compensates for the energy losses at defects above the line r approximately sqrt[c]. The scaling exponents of the distributions in this region of phase diagram vary approximately linearly with the driving rate. Using properties of recurrent states and the probability theory we determine analytically the exact upper bound of the probability distribution of busy periods. In the case of conservative dynamics c=0 the probability of a continuous flow increases as F(infinity) approximately r(2) for small driving rates. PMID:11088824

  14. Silicon Avalanche Pixel Sensor for High Precision Tracking

    CERN Document Server

    D'Ascenzo, N; Moon, C S; Morsani, F; Ratti, L; Saveliev, V; Navarro, A Savoy; Xie, Q

    2013-01-01

    The development of an innovative position sensitive pixelated sensor to detect and measure with high precision the coordinates of the ionizing particles is proposed. The silicon avalanche pixel sensors (APiX) is based on the vertical integration of avalanche pixels connected in pairs and operated in coincidence in fully digital mode and with the processing electronics embedded on the chip. The APiX sensor addresses the need to minimize the material budget and related multiple scattering effects in tracking systems requiring a high spatial resolution in the presence of a large occupancy. The expected operation of the new sensor features: low noise, low power consumption and suitable radiation tolerance. The APiX device provides on-chip digital information on the position of the coordinate of the impinging charged particle and can be seen as the building block of a modular system of pixelated arrays, implementing a sparsified readout. The technological challenges are the 3D integration of the device under CMOS ...

  15. A near infrared organic photodiode with gain at low bias voltage

    Energy Technology Data Exchange (ETDEWEB)

    Campbell, Ian H [Los Alamos National Laboratory; Crone, Brian K [Los Alamos National Laboratory

    2009-01-01

    We demonstrate an organic photodiode with near infrared optical response out to about 1100 run with a gain of {approx}10 at 1000 run under 5V reverse bias. The diodes employ a soluble naphthalocyanine with a peak absorption coefficient of {approx}10{sup 5} cm{sup -1} at 1000 nm. In contrast to most organic photodiodes, no exciton dissociating material is used. At zero bias, the diodes are inefficient with an external quantum efficiency of {approx} 10{sup -2}. In reverse bias, large gain occurs and is linear with bias voltage above 4V. The observed gain is consistent with a photoconductive gain mechanism.

  16. Comparative Study of Gamma Radiation Effects on Solar Cells, Photodiodes, and Phototransistors

    Directory of Open Access Journals (Sweden)

    Dejan Nikolić

    2013-01-01

    Full Text Available This paper presents the behavior of various optoelectronic devices after gamma irradiation. A number of PIN photodiodes, phototransistors, and solar panels have been exposed to gamma irradiation. Several types of photodiodes and phototransistors were used in the experiment. I-V characteristics (current dependance on voltage of these devices have been measured before and after irradiation. The process of annealing has also been observed. A comparative analysis of measurement results has been performed in order to determine the reliability of optoelectronic devices in radiation environments.

  17. 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

  18. Dark Current Reduction of P3HT-Based Organic Photodiode Using a Ytterbium Fluoride Buffer Layer in Electron Transport

    CERN Document Server

    Lim, Seong Bin; Kim, Ki Tae; Oh, Se Young

    2016-01-01

    Photodiodes are widely used to convert lights into electrical signals. The conventional silicon (Si) based photodiodes boast high photoelectric conversion efficiency and detectivity. However, in general, inorganic-based photodiodes have low visible wavelength sensitivity due to their infrared wavelength absorption. Recently, electrical conducting polymer-based photodiodes have received significant attention due to their flexibility, low cost of production and high sensitivity of visible wavelength ranges. In the present work, we fabricated an organic photodiode (OPD) consisting of ITO/ NiOx/ P3HT:PC60BM/ YbF3/ Al. In the OPD, a yitterbium fluoride (YbF3) buffer layer was used as the electron transport layer. The OPD was analyzed for its optical-electrical measurements, including J-V characteristics, detectivity and dynamic characteristics. We have investigated the physical effects of the YbF3 buffer layer on the performance of OPD such as its carrier extraction, leakage current and ohmic characteristics.

  19. Investigation of CMOS photodiodes integrated on an ASIC by a 0.5-µm analog CMOS process

    Science.gov (United States)

    Luo, H.; Ricklefs, U.; Hillmer, H.

    2010-04-01

    The characteristics of photodiodes integrated on CMOS ASICs depend on wavelength of radiation, structure of the photodiode itself and the parameters of the process of production. In this paper, the influence of the structure of integrated CMOS photodiodes produced in a standard 0.5 μm mixed signal CMOS process on the sensitivity is described. These photodiodes are used as image sensor elements arranged in an array for noncontact optoelectronic measurements. Models of integrated photodiodes distinguish the lateral and the vertical region of the photodiodes. The standard 0.5 μm CMOS process offers three types of pn-junctions: n+/p-substrate, p+/n-well and n-well/p-substrate. Based on our previous research and on the results from other authors the p+/n-well is chosen due to its better sensitivity and isolation against other structures. The local sensitivity is measured with a scanning setup by applying a diffraction limited spot spot of light on the surface of the diodes. Independent of the wavelength of radiation the charge carriers are generated mainly in the lateral region and not - as expected - in the vertical region. The maximum value of the local sensitivity is found in photodiodes with subdivided p+ regions showing a distance of 1.5 μm between these regions in the space between these two adjacent p+ regions. This local sensitivity is three times smaller than that of a reference PIN photodiode. According to this result, the new photodiodes will be constructed with optimized geometries. All examined structures of this type of photodiodes show a maximal spectral sensitivity in the range of 650 nm - 700 nm.

  20. Avalanche dynamics in the Bak-Sneppen evolution model observed with a standard distribution width of fitness

    Science.gov (United States)

    Lee, Chaohong; Zhu, Xiwen; Gao, Kelin

    2003-01-01

    We introduce the standard distribution width of fitness to characterize the global and individual features of an ecosystem described by the Bak-Sneppen evolution model. Through tracking this quantity in evolution, a different hierarchy of avalanche dynamics, the w0 avalanche, is observed. The corresponding gap equation and the self-organized threshold wc are obtained. The critical exponents τ, γ and ρ, which describe the behaviour of the avalanche size distribution, the average avalanche size and the relaxation to attractor, respectively, are calculated by numerical simulation. The exact master equation and γ equation are derived, and the scaling relations are established among the critical exponents of this new avalanche.

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

    International Nuclear Information System (INIS)

    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. Dendrogeomorphology and high-magnitude snow avalanches: a review and case study

    Directory of Open Access Journals (Sweden)

    D. R. Butler

    2008-04-01

    Full Text Available The application of the principles of dendrogeomorphology for the dating of high-magnitude snow avalanches is well established in the natural hazards literature. A variety of methodologies are employed by different authors, however, and no standardization currently exists for appropriate sample sizes, the issue of "weighting" certain tree-ring responses as more important than others, or the minimum number of responding trees required in order to infer an avalanche event. We review the literature of dendrogeomorphology as it applies to snow avalanches, and examine the questions of sample size, type of ring reactions dated and weighted, and minimum responses. We present tree-ring data from two avalanche paths in the Rocky Mountains of Montana, USA, from trees uprooted by major snow avalanches in the winter of 2002. These data provide distinct chronologies of past avalanche events, and also illustrate how the critical choice of a minimum Index Number can affect the number of avalanche events in a final chronology based on tree-ring analysis.

  3. Avalanche risk in backcountry terrain based on usage frequency and accident data

    Directory of Open Access Journals (Sweden)

    F. Techel

    2014-08-01

    Full Text Available In Switzerland, the vast majority of avalanche accidents occurs during recreational activities. Risk analysis studies mostly rely on accident statistics without considering exposure (or the elements at risk, i.e. how many and where people are recreating. We compared the accident data (backcountry touring with reports from two social media mountaineering networks – bergportal.ch and camptocamp.org. On these websites, users reported more than 15 000 backcountry tours during the five winters 2009/2010 to 2013/2014. We noted similar patterns in avalanche accident data and user data like demographics of recreationists, distribution of the day of the week (weekday vs. weekend or weather conditions (fine vs. poor weather. However, we also found differences such as the avalanche danger conditions on days with activities and accidents, but also the geographic distribution. While backcountry activities are concentrated in proximity to the main population centres in the West and North of the Swiss Alps, a large proportion of the severe avalanche accidents occurred in the inner-alpine, more continental regions with frequently unfavorably snowpack structure. This suggests that even greater emphasis should be put on the type of avalanche problem in avalanche education and avalanche forecasting to increase the safety of backcountry recreationists.

  4. Slab entrainment and surge dynamics of the 2015 Valleé de la Sionne avalanches

    Science.gov (United States)

    Köhler, Anselm; McElwaine, Jim; Sovilla, Betty

    2016-04-01

    On 3 February 2015 five avalanches were artificially released at the Valleé de la Sionne test site in the west of Switzerland. The dense parts of the avalanches were tracked by the GEODAR Mark 2 radar system at 111 Hz framerate with 0.75 m down slope resolution. The data show that these avalanche contain several internal surges and that the avalanche front is repeatedly overtaken by some of these surges. We show that these surges exist on different scale. While the major surges originates from secondary triggered slab releases and occur all over the avalanche. The minor surges are only found in the energetic part of a well developed powder snow avalanche. The mass of the major surges can be as huge as the initial released mass, this has a dramatic effect on the mass distribution inside the avalanche and effects the front velocity and run out. Furthermore, the secondary released snow slabs are an important entrainment mechanism and up to 50 percent of the mass entered the avalanche via slab entrainment. We analyse the dynamics of the leading edge and the minor surges in more detail using a simple one dimensional model with frictional resistance and quadratic velocity dependent drag. These models fit the data well for the start and middle of avalanche but cannot capture the slowing and overtaking of the minor surge. We find much higher friction coefficients to describe the surging. We propose that this data can only be explained by changes in the snow surface. These effects are not included in current models yet, but the data presented here will enable the development and verification of such models.

  5. 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 ...

  6. Elimination or minimisation of optoelectronic crosstalk between photodiodes and electronic devices in OEIC on Si

    NARCIS (Netherlands)

    Zhou, M.-J.; Holleman, J.; Wallinga, H.

    1994-01-01

    The optoelectronic crosstalk between photodiodes and electronic devices is observed and investigated in OEICs based on silicon. Results show that the phenomenon is closely related to the diffusion of minority carriers, generated by photon absorption. The crosstalk can be eliminated or minimised by e

  7. HPLC-photodiode array detection analysis of curcuminoids in Curcuma species indigenous to Indonesia

    NARCIS (Netherlands)

    Bos, Rein; Windono, Tri; Woerdenbag, Herman J.; Boersma, Ykelien L.; Koulman, Albert; Kayser, Oliver

    2007-01-01

    An optimized HPLC method with photodiode array detection was developed and applied to analyse the curcuminoids curcumin, demethoxycurcumin, and bis-demethoxycurcumin in rhizomes of Curcuma mangga Val &. v. Zijp, C. heyneana Val. & v. Zijp, C. aeruginosa Roxb. and C. soloensis Val. (Zingiberaceae), i

  8. High-speed optical receivers with integrated photodiode in nanoscale CMOS

    CERN Document Server

    Tavernier, Filip

    2011-01-01

    This book describes the design of optical receivers that use the most economical integration technology, while enabling performance that is typically only found in very expensive devices. To achieve this, all necessary functionality, from light detection to digital output, is integrated on a single piece of silicon. All building blocks are thoroughly discussed, including photodiodes, transimpedance amplifiers, equalizers and post amplifiers.

  9. Experimental analysis of a novel and low-cost pin photodiode dosimetry system for diagnostic radiology

    Science.gov (United States)

    Nazififard, Mohammad; Suh, Kune Y.; Mahmoudieh, Afshin

    2016-07-01

    Silicon PIN photodiode has recently found broad and exciting applications in the ionizing radiation dosimetry. In this study a compact and novel dosimetry system using a commercially available PIN photodiode (BPW34) has been experimentally tested for diagnostic radiology. The system was evaluated with clinical beams routinely used for diagnostic radiology and calibrated using a secondary reference standard. Measured dose with PIN photodiode (Air Kerma) varied from 10 to 430 μGy for tube voltages from 40 to 100 kVp and tube current from 0.4 to 40 mAs. The minimum detectable organ dose was estimated to be 10 μGy with 20% uncertainty. Results showed a linear correlation between the PIN photodiode readout and dose measured with standard dosimeters spanning doses received. The present dosimetry system having advantages of suitable sensitivity with immediate readout of dose values, low cost, and portability could be used as an alternative to passive dosimetry system such as thermoluminescent dosimeter for dose measurements in diagnostic radiology.

  10. On The Pixel Level Estimation of Pinning Voltage, Pinned Photodiode Capacitance and Transfer Gate Channel Potential

    OpenAIRE

    Goiffon, Vincent; Michelot, Julien; Magnan, Pierre; Estribeau, Magali; Marcelot, Olivier; Cervantes, Paola; Pelamatti, Alice; Martin-Gonthier, Philippe

    2013-01-01

    The pinning voltage extraction method proposed by Tan et al. is analyzed to clarify its benefits and limitations. It is demonstrated that this simple measurement can bring much more useful information than the pinning voltage, such as the pinned photodiode capacitance and the transfer gate channel potential. Objective criteria to compare the pinning voltage on different devices are also discussed.

  11. Investigation of dark current random telegraph signal in pinned photodiode CMOS image sensors

    OpenAIRE

    Goiffon, Vincent; Virmontois, Cédric; Magnan, Pierre

    2011-01-01

    The characteristics of Dark Current Random Telegraph Signal (DC-RTS), observed in Pinned PhotoDiode (PPD) CMOS Image Sensors (CIS), are investigated thanks to a dedicated analysis tool. Our results demonstrate, for the first time in PPD CIS, that this DC-RTS is due to meta-stable oxide interface SRH generation centers located in the transfer gate depletion region.

  12. A new circuit model of HgCdTe photodiode for SPICE simulation of integrated IRFPA

    Science.gov (United States)

    Saxena, Raghvendra Sahai; Saini, Navneet Kaur; Bhan, R. K.; Sharma, R. K.

    2014-11-01

    We propose a novel sub circuit model to simulate HgCdTe infrared photodiodes in a circuit simulator, like PSPICE. We have used two diodes of opposite polarity in parallel to represent the forward biased and the reverse biased behavior of an HgCdTe photodiode separately. We also connected a resistor in parallel with them to represent the ohmic shunt and a constant current source to represent photocurrent. We show that by adjusting the parameters in standard diode models and the resistor and current values, we could actually fit the measured data of our various HgCdTe photodiodes having different characteristics. This is a very efficient model that can be used for simulation of readout integrated circuit (ROIC) for HgCdTe IR photodiode arrays. This model also allows circuit level Monte Carlo simulation on a complete IRFPA at a single circuit simulator platform to estimate the non-uniformity for given processes of HgCdTe device fabrication and Si ROIC fabrication.

  13. High-sensitivity high-stability silicon photodiodes for DUV, VUV and EUV spectral ranges

    NARCIS (Netherlands)

    Shi, L.; Nihtianov, S.; Scholze, F.; Gottwald, A.; Nanver, L.K.

    2011-01-01

    In this paper, the optical and electrical performance of a newly developed silicon photodiode based on pure boron CVD technology (PureB-diodes) is introduced. Due to their extremely shallow p-n junction, with the depletion zone starting only a few nanometers below the surf ce, and nm-thin pure-boron

  14. Passivation of MBE grown InGaSb/InAs superlattice photodiodes

    Science.gov (United States)

    Hill, Cory J.; Keo, Sam S.; Mumolo, Jason M.; Gunapala, Sarath D.

    2005-01-01

    We have performed wet chemical passivation tests on InGaSb/InAs superlattice photodiode structures grown molecular beam epitaxy. The details of the devices growth and characterization as well as the results of chemical passivation involving RuCl3 and H2SO4 with SiO2 dielectric depositions are presented.

  15. Discrete element modeling of the mass movement and loose material supplying the gully process of a debris avalanche in the Bayi Gully, Southwest China

    Science.gov (United States)

    Zhou, Jia-wen; Huang, Kang-xin; Shi, Chong; Hao, Ming-hui; Guo, Chao-xu

    2015-03-01

    The dynamic process of a debris avalanche in mountainous areas is influenced by the landslide volume, topographical conditions, mass-material composition, mechanical properties and other factors. A good understanding of the mass movement and loose material supplying the gully process is very important for understanding the dynamic properties of debris avalanches. Three-dimensional particle flow code (PFC3D) was used to simulate a debris avalanche in Quaternary deposits at the Bayi Gully, Southwest China. FORTRAN and AutoCAD were used for the secondary development to display the mass movement process and to quantitatively describe the mass movement and loose material supplying the gully process. The simulated results show that after the landslide is initiated, the gravitational potential energy is converted into kinetic energy with a variation velocity for the sliding masses. Two stages exist for the average-movement velocity: the acceleration stage and the slowdown stage, which are influenced by the topographical conditions. For the loose materials supplying the gully process, the cumulative volume of the sliding masses into the gully gradually increases over the time. When the landslide volume is not large enough, the increasing landslide volume does not obviously influence the movement process of the sliding masses. The travel distance and movement velocity increase with the decreasing numerical parameters, and the mass-movement process is finished more quickly using low-value parameters. The deposition area of the sliding masses decreases with the increasing numerical parameters and the corresponding deposition thickness increases. The mass movement of the debris avalanche is not only influenced by the mechanical parameters but is also controlled by the topographical conditions.

  16. Triple SV: A Bit Level Symmetric Block-Cipher Having High Avalanche Effect

    Directory of Open Access Journals (Sweden)

    Rajdeep Chakraborty

    2011-08-01

    Full Text Available The prolific growth of network communication system entails high risk of breach in information security. This substantiates the need for higher security for electronic information. Cryptography is one of the ways to secure electronic documents. In this paper, we propose a new block cipher, TRIPLE SV (3SV, with 256-bit block size and 112-bit key length. Generally, stream ciphers produce higher avalanche effect but Triple SV shows a substantial rise in avalanche effect with a block cipher implementation. The CBC mode has been used to attain higher avalanche effect. The technique is implemented in C language and has been tested for feasibility

  17. A new hierarchy of avalanches observed in Bak-Sneppen evolution model

    OpenAIRE

    Li, W; Cai, X.

    1999-01-01

    A new quantity, average fitness, is introduced in Bak-Sneppen evolution model. Through this new quantity, a new hierarchy of avalanches is observed in the evolution of Bak-Sneppen model. An exact gap equation, governing the self-organization of the model, is presented. It is found that the self-organized threshold of the new quantity can be exactly obtained. Two basic exponents, avalanche distribution and avalanche dimension are given through simulations of one- and two-dimensional Bak-Sneppe...

  18. Bounds for avalanche critical values of the Bak-Sneppen model

    OpenAIRE

    Gillett, Alexis; Meester, Ronald; Nuyens, Misja

    2005-01-01

    We study the Bak-Sneppen model on locally finite transitive graphs $G$, in particular on Z^d and on T_Delta, the regular tree with common degree Delta. We show that the avalanches of the Bak-Sneppen model dominate independent site percolation, in a sense to be made precise. Since avalanches of the Bak-Sneppen model are dominated by a simple branching process, this yields upper and lower bounds for the so-called avalanche critical value $p_c^{BS}(G)$. Our main results imply that 1/(Delta+1)

  19. Avalanche transmission and critical behaviour in load-bearing hierarchical networks

    Indian Academy of Sciences (India)

    Ajay Deep Kachhvah; Neelima Gupte

    2011-11-01

    The strength and stability properties of hierarchical load-bearing networks and their strengthened variants have been discussed in a recent work. Here, we study the avalanche time distributions on these load-bearing networks. The avalanche time distributions of the V-lattice, a unique realization of the networks, show power-law behaviour when tested with certain fractions of its trunk weights. All other avalanche distributions show Gaussian peaked behaviour. Thus the V-lattice is the critical case of the network. We discuss the implications of this result.

  20. Motion of current filaments in avalanching PIN diodes

    Institute of Scientific and Technical Information of China (English)

    Ren Xingrong; Chai Changchun; Ma Zhenyang; Yang Yintang; Qiao Liping; Shi Chunlei; Ren Lihua

    2013-01-01

    The motion of current filaments in avalanching PIN diodes has been investigated in this paper by 2D transient numerical simulations.The simulation results show that the filament can move along the length of the PIN diode back and forth when the self-heating effect is considered.The voltage waveform varies periodically due to the motion of the filament.The filament motion is driven by the temperature gradient in the filament due to the negative temperature dependence of the impact ionization rates.Contrary to the traditional understanding that current filamentation is a potential cause of thermal destruction,it is shown in this paper that the thermally-driven motion of current filaments leads to the homogenization of temperature in the diode and is expected to have a positive influence on the failure threshold of the PIN diode.

  1. 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.

  2. Self-aligned multi-channel superconducting nanowire avalanche photodetector

    CERN Document Server

    Cheng, Risheng; Ma, Xiaosong; Fan, Linran; Fong, King Y; Poot, Menno; Tang, Hong X

    2016-01-01

    We describe a micromachining process to allow the coupling of an array of single-mode telecommunication fibers to individual superconducting nanowire single photon detectors (SNSPDs). As proof of principle, we show the integration of four detectors on the same silicon chip, including two standard single-section nanowire detectors and two superconducting nanowire avalanche photodetectors (SNAPs) with modified series structure without external inductor, and their performances are compared. The SNAP shows saturated system detection efficiency of 16% while the dark count rate is less than 20 Hz, without the use of photon-recycling reflectors. The SNAP also demonstrates doubled signal-to-noise ratio, reduced reset time (~ 4.9 ns decay time) and improved timing jitter (62 ps FWHM) compared to standard SNSPDs.

  3. Submicron Plasticity: Yield Stress, Dislocation Avalanches, and Velocity Distribution

    Science.gov (United States)

    Ispánovity, Péter Dusán; Groma, István; Györgyi, Géza; Csikor, Ferenc F.; Weygand, Daniel

    2010-08-01

    The existence of a well-defined yield stress, where a macroscopic crystal begins to plastically flow, has been a basic observation in materials science. In contrast with macroscopic samples, in microcrystals the strain accumulates in random bursts, which makes controlled plastic formation difficult. Here we study by 2D and 3D simulations the plastic deformation of submicron objects under increasing stress. We show that, while the stress-strain relation of individual samples exhibits jumps, its average and mean deviation still specify a well-defined critical stress. The statistical background of this phenomenon is analyzed through the velocity distribution of dislocations, revealing a universal cubic decay and the appearance of a shoulder due to dislocation avalanches.

  4. Sixteen-year follow-up of childhood avalanche survivors

    Directory of Open Access Journals (Sweden)

    Edda Bjork Thordardottir

    2016-08-01

    Full Text Available Background: Every year a substantial number of children are affected by natural disasters worldwide. However, data are scarce on long-term psychological impact of natural disasters on children's health. Identifying risk factors and outcomes associated with the long-term sequelae of posttraumatic stress disorder (PTSD can provide a gateway to recovery as well as enhancement of preventive measures. Objective: Among childhood avalanche survivors, we aimed to investigate risk factors for PTSD symptoms and the relationship between socioeconomic status (SES and PTSD symptoms in adulthood. Methods: Childhood survivors (aged 2–19 at the time of exposure of two avalanches were identified through nationwide registers 16 years later. The Posttraumatic Diagnostic Scale was used to assess current PTSD symptoms. One-way ANOVA was used to explore PTSD symptoms by background and trauma-specific factors, as well as associations with current SES. Predictors of PTSD symptoms were examined by multivariable regression analysis. Results: Response rate was 66% (108/163. Results from univariate ANOVA analysis revealed that female sex was associated with PTSD symptoms (F=5.96, p<0.05. When adjusted for age and sex, PTSD symptoms were associated with lower education (F=7.62, p<0.001, poor financial status (F=12.21, p<0.001, and unemployment and/or disability (F=3.04, p<0.05. In a multivariable regression model, when adjusting for age and sex, lack of social support (t=4.22, p<0.001 and traumatic reactions of caregivers (t=2.49, p<0.05 in the aftermath of the disaster independently predicted PTSD 16 years post-trauma. Conclusions: Lingering PTSD symptoms after childhood exposure to a disaster may negatively influence socioeconomic development in adulthood. Strengthening children's support systems post-disaster may prevent the long-term sequelae of symptoms.

  5. Gravitational wet-avalanche pressure on pylon-like structures

    Science.gov (United States)

    Sovilla, Betty; Faug, Thierry; Köhler, Anselm; Baroudi, Djebar; Fischer, Jan-Thomas; Thibert, Emmanuel

    2016-04-01

    Low-speed wet-avalanches exert hydrostatic forces on structures which are surface-dependent, however neither the pressure amplification experienced by smaller structure has been quantified and the causes of the amplification understood. In particular, recent wet-snow avalanche pressure measurements, performed with small cells at the "Vallée the la Sionne" test site, indicate significantly higher pressures than those considered by engineering guidelines and common practice rules based only on the contribution of inertial forces. In order to gain a deeper understanding and investigate the relevance of these measurements for structural design, we analyze data collected at the "Vallée the la Sionne" on obstacles of different shapes and dimensions. We show that, the pressure measured on a 1 m2 pressure plate is, on average, 1.8 times smaller than the pressure measured on a 0.008 m2 piezoelectric cell, installed on a 0.60 m wide pylon, and 2.9 times smaller than the pressure measured on a 0.0125 m2 cantilever sensor, extending freely into the snow. The different pressures encountered by the different obstacles is quantitatively explained with a granular force model, assuming the formation of a mobilized volume of snow granules extending from the obstacle upstream. The results underscore the fundamental influence of the dimension of the sensor and the obstacle on pressures. Our study highlights the difficulties that appear in the estimation of forces in the gravitational flow regime, for which force amplification may be caused by this mobilized volume at the scale of the whole structure, but also by plastic wedges, or small dead zones, at the scale of the sensor mounted on a wider structure.

  6. An InP/Si heterojunction photodiode fabricated by self-aligned corrugated epitaxial lateral overgrowth

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Y. T., E-mail: yasun@kth.se; Omanakuttan, G.; Lourdudoss, S. [Laboratory of Semiconductor Materials, Department of Materials and Nano Physics, School of Information and Communication Technology, KTH-Royal Institute of Technology, Electrum 229, Kista S-164 40 (Sweden)

    2015-05-25

    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{sup 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{sup 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.

  7. Video-speed detection of the absolute position of a light point on a large-area photodetector based on luminescent waveguides.

    Science.gov (United States)

    Koeppe, Robert; Neulinger, Anton; Bartu, Petr; Bauer, S

    2010-02-01

    A large-area photosensor is presented that uses the coupling of light into the planar waveguide mode of a polycarbonate foil by luminescent dyes to extend the active area of silicon photodiodes attached to the surface of the foil in a regular pattern. The photodiode signal is directly related to the distance between the point where light is coupled into the foil and the photodiode, thus enabling a precise recovery of the position of a localized light signal hitting the foil. We present a large-area device that can trace the movement of a light point generated by a laser pointer hitting its surface. PMID:20174049

  8. Landslides and glacier fall - ice/debris avalanches triggered by the April 2015 Gorkha Earthquake, Nepal

    Science.gov (United States)

    Fukuoka, Hiroshi; Bhandari, Netra Prakash; Adhikari, Basanta Raj; Yamasaki, Shintaro

    2016-04-01

    On 25 April 2015, a large-scale earthquake of M7.8 attacked central Nepal. Epicenter is located in Gorkha, west of Kathmandu. Aftershocks epicenter area extended about 100 km long and 150 km wide. Acceleration records inside Kathmandu basin show that the main shock predominant period is 3 - 5 s and PGA is smaller than 0.2 g, because of underneath thick deposits. Japanese expert investigation team dispatched immediately after the quake found numerous small- to large-scale landslides in the earthquake fault rupture zone except Kathmandu basin. Those characteristics are (1) number of larger landslides are much smaller than expected from the main shock magnitude, (2) uncountable rock falls were observed which claimed casualties in the mountain communities; (3) as many landslides were reactivated since the main/after-shock area are occupied by landslide-prone hill slopes; (4) some large-scale rock slides resulting in landslide dam creation, were confirmed by the immediate satellite imagery analysis; (5) In the Langtang village in Himalaya mountains, an hanging glacier fall - ice/debris avalanche was triggered, claiming the lives of all the residents and trekkers staying in the community. Authors had returned debris sample to Japan, trying to apply geotechnical tests for mechanism study; (6) subsidence sites along the highway of artificial fills and adjacent communities of Kathmandu were observed; (7) Small-scale landslides and subsidence were observed in some of UNESCO's World heritage sites.

  9. Extended Wavelength InP Based Avalanche Diodes for MWIR Response Project

    Data.gov (United States)

    National Aeronautics and Space Administration — For this NASA STTR program, we propose to develop a novel superlattice-based near infrared to midwave infrared avalanche photodetector (APD) grown on InP substrates...

  10. 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

    2012-08-24

    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. PMID:23002751

  11. Prediction of picosecond voltage collapse and electromagnetic wave generation in gas avalanche switches

    International Nuclear Information System (INIS)

    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

  12. 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.

  13. Loading-rate-independent delay of catastrophic avalanches in a bulk metallic glass

    Science.gov (United States)

    Chen, S. H.; Chan, K. C.; Wang, G.; Wu, F. F.; Xia, L.; Ren, J. L.; Li, J.; Dahmen, K. A.; Liaw, P. K.

    2016-02-01

    The plastic flow of bulk metallic glasses (BMGs) is characterized by intermittent bursts of avalanches, and this trend results in disastrous failures of BMGs. In the present work, a double-side-notched BMG specimen is designed, which exhibits chaotic plastic flows consisting of several catastrophic avalanches under the applied loading. The disastrous shear avalanches have, then, been delayed by forming a stable plastic-flow stage in the specimens with tailored distances between the bottoms of the notches, where the distribution of a complex stress field is acquired. Differing from the conventional compressive testing results, such a delaying process is independent of loading rate. The statistical analysis shows that in the specimens with delayed catastrophic failures, the plastic flow can evolve to a critical dynamics, making the catastrophic failure more predictable than the ones with chaotic plastic flows. The findings are of significance in understanding the plastic-flow mechanisms in BMGs and controlling the avalanches in relating solids.

  14. Avalanche criticality during compression of porcine cortical bone of different ages

    Science.gov (United States)

    Baró, Jordi; Shyu, Peter; Pang, Siyuan; Jasiuk, Iwona M.; Vives, Eduard; Salje, Ekhard K. H.; Planes, Antoni

    2016-05-01

    Crack events developed during uniaxial compression of cortical bones cut from femurs of developing pigs of several ages (4, 12, and 20 weeks) generate avalanches. These avalanches have been investigated by acoustic emission analysis techniques. The avalanche energies are power-law distributed over more than four decades. Such behavior indicates the absence of characteristic scales and suggests avalanche criticality. The statistical distributions of energies and waiting times depend on the pig age and indicate that bones become stronger, but less ductile, with increasing age. Crack propagation is equally age-dependent. Older pigs show, on average, larger cracks with a time distribution similar to those of aftershocks in earthquakes, while younger pigs show only statistically independent failure events.

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

    Institute of Scientific and Technical Information of China (English)

    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.

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

    Science.gov (United States)

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

    2013-03-01

    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.

  17. Some influences of rock strength and strain rate on propagation of rock avalanches

    Science.gov (United States)

    Bowman, Elisabeth; Rait, Kim

    2016-04-01

    Rock avalanches are extreme and destructive mass movements in which large volumes of rock (typically >1 million cubic metres) travel at high speeds, covering large distances, and the occurrence of which is highly unpredictable. The "size effect" in rock avalanches, whereby those with larger volumes produce greater spreading efficiency (as defined by an increase in normalised runout) or lower farboschung angle (defined as the tangent of the ratio of fall height to runout length), is well known. Studies have shown that rock strength is a controlling factor in the mobility of rock avalanches - that is, mass movements involving lower strength rock are generally found to produce greater mobility as evidenced by the spread of deposits or low farboschung angle. However, there are conflicting ideas as to how and why this influence is manifested. This paper discusses different theories of rock comminution in light of numerical simulations of rock clasts undergoing normal and shear induced loading, experimental work on rock avalanche behaviour, and dynamic fracture mechanics. In doing so, we introduce the idea of thresholds of strain rate for the production of dynamic fragmentation (as opposed to pseudo-static clast crushing) that are based, inter alia, on static rock strength. To do this, we refer to data from physical models using rock analogue materials, field data on chalk cliff collapses, and field statistics from documented rock avalanches. The roles of normal and shear loading and loading rate within a rock avalanche are examined numerically using 3D Discrete Element Method models of rock clasts loaded to failure. Results may help to reconcile the observations that large rock avalanches in stronger materials tend not to fragment as much as those in weaker materials and also possess lower mobility, while small cliff collapses (typically > 1000 cubic metres) in weak chalk can exhibit rock avalanche-like behaviour at much smaller volumes.

  18. High pressure pulsed avalanche discharges: Scaling of required preionization rate for homogeneity

    International Nuclear Information System (INIS)

    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 Nst.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 Nst.p ∝ p21/4τ-3/4. This pressure scaling disagrees with the p3/2 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 ne of free electrons becomes larger than the density Nst.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

  19. Exact equqations and scaling relations for f-avalanche in the Bak-Sneppen evolution model

    OpenAIRE

    Li, W; Cai, X.

    2000-01-01

    Infinite hierarchy of exact equations are derived for the newly-observed f-avalanche in the Bak-Sneppen evolution model. By solving the first order exact equation, we found that the critical exponent which governs the divergence of the average avalanche size, is exactly 1 (for all dimensions), confirmed by the simulations. Solution of the gap equation yields another universal exponent, denoting the the relaxation to the attractor, is exactly 1. We also establish some scaling relations among t...

  20. Mean Field Theory of Sandpile Avalanches: from the Intermittent to the Continuous Flow Regime

    OpenAIRE

    Benza, V. G.; Nori, Franco; Pla, Oscar

    1993-01-01

    We model the dynamics of avalanches in granular assemblies in partly filled rotating cylinders using a mean-field approach. We show that, upon varying the cylinder angular velocity $\\omega$, the system undergoes a hysteresis cycle between an intermittent and a continuous flow regimes. In the intermittent flow regime, and approaching the transition, the avalanche duration exhibits critical slowing down with a temporal power-law divergence. Upon adding a white noise term, and close to the trans...