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Sample records for pixelated cdznte drift

  1. Pixelated CdZnTe drift detectors

    DEFF Research Database (Denmark)

    Kuvvetli, Irfan; Budtz-Jørgensen, Carl

    2005-01-01

    A technique, the so-called Drift Strip Method (DSM), for improving the CdZnTe detector energy response to hard X-rays and gamma-rays was applied as a pixel geometry. First tests have confirmed that this detector type provides excellent energy resolution and imaging performance. We specifically...... report on the performance of 3 mm thick prototype CZT drift pixel detectors fabricated using material from eV-products. We discuss issues associated with detector module performance. Characterization results obtained from several prototype drift pixel detectors are presented. Results of position...

  2. Leakage current measurements on pixelated CdZnTe detectors

    NARCIS (Netherlands)

    Dirks, B.P.F.; Blondel, C.; Daly, F.; Gevin, O.; Limousin, O.; Lugiez, F.

    2006-01-01

    In the field of the R&D of a new generation hard X-ray cameras for space applications we focus on the use of pixelated CdTe or CdZnTe semiconductor detectors. They are covered with 64 (0.9×0.9 mm2) or 256 (0.5×0.5 mm2) pixels, surrounded by a guard ring and operate in the energy ranging from several

  3. Fast Neutron Detection Using Pixelated CdZnTe Spectrometers

    Science.gov (United States)

    Streicher, Michael; Goodman, David; Zhu, Yuefeng; Brown, Steven; Kiff, Scott; He, Zhong

    2017-07-01

    Fast neutrons are an important signature of special nuclear materials (SNMs). They have a low natural background rate and readily penetrate high atomic number materials that easily shield gamma-ray signatures. Therefore, they provide a complementary signal to gamma rays for detecting shielded SNM. Scattering kinematics dictate that a large nucleus (such as Cd or Te) will recoil with small kinetic energy after an elastic collision with a fast neutron. Charge carrier recombination and quenching further reduce the recorded energy deposited. Thus, the energy threshold of CdZnTe detectors must be very low in order to sense the small signals from these recoils. In this paper, the threshold was reduced to less than 5 keVee to demonstrate that the 5.9-keV X-ray line from 55Fe could be separated from electronic noise. Elastic scattering neutron interactions were observed as small energy depositions (less than 20 keVee) using digitally sampled pulse waveforms from pixelated CdZnTe detectors. Characteristic gamma-ray lines from inelastic neutron scattering were also observed.

  4. Performance updating of CdZnTe strip-drift detectors

    DEFF Research Database (Denmark)

    Shorohov, M.; Tsirkunova, I.; Loupilov, A.;

    2007-01-01

    59.6 and 662 keV correspondingly. Recently, significant progress was done in CdZnTe crystals growth technology. In the present paper we present preliminary result of performance updating of CdZnTe strip-drift detectors based on crystal of 10 x 10 x 6 mm 3 produced by Yinnel Tech company. Results...

  5. Signal modeling of charge sharing effect in simple pixelated CdZnTe detector

    Science.gov (United States)

    Kim, Jae Cheon; Kaye, William R.; He, Zhong

    2014-05-01

    In order to study the energy resolution degradation in 3D position-sensitive pixelated CdZnTe (CZT) detectors, a detailed detector system modeling package has been developed and used to analyze the detector performance. A 20 × 20 × 15 mm3 CZT crystal with an 11 × 11 simple-pixel anode array and a 1.72 mm pixel pitch was modeled. The VAS UM/TAT4 Application Specific Integrated Circuitry (ASIC) was used for signal read-out. Components of the simulation package include gamma-ray interactions with the CZT crystal, charge induction, electronic noise, pulse shaping, and ASIC triggering procedures. The charge induction model considers charge drift, trapping, diffusion, and sharing between pixels. This system model is used to determine the effects of electron cloud sharing, weighting potential non-uniformity, and weighting potential cross-talk which produce non-uniform signal responses for different gamma-ray interaction positions and ultimately degrade energy resolution. The effect of the decreased weighting potential underneath the gap between pixels on the total pulse amplitude of events has been studied. The transient signals induced by electron clouds collected near the gap between pixels may generate false signals, and the measured amplitude can be even greater than the photopeak. As the number of pixels that collect charge increases, the probability of side-neighbor events due to charge sharing significantly increases. If side-neighbor events are not corrected appropriately, the energy resolution of pixelated CZT detectors in multiple-pixel events degrades rapidly.

  6. Signal modeling of charge sharing effect in simple pixelated CdZnTe detector

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jae C.; Kaye, William R.; He, Zhong [University of Michigan, Ann Arbor, MI (United States)

    2014-05-15

    In order to study the energy resolution degradation in 3D position-sensitive pixelated CdZnTe (CZT) detectors, a detailed detector system modeling package has been developed and used to analyze the detector performance. A 20 x 20 x 15 mm{sup 3} CZT crystal with an 11 x 11 simple-pixel anode array and a 1.72 mm pixel pitch was modeled. The VAS UM/TAT4 Application Specific Integrated Circuitry (ASIC) was used for signal read-out. Components of the simulation package include gamma-ray interactions with the CZT crystal, charge induction, electronic noise, pulse shaping, and ASIC triggering procedures. The charge induction model considers charge drift, trapping, diffusion, and sharing between pixels. This system model is used to determine the effects of electron cloud sharing, weighting potential non-uniformity, and weighting potential cross-talk which produce non-uniform signal responses for different gamma-ray interaction positions and ultimately degrade energy resolution. The effect of the decreased weighting potential underneath the gap between pixels on the total pulse amplitude of events has been studied. The transient signals induced by electron clouds collected near the gap between pixels may generate false signals, and the measured amplitude can be even greater than the photopeak. As the number of pixels that collect charge increases, the probability of side-neighbor events due to charge sharing significantly increases. If side-neighbor events are not corrected appropriately, the energy resolution of pixelated CZT detectors in multiple-pixel events degrades rapidly.

  7. A highly pixelated CdZnTe detector based on \\textit{Topmetal-${II}^-$} sensor

    CERN Document Server

    Zou, Shuguang; Sun, Xiangming; Huang, Guangming; Pei, Hua; Wang, Zhen; Liu, Jun; Yang, Ping; Wang, Dong

    2016-01-01

    \\textit{Topmetal-${II}^-$} is a low noise CMOS pixel direct charge sensor with a pitch of 83$\\mu m$. CdZnTe is an excellent semiconductor material for radiation detection. The combination of CdZnTe and the sensor makes it possible to build a detector with high spatial resolution. In our experiments, an epoxy adhesive is used as the conductive medium to connect the sensor and CdZnTe. The diffusion coefficient and charge efficiency of electrons are measured at a low bias voltage of -2 Volts, and the image of a single alpha is clear with a reasonable spatial resolution. The detector of such structure has the potential to be applied in X-ray imaging systems with a further improvements of the sensor.

  8. The development of drift-strip detectors based on CdZnTe

    DEFF Research Database (Denmark)

    Gostilo, V.; Budtz-Jørgensen, Carl; Kuvvetli, Irfan

    2002-01-01

    The design and technological development of a CdZnTe drift strip detector is described. The device is based on a monocrystal of dimensions 10 x 10 x 3 mm(3) and has a pitch of 200 mum and a strip width of 100 mum. The strip length is 9.5 mm. The distribution of the leakage currents of the strips...

  9. Hard x-ray response of pixellated CdZnTe detectors

    Science.gov (United States)

    Abbene, L.; Del Sordo, S.; Caroli, E.; Gerardi, G.; Raso, G.; Caccia, S.; Bertuccio, G.

    2009-06-01

    In recent years, the development of cadmium zinc telluride (CdZnTe) detectors for x-ray and gamma ray spectrometry has grown rapidly. The good room temperature performance and the high spatial resolution of pixellated CdZnTe detectors make them very attractive in space-borne x-ray astronomy, mainly as focal plane detectors for the new generation of hard x-ray focusing telescopes. In this work, we investigated on the spectroscopic performance of two pixellated CdZnTe detectors coupled with a custom low noise and low power readout application specific integrated circuit (ASIC). The detectors (10×10×1 and 10×10×2 mm3 single crystals) have an anode layout based on an array of 256 pixels with a geometric pitch of 0.5 mm. The ASIC, fabricated in 0.8 μm BiCMOS technology, is equipped with eight independent channels (preamplifier and shaper) and characterized by low power consumption (0.5 mW/channel) and low noise (150-500 electrons rms). The spectroscopic results point out the good energy resolution of both detectors at room temperature [5.8% full width at half maximum (FWHM) at 59.5 keV for the 1 mm thick detector; 5.5% FWHM at 59.5 keV for the 2 mm thick detector) and low tailing in the measured spectra, confirming the single charge carrier sensing properties of the CdZnTe detectors equipped with a pixellated anode layout. Temperature measurements show optimum performance of the system (detector and electronics) at T =10 °C and performance degradation at lower temperatures. The detectors and the ASIC were developed by our collaboration as two small focal plane detector prototypes for hard x-ray multilayer telescopes operating in the 20-70 keV energy range.

  10. CdZnTe position-sensitive drift detectors with thicknesses up to 5 cm

    Science.gov (United States)

    Bolotnikov, A. E.; Camarda, G. S.; Chen, E.; Cheng, S.; Cui, Y.; Gul, R.; Gallagher, R.; Dedic, V.; De Geronimo, G.; Ocampo Giraldo, L.; Fried, J.; Hossain, A.; MacKenzie, J. M.; Sellin, P.; Taherion, S.; Vernon, E.; Yang, G.; El-hanany, U.; James, R. B.

    2016-02-01

    We investigated the feasibility of long-drift-time CdZnTe (CZT) gamma-ray detectors, fabricated from CZT material produced by Redlen Technologies. CZT crystals with cross-section areas of 5 × 5 mm2 and 6 × 6 mm2 and thicknesses of 20-, 30-, 40-, and 50-mm were configured as 3D position-sensitive drift detectors and were read out using a front-end ASIC. By correcting the electron charge losses caused by defects in the crystals, we demonstrated high performance for relatively thick detectors fabricated from unselected CZT material.

  11. CdZnTe position-sensitive drift detectors with thicknesses up to 5 cm

    OpenAIRE

    Bolotnikov, AE; Camarda, GS; Chen, E.; Cheng, S.; Cui, Y.; Gul, R; Gallagher, R; Dedic, V.; De Geronimo, G.; Giraldo, LO; Fried, J.; Hossain, A; MacKenzie, JM; Sellin, P.; Taherion, S

    2016-01-01

    We investigated the feasibility of long-drift-time CdZnTe (CZT) gamma-ray detectors, fabricated from CZT material produced by Redlen Technologies. CZT crystals with cross-section areas of 5 5 mm2 and 6 6 mm2 and thicknesses of 20-, 30-, 40-, and 50-mm were configured as 3D position-sensitive drift detectors and were read out using a front-end ASIC. By correcting the electron charge losses caused by defects in the crystals, we demonstrated high performance for relatively thick detectors fabric...

  12. CMOS Pixel Spectroscopic Circuits for Cd(ZnTe Gamma Ray Imagers

    Directory of Open Access Journals (Sweden)

    Hatzistratis D.

    2016-01-01

    Full Text Available A family of 2-D pixel CMOS ASICs have been developed to be used as readout electronics of gamma ray imaging instruments based on hybrid pixel sensor arrays. One element of the sensor array consists of a pixilated single crystal of CdTe or CdZnTe semiconductor bump bonded to the CMOS electronic circuit. The first member of the family can process single photon signals which deliver up to 4fCb charge, while the two other can process signals up to 36fCb. A unique readout mode and the simultaneous extraction of energy and time tagging information of the converted photons differentiate the members of this family from other existing CMOS readout circuits.

  13. CdZnTe drift detector with correction for hole trapping

    DEFF Research Database (Denmark)

    van Pamelen, M.A.J.; Budtz-Jørgensen, Carl

    1998-01-01

    The results are presented of a CdZnTe drift detector for which the energy determination can be corrected for hole trapping. The electronic noise and the hole contribution to the signal are reduced and the signals are also corrected for any residual effects of hole trapping. This is achieved...... by using drift strips and an anode strip on one side of the detector crystal in combination with a single planar electrode on the other side. Below 100 keV, the resolution tin FWHM) was electronic noise limited. Using a planar electrode, the peak of Am-241 at 59.6 keV has a width of 14.1 ke...

  14. Intensifying process of polarization effect within pixellated CdZnTe detectors for X-ray imaging

    Institute of Scientific and Technical Information of China (English)

    Xi Wang; Shali Xiao; Miao Li; Liuqiang Zhang; Yulin Cao; Yuxiao Chen

    2011-01-01

    The intensifying process of polarization effect at room temperature in a pixellated Cadmium zinc telluride (CdZnTe) monolithic detector is studied.The process is attributed to the increase in build up space charges in the CdZnTe crystal,which causes an expansion of the space charge region under the irradiated area.The simulations of electric potential distributions indicate that the distorted electric potential due to the high X-ray flux is significantly changed and even deteriorated due to increasing space charges within the irradiated volume.An agreement between the space charge distribution and electric potential is discussed.

  15. Charge sharing in common-grid pixelated CdZnTe detectors

    Science.gov (United States)

    Kim, Jae Cheon; Anderson, Stephen E.; Kaye, Willy; Zhang, Feng; Zhu, Yuefeng; Kaye, Sonal Joshi; He, Zhong

    2011-10-01

    The charge sharing effect in pixelated CdZnTe (CZT) detectors with a common anode steering grid has been studied. The impact on energy resolution of weighting potential cross-talk and ballistic deficit due to cathode signal shaping has been investigated. A detailed system modeling package considering charge induction, electronic noise, pulse shaping, and ASIC triggering procedures has been developed to study the characteristics of common-grid CZT detectors coupled to the VAS_UM/TAT4 ASIC. Besides an actual common-grid CZT detector coupled to VAS_UM/TAT4 ASIC, a prototype digital read-out system has been developed to better understand the nature of the charge sharing effect.

  16. Charge sharing in common-grid pixelated CdZnTe detectors

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jae Cheon, E-mail: jaecheon@umich.edu [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI 48109 (United States); Anderson, Stephen E.; Kaye, Willy; Zhang Feng; Zhu Yuefeng; Kaye, Sonal Joshi; He Zhong [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI 48109 (United States)

    2011-10-21

    The charge sharing effect in pixelated CdZnTe (CZT) detectors with a common anode steering grid has been studied. The impact on energy resolution of weighting potential cross-talk and ballistic deficit due to cathode signal shaping has been investigated. A detailed system modeling package considering charge induction, electronic noise, pulse shaping, and ASIC triggering procedures has been developed to study the characteristics of common-grid CZT detectors coupled to the VAS{sub U}M/TAT4 ASIC. Besides an actual common-grid CZT detector coupled to VAS{sub U}M/TAT4 ASIC, a prototype digital read-out system has been developed to better understand the nature of the charge sharing effect.

  17. Development of a simplified simulation model for performance characterization of a pixellated CdZnTe multimodality imaging system

    Energy Technology Data Exchange (ETDEWEB)

    Guerra, P; Santos, A [Departamento de IngenierIa Electronica, Universidad Politecnica de Madrid, Ciudad Universitaria s/n, 28040 Madrid (Spain); Darambara, D G [Joint Department of Physics, Royal Marsden NHS Foundation Trust and The Institute of Cancer Research, Fulham Road, London SW3 6JJ (United Kingdom)], E-mail: pguerra@die.um.es

    2008-02-21

    Current requirements of molecular imaging lead to the complete integration of complementary modalities in a single hybrid imaging system to correlate function and structure. Among the various existing detector technologies, which can be implemented to integrate nuclear modalities (PET and/or single-photon emission computed tomography with x-rays (CT) and most probably with MR, pixellated wide bandgap room temperature semiconductor detectors, such as CdZnTe and/or CdTe, are promising candidates. This paper deals with the development of a simplified simulation model for pixellated semiconductor radiation detectors, as a first step towards the performance characterization of a multimodality imaging system based on CdZnTe. In particular, this work presents a simple computational model, based on a 1D approximate solution of the Schockley-Ramo theorem, and its integration into the Geant4 application for tomographic emission (GATE) platform in order to perform accurately and, therefore, improve the simulations of pixellated detectors in different configurations with a simultaneous cathode and anode pixel readout. The model presented here is successfully validated against an existing detailed finite element simulator, the multi-geometry simulation code, with respect to the charge induced at the anode, taking into consideration interpixel charge sharing and crosstalk, and to the detector charge induction efficiency. As a final point, the model provides estimated energy spectra and time resolution for {sup 57}Co and {sup 18}F sources obtained with the GATE code after the incorporation of the proposed model.

  18. Polarimetric analysis of a CdZnTe spectro-imager under multi-pixel irradiation conditions

    Science.gov (United States)

    Pinto, M.; da Silva, R. M. Curado; Maia, J. M.; Simões, N.; Marques, J.; Pereira, L.; Trindade, A. M. F.; Caroli, E.; Auricchio, N.; Stephen, J. B.; Gonçalves, P.

    2016-12-01

    So far, polarimetry in high-energy astrophysics has been insufficiently explored due to the complexity of the required detection, electronic and signal processing systems. However, its importance is today largely recognized by the astrophysical community, therefore the next generation of high-energy space instruments will certainly provide polarimetric observations, contemporaneously with spectroscopy and imaging. We have been participating in high-energy observatory proposals submitted to ESA Cosmic Vision calls, such as GRI (Gamma-Ray Imager), DUAL and ASTROGAM, where the main instrument was a spectro-imager with polarimetric capabilities. More recently, the H2020 AHEAD project was launched with the objective to promote more coherent and mature future high-energy space mission proposals. In this context of high-energy proposal development, we have tested a CdZnTe detection plane prototype polarimeter under a partially polarized gamma-ray beam generated from an aluminum target irradiated by a 22Na (511 keV) radioactive source. The polarized beam cross section was 1 cm2, allowing the irradiation of a wide multi-pixelated area where all the pixels operate simultaneously as a scatterer and as an absorber. The methods implemented to analyze such multi-pixel irradiation are similar to those required to analyze a spectro-imager polarimeter operating in space, since celestial source photons should irradiate its full pixilated area. Correction methods to mitigate systematic errors inherent to CdZnTe and to the experimental conditions were also implemented. The polarization level ( 40%) and the polarization angle (precision of ±5° up to ±9°) obtained under multi-pixel irradiation conditions are presented and compared with simulated data.

  19. 碲锌镉面元辐射探测器堆积载流子屏蔽效应%Accumulated-carrier screening effect based investigation for pixellated CdZnTe radiation detector

    Institute of Scientific and Technical Information of China (English)

    肖沙里; 黎淼; 王玺; 曹玉琳; 陈宇晓; 聂玲; 张流强

    2011-01-01

    Using the pixellated CdZnTe detector, the radiation imaging experiment for the Rh target X-ray source was accomplished. The experimental results indicate that the response signals of the anode pixels, which distribute over the center irradiated area, are completely shut-off when the tube voltage is 45 kV and the tube current increases to 20 μA. Moreover, the non-response pixel area expands with the increase of the tube current, and the total event count of the CdZnTe detector reduces obviously. Furthermore, the inner electric potential and electric field distributions of the pixellated CdZnTe detector were simulated based on the Poisson equation. The simulation results reveal that the accumulation of the hole carriers, which results from the extremely low drift ability of the hole carrier, leads to a relatively high space-charge-density area in the CdZnTe bulk when the irradiated photon flux increases to 5× 105 mm-2 · s-1. And thus, the induced signal screen effect of the anode pixels in the center irradiated area is mainly attributed to the distorted electric field which makes electron carriers drift toward the high potential area in the CdZnTe crystal instead of the pixel anodes.%采用铑(Rh)靶45 kV X射线源进行了碲锌镉(CdZnTe)面元像素阵列探测器成像实验.实验结果表明:在探测距离1 mm,管电压45 kV条件下,管电流增大至20μA时,辐照中心区域像素单元信号丢失,出现围绕辐照中心区域的边缘高事件计数环形探测图像.随着管电流的增大,无响应像素区域扩大,探测器总体事件计数明显降低.进一步根据泊松方程建立了CdZnTe晶体内部电势分布模型,仿真结果表明:单位面积光子通量为5×105 mm-2·s-1时,由于CdZnTe晶体较低的空穴迁移率,晶体内部存在堆积空穴载流子形成的高空间电荷密度分布区域.晶体内部电场产生扭曲,电子载流子无法迁移至对应阳极位置,导致辐照中心区域产生信号屏蔽效应.

  20. Performance comparison of small-pixel CdZnTe radiation detectors with gold contacts formed by sputter and electroless deposition

    Science.gov (United States)

    Bell, S. J.; Baker, M. A.; Duarte, D. D.; Schneider, A.; Seller, P.; Sellin, P. J.; Veale, M. C.; Wilson, M. D.

    2017-06-01

    Recent improvements in the growth of wide-bandgap semiconductors, such as cadmium zinc telluride (CdZnTe or CZT), has enabled spectroscopic X/γ-ray imaging detectors to be developed. These detectors have applications covering homeland security, industrial analysis, space science and medical imaging. At the Rutherford Appleton Laboratory (RAL) a promising range of spectroscopic, position sensitive, small-pixel Cd(Zn)Te detectors have been developed. The challenge now is to improve the quality of metal contacts on CdZnTe in order to meet the demanding energy and spatial resolution requirements of these applications. The choice of metal deposition method and fabrication process are of fundamental importance. Presented is a comparison of two CdZnTe detectors with contacts formed by sputter and electroless deposition. The detectors were fabricated with a 74 × 74 array of 200 μm pixels on a 250 μm pitch and bump-bonded to the HEXITEC ASIC. The X/γ-ray emissions from an 241Am source were measured to form energy spectra for comparison. It was found that the detector with contacts formed by electroless deposition produced the best uniformity and energy resolution; the best pixel produced a FWHM of 560 eV at 59.54 keV and 50% of pixels produced a FWHM better than 1.7 keV . This compared with a FWHM of 1.5 keV for the best pixel and 50% of pixels better than 4.4 keV for the detector with sputtered contacts.

  1. Effects of bulk and surface conductivity on the performance of CdZnTe pixel detectors

    DEFF Research Database (Denmark)

    Bolotnikov, A.E.; Chen, C.M.H.; Cook, W.R.;

    2002-01-01

    between the pixel contacts. When the grid is negatively biased, the strong electric field in the gaps between the pixels forces the electrons landing on the surface to move toward the contacts, preventing the charge loss. We have investigated these effects by using CZT pixel detectors indium bump...

  2. Using the TOF method to measure the electron lifetime in long-drift CdZnTe detectors (Conference Presentation)

    Science.gov (United States)

    Bolotnikov, Aleksey E.; Camarda, Giuseppe S.; Chen, Eric; Cui, Yonggang; Gul, Rubi; Dedic, Václav; De Geronimo, Gianluigi; Fried, Jack; Hossain, Anwar; MacKenzie, Jason M.; Sellin, Paul; Taherion, Saeid; Vernon, Emerson; Yang, Ge; El-hanany, Uri; James, Ralph B.

    2016-09-01

    The traditional method for electron lifetime measurements of CdZnTe (CZT) detectors relies on using the Hecht equation. The procedure involves measuring the dependence of the detector response on the applied bias and applying the Hecht equation to evaluate the mu-tau product, which in turn can be converted into the carrier lifetime if the mobility is known. Despite general acceptance of this technique, which is very convenient for comparative testing of different CZT materials, the assumption of a constant electric field inside a detector is unjustified. In the Hecht equation, this assumption means that the drift time would be a linear function of the drift distance. This condition is rarely fulfilled in practice at low applied biases where the Hecht equation is most sensitive to the mu-tau product. As a result, researchers usually take measurements at relatively high biases, which work well in the case of the low mu-tau material, Technologies. The TOF-based techniques are traditionally used for monitoring the electronegative impurity concentrations in noble gas detectors by measuring the electron lifetimes. We found the electron mu-tau product of tested crystals is in the range 0.1-0.2 cm2/V, which is an order of the magnitude higher than any value previously reported for CZT material. In this work, we reported the measurement procedure and the results. We will also discuss the applicability criteria of the Hecht equation for measuring the electron lifetime in high mu-tau product CZT.

  3. Optimal configuration of a low-dose breast-specific gamma camera based on semiconductor CdZnTe pixelated detectors

    Science.gov (United States)

    Genocchi, B.; Pickford Scienti, O.; Darambara, DG

    2017-05-01

    Breast cancer is one of the most frequent tumours in women. During the ‘90s, the introduction of screening programmes allowed the detection of cancer before the palpable stage, reducing its mortality up to 50%. About 50% of the women aged between 30 and 50 years present dense breast parenchyma. This percentage decreases to 30% for women between 50 to 80 years. In these women, mammography has a sensitivity of around 30%, and small tumours are covered by the dense parenchyma and missed in the mammogram. Interestingly, breast-specific gamma-cameras based on semiconductor CdZnTe detectors have shown to be of great interest to early diagnosis. Infact, due to the high energy, spatial resolution, and high sensitivity of CdZnTe, molecular breast imaging has been shown to have a sensitivity of about 90% independently of the breast parenchyma. The aim of this work is to determine the optimal combination of the detector pixel size, hole shape, and collimator material in a low dose dual head breast specific gamma camera based on a CdZnTe pixelated detector at 140 keV, in order to achieve high count rate, and the best possible image spatial resolution. The optimal combination has been studied by modeling the system using the Monte Carlo code GATE. Six different pixel sizes from 0.85 mm to 1.6 mm, two hole shapes, hexagonal and square, and two different collimator materials, lead and tungsten were considered. It was demonstrated that the camera achieved higher count rates, and better signal-to-noise ratio when equipped with square hole, and large pixels (> 1.3 mm). In these configurations, the spatial resolution was worse than using small pixel sizes (< 1.3 mm), but remained under 3.6 mm in all cases.

  4. Use of high-granularity CdZnTe pixelated detectors to correct response non-uniformities caused by defects in crystals

    Energy Technology Data Exchange (ETDEWEB)

    Bolotnikov, A.E., E-mail: bolotnik@bnl.gov [Brookhaven National Laboratory, Upton, NY 11793 (United States); Camarda, G.S.; Cui, Y.; De Geronimo, G. [Brookhaven National Laboratory, Upton, NY 11793 (United States); Eger, J.; Emerick, A. [eV Products Inc., Saxonburg, PA 16056 (United States); Fried, J.; Hossain, A.; Roy, U.; Salwen, C. [Brookhaven National Laboratory, Upton, NY 11793 (United States); Soldner, S. [eV Products Inc., Saxonburg, PA 16056 (United States); Vernon, E.; Yang, G.; James, R.B. [Brookhaven National Laboratory, Upton, NY 11793 (United States)

    2016-01-01

    Following our successful demonstration of the position-sensitive virtual Frisch-grid detectors, we investigated the feasibility of using high-granularity position sensing to correct response non-uniformities caused by the crystal defects in CdZnTe (CZT) pixelated detectors. The development of high-granularity detectors able to correct response non-uniformities on a scale comparable to the size of electron clouds opens the opportunity of using unselected off-the-shelf CZT material, whilst still assuring high spectral resolution for the majority of the detectors fabricated from an ingot. Here, we present the results from testing 3D position-sensitive 15×15×10 mm{sup 3} pixelated detectors, fabricated with conventional pixel patterns with progressively smaller pixel sizes: 1.4, 0.8, and 0.5 mm. We employed the readout system based on the H3D front-end multi-channel ASIC developed by BNL's Instrumentation Division in collaboration with the University of Michigan. We use the sharing of electron clouds among several adjacent pixels to measure locations of interaction points with sub-pixel resolution. By using the detectors with small-pixel sizes and a high probability of the charge-sharing events, we were able to improve their spectral resolutions in comparison to the baseline levels, measured for the 1.4-mm pixel size detectors with small fractions of charge-sharing events. These results demonstrate that further enhancement of the performance of CZT pixelated detectors and reduction of costs are possible by using high spatial-resolution position information of interaction points to correct the small-scale response non-uniformities caused by crystal defects present in most devices. - Highlights: • We investigated performances of 3D position sensitive CdZnTe pixelated detectors. • We employed the readout electronics based on H3D ASIC and data processing. • We demonstrated the feasibility of correcting response nonuniformities in CdZnTe pixelated detectors.

  5. Use of the drift-time method to measure the electron lifetime in long-drift-length CdZnTe detectors

    Science.gov (United States)

    Bolotnikov, A. E.; Camarda, G. S.; Chen, E.; Gul, R.; Dedic, V.; De Geronimo, G.; Fried, J.; Hossain, A.; MacKenzie, J. M.; Ocampo, L.; Sellin, P.; Taherion, S.; Vernon, E.; Yang, G.; El-Hanany, U.; James, R. B.

    2016-09-01

    The traditional method for electron lifetime measurements of CdZnTe (CZT) detectors relies on using the Hecht equation. The procedure involves measuring the dependence of the detector response on the applied bias to evaluate the μτ product, which in turn can be converted into the carrier lifetime. Despite general acceptance of this technique, which is very convenient for comparative testing of different CZT materials, the assumption of a constant electric field inside a detector is unjustified. In the Hecht equation, this assumption means that the drift time would be a linear function of the distance. This condition is not fulfilled in practice at low applied biases, where the Hecht equation is most sensitive to the μτ product. As a result, researchers usually take measurements at relatively high biases, which work well in the case of the low μτ-product material, grade CZT detectors produced by the Redlen Technologies. We found that the electron μτ product of tested crystals is in the range 0.1-0.2 cm2/V, which is an order of the magnitude higher than any value previously reported for a CZT material. In comparison, using the Hecht equation fitting, we obtained μτ = 2.3 × 10-2 cm2/V for a 2-mm thin planar detector fabricated from the same CZT material.

  6. Preliminary test results of a new high-energy-resolution silicon and CdZnTe pixel detectors for application to x-ray astronomy

    Science.gov (United States)

    Sushkov, V. V.; Hamilton, William J.; Hurley, Kevin; Maeding, Dale G.; Ogelman, Hakki; Paulos, Robert J.; Puetter, Richard C.; Tumer, Tumay O.; Zweerink, Jeffrey

    1999-10-01

    New, high spatial resolution CdZnTe (CZT) and silicon (Si) pixel detectors are highly suitable for x-ray astronomy. These detectors are planned for use in wide field of view, imaging x-ray, and low energy gamma-ray all-sky monitor (AXGAM) in a future space mission. The high stopping power of CZT detectors combined with low-noise front-end readout makes possible an order of magnitude improvement in spatial and energy resolution in x-ray detection. The AXGAM instrument will be built in the form of a fine coded aperture placed over two-dimensional, high spatial resolution and low energy threshold CZT pixel detector array. The preliminary result of CZT and silicon pixel detector test with low-noise readout electronics system are presented. These detectors may also be used with or without modification for medical and industrial imaging.

  7. Use of high-granularity CdZnTe pixelated detectors to correct response non-uniformities caused by defects in crystals

    Science.gov (United States)

    Bolotnikov, A. E.; Camarda, G. S.; Cui, Y.; De Geronimo, G.; Eger, J.; Emerick, A.; Fried, J.; Hossain, A.; Roy, U.; Salwen, C.; Soldner, S.; Vernon, E.; Yang, G.; James, R. B.

    2016-01-01

    Following our successful demonstration of the position-sensitive virtual Frisch-grid detectors, we investigated the feasibility of using high-granularity position sensing to correct response non-uniformities caused by the crystal defects in CdZnTe (CZT) pixelated detectors. The development of high-granularity detectors able to correct response non-uniformities on a scale comparable to the size of electron clouds opens the opportunity of using unselected off-the-shelf CZT material, whilst still assuring high spectral resolution for the majority of the detectors fabricated from an ingot. Here, we present the results from testing 3D position-sensitive 15×15×10 mm3 pixelated detectors, fabricated with conventional pixel patterns with progressively smaller pixel sizes: 1.4, 0.8, and 0.5 mm. We employed the readout system based on the H3D front-end multi-channel ASIC developed by BNL's Instrumentation Division in collaboration with the University of Michigan. We use the sharing of electron clouds among several adjacent pixels to measure locations of interaction points with sub-pixel resolution. By using the detectors with small-pixel sizes and a high probability of the charge-sharing events, we were able to improve their spectral resolutions in comparison to the baseline levels, measured for the 1.4-mm pixel size detectors with small fractions of charge-sharing events. These results demonstrate that further enhancement of the performance of CZT pixelated detectors and reduction of costs are possible by using high spatial-resolution position information of interaction points to correct the small-scale response non-uniformities caused by crystal defects present in most devices.

  8. Drift time variations in CdZnTe detectors measured with alpha-particles: Their correlation with the detector’s responses

    Energy Technology Data Exchange (ETDEWEB)

    Bolotnikov A. E.; Butcher, J.; Hamade, M.; Petryk, M.; Bolotnikov, A.; Camarda, G.; Cui, Y.; Hossain, A.; Kim, K.; Yang, G.; and James, R.

    2012-05-14

    Homogeneity of properties related to material crystallinity is a critical parameter for achieving high-performance CdZnTe (CZT) radiation detectors. Unfortunately, this requirement is not always satisfied in today's commercial CZT material due to high concentrations of extended defects, in particular subgrain boundaries, which are believed to be part of the causes hampering the energy resolution and efficiency of CZT detectors. In the past, the effects of subgrain boundaries have been studied in Si, Ge and other semiconductors. It was demonstrated that subgrain boundaries tend to accumulate secondary phases and impurities causing inhomogeneous distributions of trapping centers. It was also demonstrated that subgrain boundaries result in local perturbations of the electric field, which affect the carrier transport and other properties of semiconductor devices. The subgrain boundaries in CZT material likely behave in a similar way, which makes them responsible for variations in the electron drift time and carrier trapping in CZT detectors. In this work, we employed the transient current technique to measure variations in the electron drift time and related the variations to the device performances and subgrain boundaries, whose presence in the crystals were confirmed with white beam X-ray diffraction topography and infrared transmission microscopy.

  9. Achieving subpixel resolution with time-correlated transient signals in pixelated CdZnTe gamma-ray sensors using a focused laser beam (Conference Presentation)

    Science.gov (United States)

    Ocampo Giraldo, Luis A.; Bolotnikov, Aleksey E.; Camarda, Giuseppe S.; Cui, Yonggang; De Geronimo, Gianluigi; Gul, Rubi; Fried, Jack; Hossain, Anwar; Unlu, Kenan; Vernon, Emerson; Yang, Ge; James, Ralph B.

    2017-05-01

    High-resolution position-sensitive detectors have been proposed to correct response non-uniformities in Cadmium Zinc Telluride (CZT) crystals by virtually subdividing the detectors area into small voxels and equalizing responses from each voxel. 3D pixelated detectors coupled with multichannel readout electronics are the most advanced type of CZT devices offering many options in signal processing and enhancing detector performance. One recent innovation proposed for pixelated detectors is to use the induced (transient) signals from neighboring pixels to achieve high sub-pixel position resolution while keeping large pixel sizes. The main hurdle in achieving this goal is the relatively low signal induced on the neighboring pixels because of the electrostatic shielding effect caused by the collecting pixel. In addition, to achieve high position sensitivity one should rely on time-correlated transient signals, which means that digitized output signals must be used. We present the results of our studies to measure the amplitude of the pixel signals so that these can be used to measure positions of the interaction points. This is done with the processing of digitized correlated time signals measured from several adjacent pixels taking into account rise-time and charge-sharing effects. In these measurements we used a focused pulsed laser to generate a 10-micron beam at one milliwatt (650-nm wavelength) over the detector surface while the collecting pixel was moved in cardinal directions. The results include measurements that present the benefits of combining conventional pixel geometry with digital pulse processing for the best approach in achieving sub-pixel position resolution with the pixel dimensions of approximately 2 mm. We also present the sub-pixel resolution measurements at comparable energies from various gamma emitting isotopes.

  10. Using a pulsed laser beam to investigate the feasibility of sub-pixel position resolution with time-correlated transient signals in 3D pixelated CdZnTe detectors

    Science.gov (United States)

    Giraldo, L. Ocampo; Bolotnikov, A. E.; Camarda, G. S.; Cheng, S.; De Geronimo, G.; McGilloway, A.; Fried, J.; Hodges, D.; Hossain, A.; Ünlü, K.; Petryk, M.; Vidal, V.; Vernon, E.; Yang, G.; James, R. B.

    2017-09-01

    We evaluated the X-Y position resolution achievable in 3D pixelated detectors by processing the signal waveforms readout from neighboring pixels. In these measurements we used a focused light beam, down to 10 μm, generated by a 1 mW pulsed laser (650 nm) to carry out raster scans over selected 3×3 pixel areas, while recording the charge signals from the 9 pixels and the cathode using two synchronized digital oscilloscopes.

  11. On drift fields in CMOS Monolithic Active Pixel Sensors with point-like collection diodes

    CERN Document Server

    Deveaux, M; Dorokhov, A; Doering, D; Heymes, J; Kachel, M; Koziel, M; Linnik, B; Müntz, C; Stroth, J

    2016-01-01

    CMOS Monolithic Active Pixel Sensors for charged particle tracking are considered as technology for numerous experiments in heavy ion and particle physics. To match the requirements for those applications in terms of tolerance to non-ionizing radiation, it is being tried to deplete the sensitive volume of the, traditionally non-depleted, silicon sensors. We study the feasibility of this approach for the common case that the collection diodes of the pixel are small as compared to the pixel pitch. An analytic equation predicting the thickness of the depletion depth and the capacity of this point-like junction is introduced. We find that the predictions of this equations differs qualitatively from the usual results for flat PN junctions and that $dC/dU$-measurements are not suited to measure the depletion depth of diodes with point-like geometry. The predictions of the equation is compared with measurements on the depletion depth of CMOS sensors, which were carried out with a novel measurement protocol. It is fo...

  12. IDeF-X ASIC for Cd(Zn)Te spectro-imaging systems

    OpenAIRE

    Limousin, O.; Gevin, O.; Lugiez, F.; Chipaux, R; Delagnes, E.; Dirks, B.; Horeau, B.

    2004-01-01

    Joint progresses in Cd(Zn)Te detectors, microelectronics and interconnection technologies open the way for a new generation of instruments for physics and astrophysics applications in the energy range from 1 to 1000 keV. Even working between -20 and 20 degrees Celsius, these instruments will offer high spatial resolution (pixel size ranging from 300 x 300 square micrometers to few square millimeters), high spectral response and high detection efficiency. To reach these goals, reliable, highly...

  13. Internal electric-field-lines distribution in CdZnTe detectors measured using X-ray mapping

    Energy Technology Data Exchange (ETDEWEB)

    Bolotnikov,A.E.; , .; Camarda, G.S.; Cui, Y.; Hossain, A.; Yang, G.; Yao, H.W.; James, R.B.

    2009-10-19

    The ideal operation of CdZnTe devices entails having a uniformly distributed internal electric field. Such uniformity especially is critical for thick long-drift-length detectors, such as large-volume CPG and 3-D multi-pixel devices. Using a high-spatial resolution X-ray mapping technique, we investigated the distribution of the electric field in real devices. Our measurements demonstrate that in thin detectors, <5 mm, the electric field-lines tend to bend away from the side surfaces (i.e., a focusing effect). In thick detectors, >1 cm, with a large aspect ratio (thickness-to-width ratio), we observed two effects: the electric field lines bending away from or towards the side surfaces, which we called, respectively, the focusing field-line distribution and the defocusing field-line distribution. In addition to these large-scale variations, the field-line distributions were locally perturbed by the presence of extended defects and residual strains existing inside the crystals. We present our data clearly demonstrating the non-uniformity of the internal electric field.

  14. Cross-Sectional Study of Macrodefects in MBE Dual-Band HgCdTe on CdZnTe

    Science.gov (United States)

    Reddy, M.; Lofgreen, D. D.; Jones, K. A.; Peterson, J. M.; Radford, W. A.; Benson, J. D.; Johnson, S. M.

    2013-11-01

    HgCdTe dual-band mid-wave infrared/long-wave infrared focal-plane arrays on CdZnTe are a key component in advanced electrooptic sensor applications. Molecular beam epitaxy (MBE) has been used successfully for growth of dual-band layers on larger CdZnTe substrates. However, the macrodefect density, which is known to reduce the pixel operability and its run-to-run variation, is larger when compared with layers grown on Si substrate. This paper reports the macrodefect density versus size signature of a well-optimized MBE dual-band growth and a cross-sectional study of a macrodefect that represents the most prevalent class using focused ion beam, scanning transmission electron microscopy, and energy-dispersive x-ray spectroscopy. The results show that the macrodefect originates from a void, which in turn is associated with a pit on the CdZnTe substrate.

  15. Prototype Imaging Cd-Zn-Te Array Detector

    CERN Document Server

    Bloser, P F; Grindlay, J E; Shah, K

    1998-01-01

    We describe initial results of our program to develop and test Cd-Zn-Te (CZT) detectors with a pixellated array readout. Our primary interest is in the development of relatively thick CZT detectors for use in astrophysical coded aperture telescopes with response extending over the energy range $\\sim 10-600$ keV. The coded aperture imaging configuration requires only relatively large area pixels (1-3 mm), whereas the desired high energy response requires detector thicknesses of at least 3-5 mm. We have developed a prototype detector employing a 10 x 10 x 5 mm CZT substrate and 4 x 4 pixel (1.5 mm each) readout with gold metal contacts for the pixels and continuous gold contact for the bias on the opposite detector face. This MSM contact configuration was fabricated by RMD and tested at Harvard for uniformity, efficiency and spatial as well as spectral resolution. We have developed an ASIC readout (IDE-VA-1) and analysis system and report results, including $\\sim 4$% (FWHM) energy resolution at 60 keV. A protot...

  16. Prototype imaging Cd-Zn-Te array detector

    Energy Technology Data Exchange (ETDEWEB)

    Bloser, P.F.; Narita, T.; Grindlay, J.E. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States); Shah, K. [Radiation Monitoring Devices, Inc., Watertown, MA (United States)

    1998-12-31

    The authors describe initial results of their program to develop and test Cd-Zn-Te (CZT) detectors with a pixellated array readout. Their primary interest is in the development of relatively thick CZT detectors for use in astrophysical coded aperture telescopes with response extending over the energy range {approximately}10--600 keV. The coded aperture imaging configuration requires only relatively large area pixels (1--3 mm), whereas the desired high energy response requires detector thicknesses of at least 3--5 mm. They have developed a prototype detector employing a 10 x 10 x 5 mm CZT substrate and 4 x 4 pixel (1.5 mm each) readout with gold metal contacts for the pixels and continuous gold contact for the bias on the opposite detector face. This MSM contact configuration was fabricated by RMD and tested at Harvard for uniformity, efficiency and spatial as well as spectral resolution. The authors have developed an ASIC readout (IDE-VA-1) and analysis system and report results, including {approximately}4% (FWHM) energy resolution at 60 keV. A prototype design for a full imaging detector array is discussed.

  17. The Effect of Twin Boundaries on the Spectroscopic Performance of CdZnTe Detectors

    Science.gov (United States)

    Parker, Bradford H.; Stahle, C. M.; Roth, D.; Babu, S.; Tueller, Jack; Powers, Edward I. (Technical Monitor)

    2001-01-01

    Most single grains in cadmium zinc telluride (CdZnTe) grown by the high-pressure Bridgman (HPB) technique contain multiple twin boundaries. As a consequence, twin boundaries are one of the most common macroscopic material defects found in large area (400 to 700 sq mm) CdZnTe specimens obtained from HPB ingots. Due to the prevalence of twin boundaries, understanding their effect on detector performance is key to the material selection process. Twin boundaries in several 2 mm thick large area specimens were first, documented using infrared transmission imaging. These specimens were then fabricated into either 2 mm pixel or planar detectors in order to examine the effect of the twin boundaries on detector performance. Preliminary results show that twin boundaries, which are decorated with tellurium inclusions, produce a reduction in detector efficiency and a degradation in resolution. The extent of the degradation appears to be a function of the density of tellurium inclusions.

  18. Modelling semiconductor pixel detectors

    CERN Document Server

    Mathieson, K

    2001-01-01

    expected after 200 ps in most cases. The effect of reducing the charge carrier lifetime and examining the charge collection efficiency has been utilised to explore how these detectors would respond in a harsh radiation environment. It is predicted that over critical carrier lifetimes (10 ps to 0.1 ns) an improvement of 40 % over conventional detectors can be expected. This also has positive implications for fabricating detectors, in this geometry, from materials which might otherwise be considered substandard. An analysis of charge transport in CdZnTe pixel detectors has been performed. The analysis starts with simulation studies into the formation of contacts and their influence on the internal electric field of planar detectors. The models include a number of well known defect states and these are balanced to give an agreement with a typical experimental I-V curve. The charge transport study extends to the development of a method for studying the effect of charge sharing in highly pixellated detectors. The ...

  19. A single CdZnTe detector for simultaneous CT/SPECT imaging

    Energy Technology Data Exchange (ETDEWEB)

    Barber, W.C. E-mail: bill@barber.uscf.edu; Iwata, Koji; Hasegawa, B.H.; Bennett, P.R.; Cirignano, L.J.; Shah, K.S

    2003-06-01

    Clinical CT/SPECT systems acquire CT and SPECT data sequentially using different detectors in close proximity to minimise patient movement and interscan delay. We have developed a prototype simultaneous CT/SPECT imager, using a single CdZnTe detector, with the goal of improving image coregistration and decreasing scan time. A 16-pixel CdZnTe detector was operated in pulse-counting mode with 50 ns shaping time. Energy discrimination is used to separate the CT and SPECT data. Simultaneous SPECT and CT images were obtained for a phantom with the X-ray flux limited to reduce pulse pile-up in the radionuclide energy window. At 140 keV, the efficiency and energy resolution are 70% and 10%, respectively, and were constant for fluence rates up to 10{sup 3} cps per detector element for 140 keV gamma rays, but degrade rapidly at higher fluence rates. In pulse-counting mode, the maximum count rate of 10{sup 3} cps per element from the CdZnTe detector is sufficient for SPECT imaging, but is considerably lower than the fluence rates encountered in CT. The smallest lesion visually detectable in SPECT is 9 mm and the CT spatial resolution is smaller than 4.5 mm. Image registration is intrinsic because the data can be acquired simultaneously with a single detector with the same reconstruction geometry.

  20. PERFORMANCE STUDIES OF CDZNTE DETECTOR BY USING A PULSE SHAPE ANALYSIS.

    Energy Technology Data Exchange (ETDEWEB)

    BOLOTNIKOV, A.

    2005-07-31

    Pulse shape analysis is proved to be a powerful tool to characterize the performance of CdZnTe devices and understand their operating principles. It allows one to investigate the device configurations, electron transport properties, effects governing charge collection, electric-field distributions, signal charge formation, etc. This work describes an application of different techniques based on the pulse shape measurements to characterize pixel, coplanar-grid, and virtual Frisch-grid devices and understand the electronic properties of CZT material provided by different vendors. We report new results that may explain the performance limits of these devices.

  1. Silicon Drift Detectors for ALICE

    CERN Document Server

    Navach, F; CERN. Geneva

    1992-01-01

    The Silicon Drift Detector (SDD) is a semiconductor, not yet extensively used in HEP experiment, which has an excellent spatial resolution and granularity about comparable to a pixel device requiring a number of readout channels two order of magnitude less.

  2. Response of CZT drift-strip detector to X- and gamma rays

    DEFF Research Database (Denmark)

    Kuvvetli, Irfan; Budtz-Jørgensen, Carl; Gerward, Leif

    2001-01-01

    The drift-strip method for improving the energy response of a CdZnTe (CZT) detector to hard X- and gamma rays is discussed. Results for a 10 x 10 x 3 mm(3) detector crystal demonstrate a remarkable improvement of the energy resolution. The full width at half maximum (FWHM) is 2.18 keV (3.6%), 2...

  3. Pixel Experiments

    DEFF Research Database (Denmark)

    Petersen, Kjell Yngve; Søndergaard, Karin; Augustesen, Christina

    2015-01-01

    Pixel Experiments The term pixel is traditionally defined as any of the minute elements that together constitute a larger context or image. A pixel has its own form and is the smallest unit seen within a larger structure. In working with the potentials of LED technology in architectural lighting...... design it became relevant to investigate the use of LEDs as the physical equivalent of a pixel as a design approach. In this book our interest has been in identifying how the qualities of LEDs can be used in lighting applications. With experiences in the planning and implementation of architectural...... elucidate and exemplify already well-known problems in relation to the experience of vertical and horizontal lighting. Pixel Experiments exist as a synergy between speculative test setups and lighting design in practice. This book is one of four books that is published in connection with the research...

  4. Pixel Detectors

    OpenAIRE

    Wermes, Norbert

    2005-01-01

    Pixel detectors for precise particle tracking in high energy physics have been developed to a level of maturity during the past decade. Three of the LHC detectors will use vertex detectors close to the interaction point based on the hybrid pixel technology which can be considered the state of the art in this field of instrumentation. A development period of almost 10 years has resulted in pixel detector modules which can stand the extreme rate and timing requirements as well as the very harsh...

  5. Analysis of Etched CdZnTe Substrates

    Science.gov (United States)

    Benson, J. D.; Bubulac, L. O.; Jaime-Vasquez, M.; Lennon, C. M.; Arias, J. M.; Smith, P. J.; Jacobs, R. N.; Markunas, J. K.; Almeida, L. A.; Stoltz, A.; Wijewarnasuriya, P. S.; Peterson, J.; Reddy, M.; Jones, K.; Johnson, S. M.; Lofgreen, D. D.

    2016-09-01

    State-of-the-art as-received (112)B CdZnTe substrates have been examined for surface impurity contamination and polishing residue. Two 4 cm × 4 cm and one 6 cm × 6 cm (112)B state-of-the-art as-received CdZnTe wafers were analyzed. A maximum surface impurity concentration of Al = 1.7 × 1015 atoms cm-2, Si = 3.7 × 1013 atoms cm-2, Cl = 3.12 × 1015 atoms cm-2, S = 1.7 × 1014 atoms cm-2, P = 1.1 × 1014 atoms cm-2, Fe = 1.0 × 1013 atoms cm-2, Br = 1.2 × 1014 atoms cm-2, and Cu = 4 × 1012 atoms cm-2 was observed on the as-received CdZnTe wafers. CdZnTe particulates and residual SiO2 polishing grit were observed on the surface of the as-received (112)B CdZnTe substrates. The polishing grit/CdZnTe particulate density on CdZnTe wafers was observed to vary across a 6 cm × 6 cm wafer from ˜4 × 107 cm-2 to 2.5 × 108 cm-2. The surface impurity and damage layer of the (112)B CdZnTe wafers dictate that a molecular beam epitaxy (MBE) preparation etch is required. The contamination for one 4 cm × 4 cm and one 6 cm × 6 cm CdZnTe wafer after a standard MBE Br:methanol preparation etch procedure was also analyzed. A maximum surface impurity concentration of Al = 2.4 × 1015 atoms cm-2, Si = 4.0 × 1013 atoms cm-2, Cl = 7.5 × 1013 atoms cm-2, S = 4.4 × 1013 atoms cm-2, P = 9.8 × 1013 atoms cm-2, Fe = 1.0 × 1013 atoms cm-2, Br = 2.9 × 1014 atoms cm-2, and Cu = 5.2 × 1012 atoms cm-2 was observed on the MBE preparation-etched CdZnTe wafers. The MBE preparation-etched surface contamination consists of Cd(Zn)Te particles/flakes. No residual SiO2 polishing grit was observed on the (112)B surface.

  6. Charge-Sensitive Front-End Electronics with Operational Amplifiers for CdZnTe Detectors

    CERN Document Server

    Födisch, P; Lange, B; Kirschke, T; Enghardt, W; Kaever, P

    2016-01-01

    Cadmium zinc telluride (CdZnTe, "CZT") radiation detectors are announced to be a game-changing detector technology. However, state-of-the-art detector systems require high-performance readout electronics as well. Even though an application-specific integrated circuit (ASIC) is an adequate solution for the readout, our demands on a high dynamic range for energy measurement and a high throughput are not served by any commercially available circuit. Consequently, we had to develop the analog front-end electronics with operational amplifiers for an 8x8 pixelated CZT detector. For this purpose, we model an electrical equivalent circuit of the CZT detector with the associated charge-sensitive amplifier (CSA). Therefore, we present the mathematical equations for a detailed network analysis. Additionally, we enhance the design with numerical values for various features such as ballistic deficit, charge-to-voltage gain, rise time, noise level and verify the performance with synthetic detector signals. With this benchm...

  7. Direct conversion Si and CdZnTe detectors for digital mammography

    CERN Document Server

    Yin Shi Shi; Maeding, D; Mainprize, J; Mawdsley, G; Yaffe, M J; Gordon, E E; Hamilton, W J

    2000-01-01

    Hybrid pixel detector arrays that convert X-rays directly into charge signals are under development at NOVA for application to digital mammography. This technology also has wide application possibilities in other fields of radiology or in industrial imaging, nondestructive evaluation (NDE) and nondestructive inspection (NDI). These detectors have potentially superior properties compared to either emulsion-based film-screen systems which has nonlinear response to X-rays, or phosphor-based detectors in which there is an intermediate step of X-ray to light photon conversion (Feig and Yaffe, Radiol. Clinics North America 33 (1995) 1205-1230). Potential advantages of direct conversion detectors are high quantum efficiencies (QE) of 98% or higher (for 0.3 mm thick CdZnTe detector with 20 keV X-rays), improved contrast, high sensitivity and low intrinsic noise. These factors are expected to contribute to high detective quantum efficiency (DQE). The prototype hybrid pixel detector developed has 50x50 mu m pixel size,...

  8. Charge-sensitive front-end electronics with operational amplifiers for CdZnTe detectors

    Science.gov (United States)

    Födisch, P.; Berthel, M.; Lange, B.; Kirschke, T.; Enghardt, W.; Kaever, P.

    2016-09-01

    Cadmium zinc telluride (CdZnTe, CZT) radiation detectors are suitable for a variety of applications, due to their high spatial resolution and spectroscopic energy performance at room temperature. However, state-of-the-art detector systems require high-performance readout electronics. Though an application-specific integrated circuit (ASIC) is an adequate solution for the readout, requirements of high dynamic range and high throughput are not available in any commercial circuit. Consequently, the present study develops the analog front-end electronics with operational amplifiers for an 8×8 pixelated CZT detector. For this purpose, we modeled an electrical equivalent circuit of the CZT detector with the associated charge-sensitive amplifier (CSA). Based on a detailed network analysis, the circuit design is completed by numerical values for various features such as ballistic deficit, charge-to-voltage gain, rise time, and noise level. A verification of the performance is carried out by synthetic detector signals and a pixel detector. The experimental results with the pixel detector assembly and a 22Na radioactive source emphasize the depth dependence of the measured energy. After pulse processing with depth correction based on the fit of the weighting potential, the energy resolution is 2.2% (FWHM) for the 511 keV photopeak.

  9. Pixel detectors

    CERN Document Server

    Passmore, M S

    2001-01-01

    positions on the detector. The loss of secondary electrons follows the profile of the detector and increases with higher energy ions. studies of the spatial resolution predict a value of 5.3 lp/mm. The image noise in photon counting systems is investigated theoretically and experimentally and is shown to be given by Poisson statistics. The rate capability of the LAD1 was measured to be 250 kHz per pixel. Theoretical and experimental studies of the difference in contrast for ideal charge integrating and photon counting imaging systems were carried out. It is shown that the contrast differs and that for the conventional definition (contrast = (background - signal)/background) the photon counting device will, in some cases, always give a better contrast than the integrating system. Simulations in MEDICI are combined with analytical calculations to investigate charge collection efficiencies (CCE) in semiconductor detectors. Different pixel sizes and biasing conditions are considered. The results show charge shari...

  10. Improving performance of a CdZnTe imaging array by mapping the detector with gamma rays

    CERN Document Server

    Marks, D G; Barrett, H H; Tüller, J; Woolfenden, J M

    1999-01-01

    We can greatly reduce image artifacts in our pixellated CdZnTe arrays by mapping imperfect regions with a narrow collimated beam of gamma rays. Portions of our detectors produce signals that agree well with simulations of gamma-ray interactions, but there are many examples of structures in the material that respond unpredictably to gamma rays. We mapped some of these imperfect regions using 60 and 140 keV gamma-ray beams, recording a 7x7 set of pixel signals for each interaction. The pixel pitch was 380 mu m. We used the mapped data to estimate the probability density function (PDF) of the pixel signals for each interaction position. Images were taken on the mapped sections, storing each gamma ray as a list of pixel signals. Images could be formed by either estimating each gamma-ray interaction position individually or using the entire set of image data in a single iterative computation using the expectation-maximization (EM) algorithm. At 60 keV individual interaction positions were estimated by fitting the ...

  11. Point Defect Characterization in CdZnTe

    Energy Technology Data Exchange (ETDEWEB)

    Gul,R.; Li, Z.; Bolotnikov, A.; Keeter, K.; Rodriguez, R.; James, R.

    2009-03-24

    Measurements of the defect levels and performance testing of CdZnTe detectors were performed by means of Current Deep Level Transient Spectroscopy (I-DLTS), Transient Charge Technique (TCT), Current versus Voltage measurements (I-V), and gamma-ray spectroscopy. CdZnTe crystals were acquired from different commercial vendors and characterized for their point defects. I-DLTS studies included measurements of defect parameters such as energy levels in the band gap, carrier capture cross sections, and defect densities. The induced current due to laser-generated carriers was measured using TCT. The data were used to determine the transport properties of the detectors under study. A good correlation was found between the point defects in the detectors and their performance.

  12. CdZnTe Background Measurement at Balloon Altitudes

    CERN Document Server

    Bloser, P F; Narita, T; Harrison, F

    1998-01-01

    We report results of an experiment conducted in May 1997 to measure CdZnTe background and background reduction schemes in space flight conditions similar to those of proposed hard X-ray astrophysics missions. A 1 cm^2 CdZnTe detector was placed adjacent to a thick BGO anticoincidence shield and flown piggybacked onto the EXITE2 scientific balloon payload. The planar shield was designed to veto background countsproduced by local gamma-ray production in passive material and neutron interactions in the detector. The CdZnTe and BGO were partially surrounded by a Pb-Sn-Cu shield to approximate the grammage of an X-ray collimator, although the field of view was still ~2 pi sr. At an altitude of 127000 feet we find a reduction in background by a factor of 6 at 100 keV. The non-vetoed background is 9 X 10^{-4} cts /cm^2-sec-keV at 100 keV, about a factor of 2 higher than that of the collimated (4.5 deg FWHM) EXITE2 phoswich detector. We compare our recorded spectrum with that expected from simulations using GEANT and...

  13. Adaptive bad pixel correction algorithm for IRFPA based on PCNN

    Science.gov (United States)

    Leng, Hanbing; Zhou, Zuofeng; Cao, Jianzhong; Yi, Bo; Yan, Aqi; Zhang, Jian

    2013-10-01

    Bad pixels and response non-uniformity are the primary obstacles when IRFPA is used in different thermal imaging systems. The bad pixels of IRFPA include fixed bad pixels and random bad pixels. The former is caused by material or manufacture defect and their positions are always fixed, the latter is caused by temperature drift and their positions are always changing. Traditional radiometric calibration-based bad pixel detection and compensation algorithm is only valid to the fixed bad pixels. Scene-based bad pixel correction algorithm is the effective way to eliminate these two kinds of bad pixels. Currently, the most used scene-based bad pixel correction algorithm is based on adaptive median filter (AMF). In this algorithm, bad pixels are regarded as image noise and then be replaced by filtered value. However, missed correction and false correction often happens when AMF is used to handle complex infrared scenes. To solve this problem, a new adaptive bad pixel correction algorithm based on pulse coupled neural networks (PCNN) is proposed. Potential bad pixels are detected by PCNN in the first step, then image sequences are used periodically to confirm the real bad pixels and exclude the false one, finally bad pixels are replaced by the filtered result. With the real infrared images obtained from a camera, the experiment results show the effectiveness of the proposed algorithm.

  14. Cooled CdZnTe detectors for X-ray astronomy

    CERN Document Server

    Bale, G; Seller, P; Lowe, B

    1999-01-01

    Recent results combining thermoelectrically cooled CdZnTe detectors with a low-noise Pentafet preamplifier are presented. Cooling between -30 deg. C and -40 deg. C reduces the leakage current of the detectors and allows the use of a pulsed reset preamplifier and long shaping times, significantly improving the energy resolution. Mn K subalpha X-rays at 5.9 keV have been observed with a resolution of less than 280 eV FWHM and a peak to background of more than 200:1. The Fano factor of the material has been estimated at 0.11+-0.012 at -40 deg. C. The detector requirement for X-ray astronomy will be a photon-counting imaging spectrometer. A 16x16 element, bump bonded pixel detector is described and results from a prototype silicon array presented. The detector is constructed with ASIC amplifiers with a system noise of <25 electrons rms and should give an energy resolution comparable to the Pentafet results presented here.

  15. Material-specific imaging system using energy-dispersive X-ray diffraction and spatially resolved CdZnTe detectors with potential application in breast imaging

    Science.gov (United States)

    Barbes, Damien; Tabary, Joachim; Paulus, Caroline; Hazemann, Jean-Louis; Verger, Loïck

    2017-03-01

    This paper presents a coherent X-ray-scattering imaging technique using a multipixel energy-dispersive system. Without any translation, the technique produces specific 1D image from data recorded by a single CdZnTe detector pixel using subpixelation techniques. The method is described in detail, illustrated by a simulation and then experimentally validated. As the main considered application of our study is breast imaging, this validation involves 2D imaging of a phantom made of plastics mimicking breast tissues. The results obtained show that our system can specifically image the phantom using a single detector pixel. For the moment, in vivo breast imaging applications remain difficult, as the dose delivered by the system is too high, but some adjustments are considered for further work.

  16. Characteristics of a prototype CdZnTe detector

    Institute of Scientific and Technical Information of China (English)

    XU Huichao; CHENG Cheng; ZHAO Cuilan; ZHANG Jinzhou; PU Shijie

    2007-01-01

    Cadmium zinc telluride(CZT)is a preferred material for X-ray and gamma-ray detector.Thanks to the relatively high atomic number,high density and wide band-gap.CZT detector possesses sharp energy resolution and high detection efficiency without cryogenic cooling.We have developed a CdZnTe detector with an energy resolution of 3.45%(FWHM)at 59.54 keV at room temperature.and it is used for X-ray fluorescence analysis.In this paper,leakage current,energy resolution and long term stability of the CZT detector are discussed.

  17. NEW RESULTS FROM TESTING OF COPLANAR-GRID CDZNTE DETECTOR.

    Energy Technology Data Exchange (ETDEWEB)

    CARINI, G.A.; ET AL.

    2005-07-31

    New results from studies of coplanar-grid CdZnTe (CZT) detectors are presented. The coplanar-grid detectors, were investigated by using a highly collimated X-ray beam available at Brookhaven's National Synchrotron Light Source and by applying a pulse-shape analysis. The coplanar-grid detector operates as a single-carrier device. Despite the fact that its operational principle is well known and has been investigated by many groups in the past, we found some new details that may explain the performance limits of these types of devices. The experimental results have been confirmed by extensive computer modeling.

  18. PHOTOINDUCED CURRENTS IN CDZNTE CRYSTALS AS A FUNCTION OF ILLUMINATION WAVELENGTH

    Energy Technology Data Exchange (ETDEWEB)

    Teague, L.; Washington, A.; Duff, M.

    2012-04-23

    We report variations in the currents of CdZnTe semiconductor crystals during exposure to a series of light emitting diodes of various wavelengths ranging from 470 to 950 nm. The changes in the steady-state current of one CdZnTe crystal with and without illumination along with the time dependence of the illumination effects are discussed. Analysis of the de-trapping and transient bulk currents during and after optical excitation yield insight into the behaviour of charge traps within the crystal. Similar behaviour is observed for illumination of a second CdZnTe crystal suggesting that the overall illumination effects are not crystal dependent.

  19. Monolithic pixel detectors for high energy physics

    CERN Document Server

    Snoeys, W

    2013-01-01

    Monolithic pixel detectors integrating sensor matrix and readout in one piece of silicon have revolutionized imaging for consumer applications, but despite years of research they have not yet been widely adopted for high energy physics. Two major requirements for this application, radiation tolerance and low power consumption, require charge collection by drift for the most extreme radiation levels and an optimization of the collected signal charge over input capacitance ratio ( Q / C ). It is shown that monolithic detectors can achieve Q / C for low analog power consumption and even carryout the promise to practically eliminate analog power consumption, but combining suf fi cient Q / C , collection by drift, and integration of readout circuitry within the pixel remains a challenge. An overview is given of different approaches to address this challenge, with possible advantages and disadvantages.

  20. Modelling and 3D optimisation of CdTe pixels detector array geometry - Extension to small pixels

    CERN Document Server

    Zumbiehl, A; Fougeres, P; Koebel, J M; Regal, R; Rit, C; Ayoub, M; Siffert, P

    2001-01-01

    CdTe and CdZnTe pixel detectors offer great interest for many applications, especially for medical and industrial imaging. Up to now, the material, generally, used and investigated for pixel arrays was CZT (Hamel et al., IEEE Trans. Nucl. Sci. 43 (3) (1996) 1422; Barrett et al., Phys. Rev. Lett. 75 (1) (1995) 156; Bennett et al., Nucl. Instr. and Meth. A 392 (1997) 260; Eskin et al., J. Appl. Phys. 85 (2) (1999) 647; Brunett et al., J. Appl. Phys. 86 (7) (1999) 3926; Luke, Nucl. Instr. and Meth. A 380 (1996) 232), but cadmium telluride can also be an appropriate choice, as shown here. However, we clearly demonstrate here that the optimal pixel configuration is highly dependent on the electrical transport properties of the material. Depending on the field of primary interest, either energy resolution or counting rate efficiency in the photopeak, the geometry for each case has to be optimised. For that purpose, we have developed a calculation of the signal induced onto the pixel. Two distinct parts are used: af...

  1. Performance simulation of an x-ray detector for spectral CT with combined Si and Cd[Zn]Te detection layers.

    Science.gov (United States)

    Herrmann, Christoph; Engel, Klaus-Jürgen; Wiegert, Jens

    2010-12-21

    The most obvious problem in obtaining spectral information with energy-resolving photon counting detectors in clinical computed tomography (CT) is the huge x-ray flux present in conventional CT systems. At high tube voltages (e.g. 140 kVp), despite the beam shaper, this flux can be close to 10⁹ Mcps mm⁻² in the direct beam or in regions behind the object, which are close to the direct beam. Without accepting the drawbacks of truncated reconstruction, i.e. estimating missing direct-beam projection data, a photon-counting energy-resolving detector has to be able to deal with such high count rates. Sub-structuring pixels into sub-pixels is not enough to reduce the count rate per pixel to values that today's direct converting Cd[Zn]Te material can cope with (≤ 10 Mcps in an optimistic view). Below 300 µm pixel pitch, x-ray cross-talk (Compton scatter and K-escape) and the effect of charge diffusion between pixels are problematic. By organising the detector in several different layers, the count rate can be further reduced. However this alone does not limit the count rates to the required level, since the high stopping power of the material becomes a disadvantage in the layered approach: a simple absorption calculation for 300 µm pixel pitch shows that the required layer thickness of below 10 Mcps/pixel for the top layers in the direct beam is significantly below 100 µm. In a horizontal multi-layer detector, such thin layers are very difficult to manufacture due to the brittleness of Cd[Zn]Te. In a vertical configuration (also called edge-on illumination (Ludqvist et al 2001 IEEE Trans. Nucl. Sci. 48 1530-6, Roessl et al 2008 IEEE NSS-MIC-RTSD 2008, Conf. Rec. Talk NM2-3)), bonding of the readout electronics (with pixel pitches below 100 µm) is not straightforward although it has already been done successfully (Pellegrini et al 2004 IEEE NSS MIC 2004 pp 2104-9). Obviously, for the top detector layers, materials with lower stopping power would be advantageous

  2. An investigation of performance characteristics of a pixellated room-temperature semiconductor detector for medical imaging

    Energy Technology Data Exchange (ETDEWEB)

    Guerra, P; Santos, A [Centro de Investigacion Biomedica de Bioningenieria, Biomateriales y Nanomedicina, CEEI-Modulo 3, C/ Maria de Luna, 11, 50018 Zaragoza (United States); Darambara, D G, E-mail: pguerra@ciber-bbn.e [Joint Department of Physics, Royal Marsden NHS Foundation Trust and Institute of Cancer Research, Fulham Road, London SW3 6JJ (United Kingdom)

    2009-09-07

    The operation of any semiconductor detector depends on the movement of the charge carriers, which are created within the material when radiation passes through, as a result of energy deposition. The carrier movement in the bulk semiconductor induces charges on the metal electrodes, and therefore a current on the electrodes and the external circuit. The induced charge strongly depends on the material transport parameters as well as the geometrical dimensions of a pixellated semiconductor detector. This work focuses on the performance optimization in terms of energy resolution, detection efficiency and intrinsic spatial resolution of a room-temperature semiconductor pixellated detector based on CdTe/CdZnTe. It analyses and inter-relates these performance figures for various dimensions of CdTe and CdZnTe detectors and for an energy range spanning from x-ray (25 keV) to PET (511 keV) imaging. Monte Carlo simulations, which integrate a detailed and accurate noise model, are carried out to investigate several CdTe/CdZnTe configurations and to determine possible design specifications. Under the considered conditions, the simulations demonstrate the superiority of the CdZnTe over the CdTe in terms of energy resolution and sensitivity in the photopeak. Further, according to the results, the spatial resolution is maximized at high energies and the energy resolution at low energies, while a reasonable detection efficiency is achieved at high energies, with a 1 x 1 x 6 mm{sup 3} CdZnTe pixellated detector.

  3. ADVANCED READOUT ELECTRONICS FOR MULTIELEMENT CdZnTe SENSORS.

    Energy Technology Data Exchange (ETDEWEB)

    DE GERONIMO,G.; O CONNOR,P.; KANDASAMY,A.; GROSHOLZ,J.

    2002-07-08

    A generation of high performance front-end and read-out ASICs customized for highly segmented CdZnTe sensors is presented. The ASICs, developed in a multi-year effort at Brookhaven National Laboratory, are targeted to a wide range of applications including medical, safeguards/security, industrial, research, and spectroscopy. The front-end multichannel ASICs provide high accuracy low noise preamplification and filtering of signals, with versions for small and large area CdZnTe elements. They implement a high order unipolar or bipolar shaper, an innovative low noise continuous reset system with self-adapting capability to the wide range of detector leakage currents, a new system for stabilizing the output baseline and high output driving capability. The general-purpose versions include programmable gain and peaking time. The read-out multichannel ASICs provide fully data driven high accuracy amplitude and time measurements, multiplexing and time domain derandomization of the shaped pulses. They implement a fast arbitration scheme and an array of innovative two-phase offset-free rail-to-rail analog peak detectors for buffering and absorption of input rate fluctuations, thus greatly relaxing the rate requirement on the external ADC. Pulse amplitude, hit timing, pulse risetime, and channel address per processed pulse are available at the output in correspondence of an external readout request. Prototype chips have been fabricated in 0.5 and 0.35 {micro}m CMOS and tested. Design concepts and experimental results are discussed.

  4. Development of Portable Uranium Enrichment Measurement Apparatus With CdZnTe Detector

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    <正>A portable uranium enrichment measurement apparatus with CdZnTe detector manufactured by "eV Products" company was tested in this work. The apparatus consists of a co-planar grid detector based on

  5. ATLAS IBL Pixel Upgrade

    CERN Document Server

    La Rosa, A

    2011-01-01

    The upgrade for ATLAS detector will undergo different phase towards super-LHC. The first upgrade for the Pixel detector will consist of the construction of a new pixel layer which will be installed during the first shutdown of the LHC machine (LHC phase-I upgrade). The new detector, called Insertable B-Layer (IBL), will be inserted between the existing pixel detector and a new (smaller radius) beam-pipe at a radius of 3.3 cm. The IBL will require the development of several new technologies to cope with increase of radiation or pixel occupancy and also to improve the physics performance which will be achieved by reducing the pixel size and of the material budget. Three different promising sensor technologies (planar-Si, 3D-Si and diamond) are currently under investigation for the pixel detector. An overview of the project with particular emphasis on pixel module is presented in this paper

  6. Interface chemistry of CdZnTe films studied by a peel-off approach

    Science.gov (United States)

    Tao, Jun; Xu, Haitao; Zhang, Yuelu; Ji, Huanhuan; Xu, Run; Huang, Jian; Zhang, Jijun; Liang, Xiaoyan; Tang, Ke; Wang, Linjun

    2016-12-01

    CdZnTe films with thickness above 50 μm were deposited at temperatures of 200-500 °C by Close Space Sublimation method. A peel-off approach has been adopted to study the interface chemistry of CdZnTe thick films. For all the CdZnTe films, the scanning electron microscopy images show the small and round-like grains formed at interface in contrast to the large ordered grains at surface. For CdZnTe films grown at a low substrate temperature of 200 °C, the interface layer between CdZnTe and substrate is mixed with Te and CdTe, as evidenced by X-ray diffraction, Raman and X-ray photoelectron spectroscopy results. The thickness of the interface layer can be estimated to be 84 nm by depth profile using X-ray photoelectron spectroscopy. In contrast, a thin interface layer less than 14 nm is found at a high substrate temperature of 500 °C. The limited reaction of Te2 and Cd (Zn) to CdZnTe at a low growth temperature is responsible for the formation of the thick interface layer and a slow deposition rate at the nucleation stage.

  7. Pixel Vertex Detectors

    OpenAIRE

    Wermes, Norbert

    2006-01-01

    Pixel vertex detectors are THE instrument of choice for the tracking of charged particles close to the interaction point at the LHC. Hybrid pixel detectors, in which sensor and read-out IC are separate entities, constitute the present state of the art in detector technology. Three of the LHC detectors use vertex detectors based on this technology. A development period of almost 10 years has resulted in pixel detector modules which can stand the extreme rate and timing requirements as well as ...

  8. READOUT SYSTEM FOR ARRAYS OF FRISCH-RING CDZNTE DETECTORS.

    Energy Technology Data Exchange (ETDEWEB)

    CUI, Y.; BOLOTNIKOV, A.E.; CAMARDA, G.S.; DE GERONIMO, G.; O' CONNOR, P.; JAMES, R.B.; KARGAR, A.; HARRISON, M.J.; MCGREGOR, D.S.

    2006-10-29

    Frisch-ring CdZnTe detectors have demonstrated good energy resolution for identifying isotopes, <1% FWHM at 662 keV, and good efficiency for detecting gamma rays. We will fabricate and test at Brookhaven National Laboratory an integrated module of a 64-element array of 6 x 6 x 12 mm{sup 3} Frisch-ring detectors, coupled with a readout electronics system. It supports 64 readout channels, and includes front-end electronics, signal processing circuit, USB interface and high-voltage power supply. The data-acquisition software is used to process the data stream, which includes amplitude and timing information for each detected event. This paper describes the design and assembly of the detector modules, readout electronics, and a conceptual prototype system. Some test results are also reported.

  9. Monolithic pixels on moderate resistivity substrate and sparsifying readout architecture

    Science.gov (United States)

    Giubilato, P.; Battaglia, M.; Bisello, D.; Caselle, M.; Chalmet, P.; Demaria, L.; Ikemoto, Y.; Kloukinas, K.; Mansuy, S. C.; Mattiazzo, S.; Marchioro, A.; Mugnier, H.; Pantano, D.; Potenza, A.; Rivetti, A.; Rousset, J.; Silvestrin, L.; Snoeys, W.

    2013-12-01

    The LePix projects aim realizing a new generation monolithic pixel detectors with improved performances at lesser cost with respect to both current state of the art monolithic and hybrid pixel sensors. The detector is built in a 90 nm CMOS process on a substrate of moderate resistivity. This allows charge collection by drift while maintaining the other advantages usually offered by MAPS, like having a single piece detector and using a standard CMOS production line. The collection by drift mechanism, coupled to the low capacitance design of the collecting node made possible by the monolithic approach, provides an excellent signal to noise ratio straight at the pixel cell together with a radiation tolerance far superior to conventional un-depleted MAPS. The excellent signal-to-noise performance is demonstrated by the device ability to separate the 6 keV 55Fe double peak at room temperature. To achieve high granularity (10-20 μm pitch pixels) over large detector areas maintaining high readout speed, a completely new compressing architecture has been devised. This architecture departs from the mainstream hybrid pixel sparsification approach, which uses in-pixel logic to reduce data, by using topological compression to minimize pixel area and power consumption.

  10. Performance characteristics of CdTe drift ring detector

    Science.gov (United States)

    Alruhaili, A.; Sellin, P. J.; Lohstroh, A.; Veeramani, P.; Kazemi, S.; Veale, M. C.; Sawhney, K. J. S.; Kachkanov, V.

    2014-03-01

    CdTe and CdZnTe material is an excellent candidate for the fabrication of high energy X-ray spectroscopic detectors due to their good quantum efficiency and room temperature operation. The main material limitation is associated with the poor charge transport properties of holes. The motivation of this work is to investigate the performance characteristics of a detector fabricated with a drift ring geometry that is insensitive to the transport of holes. The performance of a prototype Ohmic CdTe drift ring detector fabricated by Acrorad with 3 drift rings is reported; measurements include room temperature current voltage characteristics (IV) and spectroscopic performance. The data shows that the energy resolution of the detector is limited by leakage current which is a combination of bulk and surface leakage currents. The energy resolution was studied as a function of incident X-ray position with an X-ray microbeam at the Diamond Light Source. Different ring biasing schemes were investigated and the results show that by increasing the lateral field (i.e. the bias gradient across the rings) the active area, evaluated by the detected count rate, increased significantly.

  11. High-Efficiency CdZnTe Position-Sensitive VFG Gamma-Ray Detectors for Safeguards Applications

    Energy Technology Data Exchange (ETDEWEB)

    Bolotnikov, Aleksey E. [Brookhaven National Lab. (BNL), Upton, NY (United States); James, Ralph B. [Brookhaven National Lab. (BNL), Upton, NY (United States); Cui, Y. [Brookhaven National Lab. (BNL), Upton, NY (United States); De Geronimo, G. [Brookhaven National Lab. (BNL), Upton, NY (United States); Vernon, E. [Brookhaven National Lab. (BNL), Upton, NY (United States); Camarda, G. S. [Brookhaven National Lab. (BNL), Upton, NY (United States); Hossain, A. [Brookhaven National Lab. (BNL), Upton, NY (United States); Yang, G. [Brookhaven National Lab. (BNL), Upton, NY (United States); Indusi, J. [Brookhaven National Lab. (BNL), Upton, NY (United States); Boyer, Brian [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-09-30

    The goal of this project is to incorporate a Cadmium-Zinc-Telluride (CdZnTe or CZT) detector (with 1% or better resolution) into a bench-top prototype for isotope identification and related safeguards applications. The bench-top system is based on a 2x2 array of 6x6x20 mm3 position-sensitive virtual Frisch-grid (VFG) CZT detectors. The key features of the array are that it allows for the use of average-grade CZT material with a moderate content of defects, and yet it provides high energy resolution, 1% FWHM at 662 keV, large effective area, and low-power consumption. The development of this type of 3D detector and new instruments incorporating them is motivated by the high cost and low availability of large, > 1 cm3, CZT crystals suitable for making multi-pixel detectors with acceptable energy resolution and efficiency.

  12. High-Efficiency CdZnTe Position-Sensitive VFG Gamma-Ray Detectors for Safeguards Applications

    Energy Technology Data Exchange (ETDEWEB)

    Bolotnikov, Aleksey E. [Brookhaven National Lab. (BNL), Upton, NY (United States); James, Ralph B. [Brookhaven National Lab. (BNL), Upton, NY (United States); Cui, Y. [Brookhaven National Lab. (BNL), Upton, NY (United States); De Geronimo, G. [Brookhaven National Lab. (BNL), Upton, NY (United States); Vernon, E. [Brookhaven National Lab. (BNL), Upton, NY (United States); Camarda, G. S. [Brookhaven National Lab. (BNL), Upton, NY (United States); Hossain, A. [Brookhaven National Lab. (BNL), Upton, NY (United States); Yang, G. [Brookhaven National Lab. (BNL), Upton, NY (United States); Indusi, J. [Brookhaven National Lab. (BNL), Upton, NY (United States); Boyer, Brian [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-09-30

    The goal of this project is to incorporate a Cadmium-Zinc-Telluride (CdZnTe or CZT) detector (with 1% or better resolution) into a bench-top prototype for isotope identification and related safeguards applications. The bench-top system is based on a 2x2 array of 6x6x20 mm3 position-sensitive virtual Frisch-grid (VFG) CZT detectors. The key features of the array are that it allows for the use of average-grade CZT material with a moderate content of defects, and yet it provides high-energy resolution, 1% FWHM at 662 keV, large effective area, and low-power consumption. The development of this type of 3D detector and new instruments incorporating them is motivated by the high cost and low availability of large, > 1 cm3, CZT crystals suitable for making multi-pixel detectors with acceptable energy resolution and efficiency.

  13. The pixelated detector

    CERN Multimedia

    Sutton, C

    1990-01-01

    "Collecting data as patterns of light or subatomic particles is vitally important in all the sciences. The new generation of solid-state detectors called pixel devices could transform experimental research at all levels" (4 pages).

  14. Nuclear reactor pulse calibration using a CdZnTe electro-optic radiation detector

    Energy Technology Data Exchange (ETDEWEB)

    Nelson, Kyle A., E-mail: knelson1@ksu.edu [S.M.A.R.T. Laboratory, Mechanical and Nuclear Engineering, Kansas State University, Manhattan, KS 66506 (United States); Geuther, Jeffrey A. [TRIGA Mark II Nuclear Reactor, Mechanical and Nuclear Engineering, Kansas State University, Manhattan, KS 66506 (United States); Neihart, James L.; Riedel, Todd A. [S.M.A.R.T. Laboratory, Mechanical and Nuclear Engineering, Kansas State University, Manhattan, KS 66506 (United States); Rojeski, Ronald A. [Nanometrics, Inc., 1550 Buckeye Drive, Milpitas, CA 95035 (United States); Saddler, Jeffrey L. [TRIGA Mark II Nuclear Reactor, Mechanical and Nuclear Engineering, Kansas State University, Manhattan, KS 66506 (United States); Schmidt, Aaron J.; McGregor, Douglas S. [S.M.A.R.T. Laboratory, Mechanical and Nuclear Engineering, Kansas State University, Manhattan, KS 66506 (United States)

    2012-07-15

    A CdZnTe electro-optic radiation detector was used to calibrate nuclear reactor pulses. The standard configuration of the Pockels cell has collimated light passing through an optically transparent CdZnTe crystal located between crossed polarizers. The transmitted light was focused onto an IR sensitive photodiode. Calibrations of reactor pulses were performed using the CdZnTe Pockels cell by measuring the change in the photodiode current, repeated 10 times for each set of reactor pulses, set between 1.00 and 2.50 dollars in 0.50 increments of reactivity. - Highlights: Black-Right-Pointing-Pointer We demonstrated the first use of an electro-optic device to trace reactor pulses in real-time. Black-Right-Pointing-Pointer We examined the changes in photodiode current for different reactivity insertions. Black-Right-Pointing-Pointer Created a linear best fit line from the data set to predict peak pulse powers.

  15. Study of a new architecture of gamma cameras with Cd/ZnTe/CdTe semiconductors; Etude d'une nouvelle architecture de gamma camera a base de semi-conducteurs CdZnTe /CdTe

    Energy Technology Data Exchange (ETDEWEB)

    Guerin, L

    2007-11-15

    This thesis studies new semi conductors for gammas cameras in order to improve the quality of image in nuclear medicine. The chapter 1 reminds the general principle of the imaging gamma, by describing the radiotracers, the channel of detection and the types of Anger gamma cameras acquisition. The physiological, physical and technological limits of the camera are then highlighted, to better identify the needs of future gamma cameras. The chapter 2 is dedicated to a bibliographical study. At first, semi-conductors used in imaging gamma are presented, and more particularly semi-conductors CDTE and CdZnTe, by distinguishing planar detectors and monolithic pixelated detectors. Secondly, the classic collimators of the gamma cameras, used in clinical routine for the most part of between them, are described. Their geometry is presented, as well as their characteristics, their advantages and their inconveniences. The chapter 3 is dedicated to a state of art of the simulation codes dedicated to the medical imaging and the methods of reconstruction in imaging gamma. These states of art allow to introduce the software of simulation and the methods of reconstruction used within the framework of this thesis. The chapter 4 presents the new architecture of gamma camera proposed during this work of thesis. It is structured in three parts. The first part justifies the use of semiconducting detectors CdZnTe, in particular the monolithic pixelated detectors, by bringing to light their advantages with regard to the detection modules based on scintillator. The second part presents gamma cameras to base of detectors CdZnTe (prototypes or commercial products) and their associated collimators, as well as the interest of an association of detectors CdZnTe in the classic collimators. Finally, the third part presents in detail the HiSens architecture. The chapter 5 describes both software of simulation used within the framework of this thesis to estimate the performances of the Hi

  16. Extended defects in as-grown CdZnTe

    Energy Technology Data Exchange (ETDEWEB)

    Xu, L.; Bolotnikov, A.E.; Hossain, A.; Kim, K-H.; Gul, R.; Yang, G.; Camarda, G.S.; Marchini, L.; Cui, Y.; James, R.B.; Xu, Y.; Wang, T.; Jie, W.

    2010-08-01

    We characterized samples cut from different locations in as-grown CdZnTe (CZT) ingots, using Automated Infrared (IR) Transmission Microscopy and White Beam X-ray Diffraction Topography (WBXDT), to locate and identify the extended defects in them. Our goal was to define the distribution of these defects throughout the entire ingot and their effects on detectors’ performance as revealed by the pulse-height spectrum. We found the highest- and the lowest- concentration of Te inclusions, respectively, in the head and middle part of the ingot, which could serve as guidance in selecting samples. Crystals with high concentration of Te inclusions showed high leakage current and poor performance, because the accumulated charge loss around trapping centers associated with Te inclusions distorts the internal electric field, affects the carrier transport properties inside the crystal, and finally degrades the detector’s performance. In addition, other extended defects revealed by the WBXDT measurements severely reduced the detector’s performance, since they trap large numbers of electrons, leading to a low signal for the pulse-height spectrum, or none whatsoever. Finally, we fully correlated the detector’s performance with our information on the extended defects gained from both the IR- and the WBXDT-measurements.

  17. CHARACTERIZATION OF SECONDARY PHASES AND OTHER DEFECTS IN CDZNTE

    Energy Technology Data Exchange (ETDEWEB)

    Duff, M.

    2010-06-30

    Semiconducting CdZnTe or 'CZT' crystals are very suitable for use as a room temperature-based gamma radiation spectrometer. During the last decade, modifications in growth methods for CZT have significantly improved the quality of the produced crystals however there are material features that can influence the performance of these materials as radiation detectors. For example, various structural heterogeneities within the CZT crystals, such as, pipes, voids, polycrystallinity, and secondary phases (SP) can have a negative impact on the detector performance. In this study, a CZT material was grown by the modified vertical Bridgman growth (MVB) method with zone leveled growth in the absence of excess Te in the melt. Numerous SP were imaged using transmission IR at a volume % of 0.002. Samples from this material were analyzed using various analytical techniques to evaluate its electrical properties, purity and detector performance as radiation spectrometers and to determine the morphology, dimension and elemental /structural composition of one of the SP in this material. This material was found to have a high resistivity and good radiation spectrometer performance. It had SPs that were rich in calcium (Ca), carbon (C) and oxygen (O) (possibly CaCO{sub 3}) or only C and O that were 5 {micro}m or less in diameter.

  18. The X-ray response of CdZnTe

    CERN Document Server

    Owens, A; Andersson, H; Gagliardi, T; Krumrey, M; Nenonen, S; Peacock, A; Taylor, I; Troeger, L

    2002-01-01

    We report the results of a series of X-ray measurements on a 3.1 mm sup 2 , 2.5 mm thick CdZnTe detector carried out at the BESSY II and HASYLAB synchrotron radiation facilities. The detector energy response function was found to be linear over the energy range 2.3-100 keV with an average rms non-linearity of 0.6%, consistent with statistics. At room temperature, under full-area illumination, the FWHM energy resolution was 1.6 keV at 5.9 keV rising to 2.9 keV at 59.54 keV. At a reduced detector temperature of -20 deg. C, these fall to 380 and 818 eV FWHM, respectively. Under pencil beam illumination, the measured energy resolution at 2.5 keV was 360 eV FWHM rising to 1558 eV at 100 keV. By best fitting the expected resolution function to the experimental data, we derive a value for the Fano factor of (0.099+-0.02). Cooling the detector to -50 deg. C, resulted in no noticeable difference in DELTA E above 60 keV, but a 40% reduction at energies <10 keV. At 5.9 keV, the measured resolution under full-area ill...

  19. Development of CDZNTE Detectors for Low-Energy Gamma-Ray Astronomy

    Science.gov (United States)

    Gehrels, N.

    1999-01-01

    Under this grant the UC Berkeley PI, K. Hurley, joined a Goddard-led effort to develop large area, multi-pixel Cadmium-Zinc-Telluride (CdZnTe, or CZT) detectors for gamma-ray astronomy. His task was to advise the project of new developments in the area of cosmic gamma-ray bursts, in order to focus the detector development effort on the construction of an instrument which could be deployed on a spacecraft to localize and measure the energy spectra of bursts with good angular and energy resolution, respectively. UC Berkeley had no hardware role in this proposal. The result of this effort was the production, at Goddard, of five CZT prototype modules. A proposal was written for SWIFT, a MIDEX mission to study cosmic gamma-ray bursts. One experiment aboard SWIFT is the Burst Arcminute Telescope (BAT), which consists of a 5200 sq cm hard X-ray detector and a coded mask. The detector comprises 256 CZT modules, each containing 128 4 x 4 x 2 mm CZT detectors. Each detector is read out using an ASIC. The angular resolution achieved with this mask/array combination is 22 arcminutes, and a strong gamma-ray burst can be localized to an accuracy of 4 arcminutes in under 10 seconds. The energy resolution is typically 5 keV FWHM at 60 keV, and the energy range is 10 - 150 keV. The BAT views 2 steradians, and its sensitivity is such that the instrument can detect 350 gamma-ray burst/year, localizing 320 of them to better than 4 arcminute accuracy. The BAT concept therefore met the science goals for gamma-ray bursts. The UCB effort in the SWIFT proposal included the scientific objectives for gamma-ray bursts, and the assembly of a team of optical and radio observers who would use the BAT data to perform rapid multi-wavelength searches for the counterparts to bursts. This proposal was submitted to NASA and peer-reviewed. In January 1999 it was one of five such proposals selected for a Phase A study. This study was completed in June, and SWIFT was formally presented to NASA in

  20. Dike/Drift Interactions

    Energy Technology Data Exchange (ETDEWEB)

    E. Gaffiney

    2004-11-23

    This report presents and documents the model components and analyses that represent potential processes associated with propagation of a magma-filled crack (dike) migrating upward toward the surface, intersection of the dike with repository drifts, flow of magma in the drifts, and post-magma emplacement effects on repository performance. The processes that describe upward migration of a dike and magma flow down the drift are referred to as the dike intrusion submodel. The post-magma emplacement processes are referred to as the post-intrusion submodel. Collectively, these submodels are referred to as a conceptual model for dike/drift interaction. The model components and analyses of the dike/drift interaction conceptual model provide the technical basis for assessing the potential impacts of an igneous intrusion on repository performance, including those features, events, and processes (FEPs) related to dike/drift interaction (Section 6.1).

  1. A multi-technique characterization of electroless gold contacts on single crystal CdZnTe radiation detectors

    OpenAIRE

    Bell, S J; BAKER, M.A.; Chen, H.; Marthandam, P; V. Perumal; A. Schneider; Seller, P.; Sellin, P J; Veale, M C; Wilson, M. D.

    2013-01-01

    Cadmium zinc telluride (CdZnTe) is now established as a popular choice of sensor for the detection of γ-rays and hard x-rays, leading to its adoption in security, medical and scientific applications. There are still many technical challenges involving the deposition of high-quality, uniform metal contacts on CdZnTe. A detailed understanding of the interface between the bulk CdZnTe and the metal contacts is required for improvements to be made. To understand these complex interfaces, a range o...

  2. Characterization of Pixel Sensors

    CERN Document Server

    Oliveira, Felipe Ferraz

    2017-01-01

    It was commissioned at CERN ATLAS pixel group a fluorescence setup for characterization of pixel sensors. The idea is to measure the energies of different targets to calibrate your sensor. It was measured four matrices (80, 95, 98 and 106) of the Investigator1 sensor with different deep PW using copper, iron and titanium as target materials. The matrix 80 has a higher gain (0.065 ± 0.002) and matrix 106 has a better energy resolution (0.05 ± 0.04). The noise of the setup is around 3.6 mV .

  3. The analysis of X-ray response of CdZnTe detectors

    Institute of Scientific and Technical Information of China (English)

    ZHA GangQiang; XIANG Hang; LIU Ting; XU YaDong; WANG Tao; JIE WanQi

    2012-01-01

    CdZnTe is an excellent material candidate for high efficiency,high-resolution room-temperature nuclear radiation detectors,and the CdZnTe detectors are being widely used in medicine,industry,safeguard and scientific X-ray and γ-ray imaging and spectroscopic applications.In this work,three CdZnTe planar detectors with different grades,named CZT-1,CZT-2 and CZT-3,respectively,were fabricated.And the effects of mobility,lifetime and de-trapping time on the performance of CdZnTe planar detector,such as the energy rcsolution,charge collection efficiency and peak to valley ratio,were analyzed.The charge collection efficiency depends on the product of carrier mobility and lifetime,which has a great effect on the energy resolution of detector when the efficiency is less than 90%.The de-trapping time of carriers in deep levels should be responsible for the peak to valley ratio and "polarization".

  4. CdZnTe room-temperature semiconductor operation in liquid scintillator

    CERN Document Server

    Stewart, D Y

    2008-01-01

    We demonstrate the first operation of CdZnTe room-temperature detectors in a liquid scintillator environment. This work follows conceptually the Heusser-type detector method of operating HPGe detectors in liquid nitrogen and liquid argon but instead for a far more practical room-temperature ensemble with the aim of achieving ultra-low background levels for radiation detection.

  5. Study of ammonium fluoride passivation time on CdZnTe bulk crystal wafers

    Energy Technology Data Exchange (ETDEWEB)

    Bensalah, H.; Crocco, J.; Carcelen, V.; Plaza, J.L.; Zheng, Q.; Dieguez, E. [Crystal Growth Laboratory, Departamento de Fisica de Materiales, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Marchini, L. [IMEM-CNR, Parma (Italy); Zanichelli, M. [Department of Physics, University of Parma (Italy); Dominguez, G.; Soriano, L. [Departamento de Fisica Aplicada and Instituto de Ciencias de Materiales Nicolas Cabrera, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain)

    2011-07-15

    The chemical etching and the passivation processes of CdZnTe wafers were studied. The treatment effects were tested through an X-Ray Photoelectron Spectroscopy (XPS) analysis and I-V measurement. The chemical etching in 2%Br-MeOH solution may effectively remove the damaged layer and improve the ohmic contact between CdZnTe wafer and Au electrodes making rich the surface with Te. After different etching times, the CdZnTe wafers were passivated with NH{sub 4}F/H{sub 2}O{sub 2}.CdZnTe wafer passivated immediately after etching showed the best passivation efficiency because the enriched Te on the surface was fully oxidized to TeO{sub 2}, which results in the thickest oxide layer, and the most stoichiometric surface. Also the surface leakage current was reduced in comparison with the sample passivated 24 h after etching. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  6. Modeling concept drift

    DEFF Research Database (Denmark)

    Borchani, Hanen; Martinez, Ana Maria; Masegosa, Andrés R.

    2015-01-01

    An often used approach for detecting and adapting to concept drift when doing classification is to treat the data as i.i.d. and use changes in classification accuracy as an indication of concept drift. In this paper, we take a different perspective and propose a framework, based on probabilistic ...

  7. Pixel detector insertion

    CERN Multimedia

    CMS

    2015-01-01

    Insertion of the Pixel Tracker, the 66-million-channel device used to pinpoint the vertex of each colliding proton pair, located at the heart of the detector. The geometry of CMS is a cylinder lying on its side (22 meters long and 15 meters high in dia

  8. Pixel detector readout chip

    CERN Multimedia

    1991-01-01

    Close-up of a pixel detector readout chip. The photograph shows an aera of 1 mm x 2 mm containing 12 separate readout channels. The entire chip contains 1000 readout channels (around 80 000 transistors) covering a sensitive area of 8 mm x 5 mm. The chip has been mounted on a silicon detector to detect high energy particles.

  9. ALICE Silicon Pixel Detector

    CERN Multimedia

    Manzari, V

    2013-01-01

    The Silicon Pixel Detector (SPD) forms the innermost two layers of the 6-layer barrel Inner Tracking System (ITS). The SPD plays a key role in the determination of the position of the primary collision and in the reconstruction of the secondary vertices from particle decays.

  10. Image processing for drift compensation in fluorescence microscopy

    DEFF Research Database (Denmark)

    Petersen, Steffen; Thiagarajan, Viruthachalam; Coutinho, Isabel

    2013-01-01

    Fluorescence microscopy is characterized by low background noise, thus a fluorescent object appears as an area of high signal/noise. Thermal gradients may result in apparent motion of the object, leading to a blurred image. Here, we have developed an image processing methodology that may remove....../reduce blur significantly for any type of microscopy. A total of ~100 images were acquired with a pixel size of 30 nm. The acquisition time for each image was approximately 1second. We can quantity the drift in X and Y using the sub pixel accuracy computed centroid location of an image object in each frame....... We can measure drifts down to approximately 10 nm in size and a drift-compensated image can therefore be reconstructed on a grid of the same size using the “Shift and Add” approach leading to an image of identical size asthe individual image. We have also reconstructed the image using a 3 fold larger...

  11. Synthesis and fluorescence properties of water-soluble CdZnTe quantum dots%水溶性 CdZnTe 量子点制备及光谱性能

    Institute of Scientific and Technical Information of China (English)

    陈燕清; 龙冠虹

    2014-01-01

    以巯基丙酸(MPA)为修饰剂,在水溶液中制备出 CdZnTe 量子点(QDs)。研究了 ZnCd 摩尔比,pH,反应时间等因素对 CdZnTe 量子点荧光性能的影响。为了进一步改善 CdZnTe 量子点的水溶性,采用聚乙烯亚胺(PEI)对 CdZnTe 量子点进一步进行包裹,探讨了前驱体溶液 pH 对 PEI 包裹 CdZnTe 量子点荧光性能的影响。相比于 CdTe 量子点,CdZnTe 量子点具有更强的荧光性能,PEI 修饰的 CdZnTe 量子点的稳定性更好。通过荧光光谱仪,红外光谱仪,X-射线粉末衍射仪,透射电镜对所制得量子点进行了表征。%Water-soluble CdZnTe quantum dots (QDs)were synthesized in aqueous solution by using mer-captopropionic acid (MPA)as stabilizer.The influence of the molar ratio of CdZn,pHand aging time on photoluminescence of obtained QDs had been studied.To further improve the solubility of CdZnTe QDs, surfaces of water-soluble quantum dots were modified by polyethyleneimine (PEI),and the effect of pH on CdZnTe QDs coated with PEI was discussed as well.CdZnTe QDs acquired better photoluminescence and decreased biological toxicity compared with CdTe QDs.The modification using PEI highly enhanced the lu-minescent property of CdZnTe QDs.The water-soluble CdZnTe QDs were characterized by fluorescence e-mission spectra,infrared spectra (IR),transmission electron microscopy (TEM),and X-ray powder diffrac-tion (XRD).

  12. Abstraction of Drift Seepage

    Energy Technology Data Exchange (ETDEWEB)

    J.T. Birkholzer

    2004-11-01

    This model report documents the abstraction of drift seepage, conducted to provide seepage-relevant parameters and their probability distributions for use in Total System Performance Assessment for License Application (TSPA-LA). Drift seepage refers to the flow of liquid water into waste emplacement drifts. Water that seeps into drifts may contact waste packages and potentially mobilize radionuclides, and may result in advective transport of radionuclides through breached waste packages [''Risk Information to Support Prioritization of Performance Assessment Models'' (BSC 2003 [DIRS 168796], Section 3.3.2)]. The unsaturated rock layers overlying and hosting the repository form a natural barrier that reduces the amount of water entering emplacement drifts by natural subsurface processes. For example, drift seepage is limited by the capillary barrier forming at the drift crown, which decreases or even eliminates water flow from the unsaturated fractured rock into the drift. During the first few hundred years after waste emplacement, when above-boiling rock temperatures will develop as a result of heat generated by the decay of the radioactive waste, vaporization of percolation water is an additional factor limiting seepage. Estimating the effectiveness of these natural barrier capabilities and predicting the amount of seepage into drifts is an important aspect of assessing the performance of the repository. The TSPA-LA therefore includes a seepage component that calculates the amount of seepage into drifts [''Total System Performance Assessment (TSPA) Model/Analysis for the License Application'' (BSC 2004 [DIRS 168504], Section 6.3.3.1)]. The TSPA-LA calculation is performed with a probabilistic approach that accounts for the spatial and temporal variability and inherent uncertainty of seepage-relevant properties and processes. Results are used for subsequent TSPA-LA components that may handle, for example, waste package

  13. Preliminary test of an imaging probe for nuclear medicine using hybrid pixel detectors

    CERN Document Server

    Bertolucci, Ennio; Mettivier, G; Montesi, M C; Russo, P

    2002-01-01

    We are investigating the feasibility of an intraoperative imaging probe for lymphoscintigraphy with Tc-99m tracer, for sentinel node radioguided surgery, using the Medipix series of hybrid detectors coupled to a collimator. These detectors are pixelated semiconductor detectors bump-bonded to the Medipix1 photon counting read-out chip (64x64 pixel, 170 mu m pitch) or to the Medipix2 chip (256x256 pixel, 55 mu m pitch), developed by the European Medipix collaboration. The pixel detector we plan to use in the final version of the probe is a semi-insulating GaAs detector or a 1-2 mm thick CdZnTe detector. For the preliminary tests presented here, we used 300-mu m thick silicon detectors, hybridized via bump-bonding to the Medipix1 chip. We used a tungsten parallel-hole collimator (7 mm thick, matrix array of 64x64 100 mu m circular holes with 170 mu m pitch), and a 22, 60 and 122 keV point-like (1 mm diameter) radioactive sources, placed at various distances from the detector. These tests were conducted in order ...

  14. The Drift Burst Hypothesis

    DEFF Research Database (Denmark)

    Christensen, Kim; Oomen, Roel; Renò, Roberto

    The Drift Burst Hypothesis postulates the existence of short-lived locally explosive trends in the price paths of financial assets. The recent US equity and Treasury flash crashes can be viewed as two high profile manifestations of such dynamics, but we argue that drift bursts of varying magnitude......, currencies and commodities. We find that the majority of identified drift bursts are accompanied by strong price reversals and these can therefore be regarded as “flash crashes” that span brief periods of severe market disruption without any material longer term price impacts....

  15. Drift in Diffusion Gradients

    Directory of Open Access Journals (Sweden)

    Fabio Marchesoni

    2013-08-01

    Full Text Available The longstanding problem of Brownian transport in a heterogeneous quasi one-dimensional medium with space-dependent self-diffusion coefficient is addressed in the overdamped (zero mass limit. A satisfactory mesoscopic description is obtained in the Langevin equation formalism by introducing an appropriate drift term, which depends on the system macroscopic observables, namely the diffuser concentration and current. The drift term is related to the microscopic properties of the medium. The paradoxical existence of a finite drift at zero current suggests the possibility of designing a Maxwell demon operating between two equilibrium reservoirs at the same temperature.

  16. ATLAS ITk Pixel detector

    CERN Document Server

    Gemme, Claudia; The ATLAS collaboration

    2016-01-01

    The high luminosity upgrade of the LHC (HL-LHC) in 2026 will provide new challenge to the ATLAS tracker. The current inner detector will be replaced with a whole silicon tracker which will consist of a five barrel layer Pixel detector surrounded by a four barrel layer Strip detector. The expected high radiation level are requiring the development of upgraded silicon sensors as well as new a front-end chip. The dense tracking environment will require finer granularity detectors. The data rates will require new technologies for high bandwidth data transmission and handling. The current status of the HL-LHC ATLA Pixel detector developments as well as the various layout options will be reviewed.

  17. Alpine Pixel Detector Layout

    CERN Document Server

    Delebecque, P; The ATLAS collaboration; Geffroy, N; Massol, N; Rambure, T; Todorov, T

    2013-01-01

    A description of an optimized layout of pixel sensors based on a stave that combines both barrel and endcap module orientations. The mechanical stiffness of the structure is provided by carbon fiber shells spaced by carbon foam. The cooling of the modules is provided by two-phase $CO_{2}$ flowing in a thin titanium pipe glued inside the carbon fiber foam. The electrical services of all modules are provided by a single stave flex. This layout eliminates the need for separate barrel and endcap detector structures, and therefore the barrel services material in front of the endcap. The transition from barrel to endcap module orientation is optimized separately for each layer in order to minimize the active pixel area and the traversed material. The sparse module spacing in the endcap part of the stave allows for multiple fixation points, and for a stiff overall structure composed only of staves interconnected by stiff disks.

  18. The Belle II DEPFET pixel detector

    Energy Technology Data Exchange (ETDEWEB)

    Moser, Hans-Günther, E-mail: moser@mpp.mpg.de

    2016-09-21

    The Belle II experiment at KEK (Tsukuba, Japan) will explore heavy flavour physics (B, charm and tau) at the starting of 2018 with unprecedented precision. Charged particles are tracked by a two-layer DEPFET pixel device (PXD), a four-layer silicon strip detector (SVD) and the central drift chamber (CDC). The PXD will consist of two layers at radii of 14 mm and 22 mm with 8 and 12 ladders, respectively. The pixel sizes will vary, between 50 μm×(55–60) μm in the first layer and between 50 μm×(70–85) μm in the second layer, to optimize the charge sharing efficiency. These innermost layers have to cope with high background occupancy, high radiation and must have minimal material to reduce multiple scattering. These challenges are met using the DEPFET technology. Each pixel is a FET integrated on a fully depleted silicon bulk. The signal charge collected in the ‘internal gate’ modulates the FET current resulting in a first stage amplification and therefore very low noise. This allows very thin sensors (75 μm) reducing the overall material budget of the detector (0.21% X{sub 0}). Four fold multiplexing of the column parallel readout allows read out a full frame of the pixel matrix in only 20 μs while keeping the power consumption low enough for air cooling. Only the active electronics outside the detector acceptance has to be cooled actively with a two phase CO{sub 2} system. Furthermore the DEPFET technology offers the unique feature of an electronic shutter which allows the detector to operate efficiently in the continuous injection mode of superKEKB.

  19. The Belle II DEPFET pixel detector

    Science.gov (United States)

    Moser, Hans-Günther

    2016-09-01

    The Belle II experiment at KEK (Tsukuba, Japan) will explore heavy flavour physics (B, charm and tau) at the starting of 2018 with unprecedented precision. Charged particles are tracked by a two-layer DEPFET pixel device (PXD), a four-layer silicon strip detector (SVD) and the central drift chamber (CDC). The PXD will consist of two layers at radii of 14 mm and 22 mm with 8 and 12 ladders, respectively. The pixel sizes will vary, between 50 μm×(55-60) μm in the first layer and between 50 μm×(70-85) μm in the second layer, to optimize the charge sharing efficiency. These innermost layers have to cope with high background occupancy, high radiation and must have minimal material to reduce multiple scattering. These challenges are met using the DEPFET technology. Each pixel is a FET integrated on a fully depleted silicon bulk. The signal charge collected in the 'internal gate' modulates the FET current resulting in a first stage amplification and therefore very low noise. This allows very thin sensors (75 μm) reducing the overall material budget of the detector (0.21% X0). Four fold multiplexing of the column parallel readout allows read out a full frame of the pixel matrix in only 20 μs while keeping the power consumption low enough for air cooling. Only the active electronics outside the detector acceptance has to be cooled actively with a two phase CO2 system. Furthermore the DEPFET technology offers the unique feature of an electronic shutter which allows the detector to operate efficiently in the continuous injection mode of superKEKB.

  20. Silicon drift detector with reduced lateral diffusion: experimental results

    CERN Document Server

    Sonsky, J; Huizenga, John R; Hollander, R W; Eijk, C W E; Sarro, P M

    2000-01-01

    In a standard multi-anode silicon drift detector electron cloud broadening during the drifting towards the anode pixels deteriorates the energy and position resolution. This makes the detector less applicable for detection of low-energy X-rays. The signal charge sharing between several anodes can be eliminated by introducing sawtooth-shaped p sup + field strips. The sawtooth structure results in small electric fields directed parallel to the sensor surface and perpendicular to the drift direction which produce gutters. The drifting electrons are confined in these gutters of one saw tooth period wide. For a detector with a sawtooth period of 500 mu m, we have measured the maximum number of fully confined electrons as a function of the potential gutter depth induced by different sawtooth angles.

  1. The detection of single electrons using a Microgas gas amplification and a MediPix2 CMOS pixel readout

    NARCIS (Netherlands)

    Forniani, A.; Campbell, M.; Chefdeville, M.A.; Colas, P.; Colijn, A.P.; Graaf, van der H.; Giomataris, Y.; Heijne, E.H.M.; Kluit, P.; Llopart, X.; Schmitz, J.; Timmermans, J.; Visschers, J.L.

    2005-01-01

    By placing a Micromegas gas gain grid on top of a CMOS pixel readout circuit (MediPix2), we developed a device which acts as a pixel-segmented direct anode in gas-filled detectors. With a He/Isobutane 80/20 mixture (capable of achieving gas gain factors up to 20×103) and employing a drift length of

  2. 3D track reconstruction capability of a silicon hybrid active pixel detector

    Science.gov (United States)

    Bergmann, Benedikt; Pichotka, Martin; Pospisil, Stanislav; Vycpalek, Jiri; Burian, Petr; Broulim, Pavel; Jakubek, Jan

    2017-06-01

    Timepix3 detectors are the latest generation of hybrid active pixel detectors of the Medipix/Timepix family. Such detectors consist of an active sensor layer which is connected to the readout ASIC (application specific integrated circuit), segmenting the detector into a square matrix of 256 × 256 pixels (pixel pitch 55 μm). Particles interacting in the active sensor material create charge carriers, which drift towards the pixelated electrode, where they are collected. In each pixel, the time of the interaction (time resolution 1.56 ns) and the amount of created charge carriers are measured. Such a device was employed in an experiment in a 120 GeV/c pion beam. It is demonstrated, how the drift time information can be used for "4D" particle tracking, with the three spatial dimensions and the energy losses along the particle trajectory (dE/dx). Since the coordinates in the detector plane are given by the pixelation ( x, y), the x- and y-resolution is determined by the pixel pitch (55 μm). A z-resolution of 50.4 μm could be achieved (for a 500 μm thick silicon sensor at 130 V bias), whereby the drift time model independent z-resolution was found to be 28.5 μm.

  3. Drift Scale THM Model

    Energy Technology Data Exchange (ETDEWEB)

    J. Rutqvist

    2004-10-07

    This model report documents the drift scale coupled thermal-hydrological-mechanical (THM) processes model development and presents simulations of the THM behavior in fractured rock close to emplacement drifts. The modeling and analyses are used to evaluate the impact of THM processes on permeability and flow in the near-field of the emplacement drifts. The results from this report are used to assess the importance of THM processes on seepage and support in the model reports ''Seepage Model for PA Including Drift Collapse'' and ''Abstraction of Drift Seepage'', and to support arguments for exclusion of features, events, and processes (FEPs) in the analysis reports ''Features, Events, and Processes in Unsaturated Zone Flow and Transport and Features, Events, and Processes: Disruptive Events''. The total system performance assessment (TSPA) calculations do not use any output from this report. Specifically, the coupled THM process model is applied to simulate the impact of THM processes on hydrologic properties (permeability and capillary strength) and flow in the near-field rock around a heat-releasing emplacement drift. The heat generated by the decay of radioactive waste results in elevated rock temperatures for thousands of years after waste emplacement. Depending on the thermal load, these temperatures are high enough to cause boiling conditions in the rock, resulting in water redistribution and altered flow paths. These temperatures will also cause thermal expansion of the rock, with the potential of opening or closing fractures and thus changing fracture permeability in the near-field. Understanding the THM coupled processes is important for the performance of the repository because the thermally induced permeability changes potentially effect the magnitude and spatial distribution of percolation flux in the vicinity of the drift, and hence the seepage of water into the drift. This is important because

  4. Pixelated neutron image plates

    Science.gov (United States)

    Schlapp, M.; Conrad, H.; von Seggern, H.

    2004-09-01

    Neutron image plates (NIPs) have found widespread application as neutron detectors for single-crystal and powder diffraction, small-angle scattering and tomography. After neutron exposure, the image plate can be read out by scanning with a laser. Commercially available NIPs consist of a powder mixture of BaFBr : Eu2+ and Gd2O3 dispersed in a polymer matrix and supported by a flexible polymer sheet. Since BaFBr : Eu2+ is an excellent x-ray storage phosphor, these NIPs are particularly sensitive to ggr-radiation, which is always present as a background radiation in neutron experiments. In this work we present results on NIPs consisting of KCl : Eu2+ and LiF that were fabricated into ceramic image plates in which the alkali halides act as a self-supporting matrix without the necessity for using a polymeric binder. An advantage of this type of NIP is the significantly reduced ggr-sensitivity. However, the much lower neutron absorption cross section of LiF compared with Gd2O3 demands a thicker image plate for obtaining comparable neutron absorption. The greater thickness of the NIP inevitably leads to a loss in spatial resolution of the image plate. However, this reduction in resolution can be restricted by a novel image plate concept in which a ceramic structure with square cells (referred to as a 'honeycomb') is embedded in the NIP, resulting in a pixelated image plate. In such a NIP the read-out light is confined to the particular illuminated pixel, decoupling the spatial resolution from the optical properties of the image plate material and morphology. In this work, a comparison of experimentally determined and simulated spatial resolutions of pixelated and unstructured image plates for a fixed read-out laser intensity is presented, as well as simulations of the properties of these NIPs at higher laser powers.

  5. The Kepler Pixel Response Function

    CERN Document Server

    Bryson, Stephen T; Jenkins, Jon M; Chandrasekaran, Hema; Klaus, Todd; Caldwell, Douglas A; Gilliland, Ronald L; Haas, Michael R; Dotson, Jessie L; Koch, David G; Borucki, William J

    2010-01-01

    Kepler seeks to detect sequences of transits of Earth-size exoplanets orbiting Solar-like stars. Such transit signals are on the order of 100 ppm. The high photometric precision demanded by Kepler requires detailed knowledge of how the Kepler pixels respond to starlight during a nominal observation. This information is provided by the Kepler pixel response function (PRF), defined as the composite of Kepler's optical point spread function, integrated spacecraft pointing jitter during a nominal cadence and other systematic effects. To provide sub-pixel resolution, the PRF is represented as a piecewise-continuous polynomial on a sub-pixel mesh. This continuous representation allows the prediction of a star's flux value on any pixel given the star's pixel position. The advantages and difficulties of this polynomial representation are discussed, including characterization of spatial variation in the PRF and the smoothing of discontinuities between sub-pixel polynomial patches. On-orbit super-resolution measurement...

  6. ATLAS-IBL Pixel Upgrade

    CERN Document Server

    LaRosa, A; The ATLAS collaboration

    2010-01-01

    The upgrade for the ATLAS detector will undergo different phase towards Super-LHC. The first upgrade for the Pixel Detector will consist in the construction of a new pixel layer which will be installed during the first shutdown of the LHC machine (SLHC Phase I). The new detector, called Insertable B-Layer (IBL), will be inserted between the existing pixel detector and a new (smaller radius) beam-pipe at a radius of 3.2 cm. The IBL will require the development of several new technologies to cope with increase of radiation or pixel occupancy and also to improve the physics performance which will be achieved by reduction of the pixel size and of the material budget. Three different promising sensor technologies (Planar-Si, 3D-Si and Diamond) are currently under investigation for the pixel detector. An overview of the project with particular emphasis on pixel module studies, irradiation and beam test plans will be presented.

  7. Monolithic pixels on moderate resistivity substrate and sparsifying readout architecture

    CERN Document Server

    Giubilato, P; Snoeys, W; Bisello, D; Marchioro, A; Battaglia, M; Demaria, L; Mansuy, S C; Pantano, D; Rousset, J; Mattiazzo, S; Kloukinas, K; Potenza, A; Ikemoto, Y; Rivetti, A; Chalmet, P; Mugnier, H; Silvestrin, L

    2013-01-01

    The LePix projects aim realizing a new generation monolithic pixel detectors with improved performances at lesser cost with respect to both current state of the art monolithic and hybrid pixel sensors. The detector is built in a 90 nm CMOS process on a substrate of moderate resistivity. This allows charge collection by drift while maintaining the other advantages usually offered by MAPS, like having a single piece detector and using a standard CMOS production line. The collection by drift mechanism, coupled to the low capacitance design of the collecting node made possible by the monolithic approach, provides an excellent signal to noise ratio straight at the pixel cell together with a radiation tolerance far superior to conventional un-depleted MAPS. The excellent signal-to-noise performance is demonstrated by the device ability to separate the 6 keV Fe-55 double peak at room temperature. To achieve high granularity (10-20 mu m pitch pixels) over large detector areas maintaining high readout speed, a complet...

  8. High performance p-i-n CdTe and CdZnTe detectors

    CERN Document Server

    Khusainov, A K; Ilves, A G; Morozov, V F; Pustovoit, A K; Arlt, R D

    1999-01-01

    A breakthrough in the performance of p-i-n CdTe and CdZnTe detectors is reported. The detector stability has been significantly improved, allowing their use in precise gamma and XRF applications. Detectors with energy resolution close to Si and Ge were produced operating with only -30--35 deg. C cooling (by a Peltier cooler of 15x15x10 mm size and a consumed power less than 5 W). Presently detectors with volume of up to 300 mm sup 3 are available. In terms of photoelectric effect efficiency it corresponds to HPGe detectors with volumes of about 1.5 cm sup 3. The possibilities of further improvement of CdTe and CdZnTe detector characteristics are discussed in this paper.

  9. A test device for isotopic γ-ray imaging with CdZnTe detector

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A test device for isotopic γ-ray imaging, which consists of an isotope γ-ray source, a CdZnTe γ-ray spectrometer and other auxiliary equipment, is studied here. Compared with the conventional X-ray, the isotope γ-ray,which is utilized in this project, has its own advantages in imaging. Furthermore, with a room-temperature high-energy-resolution CdZnTe detector and a modern imaging processing technique, this device is capable of effectively suppressing the background and gaining more information, thus it can obtain a better image than conventional X-ray devices. In the experiment of PCB imaging, all soldered points and chip components are sharply demonstrated.

  10. Characterization of a large CdZnTe coplanar quad-grid semiconductor detector

    CERN Document Server

    Ebert, Joachim; Gehre, Daniel; Hagner, Caren; Heidrich, Nadine; Klingenberg, Rainer; Kröninger, Kevin; Nitsch, Christian; Oldorf, Christian; Quante, Thomas; Rajek, Silke; Rebber, Henning; Rohatsch, Katja; Tebrügge, Jan; Temminghoff, Robert; Theinert, Robert; Timm, Jan; Wonsak, Björn; Zatschler, Stefan; Zuber, Kai

    2015-01-01

    The COBRA collaboration aims to search for neutrinoless double beta-decay of $^{116}$Cd. A demonstrator setup with 64 CdZnTe semiconductor detectors, each with a volume of 1cm$^3$, is currently being operated at the LNGS underground laboratory in Italy. This paper reports on the characterization of a large (2 $\\times$ 2 $\\times$ 1.5)cm$^3$ CdZnTe detector with a new coplanar-grid design for applications in $\\gamma$-ray spectroscopy and low-background operation. Several studies of electric properties as well as of the spectrometric performance, like energy response and resolution, are conducted. Furthermore, measurements including investigating the operational stability and a possibility to identify multiple-scattered photons are presented.

  11. Surface morphology study on CdZnTe crystals by atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Azoulay, M.; George, M.A.; Burger, A.; Collins, W.E.; Silberman, E. [Fisk Univ., Nashville, TN (United States)

    1993-03-01

    The study of the crystal surface morphology of CdZnTe is important for the understanding of the fundamentals of crystal growth in order to improve the crystal quality which is essential in applications such as substrates for epitaxy or performance of devices, i.e., room temperature nuclear spectrometers. We present a first atomic force microscopy study on CdZnTe. Cleaved (110) surfaces were imaged in the ambient and an atomic layer step structure was revealed. The effects of thermal annealing on the atomic steps together with Te precipitation along these steps are discussed in terms of deformation due to stress relief and the diffusion of tellurium precipitates. 12 refs., 3 figs.

  12. Drift Degradation Analysis

    Energy Technology Data Exchange (ETDEWEB)

    D. Kicker

    2004-09-16

    Degradation of underground openings as a function of time is a natural and expected occurrence for any subsurface excavation. Over time, changes occur to both the stress condition and the strength of the rock mass due to several interacting factors. Once the factors contributing to degradation are characterized, the effects of drift degradation can typically be mitigated through appropriate design and maintenance of the ground support system. However, for the emplacement drifts of the geologic repository at Yucca Mountain, it is necessary to characterize drift degradation over a 10,000-year period, which is well beyond the functional period of the ground support system. This document provides an analysis of the amount of drift degradation anticipated in repository emplacement drifts for discrete events and time increments extending throughout the 10,000-year regulatory period for postclosure performance. This revision of the drift degradation analysis was developed to support the license application and fulfill specific agreement items between the U.S. Nuclear Regulatory Commission (NRC) and the U.S. Department of Energy (DOE). The earlier versions of ''Drift Degradation Analysis'' (BSC 2001 [DIRS 156304]) relied primarily on the DRKBA numerical code, which provides for a probabilistic key-block assessment based on realistic fracture patterns determined from field mapping in the Exploratory Studies Facility (ESF) at Yucca Mountain. A key block is defined as a critical block in the surrounding rock mass of an excavation, which is removable and oriented in an unsafe manner such that it is likely to move into an opening unless support is provided. However, the use of the DRKBA code to determine potential rockfall data at the repository horizon during the postclosure period has several limitations: (1) The DRKBA code cannot explicitly apply dynamic loads due to seismic ground motion. (2) The DRKBA code cannot explicitly apply loads due to thermal

  13. Growth of CdZnTe Crystals for Radiation Detector Applications by Directional Solidification

    Science.gov (United States)

    Su, Ching-Hua

    2014-01-01

    Advances in Cadmium Zinc Telluride (Cd(sub 1-x)Zn(sub x)Te) growth techniques are needed for the production of large-scale arrays of gamma and x-ray astronomy. The research objective is to develop crystal growth recipes and techniques to obtain large, high quality CdZnTe single crystal with reduced defects, such as charge trapping, twinning, and tellurium precipitates, which degrade the performance of CdZnTe and, at the same time, to increase the yield of usable material from the CdZnTe ingot. A low gravity material experiment, "Crystal Growth of Ternary Compound Semiconductors in Low Gravity Environment", will be performed in the Material Science Research Rack (MSRR) on International Space Station (ISS). One section of the flight experiment is the melt growth of CdZnTe ternary compounds. This talk will focus on the ground-based studies on the growth of Cd(sub 0.80)Zn(sub 0.20)Te crystals for radiation detector applications by directional solidification. In this investigation, we have improved the properties that are most critical for the detector applications (electrical properties and crystalline quality): a) Electrical resistivity: use high purity starting materials (with reproducible impurity levels) and controlled Cd over pressure during growth to reproducibly balance the impurity levels and Cd vacancy concentration b) Crystalline quality: use ultra-clean growth ampoule (no wetting after growth), optimized thermal profile and ampoule design, as well as a technique for supercool reduction to growth large single crystal with high crystalline quality

  14. CdZnTe gamma ray spectrometer for orbital planetary missions

    Energy Technology Data Exchange (ETDEWEB)

    Feldman, W. C. (William C.); Storms, S. A. (Steven A.); Fuller, K. R. (Kenneth R.); Moss, C. E. (Calvin E.); Browne, M. C. (Michael C.); Lawrence, David J. (David Jeffery),; Ianakiev, K. D.; Prettyman, T. H. (Thomas H.)

    2001-01-01

    Knowledge of surface elemental composition is needed to understand the formation and evolution of planetary bodies. Gamma rays and neutrons produced by the interaction of galactic cosmic rays with surface materials can be detected from orbit and analyzed to determine composition. Using gamma ray spectroscopy, major rock forming elements such as Fe, Ti, Al, Si, Mg, and Ca can be detected. The accuracy of elemental abundance is limited by the resolution of the spectrometer. For space missions, scintillators such as BGO and NaI(Tl) have been used for gamma ray spectroscopy. New planetary science missions are being planned to explore Mars, Mercury, the asteroid belt, and the outer planets. Significant improvements in the pulse height resolution relative to scintillation detectors can be made using CdZnTe, a new room temperature detector technology. For an orbiting instrument, a CdZnTe detector at least 16 cm{sup 3} in size is needed. A 4 x 4 array of 1-cm{sup 3} coplanar grid detectors can be manufactured that meets requirements for resolution and counting efficiency. The array will shielded from gamma rays produced in the spacecraft by a BGO detector. By improving pulse height resolution by a factor of three at low energy, the CdZnTe detector will be able to make accurate measurements of elements that are currently difficult to measure using scintillation technology. The BGO shield will provide adequate suppression of gamma rays originating in the spacecraft, enabling the gamma ray spectrometer to be mounted on the deck of a spacecraft. To test this concept, we are constructing a flight qualified, prototype CdZnTe detector array. The prototype consists of a 2 x 2 array of coplanar grid detectors. We will present the results of mechanical and electronic testing and radiation damage tests, and the performance of the array for gamma ray spectroscopy.

  15. Charge-sensitive front-end electronics with operational amplifiers for CdZnTe detectors

    OpenAIRE

    Födisch, P.; Berthel, M.; Lange, B; Kirschke, T.; Enghardt, W.; Kaever, P.

    2016-01-01

    Cadmium zinc telluride (CdZnTe, CZT) radiation detectors are suitable for a variety of applications, due to their high spatial resolution and spectroscopic energy performance at room temperature. However, state-of-the-art detector systems require high-performance readout electronics. Though an application-specific integrated circuit (ASIC) is an adequate solution for the readout, requirements of high dynamic range and high throughput are not available in any commercial circuit. Consequently, ...

  16. SAA drift: Experimental results

    Science.gov (United States)

    Grigoryan, O. R.; Romashova, V. V.; Petrov, A. N.

    According to the paleomagnetic analysis there are variations of Earth’s magnetic field connected with magnetic moment changing. These variations affect on the South Atlantic Anomaly (SAA) location. Indeed different observations approved the existence of the SAA westward drift rate (0.1 1.0 deg/year) and northward drift rate (approximately 0.1 deg/year). In this work, we present the analysis of experimental results obtained in Scobeltsyn Institute of Nuclear Physics, Moscow State University (SINP MSU) onboard different Earth’s artificial satellites (1972 2003). The fluxes of protons with energy >50 MeV, gamma quanta with energy >500 keV and neutrons with energy 0.1 1.0 MeV in the SAA region have been analyzed. The mentioned above experimental data were obtained onboard the orbital stations Salut-6 (1979), MIR (1991, 1998) and ISS (2003) by the similar experimental equipment. The comparison of the data obtained during these two decades of investigations confirms the fact that the SAA drifts westward. Moreover the analysis of fluxes of electrons with energy about hundreds keV (Cosmos-484 (1972) and Active (Interkosmos-24, 1991) satellites) verified not only the SAA westward drift but northward drift also.

  17. Research of CdZnTe detector based portable energy dispersive spectrometer

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    A kind of excellent CdZnTe crystal has been grown in Yinnel Tech, Inc. in recent years. Based on these CdZnTe crystals and some new techniques, a portable energy-dispersive spectrometer has been constructed which has yielded good results. CdZnTe detector has a 3% relative resolution in high-energy field and can detect gamma rays at room temperature. An integrated circuit based on preamplifier and shaping amplifier chips is connected to the detector.Voltage pulses are transformed into digital signals in MCA (multichannel analyzer) and are then transmitted to computer via USB bus. Data process algorithms are improved in this spectrometer. Fast Fourier transform (FFT) and numerical differentiation (ND) are used in energy peak's searching program. Sampling-based correction technique is used in X-ray energy calibration. Modified Gaussian-Newton algorithm is a classical method to solve nonlinear curve fitting problems, and it is used to compute absolute intensity of each detected characteristic line.

  18. Nanomechanical behaviors of (110) and (111) CdZnTe crystals investigated by nanoindentation

    Institute of Scientific and Technical Information of China (English)

    LI Yan; KANG Renke; GAO Hang; WANG Jinghe; LANG Yanju

    2009-01-01

    The nanomechanical behaviors of (110) and (111) CdZnTe crystals were investigated by nanoindentation. It was found that the indenter tip was adhered by the removed materials in scanning testing area although the scanning force on the tested surface was very small (1000 nN), which would affect the testing result of nanoindentation, so the indenter was clean before nanoindentation test. The experimemtal results showed that the hardness and Young's modulus decreased with the increase of indentation loads on the same plane. Because of the anisot-ropy of the CdZnTe crystal, the average hardness of (110) plane is 35% lower than that of (l 11 ) plane, and there are about 30% difference of the hardness along different crystallographic directions on the same plane. The hardness in 0° and 120° testing directions was the same due to the threefold symmetry of a Berkovich indenter. And the anisotropy affected the surface quality during machining of CdZnTe crystal.

  19. MTF study of planar small pixel pitch quantum IR detectors

    Science.gov (United States)

    Gravrand, O.; Baier, N.; Ferron, A.; Rochette, F.; Berthoz, J.; Rubaldo, L.; Cluzel, R.

    2014-06-01

    The actual trend in quantum IR detector development is the design of very small pixel pitch large arrays. From previously 30μm pitch, the standard pixel pitch is today 15μm and is expected to decrease to 12μm in the next few years. Furthermore, focal plane arrays (FPA) with pixel pitch as small as small as 10μm has been demonstrated. Such ultra-small pixel pitches are very small compared to the typical length ruling the electrical characteristics of the absorbing materials, namely the minority carrier diffusion length. As an example for low doped N type HgCdTe or InSb material, this diffusion length is of the order of 30 to 50μm, i.e. 3 to 5 times the targeted pixel pitches. This has strong consequences on the modulation transfer function (MTF) for planar structures, where the lateral extension of the photodiode is limited by diffusion. For such aspect ratios, the self-confinement of neighboring diodes may not be efficient enough to maintain optimal MTF. Therefore, this issue has to be addressed in order to take full benefits of the pixel pitch reduction in terms of image resolution. This paper aims at investigating the MTF evolution of HgCdTe and InSb FPAs decreasing the pixel pitch below 15μm. Both experimental measurements and finite element simulations are used to discuss this issue. Different scenarii will be compared, namely deep mesa etch between pixels, internal drift, surface recombination, thin absorbing layers.

  20. The ALICE pixel detector

    CERN Document Server

    Mercado Perez, J

    2002-01-01

    The present document is a brief summary of the performed activities during the 2001 Summer Student Programme at CERN under the Scientific Summer at Foreign Laboratories Program organized by the Particles and Fields Division of the Mexican Physical Society (Sociedad Mexicana de Fisica). In this case, the activities were related with the ALICE Pixel Group of the EP-AIT Division, under the supervision of Jeroen van Hunen, research fellow in this group. First, I give an introduction and overview to the ALICE experiment; followed by a description of wafer probing. A brief summary of the test beam that we had from July 13th to July 25th is given as well. (3 refs).

  1. Pixelated gamma detector

    Energy Technology Data Exchange (ETDEWEB)

    Dolinsky, Sergei Ivanovich; Yanoff, Brian David; Guida, Renato; Ivan, Adrian

    2016-12-27

    A pixelated gamma detector includes a scintillator column assembly having scintillator crystals and optical transparent elements alternating along a longitudinal axis, a collimator assembly having longitudinal walls separated by collimator septum, the collimator septum spaced apart to form collimator channels, the scintillator column assembly positioned adjacent to the collimator assembly so that the respective ones of the scintillator crystal are positioned adjacent to respective ones of the collimator channels, the respective ones of the optical transparent element are positioned adjacent to respective ones of the collimator septum, and a first photosensor and a second photosensor, the first and the second photosensor each connected to an opposing end of the scintillator column assembly. A system and a method for inspecting and/or detecting defects in an interior of an object are also disclosed.

  2. Planar Pixelations and Image Recognition

    CERN Document Server

    Rowekamp, Brandon

    2011-01-01

    Any subset of the plane can be approximated by a set of square pixels. This transition from a shape to its pixelation is rather brutal since it destroys geometric and topological information about the shape. Using a technique inspired by Morse Theory, we algorithmically produce a PL approximation of the original shape using only information from its pixelation. This approximation converges to the original shape in a very strong sense: as the size of the pixels goes to zero we can recover important geometric and topological invariants of the original shape such as Betti numbers, area, perimeter and curvature measures.

  3. Negative Drift in Populations

    DEFF Research Database (Denmark)

    Lehre, Per Kristian

    2011-01-01

    An important step in gaining a better understanding of the stochastic dynamics of evolving populations, is the development of appropriate analytical tools. We present a new drift theorem for populations that allows properties of their long-term behaviour, e.g. the runtime of evolutionary algorithms...

  4. IN DRIFT CORROSION PRODUCTS

    Energy Technology Data Exchange (ETDEWEB)

    D.M. Jolley

    1999-12-02

    As directed by a written development plan (CRWMS M&O 1999a), a conceptual model for steel and corrosion products in the engineered barrier system (EBS) is to be developed. The purpose of this conceptual model is to assist Performance Assessment Operations (PAO) and its Engineered Barrier Performance Department in modeling the geochemical environment within a repository drift, thus allowing PAO to provide a more detailed and complete in-drift geochemical model abstraction and to answer the key technical issues (KTI) raised in the NRC Issue Resolution Status Report (IRSR) for the Evolution of the Near-Field Environment (NFE) Revision 2 (NRC 1999). This document provides the conceptual framework for the in-drift corrosion products sub-model to be used in subsequent PAO analyses including the EBS physical and chemical model abstraction effort. This model has been developed to serve as a basis for the in-drift geochemical analyses performed by PAO. However, the concepts discussed within this report may also apply to some near and far-field geochemical processes and may have conceptual application within the unsaturated zone (UZ) and saturated zone (SZ) transport modeling efforts.

  5. Development of drifting buoys

    Digital Repository Service at National Institute of Oceanography (India)

    Nayak, M.R.; Peshwe, V.B.; Tengali, S.

    . Considerable potential exists for the use of drifting buoys if the cost of data acquisition and processing systems is held at a reasonable level. As yet it is in infancy and further development is required before system reliability and longevity are considered...

  6. Dike Propagation Near Drifts

    Energy Technology Data Exchange (ETDEWEB)

    NA

    2002-03-04

    The purpose of this Analysis and Model Report (AMR) supporting the Site Recommendation/License Application (SR/LA) for the Yucca Mountain Project is the development of elementary analyses of the interactions of a hypothetical dike with a repository drift (i.e., tunnel) and with the drift contents at the potential Yucca Mountain repository. This effort is intended to support the analysis of disruptive events for Total System Performance Assessment (TSPA). This AMR supports the Process Model Report (PMR) on disruptive events (CRWMS M&O 2000a). This purpose is documented in the development plan (DP) ''Coordinate Modeling of Dike Propagation Near Drifts Consequences for TSPA-SR/LA'' (CRWMS M&O 2000b). Evaluation of that Development Plan and the work to be conducted to prepare Interim Change Notice (ICN) 1 of this report, which now includes the design option of ''Open'' drifts, indicated that no revision to that DP was needed. These analyses are intended to provide reasonable bounds for a number of expected effects: (1) Temperature changes to the waste package from exposure to magma; (2) The gas flow available to degrade waste containers during the intrusion; (3) Movement of the waste package as it is displaced by the gas, pyroclasts and magma from the intruding dike (the number of packages damaged); (4) Movement of the backfill (Backfill is treated here as a design option); (5) The nature of the mechanics of the dike/drift interaction. These analyses serve two objectives: to provide preliminary analyses needed to support evaluation of the consequences of an intrusive event and to provide a basis for addressing some of the concerns of the Nuclear Regulatory Commission (NRC) expressed in the Igneous Activity Issue Resolution Status Report.

  7. Correction of diagnostic x-ray spectra measured with CdTe and CdZnTe detectors

    Energy Technology Data Exchange (ETDEWEB)

    Matsumoto, M. [Osaka Univ., Suita (Japan). Medical School; Kanamori, H.; Toragaito, T.; Taniguchi, A.

    1996-07-01

    We modified the formula of stripping procedure presented by E. Di. Castor et al. We added the Compton scattering and separated K{sub {alpha}} radiation of Cd and Te (23 and 27keV, respectively). Using the new stripping procedure diagnostic x-ray spectra (object 4mm-Al) of tube voltage 50kV to 100kV for CdTe and CdZnTe detectors are corrected with comparison of those spectra for the Ge detector. The corrected spectra for CdTe and CdZnTe detectors coincide with those for Ge detector at lower tube voltage than 70kV. But the corrected spectra at higher tube voltage than 70kV do not coincide with those for Ge detector. The reason is incomplete correction for full energy peak efficiencies of real CdTe and CdZnTe detectors. (J.P.N.)

  8. HAND-HELD GAMMA-RAY SPECTROMETER BASED ON HIGH-EFFICIENCY FRISCH-RING CdZnTe DETECTORS.

    Energy Technology Data Exchange (ETDEWEB)

    CUI,Y.

    2007-05-01

    Frisch-ring CdZnTe detectors have demonstrated good energy resolution, el% FWHM at 662 keV, and good efficiency for detecting gamma rays. This technique facilitates the application of CdZnTe materials for high efficiency gamma-ray detection. A hand-held gamma-ray spectrometer based on Frisch-ring detectors is being designed at Brookhaven National Laboratory. It employs an 8x8 CdZnTe detector array to achieve a high volume of 19.2 cm3, so that detection efficiency is significantly improved. By using the front-end ASICs developed at BNL, this spectrometer has a small profile and high energy resolution. The spectrometer includes signal processing circuit, digitization and storage circuit, high-voltage module, and USB interface. In this paper, we introduce the details of the system structure and report our test results with it.

  9. Diamond pixel modules

    CERN Document Server

    Gan, K K; Robichaud, A; Potenza, R; Kuleshov, S; Kagan, H; Kass, R; Wermes, N; Dulinski, W; Eremin, V; Smith, S; Sopko, B; Olivero, P; Gorisek, A; Chren, D; Kramberger, G; Schnetzer, S; Weilhammer, P; Martemyanov, A; Hugging, F; Pernegger, H; Lagomarsino, S; Manfredotti, C; Mishina, M; Trischuk, W; Dobos, D; Cindro, V; Belyaev, V; Duris, J; Claus, G; Wallny, R; Furgeri, A; Tuve, C; Goldstein, J; Sciortino, S; Sutera, C; Asner, D; Mikuz, M; Lo Giudice, A; Velthuis, J; Hits, D; Griesmayer, E; Oakham, G; Frais-Kolbl, H; Bellini, V; D'Alessandro, R; Cristinziani, M; Barbero, M; Schaffner, D; Costa, S; Goffe, M; La Rosa, A; Bruzzi, M; Schreiner, T; de Boer, W; Parrini, G; Roe, S; Randrianarivony, K; Dolenc, I; Moss, J; Brom, J M; Golubev, A; Mathes, M; Eusebi, R; Grigoriev, E; Tsung, J W; Mueller, S; Mandic, I; Stone, R; Menichelli, D

    2011-01-01

    With the commissioning of the LHC in 2010 and upgrades expected in 2015, ATLAS and CMS are planning to upgrade their innermost tracking layers with radiation hard technologies. Chemical Vapor Deposition diamond has been used extensively in beam conditions monitors as the innermost detectors in the highest radiation areas of BaBar, Belle, CDF and all LHC experiments. This material is now being considered as a sensor material for use very close to the interaction region where the most extreme radiation conditions exist Recently the RD42 collaboration constructed, irradiated and tested polycrystalline and single-crystal chemical vapor deposition diamond sensors to the highest fluences expected at the super-LHC. We present beam test results of chemical vapor deposition diamond up to fluences of 1.8 x 10(16) protons/cm(2) illustrating that both polycrystalline and single-crystal chemical vapor deposition diamonds follow a single damage curve. We also present beam test results of irradiated complete diamond pixel m...

  10. Style drift in private equity

    NARCIS (Netherlands)

    D. Cumming; G. Fleming; A. Schwienbacher

    2009-01-01

    We introduce the concept of style drift to private equity investment. We present theory and evidence pertaining to style drifts in terms of a fund manager's stated focus on particular stages of entrepreneurial development. We develop a model that derives conditions under which style drifts are less

  11. Drift-Diffusion Equation

    Directory of Open Access Journals (Sweden)

    K. Banoo

    1998-01-01

    equation in the discrete momentum space. This is shown to be similar to the conventional drift-diffusion equation except that it is a more rigorous solution to the Boltzmann equation because the current and carrier densities are resolved into M×1 vectors, where M is the number of modes in the discrete momentum space. The mobility and diffusion coefficient become M×M matrices which connect the M momentum space modes. This approach is demonstrated by simulating electron transport in bulk silicon.

  12. From Pixels to Planets

    Science.gov (United States)

    Brownston, Lee; Jenkins, Jon M.

    2015-01-01

    The Kepler Mission was launched in 2009 as NASAs first mission capable of finding Earth-size planets in the habitable zone of Sun-like stars. Its telescope consists of a 1.5-m primary mirror and a 0.95-m aperture. The 42 charge-coupled devices in its focal plane are read out every half hour, compressed, and then downlinked monthly. After four years, the second of four reaction wheels failed, ending the original mission. Back on earth, the Science Operations Center developed the Science Pipeline to analyze about 200,000 target stars in Keplers field of view, looking for evidence of periodic dimming suggesting that one or more planets had crossed the face of its host star. The Pipeline comprises several steps, from pixel-level calibration, through noise and artifact removal, to detection of transit-like signals and the construction of a suite of diagnostic tests to guard against false positives. The Kepler Science Pipeline consists of a pipeline infrastructure written in the Java programming language, which marshals data input to and output from MATLAB applications that are executed as external processes. The pipeline modules, which underwent continuous development and refinement even after data started arriving, employ several analytic techniques, many developed for the Kepler Project. Because of the large number of targets, the large amount of data per target and the complexity of the pipeline algorithms, the processing demands are daunting. Some pipeline modules require days to weeks to process all of their targets, even when run on NASA's 128-node Pleiades supercomputer. The software developers are still seeking ways to increase the throughput. To date, the Kepler project has discovered more than 4000 planetary candidates, of which more than 1000 have been independently confirmed or validated to be exoplanets. Funding for this mission is provided by NASAs Science Mission Directorate.

  13. Bump bonding of pixel systems

    Energy Technology Data Exchange (ETDEWEB)

    Lozano, M. E-mail: manuel.lozano@cnm.es; Cabruja, E.; Collado, A.; Santander, J.; Ullan, M

    2001-11-01

    A pixel detector consists of an array of radiation sensing elements which is connected to an electronic read-out unit. Many different ways of making this connection between these two different devices are currently being used or considered to be used in the next future. Bonding techniques such as flip chip technology can present real advantages because they allow very fine pitch and a high number of I/Os. This paper presents a review of the different flip chip technologies available and their suitability for manufacturing pixel detectors. The particular problems concerning testing of pixel detectors and thermal issues related to them are pointed out.

  14. Bump bonding of pixel systems

    CERN Document Server

    Lozano, M; Collado, A; Santander, J; Ullán, M

    2001-01-01

    A pixel detector consists of an array of radiation sensing elements which is connected to an electronic read-out unit. Many different ways of making this connection between these two different devices are currently being used or considered to be used in the next future. Bonding techniques such as flip chip technology can present real advantages because they allow very fine pitch and a high number of I/Os. This paper presents a review of the different flip chip technologies available and their suitability for manufacturing pixel detectors. The particular problems concerning testing of pixel detectors and thermal issues related to them are pointed out.

  15. CMS Barrel Pixel Detector Overview

    CERN Document Server

    Kästli, H C; Erdmann, W; Gabathuler, K; Hörmann, C; Horisberger, Roland Paul; König, S; Kotlinski, D; Meier, B; Robmann, P; Rohe, T; Streuli, S

    2007-01-01

    The pixel detector is the innermost tracking device of the CMS experiment at the LHC. It is built from two independent sub devices, the pixel barrel and the end disks. The barrel consists of three concentric layers around the beam pipe with mean radii of 4.4, 7.3 and 10.2 cm. There are two end disks on each side of the interaction point at 34.5 cm and 46.5 cm. This article gives an overview of the pixel barrel detector, its mechanical support structure, electronics components, services and its expected performance.

  16. Novel electrode geometry to improve performance of CdZnTe detectors

    DEFF Research Database (Denmark)

    van Pamelen, M.A.J.; Budtz-Jørgensen, Carl

    1998-01-01

    unipolar sensing. The effectiveness of the geometry was demonstrated with a CdZnTe crystal. Above X-ray energies of 40 keV, large improvements were achieved ill the spectral sensitivity, and the spectral resolution could be increased further by applying a correction for charge trapping. The peak of Cs-137......A novel electrode geometry to improve the sensitivity to single-polarity charge carriers in ionization detectors is presented. The electrode geometry is based on the same principle as Frisch grids in gas detectors. It reduces the sensitivity to one type of charge carrier, making the detector almost...

  17. Zinc segregation in CdZnTe grown under Cd/Zn partial pressure control

    Science.gov (United States)

    Azoulay, M.; Rotter, S.; Gafni, G.; Tenne, R.; Roth, M.

    1992-02-01

    CdZnTe crystals have been grown by the modified vertical gradient freeze (VGF) method. Growth atmosphere control has been introduced to compensate for the Zn depletion in the melt during solidification. The axial Zn concentration in the grown crystals is found to be uniform within ±3%, as evaluated by X-ray diffraction and electron microprobe analysis. The radial segregation of Zn is minimal and does not exceed the experimental error due to the nearly planar interface achieved. Zinc microsegregation has been studied as well and is discussed in terms of the temporal variations of the solute concentration at the growth interface.

  18. Infrared LED Enhanced Spectroscopic CdZnTe Detector Working under High Fluxes of X-rays

    Directory of Open Access Journals (Sweden)

    Jakub Pekárek

    2016-09-01

    Full Text Available This paper describes an application of infrared light-induced de-polarization applied on a polarized CdZnTe detector working under high radiation fluxes. We newly demonstrate the influence of a high flux of X-rays and simultaneous 1200-nm LED illumination on the spectroscopic properties of a CdZnTe detector. CdZnTe detectors operating under high radiation fluxes usually suffer from the polarization effect, which occurs due to a screening of the internal electric field by a positive space charge caused by photogenerated holes trapped at a deep level. Polarization results in the degradation of detector charge collection efficiency. We studied the spectroscopic behavior of CdZnTe under various X-ray fluxes ranging between 5 × 10 5 and 8 × 10 6 photons per mm 2 per second. It was observed that polarization occurs at an X-ray flux higher than 3 × 10 6 mm − 2 ·s − 1 . Using simultaneous illumination of the detector by a de-polarizing LED at 1200 nm, it was possible to recover X-ray spectra originally deformed by the polarization effect.

  19. Infrared LED Enhanced Spectroscopic CdZnTe Detector Working under High Fluxes of X-rays.

    Science.gov (United States)

    Pekárek, Jakub; Dědič, Václav; Franc, Jan; Belas, Eduard; Rejhon, Martin; Moravec, Pavel; Touš, Jan; Voltr, Josef

    2016-09-27

    This paper describes an application of infrared light-induced de-polarization applied on a polarized CdZnTe detector working under high radiation fluxes. We newly demonstrate the influence of a high flux of X-rays and simultaneous 1200-nm LED illumination on the spectroscopic properties of a CdZnTe detector. CdZnTe detectors operating under high radiation fluxes usually suffer from the polarization effect, which occurs due to a screening of the internal electric field by a positive space charge caused by photogenerated holes trapped at a deep level. Polarization results in the degradation of detector charge collection efficiency. We studied the spectroscopic behavior of CdZnTe under various X-ray fluxes ranging between 5 × 10 5 and 8 × 10 6 photons per mm 2 per second. It was observed that polarization occurs at an X-ray flux higher than 3 × 10 6 mm - 2 ·s - 1 . Using simultaneous illumination of the detector by a de-polarizing LED at 1200 nm, it was possible to recover X-ray spectra originally deformed by the polarization effect.

  20. Progress in the Development of CdZnTe Unipolar Detectors for Different Anode Geometries and Data Corrections

    Directory of Open Access Journals (Sweden)

    Qiushi Ren

    2013-02-01

    Full Text Available CdZnTe detectors have been under development for the past two decades, providing good stopping power for gamma rays, lightweight camera heads and improved energy resolution. However, the performance of this type of detector is limited primarily by incomplete charge collection problems resulting from charge carriers trapping. This paper is a review of the progress in the development of CdZnTe unipolar detectors with some data correction techniques for improving performance of the detectors. We will first briefly review the relevant theories. Thereafter, two aspects of the techniques for overcoming the hole trapping issue are summarized, including irradiation direction configuration and pulse shape correction methods. CdZnTe detectors of different geometries are discussed in detail, covering the principal of the electrode geometry design, the design and performance characteristics, some detector prototypes development and special correction techniques to improve the energy resolution. Finally, the state of art development of 3-D position sensing and Compton imaging technique are also discussed. Spectroscopic performance of CdZnTe semiconductor detector will be greatly improved even to approach the statistical limit on energy resolution with the combination of some of these techniques.

  1. Angular response of a W-collimated room-temperature-operated CdZnTe Frisch collar spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Kargar, Alireza [S.M.A.R.T. Laboratory, Department of Mechanical and Nuclear Engineering, Kansas State University, Manhattan, KS 66506 (United States); Jones, Andrew M. [S.M.A.R.T. Laboratory, Department of Mechanical and Nuclear Engineering, Kansas State University, Manhattan, KS 66506 (United States); McNeil, Walter J. [S.M.A.R.T. Laboratory, Department of Mechanical and Nuclear Engineering, Kansas State University, Manhattan, KS 66506 (United States); Harrison, Mark J. [S.M.A.R.T. Laboratory, Department of Mechanical and Nuclear Engineering, Kansas State University, Manhattan, KS 66506 (United States); McGregor, Douglas S. [S.M.A.R.T. Laboratory, Department of Mechanical and Nuclear Engineering, Kansas State University, Manhattan, KS 66506 (United States)]. E-mail: mcgregor@ksu.edu

    2006-06-15

    The spatial resolution of a collimated CdZnTe Frisch collar detector was experimentally investigated for two different tungsten collimator designs using a {sup 198}Au gamma-ray source at 412 keV. A two-dimensional model for the detector-collimator-source geometry was developed and applied with some simplifying assumptions. The CdZnTe detector was fabricated from a single crystal using a copper shim as the Frisch collar. The detector fabrication process is briefly described. Pulse height spectra were collected from {sup 241}Am, {sup 198}Au and {sup 137}Cs using a 3.4x3.4x5.8 mm{sup 3} CdZnTe detector utilizing an insulated Frisch collar mounted inside a tungsten collimator. The resulting energy spectra are presented. Room-temperature energy resolution of 1.72% full-width at half-maximum (FWHM) was obtained for {sup 137}Cs at 662 keV without electronic correction. The two-dimensional model reasonably predicts the angular response of the CdZnTe detectors when inserted into two different collimators.

  2. Characterization of CdZnTe after argon ion beam bombardment

    Energy Technology Data Exchange (ETDEWEB)

    Bensalah, H., E-mail: hakima.bensalah@uam.es [Departamento de Fisica de Materiales, Laboratorio de Crecimiento de Cristales, Facultad de Ciencias, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Hortelano, V. [GdS-Optronlab Group, Departamento Fisica Materia Condensada, Universidad de Valladolid, Edificio I-D, Paseo de Belen 1, 47011 Valladolid (Spain); Plaza, J.L. [Departamento de Fisica de Materiales, Laboratorio de Crecimiento de Cristales, Facultad de Ciencias, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Martinez, O. [GdS-Optronlab Group, Departamento Fisica Materia Condensada, Universidad de Valladolid, Edificio I-D, Paseo de Belen 1, 47011 Valladolid (Spain); Crocco, J.; Zheng, Q.; Carcelen, V.; Dieguez, E. [Departamento de Fisica de Materiales, Laboratorio de Crecimiento de Cristales, Facultad de Ciencias, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain)

    2012-12-05

    Highlights: Black-Right-Pointing-Pointer After argon irradiation using low fluence, the defects on surface were removed. Black-Right-Pointing-Pointer The PL intensity increases after irradiation. This increase should be related to the improved quality of the CdZnTe surfaces. Black-Right-Pointing-Pointer Irradiation process lead to an elimination of Te precipitates from the surfaces of the CdZnTe samples. - Abstract: The objective of this work is to analyze the effects of argon ion irradiation process on the structure and distribution of Te inclusions in Cd{sub 1-x}Zn{sub x}Te crystals. The samples were treated with different ion fluences ranging from 2 to 8 Multiplication-Sign 10{sup 17} cm{sup -2}. The state of the samples before and after irradiation were studied by Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Cathodoluminescence, Photoluminescence, and micro-Raman spectroscopy. The effect of the irradiation on the surface of the samples was clearly observed by SEM or AFM. Even for small fluences a removal of polishing scratches on the sample surfaces was observed. Likely correlated to this effect, an important enhancement in the luminescence intensity of the irradiated samples was observed. An aggregation effect of the Te inclusions seems to occur due to the Ar bombardment, which are also eliminated from the surfaces for the highest ion fluences used.

  3. Low noise CMOS readout for CdZnTe detector arrays

    CERN Document Server

    Jakobson, C G; Lev, S B; Nemirovsky, Y

    1999-01-01

    A low noise CMOS readout for CdTe and CdZnTe X- and gamma-ray detector arrays has been designed and implemented in the CMOS 2 mu m low noise analog process provided by the multi-chip program of Metal Oxide Semiconductor Implementation Service. The readout includes CMOS low noise charge sensitive preamplifier and a multiplexed semi-Gaussian pulse shaper. Thus, each detector has a dedicated charge sensitive preamplifier that integrates its signal, while a single shaping amplifier shapes the pulses after the multiplexer. Low noise and low-power operation are achieved by optimizing the input transistor of the charge sensitive preamplifier. Two optimization criteria are used to reduce noise. The first criterion is based on capacitance matching between the input transistor and the detector. The second criterion is based on bandwidth optimization, which is obtained by tailoring the shaper parameters to the particular noise mechanisms of the MOS transistor and the CdZnTe detector. Furthermore, the multiplexing functi...

  4. CdZnTe Frisch collar detectors for {gamma}-ray spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kargar, Alireza [S.M.A.R.T. Laboratory, Department of Mechanical and Nuclear Engineering, Kansas State University, Manhattan, KS 66506 (United States); Jones, Andrew M. [S.M.A.R.T. Laboratory, Department of Mechanical and Nuclear Engineering, Kansas State University, Manhattan, KS 66506 (United States); McNeil, Walter J. [S.M.A.R.T. Laboratory, Department of Mechanical and Nuclear Engineering, Kansas State University, Manhattan, KS 66506 (United States); Harrison, Mark J. [S.M.A.R.T. Laboratory, Department of Mechanical and Nuclear Engineering, Kansas State University, Manhattan, KS 66506 (United States); McGregor, Douglas S. [S.M.A.R.T. Laboratory, Department of Mechanical and Nuclear Engineering, Kansas State University, Manhattan, KS 66506 (United States)]. E-mail: mcgregor@ksu.edu

    2006-03-15

    Low-energy {gamma}-ray spectra were collected from {sup 241}Am, {sup 57}Co, {sup 133}Ba, {sup 198}Au, {sup 137}Cs and {sup 235}U using a 3.4x3.4x5.7 mm{sup 3} CdZnTe detector utilizing an insulated Frisch ring. The CdZnTe detector was fabricated from a single crystal and a copper shim was used as the Frisch collar. Room-temperature energy resolution of 1.45% full-width half-maximum (FWHM) was obtained for {sup 137}Cs at 661.7 keV without electronic correction. The detector fabrication process is described and the resulting energy spectra are discussed. The detector fabrication process is described and the resulting energy spectra are discussed. The detector full-energy-peak intrinsic efficiency is reported for different {gamma}-ray energies, specifically from {sup 241}Am, {sup 57}Co, {sup 133}Ba and {sup 137}Cs.

  5. Characterisation of vapour grown CdZnTe crystals using synchrotron X-ray topography

    Science.gov (United States)

    Egan, Christopher K.; Choubey, Ashutosh; Moore, Moreton; Cernik, Robert J.

    2012-03-01

    Synchrotron white beam X-ray topography has been used to characterise bulk crystal defects of thick vapour grown CdZnTe crystals. Whole 50 mm diameter wafers with thicknesses in the range of 2-3 mm were sliced from boules grown by the multi-tube physical vapour transport method and analysed by diffraction topography in a transmission geometry. A variety of defects were observed including cracks, voids and grain boundaries. The largest quantity of defects observed were sub-grains appearing as localised increased intensity in the topographs. The periphery of the wafers showed the highest number of defects, whereas central regions where largely defect-free. We failed to observe any inclusions or precipitates within these crystals. Surface damage from wire-saw cutting was also observed on poorly processed wafers; these defects were otherwise invisible to standard characterisation methods. X-ray topography has proven to be a useful tool for non-destructively investigating bulk extended defects in CdZnTe crystals for radiation detector applications.

  6. Analysis of trapping and de-trapping in CdZnTe detectors by Pockels effect

    Science.gov (United States)

    Rejhon, M.; Franc, J.; Dědič, V.; Kunc, J.; Grill, R.

    2016-09-01

    In this contribution we introduce a method of deep level spectroscopy in semi-insulating semiconductors demonstrated on detector-grade bulk CdZnTe. The method is based on the measurements of temporal and temperature evolution of the electric field profile in studied samples, which is very sensitive to a change of occupancy of deep levels. The measurement of the electric field is based on the linear electro-optic (Pockels) effect using the InGaAs avalanche photodiode with fast response. The internal electric field profile in studied samples significantly changes under various external conditions represented by the application of the bias and pulsed illumination with below-bandgap light. From the knowledge of the electric field behavior and using a standard analysis based on thermally induced transitions of electrons and holes from the deep levels to the conduction and valence bands, respectively, it is possible to get activation energies of the energy levels, their types (donor or acceptor) and corresponding capture cross-sections. By this method we have found deep levels responsible for the polarization of CdZnTe detector under high photon-fluxes. Identified deep levels {{E}\\text{v}}+0.41 eV, {{E}\\text{v}}+0.77 eV and {{E}\\text{v}}+0.94 eV can capture the photo-generated holes and thus form a positive space charge, which is responsible for polarization of the detector.

  7. Low noise CMOS readout for CdZnTe detector arrays

    Energy Technology Data Exchange (ETDEWEB)

    Jakobson, C.G.; Asa, G.; Lev, S. Bar; Nemirovsky, Y. E-mail: nemirov@ee.technion.ac.il

    1999-06-01

    A low noise CMOS readout for CdTe and CdZnTe X- and gamma-ray detector arrays has been designed and implemented in the CMOS 2 {mu}m low noise analog process provided by the multi-chip program of Metal Oxide Semiconductor Implementation Service. The readout includes CMOS low noise charge sensitive preamplifier and a multiplexed semi-Gaussian pulse shaper. Thus, each detector has a dedicated charge sensitive preamplifier that integrates its signal, while a single shaping amplifier shapes the pulses after the multiplexer. Low noise and low-power operation are achieved by optimizing the input transistor of the charge sensitive preamplifier. Two optimization criteria are used to reduce noise. The first criterion is based on capacitance matching between the input transistor and the detector. The second criterion is based on bandwidth optimization, which is obtained by tailoring the shaper parameters to the particular noise mechanisms of the MOS transistor and the CdZnTe detector. Furthermore, the multiplexing function incorporated in the shaper provides low power and reduces chip area. The system is partitioned into a chip containing the charge amplifiers and a chip containing the semi-Gaussian pulse shaper and multiplexer. This architecture minimizes coupling from multiplexer switches as well as shaper output to the input of the charge sensitive preamplifiers.

  8. Fingermark ridge drift.

    Science.gov (United States)

    De Alcaraz-Fossoul, Josep; Roberts, Katherine A; Feixat, Carme Barrot; Hogrebe, Gregory G; Badia, Manel Gené

    2016-01-01

    Distortions of the fingermark topography are usually considered when comparing latent and exemplar fingerprints. These alterations are characterized as caused by an extrinsic action, which affects entire areas of the deposition and alters the overall flow of a series of contiguous ridges. Here we introduce a novel visual phenomenon that does not follow these principles, named fingermark ridge drift. An experiment was designed that included variables such as type of secretion (eccrine and sebaceous), substrate (glass and polystyrene), and degrees of exposure to natural light (darkness, shade, and direct light) indoors. Fingermarks were sequentially visualized with titanium dioxide powder, photographed and analyzed. The comparison between fresh and aged depositions revealed that under certain environmental conditions an individual ridge could randomly change its original position regardless of its unaltered adjacent ridges. The causes of the drift phenomenon are not well understood. We believe it is exclusively associated with intrinsic natural aging processes of latent fingermarks. This discovery will help explain the detection of certain dissimilarities at the minutiae/ridge level; determine more accurate "hits"; identify potentially erroneous corresponding points; and rethink identification protocols, especially the criteria of "no single minutiae discrepancy" for a positive identification.

  9. The CLEO III drift chamber

    CERN Document Server

    Peterson, D; Briere, R A; Chen, G; Cronin-Hennessy, D; Csorna, S; Dickson, M; Dombrowski, S V; Ecklund, K M; Lyon, A; Marka, S; Meyer, T O; Patterson, J R; Sadoff, A; Thies, P; Thorndike, E H; Urner, D

    2002-01-01

    The CLEO group at the Cornell Electron Storage Ring has constructed and commissioned a new central drift chamber. With 9796 cells arranged in 47 layers ranging in radius from 13.2 to 79 cm, the new drift chamber has a smaller outer radius and fewer wires than the drift chamber it replaces, but allows the CLEO tracking system to have improved momentum resolution. Reduced scattering material in the chamber gas and in the inner skin separating the drift chamber from the silicon vertex detector provides a reduction of the multiple scattering component of the momentum resolution and an extension of the usable measurement length into the silicon. Momentum resolution is further improved through quality control in wire positioning and symmetry of the electric fields in the drift cells which have provided a reduction in the spatial resolution to 88 mu m (averaged over the full drift range).

  10. The DRIFT Dark Matter Experiments

    CERN Document Server

    Daw, E; Fox, J R; Gauvreau, J -L; Ghag, C; Harmon, L J; Harton, J L; Gold, M; Lee, E R; Loomba, D; Miller, E H; Murphy, A St J; Paling, S M; Landers, J M; Phan, N; Pipe, M; Pushkin, K; Robinson, M; Sadler, S W; Snowden-Ifft, D P; Spooner, N J C; Walker, D; Warner, D

    2011-01-01

    The current status of the DRIFT (Directional Recoil Identification From Tracks) experiment at Boulby Mine is presented, including the latest limits on the WIMP spin-dependent cross-section from 1.5 kg days of running with a mixture of CS2 and CF4. Planned upgrades to DRIFT IId are detailed, along with ongoing work towards DRIFT III, which aims to be the world's first 10 m3-scale directional Dark Matter detector.

  11. Study of the Tracking Method and Expected Performance of the Silicon Pixel Inner Tracker Applied in BESIII

    CERN Document Server

    Xiu, Qinglei; Li, Weidong; Liu, Huaimin; Ma, Qiumei; Ouyang, Qun; Qin, Zhonghua; Wang, Liangliang; Wu, Linghui; Yuan, Ye; Zhang, Yao

    2015-01-01

    The inner drift chamber of the BESIII is encountering serious aging problem after five year's running. For the first layer, the decrease in gas gain is about 26% from 2009 to 2013. The upgrade of the inner tracking detector has become an urgent problem for the BESIII experiment. An inner tracker using CMOS pixel sensors is an important candidate because of its great advantages on spatial resolution and radiation hardness. In order to carry out a Monte Carlo study on the expected performance, a Geant4-based full simulation for the silicon pixel detector has been implemented. The tracking method combining the silicon pixel inner tracker and outer drift chamber has been studied and a preliminary reconstruction software was developed. The Monte Carlo study shows that the performances including momentum resolution, vertex resolution and the tracking efficiency are significantly improved due to the good spatial resolution and moderate material budget of the silicon pixel detector.

  12. Evaluation of ZnO:Al as a contact material to CdZnTe for radiation detector applications (Conference Presentation)

    Science.gov (United States)

    Roy, Utpal N.; Camarda, Giuseppe S.; Cui, Yonggang; Gul, Rubi; Hossain, Anwar; Yang, Ge; James, Ralph B.; Pradhan, Aswini K.; Mundle, Rajeh

    2016-09-01

    Aluminum (Al) doped ZnO with very high Al concentration acts as metal regarding its electrical conductivity. ZnO offers many advantages over the commonly-known metals being used today as electrode materials for nuclear detector fabrication. Often, the common metals show poor adhesion to CdZnTe or CdTe surfaces and have a tendency to peel off. In addition, there is a large mismatch of the coefficients of thermal expansion (CTE) between the metals and underlying CdZnTe, which is one of the reasons for mechanical degradation of the contact. In contrast ZnO has a close match of the CTE with CdZnTe and possesses 8-20 times higher hardness than the commonly-used metals. In this presentation, we will explore and discuss the properties of CdZnTe detectors with ZnO:Al contacts.

  13. The KLOE drift chamber

    Energy Technology Data Exchange (ETDEWEB)

    Adinolfi, M.; Aloisio, A.; Ambrosino, F.; Andryakov, A.; Antonelli, A.; Antonelli, M.; Anulli, F.; Bacci, C.; Bankamp, A.; Barbiellini, G.; Bellini, F.; Bencivenni, G.; Bertolucci, S.; Bini, C.; Bloise, C.; Bocci, V.; Bossi, F.; Branchini, P.; Bulychjov, S.A.; Cabibbo, G.; Calcaterra, A.; Caloi, R.; Campana, P.; Capon, G.; Carboni, G.; Cardini, A.; Casarsa, M.; Cataldi, G.; Ceradini, F.; Cervelli, F.; Cevenini, F.; Chiefari, G.; Ciambrone, P.; Conetti, S.; Conticelli, S.; Lucia, E. De; Robertis, G. De; Sangro, R. De; Simone, P. De; Zorzi, G. De; Dell' Agnello, S.; Denig, A.; Domenico, A. Di; Donato, C. Di; Falco, S. Di; Doria, A.; Drago, E.; Elia, V.; Erriquez, O.; Farilla, A.; Felici, G.; Ferrari, A.; Ferrer, M.L.; Finocchiaro, G.; Forti, C.; Franceschi, A.; Franzini, P.; Gao, M.L.; Gatti, C.; Gauzzi, P.; Giovannella, S.; Golovatyuk, V.; Gorini, E.; Grancagnolo, F.; Grandegger, W.; Graziani, E.; Guarnaccia, P.; Hagel, U.V.; Han, H.G.; Han, S.W.; Huang, X.; Incagli, M.; Ingrosso, L.; Jang, Y.Y.; Kim, W.; Kluge, W.; Kulikov, V.; Lacava, F.; Lanfranchi, G.; Lee-Franzini, J.; Lomtadze, F.; Luisi, C.; Mao, C.S.; Martemianov, M.; Matsyuk, M.; Mei, W.; Merola, L.; Messi, R.; Miscetti, S.; Moalem, A.; Moccia, S.; Moulson, M.; Mueller, S.; Murtas, F.; Napolitano, M.; Nedosekin, A.; Panareo, M.; Pacciani, L.; Pages, P.; Palutan, M.; Paoluzi, L.; Pasqualucci, E.; Passalacqua, L.; Passaseo, M.; Passeri, A.; Patera, V.; Petrolo, E.; Petrucci, G.; Picca, D.; Pirozzi, G.; Pistillo, C.; Pollack, M.; Pontecorvo, L.; Primavera, M.; Ruggieri, F.; Santangelo, P.; Santovetti, E.; Saracino, G.; Schamberger, R.D.; Schwick, C.; Sciascia, B.; Sciubba, A.; Scuri, F.; Sfiligoi, I.; Shan, J.; Silano, P.; Spadaro, T.; Spagnolo, S.; Spiriti, E.; Stanescu, C.; Tong, G.L.; Tortora, L.; Valente, E.; Valente, P. E-mail: paolo.valente@lnf.infn.it; Valeriani, B.; Venanzoni, G.; Veneziano, S.; Wu, Y.; Xie, Y.G.; Zhao, P.P.; Zhou, Y

    2001-04-01

    The tracking detector of the KLOE experiment is 4 m diameter, 3.3 m length drift chamber, designed to contain a large fraction of the decays of low-energy K{sub L} produced at the Frascati DAPHINE phi-factory. The chamber is made by a thin carbon fiber structure and operated with a helium-based gas mixture in order to minimise conversion of low-energy photons and multiple scattering inside the sensitive volume. The tracking information is provided by 58 layers of stereo wires defing 12,582 cells, 2x2 cm{sup 2} in size in the 12 innermost layers and 3x3 cm{sup 2} in the outer ones. Details of the chamber design, calibration procedure and tracking performances are presented.

  14. High rate drift chambers

    Energy Technology Data Exchange (ETDEWEB)

    Christian, D.C. (Fermilab, Batavia, IL 60510 (United States)); Berisso, M.C. (Fermilab, Batavia, IL 60510 (United States)); Gutierrez, G. (Fermilab, Batavia, IL 60510 (United States)); Holmes, S.D. (Fermilab, Batavia, IL 60510 (United States)); Wehmann, A. (Fermilab, Batavia, IL 60510 (United States)); Avilez, C. (Instituto de Fisica, Universidad de Guanajuato, Leon, Guanajuato (Mexico)); Felix, J. (Instituto de Fisica, Universidad de Guanajuato, Leon, Guanajuato (Mexico)); Moreno, G. (Instituto de Fisica, Universidad de Guanajuato, Leon, Guanajuato (Mexico)); Romero, M. (Instituto de Fisica, Universidad de Guanajuato, Leon, Guanajuato (Mexico)); Sosa, M. (Instituto de Fisica, Universidad de Guanajuato, Leon, Guanajuato (Mexico)); Forbush, M. (Department of Physics, Texas A and M University, College Station, TX 77843 (United States)); Huson, F.R. (Department of Physics, Texas A and M University, College Station, TX 77843 (United States)); Wightman, J.A. (Department of Physi

    1994-06-01

    Fermilab experiment 690, a study of target dissociation reactions pp[yields]pX using an 800 GeV/c proton beam and a liquid hydrogen target, collected data in late 1991. The incident beam and 600-800 GeV/c scattered protons were measured using a system of six 6 in.x4 in. and two 15 in.x8 in. pressurized drift chambers spaced over 260 m. These chambers provided precise measurements at rates above 10 MHz (2 MHz per cm of sense wire). The measurement resolution of the smaller chambers was 90 [mu]m, and the resolution of the larger chambers was 125 [mu]m. Construction details and performance results, including radiation damage, are presented. ((orig.))

  15. The KLOE drift chamber

    CERN Document Server

    Adinolfi, M; Ambrosino, F; Andryakov, A; Antonelli, A; Antonelli, M; Anulli, F; Bacci, C; Bankamp, A; Barbiellini, G; Bellini, F; Bencivenni, G; Bertolucci, Sergio; Bini, C; Bloise, C; Bocci, V; Bossi, F; Branchini, P; Bulychjov, S A; Cabibbo, G; Calcaterra, A; Caloi, R; Campana, P; Capon, G; Carboni, G; Cardini, A; Casarsa, M; Cataldi, G; Ceradini, F; Cervelli, F; Cevenini, F; Chiefari, G; Ciambrone, P; Conetti, S; Conticelli, S; Lucia, E D; Robertis, G D; Sangro, R D; Simone, P D; Zorzi, G D; Dell'Agnello, S; Denig, A; Domenico, A D; Donato, C D; Falco, S D; Doria, A; Drago, E; Elia, V; Erriquez, O; Farilla, A; Felici, G; Ferrari, A; Ferrer, M L; Finocchiaro, G; Forti, C; Franceschi, A; Franzini, P; Gao, M L; Gatti, C; Gauzzi, P; Giovannella, S; Golovatyuk, V; Gorini, E; Grancagnolo, F; Grandegger, W; Graziani, E; Guarnaccia, P; Von Hagel, U; Han, H G; Han, S W; Huang, X; Incagli, M; Ingrosso, L; Jang, Y Y; Kim, W; Kluge, W; Kulikov, V; Lacava, F; Lanfranchi, G; Lee-Franzini, J; Lomtadze, F; Luisi, C; Mao Chen Sheng; Martemyanov, M; Matsyuk, M; Mei, W; Merola, L; Messi, R; Miscetti, S; Moalem, A; Moccia, S; Moulson, M; Müller, S; Murtas, F; Napolitano, M; Nedosekin, A; Panareo, M; Pacciani, L; Pagès, P; Palutan, M; Paoluzi, L; Pasqualucci, E; Passalacqua, L; Passaseo, M; Passeri, A; Patera, V; Petrolo, E; Petrucci, Guido; Picca, D; Pirozzi, G; Pistillo, C; Pollack, M; Pontecorvo, L; Primavera, M; Ruggieri, F; Santangelo, P; Santovetti, E; Saracino, G; Schamberger, R D; Schwick, C; Sciascia, B; Sciubba, A; Scuri, F; Sfiligoi, I; Shan, J; Silano, P; Spadaro, T; Spagnolo, S; Spiriti, E; Stanescu, C; Tong, G L; Tortora, L; Valente, E; Valente, P; Valeriani, B; Venanzoni, G; Veneziano, Stefano; Wu, Y; Xie, Y G; Zhao, P P; Zhou, Y

    2001-01-01

    The tracking detector of the KLOE experiment is 4 m diameter, 3.3 m length drift chamber, designed to contain a large fraction of the decays of low-energy K sub L produced at the Frascati DAPHINE phi-factory. The chamber is made by a thin carbon fiber structure and operated with a helium-based gas mixture in order to minimise conversion of low-energy photons and multiple scattering inside the sensitive volume. The tracking information is provided by 58 layers of stereo wires defing 12,582 cells, 2x2 cm sup 2 in size in the 12 innermost layers and 3x3 cm sup 2 in the outer ones. Details of the chamber design, calibration procedure and tracking performances are presented.

  16. DRIFT EFFECTS IN HGCDTE DETECTORS

    Directory of Open Access Journals (Sweden)

    B. PAVAN KUMAR

    2013-08-01

    Full Text Available The characteristics of temporal drift in spectral responsivity of HgCdTe photodetectors is investigated and found to have an origin different from what has been reported in literature. Traditionally, the literature attributes the cause of drift due to the deposition of thin film of ice water on the active area of the cold detector. The source of drift as proposed in this paper is more critical owing to the difficulties in acquisition of infrared temperature measurements. A model explaining the drift phenomenon in HgCdTe detectors is described by considering the deep trapping of charge carriers and generation of radiation induced deep trap centers which are meta-stable in nature. A theoretical model is fitted to the experimental data. A comparison of the model with the experimental data shows that the radiation induced deep trap centers and charge trapping effects are mainly responsible for the drift phenomenon observed in HgCdTe detectors.

  17. Bouchaud walks with variable drift

    CERN Document Server

    Parra, Manuel Cabezas

    2010-01-01

    In this paper we study a sequence of Bouchaud trap models on $\\mathbb{Z}$ with drift. We analyze the possible scaling limits for a sequence of walks, where we make the drift decay to 0 as we rescale the walks. Depending on the speed of the decay of the drift we obtain three different scaling limits. If the drift decays slowly as we rescale the walks we obtain the inverse of an \\alpha$-stable subordinator as scaling limit. If the drift decays quickly as we rescale the walks, we obtain the F.I.N. diffusion as scaling limit. There is a critical speed of decay separating these two main regimes, where a new process appears as scaling limit. This critical speed is related to the index $\\alpha$ of the inhomogeneity of the environment.

  18. CTF Void Drift Validation Study

    Energy Technology Data Exchange (ETDEWEB)

    Salko, Robert K. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Gosdin, Chris [Pennsylvania State Univ., University Park, PA (United States); Avramova, Maria N. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Gergar, Marcus [Pennsylvania State Univ., University Park, PA (United States)

    2015-10-26

    This milestone report is a summary of work performed in support of expansion of the validation and verification (V&V) matrix for the thermal-hydraulic subchannel code, CTF. The focus of this study is on validating the void drift modeling capabilities of CTF and verifying the supporting models that impact the void drift phenomenon. CTF uses a simple turbulent-diffusion approximation to model lateral cross-flow due to turbulent mixing and void drift. The void drift component of the model is based on the Lahey and Moody model. The models are a function of two-phase mass, momentum, and energy distribution in the system; therefore, it is necessary to correctly model the ow distribution in rod bundle geometry as a first step to correctly calculating the void distribution due to void drift.

  19. WFC3 Pixel Area Maps

    Science.gov (United States)

    Kalirai, J. S.; Cox, C.; Dressel, L.; Fruchter, A.; Hack, W.; Kozhurina-Platais, V.; Mack, J.

    2010-04-01

    We present the pixel area maps (PAMs) for the WFC3/UVIS and WFC3/IR detectors, and discuss the normalization of these images. HST processed flt images suffer from geometric distortion and therefore have pixel areas that vary on the sky. The counts (electrons) measured for a source on these images depends on the position of the source on the detector, an effect that is implicitly corrected when these images are multidrizzled into drz files. The flt images can be multiplied by the PAMs to yield correct and uniform counts for a given source irrespective of its location on the image. To ensure consistency between the count rate measured for sources in drz images and near the center of flt images, we set the normalization of the PAMs to unity at a reference pixel near the center of the UVIS mosaic and IR detector, and set the SCALE in the IDCTAB equal to the square root of the area of this reference pixel. The implications of this choice for photometric measurements are discussed.

  20. VNR CMS Pixel detector replacement

    CERN Document Server

    2017-01-01

    Joel Butler, spokesperson of the CMS collaboration explains how a team from many different partner institutes installed a new detector in CMS. This detector is the silicon pixel detector and they’ve been working on it for about five years, to replace one of our existing detectors. This detectors measures particles closer to the beam than any of the other components of this huge detector behind me. It gives us the most precise picture of tracks as they come out of the collisions and expand and travel through the detector. This particular device has twice as many pixels, 120 million, as opposed to about 68 million in the old detector and it can take data faster and pump it out to the analysis more quickly. 00’53’’ Images of the descent, insertion and installation of first piece of the Pixel detector on Tue Feb 28. Images of the descent, insertion and installation of second piece of the Pixel and the two cylinders being joined.

  1. Simulation of the anode structure for capacitive Frisch grid CdZnTe detectors

    Institute of Scientific and Technical Information of China (English)

    MIN Jiahua; SHI Zhubin; QIAN Yongbiao; SANG Wenbin; ZHAO Hengyu; TENG Jianyong; LIU Jishan

    2009-01-01

    CdZnTe (CZT) capacitive Frisch grid detectors can achieve a higher detecting resolution.The anode structure might have an important role in improving the weighting potential distribution of the detectors.In this paper,four anode structures of capacitive Frisch grid structures have been analyzed with FE simulation,based on a 3-dimensional weighting potential analysis.The weighting potential distributions in modified anode devices (Model B,C and D) are optimized compared with a square device (Model A).In model C and D,the abrupt weighting potential can be well modified.However,with increased radius of the circular electrode in Model C the weighting potential platform away from the anode becomes higher and higher and in Model D,the weighting potential does not vary too much.

  2. Analysis of Surface Chemistry and Detector Performance of Chemically Process CdZnTe crystals

    Energy Technology Data Exchange (ETDEWEB)

    HOSSAIN, A.; Yang, G.; Sutton, J.; Zergaw, T.; Babalola, O. S.; Bolotnikov, A. E.; Camarda. ZG. S.; Gul, R.; Roy, U. N., and James, R. B.

    2015-10-05

    The goal is to produce non-conductive smooth surfaces for fabricating low-noise and high-efficiency CdZnTe devices for gamma spectroscopy. Sample preparation and results are discussed. The researachers demonstrated various bulk defects (e.g., dislocations and sub-grain boundaries) and surface defects, and examined their effects on the performance of detectors. A comparison study was made between two chemical etchants to produce non-conductive smooth surfaces. A mixture of bromine and hydrogen peroxide proved more effective than conventional bromine etchant. Both energy resolution and detection efficiency of CZT planar detectors were noticeably increased after processing the detector crystals using improved chemical etchant and processing methods.

  3. CdTe and CdZnTe crystals for room temperature gamma-ray detectors

    CERN Document Server

    Franc, J; Belas, E; Grill, R; Hlidek, P; Moravec, P; Bok, J B

    1999-01-01

    CdTe(Cl) detectors from CdTe single crystals, grown by the Bridgman method from Te-rich melt, were fabricated. The quality of the detectors was tested with sup 5 sup 7 Co and sup 2 sup 4 sup 1 Am sources. In the sup 5 sup 7 Co spectrum low noise is demonstrated by the presence of a 14 keV peak and good resolution approx 7 keV (FWHM) evident from the separation of 122 and 136 keV peaks. A review is given of the state-of-the-art properties of (CdZn)Te single crystals prepared for substrates in the Institute of Physics of Charles University. The quality of samples is tested by measurements of the diffusion length of minority carriers, from which the mobility-lifetime product is evaluated. (author)

  4. XA readout chip characteristics and CdZnTe spectral measurements

    Energy Technology Data Exchange (ETDEWEB)

    Barbier, L.M.; Birsa, F.; Odom, J. [NASA/Goddard Space Flight Center, Greenbelt, MD (United States)] [and others

    1999-02-01

    The authors report on the performance of a CdZnTe (CZT) array readout by an XA (X-ray imaging chip produced at the AMS foundry) application specific readout chip (ASIC). The array was designed and fabricated at NASA/Goddard Space Flight Center (GSFC) as a prototype for the Burst Arc-Second Imaging and Spectroscopy gamma-ray instrument. The XA ASIC was obtained from Integrated Detector and Electronics (IDE), in Norway. Performance characteristics and spectral data for {sup 241}Am are presented both at room temperature and at {minus}20 C. The measured noise ({sigma}) was 2.5 keV at 60 keV at room temperature. This paper represents a progress report on work with the XA ASIC and CZT detectors. Work is continuing and in particular, larger arrays are planned for future NASA missions.

  5. Nuclear reactor pulse tracing using a CdZnTe electro-optic radiation detector

    Energy Technology Data Exchange (ETDEWEB)

    Nelson, Kyle A., E-mail: nuclearengg@gmail.com [S.M.A.R.T. Laboratory, Mechanical and Nuclear Engineering, Kansas State University, Manhattan KS 66506 (United States); Geuther, Jeffrey A. [TRIGA Mark II Nuclear Reactor, Mechanical and Nuclear Engineering, Kansas State University, Manhattan KS 66506 (United States); Neihart, James L.; Riedel, Todd A. [S.M.A.R.T. Laboratory, Mechanical and Nuclear Engineering, Kansas State University, Manhattan KS 66506 (United States); Rojeski, Ronald A. [Nanometrics, Inc., 1550 Buckeye Drive, Milpitas CA 95035 (United States); Ugorowski, Philip B.; McGregor, Douglas S. [S.M.A.R.T. Laboratory, Mechanical and Nuclear Engineering, Kansas State University, Manhattan KS 66506 (United States)

    2012-07-11

    CdZnTe has previously been shown to operate as an electro-optic radiation detector by utilizing the Pockels effect to measure steady-state nuclear reactor power levels. In the present work, the detector response to reactor power excursion experiments was investigated. Peak power levels during an excursion were predicted to be between 965 MW and 1009 MW using the Fuchs-Nordheim and Fuchs-Hansen models and confirmed with experimental data from the Kansas State University TRIGA Mark II nuclear reactor. The experimental arrangement of the Pockels cell detector includes collimated laser light passing through a transparent birefringent crystal, located between crossed polarizers, and focused upon a photodiode. The birefringent crystal, CdZnTe in this case, is placed in a neutron beam emanating from a nuclear reactor beam port. After obtaining the voltage-dependent Pockels characteristic response curve with a photodiode, neutron measurements were conducted from reactor pulses with the Pockels cell set at the 1/4 and 3/4 wave bias voltages. The detector responses to nuclear reactor pulses were recorded in real-time using data logging electronics, each showing a sharp increase in photodiode current for the 1/4 wave bias, and a sharp decrease in photodiode current for the 3/4 wave bias. The polarizers were readjusted to equal angles in which the maximum light transmission occurred at 0 V bias, thereby, inverting the detector response to reactor pulses. A high sample rate oscilloscope was also used to more accurately measure the FWHM of the pulse from the electro-optic detector, 64 ms, and is compared to the experimentally obtained FWHM of 16.0 ms obtained with the {sup 10}B-lined counter.

  6. Hemoglobin Drift after Cardiac Surgery

    Science.gov (United States)

    George, Timothy J.; Beaty, Claude A.; Kilic, Arman; Haggerty, Kara A.; Frank, Steven M.; Savage, William J.; Whitman, Glenn J.

    2013-01-01

    Introduction Recent literature suggests that a restrictive approach to red blood cell transfusions is associated with improved outcomes in cardiac surgery (CS) patients. Even in the absence of bleeding, intravascular fluid shifts cause hemoglobin levels to drift postoperatively, possibly confounding the decision to transfuse. We undertook this study to define the natural progression of hemoglobin levels in postoperative CS patients. Methods We included all CS patients from 10/10-03/11 who did not receive a postoperative transfusion. Primary stratification was by intraoperative transfusion status. Change in hemoglobin was evaluated relative to the initial postoperative hemoglobin. Maximal drift was defined as the maximum minus the minimum hemoglobin for a given hospitalization. Final drift was defined as the difference between initial and discharge hemoglobin. Results Our final cohort included 199 patients, 71(36%) received an intraoperative transfusion while 128(64%) did not. The average initial and final hemoglobin for all patients were 11.0±1.4g/dL and 9.9±1.3g/dL, respectively, an final drift of 1.1±1.4g/dL. The maximal drift was 1.8±1.1g/dL and was similar regardless of intraoperative transfusion status(p=0.9). Although all patients’ hemoglobin initially dropped, 79% of patients reached a nadir and experienced a mean recovery of 0.7±0.7g/dL by discharge. On multivariable analysis, increasing CPB time was significantly associated with total hemoglobin drift(Coefficient/hour: 0.3[0.1–0.5]g/dL, p=0.02). Conclusions In this first report of hemoglobin drift following CS, although all postoperative patients experienced downward hemoglobin drift, 79% of patients exhibited hemoglobin recovery prior to discharge. Physicians should consider the eventual upward hemoglobin drift prior to administering red cell transfusions. PMID:22609121

  7. 3-dimensional Oil Drift Simulations

    Science.gov (United States)

    Wettre, C.; Reistad, M.; Hjøllo, B.Å.

    Simulation of oil drift has been an ongoing activity at the Norwegian Meteorological Institute since the 1970's. The Marine Forecasting Centre provides a 24-hour service for the Norwegian Pollution Control Authority and the oil companies operating in the Norwegian sector. The response time is 30 minutes. From 2002 the service is extended to simulation of oil drift from oil spills in deep water, using the DeepBlow model developed by SINTEF Applied Chemistry. The oil drift model can be applied both for instantaneous and continuous releases. The changes in the mass of oil and emulsion as a result of evaporation and emulsion are computed. For oil spill at deep water, hydrate formation and gas dissolution are taken into account. The properties of the oil depend on the oil type, and in the present version 64 different types of oil can be simulated. For accurate oil drift simulations it is important to have the best possible data on the atmospheric and oceanic conditions. The oil drift simulations at the Norwegian Meteorological Institute are always based on the most updated data from numerical models of the atmosphere and the ocean. The drift of the surface oil is computed from the vectorial sum of the surface current from the ocean model and the wave induced Stokes drift computed from wave energy spectra from the wave prediction model. In the new model the current distribution with depth is taken into account when calculating the drift of the dispersed oil droplets. Salinity and temperature profiles from the ocean model are needed in the DeepBlow model. The result of the oil drift simulations can be plotted on sea charts used for navigation, either as trajectory plots or particle plots showing the situation at a given time. The results can also be sent as data files to be included in the user's own GIS system.

  8. Improving Photometry and Stellar Signal Preservation with Pixel-Level Systematic Error Correction

    Science.gov (United States)

    Kolodzijczak, Jeffrey J.; Smith, Jeffrey C.; Jenkins, Jon M.

    2013-01-01

    The Kepler Mission has demonstrated that excellent stellar photometric performance can be achieved using apertures constructed from optimally selected CCD pixels. The clever methods used to correct for systematic errors, while very successful, still have some limitations in their ability to extract long-term trends in stellar flux. They also leave poorly correlated bias sources, such as drifting moiré pattern, uncorrected. We will illustrate several approaches where applying systematic error correction algorithms to the pixel time series, rather than the co-added raw flux time series, provide significant advantages. Examples include, spatially localized determination of time varying moiré pattern biases, greater sensitivity to radiation-induced pixel sensitivity drops (SPSDs), improved precision of co-trending basis vectors (CBV), and a means of distinguishing the stellar variability from co-trending terms even when they are correlated. For the last item, the approach enables physical interpretation of appropriately scaled coefficients derived in the fit of pixel time series to the CBV as linear combinations of various spatial derivatives of the pixel response function (PRF). We demonstrate that the residuals of a fit of soderived pixel coefficients to various PRF-related components can be deterministically interpreted in terms of physically meaningful quantities, such as the component of the stellar flux time series which is correlated with the CBV, as well as, relative pixel gain, proper motion and parallax. The approach also enables us to parameterize and assess the limiting factors in the uncertainties in these quantities.

  9. CMOS pixel sensors on high resistive substrate for high-rate, high-radiation environments

    Science.gov (United States)

    Hirono, Toko; Barbero, Marlon; Breugnon, Patrick; Godiot, Stephanie; Gonella, Laura; Hemperek, Tomasz; Hügging, Fabian; Krüger, Hans; Liu, Jian; Pangaud, Patrick; Peric, Ivan; Pohl, David-Leon; Rozanov, Alexandre; Rymaszewski, Piotr; Wang, Anqing; Wermes, Norbert

    2016-09-01

    A depleted CMOS active pixel sensor (DMAPS) has been developed on a substrate with high resistivity in a high voltage process. High radiation tolerance and high time resolution can be expected because of the charge collection by drift. A prototype of DMAPS was fabricated in a 150 nm process by LFoundry. Two variants of the pixel layout were tested, and the measured depletion depths of the variants are 166 μm and 80 μm. We report the results obtained with the prototype fabricated in this technology.

  10. CMOS pixel sensors on high resistive substrate for high-rate, high-radiation environments

    Energy Technology Data Exchange (ETDEWEB)

    Hirono, Toko, E-mail: thirono@uni-bonn.de [Physikalisches Institute der Universität Bonn, Bonn (Germany); Barbero, Marlon; Breugnon, Patrick; Godiot, Stephanie [CPPM, Aix-Marseille Universite, CNRS/IN2P3, Marseille (France); Gonella, Laura; Hemperek, Tomasz; Hügging, Fabian; Krüger, Hans [Physikalisches Institute der Universität Bonn, Bonn (Germany); Liu, Jian; Pangaud, Patrick [CPPM, Aix-Marseille Universite, CNRS/IN2P3, Marseille (France); Peric, Ivan [IPE, Karlsruher Institut für Technologie, Karlsruhe (Germany); Pohl, David-Leon [Physikalisches Institute der Universität Bonn, Bonn (Germany); Rozanov, Alexandre [CPPM, Aix-Marseille Universite, CNRS/IN2P3, Marseille (France); Rymaszewski, Piotr [Physikalisches Institute der Universität Bonn, Bonn (Germany); Wang, Anqing [CPPM, Aix-Marseille Universite, CNRS/IN2P3, Marseille (France); Wermes, Norbert [Physikalisches Institute der Universität Bonn, Bonn (Germany)

    2016-09-21

    A depleted CMOS active pixel sensor (DMAPS) has been developed on a substrate with high resistivity in a high voltage process. High radiation tolerance and high time resolution can be expected because of the charge collection by drift. A prototype of DMAPS was fabricated in a 150 nm process by LFoundry. Two variants of the pixel layout were tested, and the measured depletion depths of the variants are 166 μm and 80 μm. We report the results obtained with the prototype fabricated in this technology.

  11. Status of the ATLAS pixel detector

    CERN Document Server

    Saavedra Aldo, F

    2005-01-01

    The ATLAS pixel detector is currently being constructed and will be installed in 2006 to be ready for commissioning at the Large Hadron Collider. The complete pixel detector is composed of three concentric barrels and six disks that are populated by 1744 ATLAS Pixel modules. The main components of the pixel module are the readout electronics and the silicon sensor whose active region is instrumented with rectangular pixels. The module has been designed to be able to survive 10 years of operation within the ATLAS detector. A brief description of the pixel detector will be presented with results and problems encountered during the production stage.

  12. Investigation of CdZnTe and LiNbO{sub 3} as electro-optic neutron detectors

    Energy Technology Data Exchange (ETDEWEB)

    Nelson, Kyle A.; Edwards, Nathan [S.M.A.R.T. Laboratory, Mechanical and Nuclear Engineering Department, Kansas State University, Manhattan, KS 66506 (United States); Harrison, Mark J. [Nuclear and Radiological Engineering, University of Florida, 202 NSB, Gainesville, FL 32611 (United States); Kargar, Alireza; McNeil, Walter J. [S.M.A.R.T. Laboratory, Mechanical and Nuclear Engineering Department, Kansas State University, Manhattan, KS 66506 (United States); Rojeski, Ronald A. [Cymer, Inc., San Diego, CA 92127 (United States); McGregor, Douglas S., E-mail: mcgregor@ksu.ed [S.M.A.R.T. Laboratory, Mechanical and Nuclear Engineering Department, Kansas State University, Manhattan, KS 66506 (United States)

    2010-08-21

    An alternative method for the detection of thermal neutrons has been investigated utilizing the Pockels effect with CdZnTe and LiNbO{sub 3}. A photodiode was used to indicate a change in light intensity transmitted through an assembly consisting of polarizer, Pockels cell, and analyzer. Ionization due to neutron reaction products can perturb an established electric field within the cell, thus changing the transmitted light intensity through the assembly. The CdZnTe cell demonstrated a repeatable change in transmitted light intensity, increasing with neutron flux, marking the first recorded use of this technology to detect neutrons. However, the LiNbO{sub 3} cell gave no response to neutron irradiation, and is assumed to be a result of the extremely short carrier lifetimes found in the material.

  13. The crystalline quality distribution in CdZnTe single crystal correlated to the interface shape during growth

    Energy Technology Data Exchange (ETDEWEB)

    Azoulay, M.; Rotter, S.; Gafni, G. (Soreq Nuclear Research Center, Yavne (Israel)); Roth, M. (School of Applied Science and Technology, Hebrew Univ. of Jerusalem (Israel))

    1992-02-01

    Crystalline quality of CdZnTe single crystals grown by the vertical gradient freeze (VGF) method has been evaluated using the double crystal rocking curve (DCRC) analysis and etch pits density (EPD) measurements. The full width at half maximum (HWHM) values of the DCRCs vary within 40% while the EPD values range from 2 to 8 x 10{sup 4} cm{sup -2} along the crystal growth axis. Best results are obtained for the central part of the crystals, where the growth interface exhibits a nearly planar shape. The results obtained have been used for practical implications with regard to the use of CdZnTe crystals as a substrate material for HgCdTe thin films growth. (orig.).

  14. Spatial characterization of monolithic multi-element Silicon-Drift-Detectors for X-ray spectroscopic applications

    CERN Document Server

    Kappen, P; Hansen, K; Reckleben, C; Lechner, P; Strüder, L; Materlik, G

    2001-01-01

    Spatially resolved spectroscopic measurements with a 10 and 20 mu m pencil beam have been performed on a monolithic 7-element Silicon-Drift-Detector (SDD). Detailed studies are shown of the modification of the spectroscopic response at pixel edges and pixel centre. The results give quantitative insight into the local SDD performance. A simple model predicts global properties (e.g. peak-to-background ratio) of larger SDD arrays, like the 61-element detector currently under development.

  15. Fully depleted CMOS pixel sensor development and potential applications

    Energy Technology Data Exchange (ETDEWEB)

    Baudot, J.; Kachel, M. [Universite de Strasbourg, IPHC, 23 rue du Loess 67037 Strasbourg (France); CNRS, UMR7178, 67037 Strasbourg (France)

    2015-07-01

    CMOS pixel sensors are often opposed to hybrid pixel sensors due to their very different sensitive layer. In standard CMOS imaging processes, a thin (about 20 μm) low resistivity epitaxial layer acts as the sensitive volume and charge collection is mostly driven by thermal agitation. In contrast, the so-called hybrid pixel technology exploits a thick (typically 300 μm) silicon sensor with high resistivity allowing for the depletion of this volume, hence charges drift toward collecting electrodes. But this difference is fading away with the recent availability of some CMOS imaging processes based on a relatively thick (about 50 μm) high resistivity epitaxial layer which allows for full depletion. This evolution extents the range of applications for CMOS pixel sensors where their known assets, high sensitivity and granularity combined with embedded signal treatment, could potentially foster breakthrough in detection performances for specific scientific instruments. One such domain is the Xray detection for soft energies, typically below 10 keV, where the thin sensitive layer was previously severely impeding CMOS sensor usage. Another application becoming realistic for CMOS sensors, is the detection in environment with a high fluence of non-ionizing radiation, such as hadron colliders. However, when considering highly demanding applications, it is still to be proven that micro-circuits required to uniformly deplete the sensor at the pixel level, do not mitigate the sensitivity and efficiency required. Prototype sensors in two different technologies with resistivity higher than 1 kΩ, sensitive layer between 40 and 50 μm and featuring pixel pitch in the range 25 to 50 μm, have been designed and fabricated. Various biasing architectures were adopted to reach full depletion with only a few volts. Laboratory investigations with three types of sources (X-rays, β-rays and infrared light) demonstrated the validity of the approach with respect to depletion, keeping a

  16. Effect of Pixel's Spatial Characteristics on Recognition of Isolated Pixelized Chinese Character.

    Science.gov (United States)

    Yang, Kun; Liu, Shuang; Wang, Hong; Liu, Wei; Wu, Yaowei

    2015-01-01

    The influence of pixel's spatial characteristics on recognition of isolated Chinese character was investigated using simulated prosthestic vision. The accuracy of Chinese character recognition with 4 kinds of pixel number (6*6, 8*8, 10*10, and 12*12 pixel array) and 3 kinds of pixel shape (Square, Dot and Gaussian) and different pixel spacing were tested through head-mounted display (HMD). A captured image of Chinese characters in font style of Hei were pixelized with Square, Dot and Gaussian pixel. Results showed that pixel number was the most important factor which could affect the recognition of isolated pixelized Chinese Chartars and the accuracy of recognition increased with the addition of pixel number. 10*10 pixel array could provide enough information for people to recognize an isolated Chinese character. At low resolution (6*6 and 8*8 pixel array), there were little difference of recognition accuracy between different pixel shape and different pixel spacing. While as for high resolution (10*10 and 12*12 pixel array), the fluctuation of pixel shape and pixel spacing could not affect the performance of recognition of isolated pixelized Chinese Character.

  17. Live-monitoring of Te inclusions laser-induced thermo-diffusion and annealing in CdZnTe crystals

    Energy Technology Data Exchange (ETDEWEB)

    Zappettini, A.; Zambelli, N.; Benassi, G.; Calestani, D. [Istituto Materiali Elettronica e Magnetismo – Consiglio Nazionale delle Ricerche, Parma (Italy); Pavesi, M. [Istituto Materiali Elettronica e Magnetismo – Consiglio Nazionale delle Ricerche, Parma (Italy); Istituto di Fisica e Scienze della Terra, Università degli Studi di Parma, Parma (Italy)

    2014-06-23

    The presence of Te inclusions is one of the main factors limiting performances of CdZnTe crystals as X-ray detectors. We show that by means of infrared laser radiation it is possible to move and anneal tellurium inclusions exploiting a thermo-diffusion mechanism. The process is studied live during irradiation by means of an optical microscope equipment. Experimental conditions, and, in particular, energy laser fluence, for annealing inclusions of different dimensions are determined.

  18. The ATLAS Silicon Pixel Sensors

    CERN Document Server

    Alam, M S; Einsweiler, K F; Emes, J; Gilchriese, M G D; Joshi, A; Kleinfelder, S A; Marchesini, R; McCormack, F; Milgrome, O; Palaio, N; Pengg, F; Richardson, J; Zizka, G; Ackers, M; Andreazza, A; Comes, G; Fischer, P; Keil, M; Klasen, V; Kühl, T; Meuser, S; Ockenfels, W; Raith, B; Treis, J; Wermes, N; Gössling, C; Hügging, F G; Wüstenfeld, J; Wunstorf, R; Barberis, D; Beccherle, R; Darbo, G; Gagliardi, G; Gemme, C; Morettini, P; Musico, P; Osculati, B; Parodi, F; Rossi, L; Blanquart, L; Breugnon, P; Calvet, D; Clemens, J-C; Delpierre, P A; Hallewell, G D; Laugier, D; Mouthuy, T; Rozanov, A; Valin, I; Aleppo, M; Caccia, M; Ragusa, F; Troncon, C; Lutz, Gerhard; Richter, R H; Rohe, T; Brandl, A; Gorfine, G; Hoeferkamp, M; Seidel, SC; Boyd, GR; Skubic, P L; Sícho, P; Tomasek, L; Vrba, V; Holder, M; Ziolkowski, M; D'Auria, S; del Papa, C; Charles, E; Fasching, D; Becks, K H; Lenzen, G; Linder, C

    2001-01-01

    Prototype sensors for the ATLAS silicon pixel detector have been developed. The design of the sensors is guided by the need to operate them in the severe LHC radiation environment at up to several hundred volts while maintaining a good signal-to-noise ratio, small cell size, and minimal multiple scattering. The ability to be operated under full bias for electrical characterization prior to the attachment of the readout integrated circuit electronics is also desired.

  19. SAR Image Complex Pixel Representations

    Energy Technology Data Exchange (ETDEWEB)

    Doerry, Armin W. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-03-01

    Complex pixel values for Synthetic Aperture Radar (SAR) images of uniform distributed clutter can be represented as either real/imaginary (also known as I/Q) values, or as Magnitude/Phase values. Generally, these component values are integers with limited number of bits. For clutter energy well below full-scale, Magnitude/Phase offers lower quantization noise than I/Q representation. Further improvement can be had with companding of the Magnitude value.

  20. CMOS digital pixel sensors: technology and applications

    Science.gov (United States)

    Skorka, Orit; Joseph, Dileepan

    2014-04-01

    CMOS active pixel sensor technology, which is widely used these days for digital imaging, is based on analog pixels. Transition to digital pixel sensors can boost signal-to-noise ratios and enhance image quality, but can increase pixel area to dimensions that are impractical for the high-volume market of consumer electronic devices. There are two main approaches to digital pixel design. The first uses digitization methods that largely rely on photodetector properties and so are unique to imaging. The second is based on adaptation of a classical analog-to-digital converter (ADC) for in-pixel data conversion. Imaging systems for medical, industrial, and security applications are emerging lower-volume markets that can benefit from these in-pixel ADCs. With these applications, larger pixels are typically acceptable, and imaging may be done in invisible spectral bands.

  1. Mapping Electrical Crosstalk in Pixelated Sensor Arrays

    Science.gov (United States)

    Seshadri, Suresh (Inventor); Cole, David (Inventor); Smith, Roger M (Inventor); Hancock, Bruce R. (Inventor)

    2013-01-01

    The effects of inter pixel capacitance in a pixilated array may be measured by first resetting all pixels in the array to a first voltage, where a first image is read out, followed by resetting only a subset of pixels in the array to a second voltage, where a second image is read out, where the difference in the first and second images provide information about the inter pixel capacitance. Other embodiments are described and claimed.

  2. Mapping Electrical Crosstalk in Pixelated Sensor Arrays

    Science.gov (United States)

    Seshadri, Suresh (Inventor); Cole, David (Inventor); Smith, Roger M. (Inventor); Hancock, Bruce R. (Inventor)

    2017-01-01

    The effects of inter pixel capacitance in a pixilated array may be measured by first resetting all pixels in the array to a first voltage, where a first image is read out, followed by resetting only a subset of pixels in the array to a second voltage, where a second image is read out, where the difference in the first and second images provide information about the inter pixel capacitance. Other embodiments are described and claimed.

  3. CVD diamond pixel detectors for LHC experiments

    Energy Technology Data Exchange (ETDEWEB)

    Wedenig, R.; Adam, W.; Bauer, C.; Berdermann, E.; Bergonzo, P.; Bogani, F.; Borchi, E.; Brambilla, A.; Bruzzi, M.; Colledani, C.; Conway, J.; Dabrowski, W.; Delpierre, P.; Deneuville, A.; Dulinski, W.; Eijk, B. van; Fallou, A.; Fizzotti, F.; Foulon, F.; Friedl, M.; Gan, K.K.; Gheeraert, E.; Grigoriev, E.; Hallewell, G.; Hall-Wilton, R.; Han, S.; Hartjes, F.; Hrubec, J.; Husson, D.; Kagan, H.; Kania, D.; Kaplon, J.; Karl, C.; Kass, R.; Knoepfle, K.T.; Krammer, M.; Logiudice, A.; Lu, R.; Manfredi, P.F.; Manfredotti, C.; Marshall, R.D.; Meier, D.; Mishina, M.; Oh, A.; Pan, L.S.; Palmieri, V.G.; Pernicka, M.; Peitz, A.; Pirollo, S.; Polesello, P.; Pretzl, K.; Procario, M.; Re, V.; Riester, J.L.; Roe, S.; Roff, D.; Rudge, A.; Runolfsson, O.; Russ, J.; Schnetzer, S.; Sciortino, S.; Speziali, V.; Stelzer, H.; Stone, R.; Suter, B.; Tapper, R.J.; Tesarek, R.; Trawick, M.; Trischuk, W.; Vittone, E.; Wagner, A.; Walsh, A.M.; Weilhammer, P.; White, C.; Zeuner, W.; Ziock, H.; Zoeller, M.; Blanquart, L.; Breugnion, P.; Charles, E.; Ciocio, A.; Clemens, J.C.; Dao, K.; Einsweiler, K.; Fasching, D.; Fischer, P.; Joshi, A.; Keil, M.; Klasen, V.; Kleinfelder, S.; Laugier, D.; Meuser, S.; Milgrome, O.; Mouthuy, T.; Richardson, J.; Sinervo, P.; Treis, J.; Wermes, N

    1999-08-01

    This paper reviews the development of CVD diamond pixel detectors. The preparation of the diamond pixel sensors for bump-bonding to the pixel readout electronics for the LHC and the results from beam tests carried out at CERN are described.

  4. CMS has a heart of pixels

    CERN Multimedia

    2003-01-01

    In the immediate vicinity of the collision point, CMS will be equipped with pixel detectors consisting of no fewer than 50 million pixels measuring 150 microns along each side. Each of the pixels, which receive the signal, is connected to its own electronic circuit by a tiny sphere (seen here in the electron microscope image) measuring 15 to 20 microns in diameter.

  5. The Drifting Star

    Science.gov (United States)

    2008-04-01

    By studying in great detail the 'ringing' of a planet-harbouring star, a team of astronomers using ESO's 3.6-m telescope have shown that it must have drifted away from the metal-rich Hyades cluster. This discovery has implications for theories of star and planet formation, and for the dynamics of our Milky Way. ESO PR Photo 09a/08 ESO PR Photo 09a/08 Iota Horologii The yellow-orange star Iota Horologii, located 56 light-years away towards the southern Horologium ("The Clock") constellation, belongs to the so-called "Hyades stream", a large number of stars that move in the same direction. Previously, astronomers using an ESO telescope had shown that the star harbours a planet, more than 2 times as large as Jupiter and orbiting in 320 days (ESO 12/99). But until now, all studies were unable to pinpoint the exact characteristics of the star, and hence to understand its origin. A team of astronomers, led by Sylvie Vauclair from the University of Toulouse, France, therefore decided to use the technique of 'asteroseismology' to unlock the star's secrets. "In the same way as geologists monitor how seismic waves generated by earthquakes propagate through the Earth and learn about the inner structure of our planet, it is possible to study sound waves running through a star, which forms a sort of large, spherical bell," says Vauclair. The 'ringing' from this giant musical instrument provides astronomers with plenty of information about the physical conditions in the star's interior. And to 'listen to the music', the astronomers used one of the best instruments available. The observations were conducted in November 2006 during 8 consecutive nights with the state-of-the-art HARPS spectrograph mounted on the ESO 3.6-m telescope at La Silla. Up to 25 'notes' could be identified in the unique dataset, most of them corresponding to waves having a period of about 6.5 minutes. These observations allowed the astronomers to obtain a very precise portrait of Iota Horologii: its

  6. Effect of thickness on physical properties of electron beam vacuum evaporated CdZnTe thin films for tandem solar cells

    Science.gov (United States)

    Chander, Subhash; Dhaka, M. S.

    2016-10-01

    The thickness and physical properties of electron beam vacuum evaporated CdZnTe thin films have been optimized in the present work. The films of thickness 300 nm and 400 nm were deposited on ITO coated glass substrates and subjected to different characterization tools like X-ray diffraction (XRD), UV-Vis spectrophotometer, source meter and scanning electron microscopy (SEM) to investigate the structural, optical, electrical and surface morphological properties respectively. The XRD results show that the as-deposited CdZnTe thin films have zinc blende cubic structure and polycrystalline in nature with preferred orientation (111). Different structural parameters are also evaluated and discussed. The optical study reveals that the optical transition is found to be direct and energy band gap is decreased for higher thickness. The transmittance is found to increase with thickness and red shift observed which is suitable for CdZnTe films as an absorber layer in tandem solar cells. The current-voltage characteristics of deposited films show linear behavior in both forward and reverse directions as well as the conductivity is increased for higher film thickness. The SEM studies show that the as-deposited CdZnTe thin films are found to be homogeneous, uniform, small circle-shaped grains and free from crystal defects. The experimental results confirm that the film thickness plays an important role to optimize the physical properties of CdZnTe thin films for tandem solar cell applications as an absorber layer.

  7. Quantifying Particle Numbers and Mass Flux in Drifting Snow

    Science.gov (United States)

    Crivelli, Philip; Paterna, Enrico; Horender, Stefan; Lehning, Michael

    2016-12-01

    We compare two of the most common methods of quantifying mass flux, particle numbers and particle-size distribution for drifting snow events, the snow-particle counter (SPC), a laser-diode-based particle detector, and particle tracking velocimetry based on digital shadowgraphic imaging. The two methods were correlated for mass flux and particle number flux. For the SPC measurements, the device was calibrated by the manufacturer beforehand. The shadowgrapic imaging method measures particle size and velocity directly from consecutive images, and before each new test the image pixel length is newly calibrated. A calibration study with artificially scattered sand particles and glass beads provides suitable settings for the shadowgraphical imaging as well as obtaining a first correlation of the two methods in a controlled environment. In addition, using snow collected in trays during snowfall, several experiments were performed to observe drifting snow events in a cold wind tunnel. The results demonstrate a high correlation between the mass flux obtained for the calibration studies (r ≥slant 0.93) and good correlation for the drifting snow experiments (r ≥slant 0.81). The impact of measurement settings is discussed in order to reliably quantify particle numbers and mass flux in drifting snow. The study was designed and performed to optimize the settings of the digital shadowgraphic imaging system for both the acquisition and the processing of particles in a drifting snow event. Our results suggest that these optimal settings can be transferred to different imaging set-ups to investigate sediment transport processes.

  8. Quantifying Particle Numbers and Mass Flux in Drifting Snow

    Science.gov (United States)

    Crivelli, Philip; Paterna, Enrico; Horender, Stefan; Lehning, Michael

    2016-06-01

    We compare two of the most common methods of quantifying mass flux, particle numbers and particle-size distribution for drifting snow events, the snow-particle counter (SPC), a laser-diode-based particle detector, and particle tracking velocimetry based on digital shadowgraphic imaging. The two methods were correlated for mass flux and particle number flux. For the SPC measurements, the device was calibrated by the manufacturer beforehand. The shadowgrapic imaging method measures particle size and velocity directly from consecutive images, and before each new test the image pixel length is newly calibrated. A calibration study with artificially scattered sand particles and glass beads provides suitable settings for the shadowgraphical imaging as well as obtaining a first correlation of the two methods in a controlled environment. In addition, using snow collected in trays during snowfall, several experiments were performed to observe drifting snow events in a cold wind tunnel. The results demonstrate a high correlation between the mass flux obtained for the calibration studies (r ≥slant 0.93 ) and good correlation for the drifting snow experiments (r ≥slant 0.81 ). The impact of measurement settings is discussed in order to reliably quantify particle numbers and mass flux in drifting snow. The study was designed and performed to optimize the settings of the digital shadowgraphic imaging system for both the acquisition and the processing of particles in a drifting snow event. Our results suggest that these optimal settings can be transferred to different imaging set-ups to investigate sediment transport processes.

  9. Caliste 256: A CdTe imaging spectrometer for space science with a 580 {mu}m pixel pitch

    Energy Technology Data Exchange (ETDEWEB)

    Limousin, O., E-mail: olimousin@cea.fr [CEA/Saclay, DSM/Irfu/Service d' Astrophysique, F-91191 Gif-sur-Yvette (France); Lugiez, F.; Gevin, O. [CEA/Saclay, DSM/Irfu/Service d' Electronique Detecteurs et Informatique, F-91191 Gif-sur-Yvette (France); Meuris, A.; Blondel, C. [CEA/Saclay, DSM/Irfu/Service d' Astrophysique, F-91191 Gif-sur-Yvette (France); Delagnes, E. [CEA/Saclay, DSM/Irfu/Service d' Electronique Detecteurs et Informatique, F-91191 Gif-sur-Yvette (France); Donati, M.; Le Mer, I.; Martignac, J.; Pinsard, F. [CEA/Saclay, DSM/Irfu/Service d' Astrophysique, F-91191 Gif-sur-Yvette (France); Vassal, M.C.; Bocage, R.; Soufflet, F. [3D Plus, 641 rue Helene Boucher, F-78532 Buc (France)

    2011-08-11

    Caliste project aims at hybridizing 1 cm{sup 2} CdTe or CdZnTe pixel detectors with low-noise full custom front-end electronics, in a single component standing in a 1x1x2 cm{sup 3} volume. Caliste device is 4-side buttable and can be used as elementary detection unit of a large mosaic to form a hard X-ray focal plane of any size and shape. Caliste is especially designed to match astronomical space mission requirements and its design takes into account environmental constraints, radiation environment in particular. This new imaging spectrometer for hard X-rays detection offers high spectral and spatial resolution together with accurate time-tagging capability and low dead time. Caliste concept relies on a 3D hybridization technology that consists in stacking full custom ASICs perpendicular to the detection surface into a single component. This technique simultaneously permits to realize a buttable imager and to enhance performance and uniformity response. Our last prototype is called Caliste 256 and integrates 16x16 pixels array, 580 {mu}m pitch and 256 corresponding independent spectroscopy channels. This paper presents Caliste 256 design and properties. We emphasize spectral performance and demonstrate spectral resolution capabilities better than 1 keV FWHM at 60 keV.

  10. Making a trillion pixels dance

    Science.gov (United States)

    Singh, Vivek; Hu, Bin; Toh, Kenny; Bollepalli, Srinivas; Wagner, Stephan; Borodovsky, Yan

    2008-03-01

    In June 2007, Intel announced a new pixelated mask technology. This technology was created to address the problem caused by the growing gap between the lithography wavelength and the feature sizes patterned with it. As this gap has increased, the quality of the image has deteriorated. About a decade ago, Optical Proximity Correction (OPC) was introduced to bridge this gap, but as this gap continued to increase, one could not rely on the same basic set of techniques to maintain image quality. The computational lithography group at Intel sought to alleviate this problem by experimenting with additional degrees of freedom within the mask. This paper describes the resulting pixelated mask technology, and some of the computational methods used to create it. The first key element of this technology is a thick mask model. We realized very early in the development that, unlike traditional OPC methods, the pixelated mask would require a very accurate thick mask model. Whereas in the traditional methods, one can use the relatively coarse approximations such as the boundary layer method, use of such techniques resulted not just in incorrect sizing of parts of the pattern, but in whole features missing. We built on top of previously published domain decomposition methods, and incorporated limitations of the mask manufacturing process, to create an accurate thick mask model. Several additional computational techniques were invoked to substantially increase the speed of this method to a point that it was feasible for full chip tapeout. A second key element of the computational scheme was the comprehension of mask manufacturability, including the vital issue of the number of colors in the mask. While it is obvious that use of three or more colors will give the best image, one has to be practical about projecting mask manufacturing capabilities for such a complex mask. To circumvent this serious issue, we eventually settled on a two color mask - comprising plain glass and etched

  11. In-Drift Microbial Communities

    Energy Technology Data Exchange (ETDEWEB)

    D. Jolley

    2000-11-09

    As directed by written work direction (CRWMS M and O 1999f), Performance Assessment (PA) developed a model for microbial communities in the engineered barrier system (EBS) as documented here. The purpose of this model is to assist Performance Assessment and its Engineered Barrier Performance Section in modeling the geochemical environment within a potential repository drift for TSPA-SR/LA, thus allowing PA to provide a more detailed and complete near-field geochemical model and to answer the key technical issues (KTI) raised in the NRC Issue Resolution Status Report (IRSR) for the Evolution of the Near Field Environment (NFE) Revision 2 (NRC 1999). This model and its predecessor (the in-drift microbial communities model as documented in Chapter 4 of the TSPA-VA Technical Basis Document, CRWMS M and O 1998a) was developed to respond to the applicable KTIs. Additionally, because of the previous development of the in-drift microbial communities model as documented in Chapter 4 of the TSPA-VA Technical Basis Document (CRWMS M and O 1998a), the M and O was effectively able to resolve a previous KTI concern regarding the effects of microbial processes on seepage and flow (NRC 1998). This document supercedes the in-drift microbial communities model as documented in Chapter 4 of the TSPA-VA Technical Basis Document (CRWMS M and O 1998a). This document provides the conceptual framework of the revised in-drift microbial communities model to be used in subsequent performance assessment (PA) analyses.

  12. High Dynamic Range Pixel Array Detector for Scanning Transmission Electron Microscopy.

    Science.gov (United States)

    Tate, Mark W; Purohit, Prafull; Chamberlain, Darol; Nguyen, Kayla X; Hovden, Robert; Chang, Celesta S; Deb, Pratiti; Turgut, Emrah; Heron, John T; Schlom, Darrell G; Ralph, Daniel C; Fuchs, Gregory D; Shanks, Katherine S; Philipp, Hugh T; Muller, David A; Gruner, Sol M

    2016-02-01

    We describe a hybrid pixel array detector (electron microscope pixel array detector, or EMPAD) adapted for use in electron microscope applications, especially as a universal detector for scanning transmission electron microscopy. The 128×128 pixel detector consists of a 500 µm thick silicon diode array bump-bonded pixel-by-pixel to an application-specific integrated circuit. The in-pixel circuitry provides a 1,000,000:1 dynamic range within a single frame, allowing the direct electron beam to be imaged while still maintaining single electron sensitivity. A 1.1 kHz framing rate enables rapid data collection and minimizes sample drift distortions while scanning. By capturing the entire unsaturated diffraction pattern in scanning mode, one can simultaneously capture bright field, dark field, and phase contrast information, as well as being able to analyze the full scattering distribution, allowing true center of mass imaging. The scattering is recorded on an absolute scale, so that information such as local sample thickness can be directly determined. This paper describes the detector architecture, data acquisition system, and preliminary results from experiments with 80-200 keV electron beams.

  13. High Dynamic Range Pixel Array Detector for Scanning Transmission Electron Microscopy

    CERN Document Server

    Tate, Mark W; Chamberlain, Darol; Nguyen, Kayla X; Hovden, Robert M; Chang, Celesta S; Deb, Pratiti; Turgut, Emrah; Heron, John T; Schlom, Darrell G; Ralph, Daniel C; Fuchs, Gregory D; Shanks, Katherine S; Philipp, Hugh T; Muller, David A; Gruner, Sol M

    2015-01-01

    We describe a hybrid pixel array detector (EMPAD - electron microscope pixel array detector) adapted for use in electron microscope applications, especially as a universal detector for scanning transmission electron microscopy. The 128 x 128 pixel detector consists of a 500 um thick silicon diode array bump-bonded pixel-by-pixel to an application-specific integrated circuit (ASIC). The in-pixel circuitry provides a 1,000,000:1 dynamic range within a single frame, allowing the direct electron beam to be imaged while still maintaining single electron sensitivity. A 1.1 kHz framing rate enables rapid data collection and minimizes sample drift distortions while scanning. By capturing the entire unsaturated diffraction pattern in scanning mode, one can simultaneously capture bright field, dark field, and phase contrast information, as well as being able to analyze the full scattering distribution, allowing true center of mass imaging. The scattering is recorded on an absolute scale, so that information such as loc...

  14. Optimization of control parameters of CdZnTe ACRT-Bridgman single crystal growth

    Institute of Scientific and Technical Information of China (English)

    2004-01-01

    [1]Kennedey, J. J., Amirtharaj, P. M., Boyd, P. R. Et al., Growth and characterization of Cd1-xZnxTe and Hg1-yZnyTe, J. Cryst. Growth, 1988, 86: 93-99.[2]Tanaka, A., Masa, Y., Seto, S. et al., Zinc and selenium co-doped CdTe substrates lattice matched to HgCdTe, J. Cryst. Growth, 1989, 94: 166-170.[3]Sen, S., Stanard, J. E., Developments in the bulk growth of Cd1-xZnxTe for substrates, Prog. Crystal Growth and Charact., 1994, 29: 253-273.[4]Azoulay, M., Rotter, S., Gafni, G. et al., Zinc segregation in CdZnTe grown under Cd/Zn partial pressure control, J. Cryst. Growth, 1992, 117: 276-280.[5]Lee, T. S., Lee, S. B., Kim, J. M. et al., Vertical Bridgman techniques to homogenize zinc composition of CdZnTe substrates, J. Electronic Materials, 1995, 24: 1057-1059.[6]Mühlberg, M., Rudolph, P., Genzel, C. Et al., Crystalline and chemical quality of CdTe and Cd1-xZnxTe grown by the Bridgman method in low temperature gradients, J. Cryst. Growth, 1990, 101: 275-280.[7]Cheuvart, P., El-Hanani, U., Schneider, D. et al., CdTe and CdZnTe crystal growth by horizontal Bridgman technique, J. Cryst. Growth, 1990, 101: 270-274.[8]Lu, Y. C., Shiau, J. J., Fiegelson, R. S. et al., Effect of vibrational stirring on the quality of Bridgman-grown CdTe, J. Cryst. Growth, 1990, 102: 807-813.[9]Butler, J. F., Doty, F. P., Apotovsky, B. Et al., γ-ray and X-ray detectors manufactured from Cd1-xZnxTe grown by a high-pressure Bridgman method, Mater. Sci. & Eng. B, 1993, 16: 291-295.[10]Capper, P., The role of accelerated crucible rotation in the growth of Hg1-xCdxTe and CdTe/CdZnTe, Prog. Crystal Growth and Charact., 1994, 28: 1-55.[11]Schulz-Dubois, E. O., Accelerated crucible rotation: hydrodynamics and stirring effect, J. Cryst. Growth, 1971, 12: 81-87.[12]Capper, P., Gosney, J. J. G., Jones, C. L. et al., Fluid flows in tall narrow containers by ACRT, Journal of Electronic Materials, 1986 15(6): 361-370.[13]Distanov, V. E., Kirdyashkin, A

  15. Development of SOI pixel detector in Cracow

    CERN Document Server

    Bugiel, Szymon; Glab, Sebastian; Idzik, Marek; Moron, Jakub; Kapusta, Piotr Julian; Kucewicz, Wojciech; Turala, Michal

    2015-01-01

    This paper presents the design of a new monolithic Silicon-On-Insulator pixel sensor in $200~nm$ SOI CMOS technology. The main application of the proposed pixel detector is the spectroscopy, but it can also be used for the minimum ionizing particle (MIP) tracking in particle physics experiments. For this reason few different versions of pixel cells are developed: a source-follower based pixel for tracking, a low noise pixel with preamplifier for spectroscopy, and a self-triggering pixel for time and amplitude measurements. In addition the design of a Successive Approximation Register Analog-to-Digital Converter (SAR ADC) is also presented. A 10-bit SAR ADC is developed for spectroscopic measurements and a lower resolution 6-bit SAR ADC is integrated in the pixel matrix as a column ADC, for tracking applications.

  16. Monte Carlo based performance assessment of different animal PET architectures using pixellated CZT detectors

    Energy Technology Data Exchange (ETDEWEB)

    Visvikis, D. [INSERM U650, LaTIM, University Hospital Medical School, F-29609 Brest (France)]. E-mail: Visvikis.Dimitris@univ-brest.fr; Lefevre, T. [INSERM U650, LaTIM, University Hospital Medical School, F-29609 Brest (France); Lamare, F. [INSERM U650, LaTIM, University Hospital Medical School, F-29609 Brest (France); Kontaxakis, G. [ETSI Telecomunicacion Universidad Politecnica de Madrid, Ciudad Universitaria, s/n 28040, Madrid (Spain); Santos, A. [ETSI Telecomunicacion Universidad Politecnica de Madrid, Ciudad Universitaria, s/n 28040, Madrid (Spain); Darambara, D. [Department of Physics, School of Engineering and Physical Sciences, University of Surrey, Guildford (United Kingdom)

    2006-12-20

    The majority of present position emission tomography (PET) animal systems are based on the coupling of high-density scintillators and light detectors. A disadvantage of these detector configurations is the compromise between image resolution, sensitivity and energy resolution. In addition, current combined imaging devices are based on simply placing back-to-back and in axial alignment different apparatus without any significant level of software or hardware integration. The use of semiconductor CdZnTe (CZT) detectors is a promising alternative to scintillators for gamma-ray imaging systems. At the same time CZT detectors have the potential properties necessary for the construction of a truly integrated imaging device (PET/SPECT/CT). The aims of this study was to assess the performance of different small animal PET scanner architectures based on CZT pixellated detectors and compare their performance with that of state of the art existing PET animal scanners. Different scanner architectures were modelled using GATE (Geant4 Application for Tomographic Emission). Particular scanner design characteristics included an overall cylindrical scanner format of 8 and 24 cm in axial and transaxial field of view, respectively, and a temporal coincidence window of 8 ns. Different individual detector modules were investigated, considering pixel pitch down to 0.625 mm and detector thickness from 1 to 5 mm. Modified NEMA NU2-2001 protocols were used in order to simulate performance based on mouse, rat and monkey imaging conditions. These protocols allowed us to directly compare the performance of the proposed geometries with the latest generation of current small animal systems. Results attained demonstrate the potential for higher NECR with CZT based scanners in comparison to scintillator based animal systems.

  17. High fidelity point-spread function retrieval in the presence of electrostatic, hysteretic pixel response

    CERN Document Server

    Rasmussen, Andrew; Lage, Craig; Antilogus, Pierre; Astier, Pierre; Doherty, Peter; Gilmore, Kirk; Kotov, Ivan; Lupton, Robert; Nomerotski, Andrei; O'Connor, Paul; Stubbs, Christopher; Tyson, Anthony; Walter, Christopher

    2016-01-01

    We employ electrostatic conversion drift calculations to match CCD pixel signal covariances observed in flat field exposures acquired using candidate sensor devices for the LSST Camera. We thus constrain pixel geometry distortions present at the end of integration, based on signal images recorded. We use available data from several operational voltage parameter settings to validate our understanding. Our primary goal is to optimize flux point-spread function (FPSF) estimation quantitatively, and thereby minimize sensor-induced errors which may limit performance in precision astronomy applications. We consider alternative compensation scenarios that will take maximum advantage of our understanding of this underlying mechanism in data processing pipelines currently under development. To quantitatively capture the pixel response in high-contrast/high dynamic range operational extrema, we propose herein some straightforward laboratory tests that involve altering the time order of source illumination on sensors, w...

  18. Drift tubes of Linac 2

    CERN Multimedia

    1977-01-01

    With the advent of the 800 MeV PS Booster in 1972, the original injector of the PS, a 50 MeV Alvarez-type proton linac, had reached its limits, in terms of intensity and stability. In 1973 one therefore decided to build a new linac (Linac 2), also with a drift-tube Alvarez structure and an energy of 50 MeV. It had a new Cockcroft-Walton preinjector with 750 keV, instead of the previous one with 500 keV. Linac 2 was put into service in 1980. The old Linac 1 was then used for the study of, and later operation with, various types of ions. This picture shows Linac 2 drift-tubes, suspended on stems coming from the top, in contrast to Linac 1, where the drift-tubes stood on stems coming from the bottom.

  19. The CLAS drift chamber system

    CERN Document Server

    Mestayer, M D; Asavapibhop, B; Barbosa, F J; Bonneau, P; Christo, S B; Dodge, G E; Dooling, T; Duncan, W S; Dytman, S A; Feuerbach, R; Gilfoyle, G P; Gyurjyan, V; Hicks, K H; Hicks, R S; Hyde-Wright, C E; Jacobs, G; Klein, A; Klein, F J; Kossov, M; Kuhn, S E; Magahiz, R A; Major, R W; Martin, C; McGuckin, T; McNabb, J; Miskimen, R A; Müller, J A; Niczyporuk, B B; O'Meara, J E; Qin, L M; Raue, B A; Robb, J; Roudot, F; Schumacher, R A; Tedeschi, D J; Thompson, R A; Tilles, D; Tuzel, W; Vansyoc, K; Vineyard, M F; Weinstein, L B; Wilkin, G R; Yegneswaran, A; Yun, J

    2000-01-01

    Experimental Hall B at Jefferson Laboratory houses the CEBAF Large Acceptance Spectrometer, the magnetic field of which is produced by a superconducting toroid. The six coils of this toroid divide the detector azimuthally into six sectors, each of which contains three large multi-layer drift chambers for tracking charged particles produced from a fixed target on the toroidal axis. Within the 18 drift chambers are a total of 35,148 individually instrumented hexagonal drift cells. The novel geometry of these chambers provides for good tracking resolution and efficiency, along with large acceptance. The design and construction challenges posed by these large-scale detectors are described, and detailed results are presented from in-beam measurements.

  20. The ALICE pixel detector upgrade

    Science.gov (United States)

    Reidt, F.

    2016-12-01

    The ALICE experiment at the CERN LHC is designed to study the physics of strongly interacting matter, and in particular the properties of the Quark-Gluon Plasma, using proton-proton, proton-nucleus and nucleus-nucleus collisions. The ALICE collaboration is preparing a major upgrade of the experimental apparatus to be installed during the second long LHC shutdown in the years 2019-2020. A key element of the ALICE upgrade is the new, ultra-light, high-resolution Inner Tracking System. With respect to the current detector, the new Inner Tracking System will significantly enhance the pointing resolution, the tracking efficiency at low transverse momenta, and the read-out rate capabilities. This will be obtained by seven concentric detector layers based on a Monolithic Active Pixel Sensor with a pixel pitch of about 30×30 μm2. A key feature of the new Inner Tracking System, which is optimised for high tracking accuracy at low transverse momenta, is the very low mass of the three innermost layers, which feature a material budget of 0.3% X0 per layer. This contribution presents the design goals and layout of the upgraded ALICE Inner Tracking System, summarises the R&D activities focussing on the technical implementation of the main detector components, and the projected detector performance.

  1. Serial powering of pixel modules

    CERN Document Server

    Stockmanns, Tobias; Hügging, Fabian Georg; Peric, I; Runólfsson, O; Wermes, Norbert

    2003-01-01

    Modern pixel detectors for the next generation of high-energy collider experiments like LHC use readout electronics in deep sub- micron technology. Chips in this technology need a low supply voltage of 2-2.5 V alongside high current consumption to achieve the desired performance. The high supply current leads to significant voltage drops in the long and low mass supply cables so that voltage fluctuations at the chips are induced, when the supply current changes. This problem scales with the number of modules when connected in parallel to the power supplies. An alternative powering scheme connects several modules in series resulting in a higher supply voltage but a lower current consumption of the chain and therefore a much lower voltage drop in the cables. In addition the amount of cables needed to supply the detector is vastly reduced. The concept and features of serial powering are presented and studies of the implementation of this technology as an alternative for the ATLAS pixel detector are shown. In par...

  2. Progress in the Development of CdTe and CdZnTe Semiconductor Radiation Detectors for Astrophysical and Medical Applications

    Directory of Open Access Journals (Sweden)

    Anna Maria Mancini

    2009-05-01

    Full Text Available Over the last decade, cadmium telluride (CdTe and cadmium zinc telluride (CdZnTe wide band gap semiconductors have attracted increasing interest as X-ray and gamma ray detectors. Among the traditional high performance spectrometers based on silicon (Si and germanium (Ge, CdTe and CdZnTe detectors show high detection efficiency and good room temperature performance and are well suited for the development of compact and reliable detection systems. In this paper, we review the current status of research in the development of CdTe and CdZnTe detectors by a comprehensive survey on the material properties, the device characteristics, the different techniques for improving the overall detector performance and some major applications. Astrophysical and medical applications are discussed, pointing out the ongoing Italian research activities on the development of these detectors.

  3. Progress in the Development of CdTe and CdZnTe Semiconductor Radiation Detectors for Astrophysical and Medical Applications.

    Science.gov (United States)

    Sordo, Stefano Del; Abbene, Leonardo; Caroli, Ezio; Mancini, Anna Maria; Zappettini, Andrea; Ubertini, Pietro

    2009-01-01

    Over the last decade, cadmium telluride (CdTe) and cadmium zinc telluride (CdZnTe) wide band gap semiconductors have attracted increasing interest as X-ray and gamma ray detectors. Among the traditional high performance spectrometers based on silicon (Si) and germanium (Ge), CdTe and CdZnTe detectors show high detection efficiency and good room temperature performance and are well suited for the development of compact and reliable detection systems. In this paper, we review the current status of research in the development of CdTe and CdZnTe detectors by a comprehensive survey on the material properties, the device characteristics, the different techniques for improving the overall detector performance and some major applications. Astrophysical and medical applications are discussed, pointing out the ongoing Italian research activities on the development of these detectors.

  4. Point Defects in Pb-, Bi-, and In-Doped CdZnTe Detectors: Deep-Level Transient Spectroscopy (DLTS) Measurements

    Science.gov (United States)

    Gul, R.; Keeter, K.; Rodriguez, R.; Bolotnikov, A. E.; Hossain, A.; Camarda, G. S.; Kim, K. H.; Yang, G.; Cui, Y.; Carcelen, V.; Franc, J.; Li, Z.; James, R. B.

    2012-03-01

    We studied, by current deep-level transient spectroscopy (I-DLTS), point defects induced in CdZnTe detectors by three dopants: Pb, Bi, and In. Pb-doped CdZnTe detectors have a new acceptor trap at around 0.48 eV. The absence of a VCd trap suggests that all Cd vacancies are compensated by Pb interstitials after they form a deep-acceptor complex [[PbCd]+-V{Cd/2-}]-. Bi-doped CdZnTe detectors had two distinct traps: a shallow trap at around 36 meV and a deep donor trap at around 0.82 eV. In detectors doped with In, we noted three well-known traps: two acceptor levels at around 0.18 eV (A-centers) and 0.31 eV (VCd), and a deep trap at around 1.1 eV.

  5. Proceedings of PIXEL98 -- International pixel detector workshop

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, D.F.; Kwan, S. [eds.

    1998-08-01

    Experiments around the globe face new challenges of more precision in the face of higher interaction rates, greater track densities, and higher radiation doses, as they look for rarer and rarer processes, leading many to incorporate pixelated solid-state detectors into their plans. The highest-readout rate devices require new technologies for implementation. This workshop reviewed recent, significant progress in meeting these technical challenges. Participants presented many new results; many of them from the weeks--even days--just before the workshop. Brand new at this workshop were results on cryogenic operation of radiation-damaged silicon detectors (dubbed the Lazarus effect). Other new work included a diamond sensor with 280-micron collection distance; new results on breakdown in p-type silicon detectors; testing of the latest versions of read-out chip and interconnection designs; and the radiation hardness of deep-submicron processes.

  6. Pixel area variations in sensors: a novel framework for predicting pixel fidelity and distortion in flat field response

    CERN Document Server

    Rasmussen, Andrew

    2014-01-01

    We describe the drift field in thick depleted silicon sensors as a superposition of a one-dimensional backdrop field and various three-dimensional perturbative contributions that are physically motivated. We compute trajectories for the conversions along the field lines toward the channel and into volumes where conversions are confined by the perturbative fields. We validate this approach by comparing predictions against measured response distributions seen in five types of fixed pattern distortion features. We derive a quantitative connection between "tree ring" flat field distortions to astrometric and shape transfer errors with connections to measurable wavelength dependence - as ancillary pixel data that may be used in pipeline analysis for catalog population. Such corrections may be tested on DECam data, where correlations between tree ring flat field distortions and astrometric errors - together with their band dependence - are already under study. Dynamic effects, including the brighter-fatter phenomen...

  7. Serial Pixel Analog-to-Digital Converter

    Energy Technology Data Exchange (ETDEWEB)

    Larson, E D

    2010-02-01

    This method reduces the data path from the counter to the pixel register of the analog-to-digital converter (ADC) from as many as 10 bits to a single bit. The reduction in data path width is accomplished by using a coded serial data stream similar to a pseudo random number (PRN) generator. The resulting encoded pixel data is then decoded into a standard hexadecimal format before storage. The high-speed serial pixel ADC concept is based on the single-slope integrating pixel ADC architecture. Previous work has described a massively parallel pixel readout of a similar architecture. The serial ADC connection is similar to the state-of-the art method with the exception that the pixel ADC register is a shift register and the data path is a single bit. A state-of-the-art individual-pixel ADC uses a single-slope charge integration converter architecture with integral registers and “one-hot” counters. This implies that parallel data bits are routed among the counter and the individual on-chip pixel ADC registers. The data path bit-width to the pixel is therefore equivalent to the pixel ADC bit resolution.

  8. Charge collection characteristics of Frisch collar CdZnTe gamma-ray spectrometers

    Energy Technology Data Exchange (ETDEWEB)

    Harrison, Mark J. [Kansas State University, Manhattan, KS 66506 (United States)], E-mail: harrison@ksu.edu; Kargar, Alireza; McGregor, Douglas S. [Kansas State University, Manhattan, KS 66506 (United States)

    2007-08-21

    A collimated {sup 198}Au source was used to determine the charge collection efficiency (CCE) at several locations along the length of a 3.4x3.4x5.5 mm{sup 3} CdZnTe bar detector, both in planar configuration and with Frisch collars of varying length. For each configuration, a 0.50-mm-long region spanning the width of the device was irradiated with 411-keV gamma rays produced by a neutron-activated gold foil. Irradiation began at the cathode and stepped in 0.50-mm steps toward the anode, with a spectrum being collected at each location. By observing the channel location of the full-energy peak in each collected spectrum, an average CCE was determined for each irradiated region. The CCE was found to vary nearly linearly along the length of the device in the planar configuration, starting at a peak value of 89% and dropping to a minimum measured value of 26% near the anode. The addition of a Frisch collar covering the entire length of the crystal greatly altered the CCE profile, which remained near 87% for approximately two-thirds of the length, then sharply dropped near the anode. Results were confirmed by theoretical models. Further CCE mapping was also completed for devices with Frisch collars of various lengths. Those results are reported as well.

  9. Development of CdZnTe X-ray detectors at DSRI

    DEFF Research Database (Denmark)

    van Pamelen, M.A.J.; Budtz-Jørgensen, Carl; Kuvvetli, Irfan

    2000-01-01

    An overview of the development of CdZnTe X-ray detectors at the Danish Space Research Institute is presented. Initiated in the beginning of 1996, the main motivation at that time was to develop focal plane detectors for the novel type of hard X-ray telescopes, which are currently under study at D...... trapping has now little influence and the spectrum displays a pronounced Gaussian peak at 661 keV with a width (FWHM) of 6.9 keV. Also a small peak produced by CdTe escape events can now be observed. At the same time, no events have to be rejected....... at DSRI. With the advent of the Danish Micro Satellite program it was, however, recognised that this type of detector is very well suited for two proposed missions (eXCALIBur, AXO). The research at DSRI has so far been concentrated on the spectroscopic properties of the CZT detector. At DSRI we have...

  10. Optimization of control parameters of CdZnTe ACRT-Bridgman single crystal growth

    Institute of Scientific and Technical Information of China (English)

    LIU Juncheng

    2004-01-01

    The CdZnTe vertical Bridgman single crystal process with accelerated crucible rotation technique (ACRT) has been simulated. Effects have been investigated of the ACRT wave parameters on the solid-liquid interface concavity and the solute segregation of the crystal. The results show that ACRT can result in the increase of both the solid-liquid interface concavity and the temperature gradient of the melt in the front of the solid-liquid interface, of which the magnitude varies from small to many times when the ACRT wave parameters change. Of the ACRT wave parameters, the increase of the crucible maximum rotation rate can hardly improve the radial solute segregation of the crystal, but the variation of the crucible acceleration time, the keep time at the maximum rotation rate, and the crucible deceleration time can affect the solute segregation of the single crystal extraordinarily. With suitable wave parameters, ACRT greatly decreases the radial solute segregation of the crystal, and even makes it disappear completely. However, it increases both the axial solute segregation and the radial one notably with bad wave parameters. An excellent single crystal could be gotten, of which a majority part is with no segregation, with ACRT-Bridgman method by adjusting both the ACRT wave parameters and the crystal growth control parameters, such as the initial temperature of the melt, the temperature gradient, and the crucible withdrawal rate, etc.

  11. Growth and characterization of CdTe and CdZnTe crystals for substrate application

    Science.gov (United States)

    Azoulay, Moshe; Zilber, Raphael; Shusterman, Sergy; Goldgirsh, Alex; Zontag, Itzhak

    2003-01-01

    During the last decade we have investigated the synthesis, growth and characterization of CdTe and CdZnTe semiconductor compounds. As a result, substrate crystals, suitable for mercury cadmium telluride thin film growth are prepared. The emphasis will be given to the investigation of the thermal regime during growth, reflected at the solid liquid interface shape and its influence on the crystalline quality. Seeded and unseeded growth experiments are compared in terms of structural crystalline quality. Seeded and unseeded growth experiments are compared in terms of structural crystalline perfection as well as single crystal yield. The effect of thermal annealing on IR transmittance, precipitates and inclusions will be discussed in detail. Moreover, we will show the recent new trends for simulation of crystal growth processes by CRYSVUN software as well as practical implementation of calculated data for the grwoth of II-VI crystals. Preliminary study on the vapor phase control during growth and crystal cooling procedures will also be discussed.

  12. MTF Issues in Small-Pixel-Pitch Planar Quantum IR Detectors

    Science.gov (United States)

    Gravrand, O.; Baier, N.; Ferron, A.; Rochette, F.; Berthoz, J.; Rubaldo, L.; Cluzel, R.

    2014-08-01

    The current trend in quantum infrared (IR) detector development is the design of very small-pixel-pitch large arrays. From the previous 30 μm pitch, the standard pixel pitch today is 15 μm and is expected to decrease to 12 μm in the next few years. Furthermore, focal-plane arrays (FPAs) with pixel pitch as small as 10 μm have been demonstrated. Such ultrasmall-pixel pitches are very small compared with the typical length ruling the electrical characteristics of the absorbing materials, namely the minority-carrier diffusion length. As an example, for low-doped n-type HgCdTe or InSb material, this diffusion length is on the order of 30 μm to 50 μm, i.e., three to five times the targeted pixel pitches. This has strong consequences for the modulation transfer function (MTF) of planar structures, where the lateral extension of the photodiode is limited by diffusion. For such aspect ratios, the self-confinement of neighboring diodes may not be efficient enough to maintain an optimal MTF. Therefore, this issue has to be addressed to take full advantage of the pixel pitch reduction in terms of image resolution. The aim of this work is to investigate the evolution of the MTF of HgCdTe and InSb FPAs when decreasing the pixel pitch below 15 μm. Both experimental measurements and finite-element simulations are used to discuss this issue. Different scenarios are compared, namely deep mesa etch between pixels, internal drift, surface recombination, and thin absorbing layers.

  13. Does the geoid drift west?

    Science.gov (United States)

    Backus, G. E.; Parker, R. L.; Zumberge, M. A.

    1985-01-01

    In 1970 Hide and Malin noted a correlation of about 0.8 between the geoid and the geomagnetic potential at the Earth's surface when the latter is rotated eastward in longitude by about 160 degrees and the spherical harmonic expansions of both functions are truncated at degree 4. From a century of magnetic observatory data, Hide and Malin inferred an average magnetic westward drift rate of about 0.27 degrees/year. They attributed the magnetic-gravitational correlation to a core event at about 1350 A.D. which impressed the mantle's gravity pattern at long wavelengths onto the core motion and the resulting magnetic field. The impressed pattern was then carried westward 160 degrees by the nsuing magnetic westward drift. An alternative possibility is some sort of steady physical coupling between the magnetic and gravitational fields (perhaps migration of Hide's bumps on the core-mantle interface). This model predicts that the geoid will drift west at the magnetic rate. On a rigid earth, the resulting changes in sea level would be easily observed, but they could be masked by adjustment of the mantle if it has a shell with viscosity considerably less than 10 to the 21 poise. However, steady westward drift of the geoid also predicts secular changes in g, the local acceleration of gravity, at land stations. These changes are now ruled out by recent independent high-accuracy absolute measurements of g made by several workers at various locations in the Northern Hemisphere.

  14. ATLAS Pixel Opto-Electronics

    CERN Document Server

    Arms, K E; Gan, K K; Holder, M; Jackson, P; Johnson, M; Kagan, H; Kass, R; Rahimi, A M; Roggenbuck, A; Rush, C; Schade, P; Smith, S; Ter-Antonian, R; Ziolkowski, M; Zoeller, M M

    2005-01-01

    We have developed two radiation-hard ASICs for optical data transmission in the ATLAS pixel detector at the LHC at CERN: a driver chip for a Vertical Cavity Surface Emitting Laser (VCSEL) diode for 80 Mbit/s data transmission from the detector, and a Bi-Phase Mark decoder chip to recover the control data and 40 MHz clock received optically by a PIN diode. We have successfully implemented both ASICs in 0.25 micron CMOS technology using enclosed layout transistors and guard rings for increased radiation hardness. We present results of the performance of these chips, including irradiation with 24 GeV protons up to 61 Mrad (2.3 x 10e15 p/cm^2).

  15. Pixel readout chip for the ATLAS experiment

    CERN Document Server

    Ackers, M; Blanquart, L; Bonzom, V; Comes, G; Fischer, P; Keil, M; Kühl, T; Meuser, S; Delpierre, P A; Treis, J; Raith, B A; Wermes, N

    1999-01-01

    Pixel detectors with a high granularity and a very large number of sensitive elements (cells) are a very recent development used for high precision particle detection. At the Large Hadron Collider LHC at CERN (Geneva) a pixel detector with 1.4*10/sup 8/ individual pixel cells is developed for the ATLAS detector. The concept is a hybrid detector. Consisting of a pixel sensor connected to a pixel electronics chip by bump and flip chip technology in one-to-one cell correspondence. The development and prototype results of the pixel front end chip are presented together with the physical and technical requirements to be met at LHC. Lab measurements are reported. (6 refs).

  16. Penrose Pixels for Super-Resolution.

    Science.gov (United States)

    Ben-Ezra, M; Lin, Zhouchen; Wilburn, Bennett; Zhang, Wei

    2011-07-01

    We present a novel approach to reconstruction-based super-resolution that uses aperiodic pixel tilings, such as a Penrose tiling or a biological retina, for improved performance. To this aim, we develop a new variant of the well-known error back projection super-resolution algorithm that makes use of the exact detector model in its back projection operator for better accuracy. Pixels in our model can vary in shape and size, and there may be gaps between adjacent pixels. The algorithm applies equally well to periodic or aperiodic pixel tilings. We present analysis and extensive tests using synthetic and real images to show that our approach using aperiodic layouts substantially outperforms existing reconstruction-based algorithms for regular pixel arrays. We close with a discussion of the feasibility of manufacturing CMOS or CCD chips with pixels arranged in Penrose tilings.

  17. Advanced pixel architectures for scientific image sensors

    CERN Document Server

    Coath, R; Godbeer, A; Wilson, M; Turchetta, R

    2009-01-01

    We present recent developments from two projects targeting advanced pixel architectures for scientific applications. Results are reported from FORTIS, a sensor demonstrating variants on a 4T pixel architecture. The variants include differences in pixel and diode size, the in-pixel source follower transistor size and the capacitance of the readout node to optimise for low noise and sensitivity to small amounts of charge. Results are also reported from TPAC, a complex pixel architecture with ~160 transistors per pixel. Both sensors were manufactured in the 0.18μm INMAPS process, which includes a special deep p-well layer and fabrication on a high resistivity epitaxial layer for improved charge collection efficiency.

  18. Dead pixel replacement in LWIR microgrid polarimeters.

    Science.gov (United States)

    Ratliff, Bradley M; Tyo, J Scott; Boger, James K; Black, Wiley T; Bowers, David L; Fetrow, Matthew P

    2007-06-11

    LWIR imaging arrays are often affected by nonresponsive pixels, or "dead pixels." These dead pixels can severely degrade the quality of imagery and often have to be replaced before subsequent image processing and display of the imagery data. For LWIR arrays that are integrated with arrays of micropolarizers, the problem of dead pixels is amplified. Conventional dead pixel replacement (DPR) strategies cannot be employed since neighboring pixels are of different polarizations. In this paper we present two DPR schemes. The first is a modified nearest-neighbor replacement method. The second is a method based on redundancy in the polarization measurements.We find that the redundancy-based DPR scheme provides an order-of-magnitude better performance for typical LWIR polarimetric data.

  19. CdZnTe detector for computed tomography based on weighting potential

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Hyun Jong; Park, Chan Sun; Kim, Jung Su; Kim, Jung Min; Choi, Jong Hak; Kim, Ki Hyun [Korea University, Seoul (Korea, Republic of)

    2016-03-15

    Room-temperature operating CdZnTe(CZT) material is an innovative radiation detector which could reduce the patient dose to one-tenth level of conventional CT (Computed Tomography) and mammography system. The pixel and pixel pitch in the imaging device determine the conversion efficiency of incident Xor gamma-ray and the cross-talk of signal, that is, image quality of detector system. The weighting potential is the virtual potential determined by the position and geometry of electrode. The weighting potential obtained by computer-based simulation in solving Poisson equation with proper boundaries condition. The pixel was optimized by considering the CIE (charge induced efficiency) and the signal cross-talk in CT detector system. The pixel pitch was 1-mm and the detector thickness was 2-mm in the simulation. The optimized pixel size and inter-pixel distance for maximizing the CIE and minimizing the signal cross-talk is about 750 μm and 125 μm, respectively.

  20. Operational Experience with the ATLAS Pixel Detector

    CERN Document Server

    Lantzsch, Kerstin; The ATLAS collaboration

    2016-01-01

    Run 2 of the LHC is providing new challenges to track and vertex reconstruction with higher energies, denser jets and higher rates. Therefore the ATLAS experiment has constructed the first 4-layer Pixel detector in HEP, installing a new Pixel layer, also called Insertable B-Layer (IBL). In addition the Pixel detector was refurbished with new service quarter panels to recover about 3% of defective modules lost during run 1 and a new optical readout system to readout the data at higher speed while reducing the occupancy when running with increased luminosity. The commissioning, operation and performance of the 4-layer Pixel Detector will be presented.

  1. Implementation of TDI based digital pixel ROIC with 15μm pixel pitch

    Science.gov (United States)

    Ceylan, Omer; Shafique, Atia; Burak, A.; Caliskan, Can; Abbasi, Shahbaz; Yazici, Melik; Gurbuz, Yasar

    2016-05-01

    A 15um pixel pitch digital pixel for LWIR time delay integration (TDI) applications is implemented which occupies one fourth of pixel area compared to previous digital TDI implementation. TDI is implemented on 8 pixels with oversampling rate of 2. ROIC provides 16 bits output with 8 bits of MSB and 8 bits of LSB. Pixel can store 75 M electrons with a quantization noise of 500 electrons. Digital pixel TDI implementation is advantageous over analog counterparts considering power consumption, chip area and signal-to-noise ratio. Digital pixel TDI ROIC is fabricated with 0.18um CMOS process. In digital pixel TDI implementation photocurrent is integrated on a capacitor in pixel and converted to digital data in pixel. This digital data triggers the summation counters which implements TDI addition. After all pixels in a row contribute, the summed data is divided to the number of TDI pixels(N) to have the actual output which is square root of N improved version of a single pixel output in terms of signal-to-noise-ratio (SNR).

  2. Hg1-xCdxTe vapor deposition on CdZnTe substrates by Closed Space Sublimation technique

    Science.gov (United States)

    Rubio, Sandra; Sochinskii, Nikolai V.; Repiso, Eva; Tsybrii, Zinoviia; Sizov, Fiodor; Plaza, Jose Luis; Diéguez, Ernesto

    2017-01-01

    Closed Space Sublimation (CSS) technique has been studied to deposit Hg1-xCdxTe polycrystalline films on CdZnTe substrates at the improved pressure-temperature conditions. The experimental results on film characterization suggest that the CSS optimal conditions are the argon atmospheric pressure (1013 mbar) and the deposition temperature in the range of 500-550 °C. These conditions provide macro-defect free Hg1-xCdxTe films with the uniform size and surface distribution of polycrystals.

  3. Influence of the thickness of a crystal on the electrical characteristics of Cd(Zn)Te detectors

    Energy Technology Data Exchange (ETDEWEB)

    Sklyarchuk, V. [Chernivtsi National Univ. (Ukraine); Fochuk, p. [Chernivtsi National Univ. (Ukraine); Rarenko, I. [Chernivtsi National Univ. (Ukraine); Zakharuk, Z. [Chernivtsi National Univ. (Ukraine); Sklyarchuk, O. F. [Chernivtsi National Univ. (Ukraine); Bolotnikov, A. E. [Brookhaven National Lab. (BNL), Upton, NY (United States); James, R. B. [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2015-08-01

    We studied the electrical characteristics of Cd(Zn)Te detectors with rectifying contacts and varying thicknesses, and established that their geometrical dimensions affect the measured electrical properties. We found that the maximum value of the operating-bias voltage and the electric field in the detector for acceptable values of the dark current can be achieved when the crystal has an optimum thickness. This finding is due to the combined effect of generation-recombination in the space-charge region and space-charge limited currents (SCLC).

  4. Dispersal of invasive species by drifting

    NARCIS (Netherlands)

    Riel, van M.C.; Velde, van der G.; Vaate, bij de A.

    2011-01-01

    Drifting can be an effective way for aquatic organisms to disperse and colonise new areas. Increasing connectivity between European large rivers facilitates invasion by drifting aquatic macroinvertebrates. The present study shows that high abundances of invasive species drift in the headstream of

  5. Drift Chambers detectors; Detectores de deriva

    Energy Technology Data Exchange (ETDEWEB)

    Duran, I.; Martinez laso, L.

    1989-07-01

    We present here a review of High Energy Physics detectors based on drift chambers. The ionization, drift diffusion, multiplication and detection principles are described. Most common drift media are analysed, and a classification of the detectors according to its geometry is done. Finally the standard read-out methods are displayed and the limits of the spatial resolution are discussed. (Author) 115 refs.

  6. Reading a GEM with a VLSI pixel ASIC used as a direct charge collecting anode

    CERN Document Server

    Bellazzini, R; Baldini, L; Bitti, F; Brez, A; Latronico, L; Massai, M M; Minuti, M; Omodei, N; Razzano, M; Sgro, C; Spandre, G; Costa, E; Soffitta, P

    2004-01-01

    In MicroPattern Gas Detectors (MPGD) when the pixel size is below 100 micron and the number of pixels is large (above 1000) it is virtually impossible to use the conventional PCB read-out approach to bring the signal charge from the individual pixel to the external electronics chain. For this reason a custom CMOS array of 2101 active pixels with 80 micron pitch, directly used as the charge collecting anode of a GEM amplifying structure, has been developed and built. Each charge collecting pad, hexagonally shaped, realized using the top metal layer of a deep submicron VLSI technology is individually connected to a full electronics chain (pre-amplifier, shaping-amplifier, sample and hold, multiplexer) which is built immediately below it by using the remaining five active layers. The GEM and the drift electrode window are assembled directly over the chip so the ASIC itself becomes the pixelized anode of a MicroPattern Gas Detector. With this approach, for the first time, gas detectors have reached the level of i...

  7. A Low-Noise CMOS Pixel Direct Charge Sensor, Topmetal-II-

    CERN Document Server

    An, Mangmang; Gao, Chaosong; Han, Mikyung; Ji, Rong; Li, Xiaoting; Mei, Yuan; Sun, Quan; Sun, Xiangming; Wang, Kai; Xiao, Le; Xu, Nu; Yang, Ping; Zhou, Wei

    2016-01-01

    We report the design and characterization of a CMOS pixel direct charge sensor, Topmetal-II-, fabricated in a standard 0.35um CMOS Integrated Circuit process. The sensor utilizes exposed metal patches on top of each pixel to directly collect charge. Each pixel contains a low-noise charge-sensitive preamplifier to establish the analog signal and a discriminator with tunable threshold to generate hits. The analog signal from each pixel is accessible through time-shared multiplexing over the entire array. Hits are read out digitally through a column-based priority logic structure. Tests show that the sensor achieved a <15e- analog noise and a 200e- minimum threshold for digital readout per pixel. The sensor is capable of detecting both electrons and ions drifting in gas. These characteristics enable its use as the charge readout device in future Time Projection Chambers without gaseous gain mechanism, which has unique advantages in low background and low rate-density experiments.

  8. A low-noise CMOS pixel direct charge sensor, Topmetal-II-

    Science.gov (United States)

    An, Mangmang; Chen, Chufeng; Gao, Chaosong; Han, Mikyung; Ji, Rong; Li, Xiaoting; Mei, Yuan; Sun, Quan; Sun, Xiangming; Wang, Kai; Xiao, Le; Yang, Ping; Zhou, Wei

    2016-02-01

    We report the design and characterization of a CMOS pixel direct charge sensor, Topmetal-II-, fabricated in a standard 0.35 μm CMOS Integrated Circuit process. The sensor utilizes exposed metal patches on top of each pixel to directly collect charge. Each pixel contains a low-noise charge-sensitive preamplifier to establish the analog signal and a discriminator with tunable threshold to generate hits. The analog signal from each pixel is accessible through time-shared multiplexing over the entire array. Hits are read out digitally through a column-based priority logic structure. Tests show that the sensor achieved a analog noise and a 200e- minimum threshold for digital readout per pixel. The sensor is capable of detecting both electrons and ions drifting in gas. These characteristics enable its use as the charge readout device in future Time Projection Chambers without gaseous gain mechanism, which has unique advantages in low background and low rate-density experiments.

  9. DMAPS: a fully depleted monolithic active pixel sensor—analog performance characterization

    Science.gov (United States)

    Havránek, M.; Hemperek, T.; Krüger, H.; Fu, Y.; Germic, L.; Kishishita, T.; Marinas, C.; Obermann, T.; Wermes, N.

    2015-02-01

    Monolithic Active Pixel Sensors (MAPS) have been developed since the late 1990s based on silicon substrates with a thin epitaxial layer (thickness of 10-15 μm) in which charge is collected on an electrode, albeit by disordered and slow diffusion rather than by drift in a directed electric field. As a consequence, the signal of these conventional MAPS is small (≈1000 e-) and the radiation tolerance is limited. In this paper, the development of a fully Depleted Monolithic Active Pixel Sensors (DMAPS) based on a high resistivity substrate allowing the creation of a fully depleted detection volume is presented. This concept overcomes the inherent limitations of charge collection by diffusion in the standard MAPS designs. We present results from a prototype chip EPCB01 designed in a commercial 150 nm CMOS technology. The technology provides a thin (≈50 μm) high resistivity n-type silicon substrate as well as an additional deep p-well which allows to integrate full CMOS circuitry inside the pixel. Different matrix types with several variants of collection electrodes and pixel electronics have been implemented. Measurements of the analog performance of this first implementation of DMAPS pixels are presented.

  10. Absolute Position Measurement in a Gas Time Projection Chamber via Transverse Diffusion of Drift Charge

    CERN Document Server

    Lewis, P M; Hedges, M T; Jaegle, I; Seong, I S; Thorpe, T N

    2014-01-01

    Time Projection Chambers (TPCs) with charge readout via micro pattern gaseous detectors can provide detailed measurements of charge density distributions. We here report on measurements of alpha particle tracks, using a TPC where the drift charge is amplified with Gas Electron Multipliers and detected with a pixel ASIC. We find that by measuring the 3-D topology of drift charge and fitting for its transverse diffusion, we obtain the absolute position of tracks in the drift direction. For example, we obtain a precision of 1~cm for 1~cm-long alpha track segments. To our knowledge this is the first demonstration of such a measurement in a gas TPC. This technique has several attractive features: it does not require knowledge of the initial specific ionization, is robust against bias from diffuse charge below detection threshold, and is also robust against high charge densities that saturate the detector response.

  11. Nonlinear evolution of drift instabilities

    Energy Technology Data Exchange (ETDEWEB)

    Lee, W.W.; Krommes, J.A.; Oberman, C.R.; Smith, R.A.

    1984-01-01

    The nonlinear evolution of collisionless drift instabilities in a shear-free magnetic field has been studied by means of gyrokinetic particle simulation as well as numerical integration of model mode-coupling equations. The purpose of the investigation is to identify relevant nonlinear mechanisms responsible for the steady-state drift wave fluctuations. It is found that the saturation of the instability is mainly caused by the nonlinear E x B convection of the resonant electrons and their associated velocity space nonlinearity. The latter also induces energy exchange between the competing modes, which, in turn, gives rise to enhanced diffusion. The nonlinear E x B convection of the ions, which contributes to the nonlinear frequency shift, is also an important ingredient for the saturation.

  12. A Pascalian lateral drift sensor

    Energy Technology Data Exchange (ETDEWEB)

    Jansen, H., E-mail: hendrik.jansen@desy.de

    2016-09-21

    A novel concept of a layer-wise produced semiconductor sensor for precise particle tracking is proposed herein. In contrast to common semiconductor sensors, local regions with increased doping concentration deep in the bulk termed charge guides increase the lateral drift of free charges on their way to the read-out electrode. This lateral drift enables charge sharing independent of the incident position of the traversing particle. With a regular grid of charge guides the lateral charge distribution resembles a normalised Pascal's triangle for particles that are stopped in depths lower than the depth of the first layer of the charge guides. For minimum ionising particles a sum of binomial distributions describes the lateral charge distribution. This concept decouples the achievable sensor resolution from the pitch size as the characteristic length is replaced by the lateral distance of the charge guides.

  13. A Pascalian lateral drift sensor

    Science.gov (United States)

    Jansen, H.

    2016-09-01

    A novel concept of a layer-wise produced semiconductor sensor for precise particle tracking is proposed herein. In contrast to common semiconductor sensors, local regions with increased doping concentration deep in the bulk termed charge guides increase the lateral drift of free charges on their way to the read-out electrode. This lateral drift enables charge sharing independent of the incident position of the traversing particle. With a regular grid of charge guides the lateral charge distribution resembles a normalised Pascal's triangle for particles that are stopped in depths lower than the depth of the first layer of the charge guides. For minimum ionising particles a sum of binomial distributions describes the lateral charge distribution. This concept decouples the achievable sensor resolution from the pitch size as the characteristic length is replaced by the lateral distance of the charge guides.

  14. Land Cover Heterogeneity Effects on Sub-Pixel and Per-Pixel Classifications

    Directory of Open Access Journals (Sweden)

    Trung V. Tran

    2014-04-01

    Full Text Available Per-pixel and sub-pixel are two common classification methods in land cover studies. The characteristics of a landscape, particularly the land cover itself, can affect the accuracies of both methods. The objectives of this study were to: (1 compare the performance of sub-pixel vs. per-pixel classification methods for a broad heterogeneous region; and (2 analyze the impact of land cover heterogeneity (i.e., the number of land cover classes per pixel on both classification methods. The results demonstrated that the accuracy of both per-pixel and sub-pixel classification methods were generally reduced by increasing land cover heterogeneity. Urban areas, for example, were found to have the lowest accuracy for the per-pixel method, because they had the highest heterogeneity. Conversely, rural areas dominated by cropland and grassland had low heterogeneity and high accuracy. When a sub-pixel method was used, the producer’s accuracy for artificial surfaces was increased by more than 20%. For all other land cover classes, sub-pixel and per-pixel classification methods performed similarly. Thus, the sub-pixel classification was only advantageous for heterogeneous urban landscapes. Both creators and users of land cover datasets should be aware of the inherent landscape heterogeneity and its potential effect on map accuracy.

  15. MPS II drift chamber system

    Energy Technology Data Exchange (ETDEWEB)

    Platner, E.D.

    1982-01-01

    The MPS II detectors are narrow drift space chambers designed for high position resolution in a magnetic field and in a very high particle flux environment. Central to this implementation was the development of 3 multi-channel custom IC's and one multi-channel hybrid. The system is deadtimeless and requires no corrections on an anode-to-anode basis. Operational experience and relevance to ISABELLE detectors is discussed.

  16. ISPA (imaging silicon pixel array) experiment

    CERN Multimedia

    Patrice Loïez

    2002-01-01

    The bump-bonded silicon pixel detector, developed at CERN by the EP-MIC group, is shown here in its ceramic carrier. Both represent the ISPA-tube anode. The chip features between 1024 (called OMEGA-1) and 8196 (ALICE-1) active pixels.

  17. Shear wall ultimate drift limits

    Energy Technology Data Exchange (ETDEWEB)

    Duffey, T.A. [Duffy, (T.A.) Tijeras, NM (United States); Goldman, A. [Goldman, (A.), Sandia, Los Alamos, NM (United States); Farrar, C.R. [Los Alamos National Lab., NM (United States)

    1994-04-01

    Drift limits for reinforced-concrete shear walls are investigated by reviewing the open literature for appropriate experimental data. Drift values at ultimate are determined for walls with aspect ratios ranging up to a maximum of 3.53 and undergoing different types of lateral loading (cyclic static, monotonic static, and dynamic). Based on the geometry of actual nuclear power plant structures exclusive of containments and concerns regarding their response during seismic (i.e.,cyclic) loading, data are obtained from pertinent references for which the wall aspect ratio is less than or equal to approximately 1, and for which testing is cyclic in nature (typically displacement controlled). In particular, lateral deflections at ultimate load, and at points in the softening region beyond ultimate for which the load has dropped to 90, 80, 70, 60, and 50 percent of its ultimate value, are obtained and converted to drift information. The statistical nature of the data is also investigated. These data are shown to be lognormally distributed, and an analysis of variance is performed. The use of statistics to estimate Probability of Failure for a shear wall structure is illustrated.

  18. Gamma spectrometric characterization of short cooling time nuclear spent fuels using hemispheric CdZnTe detectors

    CERN Document Server

    Lebrun, A; Szabó, J L; Arenas-Carrasco, J; Arlt, R; Dubreuil, A; Esmailpur-Kazerouni, K

    2000-01-01

    After years of cooling, nuclear spent fuel gamma emissions are mainly due to caesium isotopes which are emitters at 605, 662 and 796-801 keV. Extensive work has been done on such fuels using various CdTe or CdZnTe probes. When fuels have to be measured after short cooling time (during NPP outage) the spectrum is much more complex due to the important contributions of niobium and zirconium in the 700 keV range. For the first time in a nuclear power plant, four spent fuels of the Kozloduy VVER reactor no 4 were measured during outage, 37 days after shutdown of the reactor. In such conditions, good resolution is of particular interest, so a 20 mm sup 3 hemispheric crystal was used with a resolution better than 7 keV at 662 keV. This paper presents the experimental device and analyzes the results which show that CdZnTe commercially available detectors enabled us to perform a semi-quantitative determination of the burn-up after a short cooling time. In addition, it is discussed how a burn-up evolution code (CESAR)...

  19. Discrimination of alpha particles in CdZnTe detectors with coplanar grid for the COBRA experiment

    Energy Technology Data Exchange (ETDEWEB)

    Rebber, Henning [Universitaet Hamburg, Institut fuer Experimentalphysik, Luruper Chaussee 149, 22761 Hamburg (Germany); Collaboration: COBRA-Collaboration

    2016-07-01

    The aim of the COBRA experiment is the search for neutrinoless double beta decay using CdZnTe semiconductor detectors. A background rate in the order of 10{sup -3} counts per keV, kg and year is intended in order to be sensitive to a half-life larger than 10{sup 26} years. Measurements from a demonstrator setup and Monte Carlo simulations indicate that a large background component is due to alpha particles. These generate charge clouds of only few μm in diameter in the detector, leading to characteristic pulse features. Parameter-based cut criteria were developed to discriminate alpha events by means of their pulse shapes. The cuts were tested on data from alpha and beta irradiation of a (1 x 1 x 1) cm{sup 3} CdZnTe detector with coplanar grid. The pulse shapes of all event signals were read out by FADCs with a sampling rate of 100 MHz. The signals were reproduced by a detector simulation which hence was used to study the cuts for energies up to 3 MeV and different detector regions.

  20. CdTe and CdZnTe detectors behavior in X-ray computed tomography conditions

    CERN Document Server

    Ricq, S; Garcin, M

    2000-01-01

    The application of CdTe and CdZnTe 2D array detectors for medical X-ray Computed Tomography (XCT) is investigated. Different metallic electrodes have been deposited on High-Pressure Bridgman Method CdZnTe and on Traveling Heater Method CdTe:Cl. These detectors are exposed to X-rays in the CT irradiation conditions and are characterized experimentally in current mode. Detectors performances such as sensitivity and response speed are studied. They are correlated with charge trapping and de-trapping. The trapped carrier space charges may influence the injection from the electrodes. This enables one to get information on the nature of the predominant levels involved. The performances achieved are encouraging: dynamic ranges higher than 4 decades and current decreases of 3 decades in 4 ms after X-ray beam cut-off are obtained. Nevertheless, these detectors are still limited by high trap densities responsible for the memory effect that makes them unsuitable for XCT.

  1. Electronic properties of traps induced by gamma-irradiation in CdTe and CdZnTe detectors

    CERN Document Server

    Cavallini, A; Chirco, P; Morigi, M P; Zanarini, M; Auricchio, N; Caroli, E; Dusi, W; Fougeres, P; Hage-Ali, M; Siffert, P

    2000-01-01

    The knowledge of a detector response to different types of radiation sources is becoming a key issue for its employment in many medical, space and scientific applications. Nevertheless, a clear understanding of the effects of irradiation on the material properties is still a long way ahead and, therefore, we have started a thorough investigation of room temperature CdTe and CdZnTe detectors exposed to gamma-ray irradiation. As-grown detectors have been exposed to increasing gamma-ray doses, up to the virtual death of the detector, which occurs at a dose of 30 kGy. The modifications in the detector performance have been investigated by dark-current measurements and quantitative spectroscopic analyses at low and medium energies. The deep levels present in the material have been identified by means of Photo-Induced Current Transient Spectroscopy (PICTS) analyses. The evolution of the trap parameters with increasing irradiation dose has been monitored and a comparison of the results obtained from CdTe and CdZnTe ...

  2. Comparison of CdTe and CdZnTe Detectors for Field Determination of Uranium Isotopic Enrichments

    Energy Technology Data Exchange (ETDEWEB)

    Hofstetter, KJ

    2004-01-23

    A performance comparison of a CdTe and a CdZnTe detector when exposed to uranium samples of various isotopic enrichments has been performed. These high-resolution detectors can assist in the rapid determination of uranium isotopic content of illicit material. Spectra were recorded from these room temperature semiconductor detectors with a portable multi-channel analyzer, both in the laboratory and in a field environment. Both detectors were operated below ambient temperature using the vendor supplied thermoelectric coolers. Both detectors had nominally the same active volume (18 mm3 for the CdZnTe and 25 mm3 for the CdTe detector) and resolution. Spectra of samples of known isotopic content were recorded at fixed geometries. An evaluation of potential signature g rays for the detection of enriched uranium was completed. Operational advantages and disadvantages of each detector are discussed. There is a need to improve the detection sensitivity during the interdiction of special nuclear materials (SNM) for increased homeland protection. It is essential to provide additional tools to first responders and law enforcement personnel for assessing nuclear and radiological threats.

  3. Dispersal of invasive species by drifting

    Directory of Open Access Journals (Sweden)

    M.C. VAN RIEL, G. VAN DER VELDE, A. BIJ DE VAATE

    2011-12-01

    Full Text Available Drifting can be an effective way for aquatic organisms to disperse and colonise new areas. Increasing connectivity between European large rivers facilitates invasion by drifting aquatic macroinvertebrates. The present study shows that high abundances of invasive species drift in the headstream of the river Rhine. Dikerogammarus villosus and Chelicorophium curvispinum represented up to 90% of the total of drifting macroinvertebrates. Drift activity shows seasonal and diel patterns. Most species started drifting in spring and were most abundant in the water column during the summer period. Drift activity was very low during the winter period. Diel patterns were apparent; most species, including D. villosus, drifted during the night. Drifting macroinvertebrates colonised stony substrate directly from the water column. D. villosus generally colonised the substrate at night, while higher numbers of C. curvispinum colonised the substrate during the day. It is very likely that drifting functions as a dispersal mechanism for crustacean invaders. Once waterways are connected, these species are no longer necessarily dependent on dispersal vectors other than drift for extending their distribution range [Current Zoology 57 (6: 818–827, 2011].

  4. Sub-pixel mapping of water boundaries using pixel swapping algorithm (case study: Tagliamento River, Italy)

    Science.gov (United States)

    Niroumand-Jadidi, Milad; Vitti, Alfonso

    2015-10-01

    Taking the advantages of remotely sensed data for mapping and monitoring of water boundaries is of particular importance in many different management and conservation activities. Imagery data are classified using automatic techniques to produce maps entering the water bodies' analysis chain in several and different points. Very commonly, medium or coarse spatial resolution imagery is used in studies of large water bodies. Data of this kind is affected by the presence of mixed pixels leading to very outstanding problems, in particular when dealing with boundary pixels. A considerable amount of uncertainty inescapably occurs when conventional hard classifiers (e.g., maximum likelihood) are applied on mixed pixels. In this study, Linear Spectral Mixture Model (LSMM) is used to estimate the proportion of water in boundary pixels. Firstly by applying an unsupervised clustering, the water body is identified approximately and a buffer area considered ensuring the selection of entire boundary pixels. Then LSMM is applied on this buffer region to estimate the fractional maps. However, resultant output of LSMM does not provide a sub-pixel map corresponding to water abundances. To tackle with this problem, Pixel Swapping (PS) algorithm is used to allocate sub-pixels within mixed pixels in such a way to maximize the spatial proximity of sub-pixels and pixels in the neighborhood. The water area of two segments of Tagliamento River (Italy) are mapped in sub-pixel resolution (10m) using a 30m Landsat image. To evaluate the proficiency of the proposed approach for sub-pixel boundary mapping, the image is also classified using a conventional hard classifier. A high resolution image of the same area is also classified and used as a reference for accuracy assessment. According to the results, sub-pixel map shows in average about 8 percent higher overall accuracy than hard classification and fits very well in the boundaries with the reference map.

  5. It's not the pixel count, you fool

    Science.gov (United States)

    Kriss, Michael A.

    2012-01-01

    The first thing a "marketing guy" asks the digital camera engineer is "how many pixels does it have, for we need as many mega pixels as possible since the other guys are killing us with their "umpteen" mega pixel pocket sized digital cameras. And so it goes until the pixels get smaller and smaller in order to inflate the pixel count in the never-ending pixel-wars. These small pixels just are not very good. The truth of the matter is that the most important feature of digital cameras in the last five years is the automatic motion control to stabilize the image on the sensor along with some very sophisticated image processing. All the rest has been hype and some "cool" design. What is the future for digital imaging and what will drive growth of camera sales (not counting the cell phone cameras which totally dominate the market in terms of camera sales) and more importantly after sales profits? Well sit in on the Dark Side of Color and find out what is being done to increase the after sales profits and don't be surprised if has been done long ago in some basement lab of a photographic company and of course, before its time.

  6. Upgrades of the ATLAS Pixel Detector

    CERN Document Server

    Hügging, F; The ATLAS collaboration

    2013-01-01

    The upgrade for the ATLAS detector will undergo different phases towards HL-LHC. The first upgrade for the Pixel Detector (Phase 1) consists in the construction of a new pixel layer, which will be installed during the 1st long shutdown of the LHC machine (LS1) in 2013/14. The new detector, called Insertable B-Layer (IBL), will be inserted between the existing pixel detector and a new (smaller radius) beam-pipe at a radius of about 3.2 cm. The IBL requires the development of several new technologies to cope with the increase of radiation and pixel occupancy as well as to improve the physics performance of the existing pixel detector. The pixel size is reduced and the material budget is minimized by using new lightweight mechanical support materials and a CO2 based cooling system. For Phase 2 upgrade of LHC a complete new 4-layer pixel system is planned as part of a new all silicon Inner Detector. The increase in luminosity to about $5\\cdot 10^{34}$cm$^{-2}$s$^{-1}$ together with a total expected lifetime of ab...

  7. LISe pixel detector for neutron imaging

    Science.gov (United States)

    Herrera, Elan; Hamm, Daniel; Wiggins, Brenden; Milburn, Rob; Burger, Arnold; Bilheux, Hassina; Santodonato, Louis; Chvala, Ondrej; Stowe, Ashley; Lukosi, Eric

    2016-10-01

    Semiconducting lithium indium diselenide, 6LiInSe2 or LISe, has promising characteristics for neutron detection applications. The 95% isotopic enrichment of 6Li results in a highly efficient thermal neutron-sensitive material. In this study, we report on a proof-of-principle investigation of a semiconducting LISe pixel detector to demonstrate its potential as an efficient neutron imager. The LISe pixel detector had a 4×4 of pixels with a 550 μm pitch on a 5×5×0.56 mm3 LISe substrate. An experimentally verified spatial resolution of 300 μm was observed utilizing a super-sampling technique.

  8. Pixel detectors from fundamentals to applications

    CERN Document Server

    Rossi, Leonardo; Rohe, Tilman; Wermes, Norbert

    2006-01-01

    Pixel detectors are a particularly important class of particle and radiation detection devices. They have an extremely broad spectrum of applications, ranging from high-energy physics to the photo cameras of everyday life. This book is a general purpose introduction into the fundamental principles of pixel detector technology and semiconductor-based hybrid pixel devices. Although these devices were developed for high-energy ionizing particles and radiation beyond visible light, they are finding new applications in many other areas. This book will therefore benefit all scientists and engineers working in any laboratory involved in developing or using particle detection.

  9. Anode readout for pixellated CZT detectors

    Science.gov (United States)

    Narita, Tomohiko; Grindlay, Jonathan E.; Hong, Jaesub; Niestemski, Francis C.

    2004-02-01

    Determination of the photon interaction depth offers numerous advantages for an astronomical hard X-ray telescope. The interaction depth is typically derived from two signals: anode and cathode, or collecting and non-collecting electrodes. We present some preliminary results from our depth sensing detectors using only the anode pixel signals. By examining several anode pixel signals simultaneously, we find that we can estimate the interaction depth, and get sub-pixel 2-D position resolution. We discuss our findings and the requirements for future ASIC development.

  10. Spiral biasing adaptor for use in Si drift detectors and Si drift detector arrays

    Energy Technology Data Exchange (ETDEWEB)

    Li, Zheng; Chen, Wei

    2016-07-05

    A drift detector array, preferably a silicon drift detector (SDD) array, that uses a low current biasing adaptor is disclosed. The biasing adaptor is customizable for any desired geometry of the drift detector single cell with minimum drift time of carriers. The biasing adaptor has spiral shaped ion-implants that generate the desired voltage profile. The biasing adaptor can be processed on the same wafer as the drift detector array and only one biasing adaptor chip/side is needed for one drift detector array to generate the voltage profiles on the front side and back side of the detector array.

  11. Adopt a Pixel Photographs: 2013-Present

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — The photographs in the Adopt a Pixel collection were provided by volunteers with a digital camera, a Global Positioning System (GPS), and a compass or a smart mobile...

  12. Adopt a Pixel Photographs: 2013-Present

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — The photographs in the Adopt a Pixel collection were provided by volunteers with a digital camera, a Global Positioning System (GPS), and a compass or a smart mobile...

  13. Adopt a Pixel Photographs: 2013-Present

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — The photographs in the Adopt a Pixel collection were provided by volunteers with a digital camera, a Global Positioning System (GPS), and a compass or a smart...

  14. Limits to Drift Chamber Resolution

    CERN Document Server

    Riegler, Werner

    1998-01-01

    ATLAS (A Large Toroidal LHC Apparatus) will be a general-purpose experiment at the Large Hadron Collider that will be operational at CERN in the year 2004. The ATLAS muon spectrometer aims for a momentum resolution of 10% for a transverse momentum of pT=1TeV. The precision tracking devices in the muon system will be high pressure drift tubes (MDTs) with a single wire resolution of 1100 chambers covering an area of ≈ 2500m2. The high counting rates in the spectrometer as well as the aim for excellent spatial resolution and high efficiency put severe constraints on the MDT operating parameters. This work describes a detailed study of all the resolution limiting factors in the ATLAS environment. A ’full chain’ simulation of the MDT response to photons and charged particles as well as quantitative comparisons with measurements was performed. The good agreement between simulation and measurements resulted in a profound understanding of the drift chamber processes and the individual contributions to the spat...

  15. Analysis of Full Charge Reconstruction Algorithms for X-Ray Pixelated Detectors

    Energy Technology Data Exchange (ETDEWEB)

    Baumbaugh, A.; /Fermilab; Carini, G.; /SLAC; Deptuch, G.; /Fermilab; Grybos, P.; /AGH-UST, Cracow; Hoff, J.; /Fermilab; Siddons, P., Maj.; /Brookhaven; Szczygiel, R.; /AGH-UST, Cracow; Trimpl, M.; Yarema, R.; /Fermilab

    2012-05-21

    Existence of the natural diffusive spread of charge carriers on the course of their drift towards collecting electrodes in planar, segmented detectors results in a division of the original cloud of carriers between neighboring channels. This paper presents the analysis of algorithms, implementable with reasonable circuit resources, whose task is to prevent degradation of the detective quantum efficiency in highly granular, digital pixel detectors. The immediate motivation of the work is a photon science application requesting simultaneous timing spectroscopy and 2D position sensitivity. Leading edge discrimination, provided it can be freed from uncertainties associated with the charge sharing, is used for timing the events. Analyzed solutions can naturally be extended to the amplitude spectroscopy with pixel detectors.

  16. Analysis of full charge reconstruction algorithms for x-ray pixelated detectors

    Energy Technology Data Exchange (ETDEWEB)

    Baumbaugh, A.; /Fermilab; Carini, G.; /SLAC; Deptuch, G.; /Fermilab; Grybos, P.; /AGH-UST, Cracow; Hoff, J.; /Fermilab; Siddons, P., Maj.; /Brookhaven; Szczygiel, R.; /AGH-UST, Cracow; Trimpl, M.; Yarema, R.; /Fermilab

    2011-11-01

    Existence of the natural diffusive spread of charge carriers on the course of their drift towards collecting electrodes in planar, segmented detectors results in a division of the original cloud of carriers between neighboring channels. This paper presents the analysis of algorithms, implementable with reasonable circuit resources, whose task is to prevent degradation of the detective quantum efficiency in highly granular, digital pixel detectors. The immediate motivation of the work is a photon science application requesting simultaneous timing spectroscopy and 2D position sensitivity. Leading edge discrimination, provided it can be freed from uncertainties associated with the charge sharing, is used for timing the events. Analyzed solutions can naturally be extended to the amplitude spectroscopy with pixel detectors.

  17. Drift chamber tracking with neural networks

    Energy Technology Data Exchange (ETDEWEB)

    Lindsey, C.S.; Denby, B.; Haggerty, H.

    1992-10-01

    We discuss drift chamber tracking with a commercial log VLSI neural network chip. Voltages proportional to the drift times in a 4-layer drift chamber were presented to the Intel ETANN chip. The network was trained to provide the intercept and slope of straight tracks traversing the chamber. The outputs were recorded and later compared off line to conventional track fits. Two types of network architectures were studied. Applications of neural network tracking to high energy physics detector triggers is discussed.

  18. Snow Drift Management: Summit Station Greenland

    Science.gov (United States)

    2016-05-01

    ER D C/ CR RE L TR -1 6- 6 Engineering for Polar Operations, Logistics, and Research (EPOLAR) Snow Drift Management Summit Station...Drift Management Summit Station Greenland Robert B. Haehnel and Matthew F. Bigl U.S. Army Engineer Research and Development Center (ERDC) Cold...Engineering for Polar Operations, Logistics, and Research (EPOLAR) EP-ARC-15-33, “Monitoring and Managing Snow Drifting at Summit Station, Greenland” ERDC

  19. Simulation study of pixel detector charge digitization

    Science.gov (United States)

    Wang, Fuyue; Nachman, Benjamin; Sciveres, Maurice; Lawrence Berkeley National Laboratory Team

    2017-01-01

    Reconstruction of tracks from nearly overlapping particles, called Tracking in Dense Environments (TIDE), is an increasingly important component of many physics analyses at the Large Hadron Collider as signatures involving highly boosted jets are investigated. TIDE makes use of the charge distribution inside a pixel cluster to resolve tracks that share one of more of their pixel detector hits. In practice, the pixel charge is discretized using the Time-over-Threshold (ToT) technique. More charge information is better for discrimination, but more challenging for designing and operating the detector. A model of the silicon pixels has been developed in order to study the impact of the precision of the digitized charge distribution on distinguishing multi-particle clusters. The output of the GEANT4-based simulation is used to train neutral networks that predict the multiplicity and location of particles depositing energy inside one cluster of pixels. By studying the multi-particle cluster identification efficiency and position resolution, we quantify the trade-off between the number of ToT bits and low-level tracking inputs. As both ATLAS and CMS are designing upgraded detectors, this work provides guidance for the pixel module designs to meet TIDE needs. Work funded by the China Scholarship Council and the Office of High Energy Physics of the U.S. Department of Energy under contract DE-AC02-05CH11231.

  20. Redshift drift in a pressure gradient cosmology

    CERN Document Server

    Balcerzak, Adam

    2012-01-01

    We derive the redshift drift formula for the inhomogeneous pressure spherically symmetric Stephani universes which are complementary to inhomogeneous density Lema\\^itre-Tolman-Bondi (LTB) models. We show that there is a clear difference between the redshift drift predictions for these two models. The Stephani models have positive drift values at small redshift and behave qualitatively as the $\\Lambda$CDM models while the drift for LTB models is always negative. This prediction can be tested in future space experiments such as E-ELT, TMT, GMT or CODEX.

  1. THERMAL EVALUATION OF DIFFERENT DRIFT DIAMETER SIZES

    Energy Technology Data Exchange (ETDEWEB)

    H.M. Wade

    1999-01-04

    The purpose of this calculation is to estimate the thermal response of a repository-emplaced waste package and its corresponding drift wall surface temperature with different drift diameters. The case examined is that of a 21 pressurized water reactor (PWR) uncanistered fuel (UCF) waste package loaded with design basis spent nuclear fuel assemblies. This calculation evaluates a 3.5 meter to 6.5 meter drift diameter range in increments of 1.0 meters. The time-dependent temperatures of interest, as determined by this calculation, are the spent nuclear fuel cladding temperature, the waste package surface temperature, and the drift wall surface temperature.

  2. RF Breakdown in Drift Tube Linacs

    CERN Document Server

    Stovall, J; Lown, R

    2009-01-01

    The highest RF electric field in drift-tube linacs (DTLs) often occurs on the face of the first drift tube. Typically this drift tube contains a quadrupole focusing magnet whose fringing fields penetrate the face of the drift tube parallel to the RF electric fields in the accelerating gap. It has been shown that the threshold for RF breakdown in RF cavities may be reduced in the presence of a static magnetic field. This note offers a “rule of thumb” for picking the maximum “safe” surface electric field in DTLs based on these measurements.

  3. Focal plane array with modular pixel array components for scalability

    Energy Technology Data Exchange (ETDEWEB)

    Kay, Randolph R; Campbell, David V; Shinde, Subhash L; Rienstra, Jeffrey L; Serkland, Darwin K; Holmes, Michael L

    2014-12-09

    A modular, scalable focal plane array is provided as an array of integrated circuit dice, wherein each die includes a given amount of modular pixel array circuitry. The array of dice effectively multiplies the amount of modular pixel array circuitry to produce a larger pixel array without increasing die size. Desired pixel pitch across the enlarged pixel array is preserved by forming die stacks with each pixel array circuitry die stacked on a separate die that contains the corresponding signal processing circuitry. Techniques for die stack interconnections and die stack placement are implemented to ensure that the desired pixel pitch is preserved across the enlarged pixel array.

  4. Region based elimination of noise pixels towards optimized classifier models for skin pixel detection

    Directory of Open Access Journals (Sweden)

    Gagandeep Kaur

    2015-03-01

    Full Text Available The extraction of the skin pixels in a human image and rejection of non-skin pixels is called the skin segmentation. Skin pixel detection is the process of extracting the skin pixels in a human image which is typically used as a pre-processing step to extract the face regions from human image. In past, there are several computer vision approaches and techniques have been developed for skin pixel detection. In the process of skin detection, given pixels are been transformed into an appropriate color space such as RGB, HSV etc. And then skin classifier model have been applied to label the pixel into skin or non-skin regions. Here in this research a “Region based elimination of noise pixels and performance analysis of classifier models for skin pixel detection applied on human images” would be performed which involve the process of image representation in color models, elimination of non-skin pixels in the image, and then pre-processing and cleansing of the collected data, feature selection of the human image and then building the model for classifier. In this research and implementation of skin pixels classifier models are proposed with their comparative performance analysis. The definition of the feature vector is simply the selection of skin pixels from the human image or stack of human images. The performance is evaluated by comparing and analysing skin colour segmentation algorithms. During the course of research implementation, efforts are iterative which help in selection of optimized skin classifier based on the machine learning algorithms and their performance analysis.

  5. First operation of a pixel imaging matrix based on DEPFET pixels

    CERN Document Server

    Fischer, P; Klein, P; Löcker, M; Lutz, Gerhard; Neeser, W; Strüder, L; Wermes, N

    2000-01-01

    In the DEPFET pixel concept the detected incident radiation is directly sensed and amplified by a JFET integrated in every pixel cell. While the DEPFET detector principle has already been demonstrated previously on single pixel structures, we present here the first successful operation of a large $32 \\times 32$ DEPFET pixel matrix as an imaging device. The matrix has been exposed to 60 keV gamma rays of a $^{241}$Am source and has been scanned using an IR laser. The principle of operation as well as the charge collection in the structure and possible improvements are discussed.

  6. Fermilab drift tube Linac revisited

    Energy Technology Data Exchange (ETDEWEB)

    Milorad Popovic

    2004-05-12

    Using the PARMILA code running under PC-WINDOWS, the present performance of the Fermilab Drift Tube Linac has been analyzed in the light of new demands on the Linac/Booster complex (the Proton Source). The Fermilab Drift Tube Linac (DTL) was designed in the sixties as a proton linac with a final energy of 200 MeV and a peak current of 100mA. In the seventies, in order to enable multi-turn charge exchange injection into the Booster, the ion source was replaced by an H- source with a peak beam current of 25mA. Since then the peak beam current was steadily increased up to 55mA. In the early nineties, part of the drift tube structure was replaced with a side-coupled cavity structure in order to increase the final energy to 400 MeV. The original and still primary purpose of the linac is to serve as the injector for the Booster. As an added benefit, the Neutron Therapy Facility (NTF) was built in the middle seventies. It uses 66MeV protons from the Linac to produce neutrons for medical purposes. The Linac/Booster complex was designed to run at a fundamental cycling rate of 15Hz, but beam is accelerated on every cycle only when NTF is running. Until recently the demand from the High Energy Physics program resulted in an average linac beam repetition rate of order 1 Hz. With the MiniBoone experiment and the NuMI program, the demands on the Proton Source have changed, with emphasis on higher beam repetition rates up to 7.5Hz. Historically the beam losses in the linac were small, localized at one spot, so activation was not an important issue. With higher beam rate, this has the potential to become the dominant issue. Until today all tuning in the linac and Proton Source was governed by two goals: to maximize the peak beam current out of the linac and to minimize the beam losses in the linac. If maximal peak current from the linac is no longer a primary goal, then the linac quadrupoles can be adjusted differently to achieve different goals.

  7. Study of Morphological Defects on Dual-Band HgCdTe on CdZnTe

    Science.gov (United States)

    Reddy, M.; Radford, W. A.; Lofgreen, D. D.; Olsson, K. R.; Peterson, J. M.; Johnson, S. M.

    2014-08-01

    HgCdTe dual-band epitaxial layers on lattice-matched CdZnTe substrates often have morphological defects. These defects, unlike normal void and microvoid defects, do not contain a polycrystalline core and, therefore, do not offer a good contrast for observation using optical and electron microscopes. This paper reports a way of identifying these defects by using a Nomarski optical microscopy image overlay on focused ion beam microscopy images for preparation of thin cross-sectional foils of these defects. Transmission electron microscopy was used to study the defect cross-sections to identify the origin and evolution of the morphological defects and their effect on the epitaxial layer. This paper reports cross-sectional analysis of four morphological defects of different shape and size.

  8. An effect of the networks of the subgrain boundaries on spectral responses of thick CdZnTe detectors

    Energy Technology Data Exchange (ETDEWEB)

    Bolotnikov, A.; Butcher, J.; Camarda, G.; Cui, Y.; Egarievwe, S.; Fochuk, P.; Gul,R.; Hamade, M.; Hossain, A.; Kim, K.; Kopach,O.; Petryk, M.; Raghothamachar, B.; Yang, G.; and James, R.B.

    2011-08-12

    CdZnTe (CZT) crystals used for nuclear-radiation detectors often contain high concentrations of subgrain boundaries and networks of poligonized dislocations that can significantly degrade the performance of semiconductor devices. These defects exist in all commercial CZT materials, regardless of their growth techniques and their vendor. We describe our new results from examining such detectors using IR transmission microscopy and white X-ray beam diffraction topography. We emphasize the roles on the devices performances of networks of subgrain boundaries with low dislocation densities, such as poligonized dislocations and mosaic structures. Specifically, we evaluated their effects on the gamma-ray responses of thick, >10 mm, CZT detectors. Our findings set the lower limit on the energy resolution of CZT detectors containing dense networks of subgrain boundaries, and walls of dislocations.

  9. Parallel readout of two-element CdZnTe detectors with real-time digital signal processing

    Energy Technology Data Exchange (ETDEWEB)

    Shi Zhubin; Wang Linjun; Qin Kaifeng; Min Jiahua; Zhang Jijun; Liang Xiaoyan; Huang Jian; Tang Ke; Xia Yiben, E-mail: ljwang@shu.edu.cn [School of Materials Science and Engineering, Shanghai University, Shanghai 200072 (China)

    2010-12-15

    Readout electronics, especially digital electronics, for two-element CdZnTe (CZT) detectors in parallel are developed. The preliminary results show the detection efficiency of the two-element CZT detectors in parallel with analog electronics is as many as 1.8 and 2.1 times the single ones, and the energy resolution (FWHM) is limited by that of the single one by the means of analog electronics. However, the digital method for signal processing will be sufficiently better by contrast with an analog method especially in energy resolution. The energy resolution by the means of digital electronics can be improved by about 26.67%, compared to that only with analog electronics, while their detection efficiency is almost the same. The cause for this difference is also discussed. (semiconductor devices)

  10. CdTe and CdZnTe gamma ray detectors for medical and industrial imaging systems

    CERN Document Server

    Eisen, Y; Mardor, I

    1999-01-01

    CdTe and CdZnTe X-ray and gamma ray detectors in the form of single elements or as segmented monolithic detectors have been shown to be useful in medical and industrial imaging systems. These detectors possess inherently better energy resolution than scintillators coupled to either photodiodes or photomultipliers, and together with application specific integrated circuits they lead to compact imaging systems of enhanced spatial resolution and better contrast resolution. Photopeak efficiencies of these detectors is greatly affected by a relatively low hole mobility-lifetime product. Utilizing these detectors as highly efficient good spectrometers, demands use of techniques to improve their charge collection properties, i.e., correct for variations in charge losses at different depths of interaction in the detector. The corrections for the large hole trapping are made either by applying electronic techniques or by fabricating detector or electrical contacts configurations which differ from the commonly used pla...

  11. Growth by the Multi-tube Physical Vapour Transport method and characterisation of bulk (Cd,Zn)Te

    Science.gov (United States)

    Choubey, A.; Veeramani, P.; Pym, A. T. G.; Mullins, J. T.; Sellin, P. J.; Brinkman, A. W.; Radley, I.; Basu, A.; Tanner, B. K.

    2012-08-01

    Growth by the Multi-tube Physical Vapour Transport technique and characterisation of bulk (Cd,Zn)Te is described. The crystalline perfection and uniformity of zinc content have been mapped by infra-red transmission and microscopy, X-ray diffraction and photoluminescence. X-ray double crystal rocking curve full widths at half maximum as low as 43 in have been obtained and a mean zinc mole fraction of 0.03 has been found to vary by less than ±0.003 over the diameter of a 50 mm boule. The material exhibits a resistivity in the 2×109Ω cm range and planar devices fabricated from this material have shown electron mobility lifetime products of 4.07×10-3 cm2 V-1.

  12. SEMICONDUCTOR DEVICES Parallel readout of two-element CdZnTe detectors with real-time digital signal processing

    Science.gov (United States)

    Zhubin, Shi; Linjun, Wang; Kaifeng, Qin; Jiahua, Min; Jijun, Zhang; Xiaoyan, Liang; Jian, Huang; Ke, Tang; Yiben, Xia

    2010-12-01

    Readout electronics, especially digital electronics, for two-element CdZnTe (CZT) detectors in parallel are developed. The preliminary results show the detection efficiency of the two-element CZT detectors in parallel with analog electronics is as many as 1.8 and 2.1 times the single ones, and the energy resolution (FWHM) is limited by that of the single one by the means of analog electronics. However, the digital method for signal processing will be sufficiently better by contrast with an analog method especially in energy resolution. The energy resolution by the means of digital electronics can be improved by about 26.67%, compared to that only with analog electronics, while their detection efficiency is almost the same. The cause for this difference is also discussed.

  13. Spatial clustering of pixels of a multispectral image

    Energy Technology Data Exchange (ETDEWEB)

    Conger, James Lynn

    2014-08-19

    A method and system for clustering the pixels of a multispectral image is provided. A clustering system computes a maximum spectral similarity score for each pixel that indicates the similarity between that pixel and the most similar neighboring. To determine the maximum similarity score for a pixel, the clustering system generates a similarity score between that pixel and each of its neighboring pixels and then selects the similarity score that represents the highest similarity as the maximum similarity score. The clustering system may apply a filtering criterion based on the maximum similarity score so that pixels with similarity scores below a minimum threshold are not clustered. The clustering system changes the current pixel values of the pixels in a cluster based on an averaging of the original pixel values of the pixels in the cluster.

  14. Spatial clustering of pixels of a multispectral image

    Science.gov (United States)

    Conger, James Lynn

    2014-08-19

    A method and system for clustering the pixels of a multispectral image is provided. A clustering system computes a maximum spectral similarity score for each pixel that indicates the similarity between that pixel and the most similar neighboring. To determine the maximum similarity score for a pixel, the clustering system generates a similarity score between that pixel and each of its neighboring pixels and then selects the similarity score that represents the highest similarity as the maximum similarity score. The clustering system may apply a filtering criterion based on the maximum similarity score so that pixels with similarity scores below a minimum threshold are not clustered. The clustering system changes the current pixel values of the pixels in a cluster based on an averaging of the original pixel values of the pixels in the cluster.

  15. Silicon drift detectors with the drift field induced by pureB-coated trenches

    NARCIS (Netherlands)

    Nanver, Lis Karen; Kneževi´c, Tihomir; Suligoj, Tomislav

    2016-01-01

    Junction formation in deep trenches is proposed as a new means of creating a built-in drift field in silicon drift detectors (SDDs). The potential performance of this trenched drift detector (TDD) was investigated analytically and through simulations, and compared to simulations of conventional

  16. The Genetic Drift Inventory: A Tool for Measuring What Advanced Undergraduates Have Mastered about Genetic Drift

    Science.gov (United States)

    Price, Rebecca M.; Andrews, Tessa C.; McElhinny, Teresa L.; Mead, Louise S.; Abraham, Joel K.; Thanukos, Anna; Perez, Kathryn E.

    2014-01-01

    Understanding genetic drift is crucial for a comprehensive understanding of biology, yet it is difficult to learn because it combines the conceptual challenges of both evolution and randomness. To help assess strategies for teaching genetic drift, we have developed and evaluated the Genetic Drift Inventory (GeDI), a concept inventory that measures…

  17. Autoresonant control of drift waves

    Science.gov (United States)

    Shagalov, A. G.; Rasmussen, J. Juul; Naulin, V.

    2017-03-01

    The control of nonlinear drift waves in a magnetized plasmas column has been investigated. The studies are based on the Hasegawa–Mima model, which is solved on a disk domain with radial inhomogeneity of the plasma density. The system is forced by a rotating potential with varying frequency defined on the boundary. To excite and control the waves we apply the autoresonant effect, taking place when the amplitude of the forcing exceeds a threshold value and the waves are phase-locked with the forcing. We demonstrate that the autoresonant approach is applicable for excitation of a range of steady nonlinear waves of the lowest azimuthal mode numbers and for controlling their amplitudes and phases. We also demonstrate the excitation of zonal flows (m = 0 modes), which are controlled via the forced modes.

  18. Autoresonant control of drift waves

    DEFF Research Database (Denmark)

    Shagalov, A.G.; Rasmussen, Jens Juul; Naulin, Volker

    2017-01-01

    The control of nonlinear drift waves in a magnetized plasmas column has been investigated. The studies are based on the Hasegawa–Mima model, which is solved on a disk domain with radial inhomogeneity of the plasma density. The system is forced by a rotating potential with varying frequency defined...... on the boundary. To excite and control the waves we apply the autoresonant effect, taking place when the amplitude of the forcing exceeds a threshold value and the waves are phase-locked with the forcing. We demonstrate that the autoresonant approach is applicable for excitation of a range of steady nonlinear...... waves of the lowest azimuthal mode numbers and for controlling their amplitudes and phases. We also demonstrate the excitation of zonal flows (m = 0 modes), which are controlled via the forced modes....

  19. The ARGUS microvertex drift chamber

    Science.gov (United States)

    Michel, E.; Schmidt-Parzefall, W.; Appuhn, R. D.; Buchmüller, J.; Kolanoski, H.; Kreimeier, B.; Lange, A.; Siegmund, T.; Walther, A.; Edwards, K. W.; Fernholz, R. C.; Kapitza, H.; MacFarlane, D. B.; O'Neill, M.; Parsons, J. A.; Prentice, J. D.; Seidel, S. C.; Tsipolitis, G.; Ball, S.; Babaev, A.; Danilov, M.; Tichomirov, I.

    1989-11-01

    The ARGUS collaboration is currently building a new microvertex drift chamber (μVDC) as an upgrade of their detector. The μVDC is optimized for B-meson physics at DORIS energies. Important design features are minimal multiple scattering for low-momentum particles and three-dimensional reconstruction of decay vertices with equal resolutions in r- φ and r- z. Vertex resolutions of 15-25 μm are expected. Prototypes of the μVDC have been tested with different gas mixtures at various pressures. Spatial resolutions as small as 20 μm were obtained using CO 2/propane at 4 bar and DME at 1 bar. New readout electronics have been developed for the μVDC aiming at low thresholds for the TDC measurements. Employing a novel idea for noise and cross-talk suppression, which is based on a discrimination against short pulses, very low threshold settings are possible.

  20. Design and performances of a low-noise and radiation-hardened readout ASIC for CdZnTe detectors

    Science.gov (United States)

    Bo, Gan; Tingcun, Wei; Wu, Gao; Yongcai, Hu

    2016-06-01

    In this paper, we present the design and performances of a low-noise and radiation-hardened front-end readout application specific integrated circuit (ASIC) dedicated to CdZnTe detectors for a hard X-ray imager in space applications. The readout channel is comprised of a charge sensitive amplifier, a CR-RC shaping amplifier, an analog output buffer, a fast shaper, and a discriminator. An 8-channel prototype ASIC is designed and fabricated in TSMC 0.35-μm mixed-signal CMOS technology, the die size of the prototype chip is 2.2 × 2.2 mm2. The input energy range is from 5 to 350 keV. For this 8-channel prototype ASIC, the measured electrical characteristics are as follows: the overall gain of the readout channel is 210 V/pC, the linearity error is less than 2%, the crosstalk is less than 0.36%, The equivalent noise charge of a typical channel is 52.9 e- at zero farad plus 8.2 e- per picofarad, and the power consumption is less than 2.4 mW/channel. Through the measurement together with a CdZnTe detector, the energy resolution is 5.9% at the 59.5-keV line under the irradiation of the radioactive source 241Am. The radiation effect experiments show that the proposed ASIC can resist the total ionization dose (TID) irradiation of higher than 200 krad(Si). Project supported by the National Key Scientific Instrument and Equipment Development Project (No. 2011YQ040082), the National Natural Science Foundation of China (Nos. 11475136, 11575144, 61176094), and the Shaanxi Natural Science Foundation of China (No. 2015JM1016).

  1. Recent advances in Tl Br, Cd Te and CdZnTe semiconductor radiation detectors: a review

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Icimone B. [Universidade Bandeirante (UNIBAN), Sao Paulo, SP (Brazil)

    2011-07-01

    The success in the development of radiation spectrometers operating at room temperature is based on many years of effort on the part of large numbers of workers around the world. These individuals have contributed to the understanding of the fundamental materials issues associated with the growth of semiconductors for this application, the development of device fabrication and processing technology, and advances in low noise electronics and pulse processing. Progress in this field continues at an accelerated pace, as in evidenced by the improvements in detector performance and by the growing number of commercial products. Thus, the last years have been seen continued effort in the development of room temperature compound semiconductors devices. High-Z compound semiconductor detectors has been explored for high energy resolution, high detection efficiency and are of low cost. Compound semiconductors detectors are well suited for addressing needs of demanding applications such as bore hole logging where high operating temperature are encountered. In this work recent developments in semiconductors detectors were reviewed. This review concentrated on thallium bromide (TlBr), cadmium zinc telluride (CdZnTe) and cadmium telluride (CdTe) crystals detectors. TlBr has higher stopping power compared to common semiconductor materials because it has the higher photoelectric and total attenuation coefficients over wide energy range from 100 keV to 1 MeV. CdTe and CdZnTe detectors have several attractive features for detecting X-ray and low energy gamma ray. Their relatively large band gaps lead to a relatively low leakage current and offer an excellent energy resolution at room temperature. A literature survey and bibliography was also included. (author)

  2. Drift wave in pair-ion plasma

    Indian Academy of Sciences (India)

    Samiran Ghosh; Nikhil Chakrabarti; Manoranjan Khan; M R Gupta

    2013-02-01

    The conditions for the existence of low-frequency electrostatic drift wave in pair-ion plasma are discussed. It is shown that the temperature and/or mass difference of both species could produce drift wave in a pair-ion plasma. The results are discussed in the context of the fullerene pair-ion plasma experiment.

  3. Resistive Drift Waves in a Bumpy Torus

    Energy Technology Data Exchange (ETDEWEB)

    J.L.V. Lewandowski

    2004-01-12

    A computational study of resistive drift waves in the edge plasma of a bumpy torus is presented. The magnetohydrodynamic equilibrium is obtained from a three-dimensional local equilibrium model. The use of a local magnetohydrodynamic equilibrium model allows for a computationally efficient systematic study of the impact of the magnetic field structure on drift wave stability.

  4. Biology Undergraduates' Misconceptions about Genetic Drift

    Science.gov (United States)

    Andrews, T. M.; Price, R. M.; Mead, L. S.; McElhinny, T. L.; Thanukos, A.; Perez, K. E.; Herreid, C. F.; Terry, D. R.; Lemons, P. P.

    2012-01-01

    This study explores biology undergraduates' misconceptions about genetic drift. We use qualitative and quantitative methods to describe students' definitions, identify common misconceptions, and examine differences before and after instruction on genetic drift. We identify and describe five overarching categories that include 16 distinct…

  5. Do Arctic waders use adaptive wind drift?

    NARCIS (Netherlands)

    Green, M; Alerstam, T; Gudmundsson, GA; Hedenstrom, A; Piersma, T; Gudmundsson, Gudmundur A.; Hedenström, Anders

    2004-01-01

    We analysed five data sets of night directions of migrating arctic waders ill relation to,winds, recorded by tracking radar and optical range finder, in order to find out if these birds compensate for wind drift, or allow themselves to be drifted by winds. Our purpose was to investigate whether arct

  6. Learning under Concept Drift: an Overview

    CERN Document Server

    e, Indr\\ e Žliobait\\

    2010-01-01

    Concept drift refers to a non stationary learning problem over time. The training and the application data often mismatch in real life problems. In this report we present a context of concept drift problem 1. We focus on the issues relevant to adaptive training set formation. We present the framework and terminology, and formulate a global picture of concept drift learners design. We start with formalizing the framework for the concept drifting data in Section 1. In Section 2 we discuss the adaptivity mechanisms of the concept drift learners. In Section 3 we overview the principle mechanisms of concept drift learners. In this chapter we give a general picture of the available algorithms and categorize them based on their properties. Section 5 discusses the related research fields and Section 5 groups and presents major concept drift applications. This report is intended to give a bird's view of concept drift research field, provide a context of the research and position it within broad spectrum of research fi...

  7. A logarithmic low dark current CMOS pixel

    Science.gov (United States)

    Brunetti, Alessandro Michel; Choubey, Bhaskar

    2016-04-01

    High dynamic range pixels are required in a number of automotive and scientific applications. CMOS pixels provide different approaches to achieve this. However, these suffer from poor performance under low light conditions due to inherently high leakage current that is present in CMOS processes, also known as dark current. The typical approach to reduce this dark current involves process modifications. Nevertheless, energy considerations suggest that the leakage current will be close to zero at a close to zero voltage on the photodiode. Hence, the reduction in dark current can be achieved by forcing a zero voltage across the photodiode. In this paper, a novel logarithmic CMOS pixel design capable of reducing dark current without any process modifications is proposed. This pixel is also able to produce a wide dynamic range response. This circuit utilizes two current mirrors to force the in-pixel photodiode at a close to zero voltage. Additionally, a bias voltage is used to reduce a higher order effect known as Drain Induced Barrier Lowering (DIBL). In fact, the contribution of this effect can be compensated by increasing the body effect. In this paper, we studied the consequences of a negative bias voltage applied to the body of the current mirror pair to compensate for the DIBL effect thereby achieving a very small voltage drop on the photodiode and consequently, a higher sensitivity in low light conditions.

  8. Preparation of Cd(Zn)Te and CuInSe sub 2 films and devices by a two-stage process

    Energy Technology Data Exchange (ETDEWEB)

    Basol, B.M.; Kapur, V.K. (International Solar Electric Technology (ISET), Inglewood, CA (USA))

    1991-05-01

    The two-stage process was used to prepare thin films of Cd(Zn)Te and CuInSe{sub 2}. The technique involves first depositing the elemental components of the compound onto a substrate in the form of thin stacked layers and then reacting these elemental components to obtain a thin film of the desired compound. While CdTe films grown on thin CdS layers have uniform stoichiometries and sharp interfaces with the underlying CdS layers, CdZnTe films deposited onto similar substrates give rise to diffused CdZnTe-CdS interfaces because of the reactive nature of zinc. In CuInSe{sub 2} processing, the nature of the reacted compound film strongly depends on the nature of the Cu-In layers. CdS/CuInSe{sub 2} device efficiencies are also influenced by the method of deposition for the CdS window layers. (orig.).

  9. Dissipative drift instability in dusty plasma

    Directory of Open Access Journals (Sweden)

    Nilakshi Das

    2012-03-01

    Full Text Available An investigation has been done on the very low-frequency electrostatic drift waves in a collisional dusty plasma. The dust density gradient is taken perpendicular to the magnetic field B0⃗, which causes the drift wave. In this case, low-frequency drift instabilities can be driven by E1⃗×B0⃗ and diamagnetic drifts, where E1⃗ is the perturbed electric field. Dust charge fluctuation is also taken into consideration for our study. The dust- neutral and ion-neutral collision terms have been included in equations of motion. It is seen that the low-frequency drift instability gets damped in such a system. Both dust charging and collision of plasma particles with the neutrals may be responsible for the damping of the wave. Both analytical and numerical techniques have been used while developing the theory.

  10. Ground Control for Emplacement Drifts for LA

    Energy Technology Data Exchange (ETDEWEB)

    Y. Sun

    2004-07-09

    The purpose of this calculation is to analyze the stability of repository emplacement drifts during the preclosure period, and to provide a final ground support method for emplacement drifts for the License Application (LA). The scope of the work includes determination of input parameter values and loads, selection of appropriate process and methods for the calculation, application of selected methods, such as empirical or analytical, to the calculation, development and execution of numerical models, and evaluation of results. Results from this calculation are limited to use for design of the emplacement drifts and the final ground support system installed in these drifts. The design of non-emplacement openings and their ground support systems is covered in the ''Ground Control for Non-Emplacement Drifts for LA'' (BSC 2004c).

  11. Radiation Tolerance of CMOS Monolithic Active Pixel Sensors with Self-Biased Pixels

    CERN Document Server

    Deveaux, M; Besson, A; Claus, G; Colledani, C; Dorokhov, M; Dritsa, C; Dulinski, W; Fröhlich, I; Goffe, M; Grandjean, D; Heini, S; Himmi, A; Hu, C; Jaaskelainen, K; Müntz, C; Shabetai, A; Stroth, J; Szelezniak, M; Valin, I; Winter, M

    2009-01-01

    CMOS Monolithic Active Pixel Sensors (MAPS) are proposed as a technology for various vertex detectors in nuclear and particle physics. We discuss the mechanisms of ionizing radiation damage on MAPS hosting the the dead time free, so-called self bias pixel. Moreover, we discuss radiation hardened sensor designs which allow operating detectors after exposing them to irradiation doses above 1 Mrad

  12. Field investigation of the drift shadow

    Energy Technology Data Exchange (ETDEWEB)

    Su, Grace W.; Kneafsey, Timothy J.; Ghezzehei, Teamrat A.; Marshall, Brian D.; Cook, Paul J.

    2005-09-08

    A drift shadow is an area immediately beneath an undergroundvoidthat, in theory, will be relatively drier than the surrounding rockmass. Numerical and analytical models of water flow through unsaturatedrock predict the existence of a drift shadow, but field tests confirmingits existence have yet to be performed. Proving the existence of driftshadows and understanding their hydrologic and transport characteristicscould provide a better understanding of how contaminants move in thesubsurface if released from waste emplacement drifts such as the proposednuclear waste repository at Yucca Mountain, Nevada. We describe the fieldprogram that will be used to investigate the existence of a drift shadowand the corresponding hydrological process at the Hazel-Atlas silica-sandmine located at the Black Diamond Mines Regional Preserve in Antioch,California. The location and configuration of this mine makes it anexcellent site to observe and measure drift shadow characteristics. Themine is located in a porous sandstone unit of the Domengine Formation, anapproximately 230 meter thick series of interbedded Eocene-age shales,coals, and massive-bedded sandstones. The mining method used at the minerequired the development of two parallel drifts, one above the other,driven along the strike of the mined sandstone stratum. Thisconfiguration provides the opportunity to introduce water into the rockmass in the upper drift and to observe and measure its flow around theunderlying drift. The passive and active hydrologic tests to be performedare described. In the passive method, cores will be obtained in a radialpattern around a drift and will be sectioned and analyzed for in-situwater content and chemical constituents. With the active hydrologic test,water will be introduced into the upper drift of the two parallel driftsand the flow of the water will be tracked as it passes near the bottomdrift. Tensiometers, electrical resistance probes, neutron probes, andground penetrating radar may be

  13. Development of CMOS Pixel Sensors with digital pixel dedicated to future particle physics experiments

    Science.gov (United States)

    Zhao, W.; Wang, T.; Pham, H.; Hu-Guo, C.; Dorokhov, A.; Hu, Y.

    2014-02-01

    Two prototypes of CMOS pixel sensor with in-pixel analog to digital conversion have been developed in a 0.18 μm CIS process. The first design integrates a discriminator into each pixel within an area of 22 × 33 μm2 in order to meet the requirements of the ALICE inner tracking system (ALICE-ITS) upgrade. The second design features 3-bit charge encoding inside a 35 × 35 μm2 pixel which is motivated by the specifications of the outer layers of the ILD vertex detector (ILD-VXD). This work aims to validate the concept of in-pixel digitization which offers higher readout speed, lower power consumption and less dead zone compared with the column-level charge encoding.

  14. The pin pixel detector--neutron imaging

    CERN Document Server

    Bateman, J E; Derbyshire, G E; Duxbury, D M; Marsh, A S; Rhodes, N J; Schooneveld, E M; Simmons, J E; Stephenson, R

    2002-01-01

    The development and testing of a neutron gas pixel detector intended for application in neutron diffraction studies is reported. Using standard electrical connector pins as point anodes, the detector is based on a commercial 100 pin connector block. A prototype detector of aperture 25.4 mmx25.4 mm has been fabricated, giving a pixel size of 2.54 mm which matches well to the spatial resolution typically required in a neutron diffractometer. A 2-Dimensional resistive divide readout system has been adapted to permit the imaging properties of the detector to be explored in advance of true pixel readout electronics. The timing properties of the device match well to the requirements of the ISIS-pulsed neutron source.

  15. Infrared single-pixel imaging utilising microscanning

    CERN Document Server

    Sun, Ming-Jie; Phillips, David B; Gibson, Graham M; Padgett, Miles J

    2015-01-01

    Since the invention of digital cameras there has been a concerted drive towards detector arrays with higher spatial resolution. Microscanning is a technique that provides a final higher resolution image by combining multiple images of a lower resolution. Each of these low resolution images is subject to a sub-pixel sized lateral displacement. In this work we apply the microscanning approach to an infrared single-pixel camera. For the same final resolution and measurement resource, we show that microscanning improves the signal-to-noise ratio (SNR) of reconstructed images by approximately 50%. In addition, this strategy also provides access to a stream of low-resolution 'preview' images throughout each high-resolution acquisition. Our work demonstrates an additional degree of flexibility in the trade-off between SNR and spatial resolution in single-pixel imaging techniques.

  16. Towards spark-proof gaseous pixel detectors

    Science.gov (United States)

    Tsigaridas, S.; Beuzekom, M. v.; Chan, H. W.; Graaf, H. v. d.; Hartjes, F.; Heijhoff, K.; Hessey, N. P.; Prodanovic, V.

    2016-11-01

    The micro-pattern gaseous pixel detector, is a promising technology for imaging and particle tracking applications. It is a combination of a gas layer acting as detection medium and a CMOS pixelated readout-chip. As a prevention against discharges we deposit a protection layer on the chip and then integrate on top a micromegas-like amplification structure. With this technology we are able to reconstruct 3D track segments of particles passing through the gas thanks to the functionality of the chip. We have turned a Timepix3 chip into a gaseous pixel detector and tested it at the SPS at Cern. The preliminary results are promising and within the expectations. However, the spark protection layer needs further improvement to make reliable detectors. For this reason, we have created a setup for spark-testing. We present the first results obtained from the lab-measurements along with preliminary results from the testbeam.

  17. Per-Pixel Lighting Data Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Inanici, Mehlika

    2005-08-01

    This report presents a framework for per-pixel analysis of the qualitative and quantitative aspects of luminous environments. Recognizing the need for better lighting analysis capabilities and appreciating the new measurement abilities developed within the LBNL Lighting Measurement and Simulation Toolbox, ''Per-pixel Lighting Data Analysis'' project demonstrates several techniques for analyzing luminance distribution patterns, luminance ratios, adaptation luminance and glare assessment. The techniques are the syntheses of the current practices in lighting design and the unique practices that can be done with per-pixel data availability. Demonstrated analysis techniques are applicable to both computer-generated and digitally captured images (physically-based renderings and High Dynamic Range photographs).

  18. Performance of active edge pixel sensors

    Science.gov (United States)

    Bomben, M.; Ducourthial, A.; Bagolini, A.; Boscardin, M.; Bosisio, L.; Calderini, G.; D'Eramo, L.; Giacomini, G.; Marchiori, G.; Zorzi, N.; Rummler, A.; Weingarten, J.

    2017-05-01

    To cope with the High Luminosity LHC harsh conditions, the ATLAS inner tracker has to be upgraded to meet requirements in terms of radiation hardness, pile up and geometrical acceptance. The active edge technology allows to reduce the insensitive area at the border of the sensor thanks to an ion etched trench which avoids the crystal damage produced by the standard mechanical dicing process. Thin planar n-on-p pixel sensors with active edge have been designed and produced by LPNHE and FBK foundry. Two detector module prototypes, consisting of pixel sensors connected to FE-I4B readout chips, have been tested with beams at CERN and DESY. In this paper the performance of these modules are reported. In particular the lateral extension of the detection volume, beyond the pixel region, is investigated and the results show high hit efficiency also at the detector edge, even in presence of guard rings.

  19. Active Pixel Sensors: Are CCD's Dinosaurs?

    Science.gov (United States)

    Fossum, Eric R.

    1993-01-01

    Charge-coupled devices (CCD's) are presently the technology of choice for most imaging applications. In the 23 years since their invention in 1970, they have evolved to a sophisticated level of performance. However, as with all technologies, we can be certain that they will be supplanted someday. In this paper, the Active Pixel Sensor (APS) technology is explored as a possible successor to the CCD. An active pixel is defined as a detector array technology that has at least one active transistor within the pixel unit cell. The APS eliminates the need for nearly perfect charge transfer -- the Achilles' heel of CCDs. This perfect charge transfer makes CCD's radiation 'soft,' difficult to use under low light conditions, difficult to manufacture in large array sizes, difficult to integrate with on-chip electronics, difficult to use at low temperatures, difficult to use at high frame rates, and difficult to manufacture in non-silicon materials that extend wavelength response.

  20. Drift velocity and pressure monitoring of the CMS muon drift chambers

    CERN Document Server

    Sonnenschein, Lars

    2011-01-01

    The drift velocity in drift tubes of the CMS muon chambers is a key parameter for the muon track reconstruction and trigger. It needs to be monitored precisely in order to detect any deviation from its nominal value. A change in absolute pressure, a variation of the gas admixture or a contamination of the chamber gas by air affect the drift velocity. Furthermore, the temperature and magnetic field influence its value. First data, taken with a dedicated Velocity Drift Chamber (VDC) built by RWTH Aachen IIIA are presented. Another important parameter to be monitored is the pressure inside the muon drift tube chambers. The differential pressure must not exceed a certain value and the absolute pressure has to be kept slightly above ambient pressure to prevent air from entering into the muon drift tube chambers in case of a leak. Latest drift velocity monitoring results are discussed.

  1. Drift velocity and pressure monitoring of the CMS muon drift chambers

    CERN Document Server

    Sonnenschein, Lars

    2010-01-01

    The drift velocity in drift tubes of the CMS muon chambers is a key parameter for the muon track reconstruction and trigger. It needs to be monitored precisely in order to detect any deviation from its nominal value. A change in absolute pressure, a variation of the gas admixture or a contamination of the chamber gas by air affect the drift velocity. Furthermore, the temperature and magnetic field influence its value. First data, taken with a dedicated Velocity Drift Chamber (VDC) built by RWTH Aachen IIIA are presented. Another important parameter to be monitored is the pressure inside the muon drift tube chambers because the drift velocity depends on it. Furthermore the differential pressure must not exceed a certain value and the absolute pressure has to be kept slightly above ambient pressure to prevent air from entering into the muon drift tube chambers in case of a leak. Latest pressure monitoring results are discussed.

  2. Point Defects in Pb-, Bi-, and In-Doped CdZnTe Detectors:Deep-Level Transient Spectroscopy (DLTS) Measurements

    Energy Technology Data Exchange (ETDEWEB)

    Bolotnikov A.; GUL, R.; KEETER, K.; RODRIGUEZ, R.; BOLOTNIKOV, A.E.; HOSSAIN, A.; CAMARDA, G.S.; KIM, K.H.; YANG, Y.; CUI, Y.; CARCELEN, V.; FRANC, J.; LI, Z.; JAMES, R.B.

    2012-02-29

    We studied, by current deep-level transient spectroscopy (I-DLTS), point defects induced in CdZnTe detectors by three dopants: Pb, Bi, and In. Pb-doped CdZnTe detectors have a new acceptor trap at around 0.48 eV. The absence of a V{sub Cd} trap suggests that all Cd vacancies are compensated by Pb interstitials after they form a deep-acceptor complex [[Pb{sub Cd}]{sup +}-V{sub Cd}{sup 2-}]{sup -}. Bi-doped CdZnTe detectors had two distinct traps: a shallow trap at around 36 meV and a deep donor trap at around 0.82 eV. In detectors doped with In, we noted three well-known traps: two acceptor levels at around 0.18 eV (A-centers) and 0.31 eV (V{sub Cd}), and a deep trap at around 1.1 eV.

  3. Physics performance of the ATLAS pixel detector

    Science.gov (United States)

    Tsuno, S.

    2017-01-01

    In preparation for LHC Run-2 the ATLAS detector introduced a new pixel detector, the Insertable B-Layer (IBL). This detector is located between the beampipe and what was the innermost pixel layer. The tracking and vertex reconstruction are significantly improved and good performance is expected in high level objects such a b-quark jet tagging. This in turn, leads to better physics results. This note summarizes the impact of the IBL detector on physics results, especially focusing on the analyses using b-quark jets throughout 2016 summer physics program.

  4. Commissioning of the ATLAS pixel detector

    Energy Technology Data Exchange (ETDEWEB)

    ATLAS Collaboration; Golling, Tobias

    2008-09-01

    The ATLAS pixel detector is a high precision silicon tracking device located closest to the LHC interaction point. It belongs to the first generation of its kind in a hadron collider experiment. It will provide crucial pattern recognition information and will largely determine the ability of ATLAS to precisely track particle trajectories and find secondary vertices. It was the last detector to be installed in ATLAS in June 2007, has been fully connected and tested in-situ during spring and summer 2008, and is ready for the imminent LHC turn-on. The highlights of the past and future commissioning activities of the ATLAS pixel system are presented.

  5. Physics performance of the ATLAS Pixel Detector

    CERN Document Server

    Tsuno, Soshi; The ATLAS collaboration

    2016-01-01

    One noticeable upgrade from Run-1 to Run-2 with ATLAS detector in proton-proton collisions at LHC is the introduction of the new pixel detector, IBL, located on the beam pipe as the extra innermost pixel layer. The tracking and vertex reconstruction are significantly improved and good performance is expected in high level object such a $b$-quark jet tagging, in turn, it leads the better physics results. This note summarizes what is the impact on the IBL detector to the physics results especially focusing on the analyses using the $b$-quark jets throughout 2016 summer physics program.

  6. Solving the drift control problem

    Directory of Open Access Journals (Sweden)

    Melda Ormeci Matoglu

    2015-12-01

    Full Text Available We model the problem of managing capacity in a build-to-order environment as a Brownian drift control problem. We formulate a structured linear program that models a practical discretization of the problem and exploit a strong relationship between relative value functions and dual solutions to develop a functional lower bound for the continuous problem from a dual solution to the discrete problem. Refining the discretization proves a functional strong duality for the continuous problem. The linear programming formulation is so badly scaled, however, that solving it is beyond the capabilities of standard solvers. By demonstrating the equivalence between strongly feasible bases and deterministic unichain policies, we combinatorialize the pivoting process and by exploiting the relationship between dual solutions and relative value functions, develop a mechanism for solving the LP without ever computing its coefficients. Finally, we exploit the relationship between relative value functions and dual solutions to develop a scheme analogous to column generation for refining the discretization so as to drive the gap between the discrete approximation and the continuous problem to zero quickly while keeping the LP small. Computational studies show our scheme is much faster than simply solving a regular discretization of the problem both in terms of finding a policy with a low average cost and in terms of providing a lower bound on the optimal average cost.

  7. Genetic drift of HIV populations in culture.

    Directory of Open Access Journals (Sweden)

    Yegor Voronin

    2009-03-01

    Full Text Available Populations of Human Immunodeficiency Virus type 1 (HIV-1 undergo a surprisingly large amount of genetic drift in infected patients despite very large population sizes, which are predicted to be mostly deterministic. Several models have been proposed to explain this phenomenon, but all of them implicitly assume that the process of virus replication itself does not contribute to genetic drift. We developed an assay to measure the amount of genetic drift for HIV populations replicating in cell culture. The assay relies on creation of HIV populations of known size and measurements of variation in frequency of a neutral allele. Using this assay, we show that HIV undergoes approximately ten times more genetic drift than would be expected from its population size, which we defined as the number of infected cells in the culture. We showed that a large portion of the increase in genetic drift is due to non-synchronous infection of target cells. When infections are synchronized, genetic drift for the virus is only 3-fold higher than expected from its population size. Thus, the stochastic nature of biological processes involved in viral replication contributes to increased genetic drift in HIV populations. We propose that appreciation of these effects will allow better understanding of the evolutionary forces acting on HIV in infected patients.

  8. Correction of image drift and distortion in a scanning electron microscopy.

    Science.gov (United States)

    Jin, P; Li, X

    2015-12-01

    Continuous research on small-scale mechanical structures and systems has attracted strong demand for ultrafine deformation and strain measurements. Conventional optical microscope cannot meet such requirements owing to its lower spatial resolution. Therefore, high-resolution scanning electron microscope has become the preferred system for high spatial resolution imaging and measurements. However, scanning electron microscope usually is contaminated by distortion and drift aberrations which cause serious errors to precise imaging and measurements of tiny structures. This paper develops a new method to correct drift and distortion aberrations of scanning electron microscope images, and evaluates the effect of correction by comparing corrected images with scanning electron microscope image of a standard sample. The drift correction is based on the interpolation scheme, where a series of images are captured at one location of the sample and perform image correlation between the first image and the consequent images to interpolate the drift-time relationship of scanning electron microscope images. The distortion correction employs the axial symmetry model of charged particle imaging theory to two images sharing with the same location of one object under different imaging fields of view. The difference apart from rigid displacement between the mentioned two images will give distortion parameters. Three-order precision is considered in the model and experiment shows that one pixel maximum correction is obtained for the employed high-resolution electron microscopic system.

  9. Real-space post-processing correction of thermal drift and piezoelectric actuator nonlinearities in scanning tunneling microscope images

    CERN Document Server

    Yothers, Mitchell P; Bumm, Lloyd A

    2016-01-01

    We have developed a real-space method to correct distortion due to thermal drift and piezoelectric actuator nonlinearities on scanning tunneling microscope images using Matlab. The method uses the known structures typically present in high-resolution atomic and molecularly-resolved images as an internal standard. Each image feature (atom or molecule) is first identified in the image. The locations of each feature's nearest neighbors (NNs) are used to measure the local distortion at that location. The local distortion map across the image is simultaneously fit to our distortion model, which includes thermal drift in addition to piezoelectric actuator hysteresis and creep. The image coordinates of the features and image pixels are corrected using an inverse transform from the distortion model. We call this technique the thermal-drift, hysteresis, and creep transform (DHCT). Performing the correction in real space allows defects, domain boundaries, and step edges to be excluded with a spatial mask. Additional re...

  10. Pixels simultaneous detection probabilities and spatial resolution determination of pixelized detectors by means of correlation measurements

    CERN Document Server

    Grabskii, V

    2007-01-01

    A novel method to estimate the pixels simultaneous detection probability and the spatial resolution of pixelized detectors is proposed, which is based on the determination of the statistical correlations between detector neighbor pixels. The correlations are determined by means of noise variance measurement for a isolated pixels and the difference between neighbor pixels. The method is validated using images from the two different GE Senographe 2000D mammographic units. The pixelized detector has been irradiated using x-rays along its entire surface. It is shown that the pixel simultaneous detection probabilities can be estimated within accuracy 0.001 - 0.003, where the systematic error is estimated to be smaller than 0.005. The presampled two-dimensional point-spread function (PSF0) is determined using a single Gaussian and a sum of two Gaussian approximations. The obtained results for the presampled PSF0 show that the single Gaussian approximation is not appropriate, and the sum of two Gaussian approximatio...

  11. From Hybrid to CMOS Pixels ... a possibility for LHC's pixel future?

    CERN Document Server

    Wermes, Norbert

    2015-01-01

    Hybrid pixel detectors have been invented for the LHC to make tracking and vertexing possible at all in LHC's radiation intense environment. The LHC pixel detectors have meanwhile very successfully fulfilled their promises and R\\&D for the planned HL-LHC upgrade is in full swing, targeting even higher ionising doses and non-ionising fluences. In terms of rate and radiation tolerance hybrid pixels are unrivaled. But they have disadvantages as well, most notably material thickness, production complexity, and cost. Meanwhile also active pixel sensors (DEPFET, MAPS) have become real pixel detectors but they would by far not stand the rates and radiation faced from HL-LHC. New MAPS developments, so-called DMAPS (depleted MAPS) which are full CMOS-pixel structures with charge collection in a depleted region have come in the R\\&D focus for pixels at high rate/radiation levels. This goal can perhaps be realised exploiting HV technologies, high ohmic substrates and/or SOI based technologies. The paper covers t...

  12. Collisional Drift Waves in Stellarator Plasmas

    Energy Technology Data Exchange (ETDEWEB)

    J.L.V. Lewandowski

    2003-10-07

    A computational study of resistive drift waves in the edge plasma of a stellarator with an helical magnetic axis is presented. Three coupled field equations, describing the collisional drift wave dynamics in the linear approximation, are solved as an initial-value problem along the magnetic field line. The magnetohydrodynamic equilibrium is obtained from a three-dimensional local equilibrium model. The use of a local magnetohydrodynamic equilibrium model allows for a computationally efficient systematic study of the impact of the magnetic field structure on drift wave stability.

  13. Current-driven electron drift solitons

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, Ali, E-mail: aliahmad79@hotmail.com [National Centre for Physics (NCP), Shahdara Valley Road, 44000 Islamabad (Pakistan); Department of Physics, COMSATS Institute of Information Technology (CIIT) Islamabad (Pakistan); Saleem, H. [National Centre for Physics (NCP), Shahdara Valley Road, 44000 Islamabad (Pakistan); Department of Physics, COMSATS Institute of Information Technology (CIIT) Islamabad (Pakistan)

    2013-12-09

    The soliton formation by the current-driven drift-like wave is investigated for heavier ion (such as barium) plasma experiments planned to be performed in future. It is pointed out that the sheared flow of electrons can give rise to short scale solitary structures in the presence of stationary heavier ions. The nonlinearity appears due to convective term in the parallel equation of motion and not because of temperature gradient unlike the case of low frequency usual drift wave soliton. This higher frequency drift-like wave requires sheared flow of electrons and not the density gradient to exist.

  14. Nonlinear Gyrokinetic Theory With Polarization Drift

    Energy Technology Data Exchange (ETDEWEB)

    L. Wang and T.S. Hahm

    2010-03-25

    A set of the electrostatic toroidal gyrokinetic Vlasov equation and the Poisson equation, which explicitly includes the polarization drift, is derived systematically by using Lie-transform method. The polarization drift is introduced in the gyrocenter equations of motion, and the corresponding polarization density is derived. Contrary to the wide-spread expectation, the inclusion of the polarization drift in the gyrocenter equations of motion does not affect the expression for the polarization density significantly. This is due to modification of the gyrocenter phase-space volume caused by the electrostatic potential [T. S. Hahm, Phys. Plasmas 3, 4658 (1996)] .

  15. Element gain drifts as an imaging dynamic range limitation in PAF-based interferometers

    CERN Document Server

    Smirnov, O M

    2011-01-01

    Interferometry with phased-array feeds (PAFs) presents new calibration challenges in comparison with single-pixel feeds. In particular, temporal instability of the compound beam patterns due to element gain drifts (EGDs) can produce calibration artefacts in interferometric images. To translate imaging dynamic range requirements into PAF hardware and calibration requirements, we must learn to relate EGD levels to imaging artefact levels. We present a MeqTrees-based simulations framework that addresses this problem, and apply it to the APERTIF prototype currently in development for the WSRT.

  16. Planar pixel sensors in commercial CMOS technologies

    Energy Technology Data Exchange (ETDEWEB)

    Gonella, Laura; Hemperek, Tomasz; Huegging, Fabian; Krueger, Hans; Wermes, Norbert [Physikalisches Institut der Universitaet Bonn, Nussallee 12, 53115 Bonn (Germany); Macchiolo, Anna [Max-Planck-Institut fuer Physik, Foehringer Ring 6, 80805 Muenchen (Germany)

    2015-07-01

    For the upgrade of the ATLAS experiment at the high luminosity LHC, an all-silicon tracker is foreseen to cope with the increased rate and radiation levels. Pixel and strip detectors will have to cover an area of up to 200m2. To produce modules in high number at reduced costs, new sensor and bonding technologies have to be investigated. Commercial CMOS technologies on high resistive substrates can provide significant advantages in this direction. They offer cost effective, large volume sensor production. In addition to this, production is done on 8'' wafers allowing wafer-to-wafer bonding to the electronics, an interconnection technology substantially cheaper than the bump bonding process used for hybrid pixel detectors at the LHC. Both active and passive n-in-p pixel sensor prototypes have been submitted in a 150 nm CMOS technology on a 2kΩ cm substrate. The passive sensor design will be used to characterize sensor properties and to investigate wafer-to-wafer bonding technologies. This first prototype is made of a matrix of 36 x 16 pixels of size compatible with the FE-I4 readout chip (i.e. 50 μm x 250 μm). Results from lab characterization of this first submission are shown together with TCAD simulations. Work towards a full size FE-I4 sensor for wafer-to-wafer bonding is discussed.

  17. Sensor development for the CMS pixel detector

    CERN Document Server

    Bölla, G; Horisberger, R P; Kaufmann, R; Rohe, T; Roy, A

    2002-01-01

    The CMS experiment which is currently under construction at the Large Hadron Collider (LHC) at CERN (Geneva, Switzerland) will contain a pixel detector which provides in its final configuration three space points per track close to the interaction point of the colliding beams. Because of the harsh radiation environment of the LHC, the technical realization of the pixel detector is extremely challenging. The readout chip as the most damageable part of the system is believed to survive a particle fluence of 6x10 sup 1 sup 4 n sub e sub q /cm sup 2 (All fluences are normalized to 1 MeV neutrons and therefore all components of the hybrid pixel detector have to perform well up to at least this fluence. As this requires a partially depleted operation of the silicon sensors after irradiation-induced type inversion of the substrate, an ''n in n'' concept has been chosen. In order to perform IV-tests on wafer level and to hold accidentally unconnected pixels close to ground potential, a resistive path between the pixe...

  18. What's A Pixel Particle Sensor Chip?

    CERN Multimedia

    2008-01-01

    ATLAS particle physics experiment aided with collaboration ON Semiconductor was recently honored by the European Council for Nuclear Research (CERN), with an Industrial Award recognizing the company's contribution in supplying complex "Pixel Particle Sensor" chips for use in CERN's ATLAS particle physics experiment.

  19. Dense Iterative Contextual Pixel Classification using Kriging

    DEFF Research Database (Denmark)

    Ganz, Melanie; Loog, Marco; Brandt, Sami

    2009-01-01

    have been proposed to this end, e.g., iterative contextual pixel classification, iterated conditional modes, and other approaches related to Markov random fields. A problem of these methods, however, is their computational complexity, especially when dealing with high-resolution images in which...

  20. CMS has a heart of pixels

    CERN Multimedia

    2003-01-01

    At the core of CMS, particles will come into contact with tiny detector components, known as pixels, which are almost invisible to the naked eye. With these elementary cells measuring a mere 150 microns (or about 1/10 of a millimetre) along each side, a real technological leap has been made.

  1. ATLAS Pixel Group - Photo Gallery from Irradiation

    CERN Multimedia

    2001-01-01

    Photos 1,2,3,4,5,6,7 - Photos taken before irradiation of Pixel Test Analog Chip and Pmbars (April 2000) Photos 8,9,10,11 - Irradiation of VDC chips (May 2000) Photos 12, 13 - Irradiation of Passive Components (June 2000) Photos 14,15, 16 - Irradiation of Marebo Chip (November 1999)

  2. Performance of active edge pixel sensors

    CERN Document Server

    Bomben, Marco; Bagolini, Alvise; Boscardin, Maurizio; Bosisio, Luciano; Calderini, Giovanni; D'Eramo, Louis; Giacomini, Gabriele; Marchiori, Giovanni; Zorzi, Nicola; Rummler, Andre; Weingarten, Jens

    2017-01-01

    this paper the performance of these modules are reported. In particular the lateral extension of the detection volume, beyond the pixel region, is investigated and the results show high hit efficiency also at the detector edge, even in presence of guard rings.

  3. Dynamic holography using pixelated light modulators.

    Science.gov (United States)

    Zwick, Susanne; Haist, Tobias; Warber, Michael; Osten, Wolfgang

    2010-09-01

    Dynamic holography using spatial light modulators is a very flexible technique that offers various new applications compared to static holography. We give an overview on the technical background of dynamic holography focusing on pixelated spatial light modulators and their technical restrictions, and we present a selection of the numerous applications of dynamic holography.

  4. Precision feature point tracking method using a drift-correcting template update strategy

    Science.gov (United States)

    Peng, Xiaoming; Ma, Qian; Zhang, Qiheng; Chen, Wufan; Xu, Zhiyong

    2009-02-01

    We present a drift-correcting template update strategy for precisely tracking a feature point in 2D image sequences in this paper. The proposed strategy greatly extends Matthews et al's template tracking strategy [I. Matthews, T. Ishikawa and S. Baker, The template update problem, IEEE Trans. PAMI 26 (2004) 810-815.] by incorporating a robust non-rigid image registration step used in medical imaging. Matthews et al's strategy uses the first template to correct drifts in the current template; however, the drift would still build up if the first template becomes quite different from the current one as the tracking continues. In our strategy the first template is updated timely when it is quite different from the current one, and henceforth the updated first template can be used to correct template drifts in subsequent frames. The method based on the proposed strategy yields sub-pixel accuracy tracking results measured by the commercial software REALVIZ(R) MatchMover(R) Pro 4.0. Our method runs fast on a desktop PC (3.0 GHz Pentium(R) IV CPU, 1GB RAM, Windows(R) XP professional operating system, Microsoft Visual C++ 6.0 (R) programming), using about 0.03 seconds on average to track the feature point in a frame (under the assumption of a general affine transformation model, 61×61 pixels in template size) and when required, less than 0.1 seconds to update the first template. We also propose the architecture for implementing our strategy in parallel.

  5. Maximizing Kepler science return per telemetered pixel: Detailed models of the focal plane in the two-wheel era

    CERN Document Server

    Hogg, David W; Barclay, Tom; Dawson, Rebekah; Fergus, Rob; Foreman-Mackey, Dan; Harmeling, Stefan; Hirsch, Michael; Lang, Dustin; Montet, Benjamin T; Schiminovich, David; Schölkopf, Bernhard

    2013-01-01

    Kepler's immense photometric precision to date was maintained through satellite stability and precise pointing. In this white paper, we argue that image modeling--fitting the Kepler-downlinked raw pixel data--can vastly improve the precision of Kepler in pointing-degraded two-wheel mode. We argue that a non-trivial modeling effort may permit continuance of photometry at 10-ppm-level precision. We demonstrate some baby steps towards precise models in both data-driven (flexible) and physics-driven (interpretably parameterized) modes. We demonstrate that the expected drift or jitter in positions in the two-weel era will help with constraining calibration parameters. In particular, we show that we can infer the device flat-field at higher than pixel resolution; that is, we can infer pixel-to-pixel variations in intra-pixel sensitivity. These results are relevant to almost any scientific goal for the repurposed mission; image modeling ought to be a part of any two-wheel repurpose for the satellite. We make other r...

  6. Vacuum condensates and `ether-drift' experiments

    OpenAIRE

    Consoli, M.; Pagano, A.; Pappalardo, L.

    2003-01-01

    The idea of a `condensed' vacuum state is generally accepted in modern elementary particle physics. We argue that this should motivate a new generation of precise `ether-drift' experiments with present-day technology.

  7. An analytical model of iceberg drift

    CERN Document Server

    Wagner, Till J W; Eisenman, Ian

    2016-01-01

    Iceberg drift and decay and the associated freshwater release are increasingly seen as important processes in Earth's climate system, yet a detailed understanding of their dynamics has remained elusive. Here, an idealized model of iceberg drift is presented. The model is designed to include the most salient physical processes that determine iceberg motion while remaining sufficiently simple to facilitate physical insight into iceberg drift dynamics. We derive an analytical solution of the model, which helps build understanding and also enables the rapid computation of large numbers of iceberg trajectories. The long-standing empirical rule of thumb that icebergs drift at 2% of the wind velocity, relative to the ocean current, is derived here from physical first principles, and it is shown that this relation only holds in the limit of strong winds or small icebergs, which approximately applies for typical icebergs in the Arctic. It is demonstrated that the opposite limit of weak winds or large icebergs approxim...

  8. Stabilization Strategies for Drift Tube Linacs

    CERN Document Server

    AUTHOR|(CDS)2085420; Lamehi Rashti, Mohammad

    The average axial electric fields in drift tube linac cavities are known to be sensitive with respect to the perturbation errors. Postcoupler is a powerful stabilizer devices that is used to reduce this sensitivity of average axial field. Postcouplers are the cylindrical rod which is extended from cavity wall toward the drift tube without touching the drift tube surface. Postcouplers need to be adjusted to the right length to stabilize the average axial field. Although postcouplers are used successfully in many projects, there is no straightforward procedure for postcouplers adjustment and it has been done almost based on trial and errors. In this thesis, the physics and characteristics of postcouplers has been studied by using an equivalent circuit model and 3D finite element method calculations. Finally, a straightforward and accurate method to adjust postcouplers has been concluded. The method has been verified by using experimental measurements on CERN Linac4 drift tube linac cavities.

  9. CROSS DRIFT ALCOVE/NICHE UTILITIES ANALYSIS

    Energy Technology Data Exchange (ETDEWEB)

    S. Goodin

    1999-07-08

    The purpose of this analysis is to provide the design basis and general arrangement requirements of the non-potable water, waste water, compressed air and ventilation (post excavation) utilities required in support of the Cross Drift alcoves and niches.

  10. The Electron Drift Instrument for MMS

    Science.gov (United States)

    Torbert, R. B.; Vaith, H.; Granoff, M.; Widholm, M.; Gaidos, J. A.; Briggs, B. H.; Dors, I. G.; Chutter, M. W.; Macri, J.; Argall, M.; Bodet, D.; Needell, J.; Steller, M. B.; Baumjohann, W.; Nakamura, R.; Plaschke, F.; Ottacher, H.; Hasiba, J.; Hofmann, K.; Kletzing, C. A.; Bounds, S. R.; Dvorsky, R. T.; Sigsbee, K.; Kooi, V.

    2016-03-01

    The Electron Drift Instrument (EDI) on the Magnetospheric Multiscale (MMS) mission measures the in-situ electric and magnetic fields using the drift of a weak beam of test electrons that, when emitted in certain directions, return to the spacecraft after one or more gyrations. This drift is related to the electric field and, to a lesser extent, the gradient in the magnetic field. Although these two quantities can be determined separately by use of different electron energies, for MMS regions of interest the magnetic field gradient contribution is negligible. As a by-product of the drift determination, the magnetic field strength and constraints on its direction are also determined. The present paper describes the scientific objectives, the experimental method, and the technical realization of the various elements of the instrument on MMS.

  11. Nonlinear electrostatic drift Kelvin-Helmholtz instability

    Science.gov (United States)

    Sharma, Avadhesh C.; Srivastava, Krishna M.

    1993-01-01

    Nonlinear analysis of electrostatic drift Kelvin-Helmholtz instability is performed. It is shown that the analysis leads to the propagation of the weakly nonlinear dispersive waves, and the nonlinear behavior is governed by the nonlinear Burger's equation.

  12. Self-shielding flex-circuit drift tube, drift tube assembly and method of making

    Energy Technology Data Exchange (ETDEWEB)

    Jones, David Alexander

    2016-04-26

    The present disclosure is directed to an ion mobility drift tube fabricated using flex-circuit technology in which every other drift electrode is on a different layer of the flex-circuit and each drift electrode partially overlaps the adjacent electrodes on the other layer. This results in a self-shielding effect where the drift electrodes themselves shield the interior of the drift tube from unwanted electro-magnetic noise. In addition, this drift tube can be manufactured with an integral flex-heater for temperature control. This design will significantly improve the noise immunity, size, weight, and power requirements of hand-held ion mobility systems such as those used for explosive detection.

  13. Monte Carlo investigation of charge-transport effects on energy resolution and detection efficiency of pixelated CZT detectors for SPECT/PET applications.

    Science.gov (United States)

    Myronakis, Marios E; Darambara, Dimitra G

    2011-01-01

    Semiconductor detectors are increasingly considered as alternatives to scintillation crystals for nuclear imaging applications such as positron emission tomography (PET) or single photon emission computed tomography (SPECT). One of the most prominent detector materials is cadmium zinc telluride (CZT), which is currently used in several application-specific nuclear imaging systems. In this work, the charge-transport effects in pixelated CZT detectors in relation to detector pixel size and thickness are investigated for pixels sizes from 0.4 up to 1.6 mm. The determination of an optimum pixel size and thickness for use with photon energies of 140 and 511 keV, suitable for SPECT and PET studies, is attempted using photon detection efficiency and energy resolution as figures of merit. The Monte Carlo method combined with detailed finite element analysis was utilized to realistically model photon interactions in the detector and the signal generation process. The GEANT4 Application for Tomographic Emission (GATE) toolkit was used for photon irradiation and interaction simulations. The COMSOL MULTIPHYSICS software application was used to create finite element models of the detector that included charge drift, diffusion, trapping, and generation. Data obtained from the two methods were combined to generate accurate signal induction at the detector pixels. The energy resolution was calculated as the full width at half maximum of the energy spectrum photopeak. Photon detection efficiency was also calculated. The effects of charge transport within the detector and photon escape from primary pixel of interaction were investigated; the extent of diffusion to lateral pixels was also assessed. Charge transport and signal induction were affected by the position of a pixel in the detector. Edge and corner pixels were less susceptible to lateral diffusion than pixels located in the inner part of the detector. Higher detection efficiency and increased photon escape from primary

  14. Characterization of Depleted Monolithic Active Pixel detectors implemented with a high-resistive CMOS technology

    Science.gov (United States)

    Kishishita, T.; Hemperek, T.; Rymaszewski, P.; Hirono, T.; Krüger, H.; Wermes, N.

    2016-07-01

    We present the recent development of DMAPS (Depleted Monolithic Active Pixel Sensor), implemented with a Toshiba 130 nm CMOS process. Unlike in the case of standard MAPS technologies which are based on an epi-layer, this process provides a high-resistive substrate that enables larger signal and faster charge collection by drift in a 50 - 300 μm thick depleted layer. Since this process also enables the use of deep n-wells to isolate the collection electrodes from the thin active device layer, NMOS and PMOS transistors are available for the readout electronics in each pixel cell. In order to characterize the technology, we implemented a simple three transistor readout with a variety of pixel pitches and input FET sizes. This layout variety gives us a clue on sensor characteristics for future optimization, such as the input detector capacitance or leakage current. In the initial measurement, the radiation spectra were obtained from 55Fe with an energy resolution of 770 eV (FWHM) and 90Sr with the MVP of 4165 e-.

  15. The Bipolar Quantum Drift-diffusion Model

    Institute of Scientific and Technical Information of China (English)

    Xiu Qing CHEN; Li CHEN

    2009-01-01

    A fourth order parabolic system, the bipolar quantum drift-diffusion model in semiconductor simulation, with physically motivated Dirichlet-Neumann boundary condition is studied in this paper. By semidiscretization in time and compactness argument, the global existence and semiclassical limit are obtained, in which semiclassical limit describes the relation between quantum and classical drift-diffusion models. Furthermore, in the case of constant doping, we prove the weak solution exponentially approaches its constant steady state as time increases to infinity.

  16. Drift waves in a weakly ionized plasma

    DEFF Research Database (Denmark)

    Popovic, M.; Melchior, H.

    1968-01-01

    A dispersion relation for low frequency drift waves in a weakly ionized plasma has been derived, and through numerical calculations the effect of collisions between the charged and the neutral particles is estimated.......A dispersion relation for low frequency drift waves in a weakly ionized plasma has been derived, and through numerical calculations the effect of collisions between the charged and the neutral particles is estimated....

  17. Strange Attractors in Drift Wave Turbulence

    Energy Technology Data Exchange (ETDEWEB)

    J.L.V. Lewandowski

    2003-04-25

    A multi-grid part-in-cell algorithm for a shearless slab drift wave model with kinetic electrons is presented. The algorithm, which is based on an exact separation of adiabatic and nonadiabatic electron responses, is used to investigate the presence of strange attractors in drift wave turbulence. Although the simulation model has a large number of degrees of freedom, it is found that the strange attractor is low-dimensional and that it is strongly affected by dissipative (collisional) effects.

  18. Design Methodology: ASICs with complex in-pixel processing for Pixel Detectors

    Energy Technology Data Exchange (ETDEWEB)

    Fahim, Farah [Fermilab

    2014-10-31

    The development of Application Specific Integrated Circuits (ASIC) for pixel detectors with complex in-pixel processing using Computer Aided Design (CAD) tools that are, themselves, mainly developed for the design of conventional digital circuits requires a specialized approach. Mixed signal pixels often require parasitically aware detailed analog front-ends and extremely compact digital back-ends with more than 1000 transistors in small areas below 100μm x 100μm. These pixels are tiled to create large arrays, which have the same clock distribution and data readout speed constraints as in, for example, micro-processors. The methodology uses a modified mixed-mode on-top digital implementation flow to not only harness the tool efficiency for timing and floor-planning but also to maintain designer control over compact parasitically aware layout.

  19. Thermodynamics Insights for the Redshift Drift

    Science.gov (United States)

    Zhang, Ming-Jian; Liu, Wen-Biao

    2015-01-01

    The secular redshift drift is a potential measurement to directly probe the cosmic expansion. Previous study on the redshift drift mainly focused on the model-dependent simulation. Apparently, the physical insights on the redshift drift are very necessary. So in this paper, it is investigated using thermodynamics on the apparent, Hubble and event horizons. Thermodynamics could analytically present the model-independent upper bounds of redshift drift. For specific assumption on the cosmological parameters, we find that the thermodynamics bounds are nearly one order of magnitude larger than the expectation in standard ΛCDM model. We then examine ten observed redshift drift from Green Bank Telescope at redshift 0.09 < z < 0.69, and find that these observational results are inconsistent with the thermodynamics. The size of the errorbars on these measurements is about three orders of magnitude larger than the effect of thermodynamical bounds for the redshift drift. Obviously, we have not yet hit any instrumental systematics at the shift level of 1m s-1 yr-1.

  20. Suppressing drift chamber diffusion without magnetic field

    CERN Document Server

    Martoff, C J; Ohnuki, T; Spooner, N J C; Lehner, M

    2000-01-01

    The spatial resolution in drift chamber detectors for ionizing radiation is limited by diffusion of the primary electrons. A strong magnetic field along the drift direction is often applied (Fancher et al., Nucl. Instr. and Meth. A 161 (1979) 383) because it suppresses the transverse diffusion, improving the resolution but at considerable increase in cost and complexity. Here we show that transverse track diffusion can be strongly suppressed without any magnetic field. This is achieved by using a gas additive which reversibly captures primary ionization electrons, forming negative ions. The ions drift with thermal energies even at very high drift fields and low pressures (E/P=28.5 V/cm torr), and the diffusion decreases with increasing drift field. Upon arrival at the avalanche region of the chamber the negative ions are efficiently stripped and ordinary avalanche gain is obtained. Using this technique, r.m.s. transverse diffusion less than 200 mu m has been achieved over a 15 cm drift path at 40 torr with ze...

  1. Design methodology: edgeless 3D ASICs with complex in-pixel processing for pixel detectors

    Energy Technology Data Exchange (ETDEWEB)

    Fahim Farah, Fahim Farah [Northwestern U. (main); Deptuch, Grzegorz W. [Fermilab; Hoff, James R. [Fermilab; Mohseni, Hooman [Northwestern U. (main)

    2015-08-28

    The design methodology for the development of 3D integrated edgeless pixel detectors with in-pixel processing using Electronic Design Automation (EDA) tools is presented. A large area 3 tier 3D detector with one sensor layer and two ASIC layers containing one analog and one digital tier, is built for x-ray photon time of arrival measurement and imaging. A full custom analog pixel is 65μm x 65μm. It is connected to a sensor pixel of the same size on one side, and on the other side it has approximately 40 connections to the digital pixel. A 32 x 32 edgeless array without any peripheral functional blocks constitutes a sub-chip. The sub-chip is an indivisible unit, which is further arranged in a 6 x 6 array to create the entire 1.248cm x 1.248cm ASIC. Each chip has 720 bump-bond I/O connections, on the back of the digital tier to the ceramic PCB. All the analog tier power and biasing is conveyed through the digital tier from the PCB. The assembly has no peripheral functional blocks, and hence the active area extends to the edge of the detector. This was achieved by using a few flavors of almost identical analog pixels (minimal variation in layout) to allow for peripheral biasing blocks to be placed within pixels. The 1024 pixels within a digital sub-chip array have a variety of full custom, semi-custom and automated timing driven functional blocks placed together. The methodology uses a modified mixed-mode on-top digital implementation flow to not only harness the tool efficiency for timing and floor-planning but also to maintain designer control over compact parasitically aware layout. The methodology uses the Cadence design platform, however it is not limited to this tool.

  2. PixelSNE: Visualizing Fast with Just Enough Precision via Pixel-Aligned Stochastic Neighbor Embedding

    OpenAIRE

    Kim, Minjeong; Choi, Minsuk; Lee, Sunwoong; Tang, Jian; Park, Haesun; Choo, Jaegul

    2016-01-01

    Embedding and visualizing large-scale high-dimensional data in a two-dimensional space is an important problem since such visualization can reveal deep insights out of complex data. Most of the existing embedding approaches, however, run on an excessively high precision, ignoring the fact that at the end, embedding outputs are converted into coarse-grained discrete pixel coordinates in a screen space. Motivated by such an observation and directly considering pixel coordinates in an embedding ...

  3. Calibration of the CMS Drift Tube Chambers and Measurement of the Drift Velocity with Cosmic Rays

    CERN Document Server

    INSPIRE-00165402; Khachatryan, V; Sirunyan, A M; Adam, W; Arnold, B; Bergauer, H; Bergauer, T; Dragicevic, M; Eichberger, M; Erö, J; Friedl, M; Frühwirth, R; Ghete, V M; Hammer, J; Hänsel, S; Hoch, M; Hörmann, N; Hrubec, J; Jeitler, M; Kasieczka, G; Kastner, K; Krammer, M; Liko, D; Magrans de Abril, I; Mikulec, I; Mittermayr, F; Neuherz, B; Oberegger, M; Padrta, M; Pernicka, M; Rohringer, H; Schmid, S; Schöfbeck, R; Schreiner, T; Stark, R; Steininger, H; Strauss, J; Taurok, A; Teischinger, F; Themel, T; Uhl, D; Wagner, P; Waltenberger, W; Walzel, G; Widl, E; Wulz, C E; Chekhovsky, V; Dvornikov, O; Emeliantchik, I; Litomin, A; Makarenko, V; Marfin, I; Mossolov, V; Shumeiko, N; Solin, A; Stefanovitch, R; Suarez Gonzalez, J; Tikhonov, A; Fedorov, A; Karneyeu, A; Korzhik, M; Panov, V; Zuyeuski, R; Kuchinsky, P; Beaumont, W; Benucci, L; Cardaci, M; De Wolf, E A; Delmeire, E; Druzhkin, D; Hashemi, M; Janssen, X; Maes, T; Mucibello, L; Ochesanu, S; Rougny, R; Selvaggi, M; Van Haevermaet, H; Van Mechelen, P; Van Remortel, N; Adler, V; Beauceron, S; Blyweert, S; D'Hondt, J; De Weirdt, S; Devroede, O; Heyninck, J; Kalogeropoulos, A; Maes, J; Maes, M; Mozer, M U; Tavernier, S; Van Doninck, W; Van Mulders, P; Villella, I; Bouhali, O; Chabert, E C; Charaf, O; Clerbaux, B; De Lentdecker, G; Dero, V; Elgammal, S; Gay, A P R; Hammad, G H; Marage, P E; Rugovac, S; Vander Velde, C; Vanlaer, P; Wickens, J; Grunewald, M; Klein, B; Marinov, A; Ryckbosch, D; Thyssen, F; Tytgat, M; Vanelderen, L; Verwilligen, P; Basegmez, S; Bruno, G; Caudron, J; Delaere, C; Demin, P; Favart, D; Giammanco, A; Grégoire, G; Lemaitre, V; Militaru, O; Ovyn, S; Piotrzkowski, K; Quertenmont, L; Schul, N; Beliy, N; Daubie, E; Alves, G A; Pol, M E; Souza, M H G; Carvalho, W; De Jesus Damiao, D; De Oliveira Martins, C; Fonseca De Souza, S; Mundim, L; Oguri, V; Santoro, A; Silva Do Amaral, S M; Sznajder, A; Fernandez Perez Tomei, T R; Ferreira Dias, M A; Gregores, E M; Novaes, S F; Abadjiev, K; Anguelov, T; Damgov, J; Darmenov, N; Dimitrov, L; Genchev, V; Iaydjiev, P; Piperov, S; Stoykova, S; Sultanov, G; Trayanov, R; Vankov, I; Dimitrov, A; Dyulendarova, M; Kozhuharov, V; Litov, L; Marinova, E; Mateev, M; Pavlov, B; Petkov, P; Toteva, Z; Chen, G M; Chen, H S; Guan, W; Jiang, C H; Liang, D; Liu, B; Meng, X; Tao, J; Wang, J; Wang, Z; Xue, Z; Zhang, Z; Ban, Y; Cai, J; Ge, Y; Guo, S; Hu, Z; Mao, Y; Qian, S J; Teng, H; Zhu, B; Avila, C; Baquero Ruiz, M; Carrillo Montoya, C A; Gomez, A; Gomez Moreno, B; Ocampo Rios, A A; Osorio Oliveros, A F; Reyes Romero, D; Sanabria, J C; Godinovic, N; Lelas, K; Plestina, R; Polic, D; Puljak, I; Antunovic, Z; Dzelalija, M; Brigljevic, V; Duric, S; Kadija, K; Morovic, S; Fereos, R; Galanti, M; Mousa, J; Papadakis, A; Ptochos, F; Razis, P A; Tsiakkouri, D; Zinonos, Z; Hektor, A; Kadastik, M; Kannike, K; Müntel, M; Raidal, M; Rebane, L; Anttila, E; Czellar, S; Härkönen, J; Heikkinen, A; Karimäki, V; Kinnunen, R; Klem, J; Kortelainen, M J; Lampén, T; Lassila-Perini, K; Lehti, S; Lindén, T; Luukka, P; Mäenpää, T; Nysten, J; Tuominen, E; Tuominiemi, J; Ungaro, D; Wendland, L; Banzuzi, K; Korpela, A; Tuuva, T; Nedelec, P; Sillou, D; Besancon, M; Chipaux, R; Dejardin, M; Denegri, D; Descamps, J; Fabbro, B; Faure, J L; Ferri, F; Ganjour, S; Gentit, F X; Givernaud, A; Gras, P; Hamel de Monchenault, G; Jarry, P; Lemaire, M C; Locci, E; Malcles, J; Marionneau, M; Millischer, L; Rander, J; Rosowsky, A; Rousseau, D; Titov, M; Verrecchia, P; Baffioni, S; Bianchini, L; Bluj, M; Busson, P; Charlot, C; Dobrzynski, L; Granier de Cassagnac, R; Haguenauer, M; Miné, P; Paganini, P; Sirois, Y; Thiebaux, C; Zabi, A; Agram, J L; Besson, A; Bloch, D; Bodin, D; Brom, J M; Conte, E; Drouhin, F; Fontaine, J C; Gelé, D; Goerlach, U; Gross, L; Juillot, P; Le Bihan, A C; Patois, Y; Speck, J; Van Hove, P; Baty, C; Bedjidian, M; Blaha, J; Boudoul, G; Brun, H; Chanon, N; Chierici, R; Contardo, D; Depasse, P; Dupasquier, T; El Mamouni, H; Fassi, F; Fay, J; Gascon, S; Ille, B; Kurca, T; Le Grand, T; Lethuillier, M; Lumb, N; Mirabito, L; Perries, S; Vander Donckt, M; Verdier, P; Djaoshvili, N; Roinishvili, N; Roinishvili, V; Amaglobeli, N; Adolphi, R; Anagnostou, G; Brauer, R; Braunschweig, W; Edelhoff, M; Esser, H; Feld, L; Karpinski, W; Khomich, A; Klein, K; Mohr, N; Ostaptchouk, A; Pandoulas, D; Pierschel, G; Raupach, F; Schael, S; Schultz von Dratzig, A; Schwering, G; Sprenger, D; Thomas, M; Weber, M; Wittmer, B; Wlochal, M; Actis, O; Altenhöfer, G; Bender, W; Biallass, P; Erdmann, M; Fetchenhauer, G; Frangenheim, J; Hebbeker, T; Hilgers, G; Hinzmann, A; Hoepfner, K; Hof, C; Kirsch, M; Klimkovich, T; Kreuzer, P; Lanske, D; Merschmeyer, M; Meyer, A; Philipps, B; Pieta, H; Reithler, H; Schmitz, S A; Sonnenschein, L; Sowa, M; Steggemann, J; Szczesny, H; Teyssier, D; Zeidler, C; Bontenackels, M; Davids, M; Duda, M; Flügge, G; Geenen, H; Giffels, M; Haj Ahmad, W; Hermanns, T; Heydhausen, D; Kalinin, S; Kress, T; Linn, A; Nowack, A; Perchalla, L; Poettgens, M; Pooth, O; Sauerland, P; Stahl, A; Tornier, D; Zoeller, M H; Aldaya Martin, M; Behrens, U; Borras, K; Campbell, A; Castro, E; Dammann, D; Eckerlin, G; Flossdorf, A; Flucke, G; Geiser, A; Hatton, D; Hauk, J; Jung, H; Kasemann, M; Katkov, I; Kleinwort, C; Kluge, H; Knutsson, A; Kuznetsova, E; Lange, W; Lohmann, W; Mankel, R; Marienfeld, M; Meyer, A B; Miglioranzi, S; Mnich, J; Ohlerich, M; Olzem, J; Parenti, A; Rosemann, C; Schmidt, R; Schoerner-Sadenius, T; Volyanskyy, D; Wissing, C; Zeuner, W D; Autermann, C; Bechtel, F; Draeger, J; Eckstein, D; Gebbert, U; Kaschube, K; Kaussen, G; Klanner, R; Mura, B; Naumann-Emme, S; Nowak, F; Pein, U; Sander, C; Schleper, P; Schum, T; Stadie, H; Steinbrück, G; Thomsen, J; Wolf, R; Bauer, J; Blüm, P; Buege, V; Cakir, A; Chwalek, T; De Boer, W; Dierlamm, A; Dirkes, G; Feindt, M; Felzmann, U; Frey, M; Furgeri, A; Gruschke, J; Hackstein, C; Hartmann, F; Heier, S; Heinrich, M; Held, H; Hirschbuehl, D; Hoffmann, K H; Honc, S; Jung, C; Kuhr, T; Liamsuwan, T; Martschei, D; Mueller, S; Müller, Th; Neuland, M B; Niegel, M; Oberst, O; Oehler, A; Ott, J; Peiffer, T; Piparo, D; Quast, G; Rabbertz, K; Ratnikov, F; Ratnikova, N; Renz, M; Saout, C; Sartisohn, G; Scheurer, A; Schieferdecker, P; Schilling, F P; Schott, G; Simonis, H J; Stober, F M; Sturm, P; Troendle, D; Trunov, A; Wagner, W; Wagner-Kuhr, J; Zeise, M; Zhukov, V; Ziebarth, E B; Daskalakis, G; Geralis, T; Karafasoulis, K; Kyriakis, A; Loukas, D; Markou, A; Markou, C; Mavrommatis, C; Petrakou, E; Zachariadou, A; Gouskos, L; Katsas, P; Panagiotou, A; Evangelou, I; Kokkas, P; Manthos, N; Papadopoulos, I; Patras, V; Triantis, F A; Bencze, G; Boldizsar, L; Debreczeni, G; Hajdu, C; Hernath, S; Hidas, P; Horvath, D; Krajczar, K; Laszlo, A; Patay, G; Sikler, F; Toth, N; Vesztergombi, G; Beni, N; Christian, G; Imrek, J; Molnar, J; Novak, D; Palinkas, J; Szekely, G; Szillasi, Z; Tokesi, K; Veszpremi, V; Kapusi, A; Marian, G; Raics, P; Szabo, Z; Trocsanyi, Z L; Ujvari, B; Zilizi, G; Bansal, S; Bawa, H S; Beri, S B; Bhatnagar, V; Jindal, M; Kaur, M; Kaur, R; Kohli, J M; Mehta, M Z; Nishu, N; Saini, L K; Sharma, A; Singh, A; Singh, J B; Singh, S P; Ahuja, S; Arora, S; Bhattacharya, S; Chauhan, S; Choudhary, B C; Gupta, P; Jain, S; Jha, M; Kumar, A; Ranjan, K; Shivpuri, R K; Srivastava, A K; Choudhury, R K; Dutta, D; Kailas, S; Kataria, S K; Mohanty, A K; Pant, L M; Shukla, P; Topkar, A; Aziz, T; Guchait, M; Gurtu, A; Maity, M; Majumder, D; Majumder, G; Mazumdar, K; Nayak, A; Saha, A; Sudhakar, K; Banerjee, S; Dugad, S; Mondal, N K; Arfaei, H; Bakhshiansohi, H; Fahim, A; Jafari, A; Mohammadi Najafabadi, M; Moshaii, A; Paktinat Mehdiabadi, S; Rouhani, S; Safarzadeh, B; Zeinali, M; Felcini, M; Abbrescia, M; Barbone, L; Chiumarulo, F; Clemente, A; Colaleo, A; Creanza, D; Cuscela, G; De Filippis, N; De Palma, M; De Robertis, G; Donvito, G; Fedele, F; Fiore, L; Franco, M; Iaselli, G; Lacalamita, N; Loddo, F; Lusito, L; Maggi, G; Maggi, M; Manna, N; Marangelli, B; My, S; Natali, S; Nuzzo, S; Papagni, G; Piccolomo, S; Pierro, G A; 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    2010-01-01

    This paper describes the calibration procedure for the drift tubes of the CMS barrel muon system and reports the main results obtained with data collected during a high statistics cosmic ray data-taking period. The main goal of the calibration is to determine, for each drift cell, the minimum time delay for signals relative to the trigger, accounting for the drift velocity within the cell. The accuracy of the calibration procedure is influenced by the random arrival time of cosmic muons. A more refined analysis of the drift velocity was performed during the offline reconstruction phase, which takes into account this feature of cosmic ray events.

  4. Calibration of the CMS Drift Tube Chambers and Measurement of the Drift Velocity with Cosmic Rays

    CERN Document Server

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Wigmans, R; Yazgan, E; Engh, D; Florez, C; Johns, W; Pathak, S; Sheldon, P; Andelin, D; Arenton, M W; Balazs, M; Boutle, S; Buehler, M; Conetti, S; Cox, B; Hirosky, R; Ledovskoy, A; Neu, C; Phillips II, D; Ronquest, M; Yohay, R; Gollapinni, S; Gunthoti, K; Harr, R; Karchin, P E; Mattson, M; Sakharov, A; Anderson, M; Bachtis, M; Bellinger, J N; Carlsmith, D; Crotty, I; Dasu, S; Dutta, S; Efron, J; Feyzi, F; Flood, K; Gray, L; Grogg, K S; Grothe, M; Hall-Wilton, R; Jaworski, M; Klabbers, P; Klukas, J; Lanaro, A; Lazaridis, C; Leonard, J; Loveless, R; Magrans de Abril, M; Mohapatra, A; Ott, G; Polese, G; Reeder, D; Savin, A; Smith, W H; Sourkov, A; Swanson, J; Weinberg, M; Wenman, D; Wensveen, M; White, A

    2010-01-01

    This paper describes the calibration procedure for the drift tubes of the CMS barrel muon system and reports the main results obtained with data collected during a high statistics cosmic ray data-taking period. The main goal of the calibration is to determine, for each drift cell, the minimum time delay for signals relative to the trigger, accounting for the drift velocity within the cell. The accuracy of the calibration procedure is influenced by the random arrival time of cosmic muons. A more refined analysis of the drift velocity was performed during the offline reconstruction phase, which takes into account this feature of cosmic ray events.

  5. ACS/WFC Pixel Stability - Bringing the Pixels Back to the Science

    Science.gov (United States)

    Borncamp, David; Grogin, Norman A.; Bourque, Matthew; Ogaz, Sara

    2016-06-01

    Electrical current that has been trapped within the lattice structure of a Charged Coupled Device (CCD) can be present through multiple exposures, which will have an adverse effect on its science performance. The traditional way to correct for this extra charge is to take an image with the camera shutter closed periodically throughout the lifetime of the instrument. These images, generally referred to as dark images, allow for the characterization of the extra charge that is trapped within the CCD at the time of observation. This extra current can then be subtracted out of science images to correct for the extra charge that was there at this time. Pixels that have a charge above a certain threshold of current are marked as “hot” and flagged in the data quality array. However, these pixels may not be "bad" in the traditional sense that they cannot be reliably dark-subtracted. If these pixels are shown to be stable over an anneal period, the charge can be properly subtracted and the extra noise from this dark current can be taken into account. We present the results of a pixel history study that analyzes every pixel of ACS/WFC individually and allows pixels that were marked as bad to be brought back into the science image.

  6. Upgrade of ATLAS ITk Pixel Detector

    CERN Document Server

    Huegging, Fabian; The ATLAS collaboration

    2017-01-01

    The high luminosity upgrade of the LHC (HL-LHC) in 2026 will provide new challenges to the ATLAS tracker. The current inner detector will be replaced with an entirely-silicon inner tracker (ITk) which will consist of a five barrel layer Pixel detector surrounded by a four barrel layer Strip detector. The expected high radiation levels are requiring the development of upgraded silicon sensors as well as new a front-end chip. The dense tracking environment will require finer granularity detectors and low mass global and local support structures. The data rates will require new technologies for high bandwidth data transmission and handling. The current status of the ITk ATLAS Pixel detector developments as well as different layout options will be reviewed.

  7. Towards third generation pixel readout chips

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Sciveres, M., E-mail: mgarcia-sciveres@lbl.gov; Mekkaoui, A.; Ganani, D.

    2013-12-11

    We present concepts and prototyping results towards a third generation pixel readout chip. We consider the 130 nm feature size FE-I4 chip, in production for the ATLAS IBL upgrade, to be a second generation chip. A third generation chip would have to go significantly further. A possible direction is to make the IC design generic so that different experiments can configure it to meet significantly different requirements, without the need for everybody to develop their own ASIC from the ground up. In terms of target technology, a demonstrator 500-pixel matrix containing analog front ends only (no complex functionality), was designed and fabricated in 65 nm CMOS and irradiated with protons in December 2011 and May 2012.

  8. Noise in a CMOS digital pixel sensor

    Institute of Scientific and Technical Information of China (English)

    Zhang Chi; Yao Suying; Xu Jiangtao

    2011-01-01

    Based on the study of noise performance in CMOS digital pixel sensor (DPS),a mathematical model of noise is established with the pulse-width-modulation (PWM) principle.Compared with traditional CMOS image sensors,the integration time is different and A/D conversion is implemented in each PWM DPS pixel.Then,the quantitative calculating formula of system noise is derived.It is found that dark current shot noise is the dominant noise source in low light region while photodiode shot noise becomes significantly important in the bright region.In this model,photodiode shot noise does not vary with luminance,but dark current shot noise does.According to increasing photodiode capacitance and the comparator's reference voltage or optimizing the mismatch in the comparator,the total noise can be reduced.These results serve as a guideline for the design of PWM DPS.

  9. ATLAS Pixel IBL: Stave Quality Assurance

    CERN Document Server

    The ATLAS collaboration

    2014-01-01

    For Run 2 of the LHC a fourth innermost Pixel Detector layer on a smaller radius beam pipe has been installed in the ATLAS Detector to add redundancy against radiation damage of the current Pixel Detector and to ensure a high quality tracking and b-tagging performance of the Inner Detector over the coming years until the High Luminosity Upgrade. State of the art components have been produced and assembled onto support structures known as staves over the last two years. In total, 20 staves have been built and qualified in a designated Quality Assurance setup at CERN of which 14 have been integrated onto the beam pipe. Results from the testing are presented.

  10. Concentrated Hitting Times of Randomized Search Heuristics with Variable Drift

    DEFF Research Database (Denmark)

    Lehre, Per Kristian; Witt, Carsten

    2014-01-01

    these results handle a position-dependent (variable) drift that was not covered by previous drift theorems with tail bounds. Moreover, our theorem can be specialized into virtually all existing drift theorems with drift towards the target from the literature. Finally, user-friendly specializations...

  11. Pixel Dynamics Analysis of Photospheric Spectral Data

    Science.gov (United States)

    2014-11-13

    corresponding Doppler blueshift (redshift) integrated over the pixel. Variations in the line width δλm may indicate variations in temperature or changes in...skewness of their absorption line redshift/ blueshift and asymmetry PFDs, as well as by the spatial average for each region. These three time-varying... blueshift PFD variance and skewness plots). These oscillations, associated with the AR regions exhibiting solar eruptions, occur with a period of ∼ 10

  12. Efficient segmentation by sparse pixel classification

    DEFF Research Database (Denmark)

    Dam, Erik B; Loog, Marco

    2008-01-01

    Segmentation methods based on pixel classification are powerful but often slow. We introduce two general algorithms, based on sparse classification, for optimizing the computation while still obtaining accurate segmentations. The computational costs of the algorithms are derived......, and they are demonstrated on real 3-D magnetic resonance imaging and 2-D radiograph data. We show that each algorithm is optimal for specific tasks, and that both algorithms allow a speedup of one or more orders of magnitude on typical segmentation tasks....

  13. Electrical Characteristics of Silicon Pixel Sensors

    CERN Document Server

    Gorelov, I; Hoeferkamp, M; Mata-Bruni, V; Santistevan, G; Seidel, S C; Ciocio, A; Einsweiler, K F; Emes, J; Gilchriese, M G D; Joshi, A; Kleinfelder, S A; Marchesini, R; McCormack, F; Milgrome, O; Palaio, N; Pengg, F; Richardson, J; Zizka, G; Ackers, M; Comes, G; Fischer, P; Keil, M; Klasen, V; Kühl, T; Meuser, S; Ockenfels, W; Raith, B; Treis, J; Wermes, N; Gössling, C; Hügging, F G; Klaiber Lodewigs, Jonas M; Krasel, O; Wüstenfeld, J; Wunstorf, R; Barberis, D; Beccherle, R; Caso, Carlo; Cervetto, M; Darbo, G; Gagliardi, G; Gemme, C; Morettini, P; Netchaeva, P; Osculati, B; Rossi, L; Charles, E; Fasching, D; Blanquart, L; Breugnon, P; Calvet, D; Clemens, J-C; Delpierre, P A; Hallewell, G D; Laugier, D; Mouthuy, T; Rozanov, A; Valin, I; Andreazza, A; Caccia, M; Citterio, M; Lari, T; Meroni, C; Ragusa, F; Troncon, C; Vegni, G; Lutz, Gerhard; Richter, R H; Rohe, T; Boyd, GR; Skubic, P L; Sícho, P; Tomasek, L; Vrba, V; Holder, M; Ziolkowski, M; Cauz, D; Cobal-Grassmann, M; D'Auria, S; De Lotto, B; del Papa, C; Grassmann, H; Santi, L; Becks, K H; Lenzen, G; Linder, C

    2001-01-01

    Prototype sensors for the ATLAS silicon pixel detector have been electrically characterized. The current and voltage characteristics, charge collection efficiencies, and resolutions have been examined. Devices were fabricated on oxygenated and standard detector-grade silicon wafers. Results from prototypes which examine p-stop and standard and moderated p-spray isolation are presented for a variety of geometrical options. Some of the comparisons relate unirradiated sensors with those that have received fluences relevant to LHC operation.

  14. Production chain of CMS pixel modules

    CERN Document Server

    2006-01-01

    The pictures show the production chain of pixel modules for the CMS detector. Fig.1: overview of the assembly procedure. Fig.2: bump bonding with ReadOut Chip (ROC) connected to the sensor. Fig.3: glueing a raw module onto the baseplate strips. Fig.4: glueing of the High Density Interconnect (HDI) onto a raw module. Fig.5: pull test after heat reflow. Fig.6: wafer sensor processing, Indium evaporation.

  15. Photovoltaic retinal prosthesis with high pixel density

    Science.gov (United States)

    Mathieson, Keith; Loudin, James; Goetz, Georges; Huie, Philip; Wang, Lele; Kamins, Theodore I.; Galambos, Ludwig; Smith, Richard; Harris, James S.; Sher, Alexander; Palanker, Daniel

    2012-06-01

    Retinal degenerative diseases lead to blindness due to loss of the `image capturing' photoreceptors, while neurons in the `image-processing' inner retinal layers are relatively well preserved. Electronic retinal prostheses seek to restore sight by electrically stimulating the surviving neurons. Most implants are powered through inductive coils, requiring complex surgical methods to implant the coil-decoder-cable-array systems that deliver energy to stimulating electrodes via intraocular cables. We present a photovoltaic subretinal prosthesis, in which silicon photodiodes in each pixel receive power and data directly through pulsed near-infrared illumination and electrically stimulate neurons. Stimulation is produced in normal and degenerate rat retinas, with pulse durations of 0.5-4 ms, and threshold peak irradiances of 0.2-10 mW mm-2, two orders of magnitude below the ocular safety limit. Neural responses were elicited by illuminating a single 70 µm bipolar pixel, demonstrating the possibility of a fully integrated photovoltaic retinal prosthesis with high pixel density.

  16. Radiation hardness studies of silicon pixel detectors

    CERN Document Server

    Lari, T

    2006-01-01

    At the LHC silicon vertex detectors will be exposed to hadron fluences of the order of . In order to study the effects of radiation damage on the performances of the ATLAS Pixel Vertex Detector, several full-size detector modules were irradiated to a fluence of and tested in a beam at CERN. After irradiation only a modest degradation of the detector performances is observed. At the operating ATLAS bias voltage of 600 V the average signal is still 80% of the pre-irradiation value, the spatial resolution is and the detection efficiency is 98.2%. The LHC luminosity upgrade will increase the radiation hardness requirements by a factor of 10 and will require the development of new ultra-radiation hard vertex detectors. A detailed simulation of silicon pixel detectors irradiated to very high fluence is presented and used to study the possibility to use silicon pixel detectors at the LHC after the luminosity upgrade. The charge collection properties and the detector response were computed for different silicon mater...

  17. Baryon Acoustic Oscillations reconstruction with pixels

    CERN Document Server

    Obuljen, Andrej; Castorina, Emanuele; Viel, Matteo

    2016-01-01

    Gravitational non-linear evolution induces a shift in the position of the baryon acoustic oscillations (BAO) peak together with a damping and broadening of its shape that bias and degrades the accuracy with which the position of the peak can be determined. BAO reconstruction is a technique developed to undo part of the effect of non-linearities. We present a new reconstruction method that consists in displacing pixels instead of galaxies and whose implementation is easier than the standard reconstruction method. We show that our method is equivalent to the standard reconstruction technique in the limit where the number of pixels becomes very large. This method is particularly useful in surveys where individual galaxies are not resolved, as in 21cm intensity mapping observations. We validate our method by reconstructing mock pixelated maps, that we build from the distribution of matter and halos in real- and redshift-space, from a large set of numerical simulations. We find that our method is able to decrease ...

  18. ATLAS ITk and new pixel sensors technologies

    CERN Document Server

    Gaudiello, A

    2016-01-01

    During the 2023–2024 shutdown, the Large Hadron Collider (LHC) will be upgraded to reach an instantaneous luminosity up to 7×10$^{34}$ cm$^{−2}$s$^{−1}$. This upgrade of the accelerator is called High-Luminosity LHC (HL-LHC). The ATLAS detector will be changed to meet the challenges of HL-LHC: an average of 200 pile-up events in every bunch crossing, and an integrated luminosity of 3000 fb $^{−1}$ over ten years. The HL-LHC luminosity conditions are too extreme for the current silicon (pixel and strip) detectors and straw tube transition radiation tracker (TRT) of the current ATLAS tracking system. Therefore the ATLAS inner tracker is being completely rebuilt for data-taking and the new system is called Inner Tracker (ITk). During this upgrade the TRT will be removed in favor of an all-new all-silicon tracker composed only by strip and pixel detectors. An overview of new layouts in study will be reported and the new pixel sensor technologies in development will be explained.

  19. Readout Architecture for Hybrid Pixel Readout Chips

    CERN Document Server

    AUTHOR|(SzGeCERN)694170; Westerlund, Tomi; Wyllie, Ken

    The original contribution of this thesis to knowledge are novel digital readout architectures for hybrid pixel readout chips. The thesis presents asynchronous bus-based architecture, a data-node based column architecture and a network-based pixel matrix architecture for data transportation. It is shown that the data-node architecture achieves readout efficiency 99 % with half the output rate as a bus-based system. The network-based solution avoids ``broken'' columns due to some manufacturing errors, and it distributes internal data traffic more evenly across the pixel matrix than column-based architectures. An improvement of $>$ 10 % to the efficiency is achieved with uniform and non-uniform hit occupancies. Architectural design has been done using transaction level modeling ($TLM$) and sequential high-level design techniques for reducing the design and simulation time. It has been possible to simulate tens of column and full chip architectures using the high-level techniques. A decrease of $>$ 10 in run-time...

  20. Characterization of the CMS Pixel Detectors

    CERN Document Server

    Gu, Weihua

    2002-01-01

    In 2005 the Large Hadron Collider (LHC) will start the pp collisions at a high luminosity and at a center of mass energy of 14 TeV. The primary goal of the experimental programme is the search of the Higgs boson(s) and the supersymmetric particles. The programme is also proposed to detect a range of diverse signatures in order to provide guidance for future physics. The pixel detector system makes up the innermost part of the CMS experiment, which is one of the two general purpose detectors at the LHC. The main tasks of the system are vertex detection and flavor tagging. The high luminosity and the high particle multiplicity as well as the small bunch spacing at the LHC impose great challenges on the pixel detectors: radiation hardness of sensors and electronics, fast signal processing and a high granularity are the essential requirements. This thesis concentrates on the study of the suitability of two test stands, which are implemented to characterize the CMS pixel detectors: one is con-cerned with test puls...

  1. Sky pixelization for the analysis of extended emission

    Science.gov (United States)

    Verkhodanov, O. V.; Doroshkevich, A. G.

    2013-08-01

    Spherical pixelization schemes are reviewed that allow analyzing extended emission and, in particular, the cosmic microwave background. Problems with implementing different schemes are considered. The nonhierarchical Gauss-Legendre sky pixelization (GLESP) approach is discussed in detail.

  2. Evaluation of a multistage CdZnTe Compton camera for prompt γ imaging for proton therapy

    Science.gov (United States)

    McCleskey, M.; Kaye, W.; Mackin, D. S.; Beddar, S.; He, Z.; Polf, J. C.

    2015-06-01

    A new detector system, Polaris J from H3D, has been evaluated for its potential application as a Compton camera (CC) imaging device for prompt γ rays (PGs) emitted during proton radiation therapy (RT) for the purpose of dose range verification. This detector system consists of four independent CdZnTe detector stages and a coincidence module, allowing the user to construct a Compton camera in different geometrical configurations and to accept both double and triple scatter events. Energy resolution for the 662 keV line from 137Cs was found to be 9.7 keV FWHM. The raw absolute efficiencies for double and triple scatter events were 2.2 ×10-5 and 5.8 ×10-7, respectively, for γs from a 60Co source. The position resolution for the reconstruction of a point source from the measured CC data was about 2 mm. Overall, due to the low efficiency of the Polaris J CC, the current system was deemed not viable for imaging PGs emitted during proton RT treatment delivery. However, using a validated Monte Carlo model of the CC, we found that by increasing the size of the detectors and placing them in a two stage configuration, the efficiency could be increased to a level to make PG imaging possible during proton RT.

  3. Novel ZnO:Al contacts to CdZnTe for X- and gamma-ray detectors.

    Science.gov (United States)

    Roy, U N; Mundle, R M; Camarda, G S; Cui, Y; Gul, R; Hossain, A; Yang, G; Pradhan, A K; James, R B

    2016-05-24

    CdZnTe (CZT) has made a significant impact as a material for room-temperature nuclear-radiation detectors due to its potential impact in applications related to nonproliferation, homeland security, medical imaging, and gamma-ray telescopes. In all such applications, common metals, such as gold, platinum and indium, have been used as electrodes for fabricating the detectors. Because of the large mismatch in the thermal-expansion coefficient between the metal contacts and CZT, the contacts can undergo stress and mechanical degradation, which is the main cause for device instability over the long term. Here, we report for the first time on our use of Al-doped ZnO as the preferred electrode for such detectors. The material was selected because of its better contact properties compared to those of the metals commonly used today. Comparisons were conducted for the detector properties using different contacts, and improvements in the performances of ZnO:Al-coated detectors are described in this paper. These studies show that Al:ZnO contacts to CZT radiation detectors offer the potential of becoming a transformative replacement for the common metallic contacts due to the dramatic improvements in the performance of detectors and improved long-term stability.

  4. Al-doped ZnO contact to CdZnTe for x- and gamma-ray detector applications

    Science.gov (United States)

    Roy, U. N.; Camarda, G. S.; Cui, Y.; Gul, R.; Hossain, A.; Yang, G.; Mundle, R. M.; Pradhan, A. K.; James, R. B.

    2016-06-01

    The poor adhesion of common metals to CdZnTe (CZT)/CdTe surfaces has been a long-standing challenge for radiation detector applications. In this present work, we explored the use of an alternative electrode, viz., Al-doped ZnO (AZO) as a replacement to common metallic contacts. ZnO offers several advantages over the latter, such as having a higher hardness, a close match of the coefficients of thermal expansion for CZT and ZnO, and better adhesion to the surface of CZT due to the contact layer being an oxide. The AZO/CZT contact was investigated via high spatial-resolution X-ray response mapping for a planar detector at the micron level. The durability of the device was investigated by acquiring I-V measurements over an 18-month period, and good long-term stability was observed. We have demonstrated that the AZO/CZT/AZO virtual-Frisch-grid device performs fairly well, with comparable or better characteristics than that for the same detector fabricated with gold contacts.

  5. A 12-bit 1 MS/s SAR-ADC for multi-channel CdZnTe detectors

    Science.gov (United States)

    Wei, Liu; Tingcun, Wei; Bo, Li; Panjie, Guo; Yongcai, Hu

    2015-04-01

    This paper presents a low power, area-efficient and radiation-hardened 12-bit 1 MS/s successive approximation register (SAR) analog-to-digital converter (ADC) for multi-channel CdZnTe (CZT) detector applications. In order to improve the SAR-ADC's accuracy, a novel comparator is proposed in which the offset voltage is self-calibrated and also a new architecture for the unit capacitor array is proposed to reduce the capacitance mismatches in the charge-redistribution DAC. The ability to radiation-harden the SAR-ADC is enhanced through circuit and layout design technologies. The prototype chip was fabricated using a TSMC 0.35 μm 2P4M CMOS process. At a 3.3/5 V power supply and a sampling rate of 1 MS/s, the proposed SAR-ADC achieves a peak signal to noise and distortion ratio (SINAD) of 67.64 dB and consumes only 10 mW power. The core of the prototype chip occupies an active area of 1180 × 1080 μm2. Project supported by the Special-Funded Program on National Key Scientific Instruments and Equipment Development (No. 2011YQ040082).

  6. Effect of de-trapping on carrier transport process in semi-insulating CdZnTe

    Science.gov (United States)

    Guo, Rong-Rong; Jie, Wan-Qi; Zha, Gang-Qiang; Xu, Ya-Dong; Feng, Tao; Wang, Tao; Du, Zhuo-Tong

    2015-06-01

    The effect of de-trapping on the carrier transport process in the CdZnTe detector is studied by laser beam-induced transient current (LBIC) measurement. Trapping time, de-trapping time, and mobility for electrons are determined directly from transient waveforms under various bias voltages. The results suggest that an electric field strengthens the capture and emission effects in trap center, which is associated with field-assisted capture and the Poole-Frenkel effect, respectively. The electron mobility is calculated to be 950 cm2/V·s and the corresponding electron mobility-lifetime product is found to be 1.32×10-3 cm2/V by a modified Hecht equation with considering the surface recombination effect. It is concluded that the trapping time and de-trapping time obtained from LBIC measurement provide direct information concerning the transport process. Project supported by the National Instrumentation Program, China (Grant No. 2011YQ040082), the National Natural Science Foundation of China (Grant Nos. 61274081, 51372205, and 51202197), the National 973 Project of China (Grant No. 2011CB610400), the China Postdoctoral Science Foundation (Grant No. 2014M550509), and the 111 Project of China (Grant No. B08040).

  7. A PFM based digital pixel with off-pixel residue measurement for 15μm pitch MWIR FPAs

    Science.gov (United States)

    Abbasi, Shahbaz; Shafique, Atia; Galioglu, Arman; Ceylan, Omer; Yazici, Melik; Gurbuz, Yasar

    2016-05-01

    Digital pixels based on pulse frequency modulation (PFM) employ counting techniques to achieve very high charge handling capability compared to their analog counterparts. Moreover, extended counting methods making use of leftover charge (residue) on the integration capacitor help improve the noise performance of these pixels. However, medium wave infrared (MWIR) focal plane arrays (FPAs) having smaller pixel pitch are constrained in terms of pixel area which makes it difficult to add extended counting circuitry to the pixel. Thus, this paper investigates the performance of digital pixels employing off-pixel residue measurement. A circuit prototype of such a pixel has been designed for 15μm pixel pitch and fabricated in 90nm CMOS. The prototype is composed of a pixel front-end based on a PFM loop. The frontend is a modified version of conventional design providing a means for buffering the signal that needs to be converted to a digital value by an off-pixel ADC. The pixel has an integration phase and a residue measurement phase. Measured integration performance of the pixel has been reported in this paper for various detector currents and integration times.

  8. PIXELS: Using field-based learning to investigate students' concepts of pixels and sense of scale

    Science.gov (United States)

    Pope, A.; Tinigin, L.; Petcovic, H. L.; Ormand, C. J.; LaDue, N.

    2015-12-01

    Empirical work over the past decade supports the notion that a high level of spatial thinking skill is critical to success in the geosciences. Spatial thinking incorporates a host of sub-skills such as mentally rotating an object, imagining the inside of a 3D object based on outside patterns, unfolding a landscape, and disembedding critical patterns from background noise. In this study, we focus on sense of scale, which refers to how an individual quantified space, and is thought to develop through kinesthetic experiences. Remote sensing data are increasingly being used for wide-reaching and high impact research. A sense of scale is critical to many areas of the geosciences, including understanding and interpreting remotely sensed imagery. In this exploratory study, students (N=17) attending the Juneau Icefield Research Program participated in a 3-hour exercise designed to study how a field-based activity might impact their sense of scale and their conceptions of pixels in remotely sensed imagery. Prior to the activity, students had an introductory remote sensing lecture and completed the Sense of Scale inventory. Students walked and/or skied the perimeter of several pixel types, including a 1 m square (representing a WorldView sensor's pixel), a 30 m square (a Landsat pixel) and a 500 m square (a MODIS pixel). The group took reflectance measurements using a field radiometer as they physically traced out the pixel. The exercise was repeated in two different areas, one with homogenous reflectance, and another with heterogeneous reflectance. After the exercise, students again completed the Sense of Scale instrument and a demographic survey. This presentation will share the effects and efficacy of the field-based intervention to teach remote sensing concepts and to investigate potential relationships between students' concepts of pixels and sense of scale.

  9. 4T CMOS Active Pixel Sensors under Ionizing Radiation

    NARCIS (Netherlands)

    Tan, J.

    2013-01-01

    This thesis investigates the ionizing radiation effects on 4T pixels and the elementary in-pixel test devices with regard to the electrical performance and the optical performance. In addition to an analysis of the macroscopic pixel parameter degradation, the radiation-induced degradation mechanisms

  10. Study of CdTe:Cl and CdZnTe detectors for medical multi-slices X-ray Computed Tomography; Etude de detecteurs en CdTe:Cl et CdZnTe pour la tomographie X medicale multicoupes

    Energy Technology Data Exchange (ETDEWEB)

    Ricq, St

    1999-09-28

    The application of CdTe and CdZnTe detectors to medical X-ray Computed Tomography have been investigated. Different electrodes (Au, Pt, In) have been deposited on CdZnTe HPBM and on CdTe:ClTHM. Their injection properties have been determined with Current-Voltage characteristics. Under X-ray in CT conditions, injection currents measurements reveal trapped carriers space-charges formation. The same way, the comparisons of the responses to X-beam cut-off with various injection possibilities enable to follow the space-charges evolutions and then to determine the predominant traps types. Nevertheless, both hole and electron traps are responsible for the memory effect e.g. the currents levels dependence with irradiation history. This effect is noticed in particular on responses to fast flux variations that simulate scanner's conditions. Trap levels probably corresponding to native defects are responsible for these limitations. In order to make such detectors suitable for X-ray Computed Tomography, significant progresses in CdTe for CdZnTe crystal growth with an important defects densities reduction (factor 10), or possibly counting mode operation, seem necessary. (author)

  11. Electron drift velocities in fast Argon and CF4 based drift gases

    CERN Document Server

    van Apeldoorn, G

    1998-01-01

    98-063 Electron drift velocities in gas mixtures were measured in a tabletop experiment using a nitrogen laser to create the primary electrons. The maximum drift times for electrons in a 5 mm (10 mm) honeycomb drift cell at 2200 V anode voltage were 28 ns (53 ns) and 21 ns (61 ns) for Ar-Cf4-CH4 (75/18/6) and Ar-CF4-CO2 (68/27/5), respectively. Changing the ratio of the latter mix did not change the drift velocity very much. The gains of the gases are ~10^4 for a single primary electron. CF4 causes electron attachment. The measured drift times agree well with GARFIELD simulations.

  12. ACS/WFC Pixel History, Bringing the Pixels Back to Science

    Science.gov (United States)

    Borncamp, David; Grogin, Norman; Bourque, Matthew; Ogaz, Sara

    2017-06-01

    Excess thermal energy within a Charged Coupled Device (CCD) results in excess electrical current that is trapped within the lattice structure of the electronics. This excess signal from the CCD itself can be present through multiple exposures, which will have an adverse effect on its science performance unless it is corrected for. The traditional way to correct for this extra charge is to take occasional long-exposure images with the camera shutter closed. These images, generally referred to as ``dark'' images, allow for the measurement of thermal-electron contamination at each pixel of the CCD. This so-called ``dark current'' can then be subtracted from the science images by re-scaling to the science exposure times. Pixels that have signal above a certain value are traditionally marked as ``hot'' and flagged in the data quality array. Many users will discard these pixels as being bad. However, these pixels may not be bad in the sense that they cannot be reliably dark-subtracted; if these pixels are shown to be stable over a given anneal period, the charge can be properly subtracted and the extra Poisson noise from this dark current can be taken into account and put into the error arrays.

  13. Thermal conductivity studies of CdZnTe with varying Te excess

    Science.gov (United States)

    Jackson, Maxx; Bennett, Brittany; Giltnane, Dustin; Babalola, Stephen; Ohmes, Martin F.; Stowe, A. C.

    2016-09-01

    Cadmium Zine Telluride (CZT) has been extensively studied as a room temperature semiconductor gamma radiation detector. CZT continues to show promise as a bulk and pixelated gamma spectrometer with less than one percent energy resolution; however the fabrication costs are high. Improved yields of high quality, large CZT spectroscopy grade crystals must be achieved. CZT is grown by the Traveling Heater Method (THM) with a Te overpressure to account for vaporization losses. This procedure creates Te rich zones. During growth, boules will often cleave limiting the number of harvestable crystals. As a result, crystal growth parameter optimization was evaluated by modeling the heat flow within the system. Interestingly, Cadmium Telluride (CdTe) is used as a thermal conductivity surrogate in the absence of a thorough study of the CZT thermal properties. The current study has measured the thermal conductivity of CZT pressed powders with varying Te concentrations from 50-100% over 25-800°C to understand the variation in this parameter from CdTe. Cd0.9Zn0.1Te1.0 is the base CZT (designated 50%). CZT exhibits a thermal conductivity of nearly 1 W/mK, an order of magnitude greater than CdTe. Further, the thermal conductivity decreased with increasing Te concentration.

  14. The KLOE drift chamber VCI 2001

    Energy Technology Data Exchange (ETDEWEB)

    Adinolfi, M.; Aloisio, A.; Ambrosino, F.; Andryakov, A.; Antonelli, A.; Antonelli, M.; Anulli, F.; Bacci, C.; Bankamp, A.; Barbiellini, G.; Bellini, F.; Bencivenni, G.; Bertolucci, S.; Bini, C.; Bloise, C.; Bocci, V.; Bossi, F.; Branchini, P.; Bulychjov, S.A.; Cabibbo, G.; Calcaterra, A.; Caloi, R.; Campana, P.; Capon, G.; Carboni, G.; Cardini, A.; Casarsa, M.; Cataldi, G.; Ceradini, F.; Cervell, F.; Cevenini, F.; Chiefari, G.; Ciambrone, P.; Conetti, S.; Conticelli, S.; De Lucia, E. E-mail: erika.delucia@roma1.infn.it; De Robertis, G.; De Sangro, R.; De Simone, P.; De Zorzi, G.; Dell' Agnello, S.; Denig, A.; Di Domenico, A.; Di Donato, C.; Di Falco, S.; Doria, A.; Drago, E.; Elia, V.; Erriquez, O.; Farilla, A.; Felici, G.; Ferrari, A.; Ferrer, M.L.; Finocchiaro, G.; Forti, C.; Franceschi, A.; Franzini, P.; Gao, M.L.; Gatti, C.; Gauzzi, P.; Giovannella, S.; Golovatyuk, V.; Gorini, E.; Grancagnolo, F.; Grandegger, W.; Graziani, E.; Guarnaccia, P.; Hagel, U. von.; Han, H.G.; Han, S.W.; Huang, X.; Incagli, M.; Ingrosso, L.; Jang, Y.Y.; Kim, W.; Kluge, W.; Kulikov, V.; Lacava, F.; Lanfranchi, G.; Lee-Franzini, J.; Lomtadze, F.; Luisi, C.; Mao, C.S.; Martemianov, M.; Matsyuk, M.; Mei, W.; Merola, L.; Messi, R.; Miscetti, S.; Moalem, A.; Moccia, S.; Moulson, M.; Mueller, S.; Murtas, F.; Napolitano, M.; Nedosekin, A.; Panareo, M.; Pacciani, L.; Pages, P.; Palutan, M.; Paoluzi, L.; Pasqualucci, E.; Passalacqua, L.; Passaseo, M.; Passeri, A.; Patera, V.; Petrolo, E.; Petrucci, G.; Picca, D.; Pirozzi, G.; Pistillo, C.; Pollack, M.; Pontecorvo, L.; Primavera, M.; Ruggieri, F.; Santangelo, P.; Santovetti, E.; Saracino, G.; Schamberger, R.D.; Schwick, C.; Sciascia, B.; Sciubba, A.; Scuri, F.; Sfiligoi, I.; Shan, J.; Silano, P.; Spadaro, T.; Spagnolo, S.; Spiriti, E.; Stanescu, C.; Tong, G.L.; Tortora, L.; Valente, E.; Valente, P.; Valeriani, B.; Venanzoni, G.; Veneziano, S.; Wu, Y.; Xie, Y.G.; Zhao, P.P.; Zhou, Y

    2002-02-01

    The main goal of the KLOE experiment at the Frascati DAPHINE phi-factory is the study CP violation in kaon decays. The tracking device of the experiment is a drift chamber whose dimensions, 4 m of diameter and 3.3 m length, provide a large acceptance volume for the decay products of low momentum K{sub L} ({lambda}{sub L}=3.4 m). A complete stereo geometry with 12.582 cells arranged in 58 layers guarantees a high and uniform efficiency in the reconstruction of the charged K{sub L} decays. Very light materials have been chosen both for the drift medium, a helium-based gas mixture, and for the mechanical structure, made of carbon fiber, to minimize multiple scattering and conversion of low-energy photons. The design requirements, the adopted solutions together with the calibration procedure and the tracking performances of the drift chamber are discussed.

  15. Epigenetic drift, epigenetic clocks and cancer risk.

    Science.gov (United States)

    Zheng, Shijie C; Widschwendter, Martin; Teschendorff, Andrew E

    2016-05-01

    It is well-established that the DNA methylation landscape of normal cells undergoes a gradual modification with age, termed as 'epigenetic drift'. Here, we review the current state of knowledge of epigenetic drift and its potential role in cancer etiology. We propose a new terminology to help distinguish the different components of epigenetic drift, with the aim of clarifying the role of the epigenetic clock, mitotic clocks and active changes, which accumulate in response to environmental disease risk factors. We further highlight the growing evidence that epigenetic changes associated with cancer risk factors may play an important causal role in cancer development, and that monitoring these molecular changes in normal cells may offer novel risk prediction and disease prevention strategies.

  16. The KLOE drift chamber VCI 2001

    CERN Document Server

    Adinolfi, M; Ambrosino, F; Andryakov, A; Antonelli, A; Antonelli, M; Anulli, F; Bacci, C; Bankamp, A; Barbiellini, G; Bellini, F; Bencivenni, G; Bertolucci, Sergio; Bini, C; Bloise, C; Bocci, V; Bossi, F; Branchini, P; Bulychjov, S A; Cabibbo, G; Calcaterra, A; Caloi, R; Campana, P; Capon, G; Carboni, G; Cardini, A; Casarsa, M; Cataldi, G; Ceradini, F; Cervell, F; Cevenini, F; Chiefari, G; Ciambrone, P; Conetti, S; Conticelli, S; De Lucia, E; De Robertis, G; De Simone, P; De Zorzi, G; De Sangro, R; Dell'Agnello, S; Denig, A; Di Domenico, A; Di Donato, C; Di Falco, S; Doria, A; Drago, E; Elia, V; Erriquez, O; Farilla, A; Felici, G; Ferrari, A; Ferrer, M L; Finocchiaro, G; Forti, C; Franceschi, A; Franzini, P; Gao, M L; Gatti, C; Gauzzi, P; Giovannella, S; Golovatyuk, V; Gorini, E; Grancagnolo, F; Grandegger, W; Graziani, E; Guarnaccia, P; Han, H G; Han, S W; Huang, X; Incagli, M; Ingrosso, L; Jang, Y Y; Kim, W; Kluge, W; Kulikov, V; Lacava, F; Lanfranchi, G; Lee-Franzini, J; Lomtadze, F; Luisi, C; Mao Chen Sheng; Martemyanov, M; Matsyuk, M; Mei, W; Merola, L; Messi, R; Miscetti, S; Moalem, A; Moccia, S; Moulson, M; Murtas, F; Müller, S; Napolitano, M; Nedosekin, A; Pacciani, L; Pagès, P; Palutan, M; Panareo, M; Paoluzi, L; Pasqualucci, E; Passalacqua, L; Passaseo, M; Passeri, A; Patera, V; Petrolo, E; Petrucci, Guido; Picca, D; Pirozzi, G; Pistillo, C; Pollack, M; Pontecorvo, L; Primavera, M; Ruggieri, F; Santangelo, P; Santovetti, E; Saracino, G; Schamberger, R D; Schwick, C; Sciascia, B; Sciubba, A; Scuri, F; Sfiligoi, I; Shan, J; Silano, P; Spadaro, T; Spagnolo, S; Spiriti, E; Stanescu, C; Tong, G L; Tortora, L; Valente, E; Valente, P; Valeriani, B; Venanzoni, G; Veneziano, Stefano; Von Hagel, U; Wu, Y; Xie, Y G; Zhao, P P; Zhou, Y

    2002-01-01

    The main goal of the KLOE experiment at the Frascati DAPHINE phi-factory is the study CP violation in kaon decays. The tracking device of the experiment is a drift chamber whose dimensions, 4 m of diameter and 3.3 m length, provide a large acceptance volume for the decay products of low momentum K sub L (lambda sub L =3.4 m). A complete stereo geometry with 12.582 cells arranged in 58 layers guarantees a high and uniform efficiency in the reconstruction of the charged K sub L decays. Very light materials have been chosen both for the drift medium, a helium-based gas mixture, and for the mechanical structure, made of carbon fiber, to minimize multiple scattering and conversion of low-energy photons. The design requirements, the adopted solutions together with the calibration procedure and the tracking performances of the drift chamber are discussed.

  17. Fabrication and Test of Pixelated CZT Detectors with Different Pixel Pitches and Thicknesses

    CERN Document Server

    Li, Q; Dowkontt, P; Martín, J; Beilicke, M; Jung, I; Groza, M; Bürger, A; De Geronimo, G; Krawczynski, H

    2008-01-01

    The main methods grown Cadmium Zinc Telluride (CZT) crystals with high yield and excellent homogeneity are Modified Horizontal Bridgman (MHB) and High Pressure Bridgman (HPB) processes, respectively. In this contribution, the readout system based on two 32-channel NCI-ASICs for pixellated CZT detector arrays has been developed and tested. The CZT detectors supplied by Orbotech (MHB) and eV products (HPB) are tested by NCI-ASIC readout system. The CZT detectors have an array of 8x8 or 11x11 pixel anodes fabricated on the anode surface with the area up to 2 cm x2 cm and the thickness of CZT detectors ranges from 0.5 cm to 1 cm. Energy spectra resolution and electron mobility-lifetime products of 8x8 pixels CZT detector with different thicknesses have been investigated.

  18. Caractérisation temporelle et spectrale de la photoluminescence de boîtes quantiques de CdZnTe

    Science.gov (United States)

    Brimont, C.; Cronenberger, S.; Crégut, O.; Gallart, M.; Hönerlage, B.; Gilliot, P.

    2006-10-01

    Nous étudions la relaxation des paires électron-trou dans des échantillons de boîtes quantiques auto-assemblées de CdZnTe riches en cadmium incluses dans un puits quantique riche en zinc. Dans ce type de système, le couplage électron-phonon LO est le principal mécanisme responsable de la relaxation d'énergie des porteurs. Nous mesurons cette relaxation par photoluminescence résolue en temps, en fonction de l'intensité et de l'énergie de photon de l'excitation.

  19. Fast Sub-Pixel Motion Estimation Algorithm For H.264

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A novel fast sub-pixel search algorithm is proposed to accelerate sub-pixel search. Based on the features of predicted motion vector (PMV) and texture direction observed, the proposed method effectively filters out impossible points and thus decreases 11 searched points in average during the sub-pixel search stage. A threshold is also adopted to early terminate the sub-pixel search. Simulation results show that the proposed method can achieve up to 4.8 times faster than full sub-pixel motion search scheme (FSPS) with less than 0.025 dB PSNR losses and 2.2% bitlength increases.

  20. A study in GUI aesthetics for modern pixel art games.

    OpenAIRE

    Grahn, Emma

    2013-01-01

    The clarity and usability of the graphical user interface is very important for the enjoyment of a digital game. Pixel art is an art style with low resolution consisting of a precise placing of pixels, the smallest unit of colour that a screen can display. Pixel art has the potential of being cheap, easy to make and nostalgic, but it takes some skill to handle. However the great weakness of pixel art is displaying letters, and small details with clarity. So is there a place for pixel art in m...

  1. Active Pixel Sensors in ams H18/H35 HV-CMOS Technology for the ATLAS HL-LHC Upgrade

    CERN Document Server

    Ristic, Branislav

    2016-01-01

    Deep sub micron HV-CMOS processes offer the opportunity for sensors built by industry standard techniques while being HV tolerant, making them good candidates for drift-based, fast collecting, thus radiation-hard pixel detectors. For the upgrade of the ATLAS Pixel Detector towards the HL-LHC requirements, active pixel sensors in HV-CMOS technology were investigated. These implement amplifier and discriminator stages directly in insulating deep n-wells, which also act as collecting electrodes. The deep n-wells allow for bias voltages up to 150V leading to a depletion depth of several 10um. Prototype sensors in the ams H18 180nm and H35 350nm HV-CMOS processes have been manufactured, acting as a potential drop-in replacement for the current ATLAS Pixel sensors, thus leaving higher level processing such as trigger handling to dedicated read-out chips. Sensors were thoroughly tested in lab measurements as well as in testbeam experiments. Irradiation with X-rays and protons revealed a tolerance to ionizing doses o...

  2. Dynamical pixel manipulation of metasurfaces (Conference Presentation)

    Science.gov (United States)

    Zhong, Jin-Qian

    2017-05-01

    Two-dimensional (2D) metamaterials or known as metasurfaces have attracted researchers' attention due to their capability to manipulate the amplitudes, phases and polarization states of incident electromagnetic waves by conferring extra phase different phase at different positions through a super cell that is composed of different oriented structures. In other words, metasurfaces can achieve beam steering and wave shaping by imparting local, gradient phase shift to the incoming waves. With these abilities, metasurfaces can be applied to applications such as ultrathin invisibility cloaks, metasurface holograms, planar lenses and a vortex generator. With the above mentioned advantages and applications of metasurfaces, yet, all the demonstrated metasurfaces possess a main insufficiency that once the metasurfaces are designed and fabricated, their optical properties are then fixed without any chance for further manipulation, which limits their versatility in practical applications. Moreover, although some researchers employed dynamically changeable materials to achieve an active metasurface, such manipulation can only change the overall performance such as an operating frequency instead of changing the provided phase on each pixel of a metasurface. To solve this issue, we employ liquid crystal integrated with a metasurface and the combination could be thus be dynamically tuned via electric bias on each pixel of liquid crystals. Through this setup, we can alter the polarization state of the incident electromagnetic wave dynamically and thus manipulate the extra phase provided by each pixel. In this combination, liquid crystal is employed to change the incident polarization from 0 to 360-degree and the metasurface is designed to achieve four different output signals including phase modulated linear- and circular-polarized light and amplitude-modulated linear- and circular-polarized light. Meanwhile, the metasurfaces could also control the transmission efficiency of the

  3. Optical Cloud Pixel Recovery via Machine Learning

    Directory of Open Access Journals (Sweden)

    Subrina Tahsin

    2017-05-01

    Full Text Available Remote sensing derived Normalized Difference Vegetation Index (NDVI is a widely used index to monitor vegetation and land use change. NDVI can be retrieved from publicly available data repositories of optical sensors such as Landsat, Moderate Resolution Imaging Spectro-radiometer (MODIS and several commercial satellites. Studies that are heavily dependent on optical sensors are subject to data loss due to cloud coverage. Specifically, cloud contamination is a hindrance to long-term environmental assessment when using information from satellite imagery retrieved from visible and infrared spectral ranges. Landsat has an ongoing high-resolution NDVI record starting from 1984. Unfortunately, this long time series NDVI data suffers from the cloud contamination issue. Though both simple and complex computational methods for data interpolation have been applied to recover cloudy data, all the techniques have limitations. In this paper, a novel Optical Cloud Pixel Recovery (OCPR method is proposed to repair cloudy pixels from the time-space-spectrum continuum using a Random Forest (RF trained and tested with multi-parameter hydrologic data. The RF-based OCPR model is compared with a linear regression model to demonstrate the capability of OCPR. A case study in Apalachicola Bay is presented to evaluate the performance of OCPR to repair cloudy NDVI reflectance. The RF-based OCPR method achieves a root mean squared error of 0.016 between predicted and observed NDVI reflectance values. The linear regression model achieves a root mean squared error of 0.126. Our findings suggest that the RF-based OCPR method is effective to repair cloudy pixels and provides continuous and quantitatively reliable imagery for long-term environmental analysis.

  4. Learning in the context of distribution drift

    Science.gov (United States)

    2017-05-09

    AFRL-AFOSR-JP-TR-2017-0039 Learning in the context of distribution drift Geoff Webb MONASH UNIVERSITY Final Report 05/09/2017 DISTRIBUTION A...Department of Defense, Executive Services, Directorate (0704-0188).   Respondents should be aware that notwithstanding any other provision of law, no person ...23 Apr 2015 to 22 Apr 2017 4.  TITLE AND SUBTITLE Learning in the context of distribution drift 5a.  CONTRACT NUMBER 5b.  GRANT NUMBER FA2386-15-1

  5. Shock drift mechanism for Forbush decreases

    Science.gov (United States)

    Cheng, Andrew F.; Sarris, E. T.; Dodopoulos, C.

    1990-01-01

    Consideration is given to the way in which Forbush decreases can arise from variable drifts in nonuniform shocks, where the variation in shock strength along the shock front causes both the shock drift distance and the energy gain to become variable. More particles can then be transported out of a given region of space and energy interval than were transported in, so a spacecraft passing through this region can observe a Forbush decrease in this energy interval despite shock energization and compression. A simple example of how this can occur is presented.

  6. Ultra-low mass drift chambers

    Energy Technology Data Exchange (ETDEWEB)

    Assiro, R. [Istituto Nazionale di Fisica Nucleare, Lecce (Italy); Cappelli, L. [Università di Cassino e del Lazio Meridionale (Italy); Cascella, M. [Istituto Nazionale di Fisica Nucleare, Lecce (Italy); Dipartimento Matematica e Fisica, Università del Salento (Italy); De Lorenzis, L. [Istituto Nazionale di Fisica Nucleare, Lecce (Italy); Dipartimento di Ingegneria dell' Innovazione, Università del Salento (Italy); Grancagnolo, F. [Istituto Nazionale di Fisica Nucleare, Lecce (Italy); Ignatov, F. [Budker Institute of Nuclear Physics, Novosibirsk (Russian Federation); L' Erario, A.; Maffezzoli, A. [Istituto Nazionale di Fisica Nucleare, Lecce (Italy); Dipartimento di Ingegneria dell' Innovazione, Università del Salento (Italy); Miccoli, A. [Istituto Nazionale di Fisica Nucleare, Lecce (Italy); Onorato, G. [Istituto Nazionale di Fisica Nucleare, Lecce (Italy); Budker Institute of Nuclear Physics, Novosibirsk (Russian Federation); Università G. Marconi, Roma (Italy); Perillo, M. [EnginSoft S.p.a., Trento (Italy); Piacentino, G. [Istituto Nazionale di Fisica Nucleare, Lecce (Italy); Fermilab, Batavia, IL (United States); Università G. Marconi, Roma (Italy); Rella, S. [Istituto Nazionale di Fisica Nucleare, Lecce (Italy); Dipartimento di Ingegneria dell' Innovazione, Università del Salento (Italy); Rossetti, F. [EnginSoft S.p.a., Trento (Italy); Spedicato, M. [Istituto Nazionale di Fisica Nucleare, Lecce (Italy); Tassielli, G., E-mail: giovanni.tassielli@le.infn.it [Istituto Nazionale di Fisica Nucleare, Lecce (Italy); Budker Institute of Nuclear Physics, Novosibirsk (Russian Federation); Università G. Marconi, Roma (Italy); and others

    2013-08-01

    We present a novel low mass drift chamber concept, developed in order to fulfill the stringent requirements imposed by the experiments for extremely rare processes, which require high resolutions (order of 100–200 keV/c) for particle momenta in a range (50–100 MeV/c) totally dominated by the multiple scattering contribution. We describe a geometry optimization procedure and a new wiring strategy with a feed-through-less wire anchoring system developed and tested on a drift chamber prototype under completion at INFN-Lecce.

  7. Algorithms for minimization of charge sharing effects in a hybrid pixel detector taking into account hardware limitations in deep submicron technology

    Science.gov (United States)

    Maj, P.; Baumbaugh, A.; Deptuch, G.; Grybos, P.; Szczygiel, R.

    2012-12-01

    Charge sharing is the main limitation of pixel detectors used in spectroscopic applications, noting that this applies to both time and amplitude/energy spectroscopy. Even though, charge sharing was the subject of many studies, there is still no ultimate solution which could be implemented in the hardware to suppress the negative effects of charge sharing. This is mainly because of strong demand on low power dissipation and small silicon area of a single pixel. The first solution of this problem was proposed by CERN and consequently it was implemented in the Medipix III chip. However, due to pixel-to-pixel threshold dispersions and some imperfections of the simplified algorithm, the hit allocation was not functioning properly. We are presenting novel algorithms which allow proper hit allocation even at the presence of charge sharing. They can be implemented in an integrated circuit using a deep submicron technology. In performed simulations, we assumed not only diffusive charge spread occurring in the course of charge drifting towards the electrodes but also limitations in the readout electronics, i.e. signal fluctuations due to noise and mismatch (gain and offsets). The simulations show that using, for example, a silicon pixel detector in the low X-ray energy range, we have been able to perform proper hit position identification and use the information from summing inter-pixel nodes for spectroscopy measurements.

  8. ATLAS Tracker and Pixel Operational Experience

    CERN Document Server

    AUTHOR|(INSPIRE)INSPIRE-00222525; The ATLAS collaboration

    2016-01-01

    The tracking performance of the ATLAS detector relies critically on the silicon and gaseous tracking subsystems that form the ATLAS Inner Detector. Those subsystems have undergone significant hardware and software upgrades to meet the challenges imposed by the higher collision energy, pileup and luminosity that are being delivered by the LHC during Run2. The key status and performance metrics of the Pixel Detector and the Semi Conductor Tracker, are summarised, and the operational experience and requirements to ensure optimum data quality and data taking efficiency are described.

  9. CMB component separation in the pixel domain

    OpenAIRE

    Doroshkevich, A.; Verkhodanov, O.

    2010-01-01

    We show that the popular ILC approach is unstable in respect to the division of the sample of map pixels to the set of ``homogeneous'' subsamples. For suitable choice of such subsamples we can obtain the restored CMB signal with amplitudes ranged from zero to the amplitudes of the observed signal. We propose approach which allows us to obtain reasonable estimates of $C_\\ell$ at $\\ell\\leq 30$ and similar to WMAP $C_\\ell$ for larger $\\ell$. With this approach we reduce some anomalies of the WMA...

  10. ISPA (imaging silicon pixel array) experiment

    CERN Multimedia

    Patrice Loïez

    2002-01-01

    The ISPA tube is a position-sensitive photon detector. It belongs to the family of hybrid photon detectors (HPD), recently developed by CERN and INFN with leading photodetector firms. HPDs confront in a vacuum envelope a photocathode and a silicon detector. This can be a single diode or a pixelized detector. The electrons generated by the photocathode are efficiently detected by the silicon anode by applying a high-voltage difference between them. ISPA tube can be used in high-energy applications as well as bio-medical and imaging applications.

  11. Reading pixelized paragraphs of Chinese characters using simulated prosthetic vision.

    Science.gov (United States)

    Zhao, Ying; Lu, Yanyu; Zhao, Ji; Wang, Kaihu; Ren, Qiushi; Wu, Kaijie; Chai, Xinyu

    2011-07-29

    Visual prostheses offer a possibility of restoring useful reading ability to the blind. The psychophysics of simulating reading with a prosthesis using pixelized text has attracted attention recently. This study was an examination of the reading accuracy and efficiency of pixelized Chinese paragraphs after different parameters were altered. Forty native Chinese speakers with normal or corrected visual acuity (20/20) participated in four experiments. Reading accuracy and efficiency were measured after changing the character resolution, character size, pixel dropout percentage, number of gray levels, and luminance. A 5° × 5° character appeared to be the optimal size necessary for accurate pixelized reading. Reading accuracy close to 100% could be achieved with 10 × 10 pixels/character and ∼60% with a 6 × 6 pixel resolution. Pixel dropout adversely affected accuracy, and paragraphs with a 50% dropout were unreadable. Luminance had little effect; however, the number of gray levels significantly affected reading performance. Paragraph reading was at least 5% more accurate at each resolution than was the accuracy of Chinese character recognition. Character size and resolution, pixel dropout, and the number of gray levels clearly affected the reading performance of pixelized Chinese paragraphs. Compared with pixelized character recognition, pixelized Chinese paragraph reading achieved higher accuracy; thus, optimal Chinese reading performance may require prostheses with more electrodes (1000) than are required to read paragraphs in the Latin alphabet (500).

  12. Performance limits of a single photon counting pixel system

    Energy Technology Data Exchange (ETDEWEB)

    Chmeissani, M.; Mikulec, B. E-mail: bettina.mikulec@cern.ch

    2001-03-11

    X-ray imaging using hybrid pixel detectors in single photon counting mode is a relatively recent and exciting development. The photon counting mode implies that each pixel has a threshold in energy above which a hit is recorded. Sharing of charge between adjacent pixels would therefore lead to a loss of registered hits and for medical imaging applications to a higher patient dose. This explains why the demand for high spatial resolution and consequently small pixel sizes (<100 {mu}m) motivates the Medipix2 collaboration to study the effects of charge sharing between pixels on system performance. Two different simulation codes are used to simulate the energy loss inside the detector and the charge transport towards the pixel electrodes. The largest contribution to the lateral spreading of charge comes from diffusion and can result in a considerable loss of detection efficiency in photon counting systems for small pixel sizes.

  13. A neighbor pixel communication filtering structure for Dynamic Vision Sensors

    Science.gov (United States)

    Xu, Yuan; Liu, Shiqi; Lu, Hehui; Zhang, Zilong

    2017-02-01

    For Dynamic Vision Sensors (DVS), thermal noise and junction leakage current induced Background Activity (BA) is the major cause of the deterioration of images quality. Inspired by the smoothing filtering principle of horizontal cells in vertebrate retina, A DVS pixel with Neighbor Pixel Communication (NPC) filtering structure is proposed to solve this issue. The NPC structure is designed to judge the validity of pixel's activity through the communication between its 4 adjacent pixels. The pixel's outputs will be suppressed if its activities are determined not real. The proposed pixel's area is 23.76×24.71μm2 and only 3ns output latency is introduced. In order to validate the effectiveness of the structure, a 5×5 pixel array has been implemented in SMIC 0.13μm CIS process. 3 test cases of array's behavioral model show that the NPC-DVS have an ability of filtering the BA.

  14. Pixel 2010: A résumé

    CERN Document Server

    Wermes, Norbert

    2011-01-01

    The Pixel 2010 conference focused on semiconductor pixel detectors for particle tracking/vertexing as well as for imaging, in particular for synchrotron light sources and XFELs. The big LHC hybrid pixel detectors have impressively started showing their capabilities. X-ray imaging detectors, also using the hybrid pixel technology, have greatly advanced the experimental possibilities for diffraction experiments. Monolithic or semi-monolithic devices like CMOS active pixels and DEPFET pixels have now reached a state such that complete vertex detectors for RHIC and superKEKB are being built with these technologies. Finally, new advances towards fully monolithic active pixel detectors, featuring full CMOS electronics merged with efficient signal charge collection, exploiting standard CMOS technologies, SOI and/or 3D integration, show the path for the future. This résumé attempts to extract the main statements of the results and developments presented at this conference.

  15. Study of Charge Diffusion in a Silicon Detector Using an Energy Sensitive Pixel Readout Chip

    CERN Document Server

    Schioppa, E. J.; van Beuzekom, M.; Visser, J.; Koffeman, E.; Heijne, E.; Engel, K. J.; Uher, J.

    2015-01-01

    A 300 μm thick thin p-on-n silicon sensor was connected to an energy sensitive pixel readout ASIC and exposed to a beam of highly energetic charged particles. By exploiting the spectral information and the fine segmentation of the detector, we were able to measure the evolution of the transverse profile of the charge carriers cloud in the sensor as a function of the drift distance from the point of generation. The result does not rely on model assumptions or electric field calculations. The data are also used to validate numerical simulations and to predict the detector spectral response to an X-ray fluorescence spectrum for applications in X-ray imaging.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-07-11

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

  17. The ALICE Silicon Pixel Detector System

    CERN Document Server

    Fadmar Osmic, FO

    2006-01-01

    The European Organization for Particle Physics (CERN) in Geneva is currently constructing the Large Hadron Collider (LHC), which will allow the study of the subnuclear ranges of physics with an accuracy never achieved before. Within the LHC project, ALICE is to the study of strongly interacting matter at extreme densities and high temperatures. ALICE as many other modern High Energy Physics (HEP) experiments uses silicon pixel detectors for tracking close to the interaction point (IP). The ALICE Silicon Pixel Detector (SPD) will constitute the two innermost layers of ALICE, and will due to its high granularity provide precise tracking information. In heavy ion collisions, the track density could be as high as 80 tracks/cm2 in the first SPD layer. The SPD will provide tracking information at radii of 3.9 and 7.6 cm from the IP. It is a fundamental element for the study of the weak decays of the particles carrying heavy flavour, whose typical signature will be a secondary vertex separated from the primary verte...

  18. Silicon pixel R&D for CLIC

    CERN Document Server

    AUTHOR|(SzGeCERN)754303

    2016-01-01

    Challenging detector requirements are imposed by the physics goals at the future multi-TeV e+e- Compact Linear Collider (CLIC). A single point resolution of 3μm for the vertex detector and 7μm for the tracker is required. Moreover, the CLIC vertex detector and tracker need to be extremely light weighted with a material budget of 0.2 % X0 per layer in the ver- tex detector and 1-2%X0 in the tracker. A fast time slicing of 10ns is further required to suppress background from beam-beam interactions. A wide range of sensor and readout ASIC technologies are investigated within the CLIC silicon pixel R&D effort. Various hybrid planar sensor assemblies with a pixel size of 25x25μm2 and 55x55μm2 have been produced and characterised by laboratory measurements and during test-beam campaigns. Experimental and simulation results for thin (50μm-500μm) slim edge and active-edge planar, and High-Voltage CMOS sensors hybridised to various readout ASICs (Timepix, Timepix3, CLICpix) are presented.

  19. Silicon pixel R&D for CLIC

    Science.gov (United States)

    Munker, M.

    2017-01-01

    Challenging detector requirements are imposed by the physics goals at the future multi-TeV e+ e‑ Compact Linear Collider (CLIC). A single point resolution of 3 μm for the vertex detector and 7 μm for the tracker is required. Moreover, the CLIC vertex detector and tracker need to be extremely light weighted with a material budget of 0.2% X0 per layer in the vertex detector and 1–2% X0 in the tracker. A fast time slicing of 10 ns is further required to suppress background from beam-beam interactions. A wide range of sensor and readout ASIC technologies are investigated within the CLIC silicon pixel R&D effort. Various hybrid planar sensor assemblies with a pixel size of 25×25 μm2 and 55×55 μm2 have been produced and characterised by laboratory measurements and during test-beam campaigns. Experimental and simulation results for thin (50 μm–500 μm) slim edge and active-edge planar, and High-Voltage CMOS sensors hybridised to various readout ASICs (Timepix, Timepix3, CLICpix) are presented.

  20. The Phase1 CMS Pixel detector upgrade

    CERN Document Server

    Tavolaro, Vittorio Raoul

    2016-01-01

    The pixel detector of the CMS experiment will be replaced in an extended end-of-year shutdown during winter 2016/2017 with an upgraded one able to cope with peak instantaneous luminosities beyond the nominal LHC instantaneous luminosity of $1 \\times 10^{34}$ cm$^{-2}$ s$^{-1}$. Under the conditions expected in the coming years, which will see an increase of a factor two in instantaneous luminosity, the present system would experience a dynamic inefficiency caused mainly by data losses due to buffer overflows. The Phase I upgrade of the CMS pixel detector, described in this paper, will operate at full efficiency at an instantaneous luminosity of $2 \\times 10^{34}$ cm$^{-2}$ s$^{-1}$, thanks to a new readout chip. The new detector will feature one additional tracking point both in the barrel and in the forward regions, while reducing the material budget as a result of a new CO$_{2}$ cooling system and optimised layout of the services. In this paper, the design and the technological choices of the Phase I detect...

  1. optical links for the atlas pixel detector

    CERN Document Server

    Stucci, Stefania Antonia; The ATLAS collaboration

    2015-01-01

    Optical links are necessary to satisfy the high speed readout over long distances for advanced silicon detector systems. We report on the optical readout used in the newly installed central pixel layer (IBL) in the ATLAS experiment. The off detector readout employs commercial optical to analog converters, which were extensively tested for this application. Performance measurements during installation and commissioning will be shown. With the increasing instantaneous luminosity in the next years, the next layers outwards of IBL of the ATLAS Pixel detector (Layer 1 and Layer 2) will reach their bandwidth limits. A plan to increase the bandwidth by upgrading the off detector readout chain is put in place. The plan also involves new optical readout components, in particular the optical receivers, for which commercial units cannot be used and a new design has been made. The latter allows for a wider operational range in term of data frequency and light input power to match the on-detector sending units on the pres...

  2. Optical links for the ATLAS Pixel detector

    CERN Document Server

    Stucci, Stefania Antonia; The ATLAS collaboration

    2015-01-01

    Optical links are necessary to satisfy the high speed readout over long distances for advanced silicon detector systems. We report on the optical readout used in the newly installed central pixel layer (IBL) in the ATLAS experiment. The off detector readout employs commercial optical to analog converters, which were extensively tested for this application. Performance measurements during installation and commissioning will be shown. With the increasing instantaneous luminosity in the next years, the next layers outwards of IBL of the ATLAS Pixel detector (Layer 1 and Layer 2) will reach their bandwidth limits. A plan to increase the bandwidth by upgrading the off detector readout chain is put in place. The plan also involves new optical readout components, in particular the optical receivers, for which commercial units cannot be used and a new design has been made. The latter allows for a wider operational range in term of data frequency and light input power to match the on-detector sending units on the pres...

  3. The Phase II ATLAS ITk Pixel Upgrade

    CERN Document Server

    Terzo, Stefano; The ATLAS collaboration

    2017-01-01

    The entire tracking system of the ATLAS experiment will be replaced during the LHC Phase II shutdown (foreseen to take place around 2025) by an all-silicon detector called the "ITk" (Inner Tracker). The innermost portion of ITk will consist of a pixel detector with five layers in the barrel region and and ring-shaped supports in the endcap regions. It will be instrumented with new sensor and readout electronics technologies to improve the tracking performance and cope with the HL-LHC environment, which will be severe in terms of occupancy and radiation. The total surface area of silicon in the new pixel system could measure up to 14 m$^2$ , depending on the final layout choice, which is expected to take place in early 2017. Several layout options are being investigated at the moment, including some with novel inclined support structures in the barrel-endcap overlap region and others with very long innermost barrel layers. Forward coverage could be as high as $|\\eta| < 4$. Supporting structures will be ...

  4. The Phase-2 ATLAS ITk Pixel Upgrade

    CERN Document Server

    Flick, Tobias; The ATLAS collaboration

    2016-01-01

    The entire tracking system of the ATLAS experiment will be replaced during the LHC Phase II shutdown (foreseen to take place around 2025) by an all-silicon detector called the “ITk” (Inner Tracker). The pixel detector will comprise the five innermost layers, and will be instrumented with new sensor and readout electronics technologies to improve the tracking performance and cope with the HL-LHC environment, which will be severe in terms of occupancy and radiation. The total surface area of silicon in the new pixel system could measure up to 14 m2, depending on the final layout choice, which is expected to take place in early 2017. Four layout options are being investigated at the moment, two with forward coverage to |eta| < 3.2 and two to |eta| < 4. For each coverage option, a layout with long barrel staves and a layout with novel inclined support structures in the barrel-endcap overlap region are considered. All potential layouts include modules mounted on ring-shaped supports in the endcap regions...

  5. Further applications for mosaic pixel FPA technology

    Science.gov (United States)

    Liddiard, Kevin C.

    2011-06-01

    In previous papers to this SPIE forum the development of novel technology for next generation PIR security sensors has been described. This technology combines the mosaic pixel FPA concept with low cost optics and purpose-designed readout electronics to provide a higher performance and affordable alternative to current PIR sensor technology, including an imaging capability. Progressive development has resulted in increased performance and transition from conventional microbolometer fabrication to manufacture on 8 or 12 inch CMOS/MEMS fabrication lines. A number of spin-off applications have been identified. In this paper two specific applications are highlighted: high performance imaging IRFPA design and forest fire detection. The former involves optional design for small pixel high performance imaging. The latter involves cheap expendable sensors which can detect approaching fire fronts and send alarms with positional data via mobile phone or satellite link. We also introduce to this SPIE forum the application of microbolometer IR sensor technology to IoT, the Internet of Things.

  6. The Pixels system: last but not late!

    CERN Multimedia

    Kevin Einsweiler

    The Pixel Detector for ATLAS is one of the smallest, but most challenging components of the experiment. It lives in the dangerous territory directly outside the beampipe, where the radiation environment is particularly fierce, and it must be roughly one million times more radiation-hard than its human designers. Starting at a radius of just 5cm from the interaction point where the proton beams collide, it occupies a volume of slightly more than one meter in length and a half meter in diameter. In this compact region, there are eighty million channels of electronics (most of the electronics channels in ATLAS!), each capable of measuring the charge deposited by a track in a silicon pixel measuring only 50 microns by 400 microns in size (a volume of 0.005 cubic millimeters). A total cooling capacity of 15 KWatts is available to keep it operating comfortably at -5C. This detector is built around, and provides the support for, the central beampipe of ATLAS. It is supported on carbon fiber rails inside of the Pix...

  7. Efficient single pixel imaging in Fourier space

    Science.gov (United States)

    Bian, Liheng; Suo, Jinli; Hu, Xuemei; Chen, Feng; Dai, Qionghai

    2016-08-01

    Single pixel imaging (SPI) is a novel technique capturing 2D images using a bucket detector with a high signal-to-noise ratio, wide spectrum range and low cost. Conventional SPI projects random illumination patterns to randomly and uniformly sample the entire scene’s information. Determined by Nyquist sampling theory, SPI needs either numerous projections or high computation cost to reconstruct the target scene, especially for high-resolution cases. To address this issue, we propose an efficient single pixel imaging technique (eSPI), which instead projects sinusoidal patterns for importance sampling of the target scene’s spatial spectrum in Fourier space. Specifically, utilizing the centrosymmetric conjugation and sparsity priors of natural images’ spatial spectra, eSPI sequentially projects two \\tfrac{π }{2}-phase-shifted sinusoidal patterns to obtain each Fourier coefficient in the most informative spatial frequency bands. eSPI can reduce requisite patterns by two orders of magnitude compared to conventional SPI, which helps a lot for fast and high-resolution SPI.

  8. Pixel-Tilecal-MDT Combined Test Beam

    CERN Multimedia

    B. Di Girolamo

    A test with many expectations When an additional week of running (from September 11th to 18th) was allocated for the test-beam, it was decided to give priority to a combined run with the participation of the Pixel, Tilecal and MDT sub-detectors. The integration of these three sub-detectors was possible as they all use the baseline (DAQ-1/EF based) DAQ for test beams (as reported in a previous e-news). The tests and the addition of a common trigger and busy were organized in a short timescale by experts from the three sub-detectors and DAQ/EF. The expectations were many; both looking for problems and finding solutions. The setup The setup, shown in the figure, consisted of the Pixel telescope normally used during the sub-detector tests, two Tilecal barrel modules, two Tilecal extended barrel modules, and six MDT barrel chambers. This fully occupied a length of some 30 meters in the H8 line of the SPS North Area. Each sub-detector used their own specialized front-end electronics. The data collected by modu...

  9. ATLAS rewards two pixel detector suppliers

    CERN Multimedia

    2007-01-01

    Peter Jenni, ATLAS spokesperson, presented the ATLAS supplier award to Herbert Reichl, IZM director, and to Simonetta Di Gioia, from the SELEX company.Two of ATLAS’ suppliers were awarded prizes at a ceremony on Wednesday 13 June attended by representatives of the experiment’s management and of CERN. The prizes went to the Fraunhofer Institut für Zuverlässigkeit und Mikrointegration (IZM) in Berlin and the company SELEX Sistemi Integrati in Rome for the manufacture of modules for the ATLAS pixel detector. SELEX supplied 1500 of the modules for the tracker, while IZM produced a further 1300. The modules, each made up of 46080 channels, form the active part of the ATLAS pixel detector. IZM and SELEX received the awards for the excellent quality of their work: the average number of faulty channels per module was less than 2.10-3. They also stayed within budget and on schedule. The difficulty they faced was designing modules based on electronic components and sensor...

  10. Psychometric Consequences of Subpopulation Item Parameter Drift

    Science.gov (United States)

    Huggins-Manley, Anne Corinne

    2017-01-01

    This study defines subpopulation item parameter drift (SIPD) as a change in item parameters over time that is dependent on subpopulations of examinees, and hypothesizes that the presence of SIPD in anchor items is associated with bias and/or lack of invariance in three psychometric outcomes. Results show that SIPD in anchor items is associated…

  11. Low-drift micro flow sensors

    NARCIS (Netherlands)

    Dijkstra, Marcel

    2009-01-01

    The emerging fields of micro total-analysis systems (micro-TAS), micro-reactors and bio-MEMS drives the need for further miniaturisation of sensors measuring quantities such as pressure, temperature and flow. The research described in this thesis concerns the development of low-drift micro flow sens

  12. Experimental design for drifting buoy Lagrangian test

    Science.gov (United States)

    Saunders, P. M.

    1975-01-01

    A test of instrumentation fabricated to measure the performance of a free drifting buoy as a (Lagrangian) current meter is described. Specifically it is proposed to distinguish between the trajectory of a drogued buoy and the trajectory of the water at the level of the drogue by measuring the flow relative to the drogue.

  13. Psychometric Consequences of Subpopulation Item Parameter Drift

    Science.gov (United States)

    Huggins-Manley, Anne Corinne

    2017-01-01

    This study defines subpopulation item parameter drift (SIPD) as a change in item parameters over time that is dependent on subpopulations of examinees, and hypothesizes that the presence of SIPD in anchor items is associated with bias and/or lack of invariance in three psychometric outcomes. Results show that SIPD in anchor items is associated…

  14. Ion Landau Damping on Drift Tearing Modes

    CERN Document Server

    Connor, J W; Zocco, A

    2012-01-01

    The equations governing the ion Landau damping (ILD) layers for a drift tearing mode are derived and solved to provide a matching to ideal MHD solutions at large $x$ and to the drift tearing solution emerging from the ion kinetic region, $k\\rho_{i}\\sim1$, at small $x,$ the distance from the rational surface. The ILD layers lie on either side of the mode rational surface at locations defined by $k_{y}xV_{Ti}/L_{s}=\\omega_{*e}(1+0.73\\eta_{e})$ and have been ignored in many previous analyses of linear drift tearing stability. The effect of the ILD layer on the drift tearing mode is to introduce an additional stabilizing contribution, requiring even larger values of the stability index, $\\Delta^{\\prime}$ for instability, than predicted by Connor Hastie and Zocco [PPCF,54, 035003, (2012)] and Cowley, Kulsrud and Hahm [Phys. Fluids,29, 3230, (1986)]. The magnitude and scaling of the new stabilizing effect in slab geometry is discussed.

  15. Stable discrete representation of relativistically drifting plasmas

    CERN Document Server

    Kirchen, Manuel; Godfrey, Brendan B; Dornmair, Irene; Jalas, Soeren; Peters, Kevin; Vay, Jean-Luc; Maier, Andreas R

    2016-01-01

    Representing the electrodynamics of relativistically drifting particle ensembles in discrete, co-propagating Galilean coordinates enables the derivation of a Particle-in-Cell algorithm that is intrinsically free of the Numerical Cherenkov Instability, for plasmas flowing at a uniform velocity. Application of the method is shown by modeling plasma accelerators in a Lorentz-transformed optimal frame of reference.

  16. Plate Tectonics and Continental Drift: Classroom Ideas.

    Science.gov (United States)

    Stout, Prentice K.

    1983-01-01

    Suggests various classroom studies related to plate tectonics and continental drift, including comments on and sources of resource materials useful in teaching the topics. A complete list of magazine articles on the topics from the Sawyer Marine Resource Collection may be obtained by contacting the author. (JN)

  17. Learning drifting concepts with neural networks

    NARCIS (Netherlands)

    Biehl, Michael; Schwarze, Holm

    1993-01-01

    The learning of time-dependent concepts with a neural network is studied analytically and numerically. The linearly separable target rule is represented by an N-vector, whose time dependence is modelled by a random or deterministic drift process. A single-layer network is trained online using differ

  18. Mode selective control of drift wave turbulence

    DEFF Research Database (Denmark)

    Schröder, C.; Klinger, T.; Block, D.;

    2001-01-01

    Experiments on spatiotemporal open-loop synchronization of drift wave turbulence in a magnetized cylindrical plasma are reported. The synchronization effect is modeled by a rotating current profile with prescribed mode structure. Numerical simulations of an extended Hasegawa-Wakatani model show g...

  19. Visualizing CMS muon drift tubes’ currents

    CERN Document Server

    Hamarik, Lauri

    2015-01-01

    This report documents my work as a summer student in the CMS DT group at CERN in July and August of 2015. During that time, I have participated in relocating DT monitoring experiment to GIF++ site and creating software to analyze drift tubes’ wires current dependence on luminosity and radioactivity.

  20. Drift wave launching in a linear quadrupole

    Energy Technology Data Exchange (ETDEWEB)

    Tessema, G.Y.; Elliott, J.A.; Rusbridge, M.G. (Manchester Univ. (UK). Inst. of Science and Technology)

    1989-12-01

    Drift waves have been successfully launched from flag probes in a steady-state magnetized plasma, and the launching mechanism has been identified. Non-linear interactions are observed between launched and intrinsic waves. A wide range of further experimental studies is thus made possible, of fundamental relevance to plasma confinement. (author).

  1. A large acceptance cylindrical drift chamber detector

    Energy Technology Data Exchange (ETDEWEB)

    Ambrose, D.A. [Texas Univ., Austin, TX (United States); Bachman, M.G. [Texas Univ., Austin, TX (United States); Coffey, W.P. [Texas Univ., Austin, TX (United States); Glass, G. [Texas Univ., Austin, TX (United States); McNaughton, K.H. [Texas Univ., Austin, TX (United States); Riley, P.J. [Texas Univ., Austin, TX (United States); Adams, D.L. [Rice University, Houston, TX 77251 (United States); Gaussiran, T.L. [Rice University, Houston, TX 77251 (United States); Hungerford, E.V. [University of Houston, Houston, TX 77204 (United States); Lan, K.A. [University of Houston, Houston, TX 77204 (United States); Johnston, K. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); McNaughton, M.W. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Penttila, S.I. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Supek, I. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

    1995-10-01

    This paper describes a large acceptance cylindrical drift chamber detector designed and built for the study of the np{yields}pp{pi}{sup -} reaction at neutron beam energies in the range 500-800 MeV. Details of construction, electronics, testing, and detection efficiencies and resolutions are presented. (orig.).

  2. Stochastic Evolution Equations with Adapted Drift

    NARCIS (Netherlands)

    Pronk, M.

    2013-01-01

    In this thesis we study stochastic evolution equations in Banach spaces. We restrict ourselves to the two following cases. First, we consider equations in which the drift is a closed linear operator that depends on time and is random. Such equations occur as mathematical models in for instance

  3. Effects of Drifting Macroalgae in Eelgrass Ecosystems

    DEFF Research Database (Denmark)

    Canal Vergés, Paula; Valdemarsen, Thomas Bruun; Kristensen, Erik

    2010-01-01

    and physical damage on eelgrass can occur when macroalgae are drifting as bedload. The ballistic effect of moving macroalgae on surface sediment was tested in the field as well as in a series of annular flume experiments, where simultaneous measurements of macroalgae transport and turbidity were measured...

  4. Effects of Drifting Macroalgae in Eelgrass Ecosystems

    DEFF Research Database (Denmark)

    Canal Vergés, Paula; Valdemarsen, Thomas Bruun; Kristensen, Erik

    2010-01-01

    It has been suggested that current-driven macroalge transport in shallow lagoons and estuaries may negatively impact eelgrass through increased turbidity and physical stress. Increased turbidity and lower light availability for eelgrass may result when drifting macroalgae erode surface sediment a...

  5. Multi-scale feature learning on pixels and super-pixels for seminal vesicles MRI segmentation

    Science.gov (United States)

    Gao, Qinquan; Asthana, Akshay; Tong, Tong; Rueckert, Daniel; Edwards, Philip "Eddie"

    2014-03-01

    We propose a learning-based approach to segment the seminal vesicles (SV) via random forest classifiers. The proposed discriminative approach relies on the decision forest using high-dimensional multi-scale context-aware spatial, textual and descriptor-based features at both pixel and super-pixel level. After affine transformation to a template space, the relevant high-dimensional multi-scale features are extracted and random forest classifiers are learned based on the masked region of the seminal vesicles from the most similar atlases. Using these classifiers, an intermediate probabilistic segmentation is obtained for the test images. Then, a graph-cut based refinement is applied to this intermediate probabilistic representation of each voxel to get the final segmentation. We apply this approach to segment the seminal vesicles from 30 MRI T2 training images of the prostate, which presents a particularly challenging segmentation task. The results show that the multi-scale approach and the augmentation of the pixel based features with the super-pixel based features enhances the discriminative power of the learnt classifier which leads to a better quality segmentation in some very difficult cases. The results are compared to the radiologist labeled ground truth using leave-one-out cross-validation. Overall, the Dice metric of 0:7249 and Hausdorff surface distance of 7:0803 mm are achieved for this difficult task.

  6. Pixel-level Analog-To-Digital Converters for Hybrid Pixel Detectors with energy sensitivity

    NARCIS (Netherlands)

    San Segundo Bello, David; Nauta, Bram; Visschers, Jan

    2000-01-01

    Single-photon counting hybrid pixel detectors have shown to be a valid alternative to other types of X-ray imaging devices due to their high sensitivity, low noise, linear behavior and wide dynamic range. One important advantage of these devices is the fact that detector and readout electronics are

  7. Design of pixel-level ADCs for energy-sensitive hybrid pixel detectors

    NARCIS (Netherlands)

    San Segundo Bello, David; Nauta, Bram; Visschers, Jan

    2000-01-01

    Single-photon counting hybrid pixel detectors have shown to be a valid alternative to other types of X-ray imaging devices due to their high sensitivity, low noise, linear behavior and wide dynamic range. One important advantage of these devices is the fact that detector and readout electronics are

  8. Generalization of the one dimensional modeling and design considerations of spiral Si drift detectors: Flat (straight) drift channels and constant drift fields

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Manwen, E-mail: mwliu1993@163.com; Li, Zheng, E-mail: zhengli58@gmail.com

    2016-07-11

    The one-dimensional design consideration for the spiral (cylindrical geometry) Si drift detector (SDD) has been modified and generalized for small drift distance (R) compatible to the detector thickness (d), i.e. for R–d, and for non uniform backside biasing situations. By applying a non uniform biasing voltage with a gradient similar (proportional) to the front side, one can increase the reach-through voltage, resulting in a large drift field for carriers. This can be important for large R (>3 mm). With a careful design of electric field profiles on both sides, one can obtain the optimum case of a spiral SDD with a straight (flat) drift channel and constant drift field throughout the carrier drift channel. The previous solution in the literature is an approximation of this work for R»d and with a curved drift channel.

  9. Generalization of the one dimensional modeling and design considerations of spiral Si drift detectors: Flat (straight) drift channels and constant drift fields

    Science.gov (United States)

    Liu, Manwen; Li, Zheng

    2016-07-01

    The one-dimensional design consideration for the spiral (cylindrical geometry) Si drift detector (SDD) has been modified and generalized for small drift distance (R) compatible to the detector thickness (d), i.e. for R-d, and for non uniform backside biasing situations. By applying a non uniform biasing voltage with a gradient similar (proportional) to the front side, one can increase the reach-through voltage, resulting in a large drift field for carriers. This can be important for large R (>3 mm). With a careful design of electric field profiles on both sides, one can obtain the optimum case of a spiral SDD with a straight (flat) drift channel and constant drift field throughout the carrier drift channel. The previous solution in the literature is an approximation of this work for R»d and with a curved drift channel.

  10. Serial pixel analog-to-digital converter (ADC)

    Science.gov (United States)

    Larson, Eric D.

    2010-02-01

    This method reduces the data path from the counter to the pixel register of the analog-to-digital converter (ADC) from as many as 10 bits to a single bit. The reduction in data path width is accomplished by using a coded serial data stream similar to a pseudo random number (PRN) generator. The resulting encoded pixel data is then decoded into a standard hexadecimal format before storage. The high-speed serial pixel ADC concept is based on the single-slope integrating pixel ADC architecture. Previous work has described a massively parallel pixel readout of a similar architecture. The serial ADC connection is similar to the state-of-the art method with the exception that the pixel ADC register is a shift register and the data path is a single bit. A state-of-the-art individual-pixel ADC uses a single-slope charge integration converter architecture with integral registers and "one-hot" counters. This implies that parallel data bits are routed among the counter and the individual on-chip pixel ADC registers. The data path bit-width to the pixel is therefore equivalent to the pixel ADC bit resolution.

  11. Edge pixel response studies of edgeless silicon sensor technology for pixellated imaging detectors

    Science.gov (United States)

    Maneuski, D.; Bates, R.; Blue, A.; Buttar, C.; Doonan, K.; Eklund, L.; Gimenez, E. N.; Hynds, D.; Kachkanov, S.; Kalliopuska, J.; McMullen, T.; O'Shea, V.; Tartoni, N.; Plackett, R.; Vahanen, S.; Wraight, K.

    2015-03-01

    Silicon sensor technologies with reduced dead area at the sensor's perimeter are under development at a number of institutes. Several fabrication methods for sensors which are sensitive close to the physical edge of the device are under investigation utilising techniques such as active-edges, passivated edges and current-terminating rings. Such technologies offer the goal of a seamlessly tiled detection surface with minimum dead space between the individual modules. In order to quantify the performance of different geometries and different bulk and implant types, characterisation of several sensors fabricated using active-edge technology were performed at the B16 beam line of the Diamond Light Source. The sensors were fabricated by VTT and bump-bonded to Timepix ROICs. They were 100 and 200 μ m thick sensors, with the last pixel-to-edge distance of either 50 or 100 μ m. The sensors were fabricated as either n-on-n or n-on-p type devices. Using 15 keV monochromatic X-rays with a beam spot of 2.5 μ m, the performance at the outer edge and corners pixels of the sensors was evaluated at three bias voltages. The results indicate a significant change in the charge collection properties between the edge and 5th (up to 275 μ m) from edge pixel for the 200 μ m thick n-on-n sensor. The edge pixel performance of the 100 μ m thick n-on-p sensors is affected only for the last two pixels (up to 110 μ m) subject to biasing conditions. Imaging characteristics of all sensor types investigated are stable over time and the non-uniformities can be minimised by flat-field corrections. The results from the synchrotron tests combined with lab measurements are presented along with an explanation of the observed effects.

  12. Characterization of charge carrier collection in a CdZnTe Frisch collar detector with a highly collimated {sup 137}Cs source

    Energy Technology Data Exchange (ETDEWEB)

    Kargar, Alireza [S.M.A.R.T. Laboratory, Department of Mechanical and Nuclear Engineering, Kansas State University, Manhattan, KS 66506 (United States); Harrison, Mark J. [Nuclear and Radiological Engineering, University of Florida, 202 NSB, Gainesville, FL 32611 (United States); Brooks, Adam C. [S.M.A.R.T. Laboratory, Department of Mechanical and Nuclear Engineering, Kansas State University, Manhattan, KS 66506 (United States); McGregor, Douglas S., E-mail: mcgregor@ksu.ed [S.M.A.R.T. Laboratory, Department of Mechanical and Nuclear Engineering, Kansas State University, Manhattan, KS 66506 (United States)

    2010-08-21

    A 4.7 x4.7x9.5 mm{sup 3} CdZnTe Frisch collar device was characterized through probing the device with a highly collimated {sup 137}Cs 662 keV gamma ray source. In a systematic series of experiments, the detector was probed along the length and width with a {sup 137}Cs gamma ray source using a 43.0 mm long Pb-collimator with a 0.6 mm circular hole. The detector was probed along the central line under different operating voltages of 1200, 1000, 800, 600 and 400 V. The experimental results correlated well to charge collection calculations for a modeled device with the same size and operating conditions. It was proved that, unlike the planar configuration, the charge collection efficiency profile along the length of Frisch collar device is considerably improved. The CdZnTe raw materials for this study were acquired from Redlen Technologies, and the Frisch collar device was fabricated and characterized at S.M.A.R.T. Laboratory at Kansas State University.

  13. Correlated analysis of 2 MeV proton-induced radiation damage in CdZnTe crystals using photoluminescence and thermally stimulated current techniques

    Science.gov (United States)

    Gu, Yaxu; Jie, Wanqi; Rong, Caicai; Wang, Yuhan; Xu, Lingyan; Xu, Yadong; Lv, Haoyan; Shen, Hao; Du, Guanghua; Fu, Xu; Guo, Na; Zha, Gangqiang; Wang, Tao

    2016-11-01

    Radiation damage induced by 2 MeV protons in CdZnTe crystals has been studied by means of photoluminescence (PL) and thermally stimulated current (TSC) techniques. A notable quenching of PL intensity is observed in the regions irradiated with a fluence of 6 × 1013 p/cm2, suggesting the increase of non-radiative recombination centers. Moreover, the intensity of emission peak Dcomplex centered at 1.48 eV dominates in the PL spectrum obtained from irradiated regions, ascribed to the increase of interstitial dislocation loops and A centers. The intensity of TSC spectra in irradiated regions decreases compared to the virgin regions, resulting from the charge collection inefficiency caused by proton-induced recombination centers. By comparing the intensity of identified traps obtained from numerical fitting using simultaneous multiple peak analysis (SIMPA) method, it suggests that proton irradiation under such dose can introduce high density of dislocation and A-centers in CdZnTe crystals, consistent with PL results.

  14. Defect Measurements of CdZnTe Detectors Using I-DLTS, TCT, I-V and Gamma-ray Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Gul,R.

    2008-08-11

    In this work we measured the crystal defect levels and tested the performance of CdZnTe detectors by diverse methodologies, viz., Current Deep Level Transient Spectroscopy (I-DLTS), Transient Current Technique (TCT), Current and Capacitance versus Voltage measurements (I-V and C-V), and gamma-ray spectroscopy. Two important characteristics of I-DLTS technique for advancing this research are (1) it is applicable for high-resistivity materials (>10{sup 6} {Omega}-cm), and, (2) the minimum temperature for measurements can be as low as 10 K. Such low-temperature capability is excellent for obtaining measurements at shallow levels. We acquired CdZnTe crystals grown by different techniques from two different vendors and characterized them for point defects and their response to photons. I-DLTS studies encompassed measuring the parameters of the defects, such as the energy levels in the band gap, the carrier capture cross-sections and their densities. The current induced by the laser-generated carriers and the charge collected (or number of electrons collected) were obtained using TCT that also provides the transport properties, such as the carrier life time and mobility of the detectors under study. The detector's electrical characteristics were explored, and its performance tested using I-V, C-V and gamma-ray spectroscopy.

  15. Dynamics of native oxide growth on CdTe and CdZnTe X-ray and gamma-ray detectors

    Science.gov (United States)

    Zázvorka, Jakub; Franc, Jan; Beran, Lukáš; Moravec, Pavel; Pekárek, Jakub; Veis, Martin

    2016-01-01

    Abstract We studied the growth of the surface oxide layer on four different CdTe and CdZnTe X-ray and gamma-ray detector-grade samples using spectroscopic ellipsometry. We observed gradual oxidization of CdTe and CdZnTe after chemical etching in bromine solutions. From X-ray photoelectron spectroscopy measurements, we found that the oxide consists only of oxygen bound to tellurium. We applied a refined theoretical model of the surface layer to evaluate the spectroscopic ellipsometry measurements. In this way we studied the dynamics and growth rate of the oxide layer within a month after chemical etching of the samples. We observed two phases in the evolution of the oxide layer on all studied samples. A rapid growth was visible within five days after the chemical treatment followed by semi-saturation and a decrease in the growth rate after the first week. After one month all the samples showed an oxide layer about 3 nm thick. The oxide thickness was correlated with leakage current degradation with time after surface preparation. PMID:27933118

  16. Defect measurements of CdZnTe detectors using I-DLTS, TCT, I-V, C-V and γ-ray spectroscopy

    Science.gov (United States)

    Gul, R.; Li, Z.; Rodriguez, R.; Keeter, K.; Bolotnikov, A.; James, R.

    2008-08-01

    In this work we measured the crystal defect levels and tested the performance of CdZnTe detectors by diverse methodologies, viz., Current Deep Level Transient Spectroscopy (I-DLTS), Transient Current Technique (TCT), Current and Capacitance versus Voltage measurements (I-V and C-V), and gamma-ray spectroscopy. Two important characteristics of I-DLTS technique for advancing this research are (1) it is applicable for high-resistivity materials (>106 Ω-cm), and, (2) the minimum temperature for measurements can be as low as 10 K. Such low-temperature capability is excellent for obtaining measurements at shallow levels. We acquired CdZnTe crystals grown by different techniques from two different vendors and characterized them for point defects and their response to photons. I-DLTS studies encompassed measuring the parameters of the defects, such as the energy levels in the band gap, the carrier capture cross-sections and their densities. The current induced by the laser-generated carriers and the charge collected (or number of electrons collected) were obtained using TCT that also provides the transport properties, such as the carrier life time and mobility of the detectors under study. The detector's electrical characteristics were explored, and its performance tested using I-V, C-V and gamma-ray spectroscopy.

  17. How big is an OMI pixel?

    Science.gov (United States)

    de Graaf, Martin; Sihler, Holger; Tilstra, Lieuwe G.; Stammes, Piet

    2016-08-01

    The Ozone Monitoring Instrument (OMI) is a push-broom imaging spectrometer, observing solar radiation backscattered by the Earth's atmosphere and surface. The incoming radiation is detected using a static imaging CCD (charge-coupled device) detector array with no moving parts, as opposed to most of the previous satellite spectrometers, which used a moving mirror to scan the Earth in the across-track direction. The field of view (FoV) of detector pixels is the solid angle from which radiation is observed, averaged over the integration time of a measurement. The OMI FoV is not quadrangular, which is common for scanning instruments, but rather super-Gaussian shaped and overlapping with the FoV of neighbouring pixels. This has consequences for pixel-area-dependent applications, like cloud fraction products, and visualisation.The shapes and sizes of OMI FoVs were determined pre-flight by theoretical and experimental tests but never verified after launch. In this paper the OMI FoV is characterised using collocated MODerate resolution Imaging Spectroradiometer (MODIS) reflectance measurements. MODIS measurements have a much higher spatial resolution than OMI measurements and spectrally overlap at 469 nm. The OMI FoV was verified by finding the highest correlation between MODIS and OMI reflectances in cloud-free scenes, assuming a 2-D super-Gaussian function with varying size and shape to represent the OMI FoV. Our results show that the OMPIXCOR product 75FoV corner coordinates are accurate as the full width at half maximum (FWHM) of a super-Gaussian FoV model when this function is assumed. The softness of the function edges, modelled by the super-Gaussian exponents, is different in both directions and is view angle dependent.The optimal overlap function between OMI and MODIS reflectances is scene dependent and highly dependent on time differences between overpasses, especially with clouds in the scene. For partially clouded scenes, the optimal overlap function was

  18. A 'Drift' algorithm for integrating vector polyline and DEM based on the spherical DQG

    Science.gov (United States)

    Wang, Jiaojiao; Wang, Lei; Cao, Wenmin; Zhao, Xuesheng

    2014-03-01

    The efficient integration method of vector and DEM data on a global scale is one of the important issues in the community of Digital Earth. Among the existing methods, geometry-based approach maintains the characteristics of vector data necessary for inquiry and analysis. However, the complexity of geometry-based approach, which needs lots of interpolation calculation, limits its applications greatly in the multi-source spatial data integration on a global scale. To overcome this serious deficiency, a novel 'drift' algorithm is developed based on the spherical Degenerate Quadtree Grid (DQG) on which the global DEMs data is represented. The main principle of this algorithm is that the vector node in a DQG cell can be moved to the cell corner-point without changing the visualization effects if the cell is smaller or equal to a pixel of screen. A detailed algorithm and the multi-scale operation steps are also presented. By the 'drift' algorithm, the vector polylines and DEM grids are integrated seamlessly, avoiding lots of interpolation calculating. Based on the approach described above, we have developed a computer program in platform OpenGL 3D API with VC++ language. In this experiment, USGS GTOPO30 DEM data and 1:1,000,000 DCW roads data sets in China area are selected. Tests have shown that time consumption of the 'drift' algorithm is only about 25% of that of the traditional ones, moreover, the mean error of drift operation on vector nodes can be controlled within about half a DQG cell. In the end, the conclusions and future works are also given.

  19. Barber's Point, Oahu, Hawaii Drift Card Study 2002-2004

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Drift cards were be released from Barber's Point, Oahu, approximately once a month during the two year span to get an idea of the distribution of card drift under...

  20. Exploring Genetic Drift and Natural Selection through a Simulation Activity.

    Science.gov (United States)

    Maret, Timothy J.; Rissing, Steven W.

    1998-01-01

    Reports on the development of a laboratory exercise that would allow students to explore the concept of genetic drift. Discusses the concept of genetic drift that is coincident with natural selection and that closely models the real world. (DDR)

  1. Drift-Scale THC Seepage Model

    Energy Technology Data Exchange (ETDEWEB)

    C.R. Bryan

    2005-02-17

    The purpose of this report (REV04) is to document the thermal-hydrologic-chemical (THC) seepage model, which simulates the composition of waters that could potentially seep into emplacement drifts, and the composition of the gas phase. The THC seepage model is processed and abstracted for use in the total system performance assessment (TSPA) for the license application (LA). This report has been developed in accordance with ''Technical Work Plan for: Near-Field Environment and Transport: Coupled Processes (Mountain-Scale TH/THC/THM, Drift-Scale THC Seepage, and Post-Processing Analysis for THC Seepage) Report Integration'' (BSC 2005 [DIRS 172761]). The technical work plan (TWP) describes planning information pertaining to the technical scope, content, and management of this report. The plan for validation of the models documented in this report is given in Section 2.2.2, ''Model Validation for the DS THC Seepage Model,'' of the TWP. The TWP (Section 3.2.2) identifies Acceptance Criteria 1 to 4 for ''Quantity and Chemistry of Water Contacting Engineered Barriers and Waste Forms'' (NRC 2003 [DIRS 163274]) as being applicable to this report; however, in variance to the TWP, Acceptance Criterion 5 has also been determined to be applicable, and is addressed, along with the other Acceptance Criteria, in Section 4.2 of this report. Also, three FEPS not listed in the TWP (2.2.10.01.0A, 2.2.10.06.0A, and 2.2.11.02.0A) are partially addressed in this report, and have been added to the list of excluded FEPS in Table 6.1-2. This report has been developed in accordance with LP-SIII.10Q-BSC, ''Models''. This report documents the THC seepage model and a derivative used for validation, the Drift Scale Test (DST) THC submodel. The THC seepage model is a drift-scale process model for predicting the composition of gas and water that could enter waste emplacement drifts and the effects of mineral

  2. LePix-A high resistivity, fully depleted monolithic pixel detector

    CERN Document Server

    Giubilato, P; Mugnier, H; Bisello, D; Marchioro, A; Snoeys, W; Denes, P; Pantano, D; Rousset, J; Mattiazzo, S; Kloukinas, K; Potenza, A; Rivetti, A; Chalmet, P

    2013-01-01

    The LePix project explores monolithic pixel sensors fabricated in a 90 nm CMOS technology built over a lightly doped substrate. This approach keeps the advantages usually offered by Monolithic Active Pixel Sensors (MAPS), like a low input capacitance, having a single piece detector and using a standard CMOS production line, and adds the benefit of charge collection by drift from a depleted region several tens of microns deep into the substrate, therefore providing an excellent signal to noise ratio and a radiation tolerance superior to conventional un-depleted MAPS. Such sensors are expected to offer significant cost savings and reduction of power consumption for the same performance, leading to the use of much less material in the detector (less cooling and less copper), addressing one of the main limitations of present day particle tracking systems. The latest evolution of the project uses detectors thinned down to 50 mu m to obtain back illuminated sensors operated in full depletion mode. By back processin...

  3. DMAPS: a fully depleted monolithic active pixel sensor - analog performance characterization

    CERN Document Server

    Havránek, Miroslav; Krüger, Hans; Fu, Yunan; Germic, Leonard; Kishishita, Tetsuichi; Obermann, Theresa; Wermes, Norbert

    2014-01-01

    Monolithic Active Pixel Sensors (MAPS) have been developed since the late 1990s based on silicon substrates with a thin epitaxial layer (thickness of 10-15 $\\mu$m) in which charge is collected on an electrode, albeit by disordered and slow diffusion rather than by drift in a directed electric field. As a consequence, the signal is small ($\\approx$ 1000 e$^-$) and the radiation tolerance is much below the LHC requirements by factors of 100 to 1000. In this paper we present the development of a fully Depleted Monolithic Active Pixel Sensors (DMAPS) based on a high resistivity substrate allowing the creation of a fully depleted detection volume. This concept overcomes the inherent limitations of charge collection by diffusion in the standard MAPS designs. We present results from a test chip EPCB01 designed in a commercial 150 nm CMOS technology. The technology provides a thin (50 $\\mu$m) high resistivity n-type silicon substrate as well as an additional deep p-well which allows to integrate full CMOS circuitry i...

  4. Silicon buried channels for pixel detector cooling

    Energy Technology Data Exchange (ETDEWEB)

    Boscardin, M., E-mail: boscardi@fbk.eu [Fondazione Bruno Kessler Trento, Via Sommarive 18, I-38123 Trento (Italy); Conci, P.; Crivellari, M.; Ronchin, S. [Fondazione Bruno Kessler Trento, Via Sommarive 18, I-38123 Trento (Italy); Bettarini, S. [Universitá di Pisa, L.go B. Pontecorvo 3, I-56127 Pisa (Italy); Istituto Nazionale di Fisica Nucleare, Sez. di Pisa, L.go B. Pontecorvo 3, I-56127 Pisa (Italy); Bosi, F. [Istituto Nazionale di Fisica Nucleare, Sez. di Pisa, L.go B. Pontecorvo 3, I-56127 Pisa (Italy)

    2013-08-01

    The support and cooling structures add important contributions to the thickness, in radiation length, of vertex detectors. In order to minimize the material budget of pixel sensors, we developed a new approach to integrate the cooling into the silicon devices. The microchannels are formed in silicon using isotropic SF{sub 6} plasma etching in a DRIE (deep reactive ion etcher) equipment. Due to their peculiar profiles, the channels can be sealed by a layer of a PECVD silicon oxide. We have realized on a silicon wafer microchannels with different geometries and hydraulic diameters. We describe the main fabrication steps of microchannels with focus on the channel definition. The experimental results are reported on the thermal characterization of several prototypes, using a mixture of glycol and water as a liquid coolant. The prototypes have shown high cooling efficiency and high-pressure breaking strength.

  5. Artificial Structural Color Pixels: A Review

    Science.gov (United States)

    Zhao, Yuqian; Zhao, Yong; Hu, Sheng; Lv, Jiangtao; Ying, Yu; Gervinskas, Gediminas; Si, Guangyuan

    2017-01-01

    Inspired by natural photonic structures (Morpho butterfly, for instance), researchers have demonstrated varying artificial color display devices using different designs. Photonic-crystal/plasmonic color filters have drawn increasing attention most recently. In this review article, we show the developing trend of artificial structural color pixels from photonic crystals to plasmonic nanostructures. Such devices normally utilize the distinctive optical features of photonic/plasmon resonance, resulting in high compatibility with current display and imaging technologies. Moreover, dynamical color filtering devices are highly desirable because tunable optical components are critical for developing new optical platforms which can be integrated or combined with other existing imaging and display techniques. Thus, extensive promising potential applications have been triggered and enabled including more abundant functionalities in integrated optics and nanophotonics. PMID:28805736

  6. CMB component separation in the pixel domain

    CERN Document Server

    Doroshkevich, A

    2010-01-01

    We show that the popular ILC approach is unstable in respect to the division of the sample of map pixels to the set of ``homogeneous'' subsamples. For suitable choice of such subsamples we can obtain the restored CMB signal with amplitudes ranged from zero to the amplitudes of the observed signal. We propose approach which allows us to obtain reasonable estimates of $C_\\ell$ at $\\ell\\leq 30$ and similar to WMAP $C_\\ell$ for larger $\\ell$. With this approach we reduce some anomalies of the WMAP results. In particular, our estimate of the quadrupole is well consistent to theoretical one, the effect of the ``axis of evil'' is suppressed and the symmetry of the north and south galactic hemispheres increases. This results can change estimates of quadrupole polarization and the redshift of reionization of the Universe. We propose also new simple approach which can improve WMAP estimates of high $\\ell$ power spectrum.

  7. Image Pixel Fusion for Human Face Recognition

    CERN Document Server

    Bhowmik, Mrinal Kanti; Nasipuri, Mita; Basu, Dipak Kumar; Kundu, Mahantapas

    2010-01-01

    In this paper we present a technique for fusion of optical and thermal face images based on image pixel fusion approach. Out of several factors, which affect face recognition performance in case of visual images, illumination changes are a significant factor that needs to be addressed. Thermal images are better in handling illumination conditions but not very consistent in capturing texture details of the faces. Other factors like sunglasses, beard, moustache etc also play active role in adding complicacies to the recognition process. Fusion of thermal and visual images is a solution to overcome the drawbacks present in the individual thermal and visual face images. Here fused images are projected into an eigenspace and the projected images are classified using a radial basis function (RBF) neural network and also by a multi-layer perceptron (MLP). In the experiments Object Tracking and Classification Beyond Visible Spectrum (OTCBVS) database benchmark for thermal and visual face images have been used. Compar...

  8. Operational Experience with the ALICE Pixel detector

    CERN Document Server

    Mastroserio, A.

    2017-01-01

    The Silicon Pixel Detector (SPD) constitutes the two innermost layers of the Inner Tracking System of the ALICE experiment and it is the closest detector to the interaction point. As a vertex detector, it has the unique feature of generating a trigger signal that contributes to the L0 trigger of the ALICE experiment. The SPD started collecting data since the very first pp collisions at LHC in 2009 and since then it has taken part in all pp, Pb-Pb and p-Pb data taking campaigns. This contribution will present the main features of the SPD, the detector performance and the operational experience, including calibration and optimization activities from Run 1 to Run 2.

  9. Irradiation and beam tests qualification for ATLAS IBL Pixel Modules.

    CERN Document Server

    Rubinskiy, Igor; The ATLAS collaboration

    2011-01-01

    The upgrade for the ATLAS detector will undergo different phases towards HL-LHC. The first upgrade for the Pixel Detector will consist in the construction of a new pixel layer which will be installed during the first shutdown of the LHC machine (foreseen for 2013-14). The new detector, called Insertable B-Layer (IBL), will be inserted between the existing pixel detector and a new (smaller radius) beam-pipe at a radius of 3.2 cm. The IBL will require the development of several new technologies to cope with increase of radiation or pixel occupancy and also to improve the physics performance which will be achieved by reduction of the pixel size and of the material budget. Two different promising Silicon sensor technologies (Planar n-in-n and 3D) are currently under investigation for the pixel detector. An overview of the sensor technologies qualification with particular emphasis on irradiation and beam tests will be presented.

  10. Irradiation and beam tests qualification for ATLAS IBL Pixel Modules

    CERN Document Server

    Rubinskiy, I

    2013-01-01

    The upgrade for the ATLAS detector will have different steps towards HL-LHC. The first upgrade for the Pixel Detector will consist in the construction of a new pixel layer which will be installed during the first shutdown of the LHC machine (foreseen for 2013–2014). The new detector, called Insertable B-Layer (IBL), will be inserted between the existing Pixel Detector and a new (smaller radius) beam-pipe at a radius of 33 mm. The IBL will require the development of several new technologies to cope with the increase in the radiation damage and the pixel occupancy and also to improve the physics performance, which will be achieved by reduction of the pixel size and of the material budget. Two different promising silicon sensor technologies (Planar n-in-n and 3D) are currently under investigation for the Pixel Detector. An overview of the sensor technologies' qualification with particular emphasis on irradiation and beam tests is presented.

  11. Irradiation and beam tests qualification for ATLAS IBL Pixel Modules

    CERN Document Server

    Rubinskiy, Igor

    2013-01-01

    The upgrade for the ATLAS detector will have different steps towards HL-LHC. The first upgrade for the Pixel Detector will consist in the construction of a new pixel layer which will be installed during the first shutdown of the LHC machine (foreseen for 2013-14). The new detector, called Insertable B-Layer (IBL), will be inserted between the existing pixel detector and a new (smaller radius) beam-pipe at a radius of 33 mm. The IBL will require the development of several new technologies to cope with the increase of the radiation damage and the pixel occupancy and also to improve the physics performance, which will be achieved by reduction of the pixel size and of the material budget. Two different promising silicon sensor technologies (Planar n-in-n and 3D) are currently under investigation for the pixel detector. An overview of the sensor technologies’ qualification with particular emphasis on irradiation and beam tests are presented.

  12. Super pixel-level dictionary learning for hyperspectral image classification

    Science.gov (United States)

    Zhao, Wei; Zhu, Wen; Liao, Bo; Fu, Xiangzheng

    2017-08-01

    This paper presents a superpixel-level dictionary learning model for hyperspectral data. The idea is to divide the hyperspectral image into a number of super-pixels by means of the super-pixel segmentation method. Each super-pixel is a spatial neighborhood called contextual group. That is, each pixel is represented using a linear combination of a few dictionary items learned from the train data, but since pixels inside a super-pixel are often consisting of the same materials, their linear combinations are constrained to use common items from the dictionary. To this end, the sparse coefficients of the context group have a common sparse pattern by using the joint sparse regularizer for dictionary learning. The sparse coefficients are then used for classification using linear support vector machines. The validity of the proposed method is experimentally verified on a real hyperspectral images.

  13. Electromagnetic drift modes in an inhomogeneous electron gas

    DEFF Research Database (Denmark)

    Shukla, P. K.; Pecseli, H. L.; Juul Rasmussen, Jens

    1986-01-01

    A pair of nonlinear equations is derived which describes the dynamics of the electromagnetic drift oscillations in a nonuniform magnetized electron gas. It is shown that the nonlinear electromagnetic drift modes can propagate in the form of dipole vortices......A pair of nonlinear equations is derived which describes the dynamics of the electromagnetic drift oscillations in a nonuniform magnetized electron gas. It is shown that the nonlinear electromagnetic drift modes can propagate in the form of dipole vortices...

  14. Longevity of Emplacement Drift Ground Support Materials

    Energy Technology Data Exchange (ETDEWEB)

    Tang, David H.

    2001-05-30

    The purpose of this analysis is to evaluate the factors affecting the longevity of emplacement drift ground support materials and to develop a basis for the selection of materials for ground support that will function throughout the preclosure period of a potential repository at Yucca Mountain. REV 01 ICN 01 of this analysis is developed in accordance with AP-3.10Q, Analyses and Models, Revision 2, ICN 4, and prepared in accordance with the Technical Work Plan for Subsurface Design Section FY 01 Work Activities (CRWMS M&O 2001a). The objective of this analysis is to update the previous analysis (CRWMS M&O 2000a) to account for related changes in the Ground Control System Description Document (CRWMS M&O 2000b), the Monitored Geologic Repository Project Description Document, which is included in the Requirements and Criteria for Implementing a Repository Design that can be Operated Over a Range of Thermal Modes (BSC 2001), input information, and in environmental conditions, and to provide updated information on candidate ground support materials. Candidate materials for ground support are carbon steel and cement grout. Steel is mainly used for steel sets, lagging, channel, rock bolts, and wire mesh. Cement grout is only considered in the case of grouted rock bolts. Candidate materials for the emplacement drift invert are carbon steel and granular natural material. Materials are evaluated for the repository emplacement drift environment based on the updated thermal loading condition and waste package design. The analysis consists of the following tasks: (1) Identify factors affecting the longevity of ground support materials for use in emplacement drifts. (2) Review existing documents concerning the behavior of candidate ground support materials during the preclosure period. (3) Evaluate impacts of temperature and radiation effects on mechanical and thermal properties of steel. Assess corrosion potential of steel at emplacement drift environment. (4) Evaluate factors

  15. Steganography on quantum pixel images using Shannon entropy

    Science.gov (United States)

    Laurel, Carlos Ortega; Dong, Shi-Hai; Cruz-Irisson, M.

    2016-07-01

    This paper presents a steganographical algorithm based on least significant bit (LSB) from the most significant bit information (MSBI) and the equivalence of a bit pixel image to a quantum pixel image, which permits to make the information communicate secretly onto quantum pixel images for its secure transmission through insecure channels. This algorithm offers higher security since it exploits the Shannon entropy for an image.

  16. CMOS monolithic pixel sensors research and development at LBNL

    Indian Academy of Sciences (India)

    D Contarato; J-M Bussat; P Denes; L Griender; T Kim; T Stezeberger; H Weiman; M Battaglia; B Hooberman; L Tompkins

    2007-12-01

    This paper summarizes the recent progress in the design and characterization of CMOS pixel sensors at LBNL. Results of lab tests, beam tests and radiation hardness tests carried out at LBNL on a test structure with pixels of various sizes are reported. The first results of the characterization of back-thinned CMOS pixel sensors are also reported, and future plans and activities are discussed.

  17. Data encoding efficiency in pixel detector readout with charge information

    CERN Document Server

    Garcia-Sciveres, Maurice

    2016-01-01

    The minimum number of bits needed for lossless readout of a pixel detector is calculated, in the regime of interest for particle physics where only a small fraction of pixels have a non-zero value per frame. This permits a systematic comparison of the readout efficiency of different encoding implementations. The calculation is compared to the bits used for by the FE-I4 pixel readout chip of the ATLAS experiment.

  18. Data encoding efficiency in pixel detector readout with charge information

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Sciveres, Maurice, E-mail: mgs@lbl.gov [Lawrence Berkeley National Laboratory, Berkeley, CA (United States); Wang, Xinkang [University of Chicago, Chicago, IL (United States)

    2016-04-11

    The average minimum number of bits needed for lossless readout of a pixel detector is calculated, in the regime of interest for particle physics where only a small fraction of pixels have a non-zero value per frame. This permits a systematic comparison of the readout efficiency of different encoding implementations. The calculation is compared to the number of bits used by the FE-I4 pixel readout chip of the ATLAS experiment.

  19. Drifting snow climate of the Antarctic and Greenland ice sheets

    NARCIS (Netherlands)

    Lenaerts, J.T.M.

    2013-01-01

    This study presents the drifting snow climate of the Earth's ice sheets, Antarctica and Greenland. For that purpose we use a regional atmospheric climate model, RACMO2. We included a routine that is able to calculate the drifting snow fluxes and accounts for the interaction between drifting snow on

  20. Drifting snow climate of the Antarctic and Greenland ice sheets

    NARCIS (Netherlands)

    Lenaerts, J.T.M.|info:eu-repo/dai/nl/314850163

    2013-01-01

    This study presents the drifting snow climate of the Earth's ice sheets, Antarctica and Greenland. For that purpose we use a regional atmospheric climate model, RACMO2. We included a routine that is able to calculate the drifting snow fluxes and accounts for the interaction between drifting snow on

  1. Hit efficiency study of CMS prototype forward pixel detectors

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Dongwook; /Johns Hopkins U.

    2006-01-01

    In this paper the author describes the measurement of the hit efficiency of a prototype pixel device for the CMS forward pixel detector. These pixel detectors were FM type sensors with PSI46V1 chip readout. The data were taken with the 120 GeV proton beam at Fermilab during the period of December 2004 to February 2005. The detectors proved to be highly efficient (99.27 {+-} 0.02%). The inefficiency was primarily located near the corners of the individual pixels.

  2. The FE-I4 pixel readout integrated circuit

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Sciveres, M., E-mail: mgarcia-sciveres@bl.gov [Lawrence Berkeley National Laboratory, Berkeley, CA (United States); Arutinov, D.; Barbero, M. [University of Bonn, Bonn (Germany); Beccherle, R. [Istituto Nazionale di Fisica Nucleare Sezione di Genova, Genova (Italy); Dube, S.; Elledge, D. [Lawrence Berkeley National Laboratory, Berkeley, CA (United States); Fleury, J. [Laboratoire de l' Accelerateur Lineaire, Orsay (France); Fougeron, D.; Gensolen, F. [Centre de Physique des Particules de Marseille, Marseille (France); Gnani, D. [Lawrence Berkeley National Laboratory, Berkeley, CA (United States); Gromov, V. [Nationaal Instituut voor Subatomaire Fysica, Amsterdam (Netherlands); Hemperek, T.; Karagounis, M. [University of Bonn, Bonn (Germany); Kluit, R. [Nationaal Instituut voor Subatomaire Fysica, Amsterdam (Netherlands); Kruth, A. [University of Bonn, Bonn (Germany); Mekkaoui, A. [Lawrence Berkeley National Laboratory, Berkeley, CA (United States); Menouni, M. [Centre de Physique des Particules de Marseille, Marseille (France); Schipper, J.-D. [Nationaal Instituut voor Subatomaire Fysica, Amsterdam (Netherlands)

    2011-04-21

    A new pixel readout integrated circuit denominated FE-I4 is being designed to meet the requirements of ATLAS experiment upgrades. It will be the largest readout IC produced to date for particle physics applications, filling the maximum allowed reticle area. This will significantly reduce the cost of future hybrid pixel detectors. In addition, FE-I4 will have smaller pixels and higher rate capability than the present generation of LHC pixel detectors. Design features are described along with simulation and test results, including low power and high rate readout architecture, mixed signal design strategy, and yield hardening.

  3. Rough differential equations with unbounded drift term

    Science.gov (United States)

    Riedel, S.; Scheutzow, M.

    2017-01-01

    We study controlled differential equations driven by a rough path (in the sense of T. Lyons) with an additional, possibly unbounded drift term. We show that the equation induces a solution flow if the drift grows at most linearly. Furthermore, we show that the semiflow exists assuming only appropriate one-sided growth conditions. We provide bounds for both the flow and the semiflow. Applied to stochastic analysis, our results imply strong completeness and the existence of a stochastic (semi)flow for a large class of stochastic differential equations. If the driving process is Gaussian, we can further deduce (essentially) sharp tail estimates for the (semi)flow and a Freidlin-Wentzell-type large deviation result.

  4. Clean Industrial Room for Drift Tube Assembling

    CERN Document Server

    Glonti, GL; Evtoukhovitch, P G; Kroa, G; Manz, A; Potrap, I N; Rihter, P; Stoletov, G D; Tskhadadze, E G; Chepurnov, V F; Chirkov, A V; Shelkov, G A

    2001-01-01

    Description of a clean industrial room for assembly of drift tubes for the muon spectrometer of the ATLAS experiment is presented. High quality specifications on the detectors to be produced demanded creation of a workplace with stable temperature and humidity, as well as minimum quantity of dust in the room. Checking of parameters of intra-room air during long period of continuous work has been confirmed correctness of the designed characteristics of the climatic system installed in the clean room. The room large volum (\\sim 190 m^3), the powerful and flexible climatic system, and simplicity of service allow assembling of detectors with length up to 5 m. Subsequent checking of functionality of the assembled detectors has shown high quality of assembling (the amount of rejected tubes does not exceed 2 %). It demonstrates conformity to the assembling quality requirements for mass production of drift chambers for the muon spectrometer.

  5. Gas sensor with attenuated drift characteristic

    Science.gov (United States)

    Chen, Ing-Shin [Danbury, CT; Chen, Philip S. H. [Bethel, CT; Neuner, Jeffrey W [Bethel, CT; Welch, James [Fairfield, CT; Hendrix, Bryan [Danbury, CT; Dimeo, Jr., Frank [Danbury, CT

    2008-05-13

    A sensor with an attenuated drift characteristic, including a layer structure in which a sensing layer has a layer of diffusional barrier material on at least one of its faces. The sensor may for example be constituted as a hydrogen gas sensor including a palladium/yttrium layer structure formed on a micro-hotplate base, with a chromium barrier layer between the yttrium layer and the micro-hotplate, and with a tantalum barrier layer between the yttrium layer and an overlying palladium protective layer. The gas sensor is useful for detection of a target gas in environments susceptible to generation or incursion of such gas, and achieves substantial (e.g., >90%) reduction of signal drift from the gas sensor in extended operation, relative to a corresponding gas sensor lacking the diffusional barrier structure of the invention

  6. Toroidal effects on drift wave turbulence

    Energy Technology Data Exchange (ETDEWEB)

    LeBrun, M.J.; Tajima, T.; Gray, M.G.; Furnish, G.; Horton, W.

    1992-09-23

    The universal drift instability and other drift instabilities driven by density and temperature gradients in a toroidal system are investigated in both linear and nonlinear regimes via particle simulation. Runs in toroidal and cylindrical geometry show dramatic differences in plasma behavior, primarily due to the toroidicity-induced coupling of rational surfaces through the poloidal mode number m. In the toroidal system studied, the eigenmodes are seen to possess (i) an elongated, nearly global radial extent (ii) a higher growth rate than in the corresponding cylindrical system, (iii) an eigenfrequency nearly constant with radius, (iv) a global temperature relaxation and enhancement of thermal heat conduction. Most importantly, the measured Xi shows an increase with radius and an absolute value on the order of that observed in experiment. On the basis of our observations, we argue that the increase in Xi with radius observed in experiment is caused by the global nature of heat convection in the presence of toroidicity-induced mode coupling.

  7. Nonlinear dynamics of resistive electrostatic drift waves

    DEFF Research Database (Denmark)

    Korsholm, Søren Bang; Michelsen, Poul; Pécseli, H.L.

    1999-01-01

    The evolution of weakly nonlinear electrostatic drift waves in an externally imposed strong homogeneous magnetic field is investigated numerically in three spatial dimensions. The analysis is based on a set of coupled, nonlinear equations, which are solved for an initial condition which is pertur......The evolution of weakly nonlinear electrostatic drift waves in an externally imposed strong homogeneous magnetic field is investigated numerically in three spatial dimensions. The analysis is based on a set of coupled, nonlinear equations, which are solved for an initial condition which...... is perturbed by a small amplitude incoherent wave-field. The initial evolution is exponential, following the growth of perturbations predicted by linear stability theory. The fluctuations saturate at relatively high amplitudes, by forming a pair of magnetic field aligned vortex-like structures of opposite...

  8. Velocity Distribution Measurement Using Pixel-Pixel Cross Correlation of Electrical Tomography

    Institute of Scientific and Technical Information of China (English)

    DENGXiang; PENGLihui; YAODanya; ZHANGBaofen

    2004-01-01

    Electrical tomography (ET) provides a novel means of visualizing the internal behavior of twophase flow in industrial process. Using a dual-sensingplane Electrical resistance tomography (ERT) or Electrical capacitance tomography (ECT) system, the raw data of two different section images can be acquired synchronously and the two images reflecting the inner medium distribution respectively can also be reconstructed by using imaging algorithm. Further, the analysis of pixel-pixel cross correlation is able to be setup and the measurement of velocity distribution of two-phase flow could be achieved. The principle is described in the paper. The FFT algorithm for gray value computation and cross correlation function calculation is also introduced. Some experimental results of velocity distribution measurement using pixelpixel cross correlation in vertical slug flow are presented.

  9. Some remarks on electronics for drift chambers

    CERN Document Server

    Verweij, H

    1973-01-01

    A brief outline of the required functions is given. Analogue and digital time measuring methods are compared. Amplifiers and current division circuits are discussed. A method for storage of analogue information, and the analogue shift register, is proposed. Functional block diagrams and more detailed information is given on complete systems, which are at present being developed at CERN. They allow the measurement of two orthogonal coordinates, one by the drift time, the other by the current division. (6 refs).

  10. Silicon drift detectors in the ALICE experiment

    CERN Document Server

    Bonvicini, V; Crescio, E; Giubellino, P; Hernández-Montoya, R; Kolojvari, A A; Mazza, G; Montaño-Zetina, L M; Nissinen, J; Nouais, D; Rashevsky, A; Rivetti, A; Tosello, F; Vacchi, A

    2000-01-01

    Silicon drift detectors (SDDs) are well suited to high-energy physics experiments with relatively low event rates. In particular SDDs will be used for the two intermediate layers of the Inner Tracking System of the ALICE experiment. Beam test results of linear SDD prototypes have shown a resolution of 40*30 mu m/sup 2/ and a cluster finding efficiency of essentially 100% with E=600 V/cm. (6 refs).

  11. The drift chambers of the NOMAD experiment

    Energy Technology Data Exchange (ETDEWEB)

    Anfreville, M.; Astier, P.; Authier, M.; Baldisseri, A.; Banner, M.; Besson, N.; Bouchez, J.; Castera, A.; Cloue, O.; Dumarchez, J. E-mail: jacques.dumarchez@cern.ch; Dumps, L.; Gangler, E.; Gosset, J.; Hagner, C.; Jollec, C.; Lachaud, C.; Letessier-Selvon, A.; Levy, J.-M.; Linssen, L.; Meyer, J.-P.; Ouriet, J.-P.; Passerieux, J.-P.; Margaley, T.P.T. Pedrol; Placci, A.; Pluquet, A.; Poinsignon, J.; Popov, B.A.; Rathouit, P.; Schahmaneche, K.; Stolarczyk, T.; Uros, V.; Vannucci, F.; Vo, M.K.; Zaccone, H

    2002-04-01

    We present a detailed description of the drift chambers used as an active target and a tracking device in the NOMAD experiment at CERN. The main characteristics of these chambers are a large area (3{center_dot}3 m{sup 2}), a self-supporting structure made of light composite materials and a low cost. A spatial resolution of 150 {mu}m has been achieved with a single hit efficiency of 97%.

  12. Unintended Positional Drift and Its Potential Solutions

    DEFF Research Database (Denmark)

    Nilsson, Niels Christian; Serafin, Stefania; Nordahl, Rolf

    2013-01-01

    Walking-In-Place interaction techniques seem particularly useful in relation to immersive virtual environments where the user's movement is greatly constrained by a limited physical space. However, current techniques may not be particularly useful in combination with head-mounted displays since...... many users unintentionally move forward while walking in place. We refer to this phenomenon accidental movement as Unintended Positional Drift. The poster presents evidence of the phenomenon's existence and subsequently discusses different design solutions which potentially could circumvent the problem....

  13. The drift table: designing for ludic engagement

    OpenAIRE

    2004-01-01

    The Drift Table is an electronic coffee table that displays slowly moving aerial photography controlled by the distribution of weight on its surface. It was designed to investigate our ideas about how technologies for the home could support ludic activities-that is, activities motivated by curiosity, exploration, and reflection rather than externally-defined tasks. The many design choices we made, for example to block or disguise utilitarian functionality, helped to articulate our emerging un...

  14. THERMAL DRIFT CHARACTERISTICS OF CAPACITIVE PRESSURE SENSORS

    OpenAIRE

    2016-01-01

    The capacitive pressure sensors based on silicon are characterized by their very high sensitivities and their low power consumption. Nevertheless, their thermal behavior remains more or less unpredictable because they can indicate very high thermal coefficients. The study of the thermal behavior of these sensors is essential to define the parameters that cause the output characteristics drift. In this study, we modeled the thermal behavior of this sensors, using Finite Element Analysis (FE...

  15. Effect of NOAA satellite orbital drift on AVHRR-derived phenological metrics

    Science.gov (United States)

    Ji, Lei; Brown, Jesslyn F.

    2017-10-01

    The U.S. Geological Survey (USGS) Earth Resources Observation and Science (EROS) Center routinely produces and distributes a remote sensing phenology (RSP) dataset derived from the Advanced Very High Resolution Radiometer (AVHRR) 1-km data compiled from a series of National Oceanic and Atmospheric Administration (NOAA) satellites (NOAA-11, -14, -16, -17, -18, and -19). Each NOAA satellite experienced orbital drift during its duty period, which influenced the AVHRR reflectance measurements. To understand the effect of the orbital drift on the AVHRR-derived RSP dataset, we analyzed the impact of solar zenith angle (SZA) on the RSP metrics in the conterminous United States (CONUS). The AVHRR weekly composites were used to calculate the growing-season median SZA at the pixel level for each year from 1989 to 2014. The results showed that the SZA increased towards the end of each NOAA satellite mission with the highest increasing rate occurring during NOAA-11 (1989-1994) and NOAA-14 (1995-2000) missions. The growing-season median SZA values (44°-60°) in 1992, 1993, 1994, 1999, and 2000 were substantially higher than those in other years (28°-40°). The high SZA in those years caused negative trends in the SZA time series, that were statistically significant (at α = 0.05 level) in 76.9% of the CONUS area. A pixel-based temporal correlation analysis showed that the phenological metrics and SZA were significantly correlated (at α = 0.05 level) in 4.1-20.4% of the CONUS area. After excluding the 5 years with high SZA (>40°) from the analysis, the temporal SZA trend was largely reduced, significantly affecting less than 2% of the study area. Additionally, significant correlation between the phenological metrics and SZA was observed in less than 7% of the study area. Our study concluded that the NOAA satellite orbital drift increased SZA, and in turn, influenced the phenological metrics. Elimination of the years with high median SZA reduced the influence of orbital drift

  16. Effect of NOAA satellite orbital drift on AVHRR-derived phenological metrics

    Science.gov (United States)

    Ji, Lei; Brown, Jesslyn

    2017-01-01

    The U.S. Geological Survey (USGS) Earth Resources Observation and Science (EROS) Center routinely produces and distributes a remote sensing phenology (RSP) dataset derived from the Advanced Very High Resolution Radiometer (AVHRR) 1-km data compiled from a series of National Oceanic and Atmospheric Administration (NOAA) satellites (NOAA-11, −14, −16, −17, −18, and −19). Each NOAA satellite experienced orbital drift during its duty period, which influenced the AVHRR reflectance measurements. To understand the effect of the orbital drift on the AVHRR-derived RSP dataset, we analyzed the impact of solar zenith angle (SZA) on the RSP metrics in the conterminous United States (CONUS). The AVHRR weekly composites were used to calculate the growing-season median SZA at the pixel level for each year from 1989 to 2014. The results showed that the SZA increased towards the end of each NOAA satellite mission with the highest increasing rate occurring during NOAA-11 (1989–1994) and NOAA-14 (1995–2000) missions. The growing-season median SZA values (44°–60°) in 1992, 1993, 1994, 1999, and 2000 were substantially higher than those in other years (28°–40°). The high SZA in those years caused negative trends in the SZA time series, that were statistically significant (at α = 0.05 level) in 76.9% of the CONUS area. A pixel-based temporal correlation analysis showed that the phenological metrics and SZA were significantly correlated (at α = 0.05 level) in 4.1–20.4% of the CONUS area. After excluding the 5 years with high SZA (>40°) from the analysis, the temporal SZA trend was largely reduced, significantly affecting less than 2% of the study area. Additionally, significant correlation between the phenological metrics and SZA was observed in less than 7% of the study area. Our study concluded that the NOAA satellite orbital drift increased SZA, and in turn, influenced the phenological metrics. Elimination of the years with high median SZA reduced the

  17. Correlated Energy Exchange in Drifting Sea Ice

    Directory of Open Access Journals (Sweden)

    A. Chmel

    2011-01-01

    Full Text Available The ice floe speed variations were monitored at the research camp North Pole 35 established on the Arctic ice pack in 2008. A three-month time series of measured speed values was used for determining changes in the kinetic energy of the drifting ice floe. The constructed energy distributions were analyzed by methods of nonextensive statistical mechanics based on the Tsallis statistics for open nonequilibrium systems, such as tectonic formations and drifting sea ice. The nonextensivity means the nonadditivity of externally induced energy changes in multicomponent systems due to dynamic interrelation of components having no structural links. The Tsallis formalism gives one an opportunity to assess the correlation between ice floe motions through a specific parameter, the so-called parameter of nonextensivity. This formalistic assessment of the actual state of drifting pack allows one to forecast some important trends in sea ice behavior, because the level of correlated dynamics determines conditions for extended mechanical perturbations in ice pack. In this work, we revealed temporal fluctuations of the parameter of nonextensivity and observed its maximum value before a large-scale sea ice fragmentation (faulting of consolidated sea ice. The correlation was not detected in fragmented sea ice where long-range interactions are weakened.

  18. Monitored Drift Chambers in the ATLAS Detector

    CERN Multimedia

    Herten, G

    Monitored Drift Chambers (MDT) are used in the ATLAS Detector to measure the momentum of high energy muons. They consist of drift tubes, which are filled with an Ar-CO2 gas mixture at 3 bar gas pressure. About 1200 drift chambers are required for ATLAS. They are up to 6 m long. Nevertheless the position of every wire needs to be known with a precision of 20 µm within a chamber. In addition, optical alignment sensors are required to measure the relative position of adjacent chambers with a precision of 30µm. This gigantic task seems impossible at first instance. Indeed it took many years of R&D to invent the right tools and methods before the first chamber could be built according to specifications. Today, at the time when 50% of the chambers have been produced, we are confident that the goal for ATLAS can be reached. The mechanical precision of the chambers could be verified with the x-ray tomograph at CERN. This ingenious device, developed for the MDT system, is able to measure the wire position insid...

  19. Ambipolar Drift Heating in Turbulent Molecular Clouds

    CERN Document Server

    Padoan, P; Nordlund, A A; Padoan, Paolo

    1999-01-01

    Although thermal pressure is unimportant dynamically in most molecular gas, the temperature is an important diagnostic of dynamical processes and physical conditions. This is the first of two papers on thermal equilibrium in molecular clouds. We present calculations of frictional heating by ion-neutral (or ambipolar) drift in three-dimensional simulations of turbulent, magnetized molecular clouds. We show that ambipolar drift heating is a strong function of position in a turbulent cloud, and its average value can be significantly larger than the average cosmic ray heating rate. The volume averaged heating rate per unit volume due to ambipolar drift, H_AD ~ |JxB|^2 ~ B^4/L_B^2, is found to depend on the rms Alfvenic Mach number, M_A, and on the average field strength, as H_AD ~ M_A^2^4. This implies that the typical scale of variation of the magnetic field, L_B, is inversely proportional to M_A, which we also demonstrate.

  20. Longevity of Emplacement Drift Ground Support Materials

    Energy Technology Data Exchange (ETDEWEB)

    D. Tang

    2000-01-07

    The purpose of this analysis is to evaluate the factors affecting the longevity of emplacement drift ground support materials and to develop a basis for selection of materials for ground support that will function throughout the preclosure period. The Development Plan (DP) for this analysis is given in CRWMS M&O (Civilian Radioactive Waste Management System Management and Operating Contractor) (1999a). The candidate materials for ground support are steel (carbon steel, ductile cast iron, galvanized steel, and stainless steel, etc.) and cement. Steel will mainly be used for steel sets, lagging, channels, rock bolts, and wire mesh. Cement usage is only considered in the case of grouted rock bolts. The candidate materials for the invert structure are steel and crushed rock ballast. The materials shall be evaluated for the repository emplacement drift environment under a specific thermal loading condition based on the proposed License Application Design Selection (LADS) design. The analysis consists of the following tasks: (1) Identify factors affecting the longevity of ground control materials for use in emplacement drifts. (2) Review existing documents concerning behavior of candidate ground control materials during the preclosure period. The major criteria to be considered for steel are mechanical and thermal properties, and durability, of which corrosion is the most important concern. (3) Evaluate the available results and develop recommendations for material(s) to be used.

  1. Social diffusion and global drift on networks

    Science.gov (United States)

    Sayama, Hiroki; Sinatra, Roberta

    2015-03-01

    We study a mathematical model of social diffusion on a symmetric weighted network where individual nodes' states gradually assimilate to local social norms made by their neighbors' average states. Unlike physical diffusion, this process is not state conservational and thus the global state of the network (i.e., sum of node states) will drift. The asymptotic average node state will be the average of initial node states weighted by their strengths. Here we show that, while the global state is not conserved in this process, the inner product of strength and state vectors is conserved instead, and perfect positive correlation between node states and local averages of their self-neighbor strength ratios always results in upward (or at least neutral) global drift. We also show that the strength assortativity negatively affects the speed of homogenization. Based on these findings, we propose an adaptive link weight adjustment method to achieve the highest upward global drift by increasing the strength-state correlation. The effectiveness of the method was confirmed through numerical simulations and implications for real-world social applications are discussed.

  2. Wind tunnel observations of drifting snow

    Science.gov (United States)

    Paterna, Enrico; Crivelli, Philip; Lehning, Michael

    2016-04-01

    Drifting snow has a significant impact on snow redistribution in mountains, prairies as well as on glaciers, ice shelves, and sea ice. In all these environments, the local mass balance is highly influenced by drifting snow. Understanding the dynamic of snow saltation is crucial to the accurate description of the process. We applied digital shadowgraphy in a cold wind tunnel to measure drifting snow over natural snow covers. The acquisition and evaluation of time-resolved shadowgraphy images allowed us to resolve a large part of the saltation layer. The technique has been successfully compared to the measurements obtained from a Snow Particle Counter, considered the most robust technique for snow mass-flux measurements so far. The streamwise snow transport is dominated by large-scale events. The vertical snow transport has a more equal distribution of energy across the scales, similarly to what is observed for the flow turbulence velocities. It is hypothesized that the vertical snow transport is a quantity that reflects the local entrainment of the snow crystals into the saltation layer while the streamwise snow transport results from the streamwise development of the trajectories of the snow particles once entrained, and therefore is rather a non-local quantity.

  3. Chemotaxis when bacteria remember: drift versus diffusion.

    Directory of Open Access Journals (Sweden)

    Sakuntala Chatterjee

    2011-12-01

    Full Text Available Escherichia coli (E. coli bacteria govern their trajectories by switching between running and tumbling modes as a function of the nutrient concentration they experienced in the past. At short time one observes a drift of the bacterial population, while at long time one observes accumulation in high-nutrient regions. Recent work has viewed chemotaxis as a compromise between drift toward favorable regions and accumulation in favorable regions. A number of earlier studies assume that a bacterium resets its memory at tumbles - a fact not borne out by experiment - and make use of approximate coarse-grained descriptions. Here, we revisit the problem of chemotaxis without resorting to any memory resets. We find that when bacteria respond to the environment in a non-adaptive manner, chemotaxis is generally dominated by diffusion, whereas when bacteria respond in an adaptive manner, chemotaxis is dominated by a bias in the motion. In the adaptive case, favorable drift occurs together with favorable accumulation. We derive our results from detailed simulations and a variety of analytical arguments. In particular, we introduce a new coarse-grained description of chemotaxis as biased diffusion, and we discuss the way it departs from older coarse-grained descriptions.

  4. Internal Clock Drift Estimation in Computer Clusters

    Directory of Open Access Journals (Sweden)

    Hicham Marouani

    2008-01-01

    Full Text Available Most computers have several high-resolution timing sources, from the programmable interrupt timer to the cycle counter. Yet, even at a precision of one cycle in ten millions, clocks may drift significantly in a single second at a clock frequency of several GHz. When tracing the low-level system events in computer clusters, such as packet sending or reception, each computer system records its own events using an internal clock. In order to properly understand the global system behavior and performance, as reported by the events recorded on each computer, it is important to estimate precisely the clock differences and drift between the different computers in the system. This article studies the clock precision and stability of several computer systems, with different architectures. It also studies the typical network delay characteristics, since time synchronization algorithms rely on the exchange of network packets and are dependent on the symmetry of the delays. A very precise clock, based on the atomic time provided by the GPS satellite network, was used as a reference to measure clock drifts and network delays. The results obtained are of immediate use to all applications which depend on computer clocks or network time synchronization accuracy.

  5. Giving cosmic redshift drift a whirl

    Science.gov (United States)

    Kim, Alex G.; Linder, Eric V.; Edelstein, Jerry; Erskine, David

    2015-03-01

    Redshift drift provides a direct kinematic measurement of cosmic acceleration but it occurs with a characteristic time scale of a Hubble time. Thus redshift observations with a challenging precision of 10-9 require a 10 year time span to obtain a signal-to-noise of 1. We discuss theoretical and experimental approaches to address this challenge, potentially requiring less observer time and having greater immunity to common systematics. On the theoretical side we explore allowing the universe, rather than the observer, to provide long time spans; speculative methods include radial baryon acoustic oscillations, cosmic pulsars, and strongly lensed quasars. On the experimental side, we explore beating down the redshift precision using differential interferometric techniques, including externally dispersed interferometers and spatial heterodyne spectroscopy. Low-redshift emission line galaxies are identified as having high cosmology leverage and systematics control, with an 8 h exposure on a 10-m telescope (1000 h of exposure on a 40-m telescope) potentially capable of measuring the redshift of a galaxy to a precision of 10-8 (few ×10-10). Low-redshift redshift drift also has very strong complementarity with cosmic microwave background measurements, with the combination achieving a dark energy figure of merit of nearly 300 (1400) for 5% (1%) precision on drift.

  6. Transient chaotic transport in dissipative drift motion

    Energy Technology Data Exchange (ETDEWEB)

    Oyarzabal, R.S. [Pós-Graduação em Ciências/Física, Universidade Estadual de Ponta Grossa, 84030-900, Ponta Grossa, PR (Brazil); Szezech, J.D. [Departamento de Matemática e Estatística, Universidade Estadual de Ponta Grossa, 84030-900, Ponta Grossa, PR (Brazil); Batista, A.M., E-mail: antoniomarcosbatista@gmail.com [Departamento de Matemática e Estatística, Universidade Estadual de Ponta Grossa, 84030-900, Ponta Grossa, PR (Brazil); Souza, S.L.T. de [Departamento de Física e Matemática, Universidade Federal de São João del Rei, 36420-000, Ouro Branco, MG (Brazil); Caldas, I.L. [Instituto de Física, Universidade de São Paulo, 05315-970, São Paulo, SP (Brazil); Viana, R.L. [Departamento de Física, Universidade Federal do Paraná, 81531-990, Curitiba, PR (Brazil); Sanjuán, M.A.F. [Departamento de Física, Universidad Rey Juan Carlos, Tulipán s/n, 28933 Móstoles, Madrid (Spain)

    2016-04-22

    Highlights: • We consider a situation for which a chaotic transient is present in the dynamics of the two-wave model with damping. • The damping in plasma models can be a way for study a realistic behavior of confinement due the collisional effect. • The escape time as a function of the damping obey a power-law scaling. • We have made a qualitative transport analysis with a simple model that can be useful for more complete models. • We have shown that the pattern of the basin of attraction depends on the damping parameter. - Abstract: We investigate chaotic particle transport in magnetised plasmas with two electrostatic drift waves. Considering dissipation in the drift motion, we verify that the removed KAM surfaces originate periodic attractors with their corresponding basins of attraction. We show that the properties of the basins depend on the dissipation and the space-averaged escape time decays exponentially when the dissipation increases. We find positive finite time Lyapunov exponents in dissipative drift motion, consequently the trajectories exhibit transient chaotic transport. These features indicate how the transient plasma transport depends on the dissipation.

  7. THERMAL DRIFT CHARACTERISTICS OF CAPACITIVE PRESSURE SENSORS

    Directory of Open Access Journals (Sweden)

    ABDELAZIZ BEDDIAF

    2016-03-01

    Full Text Available The capacitive pressure sensors based on silicon are characterized by their very high sensitivities and their low power consumption. Nevertheless, their thermal behavior remains more or less unpredictable because they can indicate very high thermal coefficients. The study of the thermal behavior of these sensors is essential to define the parameters that cause the output characteristics drift. In this study, we modeled the thermal behavior of this sensors, using Finite Element Analysis (FEA made in COMSOL. The model solved by COMSOL environment takes into account the entire sensor and thermal effects due to the temperature considering the materials’ properties, the geometric shape and also the heat transfer mechanisms. By COMSOL we determine how the temperature affects the sensor during the manufacturing process. For that end, we calculated the thermal drift of capacitance at rest, the thermal coefficients and we compared them with experimental results to validate our model. Further, we studied the thermal drift of sensor characteristics both at rest and under constant and uniform pressure. Further, our study put emphasis on the geometric influence parameters on these characteristics to optimize the sensor performance. Finally, this study allows us to predict the sensor behavior against temperature and to minimize this effect by optimizing the geometrical parameters.

  8. Pixel detector modules performance for ATLAS IBL and future pixel detectors

    CERN Document Server

    AUTHOR|(INSPIRE)INSPIRE-00355104; Pernegger, Heinz

    2015-11-06

    The ATLAS Detector is one of the four big particle physics experiments at CERN’s LHC. Its innermost tracking system consisted of the 3-Layer silicon Pixel Detector (~80M readout channels) in the first run (2010-2012). Over the past two years it was refurbished and equipped with new services as well as a new beam monitor. The major upgrade, however, was the Insertable B-Layer (IBL). It adds ~12M readout channels for improved vertexing, tracking robustness and b-tagging performance for the upcoming runs, before the high luminosity upgrade of the LHC will take place. This thesis covers two main aspects of Pixel detector performance studies: The main work was the planning, commissioning and operation of a test bench that meets the requirements of current pixel detector components. Each newly built ATLAS IBL stave was thoroughly tested, following a specifically developed procedure, and initially calibrated in that setup. A variety of production accompanying measurements as well as preliminary results after integ...

  9. Pixel Stability in HST Advanced Camera for Surveys Images

    Science.gov (United States)

    Borncamp, David; Grogin, Norman A.; Bourque, Matthew; Ogaz, Sara

    2017-06-01

    Excess thermal energy present in a Charged Coupled Device (CCD) can result in additional electrical current that is propagated into individual pixels in an exposure. This excess signal from the CCD itself can be persistently existent through multiple exposures and can have an adverse effect on the detectors science performance unless properly flagged and corrected for. The traditional way to correct for this extra charge is to take occasional long-exposure images with the camera shutter closed to map the location of these pixels. These images, generally referred to as “dark” images, allow for the measurement of the thermal-electron contamination present in each pixel of the CCD lattice. This "dark current" can then be subtracted from the science images by re-scaling the dark to the science exposure times. Pixels that have signal above a certain threshold are traditionally marked as “hot” and flagged in the data quality array. Many users will discard these pixels as being bad because of this extra current. However, these pixels may not be "bad" in the traditional sense that they cannot be reliably dark-subtracted. If these pixels are shown to be stable over an anneal period, the charge can be properly subtracted and the extra Poisson noise from this hot pixel’s dark current can be taken into account. Here we present the results of a pixel history study that analyzes every individual pixel of the Hubble Space Telescope's (HST) Advanced Camera for Surveys (ACS) Wide Field Channel (WFC) CCDs over time and allows pixels that were previously marked as bad to be brought back into the science image as a reliable pixel.

  10. Open-source sea ice drift algorithm for Sentinel-1 SAR imagery using a combination of feature tracking and pattern matching

    Science.gov (United States)

    Muckenhuber, Stefan; Sandven, Stein

    2017-08-01

    An open-source sea ice drift algorithm for Sentinel-1 SAR imagery is introduced based on the combination of feature tracking and pattern matching. Feature tracking produces an initial drift estimate and limits the search area for the consecutive pattern matching, which provides small- to medium-scale drift adjustments and normalised cross-correlation values. The algorithm is designed to combine the two approaches in order to benefit from the respective advantages. The considered feature-tracking method allows for an efficient computation of the drift field and the resulting vectors show a high degree of independence in terms of position, length, direction and rotation. The considered pattern-matching method, on the other hand, allows better control over vector positioning and resolution. The preprocessing of the Sentinel-1 data has been adjusted to retrieve a feature distribution that depends less on SAR backscatter peak values. Applying the algorithm with the recommended parameter setting, sea ice drift retrieval with a vector spacing of 4 km on Sentinel-1 images covering 400 km × 400 km, takes about 4 min on a standard 2.7 GHz processor with 8 GB memory. The corresponding recommended patch size for the pattern-matching step that defines the final resolution of each drift vector is 34 × 34 pixels (2.7 × 2.7 km). To assess the potential performance after finding suitable search restrictions, calculated drift results from 246 Sentinel-1 image pairs have been compared to buoy GPS data, collected in 2015 between 15 January and 22 April and covering an area from 80.5 to 83.5° N and 12 to 27° E. We found a logarithmic normal distribution of the displacement difference with a median at 352.9 m using HV polarisation and 535.7 m using HH polarisation. All software requirements necessary for applying the presented sea ice drift algorithm are open-source to ensure free implementation and easy distribution.

  11. Performance of a CdZnTe Radiation Detector Grown by a Low-pressure Bridgman Method

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Han Soo; Ha, Jang Ho; Lee, Kyu Hong [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2011-11-15

    CdZnTe (CZT) has been studied for many years as a material for room-temperature, high energy resolution gamma-ray detectors. Currently, prototypical detectors are now available for medical imaging, industrial tomograph and astrophysics in the world-wide. For this reason and next-generation gamma-ray detector, core-technology of CZT crystal growth and detector fabrication is much more crucial. CZT crystal was grown by Low-pressure Bridgman Method at Korea Atomic Energy Research Institute (KAERI) for room-temperature gamma-ray detector. In this study, performance of a CZT radiation detector such as I-V curve and energy resolution for gamma-ray was presented. We measured the I-V curve to define the resistivity of the grown CZT crystal. The electrometer, Keithley 6517A, was used to biasthe high voltage on the detector and read the leakage current. The measured I-V curve is shown in Fig. 3. Resistivity of the planar-type CZT detector, which didn't apply any passivation, was 7.8 x 10{sup 9} Ω·cm. The pulse height spectra was obtained with a CREMAT® CR-110 preamplifier, ORTEC® 572 amplifier, and 919 MCA. Figure 4 and 5 shows the pulse height spectra for 511 keV and 660 keV gamma-ray. The 10.0 % and 9.7 % energy resolutions for 511 keV and 662 keV gamma-ray, respectively, were obtained with the fabricated CZT detector. CZT single crystal was grown by low-pressure Bridgman method. Large domain of (1,1,1) crystalline face was obtained. Resistivity of 7.8 x 10{sup 9} Ω·cm of the grown CZT crystal, can be fabricated gamma-ray detector from the results. 10.0 % and 9.7 % of enrgy resolution for 511 keV and 662 keV gamma-ray, respectively, was also obtained. In the future work, passivation and types of detector, such as a Schottky-type, a Frisch Collor, and a coplanar electrode, will be studied to improve energy resolution.

  12. Development of new CdZnTe detectors for room-temperature high-flux radiation measurements.

    Science.gov (United States)

    Abbene, Leonardo; Gerardi, Gaetano; Raso, Giuseppe; Principato, Fabio; Zambelli, Nicola; Benassi, Giacomo; Bettelli, Manuele; Zappettini, Andrea

    2017-03-01

    Recently, CdZnTe (CZT) detectors have been widely proposed and developed for room-temperature X-ray spectroscopy even at high fluxes, and great efforts have been made on both the device and the crystal growth technologies. In this work, the performance of new travelling-heater-method (THM)-grown CZT detectors, recently developed at IMEM-CNR Parma, Italy, is presented. Thick planar detectors (3 mm thick) with gold electroless contacts were realised, with a planar cathode covering the detector surface (4.1 mm × 4.1 mm) and a central anode (2 mm × 2 mm) surrounded by a guard-ring electrode. The detectors, characterized by low leakage currents at room temperature (4.7 nA cm(-2) at 1000 V cm(-1)), allow good room-temperature operation even at high bias voltages (>7000 V cm(-1)). At low rates (200 counts s(-1)), the detectors exhibit an energy resolution around 4% FWHM at 59.5 keV ((241)Am source) up to 2200 V, by using commercial front-end electronics (A250F/NF charge-sensitive preamplifier, Amptek, USA; nominal equivalent noise charge of 100 electrons RMS). At high rates (1 Mcounts s(-1)), the detectors, coupled to a custom-designed digital pulse processing electronics developed at DiFC of University of Palermo (Italy), show low spectroscopic degradations: energy resolution values of 8% and 9.7% FWHM at 59.5 keV ((241)Am source) were measured, with throughputs of 0.4% and 60% at 1 Mcounts s(-1), respectively. An energy resolution of 7.7% FWHM at 122.1 keV ((57)Co source) with a throughput of 50% was obtained at 550 kcounts s(-1) (energy resolution of 3.2% at low rate). These activities are in the framework of an Italian research project on the development of energy-resolved photon-counting systems for high-flux energy-resolved X-ray imaging.

  13. In-Drift Precipitates/Salts Analysis

    Energy Technology Data Exchange (ETDEWEB)

    P. Mariner

    2001-01-10

    As directed by a written development plan (CRWMS M&O 1999a), an analysis of the effects of salts and precipitates on the repository chemical environment is to be developed and documented in an Analyses/Model Report (AMR). The purpose of this analysis is to assist Performance Assessment Operations (PAO) and the Engineered Barrier Performance Department in modeling the geochemical environment within a repository drift, thus allowing PAO to provide a more detailed and complete in-drift geochemical model abstraction and to answer the key technical issues (KTI) raised in the NRC Issue Resolution Status Report (IRSR) for the Evolution of the Near Field Environment (NFE) Revision 2 (NRC 1999). The purpose of this ICN is to qualify and document qualification of the AMR's technical products. The scope of this document is to develop a model of the processes that govern salt precipitation and dissolution and resulting water composition in the Engineered Barrier System (EBS). This model is developed to serve as a basis for the in-drift geochemical modeling work performed by PAO and is to be used in subsequent PAO analyses including the EBS physical and chemical model abstraction effort. However, the concepts may also apply to some near and far field geochemical processes and can have conceptual application within the unsaturated zone and saturated zone transport modeling efforts. The intended use of the model developed in this report is to estimate, within an appropriate level of confidence, the pH, chloride concentration, and ionic strength of water on the drip shield or other location within the drift during the post-closure period. These estimates are based on evaporative processes that are subject to a broad range of potential environmental conditions and are independent of the presence or absence of backfill. An additional intended use is to estimate the environmental conditions required for complete vaporization of water. The presence and composition of liquid water

  14. Ground Control for Emplacement Drifts for SR

    Energy Technology Data Exchange (ETDEWEB)

    Y. Sun

    2000-04-07

    This analysis demonstrates that a satisfactory ground control system can be designed for the Yucca Mountain site, and provides the technical basis for the design of ground support systems to be used in repository emplacement and non-emplacement drifts. The repository ground support design was based on analytical methods using acquired computer codes, and focused on the final support systems. A literature review of case histories, including the lessons learned from the design and construction of the ESF, the studies on the seismic damages of underground openings, and the use of rock mass classification systems in the ground support design, was conducted (Sections 6.3.4 and 6.4). This review provided some basis for determining the inputs and methodologies used in this analysis. Stability of the supported and unsupported emplacement and non-emplacement drifts was evaluated in this analysis. The excavation effects (i.e., state of the stress change due to excavation), thermal effects (i.e., due to heat output from waste packages), and seismic effects (i.e., from potential earthquake events) were evaluated, and stress controlled modes of failure were examined for two in situ stress conditions (k_0=0.3 and 1.0) using rock properties representing rock mass categories of 1 and 5. Variation of rock mass units such as the non-lithophysal (Tptpmn) and lithophysal (Tptpll) was considered in the analysis. The focus was on the non-lithophysal unit because this unit appears to be relatively weaker and has much smaller joint spacing. Therefore, the drift stability and ground support needs were considered to be controlled by the design for this rock unit. The ground support systems for both emplacement and non-emplacement drifts were incorporated into the models to assess their performance under in situ, thermal, and seismic loading conditions. Both continuum and discontinuum modeling approaches were employed in the analyses of the rock mass behavior and in the evaluation of the

  15. Reconnection and Spire Drift in Coronal Jets

    Science.gov (United States)

    Moore, Ronald; Sterling, Alphonse; Falconer, David

    2015-04-01

    It is observed that there are two morphologically-different kinds of X-ray/EUV jets in coronal holes: standard jets and blowout jets. In both kinds: (1) in the base of the jet there is closed magnetic field that has one foot in flux of polarity opposite that of the ambient open field of the coronal hole, and (2) in coronal X-ray/EUV images of the jet there is typically a bright nodule at the edge of the base. In the conventional scenario for jets of either kind, the bright nodule is a compact flare arcade, the downward product of interchange reconnection of closed field in the base with impacted ambient open field, and the upper product of this reconnection is the jet-outflow spire. It is also observed that in most jets of either kind the spire drifts sideways away from the bright nodule. We present the observed bright nodule and spire drift in an example standard jet and in two example blowout jets. With cartoons of the magnetic field and its reconnection in jets, we point out: (1) if the bright nodule is a compact flare arcade made by interchange reconnection, then the spire should drift toward the bright nodule, and (2) if the bright nodule is instead a compact flare arcade made, as in a filament-eruption flare, by internal reconnection of the legs of the erupting sheared-field core of a lobe of the closed field in the base, then the spire, made by the interchange reconnection that is driven on the outside of that lobe by the lobe’s internal convulsion, should drift away from the bright nodule. Therefore, from the observation that the spire usually drifts away from the bright nodule, we infer: (1) in X-ray/EUV jets of either kind in coronal holes the interchange reconnection that generates the jet-outflow spire usually does not make the bright nodule; instead, the bright nodule is made by reconnection inside erupting closed field in the base, as in a filament eruption, the eruption being either a confined eruption for a standard jet or a blowout eruption (as

  16. Airborne organophosphate pesticides drift in Mediterranean climate: The importance of secondary drift

    Science.gov (United States)

    Zivan, Ohad; Segal-Rosenheimer, Michal; Dubowski, Yael

    2016-02-01

    Pesticide application is a short-term air-pollution episode with near and far field effects due to atmospheric drift. In order to better evaluate resulting air concentrations in nearby communities following pesticide application, measurements of airborne pesticides were conducted at ∼70 m from field edge. This was done following three different application events of the organophosphate pesticide Chlorpyrifos in a persimmon orchard. Complementary information on larger spatial scale was obtained using CALPUFF modeling in which application and meteorological data was used to better evaluate dispersion patterns. Measurements indicated high airborne concentrations during application hours (few μg m-3 for 8 h average), which dropped to tens of ng m-3 in the following days. Measured atmospheric concentrations show that secondary drift (i.e., post-application drift) involves significant loads of pesticides and hence should not be ignored in exposure considerations. Furthermore, CALPUFF modeling revealed the complex dispersion pattern when weak winds prevailed, and showed that during the 24 h after application air concentrations reached levels above the hourly Texas effect screening level (0.1 μg m-3). Interestingly, weak winds on the night after application resulted in a secondary peak in measured and modeled air concentrations. Long exposure time (when secondary drift is considered) and concentrations measured following such common air-assisted orchard application, suggest pesticide drift may have health repercussions that are currently unknown, and emphasize the need for further epidemiological studies.

  17. Simplified Drift Analysis for Proving Lower Bounds in Evolutionary Computation

    DEFF Research Database (Denmark)

    Oliveto, Pietro S.; Witt, Carsten

    2011-01-01

    Drift analysis is a powerful tool used to bound the optimization time of evolutionary algorithms (EAs). Various previous works apply a drift theorem going back to Hajek in order to show exponential lower bounds on the optimization time of EAs. However, this drift theorem is tedious to read...... and to apply since it requires two bounds on the moment-generating (exponential) function of the drift. A recent work identifies a specialization of this drift theorem that is much easier to apply. Nevertheless, it is not as simple and not as general as possible. The present paper picks up Hajek’s line...... of thought to prove a drift theorem that is very easy to use in evolutionary computation. Only two conditions have to be verified, one of which holds for virtually all EAs with standard mutation. The other condition is a bound on what is really relevant, the drift. Applications show how previous analyses...

  18. Architectural modeling of pixel readout chips Velopix and Timepix3

    NARCIS (Netherlands)

    Poikela, T.; Plosila, J.; Westerlund, T.; Buytaert, J.; Campbell, M.; Llopart, X.; Plackett, R.; Wyllie, K.; van Beuzekom, M.; Gromov, V.; Kluit, R.; Zappon, F.; Zivkovic, V.; Brezina, C.; Desch, K.; Fang, X.; Kruth, A.

    2012-01-01

    We examine two digital architectures for front end pixel readout chips, Velopix and Timepix3. These readout chips are developed for tracking detectors in future high energy physics experiments. They must incorporate local intelligence in pixels for time-over-threshold measurement and sparse readout.

  19. Hybrid Pixel Detectors for gamma/X-ray imaging

    Science.gov (United States)

    Hatzistratis, D.; Theodoratos, G.; Zografos, V.; Kazas, I.; Loukas, D.; Lambropoulos, C. P.

    2015-09-01

    Hybrid pixel detectors are made by direct converting high-Z semi-insulating single crystalline material coupled to complementary-metal-oxide semiconductor (CMOS) readout electronics. They are attractive because direct conversion exterminates all the problems of spatial localization related to light diffusion, energy resolution, is far superior from the combination of scintillation crystals and photomultipliers and lithography can be used to pattern electrodes with very fine pitch. We are developing 2-D pixel CMOS ASICs, connect them to pixilated CdTe crystals with the flip chip and bump bonding method and characterize the hybrids. We have designed a series of circuits, whose latest member consists of a 50×25 pixel array with 400um pitch and an embedded controller. In every pixel a full spectroscopic channel with time tagging information has been implemented. The detectors are targeting Compton scatter imaging and they can be used for coded aperture imaging too. Hybridization using CMOS can overcome the limit put on pixel circuit complexity by the use of thin film transistors (TFT) in large flat panels. Hybrid active pixel sensors are used in dental imaging and other applications (e.g. industrial CT etc.). Thus X-ray imaging can benefit from the work done on dynamic range enhancement methods developed initially for visible and infrared CMOS pixel sensors. A 2-D CMOS ASIC with 100um pixel pitch to demonstrate the feasibility of such methods in the context of X-ray imaging has been designed.

  20. Novel integrated CMOS pixel structures for vertex detectors

    Energy Technology Data Exchange (ETDEWEB)

    Kleinfelder, Stuart; Bieser, Fred; Chen, Yandong; Gareus, Robin; Matis, Howard S.; Oldenburg, Markus; Retiere, Fabrice; Ritter, Hans Georg; Wieman, Howard H.; Yamamoto, Eugene

    2003-10-29

    Novel CMOS active pixel structures for vertex detector applications have been designed and tested. The overriding goal of this work is to increase the signal to noise ratio of the sensors and readout circuits. A large-area native epitaxial silicon photogate was designed with the aim of increasing the charge collected per struck pixel and to reduce charge diffusion to neighboring pixels. The photogate then transfers the charge to a low capacitance readout node to maintain a high charge to voltage conversion gain. Two techniques for noise reduction are also presented. The first is a per-pixel kT/C noise reduction circuit that produces results similar to traditional correlated double sampling (CDS). It has the advantage of requiring only one read, as compared to two for CDS, and no external storage or subtraction is needed. The technique reduced input-referred temporal noise by a factor of 2.5, to 12.8 e{sup -}. Finally, a column-level active reset technique is explored that suppresses kT/C noise during pixel reset. In tests, noise was reduced by a factor of 7.6 times, to an estimated 5.1 e{sup -} input-referred noise. The technique also dramatically reduces fixed pattern (pedestal) noise, by up to a factor of 21 in our tests. The latter feature may possibly reduce pixel-by-pixel pedestal differences to levels low enough to permit sparse data scan without per-pixel offset corrections.