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Sample records for cdte semiconductor detectors

  1. Improvement of the sensitivity of CdTe semiconductor detector in the high energy region

    International Nuclear Information System (INIS)

    Cadmium Telluride, CdTe, semiconductor detectors have sufficient band gap energy (1.47 eV) to use at room temperature, and their atomic number are so large (48 and 52) that their photon detection efficiency is more excellent than that of Si or Ge. Recently CdTe crystals have become easily available because of improvements in the crystal growth method. It is a useful X-ray detector, because it has good energy resolution and high efficiency at the full energy peak at less than a few hundred keV of incident photon energy. However, if the incident photon energy become higher, the efficiency of the full energy peak become worse, and it is very difficult to distinguish the full energy peak above 1 MeV, because the mobility of charge carriers in the CdTe crystal is much smaller than in Si and Ge and it is difficult to produce a larger volume element. In order to analyze the energy of several radioisotopes, it is necessary to improve the sensitivity of CdTe detectors in high energy regions. We have previously suggested a multilayered structure of CdTe elements. This paper describes a simulation and experiment to improve the efficiency of the full energy peak in the high energy region above 1 MeV. (author)

  2. Optimization of the SPECT systems based on a CdTe pixelated semiconductor detector using novel parallel-hole collimators

    International Nuclear Information System (INIS)

    Recently, many studies have been conducted using semiconductor materials to improve the system's sensitivity and spatial resolution. We are able to improve the spatial resolution by using a pixelated parallel-hole collimator with equal hole and pixel sizes. However, pixelated parallel-hole collimator appears to be problematic to manufacture collimator with small holes. Therefore, we presented an idea for a novel parallel-hole collimator with a cadmium telluride (CdTe) pixelated semiconductor detector. The purpose of this study was to evaluate and optimize the novel parallel-hole collimator geometric designs with CdTe pixelated semiconductor detector using GATE simulation program. This detector was modeled on PID 350 (Oy Ajat, Finland). We designed a novel parallel-hole collimator which consists of the two overlapped pixelated parallel-hole collimators. The overlap ratios of these collimators are 1:1, 1:2, 2:1, 1:3, 3:1, 1:4, and 4:1. To evaluate the performance of this system, system's sensitivity and spatial resolution were estimated. Additionally, image figure of merit (FOM) were calculated from the sensitivity and spatial resolution for the optimization of the novel parallel-hole collimator. According to the results, the measured averages of sensitivity using the 1:1, 1:2, 2:1, 1:3, 3:1, 1:4, and 4:1 ratio were 4.45, 7.56, 7.51, 12.76, 12.65, 20.01, and 19.90 times higher than that of the pixelated parallel-hole collimator, respectively, and the measured averages of spatial resolution were estimated various values depending on the source-to-collimator distances. Finally, the FOM using the pixelated parallel-hole collimator, 1:1, 1:2, 2:1, 1:3, 3:1, 1:4, and 4:1 ratio were 0.57, 0.73, 1.05, 1.13, 1.47, 1.62, 1.95, and 2.15, respectively. We designed a novel parallel-hole collimator with various ratios of collimator septal heights using a CdTe pixelated semiconductor detector. In conclusion, we successfully established a novel parallel-hole collimator

  3. Compound semiconductor GaAs and CdTe nuclear radiation detectors

    International Nuclear Information System (INIS)

    The preparation technology and characteristics of semi-insulating bulk single crystal GaAs surface-barrier detectors and single crystal CdTe surface-barrier detectors are described. The spectroscopic performance of the detectors for γ-rays from 125I, 241Am and 57Co at room temperature is given. The influence of the magnitude of forward resistive induced by ohmic contacts and of the surface passivation and aging in the fabrication process of surface-barrier detectors on the performance of the detectors is discussed. Finally, the influence of the fabrication technology of ohmic contacts and selected materials, such as Ni-Ge-Au and In-Ge-Ag, on the performance of the detectors is also studied

  4. Design of a high-resolution small-animal SPECT-CT system sharing a CdTe semiconductor detector

    Energy Technology Data Exchange (ETDEWEB)

    Ryu, Hyun-Ju; Lee, Young-Jin; Lee, Seung-Wan; Cho, Hyo-Min; Choi, Yu-Na; Kim, Hee-Joung [Yonsei University, Wonju (Korea, Republic of)

    2012-07-15

    A single photon emission computed tomography (SPECT) system with a co-registered X-y computed tomography (CT) system allows the convergence of functional information and morphologic information. The localization of radio pharmaceuticals on a SPECT can be enhanced by combining the SPECT with an anatomical modality, such as X-ray CT. Gamma-ray imaging for nuclear medicine devices and X-ray imaging systems for diagnostics has recently been developed based on semiconductor detectors, and semiconductor detector materials such as cadmium telluride (CdTe) or cadmium zinc telluride (CZT) are available for both X-ray and gamma-ray systems for small animal imaging. CdTe or CZT detectors provide strong absorption and high detection efficiency of high energy X-ray and gamma-ray photons because of their large atomic numbers. In this study, a pinhole collimator SPECT system sharing a cadmium telluride (CdTe) detector with a CT was designed. The GEANT4 application for tomographic emission (GATE) v.6.1 was used for the simulation. The pinhole collimator was designed to obtain a high spatial resolution of the SPECT system. The acquisition time for each projection was 40 seconds, and 60 projections were obtained for tomographic image acquisition. The reconstruction was performed using ordered subset expectation maximization (OS-EM) algorithms. The sensitivity and the spatial resolution were measured on the GATE simulation to evaluate the system characteristics. The spatial resolution of the system calculated from the FWHM of Gaussian fitted PSF curve was 0.69 mm, and the sensitivity of the system was measured to be 0.354 cps/kBq by using a Tc-99m point source of 1 MBq for 800 seconds. A phantom study was performed to verify the design of the dual imaging modality system. The system will be built as designed, and it can be applied as a pre-clinical imaging system.

  5. Design of a high-resolution small-animal SPECT-CT system sharing a CdTe semiconductor detector

    International Nuclear Information System (INIS)

    A single photon emission computed tomography (SPECT) system with a co-registered X-y computed tomography (CT) system allows the convergence of functional information and morphologic information. The localization of radio pharmaceuticals on a SPECT can be enhanced by combining the SPECT with an anatomical modality, such as X-ray CT. Gamma-ray imaging for nuclear medicine devices and X-ray imaging systems for diagnostics has recently been developed based on semiconductor detectors, and semiconductor detector materials such as cadmium telluride (CdTe) or cadmium zinc telluride (CZT) are available for both X-ray and gamma-ray systems for small animal imaging. CdTe or CZT detectors provide strong absorption and high detection efficiency of high energy X-ray and gamma-ray photons because of their large atomic numbers. In this study, a pinhole collimator SPECT system sharing a cadmium telluride (CdTe) detector with a CT was designed. The GEANT4 application for tomographic emission (GATE) v.6.1 was used for the simulation. The pinhole collimator was designed to obtain a high spatial resolution of the SPECT system. The acquisition time for each projection was 40 seconds, and 60 projections were obtained for tomographic image acquisition. The reconstruction was performed using ordered subset expectation maximization (OS-EM) algorithms. The sensitivity and the spatial resolution were measured on the GATE simulation to evaluate the system characteristics. The spatial resolution of the system calculated from the FWHM of Gaussian fitted PSF curve was 0.69 mm, and the sensitivity of the system was measured to be 0.354 cps/kBq by using a Tc-99m point source of 1 MBq for 800 seconds. A phantom study was performed to verify the design of the dual imaging modality system. The system will be built as designed, and it can be applied as a pre-clinical imaging system.

  6. Design of a high-resolution small-animal SPECT-CT system sharing a CdTe semiconductor detector

    Science.gov (United States)

    Ryu, Hyun-Ju; Lee, Young-Jin; Lee, Seung-Wan; Cho, Hyo-Min; Choi, Yu-Na; Kim, Hee-Joung

    2012-07-01

    A single photon emission computed tomography (SPECT) system with a co-registered X-y computed tomography (CT) system allows the convergence of functional information and morphologic information. The localization of radiopharmaceuticals on a SPECT can be enhanced by combining the SPECT with an anatomical modality, such as X-ray CT. Gamma-ray imaging for nuclear medicine devices and X-ray imaging systems for diagnostics has recently been developed based on semiconductor detectors, and semiconductor detector materials such as cadmium telluride (CdTe) or cadmium zinc telluride (CZT) are available for both X-ray and gamma-ray systems for small-animal imaging. CdTe or CZT detectors provide strong absorption and high detection efficiency of high energy X-ray and gamma-ray photons because of their large atomic numbers. In this study, a pinhole collimator SPECT system sharing a cadmium telluride (CdTe) detector with a CT was designed. The GEANT4 application for tomographic emission (GATE) v.6.1 was used for the simulation. The pinhole collimator was designed to obtain a high spatial resolution of the SPECT system. The acquisition time for each projection was 40 seconds, and 60 projections were obtained for tomographic image acquisition. The reconstruction was performed using ordered subset expectation maximization (OS-EM) algorithms. The sensitivity and the spatial resolution were measured on the GATE simulation to evaluate the system characteristics. The spatial resolution of the system calculated from the FWHM of Gaussian fitted PSF curve was 0.69 mm, and the sensitivity of the system was measured to be 0.354 cps/kBq by using a Tc-99m point source of 1 MBq for 800 seconds. A phantom study was performed to verify the design of the dual imaging modality system. The system will be built as designed, and it can be applied as a pre-clinical imaging system.

  7. 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.

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

    OpenAIRE

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

    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...

  9. CdTe and CdZnTe semiconductor gamma detectors equipped with ohmic contacts

    CERN Document Server

    Lachish, U

    1999-01-01

    Semiconductor gamma detectors, equipped with ohmic contacts, are uniform and fast response devices that are not sensitive to hole trapping. Gamma generated charges flow within the detector bulk towards the ohmic contacts, and induce additional charge flow from the contacts towards them. The additional flow stems from the fundamental principles of Poisson and the continuity equations. Electrons flow from the negative contacts towards the holes and recombine with them, therefore, they overcome hole trapping. The ohmic contact effect transforms the detector into a single carrier device. Good quality ohmic contact detectors are achieved from a crystal grown by standard methods, that initially has too many traps, by adjustment of the Fermi level position within the forbidden band. The device design and its principle of operation are discussed.

  10. Hard-X and gamma-ray imaging detector for astrophysics based on pixelated CdTe semiconductors

    Science.gov (United States)

    Gálvez, J.-L.; Hernanz, M.; Álvarez, L.; Artigues, B.; Ullán, M.; Lozano, M.; Pellegrini, G.; Cabruja, E.; Martínez, R.; Chmeissani, M.; Puigdengoles, C.

    2016-01-01

    Stellar explosions are astrophysical phenomena of great importance and interest. Instruments with high sensitivities are essential to perform detailed studies of cosmic explosions and cosmic accelerators. In order to achieve the needed performance, a hard-X and gamma-ray imaging detector with mm spatial resolution and large enough efficiency is required. We present a detector module which consists of a single CdTe crystal of 12.5 × 12.5mm 2 and 2mm thick with a planar cathode and with the anode segmented in an 11x11 pixel array with a pixel pitch of 1 mm attached to the readout chip. Two possible detector module configurations are considered: the so-called Planar Transverse Field (PTF) and the Parallel Planar Field (PPF). The combination of several modules in PTF or PPF configuration will achieve the desired performance of the imaging detector. The sum energy resolution of all pixels of the CdTe module measured at 122 keV and 356 keV is 3.8% and 2% respectively, in the following operating conditions: PPF irradiation, bias voltage -500 V and temperature -10̂ C.

  11. High efficiency pixellated CdTe detector

    International Nuclear Information System (INIS)

    Position sensitive detectors constructed from compound semiconductors (CdTe, CdZnTe, HgI2) are being developed for a variety of applications where high sensitivity and improved energy resolution are significant advantages over scintillator or gas based systems. We have investigated the possibility of using a CdTe detector array in a SPECT gamma camera that would require a high efficiency at 140 keV. The problem of worsening photopeak efficiencies in thick detectors (due to incomplete charge collection) makes it difficult to maintain a high efficiency which, ironically, is the primary reason for choosing a thicker detector. Recent research has shown that following a simple geometrical design criterion can greatly reduce this deleterious effect. This paper reports on the results from a small prototype pixellated array fabricated using this design. We verify the 'small pixel effect' for a detector thickness and pixel size significantly larger than those used in most other work. A 9-element detector (1 x 1 mm pixels, 4 mm thick) has been fabricated and characterized in terms of energy resolution, peak-to-valley ratio and detection efficiency. Testing of the detector in a fast pulse mode to obtain its high count rate response has also been performed. (orig.)

  12. COBRA - Double beta decay searches using CdTe detectors

    OpenAIRE

    Zuber, K.

    2001-01-01

    A new approach (called COBRA) for investigating double beta decay using CdTe (CdZnTe) semiconductor detectors is proposed. It follows the idea that source and detector are identical. This will allow simultaneous measurements of 5 $\\beta^-\\beta^-$ - and 4 $\\beta^+\\beta^+$ - emitters at once. Half-life limits for neutrinoless double beta decay of Cd-116 and Te-130 can be improved by more than one order of magnitude with respect to current limits and sensitivities on the effective Majorana neutr...

  13. Developments of gamma-ray imagers using CdTe semiconductors based on the analog ASIC technology

    International Nuclear Information System (INIS)

    Cadmium Telluride (CdTe) is one of the most promising semiconductor materials for hard X-ray and gamma-ray detection because of the high detection efficiency, and of the good energy resolution. Moreover, CdTe detectors with Schottky junction work as diode detectors, and show superior energy resolution. Based on the CdTe diode devices, we have developed CdTe pixel/strip imagers, and also realized a Si/CdTe Compton camera. These devices will be used for the Hard X-ray Imager (HXI) and the Soft Gamma-ray Detector (SGD) onboard ASTRO-H X-ray satellite to be launched in 2015. These developments are briefly reported in this article. We also describe our recent development of low-noise analog readout ASICs to be used for future development of CdTe gamma-ray imagers. (author)

  14. Time walk correction of CdTe detectors using depth sensing technique

    International Nuclear Information System (INIS)

    A digital timing method aiming to minimize the time walk caused by the depth-dependent pulse shape variations in CdTe detectors has been developed. Detector pulses are digitized at the preamplifier stage and a full digital process is carried out to deduce and correct the time walk according to the interaction depth. A time resolution of 6.52 ns FWHM at an energy threshold of 150 keV with a CdTe detector (10x10x1 mm3) is achieved, which is close to the intrinsic resolution of the detector. The method improves the time resolution with no loss of detection efficiency and it is easy to implement. It is confirmed that the slow mobility and the short lifetime of the holes are major obstacles for further improvement in the timing performance of the CdTe detectors. The method is applicable to any semiconductor detector.

  15. Fabrication of pixelated CdTe and CdZnTe radiation detectors

    International Nuclear Information System (INIS)

    Cadmium telluride (CdTe) and cadmium zinc telluride (CdZnTe) are compound semiconductor characterized by wide semiconducting band gap and high photon stopping power due to its high atomic number and density. The mobility-life time product (μ t product) for holes in the materials is smaller than that for electrons. Hence, the effect of trapping losses is more pronounced on holes than on electrons. The trapping losses for holes limit achievable energy resolutions for planar detectors. In this study, pixelated CdTe detectors and pixelated CdZnTe detectors were fabricated and tested by 662 KeV gamma-rays of 137Cs at room temperature. Electrodes were formed on both sides of CdTe crystals and CdZnTe crystals by vacuum evaporation of gold. For purpose of comparison, a planar CdTe detector and a planar CdZnTe detector were evaluated. Since the pixelated CdTe detectors and the pixelated CdZnTe detectors operated as a single-polarity charge sensing device, the obtained energy resolutions were significantly higher than those for the planar detectors. Further improvement of energy resolutions of the detectors will be achieved by optimizing electrode structures. (M. Suetake)

  16. The CdTe detector module and its imaging performance

    Energy Technology Data Exchange (ETDEWEB)

    Mori, Issei; Takayama, Takuzo; Motomura, Nobutoku [Toshiba Corp. Medical Systems Co., Otawara, Tochigi (Japan). Medical Systems R and D Center

    2001-12-01

    In recent years investigations into the application of semiconductor detector technology in gamma cameras have become active world-wide. The reason for this burst of activity is the expectation that the semiconductor-based gamma camera would outperform the conventional Anger-type gamma camera with a large scintillator and photomultipliers. Nevertheless, to date, it cannot be said that this expectation has been met. While most of the studies have used CZT (Cadmium Zinc Telluride) as the semiconductor material, we designed and fabricated an experimental detector module of CdTe (Cadmium Telluride). The module consists of 512 elements and its pixel pitch is 1.6 mm. We have evaluated its energy resolution, planar image performance, single photon emission computed tomography (SPECT) image performance and time resolution for coincidence detection. The average energy resolution was 5.5% FWHM at 140 keV. The intrinsic spatial resolution was 1.6 mm. The quality of the phantom images, both planar and SPECT, was visually superior to that of the Anger-type gamma camera. The quantitative assessment of SPECT images showed accuracy far better than that of the Anger-type camera. The coincidence time resolution was 8.6 ns. All measurement were done at room temperature, and the polarization effect that had been the biggest concern for CdTe was not significant. The results indicated that the semiconductor-based gamma camera is superior in performance to the Anger-type and has the possibility of being used as a positron emission computed tomography (PET) scanner. (author)

  17. The CdTe detector module and its imaging performance

    International Nuclear Information System (INIS)

    In recent years investigations into the application of semiconductor detector technology in gamma cameras have become active world-wide. The reason for this burst of activity is the expectation that the semiconductor-based gamma camera would outperform the conventional Anger-type gamma camera with a large scintillator and photomultipliers. Nevertheless, to date, it cannot be said that this expectation has been met. While most of the studies have used CZT (Cadmium Zinc Telluride) as the semiconductor material, we designed and fabricated an experimental detector module of CdTe (Cadmium Telluride). The module consists of 512 elements and its pixel pitch is 1.6 mm. We have evaluated its energy resolution, planar image performance, single photon emission computed tomography (SPECT) image performance and time resolution for coincidence detection. The average energy resolution was 5.5% FWHM at 140 keV. The intrinsic spatial resolution was 1.6 mm. The quality of the phantom images, both planar and SPECT, was visually superior to that of the Anger-type gamma camera. The quantitative assessment of SPECT images showed accuracy far better than that of the Anger-type camera. The coincidence time resolution was 8.6 ns. All measurement were done at room temperature, and the polarization effect that had been the biggest concern for CdTe was not significant. The results indicated that the semiconductor-based gamma camera is superior in performance to the Anger-type and has the possibility of being used as a positron emission computed tomography (PET) scanner. (author)

  18. Si, CdTe and CdZnTe radiation detectors for imaging applications

    OpenAIRE

    Schulman, Tom

    2006-01-01

    The structure and operation of CdTe, CdZnTe and Si pixel detectors based on crystalline semiconductors, bump bonding and CMOS technology and developed mainly at Oy Simage Ltd. And Oy Ajat Ltd., Finland for X- and gamma ray imaging are presented. This detector technology evolved from the development of Si strip detectors at the Finnish Research Institute for High Energy Physics (SEFT) which later merged with other physics research units to form the Helsinki Institute of Physics (HIP). General ...

  19. Development of CdTe radiation detectors and their applications

    International Nuclear Information System (INIS)

    We have been developing radiation detectors using cadmium telluride (CdTe), which has the high radiation absorption characteristic. The image pickup tube using polycrystalline CdTe thin film has been developed at the first stage. Furthermore, the X-ray imaging line sensor with high scanning speed and the radiation spectrometer with thermo-electric Peltier cooler were developed by using CdTe single crystal, which has high electric charge collection characteristics. At present, the energy discriminating photon counting radiation line sensors are developing. In this presentation, the feature of the detector using CdTe and their applications are described examples of development until now. (author)

  20. Layered semiconductor neutron detectors

    Science.gov (United States)

    Mao, Samuel S; Perry, Dale L

    2013-12-10

    Room temperature operating solid state hand held neutron detectors integrate one or more relatively thin layers of a high neutron interaction cross-section element or materials with semiconductor detectors. The high neutron interaction cross-section element (e.g., Gd, B or Li) or materials comprising at least one high neutron interaction cross-section element can be in the form of unstructured layers or micro- or nano-structured arrays. Such architecture provides high efficiency neutron detector devices by capturing substantially more carriers produced from high energy .alpha.-particles or .gamma.-photons generated by neutron interaction.

  1. Improvement of the energy resolution of CdTe detectors by pulse height correction from waveform

    OpenAIRE

    Kikawa, T.; Ichikawa, A. K.; Hiraki, T.; Nakaya, T.(Kyoto University, Department of Physics, Kyoto, Japan)

    2011-01-01

    Semiconductor detectors made of CdTe crystal have high gamma-ray detection efficiency and are usable at room temperature. However, the energy resolution of CdTe detectors for MeV gamma-rays is rather poor because of the significant hole trapping effect. We have developed a method to improve the energy resolution by correcting the pulse height using the waveform of the signal and achieved 2.0% (FWHM) energy resolution for 662keV gamma-rays. Best energy resolution was achieved at temperatures b...

  2. Improvement of the energy resolution of CdTe detectors by pulse height correction from waveform

    CERN Document Server

    Kikawa, T; Hiraki, T; Nakaya, T

    2011-01-01

    Semiconductor detectors made of CdTe crystal have high gamma-ray detection efficiency and are usable at room temperature. However, the energy resolution of CdTe detectors for MeV gamma-rays is rather poor because of the significant hole trapping effect. We have developed a method to improve the energy resolution by correcting the pulse height using the waveform of the signal and achieved 2.0% (FWHM) energy resolution for 662keV gamma-rays. Best energy resolution was achieved at temperatures between -10 degrees C and 0 degrees C.

  3. Evaluation of XRI-UNO CdTe detector for nuclear medical imaging

    International Nuclear Information System (INIS)

    Over the last two decades advances in semiconductor detector technology have reached the point where they are sufficiently sensitive to become an alternative to scintillators for high energy gamma ray detection for application in fields such as medical imaging. This paper assessed the Cadmium-Telluride (CdTe) XRI-UNO semiconductor detector produced by X-RAY Imatek for photon energies of interest in nuclear imaging. The XRI-UNO detector was found to have an intrinsic spatial resolution of <0.5mm and a high incident count rate capability up to at least 1680cps. The system spatial resolution, uniformity and sensitivity characteristics are also reported

  4. Counting efficiency of a CdTe detector

    International Nuclear Information System (INIS)

    The purpose of this work is to obtain some data about the energy dependence of the sensitivity of a CdTe detector in order to use it for a miniature dose rate meter. The intrinsic efficiencies of the CdTe detector were measured for several photon energies between 22 and 835 keV. The results showed the great dependence of the efficiency of the CdTe detector on photon energy, for example, the intrinsic efficiencies for the photons of 122 keV and 835 keV were 71% and 8.7% respectively. Some further problems were also presented and discussed. (author)

  5. Optimization of an ultra-high-resolution parallel-hole collimator for CdTe semiconductor SPECT system

    International Nuclear Information System (INIS)

    Recently, there has been an increase in the demand for semiconductor detectors in the field of nuclear medicine imaging. The development of semiconductor detectors using materials such as CdTe that allowed for improved spatial resolution greatly advanced the field. However, the pinhole collimator that allows for high spatial resolution compromises the sensitivity due to the small size of the hole. An improvement in both sensitivity and spatial resolution may be achieved by using a pixelated parallel-hole collimator where the hole and pixel sizes are the same. The purpose of this study was to optimize the design of a detector and collimator system to achieve excellent resolution and high sensitivity for a SPECT detector based on a CdTe detector. We performed a simulation study of the PID 350 (Ajat Oy Ltd., Finland) CdTe detector by using a Geant4 Application for Tomographic Emission (GATE). In addition to the above-mentioned pixelated parallel-hole collimator, we also designed a hexagonal parallel-hole collimator with similar hole size, and we evaluated the sensitivity and spatial resolution of each to determine which set-up was optimal for the PID 350 CdTe detector. Our results indicated that the average sensitivity and spatial resolution were 33.48% and 10.97% higher for the pixelated parallel-hole collimator than for the hexagonal parallel-hole collimator, respectively. We resolved a diameter of 0.5 mm in hot-rod phantom images with the pixelated parallel-hole collimator at a distance of 2 cm. Based on our results, we recommend the pixelated parallel-hole collimator for improving the sensitivity and spatial resolution of SPECT systems with CdTe semiconductor detectors.

  6. Application of CdTe (CdZnTe) detectors for radioactive waste characterization

    CERN Document Server

    Dovbnya, N A; Kutny, V E

    2002-01-01

    The radiation detectors based on wide-zone semiconductor CdTe (CdZnTe) monocrystals have promising advantages for their application in investigation (characterization) of radioactive waste. Among these advantages there are the wide range of photons flux and energy, high registration efficiency and satisfactory energy resolution without deep cooling of the detector. This report discusses the obtained data concerning radiation stability of detectors, influence of different conditions (filters, collimators, registration channel fill etc.) on their energy resolution in spectrometric regime, as well as a dependence of radionuclide identification accuracy on detector size.

  7. Radiation induced polarization in CdTe detectors

    Science.gov (United States)

    Vartsky, D.; Goldberg, M.; Eisen, Y.; Shamai, Y.; Dukhan, R.; Siffert, P.; Koebel, J. M.; Regal, R.; Gerber, J.

    1988-01-01

    Polarization induced by irradiation with intense gamma ray sources has been studied in chlorine-compensated CdTe detectors. The influence of several parameters, such as applied field strength, temperature and incident photon flux, on the polarization effect have been investigated. A relationship was found between the degree of polarization, detector efficiency and detector leakage current.

  8. Radiation induced polarization in CdTe detectors

    Energy Technology Data Exchange (ETDEWEB)

    Vartsky, D.; Goldberg, M.; Eisen, Y.; Shamai, Y.; Dukhan, R.; Siffert, P.; Koebel, J.M.; Regal, R.; Gerber, J.

    1988-01-15

    Polarization induced by irradiation with intense gamma ray sources has been studied in chlorine-compensated CdTe detectors. The influence of several parameters, such as applied field strength, temperature and incident photon flux, on the polarization effect have been investigated. A relationship was found between the degree of polarization, detector efficiency and detector leakage current.

  9. CdTe detector efficiency calibration using thick targets of pure and stable compounds

    International Nuclear Information System (INIS)

    Quantitative PIXE measurements require perfectly calibrated set-ups. Cooled CdTe detectors have good efficiency for energies above those covered by Si(Li) detectors and turn on the possibility of studying K X-rays lines instead of L X-rays lines for medium and eventually heavy elements, which is an important advantage in various cases, if only limited resolution systems are available in the low energy range. In this work we present and discuss spectra from a CdTe semiconductor detector covering the energy region from Cu (Kα1 = 8.047 keV) to U (Kα1 = 98.439 keV). Pure thick samples were irradiated with proton beams at the ITN 3.0 MV Tandetron accelerator in the High Resolution High Energy PIXE set-up. Results and the application to the study of a Portuguese Ossa Morena region Dark Stone sample are presented in this work.

  10. Signal processing for semiconductor detectors

    International Nuclear Information System (INIS)

    A balanced perspective is provided on the processing of signals produced by semiconductor detectors. The general problems of pulse shaping to optimize resolution with constraints imposed by noise, counting rate and rise time fluctuations are discussed

  11. Frontal IBICC study of the induced proton radiation damage in CdTe detectors

    Energy Technology Data Exchange (ETDEWEB)

    Pastuovic, Zeljko E-mail: pastu@rudjer.irb.hr; Jaksic, Milko

    2001-07-01

    Within a continuous international effort in developing the non-cryogenic semiconductor detectors for gamma ray spectroscopy, various wide gap materials were considered. With a best performance achieved, CdTe- and CdZnTe-based detectors become today widely accepted and commercially available. In addition to possible future use of such detectors for particle-induced gamma-ray emission (PIGE), nuclear microprobes are in recent years applied more as their characterisation tool using the ion beam-induced charge collection (IBICC) technique. Several CdTe detectors of 2x2x1 mm{sup 3} size were used in this study. On the basis of frontal IBICC measurements of the charge collection efficiency (CCE) distribution, the spectroscopy performance of detectors were measured. Further degradation of charge collection efficiency and the downward trend in peak position were studied by on-line irradiation of CdTe samples with 3 MeV protons up to 10{sup 10} p/cm{sup 2} radiation dose.

  12. Frontal IBICC study of the induced proton radiation damage in CdTe detectors

    Science.gov (United States)

    Pastuović, Željko; Jakšić, Milko

    2001-07-01

    Within a continuous international effort in developing the non-cryogenic semiconductor detectors for gamma ray spectroscopy, various wide gap materials were considered. With a best performance achieved, CdTe- and CdZnTe-based detectors become today widely accepted and commercially available. In addition to possible future use of such detectors for particle-induced gamma-ray emission (PIGE), nuclear microprobes are in recent years applied more as their characterisation tool using the ion beam-induced charge collection (IBICC) technique. Several CdTe detectors of 2×2×1 mm3 size were used in this study. On the basis of frontal IBICC measurements of the charge collection efficiency (CCE) distribution, the spectroscopy performance of detectors were measured. Further degradation of charge collection efficiency and the downward trend in peak position were studied by on-line irradiation of CdTe samples with 3 MeV protons up to 10 10 p/cm2 radiation dose.

  13. Recent Progress in CdTe and CdZnTe Detectors

    OpenAIRE

    Takahashi, Tadayui; Watanabe, Shin

    2001-01-01

    Cadmium telluride (CdTe) and cadmium zinc telluride (CdZnTe) have been regarded as promising semiconductor materials for hard X-ray and Gamma-ray detection. The high atomic number of the materials (Z_{Cd} =48, Z_{Te} =52) gives a high quantum efficiency in comparison with Si. The large band-gap energy (Eg ~ 1.5 eV) allows us to operate the detector at room temperature. However, a considerable amount of charge loss in these detectors produces a reduced energy resolution. This problem arises du...

  14. Semiconductor radiation detectors. Device physics

    International Nuclear Information System (INIS)

    Starting from basic principles, the author, whose own contributions to these developments have been significant, describes the rapidly growing field of modern semiconductor detectors used for energy and position measurement radiation. This development was stimulated by requirements in elementary particle physics where it has led to important scientific discoveries. It has now spread to many other fields of science and technology. The book is written in a didactic way and includes an introduction to semiconductor physics. The working principles of semiconductor radiation detectors are explained in an intuitive way, followed by formal quantitative analysis. Broad coverage is also given to electronic signal readout and to the subject of radiation damage. The book is the first to comprehensively cover the semiconductor radiation detectors currently in use. It is useful as a teaching guide and as a reference work for research and applications. (orig.)

  15. Radiation damage in semiconductor detectors

    Energy Technology Data Exchange (ETDEWEB)

    Kraner, H.W.

    1981-12-01

    A survey is presented of the important damage-producing interactions in semiconductor detectors and estimates of defect numbers are made for MeV protons, neutrons and electrons. Damage effects of fast neutrons in germanium gamma ray spectrometers are given in some detail. General effects in silicon detectors are discussed and damage constants and their relationship to leakage current is introduced.

  16. Digital pulse-shape processing for CdTe detectors

    International Nuclear Information System (INIS)

    CdTe detectors suffer from low photo-peak efficiency and poor energy resolution. These problems are due to the drift properties of charge carriers in CdTe where particularly the holes have small mobility and trapping time. This is reflected in the amplitude and the shape of the detector output. To improve this situation a digital method is introduced where a sampling ADC is used to make a detailed measurement of the time evolution of the pulse. The measured pulse shape is fitted with a model. For the detector under study a model taking hole trapping into account significantly improves the photo-peak efficiency. The description of the hole component is, however, not fully satisfactory since for pulses with a large hole contribution a broadening of the full-energy peak occurs. Allowing for inhomogeneities in the detector material within the model partially remedies this deficiency

  17. Digital pulse-shape processing for CdTe detectors

    CERN Document Server

    Bargholtz, C; Maartensson, L; Wachtmeister, S

    2001-01-01

    CdTe detectors suffer from low photo-peak efficiency and poor energy resolution. These problems are due to the drift properties of charge carriers in CdTe where particularly the holes have small mobility and trapping time. This is reflected in the amplitude and the shape of the detector output. To improve this situation a digital method is introduced where a sampling ADC is used to make a detailed measurement of the time evolution of the pulse. The measured pulse shape is fitted with a model. For the detector under study a model taking hole trapping into account significantly improves the photo-peak efficiency. The description of the hole component is, however, not fully satisfactory since for pulses with a large hole contribution a broadening of the full-energy peak occurs. Allowing for inhomogeneities in the detector material within the model partially remedies this deficiency.

  18. Digital pulse-shape processing for CdTe detectors

    Science.gov (United States)

    Bargholtz, Chr.; Fumero, E.; Mårtensson, L.; Wachtmeister, S.

    2001-09-01

    CdTe detectors suffer from low photo-peak efficiency and poor energy resolution. These problems are due to the drift properties of charge carriers in CdTe where particularly the holes have small mobility and trapping time. This is reflected in the amplitude and the shape of the detector output. To improve this situation a digital method is introduced where a sampling ADC is used to make a detailed measurement of the time evolution of the pulse. The measured pulse shape is fitted with a model. For the detector under study a model taking hole trapping into account significantly improves the photo-peak efficiency. The description of the hole component is, however, not fully satisfactory since for pulses with a large hole contribution a broadening of the full-energy peak occurs. Allowing for inhomogeneities in the detector material within the model partially remedies this deficiency.

  19. Digital pulse-shape processing for CdTe detectors

    Energy Technology Data Exchange (ETDEWEB)

    Bargholtz, Chr.; Fumero, E.; Maartensson, L. E-mail: martensson@physto.se; Wachtmeister, S

    2001-09-21

    CdTe detectors suffer from low photo-peak efficiency and poor energy resolution. These problems are due to the drift properties of charge carriers in CdTe where particularly the holes have small mobility and trapping time. This is reflected in the amplitude and the shape of the detector output. To improve this situation a digital method is introduced where a sampling ADC is used to make a detailed measurement of the time evolution of the pulse. The measured pulse shape is fitted with a model. For the detector under study a model taking hole trapping into account significantly improves the photo-peak efficiency. The description of the hole component is, however, not fully satisfactory since for pulses with a large hole contribution a broadening of the full-energy peak occurs. Allowing for inhomogeneities in the detector material within the model partially remedies this deficiency.

  20. Study of the spectrometric performances of monolithic CdTe CdZnTe gamma ray detectors

    OpenAIRE

    Gros D'Aillon, Eric

    2005-01-01

    Pixelated monolithic CdTe / CdZnTe semiconductor gamma ray detectors are brought to replace scintillation detectors for medical applications, notably for single photon emission computed tomography (SPECT). In addition to compactness, they present better spectrometric performances: energy resolution, detection efficiency, and spatial resolution. Moreover, the photons depth of interaction in the crystal can be measured. This work aimed in studying experimentally and by simulation the correlatio...

  1. Comparative study for small computer supported clearance determination with 131iodine hippuran using CdTe detectors

    International Nuclear Information System (INIS)

    With the goal to work out a simple, non-invasive method for the total clearance determination also for immobile patients, we carried out this clearance study with CdTe semi-conductor detectors. The 131iodine hippuran clearance determination was carried out on 69 patients in the nuclear medicine department of the Radiological Policlinic in the framework of a routine diagnosis with ambulant and stationary patients with a gamma camera and a connecting evaluation system. At the same time we recorded the shoulder curves using two CdTe semi-conductor detectors and deposited the data in a portable semi-conductor memory. Next the hypotheses for the routine use with the inclusion of commercially common small computers was worked out. The plasma disappearance curves which were recorded over the shoulder region were evaluated with a small computer according to the method of the modified Oberhausen tables and the Oberhausen formula. (orig./DG)

  2. Recent Progress in CdTe and CdZnTe Detectors

    CERN Document Server

    Takahashi, T; Takahashi, Tadayui; Watanabe, Shin

    2001-01-01

    Cadmium telluride (CdTe) and cadmium zinc telluride (CdZnTe) have been regarded as promising semiconductor materials for hard X-ray and Gamma-ray detection. The high atomic number of the materials (Z_{Cd} =48, Z_{Te} =52) gives a high quantum efficiency in comparison with Si. The large band-gap energy (Eg ~ 1.5 eV) allows us to operate the detector at room temperature. However, a considerable amount of charge loss in these detectors produces a reduced energy resolution. This problem arises due to the low mobility and short lifetime of holes. Recently, significant improvements have been achieved to improve the spectral properties based on the advances in the production of crystals and in the design of electrodes. In this overview talk, we summarize (1) advantages and disadvantages of CdTe and CdZnTe semiconductor detectors and (2) technique for improving energy resolution and photopeak efficiencies. Applications of these imaging detectors in future hard X-ray and Gamma-ray astronomy missions are briefly discus...

  3. Characterization of M-π-n CdTe pixel detectors coupled to HEXITEC readout chip

    Science.gov (United States)

    Veale, M. C.; Kalliopuska, J.; Pohjonen, H.; Andersson, H.; Nenonen, S.; Seller, P.; Wilson, M. D.

    2012-01-01

    Segmentation of the anode-side of an M-π-n CdTe diode, where the pn-junction is diffused into the detector bulk, produces large improvements in the spatial and energy resolution of CdTe pixel detectors. It has been shown that this fabrication technique produces very high inter-pixel resistance and low leakage currents are obtained by physical isolation of the pixels of M-π-n CdTe detectors. In this paper the results from M-π-n CdTe detectors stud bonded to a spectroscopic readout ASIC are reported. The CdTe pixel detectors have 250 μm pitch and an area of 5 × 5 mm2 with thicknesses of 1 and 2 mm. The polarization and energy resolution dependence of the M-π-n CdTe detectors as a function of detector thickness are discussed.

  4. Semiconductor detectors in nuclear and particle physics

    International Nuclear Information System (INIS)

    Semiconductor detectors for elementary particle physics and nuclear physics in the energy range above 1 GeV are briefly reviewed. In these two fields semiconductor detectors are used mainly for the precise position sensing. In a typical experiment, the position of a fast charged particle crossing a relatively thin semiconductor detector is measured. The position resolution achievable by semiconductor detectors is compared with the resolution achievable by gas filled position sensing detectors. Semiconductor detectors are divided into two groups: Classical semiconductor diode detectors and semiconductor memory detectors. Principles of the signal formation and the signal read-out for both groups of detectors are described. New developments of silicon detectors of both groups are reported

  5. 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 ...

  6. Digital signal processing for CdTe detectors using VXIbus data collection systems

    Energy Technology Data Exchange (ETDEWEB)

    Fukuda, Daiji; Takahashi, Hiroyuki; Kurahashi, Tomohiko; Iguchi, Tetsuo; Nakazawa, Masaharu

    1996-07-01

    Recently fast signal digitizing technique has been developed, and signal waveforms with very short time periods can be obtained. In this paper, we analyzed each measured pulse which was digitized by an apparatus of this kind, and tried to improve an energy resolution of a CdTe semiconductor detector. The result of the energy resolution for {sup 137}Cs 662 keV photopeak was 13 keV. Also, we developed a fast data collection system based on VXIbus standard, and the counting rate on this system was obtained about 50 counts per second. (author)

  7. CdTe and CdZnTe materials for room-temperature X-ray and gamma ray detectors

    Science.gov (United States)

    Eisen, Y.; Shor, A.

    1998-02-01

    Among the semiconductor materials of a wide band gap, CdTe and CdZnTe have attracted most attention as room-temperature X-ray and gamma-ray detectors. Suitable CdTe materials for nuclear detectors and, in particular, for spectrometers, have been developed over the past few decades and are mainly grown via the traveling heater method (THM). However, the manufacture of large homogeneous ingots at relatively low cost has not reached yet a proven stage. Cd 1- xZn xTe (CZT) materials, mainly grown via the high-pressure Bridgman (HPB) technique, possess several advantages over CdTe and appear to better approach the practicality of providing large volume X-ray and gamma-ray detectors at moderate costs. Continuing effort is still underway to improve the characteristics of both CdTe and CZT materials in order to achieve reproducible detectors for either low- and high-energy gamma rays. This review paper is divided into three parts: The first part describes different structural designs of detectors to improve their spectroscopic characteristics. These include hemispherical detectors, coplanar strip-electrode detectors and monolithic, two-dimensional segmented electrode arrays with pad sizes smaller than their thickness. This part will also describe various electronic methods to compensate for the poor charge collection of holes. The second part compares the characteristics of planar CdTe and CZT nuclear detectors containing metal contacts. Characteristics include: charge collection efficiencies for both electrons and holes indicated by the mobility-lifetime product, energy resolutions, leakage currents and robustness in field use. The third part is devoted to field uses of these detectors. Those include: X-ray fluorescent spectrometers, large volume spectrometers and a new generation nuclear gamma camera for medical diagnostics based on room-temperature solid-state spectrometers.

  8. Evaluation of a CdTe semiconductor based compact gamma camera for sentinel lymph node imaging

    Energy Technology Data Exchange (ETDEWEB)

    Russo, Paolo; Curion, Assunta S.; Mettivier, Giovanni; Esposito, Michela; Aurilio, Michela; Caraco, Corradina; Aloj, Luigi; Lastoria, Secondo [Dipartimento di Scienze Fisiche, Universita di Napoli Federico II, I-80126 Napoli (Italy) and Istituto Nazionale di Fisica Nucleare, Sezione di Napoli, I-80126 Napoli (Italy); Medicina Nucleare, Istituto Nazionale per lo Studio e la Cura dei Tumori, Fondazione G. Pascale, I-80131 Napoli (Italy)

    2011-03-15

    Purpose: The authors assembled a prototype compact gamma-ray imaging probe (MediPROBE) for sentinel lymph node (SLN) localization. This probe is based on a semiconductor pixel detector. Its basic performance was assessed in the laboratory and clinically in comparison with a conventional gamma camera. Methods: The room-temperature CdTe pixel detector (1 mm thick) has 256x256 square pixels arranged with a 55 {mu}m pitch (sensitive area 14.08x14.08 mm{sup 2}), coupled pixel-by-pixel via bump-bonding to the Medipix2 photon-counting readout CMOS integrated circuit. The imaging probe is equipped with a set of three interchangeable knife-edge pinhole collimators (0.94, 1.2, or 2.1 mm effective diameter at 140 keV) and its focal distance can be regulated in order to set a given field of view (FOV). A typical FOV of 70 mm at 50 mm skin-to-collimator distance corresponds to a minification factor 1:5. The detector is operated at a single low-energy threshold of about 20 keV. Results: For {sup 99m}Tc, at 50 mm distance, a background-subtracted sensitivity of 6.5x10{sup -3} cps/kBq and a system spatial resolution of 5.5 mm FWHM were obtained for the 0.94 mm pinhole; corresponding values for the 2.1 mm pinhole were 3.3x10{sup -2} cps/kBq and 12.6 mm. The dark count rate was 0.71 cps. Clinical images in three patients with melanoma indicate detection of the SLNs with acquisition times between 60 and 410 s with an injected activity of 26 MBq {sup 99m}Tc and prior localization with standard gamma camera lymphoscintigraphy. Conclusions: The laboratory performance of this imaging probe is limited by the pinhole collimator performance and the necessity of working in minification due to the limited detector size. However, in clinical operative conditions, the CdTe imaging probe was effective in detecting SLNs with adequate resolution and an acceptable sensitivity. Sensitivity is expected to improve with the future availability of a larger CdTe detector permitting operation at shorter

  9. Evaluation of a CdTe semiconductor based compact gamma camera for sentinel lymph node imaging

    International Nuclear Information System (INIS)

    Purpose: The authors assembled a prototype compact gamma-ray imaging probe (MediPROBE) for sentinel lymph node (SLN) localization. This probe is based on a semiconductor pixel detector. Its basic performance was assessed in the laboratory and clinically in comparison with a conventional gamma camera. Methods: The room-temperature CdTe pixel detector (1 mm thick) has 256x256 square pixels arranged with a 55 μm pitch (sensitive area 14.08x14.08 mm2), coupled pixel-by-pixel via bump-bonding to the Medipix2 photon-counting readout CMOS integrated circuit. The imaging probe is equipped with a set of three interchangeable knife-edge pinhole collimators (0.94, 1.2, or 2.1 mm effective diameter at 140 keV) and its focal distance can be regulated in order to set a given field of view (FOV). A typical FOV of 70 mm at 50 mm skin-to-collimator distance corresponds to a minification factor 1:5. The detector is operated at a single low-energy threshold of about 20 keV. Results: For 99mTc, at 50 mm distance, a background-subtracted sensitivity of 6.5x10-3 cps/kBq and a system spatial resolution of 5.5 mm FWHM were obtained for the 0.94 mm pinhole; corresponding values for the 2.1 mm pinhole were 3.3x10-2 cps/kBq and 12.6 mm. The dark count rate was 0.71 cps. Clinical images in three patients with melanoma indicate detection of the SLNs with acquisition times between 60 and 410 s with an injected activity of 26 MBq 99mTc and prior localization with standard gamma camera lymphoscintigraphy. Conclusions: The laboratory performance of this imaging probe is limited by the pinhole collimator performance and the necessity of working in minification due to the limited detector size. However, in clinical operative conditions, the CdTe imaging probe was effective in detecting SLNs with adequate resolution and an acceptable sensitivity. Sensitivity is expected to improve with the future availability of a larger CdTe detector permitting operation at shorter distances from the patient skin.

  10. Semiconductor X-ray detectors

    CERN Document Server

    Lowe, Barrie Glyn

    2014-01-01

    Identifying and measuring the elemental x-rays released when materials are examined with particles (electrons, protons, alpha particles, etc.) or photons (x-rays and gamma rays) is still considered to be the primary analytical technique for routine and non-destructive materials analysis. The Lithium Drifted Silicon (Si(Li)) X-Ray Detector, with its good resolution and peak to background, pioneered this type of analysis on electron microscopes, x-ray fluorescence instruments, and radioactive source- and accelerator-based excitation systems. Although rapid progress in Silicon Drift Detectors (SDDs), Charge Coupled Devices (CCDs), and Compound Semiconductor Detectors, including renewed interest in alternative materials such as CdZnTe and diamond, has made the Si(Li) X-Ray Detector nearly obsolete, the device serves as a useful benchmark and still is used in special instances where its large, sensitive depth is essential. Semiconductor X-Ray Detectors focuses on the history and development of Si(Li) X-Ray Detect...

  11. Development of a CdTe thermal neutron detector for neutron imaging

    International Nuclear Information System (INIS)

    A thin CdTe thermal neutron detector has been developed and its suitability for neutron imaging has been investigated. Simulations of the interaction of neutrons with a 0.5 mm-thick CdTe detector demonstrate the advantages of using 96 keV prompt gamma rays produced by neutron capture in 113Cd as a neutron event. Specifically, they provide a high spatial resolution and approximately the same detection efficiency as 558 keV prompt gamma rays, which are commonly used for detecting thermal neutrons in CdTe detectors. We fabricated a thin CdTe detector. Measurements using a 133Ba gamma-ray source revealed that the detector has a gamma-ray energy resolution of 3 keV at 80 keV, while measurements using a 252Cf neutron source demonstrated that the CdTe detector has good neutron/gamma ray discrimination.

  12. Pixelized M-pi-n CdTe detector coupled to Medipix2 readout chip

    CERN Document Server

    Kalliopuska, J; Penttila, R; Andersson, H; Nenonen, S; Gadda, A; Pohjonen, H; Vanttajac, I; Laaksoc, P; Likonen, J

    2011-01-01

    We have realized a simple method for patterning an M-pi-n CdTe diode with a deeply diffused pn-junction, such as indium anode on CdTe. The method relies on removing the semiconductor material on the anode-side of the diode until the physical junction has been reached. The pixelization of the p-type CdTe diode with an indium anode has been demonstrated by patterning perpendicular trenches with a high precision diamond blade and pulsed laser. Pixelization or microstrip pattering can be done on both sides of the diode, also on the cathode-side to realize double sided detector configuration. The article compares the patterning quality of the diamond blade process, pulsed pico-second and femto-second lasers processes. Leakage currents and inter-strip resistance have been measured and are used as the basis of the comparison. Secondary ion mass spectrometry (SIMS) characterization has been done for a diode to define the pn-junction depth and to see the effect of the thermal loads of the flip-chip bonding process. Th...

  13. CdTe detectors in medicine: a review of current applications and future perspectives

    International Nuclear Information System (INIS)

    Cadmium telluride (CdTe) semiconductor sensors have been evaluated for medical applications for 15 years owing to their high stopping power, convenient energy resolution and operating conditions at room temperature. Most of the applications herein reviewed concern medical imaging procedures, i.e., nuclear medicine, including positron emission tomography and radiology with computerized tomography (XCT). Despite their attractive physical characteristics, their preliminary commercial development has been slowed down in the early 80s because of technical problems, particularly when large arrays were considered, and because of the competition with the more available and less expensive scintillators or xenon chambers which are still mounted in most modern medical imaging systems. Nowadays the characteristics of new materials have allowed the development of restricted but more specific domains of CdTe medical applications i.e. miniaturized nuclear probes dedicated to per-operative tumor detection or ambulatory monitoring of physiological (renal, cardiac) functions and bone absorptiometry using either planar or miniature tomographic systems. Supported by the features and encouraged by the growing competition between ionising and non-ionizing imaging modalities (US, MRI), research work is presently conducted with a view to using CdTe detectors in XCT. (orig.)

  14. Optimization of a high-resolution collimator for a CdTe detector: Monte Carlo simulation studies

    International Nuclear Information System (INIS)

    parallel-hole collimator is better than that of the hexagonal parallel-hole collimator. In conclusion, we successfully established a high resolution gamma camera system with a pixelated parallel-hole collimator, and based on our results, we recommend using the pixelated parallel-hole collimator to improve the sensitivity and the spatial resolution of gamma camera systems with semiconductor detectors such as CdTe.

  15. A pixellated gamma-camera based on CdTe detectors clinical interests and performances

    CERN Document Server

    Chambron, J; Eclancher, B; Scheiber, C; Siffert, P; Hage-Ali, M; Regal, R; Kazandjian, A; Prat, V; Thomas, S; Warren, S; Matz, R; Jahnke, A; Karman, M; Pszota, A; Németh, L

    2000-01-01

    A mobile gamma camera dedicated to nuclear cardiology, based on a 15 cmx15 cm detection matrix of 2304 CdTe detector elements, 2.83 mmx2.83 mmx2 mm, has been developed with a European Community support to academic and industrial research centres. The intrinsic properties of the semiconductor crystals - low-ionisation energy, high-energy resolution, high attenuation coefficient - are potentially attractive to improve the gamma-camera performances. But their use as gamma detectors for medical imaging at high resolution requires production of high-grade materials and large quantities of sophisticated read-out electronics. The decision was taken to use CdTe rather than CdZnTe, because the manufacturer (Eurorad, France) has a large experience for producing high-grade materials, with a good homogeneity and stability and whose transport properties, characterised by the mobility-lifetime product, are at least 5 times greater than that of CdZnTe. The detector matrix is divided in 9 square units, each unit is composed ...

  16. Miniature hybrid preamplifier for CdTe detectors

    International Nuclear Information System (INIS)

    Aeronutronic Ford has developed a rugged, miniature, room temperature operable, gamma ray detector package containing a CdTe photon detector, a charge amplifier and a pulse shaper circuit. Photon detection efficiencies between 10 percent and 40 percent are achieved for various photon energies between 100 keV and 1000 keV in a detector area of .032 square inches. The resulting package weighs approximately 8 grams and occupies approximately 0.1 cubic inch. Prototypes have been tested for aging and temperature effects on gamma detection efficiency. The intended application of the device is calibrated gamma ray counting in a warm environment while subjected to high intensity acoustic and vibration stresses as well as very large linear accelerations

  17. A new method for evaluation of transport properties in CdTe and CZT detectors

    CERN Document Server

    Jung, M; Fougeres, P; Hage-Ali, M; Siffert, P

    1999-01-01

    The precise evaluation of transport properties of both electrons and holes in compound semiconductor detectors, like CdTe or CZT, is of great interest for the development of these devices. Although the electron behaviour can be measured in most cases, that of holes is much more difficult. Both alpha or gamma radiations, as well as conventional computer simulations, have shown their limits. In this paper, we present a new approach based on computer simulations, which are performed at various energies. This model will be applied on various kinds of materials. The results will be discussed in terms of sensitivity of the method, electronic noise level as well as electric field distribution within the detector.

  18. Performance optimization of CdTe and CdZnTe detectors for γ-spectrometry

    International Nuclear Information System (INIS)

    This study deals with room-temperature gamma spectrometry with CdTe and CdZnTe semiconductor detectors. The aim was the improvement of energy resolution and detection efficiency. Some different phenomena have been investigated. Electronic noise knowledge has enabled us to optimize the design of filtering. Charge transport induces signal shape uncertainty and the processing circuit has been adapted in order to account for these variations. Study and simulation of electrical current induction process has permitted the development of a new Frisch-grid based detection structure. We have reached 3% energy resolutions at 122 keV without detection efficiency loss. Finally, the remaining limits of detector performances have been estimated by focusing on gamma interaction phenomena and material non-uniformity problems. (author)

  19. Hybrid anode for semiconductor radiation detectors

    Science.gov (United States)

    Yang, Ge; Bolotnikov, Aleksey E; Camarda, Guiseppe; Cui, Yonggang; Hossain, Anwar; Kim, Ki Hyun; James, Ralph B

    2013-11-19

    The present invention relates to a novel hybrid anode configuration for a radiation detector that effectively reduces the edge effect of surface defects on the internal electric field in compound semiconductor detectors by focusing the internal electric field of the detector and redirecting drifting carriers away from the side surfaces of the semiconductor toward the collection electrode(s).

  20. Characterization inconsistencies in CdTe and CZT gamma-ray detectors

    International Nuclear Information System (INIS)

    In the past few years, significant developments in cadmium telluride (CdTe) and cadmium zinc telluride (CZT) semiconductor materials have taken place with respect to both quality and yield. Many of the more recent developments have occurred in the area of CZT crystal growth. This has resulted in an explosion of interest in the use of these materials in ambient temperature gamma-ray detectors. Most, if not all, of the manufacturers of CdTe and CZT have acquired government funding to continue research in development and applications, indicating the importance of these improvements in material quality. We have examined many detectors, along with the accompanying manufacturer's data, and it has become apparent that a clear standard does not exist by which each manufacturer characterizes the performance of their material. Result is a wide variety of performance claims that have no basis for comparison and normally cannot be readily reproduced. This paper first supports our observations and then proposes a standard that all manufacturers and users of these materials may use for characterization

  1. Wide-range plutonium isotopic analysis with CDTE detector

    Energy Technology Data Exchange (ETDEWEB)

    Vo, Duc T.; Russo, P. A. (Phyllis A.)

    2001-01-01

    Nondestructive analysis (NDA) techniques applied to bulk nuclear materials (NM) are important for nuclear safeguards and material control because of timeliness, cost-effectiveness and containment integrity. The common NDA techniques, calorimetry and neutron coincidence counting, require knowledge of the isotopic composition of the material quantitative interpretation of these measurements. Gamma-ray spectroscopy with high-resolution detectors is a well-developed NDA technique for isotopics. The use of intrinsic germanium detectors cooled to cryogenic temperatures for isotopic measurements is sometimes difficult or even impossible because of severe access limitations with the sensitive, heavy detectors. Highly portable isotopics measurements are needed for in-situ verification of bulk NM quantities or, in many cases, for measurements of holdup quantities. This paper summarizes the gamma-ray measurements with a new, portable CdTe detector. It also presents the detailed results of the wide-range isotopic analysis of plutonium with FRAM v4, the first results of this kind for a non-cryogenic detector.

  2. Semiconductors detectors: basics principals, fabrication and repair

    International Nuclear Information System (INIS)

    The fabrication and repairing techniques of semiconductor detectors, are described. These methods are shown in the way they are applied by the semiconductor detector laboratory of the KFA-Julich, where they have been developed during the last 15 years. The history of the semiconductor detectors is presented here, being also described the detector fabrication experiences inside Brazil. The key problems of manufacturing are raised. In order to understand the fabrication and repairing techniques the working principles of these detectors, are described. The cases in which worked during the stay in the KFA-Julich, particularly the fabrication of a plane Ge (Li) detector, with side entry, and the repair of a coaxial Ge (Li) is described. The vanguard problems being researched in Julich are also described. Finally it is discussed a timetable for the semiconductor detector laboratory of the UFRJ, which laboratory is in the mounting stage now. (Author)

  3. Gamma spectrometric characterization of various CdTe and CdZnTe detectors

    CERN Document Server

    Arlt, R; Sumah, P

    1999-01-01

    CdZnTe and CdTe detectors are now used by the Department of Safeguards of the International Atomic Energy Agency in significant numbers. To prepare, plan and support various verification methods, their properties must be well characterized and understood. In this paper we present some of the results which were obtained with large volume hemispheric CdZnTe detectors and high-resolution CdTe detectors.

  4. Miniature semiconductor detectors for in vivo dosimetry

    International Nuclear Information System (INIS)

    Silicon mini-semiconductor detectors are found in wide applications for in vivo personal dosimetry and dosimetry and Micro-dosimetry of different radiation oncology modalities. These applications are based on integral and spectroscopy modes of metal oxide semiconductor field effect transistor and silicon p-n junction detectors. The advantages and limitations of each are discussed. (authors)

  5. Semiconductor High-Energy Radiation Scintillation Detector

    OpenAIRE

    Kastalsky, A.; Luryi, S.; Spivak, B

    2006-01-01

    We propose a new scintillation-type detector in which high-energy radiation produces electron-hole pairs in a direct-gap semiconductor material that subsequently recombine producing infrared light to be registered by a photo-detector. The key issue is how to make the semiconductor essentially transparent to its own infrared light, so that photons generated deep inside the semiconductor could reach its surface without tangible attenuation. We discuss two ways to accomplish this, one based on d...

  6. Characterisation of vapour phase grown CdTe and (Cd,Zn)Te for detector applications

    CERN Document Server

    Fiederle, M; Rogalla, M; Meinhardt, J; Ludwig, J; Runge, K; Benz, W

    1999-01-01

    The growth of CdTe from the vapour phase offers several improvements in crystal quality and homogeneity. CdTe and (Cd, Zn)Te were grown by the modified Markov technique. The transport properties and the detector performance are given and compared to melt grown material. (author)

  7. Performance evaluation of three-dimensional position-sensitive CdTe detector blocks for an ultra-high resolution brain PET scanner

    International Nuclear Information System (INIS)

    We have developed an ultra-high resolution human brain positron emission tomography (PET) scanner with the resolution of less than 1 mm FWHM, in which cadmium telluride (CdTe) semiconductor detectors were used. As the detector of the scanner, we have developed a two-dimensional position-sensitive CdTe detector (2D-PSD) which was developed in our previous study. The 2D-PSD can detect gamma rays with a position resolution of approximately 1.2 mm. We developed a three-dimensional position-sensitive CdTe detector block (3D-PSD block) by stacking 80 2D-PSDs which were connected to subsequent circuits (amplifiers, analog to digital converters, and other data processing circuits). We constructed an ultra-high resolution semiconductor brain PET gantry placing the ten 3D-PSD blocks in decagonal arrangement. In this paper, we checked all 2D-PSDs and classified their performance. As the results, we confirmed that our 3D-PSD blocks can be used to the ultra-high resolution human brain PET. We made a circuit to reduce the dead time due to restoration from polarization phenomena in CdTe detector and we could stabilize count rates. (author)

  8. Position-sensitive CdTe detector using improved crystal growth method

    Science.gov (United States)

    1988-09-01

    The feasibility of developing a position-sensitive CdTe detector array for astronomical observations in the hard X-ray, soft gamma ray region is demonstrated. In principle, it was possible to improve the resolution capability for imaging measurements in this region by orders of magnitude over what is now possible through the use of CdTe detector arrays. The objective was to show that CdTe crystals of the quality, size and uniformity required for this application can be obtained with a new high pressure growth technique. The approach was to fabricate, characterize and analyze a 100 element square array and several single-element detectors using crystals from the new growth process. Results show that detectors fabricated from transversely sliced, 7 cm diameter wafers of CdTe exhibit efficient counting capability and a high degree of uniformity over their entire areas. A 100 element square array of 1 sq mm detectors was fabricated and operated.

  9. Semiconductor High-Energy Radiation Scintillation Detector

    CERN Document Server

    Kastalsky, A; Spivak, B

    2006-01-01

    We propose a new scintillation-type detector in which high-energy radiation produces electron-hole pairs in a direct-gap semiconductor material that subsequently recombine producing infrared light to be registered by a photo-detector. The key issue is how to make the semiconductor essentially transparent to its own infrared light, so that photons generated deep inside the semiconductor could reach its surface without tangible attenuation. We discuss two ways to accomplish this, one based on doping the semiconductor with shallow impurities of one polarity type, preferably donors, the other by heterostructure bandgap engineering. The proposed semiconductor scintillator combines the best properties of currently existing radiation detectors and can be used for both simple radiation monitoring, like a Geiger counter, and for high-resolution spectrography of the high-energy radiation. The most important advantage of the proposed detector is its fast response time, about 1 ns, essentially limited only by the recombi...

  10. CdTe and HgI2 crystals and detectors: present state and future

    International Nuclear Information System (INIS)

    After recalling the main properties of CdTe and HgI2 crystals from which the characteristics of these detectors will arise, the fabrication cycle is analysed at its various stages. The results at present achieved on CdTe and HgI2 detectors are analysed with a number of concrete applications in view such as medium power (0-200 keV) X and γ spectrometry, localisation of γ photons and solid ionisation chambers

  11. Preparation and characterization of thin films of electrodeposited CdTe semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Soliman, M.; Elgamal, M. [Alexandria University (Egypt). Institute of Graduate Studies and Research; Kashyout, A.B. [Mubarak City for Scientific Research and Technological Applications, Alexandria (Egypt); Shabana, M. [Alexandria University (Egypt). Faculty of Engineering

    2001-07-01

    Thin films of CdTe semiconductors were prepared by electrodeposition technique in aqueous solutions. The deposition mechanism was investigated by cyclic voltammetry. The potential regions for the formation of the n-CdTe and p-CdTe films were determined. The structure, composition and morphology characteristics of as-deposited thin films of CdTe grown on SnO{sub 2}/glass and CdS/SnO{sub 2}/glass were investigated by XRD, EDAX and SEM techniques. The optical properties were measured to determine the absorption coefficient and band gap values. The as-deposited CdTe films grown on SnO{sub 2}/glass contained free Te while those grown on CdS/SnO{sub 2}/glass did not contain this phase. The CdTe has the cubic structure with strong (111) orientation. The EDAX analysis showed a nearly stoichiometric Cd:Te ratio. The band gap has a value of 1.48 eV, which is in a good accordance with those reported in the literature. The effect of annealing at 350 and 400{sup o}C after, CdCI{sub 2} treatment on the structure and morphology was also examined. (author)

  12. Time walk correction of CdTe detectors using depth sensing technique

    OpenAIRE

    Nakhostin, M; Walker, PM; Sellin, PJ

    2010-01-01

    A digital timing method aiming to minimize the time walk caused by the depth-dependent pulse shape variations in CdTe detectors has been developed. Detector pulses are digitized at the preamplifier stage and a full digital process is carried out to deduce and correct the time walk according to the interaction depth. A time resolution of 6.52 ns FWHM at an energy threshold of 150 keV with a CdTe detector (10×10×1 mm3) is achieved, which is close to the intrinsic resolution of the detector. The...

  13. A pixellated γ-camera based on CdTe detectors clinical interests and performances

    Science.gov (United States)

    Chambron, J.; Arntz, Y.; Eclancher, B.; Scheiber, Ch; Siffert, P.; Hage Hali, M.; Regal, R.; Kazandjian, A.; Prat, V.; Thomas, S.; Warren, S.; Matz, R.; Jahnke, A.; Karman, M.; Pszota, A.; Nemeth, L.

    2000-07-01

    A mobile gamma camera dedicated to nuclear cardiology, based on a 15 cm×15 cm detection matrix of 2304 CdTe detector elements, 2.83 mm×2.83 mm×2 mm, has been developed with a European Community support to academic and industrial research centres. The intrinsic properties of the semiconductor crystals - low-ionisation energy, high-energy resolution, high attenuation coefficient - are potentially attractive to improve the γ-camera performances. But their use as γ detectors for medical imaging at high resolution requires production of high-grade materials and large quantities of sophisticated read-out electronics. The decision was taken to use CdTe rather than CdZnTe, because the manufacturer (Eurorad, France) has a large experience for producing high-grade materials, with a good homogeneity and stability and whose transport properties, characterised by the mobility-lifetime product, are at least 5 times greater than that of CdZnTe. The detector matrix is divided in 9 square units, each unit is composed of 256 detectors shared in 16 modules. Each module consists in a thin ceramic plate holding a line of 16 detectors, in four groups of four for an easy replacement, and holding a special 16 channels integrated circuit designed by CLRC (UK). A detection and acquisition logic based on a DSP card and a PC has been programmed by Eurorad for spectral and counting acquisition modes. Collimators LEAP and LEHR from commercial design, mobile gantry and clinical software were provided by Siemens (Germany). The γ-camera head housing, its general mounting and the electric connections were performed by Phase Laboratory (CNRS, France). The compactness of the γ-camera head, thin detectors matrix, electronic readout and collimator, facilitates the detection of close γ sources with the advantage of a high spatial resolution. Such an equipment is intended to bedside explorations. There is a growing clinical requirement in nuclear cardiology to early assess the extent of an

  14. A pixellated γ-camera based on CdTe detectors clinical interests and performances

    International Nuclear Information System (INIS)

    A mobile gamma camera dedicated to nuclear cardiology, based on a 15 cmx15 cm detection matrix of 2304 CdTe detector elements, 2.83 mmx2.83 mmx2 mm, has been developed with a European Community support to academic and industrial research centres. The intrinsic properties of the semiconductor crystals - low-ionisation energy, high-energy resolution, high attenuation coefficient - are potentially attractive to improve the γ-camera performances. But their use as γ detectors for medical imaging at high resolution requires production of high-grade materials and large quantities of sophisticated read-out electronics. The decision was taken to use CdTe rather than CdZnTe, because the manufacturer (Eurorad, France) has a large experience for producing high-grade materials, with a good homogeneity and stability and whose transport properties, characterised by the mobility-lifetime product, are at least 5 times greater than that of CdZnTe. The detector matrix is divided in 9 square units, each unit is composed of 256 detectors shared in 16 modules. Each module consists in a thin ceramic plate holding a line of 16 detectors, in four groups of four for an easy replacement, and holding a special 16 channels integrated circuit designed by CLRC (UK). A detection and acquisition logic based on a DSP card and a PC has been programmed by Eurorad for spectral and counting acquisition modes. Collimators LEAP and LEHR from commercial design, mobile gantry and clinical software were provided by Siemens (Germany). The γ-camera head housing, its general mounting and the electric connections were performed by Phase Laboratory (CNRS, France). The compactness of the γ-camera head, thin detectors matrix, electronic readout and collimator, facilitates the detection of close γ sources with the advantage of a high spatial resolution. Such an equipment is intended to bedside explorations. There is a growing clinical requirement in nuclear cardiology to early assess the extent of an infarct

  15. Semiconductor high-energy radiation scintillation detector

    Energy Technology Data Exchange (ETDEWEB)

    Kastalsky, A. [University at Stony Brook, ECE Department and NY State Center for Advanced Sensor Technology, Stony Brook, NY 11794-2350 (United States); Luryi, S. [University at Stony Brook, ECE Department and NY State Center for Advanced Sensor Technology, Stony Brook, NY 11794-2350 (United States)]. E-mail: serge.luryi@stonybrook.edu; Spivak, B. [Department of Physics, University of Washington, Seattle, WA 98195 (United States)

    2006-09-15

    We propose a new scintillation-type detector in which high-energy radiation generates electron-hole pairs in a direct-gap semiconductor material that subsequently recombine producing infrared light to be registered by a photo-detector. The key issue is how to make the semiconductor essentially transparent to its own infrared light, so that photons generated deep inside the semiconductor could reach its surface without tangible attenuation. We discuss two ways to accomplish this, one based on doping the semiconductor with shallow impurities of one polarity type, preferably donors, the other by heterostructure bandgap engineering. The proposed semiconductor scintillator combines the best properties of currently existing radiation detectors and can be used for both simple radiation monitoring, like a Geiger counter, and for high-resolution spectrography of the high-energy radiation. An important advantage of the proposed detector is its fast response time, about 1 ns, essentially limited only by the recombination time of minority carriers. Notably, the fast response comes without any degradation in brightness. When the scintillator is implemented in a qualified semiconductor material (such as InP or GaAs), the photo-detector and associated circuits can be epitaxially integrated on the scintillator slab and the structure can be stacked-up to achieve virtually any desired absorption capability.

  16. Rise and plasma times in semiconductor detectors

    International Nuclear Information System (INIS)

    The use of the rise time of the pulse from a semiconductor detector as a measure of the decay time of the plasma produced by a heavily ionising particle is discussed. Taking a simple model for plasma decay, conditions are developed under which the plasma decay time can be validity determined in this way. Both partially and totally depleted detectors are considered. (orig.)

  17. Semiconductor detectors with proximity signal readout

    International Nuclear Information System (INIS)

    Semiconductor-based radiation detectors are routinely used for the detection, imaging, and spectroscopy of x-rays, gamma rays, and charged particles for applications in the areas of nuclear and medical physics, astrophysics, environmental remediation, nuclear nonproliferation, and homeland security. Detectors used for imaging and particle tracking are more complex in that they typically must also measure the location of the radiation interaction in addition to the deposited energy. In such detectors, the position measurement is often achieved by dividing or segmenting the electrodes into many strips or pixels and then reading out the signals from all of the electrode segments. Fine electrode segmentation is problematic for many of the standard semiconductor detector technologies. Clearly there is a need for a semiconductor-based radiation detector technology that can achieve fine position resolution while maintaining the excellent energy resolution intrinsic to semiconductor detectors, can be fabricated through simple processes, does not require complex electrical interconnections to the detector, and can reduce the number of required channels of readout electronics. Proximity electrode signal readout (PESR), in which the electrodes are not in physical contact with the detector surface, satisfies this need

  18. Semiconductor detectors with proximity signal readout

    Energy Technology Data Exchange (ETDEWEB)

    Asztalos, Stephen J. [XIA, LLC, Hayward, CA (United States)

    2014-01-30

    Semiconductor-based radiation detectors are routinely used for the detection, imaging, and spectroscopy of x-rays, gamma rays, and charged particles for applications in the areas of nuclear and medical physics, astrophysics, environmental remediation, nuclear nonproliferation, and homeland security. Detectors used for imaging and particle tracking are more complex in that they typically must also measure the location of the radiation interaction in addition to the deposited energy. In such detectors, the position measurement is often achieved by dividing or segmenting the electrodes into many strips or pixels and then reading out the signals from all of the electrode segments. Fine electrode segmentation is problematic for many of the standard semiconductor detector technologies. Clearly there is a need for a semiconductor-based radiation detector technology that can achieve fine position resolution while maintaining the excellent energy resolution intrinsic to semiconductor detectors, can be fabricated through simple processes, does not require complex electrical interconnections to the detector, and can reduce the number of required channels of readout electronics. Proximity electrode signal readout (PESR), in which the electrodes are not in physical contact with the detector surface, satisfies this need.

  19. CdTe detector based PIXE mapping of geological samples

    International Nuclear Information System (INIS)

    A sample collected from a borehole drilled approximately 10 km ESE of Bragança, Trás-os-Montes, was analysed by standard and high energy PIXE at both CTN (previous ITN) PIXE setups. The sample is a fine-grained metapyroxenite grading to coarse-grained in the base with disseminated sulphides and fine veinlets of pyrrhotite and pyrite. Matrix composition was obtained at the standard PIXE setup using a 1.25 MeV H+ beam at three different spots. Medium and high Z elemental concentrations were then determined using the DT2fit and DT2simul codes (Reis et al., 2008, 2013 [1,2]), on the spectra obtained in the High Resolution and High Energy (HRHE)-PIXE setup (Chaves et al., 2013 [3]) by irradiation of the sample with a 3.8 MeV proton beam provided by the CTN 3 MV Tandetron accelerator. In this paper we present results, discuss detection limits of the method and the added value of the use of the CdTe detector in this context

  20. CdTe detector based PIXE mapping of geological samples

    Energy Technology Data Exchange (ETDEWEB)

    Chaves, P.C., E-mail: cchaves@ctn.ist.utl.pt [Centro de Física Atómica da Universidade de Lisboa, Av. Prof. Gama Pinto 2, 1649-003 Lisboa (Portugal); IST/ITN, Instituto Superior Técnico, Universidade Técnica de Lisboa, Campus Tecnológico e Nuclear, EN10, 2686-953 Sacavém (Portugal); Taborda, A. [Centro de Física Atómica da Universidade de Lisboa, Av. Prof. Gama Pinto 2, 1649-003 Lisboa (Portugal); IST/ITN, Instituto Superior Técnico, Universidade Técnica de Lisboa, Campus Tecnológico e Nuclear, EN10, 2686-953 Sacavém (Portugal); Oliveira, D.P.S. de [Laboratório Nacional de Energia e Geologia (LNEG), Apartado 7586, 2611-901 Alfragide (Portugal); Reis, M.A. [Centro de Física Atómica da Universidade de Lisboa, Av. Prof. Gama Pinto 2, 1649-003 Lisboa (Portugal); IST/ITN, Instituto Superior Técnico, Universidade Técnica de Lisboa, Campus Tecnológico e Nuclear, EN10, 2686-953 Sacavém (Portugal)

    2014-01-01

    A sample collected from a borehole drilled approximately 10 km ESE of Bragança, Trás-os-Montes, was analysed by standard and high energy PIXE at both CTN (previous ITN) PIXE setups. The sample is a fine-grained metapyroxenite grading to coarse-grained in the base with disseminated sulphides and fine veinlets of pyrrhotite and pyrite. Matrix composition was obtained at the standard PIXE setup using a 1.25 MeV H{sup +} beam at three different spots. Medium and high Z elemental concentrations were then determined using the DT2fit and DT2simul codes (Reis et al., 2008, 2013 [1,2]), on the spectra obtained in the High Resolution and High Energy (HRHE)-PIXE setup (Chaves et al., 2013 [3]) by irradiation of the sample with a 3.8 MeV proton beam provided by the CTN 3 MV Tandetron accelerator. In this paper we present results, discuss detection limits of the method and the added value of the use of the CdTe detector in this context.

  1. Estimation of mammary gland composition using CdTe series detector developed for photon-counting mammography

    Science.gov (United States)

    Ihori, Akiko; Okamoto, Chizuru; Yamakawa, Tsutomu; Yamamoto, Shuichiro; Okada, Masahiro; Nakajima, Ai; Kato, Misa; Kodera, Yoshie

    2016-03-01

    Energy resolved photon-counting mammography is a new technology, which counts the number of photons that passes through an object, and presents it as a pixel value in an image of the object. Silicon semiconductor detectors are currently used in commercial mammography. However, the disadvantage of silicon is the low absorption efficiency for high X-ray energies. A cadmium telluride (CdTe) series detector has a high absorption efficiency over a wide energy range. In this study, we proposed a method to estimate the composition of the mammary gland using a CdTe series detector as a photon-counting detector. The fact that the detection rate of breast cancer in mammography is affected by mammary gland composition is now widely accepted. Assessment of composition of the mammary gland has important implications. An important advantage of our proposed technique is its ability to discriminate photons using three energy bins. We designed the CdTe series detector system using the MATLAB simulation software. The phantom contains nine regions with the ratio of glandular tissue and adipose varying in increments of 10%. The attenuation coefficient for each bin's energy was calculated from the number of input and output photons possessed by each. The evaluation results obtained by plotting the attenuation coefficient μ in a three-dimensional (3D) scatter plot show that the plots had a regular composition order congruent with that of the mammary gland. Consequently, we believe that our proposed method can be used to estimate the composition of the mammary gland.

  2. Evaluation of Compton gamma camera prototype based on pixelated CdTe detectors

    OpenAIRE

    Calderón, Y.; Chmeissani, M.; Kolstein, M.; De Lorenzo, G.

    2014-01-01

    A proposed Compton camera prototype based on pixelated CdTe is simulated and evaluated in order to establish its feasibility and expected performance in real laboratory tests. The system is based on module units containing a 2×4 array of square CdTe detectors of 10×10 mm2 area and 2 mm thickness. The detectors are pixelated and stacked forming a 3D detector with voxel sizes of 2 × 1 × 2 mm3. The camera performance is simulated with Geant4-based Architecture for Medicine-Oriented Simulations(G...

  3. Performance of a new Schottky CdTe detector for hard x-ray spectroscopy

    Science.gov (United States)

    Takahashi, Tadayuki; Hirose, K.; Matsumoto, Chiho; Takizawa, Kyoko; Ohno, Ryouichi; Ozaki, Tsutomu; Mori, Kunishiro; Tomita, Yasuhiro

    1998-07-01

    We report a significant improvement of the spectral properties of a cadmium telluride (CdTe) detector. With the use of a high quality CdTe crystal, we formed a high Schottky barrier for the holes on a CdTe surface using a low work-function metal, indium. For a 2 X 2 mm(superscript 2) detector with a thickness of 0.5 mm the leakage current was measured to be 0.7 nA at room temperature (20 degree(s)C) and 10 pA at -20 degree(s)C for a 400 V bias voltage. The low-leakage current of the detector allows us to operate the detector at a higher bias voltage than previous CdTe detectors. The improved charge collection efficiency and the low-leakage current leads to an energy resolution of 1.1 - 2.5 keV FWHM in the energy range 2 keV to 150 keV at 20 degree(s)C without charge loss correction electronics. We confirmed that once a high electric field of several kV/cm is applied, the Schottky CdTe has a very good energy resolution as well as sufficient stability to be used for practical applications.

  4. CdTe detector use for PIXE characterization of TbCoFe thin films

    International Nuclear Information System (INIS)

    Peltier cooled CdTe detectors have good efficiency beyond the range of energies normally covered by Si(Li) detectors, the most common detectors in PIXE applications. An important advantage of CdTe detectors is the possibility of studying K X-rays lines instead the L X-rays lines in various cases since CdTe detectors present an energy efficiency plateau reaching 70 keV or more. The ITN CdTe useful energy range starts at K-Kα (3.312 keV) and goes up to 120 keV, just above the energy of the lowest γ-ray of the 19F(p, p'γ)19F reaction. In the new ITN HRHE-PIXE line, a CdTe detector is associated to a POLARIS microcalorimeter X-ray detector built by Vericold Technologies GmbH (an Oxford Instruments Group Company). The ITN POLARIS has a resolution of 15 eV at 1.486 keV (Al-Kα) and 24 eV at 10.550 keV (Pb-Lα1). In the present work, a TbCoFe thin film deposited on a Si substrate was analysed at the HRHE-PIXE system. The good efficiency of the CdTe detector at 45 keV (Tb-Kα), and the excellent resolution of POLARIS microcalorimeter at 6.403 keV (Fe-Kα), are presented and the new possibilities open to the IBA analysis of systems with traditionally overlapping X-rays and near mass elements are discussed.

  5. Imaging performance comparison between a LaBr3: Ce scintillator based and a CdTe semiconductor based photon counting compact gamma camera.

    Science.gov (United States)

    Russo, P; Mettivier, G; Pani, R; Pellegrini, R; Cinti, M N; Bennati, P

    2009-04-01

    The authors report on the performance of two small field of view, compact gamma cameras working in single photon counting in planar imaging tests at 122 and 140 keV. The first camera is based on a LaBr3: Ce scintillator continuous crystal (49 x 49 x 5 mm3) assembled with a flat panel multianode photomultiplier tube with parallel readout. The second one belongs to the class of semiconductor hybrid pixel detectors, specifically, a CdTe pixel detector (14 x 14 x 1 mm3) with 256 x 256 square pixels and a pitch of 55 microm, read out by a CMOS single photon counting integrated circuit of the Medipix2 series. The scintillation camera was operated with selectable energy window while the CdTe camera was operated with a single low-energy detection threshold of about 20 keV, i.e., without energy discrimination. The detectors were coupled to pinhole or parallel-hole high-resolution collimators. The evaluation of their overall performance in basic imaging tasks is presented through measurements of their detection efficiency, intrinsic spatial resolution, noise, image SNR, and contrast recovery. The scintillation and CdTe cameras showed, respectively, detection efficiencies at 122 keV of 83% and 45%, intrinsic spatial resolutions of 0.9 mm and 75 microm, and total background noises of 40.5 and 1.6 cps. Imaging tests with high-resolution parallel-hole and pinhole collimators are also reported. PMID:19472638

  6. Metal-semiconductor, composite radiation detectors

    International Nuclear Information System (INIS)

    In 1989, Naruse and Hatayama of Toshiba published a design for an increased efficiency x-ray detector. The design increased the efficiency of a semiconductor detector by interspersing layers of high-z metal within it. Semiconductors such as silicon make good, high-resolution radiation detectors, but they have low efficiency because they are low-z materials (z = 14). High-z metals, on the other hand, are good absorbers of high-energy photons. By interspersing high-z metal layers with semiconductor layers, Naruse and Hatayama combined the high absorption efficiency of the high-z metals with the good detection capabilities of a semiconductor. This project is an attempt to use the same design to produce a high-efficiency, room temperature gamma ray detector. By their nature, gamma rays require thicker metal layers to efficiently absorb them. These thicker layers change the behavior of the detector by reducing the resolution, compared to a solid state detector, and shifting the photopeak by a predictable amount. During the last year, the authors have procured and tested a commercial device with operating characteristics similar to those of a single layer of the composite device. They have modeled the radiation transport in a multi-layered device, to verify the initial calculations of layer thickness and composition. They have modeled the electrostatic field in different device designs to locate and remove high-field regions that can cause device breakdown. They have fabricated 14 single layer prototypes

  7. Alpha spectroscopy apparatus using a semiconductor detector

    International Nuclear Information System (INIS)

    Semiconductor detectors permit precise measurement of α particle energy. The experimental equipment described includes: a detection head surrounding a primary vacuum and arranged specially for a spectroscopy, a low-background preamplifier with a response proportional to the charge collected by the detector, a conventional amplifier and a multi-channel selector. The electronic background is reduced by selecting the most appropriate entrance and pulseshaping circuits. The source and detector are placed in such a way as to ensure minimum dispersion of the energy of the incident α particles. Resolutions of approximately 30 keV have been obtained for the α particles of U233 with a recent prototype detector (LTT). (author)

  8. Testing the plutonium isotopic analysis code FRAM with various CdTe detectors.

    Energy Technology Data Exchange (ETDEWEB)

    Vo, Duc T.; Russo, P. A. (Phyllis A.)

    2002-01-01

    The isotopic analysis code Fixed-energy Response-function Analysis with Multiple efficiency (FRAM)1,2 has been proven to successfully analyze plutonium spectra taken with a portable CdTe detector with Peltier cooling, the first results of this kind for a noncryogenic detector.3 These are the first wide-range plutonium gamma-ray isotopics analysis results obtained with other than Ge spectrometers. The CdTe spectrometer measured small plutonium reference samples in reasonable count times, covering the range from low to high burnup. This paper describes further testing of FRAM with two CdTe detectors of different sizes and resolutions using different analog and digital, portable multichannel analyzers (MCAs).

  9. New CdTe photoconductor array detector for x-ray applications

    International Nuclear Information System (INIS)

    A CdTe photoconductor array x-ray detector was grown using molecular beam epitaxy (MBE) on a Si(100) substrate. The temporal response of the photoconductor arrays is as fast as 21 ps rise time and 38 ps full width half-maximum (FWHM). The spatial resolution of the photoconductor was good enough to provide 75 μm FWHM using a 50 μm synchrotron x-ray beam. A substantial number of x-ray photons are absorbed effectively within the MBE CdTe layer as observed from the linear response up to 15 keV. These results demonstrate that MBE grown CdTe is a suitable choice of the detector materials to meet the requirements for x-ray detectors

  10. The use of portable semiconductor detectors in nuclear medicine

    International Nuclear Information System (INIS)

    A new biotelemetric system, CdTe semiconductor detectors with portable hard memory, for the registration of time activity curves in particular body regions of patients is introduced. The hard- and software connection of the system to the already present EDV configuration is described. The characteristics of the detectors are studied, theoretically explained and compared to the information given by the producers. By means of the determination of the ortho-iodine hippuric acid clearance (OIH) from the registration of the time activity curves in the chest the first information about the practicability in clinical use as well as the validity of the method are deduced. The detector system proved itself to be susceptible to problems, especially from manipulation of the cable or from movement of the patient. The determination of the OIH clearance from the partial body curve was problematic, because an extrapolation to the whole body based on the specific OIH kinetic in the small, observed tissue section is difficult. The comparison with the camera picture should be carefully evaluated, because this method has in principle the same inadequacies. (orig./HP)

  11. Radiation tests of semiconductor detectors

    OpenAIRE

    Chmill, Valery

    2006-01-01

    This thesis investigates the response of Gallium Arsenide (GaAs) detectors to ionizing irradiation. Detectors based on π-υ junction formed by deep level centers doping. The detectors have been irradiated with 137Cs γ-rays up to 110 kGy, with 6 MeV mean energy neutron up to approximately 6 · 1014 n/cm2, with protons and mixed beam up to 1015 p/cm2. Results are presented for the effects on leakage currents and charge collection efficiencies for minimum ionizing electrons and alpha particles. Th...

  12. New materials for radiation hard semiconductor detectors

    CERN Document Server

    Sellin, P J; CERN. Geneva

    2006-01-01

    We present a review of the current status of research into new semiconductor materials for use as particle tracking detectors in very high radiation environments. This work is carried out within the framework of the CERN RD50 collaboration, which is investigating detector technologies suitable for operation at the proposed Super-LHC facility (SLHC). Tracking detectors operating at the SLHC in this environment will have to be capable of withstanding radiation levels arising from a luminosity of 1035 cm-2s-1 which will present severe challenges to current tracking detector technologies. The "new materials" activity within RD50 is investigating the performance of various semiconductor materials that potentially offer radiation hard alternatives to silicon devices. The main contenders in this study are silicon carbide, gallium nitride and amorphous silicon. In this paper we review the current status of these materials, in terms of material quality, commercial availability, charge transport properties, and radiati...

  13. 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.

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

    Science.gov (United States)

    Khusainov, A. Kh; Dudin, A. L.; Ilves, A. G.; Morozov, V. F.; Pustovoit, A. K.; Arlt, R. D.

    1999-06-01

    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°C cooling (by a Peltier cooler of 15×15×10 mm size and a consumed power less than 5 W). Presently detectors with volume of up to 300 mm 3 are available. In terms of photoelectric effect efficiency it corresponds to HPGe detectors with volumes of about 1.5 cm 3. The possibilities of further improvement of CdTe and CdZnTe detector characteristics are discussed in this paper.

  15. Si and CdTe pixel detector developments at SPring-8

    International Nuclear Information System (INIS)

    Single X-ray photon counting pixel detectors have become the most advanced detector technology in synchrotron radiation experiments recently. In particular, the PILATUS detector based on a silicon sensor has reached a very mature state and represents the world's largest detector in this field. This paper first reports on threshold energy calibrations and the capability of applying an energy-resolved X-ray imaging with PILATUS. Second the design of a cadmium telluride (CdTe) pixel detector is described. A high density and high-atomic number sensor material is required in high energy X-ray applications available at SPring-8. For this purpose we are developing a CdTe pixel detector with the SP8-01 readout ASIC covering a wide dynamic range between 10 and 100 keV and containing lower and upper discriminators.

  16. Simulation of active-edge pixelated CdTe radiation detectors

    OpenAIRE

    Duarte, DD; Lipp, JD; Schneider, A.; Seller, P; Veale, MC; Wilson, MD; Baker, MA; Sellin, PJ

    2016-01-01

    The edge surfaces of single crystal CdTe play an important role in the electronic properties and performance of this material as an X-ray and γ-ray radiation detector. Edge effects have previously been reported to reduce the spectroscopic performance of the edge pixels in pixelated CdTe radiation detectors without guard bands. A novel Technology Computer Aided Design (TCAD) model based on experimental data has been developed to investigate these effects. The results presented in this paper sh...

  17. Basic processes and scintillator and semiconductor detectors

    International Nuclear Information System (INIS)

    In the following course, the interaction of heavy charged particles, electrons and Γ with matter is represented. Two types of detectors are studied, organic and inorganic scintillators and semiconductors. The signal formation is analysed. (author). 13 refs., 48 figs., 5 tabs

  18. Simulation of active-edge pixelated CdTe radiation detectors

    Science.gov (United States)

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

    2016-01-01

    The edge surfaces of single crystal CdTe play an important role in the electronic properties and performance of this material as an X-ray and γ-ray radiation detector. Edge effects have previously been reported to reduce the spectroscopic performance of the edge pixels in pixelated CdTe radiation detectors without guard bands. A novel Technology Computer Aided Design (TCAD) model based on experimental data has been developed to investigate these effects. The results presented in this paper show how localized low resistivity surfaces modify the internal electric field of CdTe creating potential wells. These result in a reduction of charge collection efficiency of the edge pixels, which compares well with experimental data.

  19. Fine-pitch CdTe detector for hard X-ray imaging and spectroscopy of the Sun with the FOXSI rocket experiment

    OpenAIRE

    Ishikawa, S.; Katsuragawa, M.; Watanabe, S; Uchida, Y.; Takeda, S; Takahashi, T.; Saito, S.; Glesener, L.; Buitrago-Casas, J. C.; Krucker, S.; Christe, S.

    2016-01-01

    We have developed a fine-pitch hard X-ray (HXR) detector using a cadmium telluride (CdTe) semiconductor for imaging and spectroscopy for the second launch of the Focusing Optics Solar X-ray Imager (FOXSI). FOXSI is a rocket experiment to perform high sensitivity HXR observations from 4-15 keV using the new technique of HXR focusing optics. The focal plane detector requires < 100 um position resolution (to take advantage of the angular resolution of the optics) and about 1 keV energy resolutio...

  20. A facile and green preparation of high-quality CdTe semiconductor nanocrystals at room temperature

    Science.gov (United States)

    Liu, Yan; Shen, Qihui; Yu, Dongdong; Shi, Weiguang; Li, Jixue; Zhou, Jianguang; Liu, Xiaoyang

    2008-06-01

    One chemical reagent, hydrazine hydrate, was discovered to accelerate the growth of semiconductor nanocrystals (cadmium telluride) instead of additional energy, which was applied to the synthesis of high-quality CdTe nanocrystals at room temperature and ambient conditions within several hours. Under this mild condition the mercapto stabilizers were not destroyed, and they guaranteed CdTe nanocrystal particle sizes with narrow and uniform distribution over the largest possible range. The CdTe nanocrystals (photoluminescence emission range of 530-660 nm) synthesized in this way had very good spectral properties; for instance, they showed high photoluminescence quantum yield of up to 60%. Furthermore, we have succeeded in detecting the living Borrelia burgdorferi of Lyme disease by its photoluminescence image using CdTe nanocrystals.

  1. A facile and green preparation of high-quality CdTe semiconductor nanocrystals at room temperature

    International Nuclear Information System (INIS)

    One chemical reagent, hydrazine hydrate, was discovered to accelerate the growth of semiconductor nanocrystals (cadmium telluride) instead of additional energy, which was applied to the synthesis of high-quality CdTe nanocrystals at room temperature and ambient conditions within several hours. Under this mild condition the mercapto stabilizers were not destroyed, and they guaranteed CdTe nanocrystal particle sizes with narrow and uniform distribution over the largest possible range. The CdTe nanocrystals (photoluminescence emission range of 530-660 nm) synthesized in this way had very good spectral properties; for instance, they showed high photoluminescence quantum yield of up to 60%. Furthermore, we have succeeded in detecting the living Borrelia burgdorferi of Lyme disease by its photoluminescence image using CdTe nanocrystals

  2. A facile and green preparation of high-quality CdTe semiconductor nanocrystals at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Liu Yan [Jilin Province Research Center for Engineering and Technology of Spectral Analytical Instruments, Jilin University, Changchun 130023 (China); Shen Qihui; Shi Weiguang; Li Jixue; Liu Xiaoyang [State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012 (China); Yu Dongdong [1st Hopstail affiliated to Jilin University, Jilin University, Changchun 130023 (China); Zhou Jianguang [Research Center for Analytical Instrumentation, Zhejiang University, Hangzhou 310058 (China)], E-mail: liuxy@jlu.edu.cn, E-mail: jgzhou70@126.com

    2008-06-18

    One chemical reagent, hydrazine hydrate, was discovered to accelerate the growth of semiconductor nanocrystals (cadmium telluride) instead of additional energy, which was applied to the synthesis of high-quality CdTe nanocrystals at room temperature and ambient conditions within several hours. Under this mild condition the mercapto stabilizers were not destroyed, and they guaranteed CdTe nanocrystal particle sizes with narrow and uniform distribution over the largest possible range. The CdTe nanocrystals (photoluminescence emission range of 530-660 nm) synthesized in this way had very good spectral properties; for instance, they showed high photoluminescence quantum yield of up to 60%. Furthermore, we have succeeded in detecting the living Borrelia burgdorferi of Lyme disease by its photoluminescence image using CdTe nanocrystals.

  3. Improved spectrometric performance of CdTe radiation detectors in a p-i -n design

    OpenAIRE

    Niraula, Madan; Mochizuki, Daisuke; Aoki, Toru; Hatanaka, Yoshinori; Tomita, Yasuhiro; Nihashi, Tokuaki; ニラウラ, マダン

    1999-01-01

    CdTe radiation detectors were fabricated using a p-i-n design and a significant improvement in the spectral properties was obtained during room temperature operation. An iodine doped n-CdTe layer was grown on the Te faces of the (111) oriented high resistivity CdTe crystals at the low substrate temperature of 150°C. An aluminum electrode was evaporated on the n-CdTe side for the n-type contact, while a gold electrode on the opposite side acted as the p-type contact. Very low leakage currents,...

  4. 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.

  5. Behaviour of semiconductor nuclear-particle detectors

    International Nuclear Information System (INIS)

    Experimental and theoretical studies of the behaviour of semiconductor nuclear-particle detectors have been carried out over the temperature range of 0.2oK to 300oK. A simple theoretical model for the detector behaviour, which is found to describe the observed behaviour over a wide range of parameters, is presented. The importance of semiconductor purity and bias voltage in connection with pulse height, pulse rise-time and detector area is discussed. Empirical studies of noise and energy resolution indicate that for alpha particles the smallest observed peak-widths are substantially larger than those expected on the basis of electrical noise from the detector and amplifier. Equivalent noise values of ≤ 3 keV full-width at half maximum (FWHM) have been found for a 40-mm2 silicon surface-barrier detector at 77oK. Semiconductor detectors exhibit a ''pulse-height defect'' for fission fragments. There is evidence that this defect is not caused by a ''dead layer''. If electric fields which are insufficient to insure complete ''collection'' are responsible for the defect, the necessary minimum field (at the surface) is > 3 x 104 V/cm for fission fragments, as compared to the value of 2 x 103 V/cm which is found necessary in the case of alpha particles in Ge and Si. Detailed considerations regarding pulse rise-time at the amplifier have shown that in high-resistivity material both the ''dielectric'' relaxation time and the resistance associated with the undepleted base material can play an important role. A quantative description of the effect of detector and amplifier parameters on the shapes and rise-times associated with the pulse are presented. The advantages and problems associated with the use of surface-barrier detectors in several unique low-temperature nuclear-alignment experiments are discussed. These experiments involved fission-fragment angular distributions and resolution of alpha-fine structure with long-term stability. Matched expansion

  6. The influence of electron track lengths on the γ-ray response of compound semiconductor detectors

    International Nuclear Information System (INIS)

    The charge-trapping effect in compound semiconductor γ-ray detectors in the presence of a uniform electric field is commonly described by Hecht's relation. However, Hecht's relation ignores the geometrical spread of charge carriers caused by the finite range of primary and secondary electrons (δ-rays) in the detector. In this paper, a method based on the Shockley–Ramo theorem is developed to calculate γ-ray induced charge pulses by taking into account the charge-trapping effect associated with the geometrical spread of charge carriers. The method is then used to calculate the response of a planar CdTe detector to energetic γ-rays by which the influence of electron track lengths on the γ-ray response of the detectors is clearly shown

  7. The influence of electron track lengths on the γ-ray response of compound semiconductor detectors

    Energy Technology Data Exchange (ETDEWEB)

    Nakhostin, M., E-mail: M.Nakhostin@surrey.ac.uk [Department of Physics, University of Surrey, Guildford GU2 7XH (United Kingdom); Esmaili-Torshabi, A. [Department of Electrical and Computer Engineering, Kerman University of Technology, Kerman (Iran, Islamic Republic of)

    2015-10-11

    The charge-trapping effect in compound semiconductor γ-ray detectors in the presence of a uniform electric field is commonly described by Hecht's relation. However, Hecht's relation ignores the geometrical spread of charge carriers caused by the finite range of primary and secondary electrons (δ-rays) in the detector. In this paper, a method based on the Shockley–Ramo theorem is developed to calculate γ-ray induced charge pulses by taking into account the charge-trapping effect associated with the geometrical spread of charge carriers. The method is then used to calculate the response of a planar CdTe detector to energetic γ-rays by which the influence of electron track lengths on the γ-ray response of the detectors is clearly shown.

  8. Characterization of CdTe0.9Se0.1:Cl strip detectors

    International Nuclear Information System (INIS)

    CdTe0.9Se0.1:Cl is a detector grade material for gamma and X-rays. Its high resistivity and the high mobility lifetime product yield a high charge collection efficiency of 90 percent. CdTe0.9Se0.1:Cl was used for the first time to built up a strip detector. The detector performance was investigated by a 57Co source. The signal behaviour, charge collection efficiency and coupling effects were analyzed for different strips. The comparison between the signal amplitude of all strips showed a good homogeneous response for the device. For a single strip a charge collection efficiency of more than 40 percent was obtained. (orig.)

  9. Evaluation of Polarization Effects of e(-) Collection Schottky CdTe Medipix3RX Hybrid Pixel Detector

    OpenAIRE

    Astromskas, V.; Gimenez, EN; Lohstroh, A; Tartoni, N

    2016-01-01

    This paper focuses on the evaluation of operational conditions such as temperature, exposure time and flux on the polarization of a Schottky electron collection CdTe detector. A Schottky e- collection CdTe Medipix3RX hybrid pixel detector was developed as a part of the CALIPSO-HIZPAD2 EU project. The 128 ×128 pixel matrix and 0.75 mm thick CdTe sensor bump-bonded to Medipix3RX readout chips enabled the study of the polarization effects. Single and quad module Medipix3RX chips were used which ...

  10. Imaging performance comparison between a LaBr3:Ce scintillator based and a CdTe semiconductor based photon counting compact gamma camera

    International Nuclear Information System (INIS)

    The authors report on the performance of two small field of view, compact gamma cameras working in single photon counting in planar imaging tests at 122 and 140 keV. The first camera is based on a LaBr3:Ce scintillator continuous crystal (49x49x5 mm3) assembled with a flat panel multianode photomultiplier tube with parallel readout. The second one belongs to the class of semiconductor hybrid pixel detectors, specifically, a CdTe pixel detector (14x14x1 mm3) with 256x256 square pixels and a pitch of 55 μm, read out by a CMOS single photon counting integrated circuit of the Medipix2 series. The scintillation camera was operated with selectable energy window while the CdTe camera was operated with a single low-energy detection threshold of about 20 keV, i.e., without energy discrimination. The detectors were coupled to pinhole or parallel-hole high-resolution collimators. The evaluation of their overall performance in basic imaging tasks is presented through measurements of their detection efficiency, intrinsic spatial resolution, noise, image SNR, and contrast recovery. The scintillation and CdTe cameras showed, respectively, detection efficiencies at 122 keV of 83% and 45%, intrinsic spatial resolutions of 0.9 mm and 75 μm, and total background noises of 40.5 and 1.6 cps. Imaging tests with high-resolution parallel-hole and pinhole collimators are also reported.

  11. Fine-pitch CdTe detector for hard X-ray imaging and spectroscopy of the Sun with the FOXSI rocket experiment

    CERN Document Server

    Ishikawa, S; Watanabe, S; Uchida, Y; Takeda, S; Takahashi, T; Saito, S; Glesener, L; Buitrago-Casas, J C; Krucker, S; Christe, S

    2016-01-01

    We have developed a fine-pitch hard X-ray (HXR) detector using a cadmium telluride (CdTe) semiconductor for imaging and spectroscopy for the second launch of the Focusing Optics Solar X-ray Imager (FOXSI). FOXSI is a rocket experiment to perform high sensitivity HXR observations from 4-15 keV using the new technique of HXR focusing optics. The focal plane detector requires -30 C). Double-sided silicon strip detectors were used for the first FOXSI flight in 2012 to meet these criteria. To improve the detectors' efficiency (66 at 15 keV for the silicon detectors) and position resolution of 75 um for the second launch, we fabricated double-sided CdTe strip detectors with a position resolution of 60 um and almost 100 % efficiency for the FOXSI energy range. The sensitive area is 7.67 mm x 7.67 mm, corresponding to the field of view of 791'' x 791''. An energy resolution of about 1 keV (FWHM) and low energy threshold of 4 keV were achieved in laboratory calibrations. The second launch of FOXSI was performed on De...

  12. Fabrication and performance of p-i-n CdTe radiation detectors

    International Nuclear Information System (INIS)

    We report on the fabrication and performance of CdTe radiation detectors in a new p-i-n structure which helps to reduce the leakage current to a minimum level. Chlorine-doped single-crystal CdTe substrates having resistivity in the order of 109 Ω cm were used in this study. Iodine-doped n-type CdTe layers were grown homoepitaxially on one face of each crystals using the hydrogen plasma-radical-assisted metalorganic chemical vapor deposition technique at low substrate temperature of 150 deg. C. Indium electrode was evaporated on the n-CdTe side while a gold electrode on the opposite side acted as a p-type contact. Detectors thus fabricated exhibited low leakage current (below 0.4 nA/mm2 at 250 V applied reverse bias for the best one) and good performance at room temperature. Spectral response of the detectors showed improved energy resolution for Am-241, Co-57, and Cs-137 radioisotopes. Detectors were further tested with X-ray photons of different intensities for their potential application in imaging systems and promising responses were obtained

  13. Fast polycrystalline CdTe detectors for bunch-by-bunch luminosity monitoring in the LHC

    CERN Document Server

    Brambilla, A; Jolliot, M; Bravin, E

    2008-01-01

    The luminosity at the four interaction points of the Large Hadron Collider (LHC) must be continuously monitored in order to provide an adequate tool for the control and optimisation of beam parameters. Polycrystalline cadmium telluride (CdTe) detectors have previously been tested, showing their high potential to fulfil the requirements of luminosity measurement in the severe environment of the LHC interaction regions. Further, the large signal yield and the fast response time should allow bunch-by-bunch measurement of the luminosity at 40 MHz with high accuracy. Four luminosity monitors with two rows of five polycrystalline CdTe detectors each have been fabricated and will be installed at both sides of the low-luminosity interaction points ALICE and LHC-b. A detector housing was specially designed to meet the mechanical constraints in the LHC. A series of elementary CdTe detectors were fabricated and tested, of which 40 were selected for the luminosity monitors. A sensitivity of 104 electrons per minimum ioni...

  14. CdTe X-ray detectors for medical computerized tomography

    International Nuclear Information System (INIS)

    The kinetic and lux-ampere characteristics (BAC) of pure CdTe crystals of p- and n-types used as X-ray detectors for medical tomography are studied. It is shown that proper reproducibility of the excitation pulse form, strict LAC linearity and low photocurrent memary of the detectors with a regquired maintained sensitivity maintained may be attained using semi-insulating cadmium telluride crystals with a low concentration of adhesion centers equal to the concentration of recombination levels. In that case, the detector should operate under the double injection regime

  15. Charge collection in semiconductor radiation detectors

    International Nuclear Information System (INIS)

    Semiconductor particle-detectors operate like ion chambers by collecting the charge liberated by an incident-ionizing particle. However the mechanism of charge collection is much more complicated than that of the ion chamber, depending in detail on the properties of the semiconductor, the potential distribution in the device and the ionization density along the initial track. Loss of charge can be attributed to two effects - recombination along the initial track and subsequent trapping of the moving carriers. These effects can be separated by using particles of widely differing ionization densities. Such investigations have been carried out for various silicon devices fabricated in different ways and covering a wide range of resistivities. Analytical results have been derived applicable to the general case of charge loss through trapping, and some results have also been obtained concerning recombination loss. (author)

  16. Improvement of the sensitivity of CdTe detectors in the high energy regions

    International Nuclear Information System (INIS)

    In order to improve the efficiency of the full energy peak in the high energy regions, we had previously suggested a multi-layered structure of CdTe elements and have since confirmed the sensitivity improvement of the full energy peak. And furthermore, we have suggested a new type structure of multi-layered elements in this paper and we confirmed that the efficiency of the full energy peak became higher and that more proper energy spectra were obtained by our current experiment than by the detector with the conventional structure. This paper describes a simulation and experiment to improve the efficiency of the full energy peak and to obtain the more proper energy spectra of 137Cs (662keV) and 60Co (1.17 and 1.33MeV) using the new structure of CdTe detector. (J.P.N.)

  17. Improvement of the sensitivity of CdTe detectors in the high energy regions

    Energy Technology Data Exchange (ETDEWEB)

    Nishizawa, Hiroshi; Ikegami, Kazunori; Takashima, Kazuo; Usami, Teruo [Mitsubishi Electric Corp., Tokyo (Japan); Yamamoto, Takayoshi

    1996-07-01

    In order to improve the efficiency of the full energy peak in the high energy regions, we had previously suggested a multi-layered structure of CdTe elements and have since confirmed the sensitivity improvement of the full energy peak. And furthermore, we have suggested a new type structure of multi-layered elements in this paper and we confirmed that the efficiency of the full energy peak became higher and that more proper energy spectra were obtained by our current experiment than by the detector with the conventional structure. This paper describes a simulation and experiment to improve the efficiency of the full energy peak and to obtain the more proper energy spectra of {sup 137}Cs (662keV) and {sup 60}Co (1.17 and 1.33MeV) using the new structure of CdTe detector. (J.P.N.)

  18. P-I-N CdTe gamma-ray detectors by liquid phase epitaxy (LPE)

    International Nuclear Information System (INIS)

    A new device concept of CdTe gamma ray detectors has been demonstrated by using p+(HgCdTe)-n(CdTe)-n+(HgCdTe) diode structures. Both p+ and n+-type Hg/sub 0.25/Cd/sub 0.75/Te epilayers were grown by the liquid phase epitaxy (LPE) technique on semi-insulating CdTe sensor elements. The LPE-grown P-I-N structure offers potential advantages for p-n junction formation and ohmic contact over standard ion-implanted diodes or Schottky barrier devices. Detectors with active areas of 2 mm2 were fabricated. Resolutions of 10 keV were obtained for the 122 keV gamma peak of Co57 at room temperature

  19. 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.)

  20. Fabrication of prototypes of Ge(li) semiconductor detector

    International Nuclear Information System (INIS)

    The fabrication process of Ge(Li) semiconductor detector prototypes, from specific chemical treatments of doped monocrystal with receptor impurities (p+ semicondutor) is presented. The detector characteristics, such as resulotion and operation tension are shown. (M.C.K.)

  1. Growth and characterization of CdTe single crystals for radiation detectors

    CERN Document Server

    Funaki, M; Satoh, K; Ohno, R

    1999-01-01

    To improve the productivity of CdTe radiation detectors, the crystal growth by traveling heater method (THM) as well as the quality of the fabricated detectors were investigated. In the THM growth, optimization of the solvent volume was found to be essential because it affects the shape of the growth interface. The use of the slightly tilted seed from B was also effective to limit the generation of twins having different directions. Single-crystal (1 1 1) wafers, larger than 30x30 mm sup 2 were successfully obtained from a grown crystal of 50 mm diameter. Pt/CdTe/Pt detectors of dimensions 4x4x2 mm sup 3 , fabricated from the whole crystal ingot, showed an energy resolution (FWHM of 122 keV peak from a sup 5 sup 7 Co source) between 6% and 8%. Similarly, Pt/CdTe/In detectors of dimensions 2x2x0.5 mm sup 3 showed a resolution better than 3%. These characteristics encourage the practical applications of various types of CdTe detectors.

  2. The Si/CdTe semiconductor Compton camera of the ASTRO-H Soft Gamma-ray Detector (SGD)

    OpenAIRE

    Watanabe, Shin; Tajima, Hiroyasu; Fukazawa, Yasushi; Ichinohe, Yuto; Takeda, Shin'ichiro; Enoto, Teruaki; Fukuyama, Taro; Furui, Shunya; Genba, Kei; Hagino, Kouichi; Harayama, Astushi; Kuroda, Yoshikatsu; Matsuura, Daisuke; Nakamura, Ryo; Nakazawa, Kazuhiro

    2015-01-01

    The Soft Gamma-ray Detector (SGD) is one of the instrument payloads onboard ASTRO-H, and will cover a wide energy band (60--600 keV) at a background level 10 times better than instruments currently in orbit. The SGD achieves low background by combining a Compton camera scheme with a narrow field-of-view active shield. The Compton camera in the SGD is realized as a hybrid semiconductor detector system which consists of silicon and cadmium telluride (CdTe) sensors. The design of the SGD Compton...

  3. CdTe in photoconductive applications. Fast detector for metrology and X-ray imaging

    International Nuclear Information System (INIS)

    Operating as a photoconductor, the sensitivity and the impulse response of semi-insulating materials greatly depend on the excitation duration compared to electron and hole lifetimes. The requirement of ohmic contact is shortly discussed. Before developing picosecond measurements with integrated autocorrelation system, this paper explains high energy industrial tomographic application with large CdTe detectors (25x15x0.9 mm3). The excitation is typically μs range. X-ray flash radiography, with 10 ns burst, is in an intermediate time domain where excitation is similar to electron life-time. In laser fusion experiment excitation is in the range of 50 ps and we develop photoconductive devices able to study very high speed X-ray emission time behaviour. Thin polycristalline MOCVD CdTe films with picosecond response are suitable to perform optical correlation measurements of single shot pulses with a very large bandwidth (- 50 GHz)

  4. Mechanism of the high X-ray sensitivity of single-crystal CdTe detectors

    International Nuclear Information System (INIS)

    One investigated into the effect of germanium amorphous impurities on X-ray sensitivity and on other features of single-crystals. One investigated into CdTe heat-stable crystals. One proposes a model of a local rearrangement of crystalline lattice near GeCd impurity atom. High X-ray sensitivity of CdTe doped by Ge impurity (doping levels = 3.0x1015 cm-3) is explained by difference of mobility of electrons and holes under ambipolar X-ray conductivity. The optimal impurity-defect composition of p-CdTe crystals serving as high-sensitive active elements of X-ray detectors is characterized by presence of GeCd, VCd defects and of VTe-Tei Frenkel pairs

  5. The Si/CdTe semiconductor Compton camera of the ASTRO-H Soft Gamma-ray Detector (SGD)

    CERN Document Server

    Watanabe, Shin; Fukazawa, Yasushi; Ichinohe, Yuto; Takeda, Shin'ichiro; Enoto, Teruaki; Fukuyama, Taro; Furui, Shunya; Genba, Kei; Hagino, Kouichi; Harayama, Astushi; Kuroda, Yoshikatsu; Matsuura, Daisuke; Nakamura, Ryo; Nakazawa, Kazuhiro; Noda, Hirofumi; Odaka, Hirokazu; Ohta, Masayuki; Onishi, Mitsunobu; Saito, Shinya; Sato, Goro; Sato, Tamotsu; Takahashi, Tadayuki; Tanaka, Takaaki; Togo, Atsushi; Tomizuka, Shinji

    2015-01-01

    The Soft Gamma-ray Detector (SGD) is one of the instrument payloads onboard ASTRO-H, and will cover a wide energy band (60--600 keV) at a background level 10 times better than instruments currently in orbit. The SGD achieves low background by combining a Compton camera scheme with a narrow field-of-view active shield. The Compton camera in the SGD is realized as a hybrid semiconductor detector system which consists of silicon and cadmium telluride (CdTe) sensors. The design of the SGD Compton camera has been finalized and the final prototype, which has the same configuration as the flight model, has been fabricated for performance evaluation. The Compton camera has overall dimensions of 12 cm x 12 cm x 12 cm, consisting of 32 layers of Si pixel sensors and 8 layers of CdTe pixel sensors surrounded by 2 layers of CdTe pixel sensors. The detection efficiency of the Compton camera reaches about 15% and 3% for 100 keV and 511 keV gamma rays, respectively. The pixel pitch of the Si and CdTe sensors is 3.2 mm, and ...

  6. A CdTe detector for Muon Transverse Profile Measurements

    CERN Document Server

    Placidi, Massimo; Schmickler, Hermann; CERN. Geneva. SPS Division; CERN. Geneva. LHC Division

    2001-01-01

    Beam diagnostics in future High Energy Accelerators will require long lived instrumentation in high radiation environment. Detectors capable of withstanding extreme radiation levels without requiring human intervention and being operated at frontiers of radiation-resistant technology are at a prime for applications in environmental-hostile situations. A research program has been launched at CERN in the framework of instrumentation developments for the LHC project aiming at individuating new solutions and technologies reliable under extreme operational conditions. Preliminary ideas are presented for applications in Muon Beams Diagnostics for future Neutrino Factories of materials presently considered and tested for application in the LHC luminosity detectors.

  7. Energy dispersive CdTe and CdZnTe detectors for spectral clinical CT and NDT applications

    Science.gov (United States)

    Barber, W. C.; Wessel, J. C.; Nygard, E.; Iwanczyk, J. S.

    2015-06-01

    We are developing room temperature compound semiconductor detectors for applications in energy-resolved high-flux single x-ray photon-counting spectral computed tomography (CT), including functional imaging with nanoparticle contrast agents for medical applications and non-destructive testing (NDT) for security applications. Energy-resolved photon-counting can provide reduced patient dose through optimal energy weighting for a particular imaging task in CT, functional contrast enhancement through spectroscopic imaging of metal nanoparticles in CT, and compositional analysis through multiple basis function material decomposition in CT and NDT. These applications produce high input count rates from an x-ray generator delivered to the detector. Therefore, in order to achieve energy-resolved single photon counting in these applications, a high output count rate (OCR) for an energy-dispersive detector must be achieved at the required spatial resolution and across the required dynamic range for the application. The required performance in terms of the OCR, spatial resolution, and dynamic range must be obtained with sufficient field of view (FOV) for the application thus requiring the tiling of pixel arrays and scanning techniques. Room temperature cadmium telluride (CdTe) and cadmium zinc telluride (CdZnTe) compound semiconductors, operating as direct conversion x-ray sensors, can provide the required speed when connected to application specific integrated circuits (ASICs) operating at fast peaking times with multiple fixed thresholds per pixel provided the sensors are designed for rapid signal formation across the x-ray energy ranges of the application at the required energy and spatial resolutions, and at a sufficiently high detective quantum efficiency (DQE). We have developed high-flux energy-resolved photon-counting x-ray imaging array sensors using pixellated CdTe and CdZnTe semiconductors optimized for clinical CT and security NDT. We have also fabricated high

  8. Energy dispersive CdTe and CdZnTe detectors for spectral clinical CT and NDT applications

    International Nuclear Information System (INIS)

    We are developing room temperature compound semiconductor detectors for applications in energy-resolved high-flux single x-ray photon-counting spectral computed tomography (CT), including functional imaging with nanoparticle contrast agents for medical applications and non-destructive testing (NDT) for security applications. Energy-resolved photon-counting can provide reduced patient dose through optimal energy weighting for a particular imaging task in CT, functional contrast enhancement through spectroscopic imaging of metal nanoparticles in CT, and compositional analysis through multiple basis function material decomposition in CT and NDT. These applications produce high input count rates from an x-ray generator delivered to the detector. Therefore, in order to achieve energy-resolved single photon counting in these applications, a high output count rate (OCR) for an energy-dispersive detector must be achieved at the required spatial resolution and across the required dynamic range for the application. The required performance in terms of the OCR, spatial resolution, and dynamic range must be obtained with sufficient field of view (FOV) for the application thus requiring the tiling of pixel arrays and scanning techniques. Room temperature cadmium telluride (CdTe) and cadmium zinc telluride (CdZnTe) compound semiconductors, operating as direct conversion x-ray sensors, can provide the required speed when connected to application specific integrated circuits (ASICs) operating at fast peaking times with multiple fixed thresholds per pixel provided the sensors are designed for rapid signal formation across the x-ray energy ranges of the application at the required energy and spatial resolutions, and at a sufficiently high detective quantum efficiency (DQE). We have developed high-flux energy-resolved photon-counting x-ray imaging array sensors using pixellated CdTe and CdZnTe semiconductors optimized for clinical CT and security NDT. We have also fabricated high

  9. Photon counting X-ray imaging with CdTe pixel detectors based on XPAD2 circuit

    Science.gov (United States)

    Franchi, Romain; Glasser, Francis; Gasse, Adrien; Clemens, Jean-Claude

    2006-07-01

    A semiconductor hybrid pixel detector for photon counting X-ray imaging has been developed and tested under radiation. The sensor is based on recent uniform CdTe single crystal associated with XPAD 2 counting chip via innovative processes of interconnection. The building detector is 1 mm thick, with an area of 1 cm 2 and consists of 600 square pixels cells 330 μm side. The readout chip working in electron collection mode is capable of setting homogeneous threshold with only a dispersion of 730 e -. Maximum noise level has been evaluated around 15 keV. First experiments under X-rays demonstrate a very good efficiency of detection. Moreover, imaging system allows excellent linearity over a large-scale achieving count rate of 3×10 6 photons/s/mm 2. Spectrometric measurements point up the system potential in multi-energies applications by locating and resolving X-rays lines of 241Am and 57Co sources.

  10. Semiconductor scintillator detector for gamma radiation

    International Nuclear Information System (INIS)

    Nowadays the devices employed to evaluate individual radiation exposition are based on dosimetric films and thermoluminescent crystals, whose measurements must be processed in specific transductors. Hence, these devices carry out indirect measurements. Although a new generation of detectors based on semiconductors which are employed in EPD's (Electronic Personal Dosemeters) being yet available, it high producing costs and large dimensions prevents the application in personal dosimetry. Recent research works reports the development of new detection devices based on photovoltaic PIN diodes, which were successfully employed for detecting and monitoring exposition to X rays. In this work, we step forward by coupling a 2mm anthracene scintillator NE1, which converts the high energy radiation in visible light, generating a Strong signal which allows dispensing the use of photomultipliers. A low gain high performance amplifier and a digital acquisition device are employed to measure instantaneous and cumulative doses for energies ranging from X rays to Gamma radiation up to 2 MeV. One of the most important features of the PIN diode relies in the fact that it can be employed as a detector for ionization radiation, since it requires a small energy amount for releasing electrons. Since the photodiode does not amplify the corresponding photon current, it must be coupled to a low gain amplifier. Therefore, the new sensor works as a scintillator coupled with a photodiode PIN. Preliminary experiments are being performed with this sensor, showing good results for a wide range of energy spectrum. (author)

  11. Semiconductor neutron detectors using depleted uranium oxide

    Science.gov (United States)

    Kruschwitz, Craig A.; Mukhopadhyay, Sanjoy; Schwellenbach, David; Meek, Thomas; Shaver, Brandon; Cunningham, Taylor; Auxier, Jerrad Philip

    2014-09-01

    This paper reports on recent attempts to develop and test a new type of solid-state neutron detector fabricated from uranium compounds. It has been known for many years that uranium oxide (UO2), triuranium octoxide (U3O8) and other uranium compounds exhibit semiconducting characteristics with a broad range of electrical properties. We seek to exploit these characteristics to make a direct-conversion semiconductor neutron detector. In such a device a neutron interacts with a uranium nucleus, inducing fission. The fission products deposit energy-producing, detectable electron-hole pairs. The high energy released in the fission reaction indicates that noise discrimination in such a device has the potential to be excellent. Schottky devices were fabricated using a chemical deposition coating technique to deposit UO2 layers a few microns thick on a sapphire substrate. Schottky devices have also been made using a single crystal from UO2 samples approximately 500 microns thick. Neutron sensitivity simulations have been performed using GEANT4. Neutron sensitivity for the Schottky devices was tested experimentally using a 252Cf source.

  12. The study of response of wide band gap semiconductor detectors using the Geant4

    Directory of Open Access Journals (Sweden)

    Hussain Riaz

    2014-01-01

    Full Text Available The energy dependence on the intrinsic efficiency, absolute efficiency, full energy peak absolute efficiency and peak-to-total ratio have been studied for various wide band gap semiconductor detectors using the Geant4 based Monte Carlo simulations. The detector thickness of 1-4 mm and the area in 16-100 mm2 range were considered in this work. In excellent agreement with earlier work (Rybka et al., [20], the Geant4 simulated values of detector efficiencies have been found to decrease with incident g-ray energy. Both for the detector thickness and the detector area, the increasing trends have been observed for total efficiency as well as for full-energy peak efficiency in 0.1 MeV-50 MeV range. For Cd1-xZnxTe, the detector response remained insensitive to changes in relative proportions of Zn. For various wide band gap detectors studied in this work, the detection efficiency of TlBr was found highest over the entire range of energy, followed by the HgI2, CdTe, and then by CZT.

  13. New trends in CdTe and CdZnTe detectors for X- and gamma-ray applications

    International Nuclear Information System (INIS)

    The CdTe gamma-ray camera IBIS/ISGRI, on board the INTEGRAL satellite launched in October 2002, is currently the largest spectro-imager of this type in the world. The development of this detector, for research in the field of astrophysics, has provided the opportunity to demonstrate the feasibility of massive integration of CdTe nuclear detectors, taking advantage of the CdTe good spectral performances and high modularity. Many other groups in the world work also to further develop detectors using this material in view of improving its spectral performances (crystal quality, electrode geometry and type, electronics and filtering, etc.), the spatial resolution (pixelization of monolithic crystals) and the detection efficiency at high energy (thickness). In this review, I will detail the main directions in which to strive in order to explore these fields in the upcoming years through examples of techniques or applications

  14. Evaluation of Compton gamma camera prototype based on pixelated CdTe detectors.

    Science.gov (United States)

    Calderón, Y; Chmeissani, M; Kolstein, M; De Lorenzo, G

    2014-06-01

    A proposed Compton camera prototype based on pixelated CdTe is simulated and evaluated in order to establish its feasibility and expected performance in real laboratory tests. The system is based on module units containing a 2×4 array of square CdTe detectors of 10×10 mm(2) area and 2 mm thickness. The detectors are pixelated and stacked forming a 3D detector with voxel sizes of 2 × 1 × 2 mm(3). The camera performance is simulated with Geant4-based Architecture for Medicine-Oriented Simulations(GAMOS) and the Origin Ensemble(OE) algorithm is used for the image reconstruction. The simulation shows that the camera can operate with up to 10(4) Bq source activities with equal efficiency and is completely saturated at 10(9) Bq. The efficiency of the system is evaluated using a simulated (18) F point source phantom in the center of the Field-of-View (FOV) achieving an intrinsic efficiency of 0.4 counts per second per kilobecquerel. The spatial resolution measured from the point spread function (PSF) shows a FWHM of 1.5 mm along the direction perpendicular to the scatterer, making it possible to distinguish two points at 3 mm separation with a peak-to-valley ratio of 8. PMID:24932209

  15. Prompt gamma and neutron detection in BNCT utilizing a CdTe detector.

    Science.gov (United States)

    Winkler, Alexander; Koivunoro, Hanna; Reijonen, Vappu; Auterinen, Iiro; Savolainen, Sauli

    2015-12-01

    In this work, a novel sensor technology based on CdTe detectors was tested for prompt gamma and neutron detection using boronated targets in (epi)thermal neutron beam at FiR1 research reactor in Espoo, Finland. Dedicated neutron filter structures were omitted to enable simultaneous measurement of both gamma and neutron radiation at low reactor power (2.5 kW). Spectra were collected and analyzed in four different setups in order to study the feasibility of the detector to measure 478 keV prompt gamma photons released from the neutron capture reaction of boron-10. The detector proved to have the required sensitivity to detect and separate the signals from both boron neutron and cadmium neutron capture reactions, which makes it a promising candidate for monitoring the spatial and temporal development of in vivo boron distribution in boron neutron capture therapy. PMID:26249745

  16. Improvement of the energy resolution of pixelated CdTe detectors for applications in 0νββ searches

    Science.gov (United States)

    Gleixner, T.; Anton, G.; Filipenko, M.; Seller, P.; Veale, M. C.; Wilson, M. D.; Zang, A.; Michel, T.

    2015-07-01

    Experiments trying to detect 0νββ are very challenging. Their requirements include a good energy resolution and a good detection efficiency. With current fine pixelated CdTe detectors there is a trade off between the energy resolution and the detection efficiency, which limits their performance. It will be shown with simulations that this problem can be mostly negated by analysing the cathode signal which increases the optimal sensor thickness. We will compare different types of fine pixelated CdTe detectors (Timepix, Dosepix, HEXITEC) from this point of view.

  17. Improvement of the energy resolution of pixelated CdTe detectors for applications in 0νββ searches

    International Nuclear Information System (INIS)

    Experiments trying to detect 0νββ are very challenging. Their requirements include a good energy resolution and a good detection efficiency. With current fine pixelated CdTe detectors there is a trade off between the energy resolution and the detection efficiency, which limits their performance. It will be shown with simulations that this problem can be mostly negated by analysing the cathode signal which increases the optimal sensor thickness. We will compare different types of fine pixelated CdTe detectors (Timepix, Dosepix, HEXITEC) from this point of view

  18. Application of a CdTe solid-state detector to polarization-dependent total-reflection fluorescence XAFS measurements

    International Nuclear Information System (INIS)

    A CdTe solid-state detector was applied to the measurement of polarization-dependent total-reflection fluorescence XAFS spectra. The data revealed that the detector has good sensitivity, and this, together with its compact size, make it appropriate for in-situ measurements and removal of X-ray Bragg diffraction. The detector efficiently recorded the high-energy K-edge XAFS spectra for molybdenum oxides supported on TiO2 (110). (au) 10 refs

  19. Simulation studies and spectroscopic measurements of a position sensitive detector based on pixelated CdTe crystals

    OpenAIRE

    Karafasoulis, K.; Zachariadou, K.; Seferlis, S.; Kaissas, I.; Lambropoulos, C.; Loukas, D; Potiriadis, C.

    2010-01-01

    Simulation studies and spectroscopic measurements are presented regarding the development of a pixel multilayer CdTe detector under development in the context of the COCAE project. The instrument will be used for the localization and identification of radioactive sources and radioactively contaminated spots. For the localization task the Compton effect is exploited. The detector response under different radiation fields as well as the overall efficiency of the detector has been evaluated. Spe...

  20. Monte Carlo simulation of the response functions of CdTe detectors to be applied in x-ray spectroscopy

    International Nuclear Information System (INIS)

    In this work, the energy response functions of a CdTe detector were obtained by Monte Carlo (MC) simulation in the energy range from 5 to 160 keV, using the PENELOPE code. In the response calculations the carrier transport features and the detector resolution were included. The computed energy response function was validated through comparison with experimental results obtained with 241Am and 152Eu sources. In order to investigate the influence of the correction by the detector response at diagnostic energy range, x-ray spectra were measured using a CdTe detector (model XR-100T, Amptek), and then corrected by the energy response of the detector using the stripping procedure. Results showed that the CdTe exhibits good energy response at low energies (below 40 keV), showing only small distortions on the measured spectra. For energies below about 80 keV, the contribution of the escape of Cd- and Te-K x-rays produce significant distortions on the measured x-ray spectra. For higher energies, the most important correction is the detector efficiency and the carrier trapping effects. The results showed that, after correction by the energy response, the measured spectra are in good agreement with those provided by a theoretical model of the literature. Finally, our results showed that the detailed knowledge of the response function and a proper correction procedure are fundamental for achieving more accurate spectra from which quality parameters (i.e., half-value layer and homogeneity coefficient) can be determined. - Highlights: • The response function of a CdTe detector was determined by Monte Carlo simulation. • The simulation takes into account all interaction process, the carrier transport and the Gaussian resolution. • The influence of different effects of spectral distortion was investigated. • CdTe detector was applied for x-ray spectroscopy. • The proper correction procedure is needed to achieve realistic x-ray spectra

  1. High short-circuit current density CdTe solar cells using all-electrodeposited semiconductors

    International Nuclear Information System (INIS)

    CdS/CdTe and ZnS/CdTe n–n heterojunction solar cells have been fabricated using all-electrodeposited semiconductors. The best devices show remarkable high short-circuit current densities of 38.5 mAcm−2 and 47.8 mAcm−2, open-circuit voltages of 630 mV and 646 mV and conversion efficiencies of 8.0% and 12.0% respectively. The major strength of these device structures lies in the combination of n–n heterojunction with a large Schottky barrier at the n-CdTe/metal back contact which provides the required band bending for the separation of photo-generated charge carriers. This is in addition to the use of a high quality n-type CdTe absorber layer with high electron mobility. The potential barrier heights estimated for these devices from the current–voltage characteristics exceed 1.09 eV and 1.13 eV for CdS/CdTe and ZnS/CdTe cells respectively. The diode rectification factors of both devices are in excess of four orders of magnitude with reverse saturation current densities of 1.0 × 10−7 Acm−2 and 4.0 × 10−7 Acm−2 respectively. These all-electrodeposited solar cell device structures are currently being studied and developed as an alternative to the well-known p–n junction structures which utilise chemical bath-deposited CdS. The preliminary material growth, device fabrication and assessment results are presented in this paper. - Highlights: • Two-electrode deposition. • High Jsc Schottky barrier solar cells. • CdCl2 + CdF2 treatment

  2. Unipolar charge sensing with coplanar electrodes -- Application to semiconductor detectors

    International Nuclear Information System (INIS)

    A novel method to perform preferential sensing of single-polarity charge carriers in ionization detectors is presented. It achieves the same function as Frisch grids commonly employed in gas ion chambers but uses a coplanar electrode configuration that allows it to be applied to semiconductor detectors. Through the use of this method, good energy resolution can be obtained from room-temperature compound semiconductor detectors despite their poor hole-collection characteristics. Experiment using a CdZnTe detector demonstrates the effectiveness of this technique. Schemes to correct for electron trapping and to obtain position information are also described

  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. A new method for charge-loss correction of room-temperature semiconductor detectors using digital trapezoidal pulse shaping

    International Nuclear Information System (INIS)

    It is well known that semiconductor detectors operating at room temperature can be read out at high rate, with good noise performance and low sensitivity to ballistic deficit, by using trapezoidal (flat-topped) pulse shaping. Nevertheless, the energy resolution of these detectors is also affected by chargetrapping inside the detector crystal, which can not be compensated by the standard trapezoidal pulse shaping. A new digital algorithm based on trapezoidal pulse shaping, to compensate for the charge-trapping effect while minimizing the electronic noise, has been developed. The application of the pulse processing algorithm to a 5 × 5 × 1 mm3 planar Schottky CdTe detector leads to an energy resolution of 1.15% FWHM at 662 keV at room temperature, which is considerably superior to the results of the standard pulse filters.

  5. A Monte Carlo simulation study of the feasibility of a high resolution parallel-hole collimator with a CdTe pixelated semiconductor SPECT system

    International Nuclear Information System (INIS)

    It is recommended that a pixelated parallel-hole collimator in which the hole and pixel sizes are equal be used to improve the sensitivity and spatial resolution when using a small pixel size and a single-photon emission computed tomography (SPECT) system with pixelated semiconductor detector materials (e.g., CdTe and CZT). However, some significant problems arise in the manufacturing of a pixelated parallel-hole collimator. Therefore, we sought to simulate a pixelated semiconductor SPECT system with various collimator geometric designs. The purpose of this study was to compare the quality of images generated with a pixelated semiconductor SPECT system simulated with pixelated parallel-hole collimators of various geometric designs. The sensitivity and spatial resolution of the various collimator geometric designs with varying septal heights and hole sizes were measured. Moreover, to evaluate the overall performance of the imaging system, a hot-rod phantom was designed using a Monte Carlo simulation. According to the results, the average sensitivity using a 15 mm septal height was 1.80, 2.87, and 4.16 times higher than that obtained with septal heights of 20, 25, and 30 mm, respectively. Also, the average spatial resolution using the 30 mm septal height was 44.33, 22.08, and 9.26% better than that attained with 15, 20, and 25 mm septal heights, respectively. When the results acquired with 0.3 and 0.6 mm hole sizes were compared, the average sensitivity with the 0.6 mm hole size was 3.97 times higher than that obtained with the 0.3 mm hole size, and the average spatial resolution with the 0.3 mm hole size was 45.76% better than that with the 0.6 mm hole size. We have presented the pixelated parallel-hole collimators of various collimator geometric designs and evaluations. Our results showed that the effect of various collimator geometric designs can be investigated by Monte Carlo simulation so as to evaluate the feasibility of a high resolution parallel

  6. A Monte Carlo simulation study of the feasibility of a high resolution parallel-hole collimator with a CdTe pixelated semiconductor SPECT system

    Science.gov (United States)

    Lee, Y.-J.; Park, S.-J.; Lee, S.-W.; Kim, D.-H.; Kim, Y.-S.; Jo, B.-D.; Kim, H.-J.

    2013-03-01

    It is recommended that a pixelated parallel-hole collimator in which the hole and pixel sizes are equal be used to improve the sensitivity and spatial resolution when using a small pixel size and a single-photon emission computed tomography (SPECT) system with pixelated semiconductor detector materials (e.g., CdTe and CZT). However, some significant problems arise in the manufacturing of a pixelated parallel-hole collimator. Therefore, we sought to simulate a pixelated semiconductor SPECT system with various collimator geometric designs. The purpose of this study was to compare the quality of images generated with a pixelated semiconductor SPECT system simulated with pixelated parallel-hole collimators of various geometric designs. The sensitivity and spatial resolution of the various collimator geometric designs with varying septal heights and hole sizes were measured. Moreover, to evaluate the overall performance of the imaging system, a hot-rod phantom was designed using a Monte Carlo simulation. According to the results, the average sensitivity using a 15 mm septal height was 1.80, 2.87, and 4.16 times higher than that obtained with septal heights of 20, 25, and 30 mm, respectively. Also, the average spatial resolution using the 30 mm septal height was 44.33, 22.08, and 9.26% better than that attained with 15, 20, and 25 mm septal heights, respectively. When the results acquired with 0.3 and 0.6 mm hole sizes were compared, the average sensitivity with the 0.6 mm hole size was 3.97 times higher than that obtained with the 0.3 mm hole size, and the average spatial resolution with the 0.3 mm hole size was 45.76% better than that with the 0.6 mm hole size. We have presented the pixelated parallel-hole collimators of various collimator geometric designs and evaluations. Our results showed that the effect of various collimator geometric designs can be investigated by Monte Carlo simulation so as to evaluate the feasibility of a high resolution parallel

  7. Front-end electronics for multichannel semiconductor detector systems

    CERN Document Server

    Grybos, P

    2010-01-01

    Front-end electronics for multichannel semiconductor detektor systems Volume 08, EuCARD Editorial Series on Accelerator Science and Technology The monograph is devoted to many different aspects related to front-end electronics for semiconductor detector systems, namely: − designing and testing silicon position sensitive detectors for HEP experiments and X-ray imaging applications, − designing and testing of multichannel readout electronics for semiconductor detectors used in X-ray imaging applications, especially for noise minimization, fast signal processing, crosstalk reduction and good matching performance, − optimization of semiconductor detection systems in respect to the effects of radiation damage. The monograph is the result mainly of the author's experience in the above-mentioned areas and it is an attempt of a comprehensive presentation of issues related to the position sensitive detection system working in a single photon counting mode and intended to X-ray imaging applications. The structure...

  8. Development of a Schottky CdTe Medipix3RX hybrid photon counting detector with spatial and energy resolving capabilities

    Science.gov (United States)

    Gimenez, E. N.; Astromskas, V.; Horswell, I.; Omar, D.; Spiers, J.; Tartoni, N.

    2016-07-01

    A multichip CdTe-Medipix3RX detector system was developed in order to bring the advantages of photon-counting detectors to applications in the hard X-ray range of energies. The detector head consisted of 2×2 Medipix3RX ASICs bump-bonded to a 28 mm×28 mm e- collection Schottky contact CdTe sensor. Schottky CdTe sensors undergo performance degrading polarization which increases with temperature, flux and the longer the HV is applied. Keeping the temperature stable and periodically refreshing the high voltage bias supply was used to minimize the polarization and achieve a stable and reproducible detector response. This leads to good quality images and successful results on the energy resolving capabilities of the system.

  9. Measurement of ionising radiation semiconductor detectors: a review

    International Nuclear Information System (INIS)

    Manufacturing techniques for nuclear detectors using semiconductors are constantly advancing, and a large range of models with different specificities and characteristics are available. After a theoretical reminder, this report describes the main types of detectors, their working and their preferential use. A comparative table guides the neophyte reader in his choice

  10. Characterization of CdTe nuclear detectors for gamma radiation spectrometry

    International Nuclear Information System (INIS)

    The crystallography of CdTe is presented. The characterization of CdTe crystals manufactured at LETI was studied using a spectrometry unit, and an experimental study of surface states and contacts was simultaneously undertaken. A manufacturing process was perfected for the detectors: hand polishing and deposit of a drop of conducting lac. Measurements mode on a great number of materials revealed the interest of chlore doping, the polarization phenomenon associated (the polarization is equivalent to a voltage drop and depends on temperature), the effect of surface states and contacts. It was shown that magnesium doping is a failure and the polarization time constant has a value of about 1 msec. An electron time-of-flight experiment was performed in order to measure the mobilities in the sample at normal temperature: the values obtained are: 70-90 cm2/v.sec for holes and 800-1000 cm2/v.sec for electrons. A trapping level was observed at 0.14eV in a Cl- doped sample; trapping parameters were estimated for a few samples

  11. Applications of CdTe detectors in x-ray imaging and metrology

    International Nuclear Information System (INIS)

    Operating as a photoconductor, the sensitivity and the impulse response of semi-insulating materials greatly depend on the excitation duration compared to electron and hole lifetimes. The characteristic of ohmic contact for these compounds is shortly discussed. Before developing picosecond measurements with integrated autocorrelation system, this paper explains high energy industrial tomographic application with large CdTe detectors (25x15x0.9 mm3) where spatial resolution, contrast and wide dynamic are the main criteria. The excitation is typically micros range. X-ray flash radiography with 10 ns burst, is in an intermediate time domain where excitation is similar to electron life-time in cadmium telluride. In laser fusion experiment the excitation is in the range of 50 ps and the authors develop for such high band devices photoconductive structures able to study very short x-ray emission. Thin polycrystalline MOCVD CdTe films with picosecond response is an alternative material suitable to perform optical correlation measurements of single shot pulses with a very large bandwidth (∼50 GHz)

  12. Studies and development of a readout ASIC for pixelated CdTe detectors for space applications

    International Nuclear Information System (INIS)

    The work presented in this thesis is part of a project where a new instrument is developed: a camera for hard X-rays imaging spectroscopy. It is dedicated to fundamental research for observations in astrophysics, at wavelengths which can only be observed using space-borne instruments. In this domain the spectroscopic accuracy as well as the imaging details are of high importance. This work has been realized at CEA/IRFU (Institut de Recherche sur les lois Fondamentales de l'Univers), which has a long-standing and successful experience in instruments for high energy physics and space physics instrumentation. The objective of this thesis is the design of the readout electronics for a pixelated CdTe detector, suitable for a stacked assembly. The principal parameters of this integrated circuit are a very low noise for reaching a good accuracy in X-ray energy measurement, very low power consumption, a critical parameter in space-borne applications, and a small dead area for the full system combining the detector and the readout electronics. In this work I have studied the limits of these three parameters in order to optimize the circuit. In terms of the spectral resolution, two categories of noise had to be distinguished to determine the final performance. The first is the Fano noise limit, related to detector interaction statistics, which cannot be eliminated. The second is the electronic noise, also unavoidable; however it can be minimized through optimization of the detection chain. Within the detector, establishing a small pixel pitch of 300 μm reduces the input capacitance and the dark current. This limits the effects of the electronic noise. Also in order to limit the input capacitance the future camera is designed as a stacked assembly of the detector with the readout ASIC. This allows to reach extremely good input parameters seen by the readout electronics: a capacitance in range of 0.3 pF-1 pF and a dark current below 5 pA. In the frame of this thesis I have

  13. Experimental evaluation of a-Se and CdTe flat-panel x-ray detectors for digital radiography and fluoroscopy

    Science.gov (United States)

    Adachi, Susumu; Hori, Naoyuki; Sato, Kenji; Tokuda, Satoshi; Sato, Toshiyuki; Uehara, Kazuhiro; Izumi, Yoshihiro; Nagata, Hisashi; Yoshimura, Youji; Yamada, Satoshi

    2000-04-01

    Described are two types of direct-detection flat-panel X-ray detectors utilizing amorphous selenium (a-Se) and cadmium telluride (CdTe). The a-Se detector is fabricated using direct deposition onto a thin film transistor (TFT) substrate, whereas the CdTe detector is fabricated using a novel hybrid method, in which CdTe is pre-deposited onto a glass substrate and then connected to a TFT substrate. The detector array format is 512 X 512 with a pixel pitch of 150 micrometer. The imaging properties of both detectors have been evaluated with respect to X-ray sensitivity, lag, spatial resolution, and detective quantum efficiency (DQE). The modulation transfer functions (MTFs) measured at 1 lp/mm were 0.96 for a- Se and 0.65 for CdTe. The imaging lags after 33 ms were about 4% for a-Se and 22% for CdTe. The DQE values measured at zero spatial frequency were 0.75 for a-Se and 0.22 for CdTe. The results indicate that the a-Se and CdTe detectors have high potential as new digital X-ray imaging devices for both radiography and fluoroscopy.

  14. Continued Development of Small-Pixel CZT and CdTe Detectors for Future High-Angular-Resolution Hard X-ray Missions

    Science.gov (United States)

    Krawczynski, Henric

    The Nuclear Spectroscopic Telescope Array (NuSTAR) Small Explorer Mission was launched in June 2012 and has demonstrated the technical feasibility and high scientific impact of hard X-ray astronomy. We propose to continue our current R&D program to develop finely pixelated semiconductor detectors and the associated readout electronics for the focal plane of a NuSTAR follow-up mission. The detector-ASIC (Application Specific Integrated Circuit) package will be ideally matched to the new generation of low-cost, low-mass X-ray mirrors which achieve an order of magnitude better angular resolution than the NuSTAR mirrors. As part of this program, the Washington University group will optimize the contacts of 2x2 cm^2 footprint Cadmium Zinc Telluride (CZT) and Cadmium Telluride (CdTe) detectors contacted with 100x116 hexagonal pixels at a next-neighbor pitch of 200 microns. The Brookhaven National Laboratory group will design, fabricate, and test the next generation of the HEXID ASIC matched to the new X-ray mirrors and the detectors, providing a low-power 100x116 channel ASIC with extremely low readout noise (i.e. with a root mean square noise of 13 electrons). The detectors will be tested with radioactive sources and in the focal plane of high-angular-resolution X-ray mirrors at the X-ray beam facilities at the Goddard and Marshall Space Flight Centers.

  15. CdTe Focal Plane Detector for Hard X-Ray Focusing Optics

    Science.gov (United States)

    Seller, Paul; Wilson, Matthew D.; Veale, Matthew C.; Schneider, Andreas; Gaskin, Jessica; Wilson-Hodge, Colleen; Christe, Steven; Shih, Albert Y.; Inglis, Andrew; Panessa, Marco

    2015-01-01

    The demand for higher resolution x-ray optics (a few arcseconds or better) in the areas of astrophysics and solar science has, in turn, driven the development of complementary detectors. These detectors should have fine pixels, necessary to appropriately oversample the optics at a given focal length, and an energy response also matched to that of the optics. Rutherford Appleton Laboratory have developed a 3-side buttable, 20 millimeter x 20 millimeter CdTe-based detector with 250 micrometer square pixels (80 x 80 pixels) which achieves 1 kiloelectronvolt FWHM (Full-Width Half-Maximum) @ 60 kiloelectronvolts and gives full spectroscopy between 5 kiloelectronvolts and 200 kiloelectronvolts. An added advantage of these detectors is that they have a full-frame readout rate of 10 kilohertz. Working with NASA Goddard Space Flight Center and Marshall Space Flight Center, 4 of these 1 millimeter-thick CdTe detectors are tiled into a 2 x 2 array for use at the focal plane of a balloon-borne hard-x-ray telescope, and a similar configuration could be suitable for astrophysics and solar space-based missions. This effort encompasses the fabrication and testing of flight-suitable front-end electronics and calibration of the assembled detector arrays. We explain the operation of the pixelated ASIC readout and measurements, front-end electronics development, preliminary X-ray imaging and spectral performance, and plans for full calibration of the detector assemblies. Work done in conjunction with the NASA Centers is funded through the NASA Science Mission Directorate Astrophysics Research and Analysis Program.

  16. Efficiency spectrum of a CdTe X- and γ-ray detector with a Schottky diode

    International Nuclear Information System (INIS)

    A study on the efficiency spectrum of CdTe X- and γ-ray detectors utilizing Schottky diodes for different material parameters and diode structures is reported. Special attention is paid to the effect of deep levels and compensation on space-charge region width. It is shown that charge collection in the neutral region of the detector considerably contributes to the device efficiency. Calculations also show that the efficiency of a stacked detector can be higher than that of a bulk detector with ohmic contacts. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  17. Electrical limitations to energy resolution in semiconductor particle detectors

    International Nuclear Information System (INIS)

    Based on the assumption that the noise contribution of a semiconductor detector is due solely to its bulk properties, equations are presented which indicate the theoretical limits of noise in detectoramplifier combinations. These equations show that an optimum amplifier time-constant and detector bias voltage exist for which condition the minimum noise is independent of the semiconductor resistivity. The optimum performance of a detector-amplifier system is shown to depend only upon detector area, input capacity (less detector capacity), semiconductor minority carrier lifetime and the transconductance of the amplifier input tube. A new detector structure which includes a guard-ring electrode as an integral part of the detector structure is described which has the effect of largely eliminating noise due to surface leakage. Experimental results for detector leakage and energy resolution which agree well with theory are presented. The theoretical limit of noise, expressed as full width at half maximum, is from 7 to 10 keV for 1-cm2 p-type silicon detectors at 25oC. (author)

  18. Photo-responsivity characterizations of CdTe films for direct-conversion X-ray detectors

    International Nuclear Information System (INIS)

    We have fabricated and investigated thin, polycrystalline, cadmium-telluride (CdTe) films in order to utilize them for optical switching readout layers in direct-conversion X-ray detectors. The polycrystalline CdTe films are fabricated on ITO glasses by using the physical vapor deposition (PVD) method at a slow deposition rate and a pressure of 10-6 torr. CdTe films with thicknesses of 5 and 20 μm are grown. The electrical and the optical characteristics of the CdTe films are investigated by measuring the dark-current and the photo-current as functions of the applied field under different wavelengths of light. Higher photo-currents are generated at the longer wavelengths of light for the same applied voltage. When a higher electrical field is applied to the 20 μm-thick CdTe film, a higher dark-current, a higher photo-current, a larger number of charges, and a higher quantum efficiency are generated.

  19. Semiconductor neutron detectors based on new types of materials

    International Nuclear Information System (INIS)

    Neutron detection in hostile environments such as nuclear reactors has been performed using a new kind of semiconductor detector. So far, crystalline semiconductor detectors are not used in nuclear reactor instrumentation because of their sensitivity to radiation damage. For doses in excess of a few tens of kilo rads, radiation induced lattice defects produce a strong loss in the standard semiconductor detector performances. In the last few years, new semiconductor materials having amorphous or polycrystalline structures such as silicon, silicon carbide or CVD diamond, became available. These semiconductors, produced by Chemical Vapor Deposition, come in the form of thin layers being typically a few tens of micron thick. Their crystalline structure is particularly resistant to radiation damage up to a few Mrads but prevent the material use in spectrometry measurements. Nevertheless, these detectors, working in a counting mode, are suitable for the detection of alpha particles produced by the neutron capture reaction with boron. Such thin film detectors have a very poor sensitivity to γ-ray background. Furthermore, they are easier and cheaper to implement than current neutron gas counters. Preliminary results obtained with diamond and amorphous silicon diodes exposed to α particles are presented. (authors). 7 figs., 3 tabs., 11 refs

  20. Low frequency noise in semiconductor detectors

    International Nuclear Information System (INIS)

    Noise characteristics of surface-barrier detectors based on Au contacts on n-Si were measured and analyzed. The metal layers were deposited by evaporation to 40-100 nm thickness. Standard surface-barrier detectors based on Au/Si structures are known to have favorable characteristics, but they tend to degrade with aging and under severe working conditions. Degradation is particularly related to the increase in noise level, leakage current and the reduction of detector efficiency and resolution. Therefore, practical applications of surface-barrier detectors demand their constant upgrading. Improvements of detector properties are concentrated mainly on the front surface and front (rectifying) contact. The aim was to improve the noise characteristics of the surface-barrier structures and retain the favorable detector properties of the Au/Si system. (authors)

  1. Fabrication and utilization of semiconductor radiation detectors

    International Nuclear Information System (INIS)

    This paper describes the assembly of the equipment for the fabrication of Ge-Li drifted detectors and the technique used in the preparation of a Planar detector of 7 cm2 x 0,5 cm for the Laboratory of the Linear Accelerator at the University of Sao Paulo, as well as the utilization of a 22 cm3 coaxial detector for the analysis of fission product gamma rays at the Instituto de Engenharia Nuclear, Rio de Janeiro, R J, Brazil. (author)

  2. 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...

  3. Furnace design for the mercuric iodide crystal growth for new semiconductor radiation detector

    International Nuclear Information System (INIS)

    Mercuric iodide has been attracted an interest for 40 years due to its efficiency as room temperature detector for X and γ-rays. It is worthy to note that commercial γ-ray detectors such as Ge semiconductor detectors should cool down to liquid nitrogen temperature. Compared to other semiconductor detectors such as CdZnTe and CdTe, mercuric iodide has higher efficiency, lower leakage current and less degradation. In addition, mercuric iodide has useful properties such as large band gap of 2.15 eV, low electron-hole pair creation energy of 4.2 eV, and high atomic number (Hg : 80 and I : 53). However, it is difficult to obtain high quality single crystals and the long term reliability problem in devices so that the applications of α-HgI2 are limited. Mercuric iodide undergoes a structural phase transition from an orthorhombic yellow phase (β-HgI2) to a tetragonal red phase (α-HgI2) at 127 .deg. C. In addition, the melting temperature of HgI2 is 259 .deg. C. Thus, when it grows through a melting method over 259 .deg. C, the β-HgI2 phase can be included in the final crystals in the room temperature. In general, in order to grow α-HgI2single crystals, the operating temperature is below 127 .deg. C. Note that the crystals from the solution method have contamination problems and the crystals from the physical vapor method usually display a higher quality with a well defined structure. A good thing for the physical vapor method is that α-HgI2 has high vapor pressure (∼0.1 Torr at 120 .deg. C) indicating that α-HgI2 can be grown in closed ampoules

  4. Development of a modular CdTe detector plane for gamma-ray burst detection below 100 keV

    CERN Document Server

    Ehanno, M; Barret, D; Lacombe, K; Pons, R; Rouaix, G; Gevin, O; Limousin, O; Lugiez, F; Bardoux, A; Penquer, A

    2007-01-01

    We report on the development of an innovative CdTe detector plane (DPIX) optimized for the detection and localization of gamma-ray bursts in the X-ray band (below 100 keV). DPIX is part of an R&D program funded by the French Space Agency (CNES). DPIX builds upon the heritage of the ISGRI instrument, currently operating with great success on the ESA INTEGRAL mission. DPIX is an assembly of 200 elementary modules (XRDPIX) equipped with 32 CdTe Schottky detectors (4x4 mm2, 1 mm thickness) produced by ACRORAD Co. LTD. in Japan. These detectors offer good energy response up to 100 keV. Each XRDPIX is readout by the very low noise front-end electronics chip IDeF-X, currently under development at CEA/DSM/DAPNIA. In this paper, we describe the design of XRDPIX, the main features of the IDeF-X chip, and will present preliminary results of the reading out of one CdTe Schottky detector by the IDeF-X V1.0 chip. A low-energy threshold around 2.7 keV has been measured. This is to be compared with the 12-15 keV threshol...

  5. CdTe and CdZnTe detectors in nuclear medicine

    CERN Document Server

    Scheiber, C

    2000-01-01

    Nuclear medicine diagnostic applications are growing in search for more disease specific or more physiologically relevant imaging. The data are obtained non-invasively from large field gamma cameras or from miniaturised probes. As far as single photon emitters are concerned, often labelled with sup 9 sup 9 sup m Tc (140 keV, gamma), nuclear instrumentation deals with poor counting statistics due to the method of spatial localisation and low contrast to noise due to scatter in the body. Since the 1960s attempts have been made to replace the NaI scintillator by semiconductor detectors with better spectrometric characteristics to improve contrast and quantitative measurements. They allow direct conversion of energy and thus more compact sensors. Room-temperature semiconductor detectors such as cadmium tellure and cadmium zinc tellure have favourable physical characteristics for medical applications which have been investigated in the 1980s. During one decade, they have been used in miniaturised probes such as fo...

  6. A 10 cm × 10 cm CdTe Spectroscopic Imaging Detector based on the HEXITEC ASIC

    International Nuclear Information System (INIS)

    The 250 μ m pitch 80x80 pixel HEXITEC detector systems have shown that spectroscopic imaging with an energy resolution of <1 keV FWHM per pixel can be readily achieved in the range of 5–200 keV with Al-pixel CdTe biased to −500 V. This level of spectroscopic imaging has a variety of applications but the ability to produce large area detectors remains a barrier to the adoption of this technology. The limited size of ASICs and defect free CdTe wafers dictates that building large area monolithic detectors is not presently a viable option. A 3-side buttable detector module has been developed to cover large areas with arrays of smaller detectors. The detector modules are 20.35 × 20.45 mm with CdTe bump bonded to the HEXITEC ASIC with coverage up to the edge of the module on three sides. The fourth side has a space of 3 mm to allow I/O wire bonds to be made between the ASIC and the edge of a PCB that routes the signals to a connector underneath the active area of the module. The detector modules have been assembled in rows of five modules with a dead space of 170 μ m between each module. Five rows of modules have been assembled in a staggered height array where the wire bonds of one row of modules are covered by the active detector area of a neighboring row. A data acquisition system has been developed to digitise, store and output the 24 Gbit/s data that is generated by the array. The maximum bias magnitude that could be applied to the CdTe detectors from the common voltage source was limited by the worst performing detector module. In this array of detectors a bias of −400 V was used and the detector modules had 93 % of pixels with better than 1.2 keV FWHM at 59.5 keV. An example of K-edge enhanced imaging for mammography was demonstrated. Subtracting images from the events directly above and below the K-edge of the Iodine contrast agent was able to extract the Iodine information from the image of a breast phantom and improve the contrast of the images

  7. CdZnTe and CdTe detector arrays for hard X-ray and gamma-ray astronomy

    International Nuclear Information System (INIS)

    A variety of CdZnTe and CdTe detector arrays were fabricated at NASA/GSFC for use in hard X-ray and gamma-ray astronomy. Mosaic, pixel, and 3-D position-sensitive detector arrays were built to demonstrate the capabilities for high-resolution imaging and spectroscopy for 10 to 2 MeV. This paper will summarize the different arrays and their applications for instruments being developed at NASA/GSFC. Specific topics to be addressed include materials characterization, fabrication of detectors, ASIC readout electronics, and imaging and spectroscopy tests

  8. CdZnTe and CdTe detector arrays for hard X-ray and gamma-ray astronomy

    Energy Technology Data Exchange (ETDEWEB)

    Stahle, C.M. E-mail: carl.stahle@gsfc.nasa.gov; Parker, B.H.; Parsons, A.M.; Barbier, L.M.; Barthelmy, S.D.; Gehrels, N.A.; Palmer, D.M.; Snodgrass, S.J.; Tueller, J

    1999-10-21

    A variety of CdZnTe and CdTe detector arrays were fabricated at NASA/GSFC for use in hard X-ray and gamma-ray astronomy. Mosaic, pixel, and 3-D position-sensitive detector arrays were built to demonstrate the capabilities for high-resolution imaging and spectroscopy for 10 to 2 MeV. This paper will summarize the different arrays and their applications for instruments being developed at NASA/GSFC. Specific topics to be addressed include materials characterization, fabrication of detectors, ASIC readout electronics, and imaging and spectroscopy tests.

  9. Integrated superconducting detectors on semiconductors for quantum optics applications

    Science.gov (United States)

    Kaniber, M.; Flassig, F.; Reithmaier, G.; Gross, R.; Finley, J. J.

    2016-05-01

    Semiconductor quantum photonic circuits can be used to efficiently generate, manipulate, route and exploit nonclassical states of light for distributed photon-based quantum information technologies. In this article, we review our recent achievements on the growth, nanofabrication and integration of high-quality, superconducting niobium nitride thin films on optically active, semiconducting GaAs substrates and their patterning to realize highly efficient and ultra-fast superconducting detectors on semiconductor nanomaterials containing quantum dots. Our state-of-the-art detectors reach external detection quantum efficiencies up to 20 % for ~4 nm thin films and single-photon timing resolutions integration of such detectors into quantum dot-loaded, semiconductor ridge waveguides, resulting in the on-chip, time-resolved detection of quantum dot luminescence. Furthermore, a prototype quantum optical circuit is demonstrated that enabled the on-chip generation of resonance fluorescence from an individual InGaAs quantum dot, with a linewidth <15 μeV displaced by 1 mm from the superconducting detector on the very same semiconductor chip. Thus, all key components required for prototype quantum photonic circuits with sources, optical components and detectors on the same chip are reported.

  10. The Si/CdTe semiconductor Compton camera of the ASTRO-H Soft Gamma-ray Detector (SGD)

    International Nuclear Information System (INIS)

    The Soft Gamma-ray Detector (SGD) is one of the instrument payloads onboard ASTRO-H, and will cover a wide energy band (60–600 keV) at a background level 10 times better than instruments currently in orbit. The SGD achieves low background by combining a Compton camera scheme with a narrow field-of-view active shield. The Compton camera in the SGD is realized as a hybrid semiconductor detector system which consists of silicon and cadmium telluride (CdTe) sensors. The design of the SGD Compton camera has been finalized and the final prototype, which has the same configuration as the flight model, has been fabricated for performance evaluation. The Compton camera has overall dimensions of 12 cm×12 cm×12 cm, consisting of 32 layers of Si pixel sensors and 8 layers of CdTe pixel sensors surrounded by 2 layers of CdTe pixel sensors. The detection efficiency of the Compton camera reaches about 15% and 3% for 100 keV and 511 keV gamma rays, respectively. The pixel pitch of the Si and CdTe sensors is 3.2 mm, and the signals from all 13,312 pixels are processed by 208 ASICs developed for the SGD. Good energy resolution is afforded by semiconductor sensors and low noise ASICs, and the obtained energy resolutions with the prototype Si and CdTe pixel sensors are 1.0–2.0 keV (FWHM) at 60 keV and 1.6–2.5 keV (FWHM) at 122 keV, respectively. This results in good background rejection capability due to better constraints on Compton kinematics. Compton camera energy resolutions achieved with the final prototype are 6.3 keV (FWHM) at 356 keV and 10.5 keV (FWHM) at 662 keV, which satisfy the instrument requirements for the SGD Compton camera (better than 2%). Moreover, a low intrinsic background has been confirmed by the background measurement with the final prototype. - Highlights: • The final prototype of the Si/CdTe Compton camera for the ASTRO-H SGD was completed. • The detailed design of the Compton camera is described. • The unprecedented high efficiency and high

  11. Fast timing methods for semiconductor detectors. Revision

    International Nuclear Information System (INIS)

    This tutorial paper discusses the basic parameters which determine the accuracy of timing measurements and their effect in a practical application, specifically timing with thin-surface barrier detectors. The discussion focusses on properties of the detector, low-noise amplifiers, trigger circuits and time converters. New material presented in this paper includes bipolar transistor input stages with noise performance superior to currently available FETs, noiseless input terminations in sub-nanosecond preamplifiers and methods using transmission lines to couple the detector to remotely mounted preamplifiers. Trigger circuits are characterized in terms of effective rise time, equivalent input noise and residual jitter

  12. Theoretical framework for mapping pulse shapes in semiconductor radiation detectors

    CERN Document Server

    Prettyman, T H

    1999-01-01

    An efficient method for calculating of charge pulses produced by semiconductor detectors is presented. The method is based on a quasi-steady-state model for semiconductor detector operation. A complete description of the model and underlying assumptions is given. Mapping of charge pulses is accomplished by solving an adjoint carrier continuity equation. The solution of the adjoint equation yields Green's function, a time- and position-dependent map that contains all possible charge pulses that can be produced by the detector for charge generated at discrete locations (e.g., by gamma-ray interactions). Because the map is generated by solving a single, time-dependent problem, the potential for reduction in computational effort over direct mapping methods is significant, particularly for detectors with complex electrode structures. In this paper, the adjoint equation is presented and the mapping method is validated for a benchmark problem.

  13. Development of the semiconductor detector of lead iodide

    International Nuclear Information System (INIS)

    Lead iodide (PbI2) crystal is one of the most promising semiconductor detectors to be operated at room temperature. It is a semiconductor with a wide band gap energy and high atomic numbers. The preparation of a detector crystal consists of the purification of starting material, in quartz ampoules, by zone refining technique and growth of crystals by Bridgman method. The ability to obtain high purity crystals containing a relatively low number of defects and the physical-chemistry characterization are necessary pre-requisites for the production of good quality radiation detectors. This work reports the lead iodide monocrystal purification and growth methods to obtain those crystals with appropriate characteristics for their application as radiation detectors. (author)

  14. Dosimetry study on A p-n junction semiconductor detector

    International Nuclear Information System (INIS)

    A p-n junction semiconductor may be used as a radiation detector. Such a study is reported here. Its dosimetry specificities, include dose, dose rate, precision, stability, depth dose distribution and directional response, were studied in a 60Co field. It is shown that the detector performs well. It exhibited a precision of ±0.05% (std dev.) and a stability of ±0.16% (std dev.), respectively. (author)

  15. A simulation of a CdTe gamma ray detector based on collection efficiency profiles as determined by lateral IBIC

    International Nuclear Information System (INIS)

    Collection efficiency profiles as determined by the ion beam-induced charge (IBIC) technique have been considered to evaluate the spectroscopic performance of a cadmium telluride (CdTe) nuclear radiation detector. The dependence of such profiles on the applied bias voltage and the shaping time are presented and discussed on the basis of a theoretical model, which is also used to evaluate the electron/hole collection lengths profiles. Experimental collection efficiency profiles were used as input data of the 'ISIDE' Monte Carlo programme to simulate the CdTe response to gamma rays produced by 57Co. A systematic investigation of such spectra obtained under different detection conditions shows the effects of non constant collection efficiency profiles and ballistic deficit on the energy resolution of the detector

  16. A simulation of a CdTe gamma ray detector based on collection efficiency profiles as determined by lateral IBIC

    CERN Document Server

    Vittone, E; Lo Giudice, A; Polesello, P; Manfredotti, C

    1999-01-01

    Collection efficiency profiles as determined by the ion beam-induced charge (IBIC) technique have been considered to evaluate the spectroscopic performance of a cadmium telluride (CdTe) nuclear radiation detector. The dependence of such profiles on the applied bias voltage and the shaping time are presented and discussed on the basis of a theoretical model, which is also used to evaluate the electron/hole collection lengths profiles. Experimental collection efficiency profiles were used as input data of the 'ISIDE' Monte Carlo programme to simulate the CdTe response to gamma rays produced by sup 5 sup 7 Co. A systematic investigation of such spectra obtained under different detection conditions shows the effects of non constant collection efficiency profiles and ballistic deficit on the energy resolution of the detector.

  17. A simulation of a CdTe gamma ray detector based on collection efficiency profiles as determined by lateral IBIC

    Science.gov (United States)

    Vittone, E.; Fizzotti, F.; Lo Giudice, A.; Polesello, P.; Manfredotti, C.

    1999-06-01

    Collection efficiency profiles as determined by the ion beam-induced charge (IBIC) technique have been considered to evaluate the spectroscopic performance of a cadmium telluride (CdTe) nuclear radiation detector. The dependence of such profiles on the applied bias voltage and the shaping time are presented and discussed on the basis of a theoretical model, which is also used to evaluate the electron/hole collection lengths profiles. Experimental collection efficiency profiles were used as input data of the "ISIDE" Monte Carlo programme to simulate the CdTe response to gamma rays produced by 57Co. A systematic investigation of such spectra obtained under different detection conditions shows the effects of non constant collection efficiency profiles and ballistic deficit on the energy resolution of the detector.

  18. Mercuric iodide semiconductor detectors encapsulated in polymeric resin

    Energy Technology Data Exchange (ETDEWEB)

    Martins, Joao F. Trencher; Santos, Robinson A. dos; Ferraz, Caue de M.; Oliveira, Adriano S.; Velo, Alexandre F.; Mesquita, Carlos H. de; Hamada, Margarida M., E-mail: mmhamada@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Disch, Christian; Fiederle, Michael [Albert-Ludwigs Universität Freiburg - UniFreibrug, Freiburg Materials Research Center - FMF, Freiburg (Germany)

    2015-07-01

    The development of new semiconductor radiation detectors always finds many setback factors, such as: high concentration of impurities in the start materials, poor long term stability, the surface oxidation and other difficulties discussed extensively in the literature, that limit their use. In this work was studied, the application of a coating resin on HgI2 detectors, in order to protect the semiconductor crystal reactions from atmospheric gases and to isolate electrically the surface of the crystals. Four polymeric resins were analyzed: Resin 1: 50% - 100%Heptane, 10% - 25% methylcyclohexane, <1% cyclohexane; Resin 2: 25% - 50% ethanol, 25% - 50% acetone, <2,5% ethylacetate; Resin 3: 50% - 100% methylacetate, 5% - 10% n-butylacetate; Resin 4: 50% - 100% ethyl-2-cyanacrylat. The influence of the polymeric resin type used on the spectroscopic performance of the HgI{sub 2} semiconductor detector is, clearly, demonstrated. The better result was found for the detector encapsulated with Resin 3. An increase of up to 26 times at the stability time was observed for the detectors encapsulated compared to that non-encapsulated detector. (author)

  19. Mercuric iodide semiconductor detectors encapsulated in polymeric resin

    International Nuclear Information System (INIS)

    The development of new semiconductor radiation detectors always finds many setback factors, such as: high concentration of impurities in the start materials, poor long term stability, the surface oxidation and other difficulties discussed extensively in the literature, that limit their use. In this work was studied, the application of a coating resin on HgI2 detectors, in order to protect the semiconductor crystal reactions from atmospheric gases and to isolate electrically the surface of the crystals. Four polymeric resins were analyzed: Resin 1: 50% - 100%Heptane, 10% - 25% methylcyclohexane, <1% cyclohexane; Resin 2: 25% - 50% ethanol, 25% - 50% acetone, <2,5% ethylacetate; Resin 3: 50% - 100% methylacetate, 5% - 10% n-butylacetate; Resin 4: 50% - 100% ethyl-2-cyanacrylat. The influence of the polymeric resin type used on the spectroscopic performance of the HgI2 semiconductor detector is, clearly, demonstrated. The better result was found for the detector encapsulated with Resin 3. An increase of up to 26 times at the stability time was observed for the detectors encapsulated compared to that non-encapsulated detector. (author)

  20. Simulation studies and spectroscopic measurements of a position sensitive detector based on pixelated CdTe crystals

    CERN Document Server

    Karafasoulis, K; Seferlis, S; Kaissas, I; Lambropoulos, C; Loukas, D; Potiriadis, C

    2010-01-01

    Simulation studies and spectroscopic measurements are presented regarding the development of a pixel multilayer CdTe detector under development in the context of the COCAE project. The instrument will be used for the localization and identification of radioactive sources and radioactively contaminated spots. For the localization task the Compton effect is exploited. The detector response under different radiation fields as well as the overall efficiency of the detector has been evaluated. Spectroscopic measurements have been performed to evaluate the energy resolution of the detector. The efficiency of the event reconstruction has been studied in a wide range of initial photon energies by exploiting the detector's angular resolution measure distribution. Furthermore, the ability of the COCAE detector to localize radioactive sources has been investigated.

  1. Spectra of radioactive nuclides radiation, measured with semiconductor detectors. 2

    International Nuclear Information System (INIS)

    The second part of the atlas 'Radiation spectra of radionuclides measured with semiconductor detectors' is presented including 259 spectra of 126 alpha, beta, gamma, and X ray emitters. Some spectra of the first part of the atlas are given at another scale and sometimes for other energy ranges. The total number of investigated radionuclides amounts to 261 of which 69 are new ones

  2. Charge collection efficiency and space charge formation in CdTe gamma and X-ray detectors

    International Nuclear Information System (INIS)

    A new extended model for the charge collection efficiency in CdTe gamma and X ray detectors is presented which allows to derive from apparent experimental gamma spectra of a quasi-monochromatic source, an 241Am source in the present case, not only the μτ products of electrons and holes individually but also the sign, spatial distribution, and temporal evolution of the net space charge accumulated in the detector. Resistive CdTe and CdZnTe as well as CdTe Schottky detectors are studied. While the resistive type is stable in time and exhibits higher μτ products, the Schottky type shows space charge accumulation which approaches saturation after about 1 h at several 1011 cm-3. This is attributed to efficient majority carrier depletion, Fermi level shift, and trap filling. Resistive detectors thus appear optimized to the needs of gamma spectroscopy even at low bias voltage, while Schottky types need higher bias to overcome the space charge. They are suited to both, gamma spectroscopy and X-ray detection in analog current mode, where they operate more stably due to the higher bias. From the point of view of materials characterization, gamma spectroscopy with Schottky detectors probes and reveals the trap density near the Fermi level (several 1012 cm-3 eV-1). We find a basically homogeneous spatial distribution suggesting the trap origin being in crystal growth rather than surface processing. Capture of photogenerated charges in traps is detrimental for current-mode operation under high X-ray flux because delayed emission from traps limits the detector''s ability to respond to fast signal changes. (orig.)

  3. Development of a CdTe pixel detector with a window comparator ASIC for high energy X-ray applications

    Science.gov (United States)

    Hirono, T.; Toyokawa, H.; Furukawa, Y.; Honma, T.; Ikeda, H.; Kawase, M.; Koganezawa, T.; Ohata, T.; Sato, M.; Sato, G.; Takagaki, M.; Takahashi, T.; Watanabe, S.

    2011-09-01

    We have developed a photon-counting-type CdTe pixel detector (SP8-01). SP8-01 was designed as a prototype of a high-energy X-ray imaging detector for experiments using synchrotron radiation. SP8-01 has a CdTe sensor of 500 μm thickness, which has an absorption efficiency of almost 100% up to 50 keV and 45% even at 100 keV. A full-custom application specific integrated circuit (ASIC) was designed as a readout circuit of SP8-01, which is equipped with a window-type discriminator. The upper discriminator realizes a low-background measurement, because X-ray beams from the monochromator contain higher-order components beside the fundamental X-rays in general. ASIC chips were fabricated with a TSMC 0.25 μm CMOS process, and CdTe sensors were bump-bonded to the ASIC chips by a gold-stud bonding technique. Beam tests were performed at SPring-8. SP8-01 detected X-rays up to 120 keV. The capability of SP8-01 as an imaging detector for high-energy X-ray synchrotron radiation was evaluated with its performance characteristics.

  4. Design and optimization of large area thin-film CdTe detector for radiation therapy imaging applications

    International Nuclear Information System (INIS)

    Purpose: The authors investigate performance of thin-film cadmium telluride (CdTe) in detecting high-energy (6 MV) x rays. The utilization of this material has become technologically feasible only in recent years due to significant development in large area photovoltaic applications. Methods: The CdTe film is combined with a metal plate, facilitating conversion of incoming photons into secondary electrons. The system modeling is based on the Monte Carlo simulations performed to determine the optimized CdTe layer thickness in combination with various converter materials. Results: The authors establish a range of optimal parameters producing the highest DQE due to energy absorption, as well as signal and noise spatial spreading. The authors also analyze the influence of the patient scatter on image formation for a set of detector configurations. The results of absorbed energy simulation are used in device operation modeling to predict the detector output signal. Finally, the authors verify modeling results experimentally for the lowest considered device thickness. Conclusions: The proposed CdTe-based large area thin-film detector has a potential of becoming an efficient low-cost electronic portal imaging device for radiation therapy applications.

  5. Characterization measurement of a thick CdTe detector for BNCT-SPECT – Detection efficiency and energy resolution

    International Nuclear Information System (INIS)

    Author's group is carrying out development of BNCT-SPECT with CdTe device, which monitors the therapy effect of BNCT in real-time. From the design calculations, the dimensions were fixed to 1.5×2×30 mm3. For the collimator it was confirmed that it would have a good spatial resolution and simultaneously the number of counts would be acceptably large. After producing the CdTe crystal, the characterization measurement was carried out. For the detection efficiency an excellent agreement between calculation and measurement was obtained. Also, the detector has a very good energy resolution so that gamma-rays of 478 keV and 511 keV could be distinguished in the spectrum. - Highlights: • BNCT-SPECT is developed with CdTe device to estimate therapy effect of BNCT. • By design calculations, CdTe dimensions are determined to be 1.5×2×30 mm3. Collimator length is 10 cm with 2 mm diameter hole. • Producing the crystal, efficiency and energy resolution were measured. • Excellent agreement was obtained between measurement and calculation. Discrimination of 478 keV and 511 keV was confirmed in the spectrum

  6. Semiconductor detectors and double beta decay

    International Nuclear Information System (INIS)

    The underlying theory of double beta decay is discussed as well as some experimental observations. A class of second generation 76Ge detector experiments is then discussed. The design and physics considerations involved in the system used by LBL are explained, particularly the means of rejecting background activity. 24 references, 18 figures, 3 tables

  7. A nuclear spectrum generator for semiconductor X-ray detectors

    International Nuclear Information System (INIS)

    A nuclear spectrum generator for semiconductor X-ray detectors is designed in this paper. It outputs step ramp signals with random distribution in amplitude and time according to specified reference spectrum. The signals are similar to the signals from an actual semiconductor X-ray detector, and can be use to check spectrum response characteristics of an X-ray fluorometer. This helps improving energy resolution of the X-ray fluorometer. The spectrum generator outputs step ramp signals satisfying the probability density distribution function of any given reference spectrum in amplitude through sampling on the basis of 32-bit randomizer. The system splits 1024 interval segmentation of the time that the step ramp signals appear, and calculates the appearance probability of step ramp signals in different intervals and the average time between the time intervals, by random sampling. The step ramp signals can meet the rule of exponential distribution in time. Test results of the spectrum generator show that the system noise is less than 2.43 mV, the output step ramp signals meet the Poisson distribution in counting rate and the probability density distribution function of the reference spectrum in amplitude. The counting rate of the output step ramp signals can be adjusted. It meets the rule of the output signals from semiconductor X-ray detectors, such as Si-pin detector and silicon drift detector. (authors)

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

    International Nuclear Information System (INIS)

    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 planar detectors. The following review paper is divided into three parts: The first part discusses detector contact configurations for enhancing photopeak efficiencies and the single carrier collection approach which leads to improved energy resolutions and photopeak efficiencies at high gamma ray energies. The second part demonstrates excellent spectroscopic results using thick CdZnTe segmented monolithic pad and strip detectors showing energy resolutions less than 2% FWHM at 356 keV gamma rays. The third part discusses advantages and disadvantages of CdTe and CdZnTe detectors in imaging systems and describes new developments for medical diagnostics imaging systems

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

    Science.gov (United States)

    Eisen, Y.; Shor, A.; Mardor, I.

    1999-06-01

    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 planar detectors. The following review paper is divided into three parts: The first part discusses detector contact configurations for enhancing photopeak efficiencies and the single carrier collection approach which leads to improved energy resolutions and photopeak efficiencies at high gamma ray energies. The second part demonstrates excellent spectroscopic results using thick CdZnTe segmented monolithic pad and strip detectors showing energy resolutions less than 2% FWHM at 356 keV gamma rays. The third part discusses advantages and disadvantages of CdTe and CdZnTe detectors in imaging systems and describes new developments for medical diagnostics imaging systems.

  10. Monte Carlo simulation of the response functions of CdTe detectors to be applied in x-ray spectroscopy.

    Science.gov (United States)

    Tomal, A; Santos, J C; Costa, P R; Lopez Gonzales, A H; Poletti, M E

    2015-06-01

    In this work, the energy response functions of a CdTe detector were obtained by Monte Carlo (MC) simulation in the energy range from 5 to 160keV, using the PENELOPE code. In the response calculations the carrier transport features and the detector resolution were included. The computed energy response function was validated through comparison with experimental results obtained with (241)Am and (152)Eu sources. In order to investigate the influence of the correction by the detector response at diagnostic energy range, x-ray spectra were measured using a CdTe detector (model XR-100T, Amptek), and then corrected by the energy response of the detector using the stripping procedure. Results showed that the CdTe exhibits good energy response at low energies (below 40keV), showing only small distortions on the measured spectra. For energies below about 80keV, the contribution of the escape of Cd- and Te-K x-rays produce significant distortions on the measured x-ray spectra. For higher energies, the most important correction is the detector efficiency and the carrier trapping effects. The results showed that, after correction by the energy response, the measured spectra are in good agreement with those provided by a theoretical model of the literature. Finally, our results showed that the detailed knowledge of the response function and a proper correction procedure are fundamental for achieving more accurate spectra from which quality parameters (i.e., half-value layer and homogeneity coefficient) can be determined. PMID:25599872

  11. Charge collection efficiency and space charge formation in CdTe gamma and X-ray detectors

    Science.gov (United States)

    Matz, R.; Weidner, M.

    1998-02-01

    A new extended model for the charge collection efficiency in CdTe gamma and X ray detectors is presented which allows to derive from apparent experimental gamma spectra of a quasi-monochromatic source, an 241Am source in the present case, not only the μρ products of electrons and holes individually but also the sign, spatial distribution, and temporal evolution of the net space charge accumulated in the detector. Resistive CdTe and CdZnTe as well as CdTe Schottky detectors are studied. While the resistive type is stable in time and exhibits higher μτ products, the Schottky type shows space charge accumulation which approaches saturation after about 1 h at several 10 11 cm -3. This is attributed to efficient majority carrier depletion, Fermi level shift, and trap filling. Resistive detectors thus appear optimized to the needs of gamma spectroscopy even at low bias voltage, while Schottky types need higher bias to overcome the space charge. They are suited to both, gamma spectroscopy and X-ray detection in analog current mode, where they operate more stably due ρo the higher bias. From the point of view of materials characterization, gamma spectroscopy with Schottky detectors probes and reveals the trap density near the Fermi level (several 10 12 cm -3 eV -1). We find a basically homogeneous spatial distribution suggesting the trap origin being in crystal growth rather than surface processing. Capture of photogenerated charges in traps is detrimental for current-mode operation under high X-ray flux because delayed emission from traps limits the detector's ability to respond to fast signal changes.

  12. Contribution to the manufacture of silicon semiconductor detectors

    International Nuclear Information System (INIS)

    Production methods used for making silicon semi-conductor detectors at the Nuclear Physics Laboratory in Grenoble are described. Detectors are of two types, either the lithium-compensated p.i.n. type up to 3.5 mm thick, or the surface barrier type from 2 mm down to 10 μ thick. The research into the surface barrier type concerned essentially the resolving power of the chemical contact obtained by Be evaporation (or Ni deposit), after a chemical attack (type C.P.I.) which is thickness-controlled and which gives a low surface current and a satisfactory flatness. The resolving power obtained (α 8.78 MeV, T ≅ - 20 deg. C) is of the order of 20 keV for thick detectors (surface barrier) and ≅ 50 keV for very thin detectors (10 μ), and for p.i.n. type detectors (≅ 50 keV at T + 20 deg. C). (author)

  13. Electrochemical Deposition of CdTe Semiconductor Thin Films for Solar Cell Application Using Two-Electrode and Three-Electrode Configurations: A Comparative Study

    Directory of Open Access Journals (Sweden)

    O. K. Echendu

    2016-01-01

    Full Text Available Thin films of CdTe semiconductor were electrochemically deposited using two-electrode and three-electrode configurations in potentiostatic mode for comparison. Cadmium sulphate and tellurium dioxide were used as cadmium and tellurium sources, respectively. The layers obtained using both configurations exhibit similar structural, optical, and electrical properties with no specific dependence on any particular electrode configuration used. These results indicate that electrochemical deposition (electrodeposition of CdTe and semiconductors in general can equally be carried out using two-electrode system as well as the conventional three-electrode system without compromising the essential qualities of the materials produced. The results also highlight the advantages of the two-electrode configuration in process simplification, cost reduction, and removal of a possible impurity source in the growth system, especially as the reference electrode ages.

  14. K-edge imaging with the XPAD3 hybrid pixel detector, direct comparison of CdTe and Si sensors

    International Nuclear Information System (INIS)

    We investigate the improvement from the use of high-Z CdTe sensors for pre-clinical K-edge imaging with the hybrid pixel detectors XPAD3. We compare XPAD3 chips bump bonded to Si or CdTe sensors in identical experimental conditions. Image performance for narrow energy bin acquisitions and contrast-to-noise ratios of K-edge images are presented and compared. CdTe sensors achieve signal-to-noise ratios at least three times higher than Si sensors within narrow energy bins, thanks to their much higher detection efficiency. Nevertheless Si sensors provide better contrast-to-noise ratios in K-edge imaging when working at equivalent counting statistics, due to their better estimation of the attenuation coefficient of the contrast agent. Results are compared to simulated data in the case of the XPAD3/Si detector. Good agreement is observed when including charge sharing between pixels, which have a strong impact on contrast-to-noise ratios in K-edge images. (paper)

  15. K-edge imaging with the XPAD3 hybrid pixel detector, direct comparison of CdTe and Si sensors

    Science.gov (United States)

    Cassol, F.; Portal, L.; Graber-Bolis, J.; Perez-Ponce, H.; Dupont, M.; Kronland, C.; Boursier, Y.; Blanc, N.; Bompard, F.; Boudet, N.; Buton, C.; Clémens, J. C.; Dawiec, A.; Debarbieux, F.; Delpierre, P.; Hustache, S.; Vigeolas, E.; Morel, C.

    2015-07-01

    We investigate the improvement from the use of high-Z CdTe sensors for pre-clinical K-edge imaging with the hybrid pixel detectors XPAD3. We compare XPAD3 chips bump bonded to Si or CdTe sensors in identical experimental conditions. Image performance for narrow energy bin acquisitions and contrast-to-noise ratios of K-edge images are presented and compared. CdTe sensors achieve signal-to-noise ratios at least three times higher than Si sensors within narrow energy bins, thanks to their much higher detection efficiency. Nevertheless Si sensors provide better contrast-to-noise ratios in K-edge imaging when working at equivalent counting statistics, due to their better estimation of the attenuation coefficient of the contrast agent. Results are compared to simulated data in the case of the XPAD3/Si detector. Good agreement is observed when including charge sharing between pixels, which have a strong impact on contrast-to-noise ratios in K-edge images.

  16. Measurement 20-200 keV hard X-ray based on CdTe detector in EAST Tokamak

    International Nuclear Information System (INIS)

    Background: Accurate and quantitative measurement of plasma radiation is a key issue to Tokamak, toroidal magnetic confinement device. The radiations from Tokamak cover large energy range. Driven by the determination of the obtaining of hard X-ray spectra, a new system based on a high performance CdTe detector was built up in EAST Tokamak, the first non-circle cross-section in the world. Purpose: Introduces the device of hard X-ray diagnosis system in the EAST Tokamak on the Port A. The system can measure the plasma hard X-ray (20-200 keV) spectra under different discharge conditions, including Ohmical shot and Lower Hybrid Current Drive (LHCD) shot. The research of high speed electron which produced by LHCD is also the aim of the new system. Methods: A high performance CdTe detector was using in EAST Tokamak to measure the hard X-ray (20-200 keV) spectra. Results: The results show that the new system based on a high performance CdTe can meet the requirements for measuring the EAST Tokamak. Conclusions: A preliminary experimental result showed that the system can meet the requirements for measuring the X-ray bremsstrahlung of plasma in the energy range from 20 to 200 keV Calibration result and typical measurement result on EAST are present in this paper. (authors)

  17. Spectroscopy of low energy solar neutrinos using CdTe detectors

    OpenAIRE

    Zuber, K.

    2002-01-01

    The usage of a large amount of CdTe(CdZnTe) semiconductor detectors for solar neutrino spectroscopy in the low energy region is investigated. Several different coincidence signals can be formed on five different isotopes to measure the Be-7 neutrino line at 862 keV in real-time. The most promising one is the usage of Cd-116 resulting in 89 SNU. The presence of Te-125 permits even the real-time detection of pp-neutrinos. A possible antineutrino flux above 713 keV might be detected by capture o...

  18. Characterization measurement of a thick CdTe detector for BNCT-SPECT - detection efficiency and energy resolution.

    Science.gov (United States)

    Murata, Isao; Nakamura, Soichiro; Manabe, Masanobu; Miyamaru, Hiroyuki; Kato, Itsuro

    2014-06-01

    Author׳s group is carrying out development of BNCT-SPECT with CdTe device, which monitors the therapy effect of BNCT in real-time. From the design calculations, the dimensions were fixed to 1.5×2×30mm(3). For the collimator it was confirmed that it would have a good spatial resolution and simultaneously the number of counts would be acceptably large. After producing the CdTe crystal, the characterization measurement was carried out. For the detection efficiency an excellent agreement between calculation and measurement was obtained. Also, the detector has a very good energy resolution so that gamma-rays of 478keV and 511keV could be distinguished in the spectrum. PMID:24581600

  19. Technological aspects of development of pixel and strip detectors based on CdTe and CdZnTe

    Energy Technology Data Exchange (ETDEWEB)

    Gostilo, V.; Ivanov, V.; Kostenko, S.; Lisjutin, I.; Loupilov, A.; Nenonen, S.; Sipila, H.; Valpas, K

    2001-03-11

    Current and spectrometrical characteristics, stability in time and reliability of pixel and strip detectors depend on initial material properties, crystal processing quality and contacts manufacture technology. The work presents analysis of current-voltage and spectrometrical characteristics for initial CdTe and CdZnTe crystals applied for pixel and strip detectors manufacture. The crystal surface preparation before contacts manufacture comprises a modified technology. The contacts were made by photolithography with the surface protected by photoresist with further windows lift-off and crystal surface metallization in lifted-off windows. Metal pads were made by gold deposition from chloroauric acid. Thermocompression, ultrasonic and pulse wirebonding, as well as traditional contacts glueing method for CdTe and CdZnTe detectors have been tested for contacts wiring. The pulse wirebonding has revealed the best results. Wiring is made of gold wire with a diameter of 30 {mu}m and is good enough for pixel and strip wirebonding, providing rather low labour-intensiveness for their assembly by standard equipment. The possibility of fabrication of pressing contacts to strip and pixel detectors by Zebra elastomeric connectors has been investigated. The pressing contacts have provided qualitative and reliable electrical contact and signal layout from pixels and strips to readout electronics. Developed technologies were applied in the manufacture of the following CdTe and CdZnTe detectors: 4x4 pixels detector with rectangular pixels 0.65x0.65 mm and pitch 0.75 mm; 4x4 pixels ring miltiple-electrode detector with anode diameter 0.32 mm and pitch 0.75 mm; strip detector with 100 {mu}m width strip and 125 {mu}m pitch. The 4x4 pixels CdZnTe detector has provided at optimal temperature energy resolutions of 808 eV and 1.19 keV at energies of 5.9 and 59.6 keV, respectively. Interstrip resistance between two strips with a distance of 25 {mu}m on detector was 2-8 G{omega}.

  20. Technological aspects of development of pixel and strip detectors based on CdTe and CdZnTe

    International Nuclear Information System (INIS)

    Current and spectrometrical characteristics, stability in time and reliability of pixel and strip detectors depend on initial material properties, crystal processing quality and contacts manufacture technology. The work presents analysis of current-voltage and spectrometrical characteristics for initial CdTe and CdZnTe crystals applied for pixel and strip detectors manufacture. The crystal surface preparation before contacts manufacture comprises a modified technology. The contacts were made by photolithography with the surface protected by photoresist with further windows lift-off and crystal surface metallization in lifted-off windows. Metal pads were made by gold deposition from chloroauric acid. Thermocompression, ultrasonic and pulse wirebonding, as well as traditional contacts glueing method for CdTe and CdZnTe detectors have been tested for contacts wiring. The pulse wirebonding has revealed the best results. Wiring is made of gold wire with a diameter of 30 μm and is good enough for pixel and strip wirebonding, providing rather low labour-intensiveness for their assembly by standard equipment. The possibility of fabrication of pressing contacts to strip and pixel detectors by Zebra elastomeric connectors has been investigated. The pressing contacts have provided qualitative and reliable electrical contact and signal layout from pixels and strips to readout electronics. Developed technologies were applied in the manufacture of the following CdTe and CdZnTe detectors: 4x4 pixels detector with rectangular pixels 0.65x0.65 mm and pitch 0.75 mm; 4x4 pixels ring miltiple-electrode detector with anode diameter 0.32 mm and pitch 0.75 mm; strip detector with 100 μm width strip and 125 μm pitch. The 4x4 pixels CdZnTe detector has provided at optimal temperature energy resolutions of 808 eV and 1.19 keV at energies of 5.9 and 59.6 keV, respectively. Interstrip resistance between two strips with a distance of 25 μm on detector was 2-8 GΩ

  1. Neutron detectors made from chemically vapor deposited semiconductors

    International Nuclear Information System (INIS)

    In this paper, the authors present the results of investigations on the use of semiconductors deposited by chemical vapor deposition (CVD) for the fabrication of neutron detectors. For this purpose, 20 microm thick hydrogenated amorphous silicon (a-Si:H) pin diodes and 100 microm thick polycrystalline diamond resistive detectors were fabricated. The detectors were coupled to a neutron-charged particle converter: a layer of either gadolinium or boron (isotope 10 enriched) deposited by evaporation. They have demonstrated the capability of such neutron detectors to operate at neutron fluxes ranging from 101 to 106 neutrons/cm2.s. The fabrication of large area detectors for neutron counting or cartography through the use of multichannel reading circuits is discussed. The advantages of these detectors include the ability to produce large area detectors at low cost, radiation hardness (∼ 4 Mrad for a-Si:H and ∼ 100 Mrad for diamond), and for diamond, operation at temperatures up to 500 C. These properties enable the use of these devices for neutron detection in harsh environments. Thermal neutron detection efficiency up to 22% and 3% are expected by coupling a-Si:H diodes and diamond detectors to 3 microm thick gadolinium (isotope 157) and 2 microm thick boron layers, respectively

  2. Discrimination between normal breast tissue and tumor tissue using CdTe series detector developed for photon-counting mammography

    Science.gov (United States)

    Okamoto, Chizuru; Ihori, Akiko; Yamakawa, Tsutomu; Yamamoto, Shuichiro; Okada, Masahiro; Kato, Misa; Nakajima, Ai; Kodera, Yoshie

    2016-03-01

    We propose a new mammography system using a cadmium telluride (CdTe) series photon-counting detector, having high absorption efficiency over a wide energy range. In a previous study, we showed that the use of high X-ray energy in digital mammography is useful from the viewpoint of exposure dose and image quality. In addition, the CdTe series detector can acquire X-ray spectrum information following transmission through a subject. This study focused on the tissue composition identified using spectral information obtained by a new photon-counting detector. Normal breast tissue consists entirely of adipose and glandular tissues. However, it is very difficult to find tumor tissue in the region of glandular tissue via a conventional mammogram, especially in dense breast because the attenuation coefficients of glandular tissue and tumor tissue are very close. As a fundamental examination, we considered a simulation phantom and showed the difference between normal breast tissue and tumor tissue of various thicknesses in a three-dimensional (3D) scatter plot. We were able to discriminate between both types of tissues. In addition, there was a tendency for the distribution to depend on the thickness of the tumor tissue. Thinner tumor tissues were shown to be closer in appearance to normal breast tissue. This study also demonstrated that the difference between these tissues could be made obvious by using a CdTe series detector. We believe that this differentiation is important, and therefore, expect this technology to be applied to new tumor detection systems in the future.

  3. On the energy response function of a CdTe Medipix2 Hexa detector

    Energy Technology Data Exchange (ETDEWEB)

    Koenig, Thomas, E-mail: t.koenig@dkfz.de [German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, 69120 Heidelberg (Germany); Zwerger, Andreas [Freiburg Materials Research Center (FMF), Stefan-Meier-Strasse 21, 79104 Freiburg (Germany); Zuber, Marcus; Schuenke, Patrick; Nill, Simeon [German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, 69120 Heidelberg (Germany); Guni, Ewald [Erlangen Centre for Astroparticle Physics (ECAP), Erwin-Rommel-Strasse 1, 91058 Erlangen (Germany); Fauler, Alex; Fiederle, Michael [Freiburg Materials Research Center (FMF), Stefan-Meier-Strasse 21, 79104 Freiburg (Germany); Oelfke, Uwe [German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, 69120 Heidelberg (Germany)

    2011-08-21

    X-ray imaging based on photon counting pixel detectors has received increased interest during the past years. Attached to a semiconductor of choice, some of these devices enable to resolve the spectral components of an image. This work presents the results from measuring the energy response function of a Medipix2 MXR Hexa detector, where six individual Medipix detectors were bump bonded to a 1 mm thick cadmium telluride sensor in order to form a 3x2 array of 4.2x2.8 cm{sup 2} size. The average FWHM of the photo peak of an {sup 241}Am source was found to be 2.2 and 2.1 keV for single pixels and bias voltages of 200 and 350 V, respectively, across the whole Hexa detector. This corresponds to a relative energy resolution of less than 4%. Adding up all pixel spectra of individual chips lead to an only small deterioration of energy resolution, with line widths of 2.7 and 2.5 keV. In general, a lower detection efficiency was observed for the lower voltage setting, along with a shift of the peak position towards lower energies.

  4. Performance of CdTe gamma-ray detectors fabricated in a new M π n design

    Science.gov (United States)

    Niraula, M.; Mochizuki, D.; Aoki, T.; Tomita, Y.; Hatanaka, Y.

    2000-06-01

    CdTe radiation detectors have been fabricated in a new M-π-n structure that provides very effective blocking for the leakage current and, as a result, excellent spectral responses are achieved. An iodine-doped n-CdTe layer was grown on the Te-faces of the (1 1 1)-oriented high-resistivity (˜10 9 Ω cm) ρ-type CdTe wafers at the low substrate temperature of 150°C. An aluminum electrode was evaporated on the n-CdTe side, while a gold electrode was evaporated on the other side. Low leakage current around 60 pA/mm 2 was typically attained for a 0.5 mm thick detector at room-temperature (25°C) for an applied reverse bias of 250 V. Improved charge collection efficiency and spectral responses for different radioisotopes in the energy range of a few tens of keV to several hundreds of keV were obtained due to the application of very large electric fields on the detectors. The performance of the detectors thus fabricated is presented.

  5. Photon detector composed of metal and semiconductor nanoparticles

    International Nuclear Information System (INIS)

    Applying the function of the single electron transistor, a novel photon detector consisting of a self-assembled structure of metal and semiconductor nanoparticles and an organic insulating layer was developed. It showed coulomb blockade behavior under dark conditions and remarkable increase in current corresponding to light intensity under light irradiation. Ultraweak photon emission of about 600 counts per second in the ultraviolet region could be detected at room temperature by this photon counter

  6. Palladium silicide - a new contact for semiconductor radiation detectors

    International Nuclear Information System (INIS)

    Silicide layers can be used as low resistance contacts in semiconductor devices. The formation of a metal rich palladium silicide Pd2Si is discussed. A palladium film 100A thick is deposited at 3000C and the resulting silicide layer used as an ohmic contact in an n + p silicon detector. This rugged contact has electrical characteristics comparable with existing evaporated gold contacts and enables the use of more reproducible bonding techniques. (author)

  7. Present status and future trends of semiconductor detectors

    International Nuclear Information System (INIS)

    Some examples of the applications of semiconductor radiation detectors are briefly outlined, in order to illustrate development trends. The major parameters including energy resolution and dead time are discussed, and their improvement by the application of temporally varying parameter filters is pointed out. Development trends point toward low-loss signal processing by using adaptive filtering, possibly digital filtering. (R.P.) 14 refs.; 3 figs

  8. Use of semiconductor detectors for radioactive waste account and control

    CERN Document Server

    Davydov, L N; Zakharchenko, A A

    2002-01-01

    The possibilities and development status of the contemporary semiconductor detectors and detecting devices intended for radiation monitoring at nuclear industry enterprises, including Chernobyl Shelter and depositories of nuclear wastes are shown. Such devices,created in the last years, can be successfully used for measurements of the gamma-radiation dose rate as well as for the isotope composition evaluation of nuclear materials and wastes, both during the work cycles and in emergency situations.

  9. Semiconductor detectors and double beta decay

    International Nuclear Information System (INIS)

    Theoretical physicists have devoted great effort to developing an adequate theory for linking the weak, electromagnetic, and strong forces of nature. Recent theoretical studies and observations of the stability of galaxies have strongly indicated the presence of large amounts of invisible mass. One element in the uncertainty associated with missing mass is the question of whether the neutrino has rest mass. A better understanding of the neutrino, explored in this paper by the possibility of double beta decay in the germanium 76 isotope, could perhaps provide some answers. Nuclear transitions are only energetically possible where the final nucleus is more tightly bound than its parent. The decay of germanium 76 to arsenic 76 is not energetically possible because the arsenic isotope is about 0.9 MeV less tightly bound than the germanium. The selenium 76 isotope, on the other hand, is about 2 MeV more tightly bound; therefore, a transition involving emission of two electrons by a germanium 76 nucleus to form a selenium 76 nucleus is energetically possible. The total energy release in kinetic energy of the beta particles and corresponding neutrinos from the excited daughter product is determined by the energy difference. This energetically possible event, if observed, will provide a breakthrough in understanding the universe. This paper discusses the underlying theory and a germanium detector experiment which could make such a contribution to the resolution of this question

  10. Determination of the dynamic nonlinearity of semiconductor and combined detectors for computer-assisted tomography

    International Nuclear Information System (INIS)

    The experimental arrangement described reproduces values of the x-ray photon flux density that are typical of computer-assisted tomography (108-1010 cm-2 x sec-1) and its rates of relative change. The authors give the results of determination of the dynamic nonlinearity γ/sup d/ of combined detectors [CsI(Tl) +- Si photodiode and CdWO4 + FEU-60 photomultiplier] and semiconducting CdTe. The CdTe detector has the highest value, γ/sup d/ ≥ 36%, while CdWO4 + FEU-60 has the lowest values, γ/sup d/ ≤ 1%, on the trailing edge of the current signal

  11. Radiation-hard semiconductor detectors for SuperLHC

    CERN Document Server

    Bruzzi, Mara; Al-Ajili, A A; Alexandrov, P; Alfieri, G; Allport, Philip P; Andreazza, A; Artuso, M; Assouak, S; Avset, B S; Barabash, L; Baranova, E; Barcz, A; Basile, A; Bates, R; Belova, N; Betta, G F D; Biagi, S F; Bilei, G M; Bisello, D; Blue, A; Blumenau, A; Boisvert, V; Bölla, G; Bondarenko, G B; Borchi, E; Borrello, L; Bortoletto, D; Boscardin, M; Bosisio, L; Bowcock, T J V; Brodbeck, T J; Broz, J; Brukhanov, A; Brzozowski, A; Buda, M; Buhmann, P; Buttar, C; Campabadal, F; Campbell, D; Candelori, A; Casse, G; Cavallini, A; Chilingarov, A G; Chren, D; Cindro, V; Citterio, M; Collins, P; Coluccia, R; Contarato, D; Coutinho, J; Creanza, D; Cunningham, W; Cvetkov, V; Davies, G; Dawson, I; De Palma, M; Demina, R; Dervan, P; Dierlamm, A; Dittongo, S; Dobrzanski, L; Dolezal, Z; Dolgolenko, A; Eberlein, T; Eremin, V; Fall, C; Fasolo, F; Ferbel, T; Fizzotti, F; Fleta, C; Focardi, E; Forton, E; Franchenko, S; Fretwurst, E; Gamaz, F; García-Navarro, J E; García, C; Gaubas, E; Genest, M H; Gill, K A; Giolo, K; Glaser, M; Gössling, C; Golovine, V; Gorelov, I; Goss, J; Gouldwell, A; Grégoire, G; Gregori, P; Grigoriev, E; Grigson, C; Grillo, A; Groza, A; Guskov, J; Haddad, L; Harding, R; Härkönen, J; Hauler, F; Hayama, S; Hoeferkamp, M; Honniger, F; Horazdovsky, T; Horisberger, R P; Horn, M; Houdayer, A; Hourahine, B; Hruban, A; Hughes, G; Ilyashenko, Yu S; Irmscher, K; Ivanov, A; Jarasiunas, K; Jin, T; Jones, B K; Jones, R; Joram, C; Jungermann, L; Kalinina, E; Kaminski, P; Karpenko, A; Karpov, A; Kazlauskiene, V; Kazukauskas, V; Khivrich, V; Khomenkov, V P; Kierstead, J A; Klaiber Lodewigs, J M; Kleverman, M; Klingenberg, R; Kodys, P; Kohout, Z; Korjenevski, S; Kowalik, A; Kozlowski, R; Kozodaev, M; Kramberger, G; Krasel, O; Kuznetsov, A; Kwan, S; Lagomarsino, S; Lari, T; Lassila-Perini, K M; Lastovetsky, V F; Latino, G; Latushkin, S T; Lazanu, I; Lazanu, S; Lebel, C; Leinonen, K; Leroy, C; Li, Z; Lindström, G; Lindström, L; Linhart, V; Litovchenko, A P; Litovchenko, P G; Litvinov, V; Lo Giudice, A; Lozano, M; Luczynski, Z; Luukka, Panja; Macchiolo, A; Mainwood, A; Makarenko, L F; Mandic, I; Manfredotti, C; Martí i García, S; Marunko, S; Mathieson, K; Melone, J; Menichelli, D; Meroni, C; Messineo, A; Miglio, S; Mikuz, M; Miyamoto, J; Moll, M; Monakhov, E; Moscatelli, F; Mozzanti, A; Murin, L; Naoumov, D; Nava, F; Nossarzhevska, E; Nummela, S; Nysten, J; Olivero, P; O'Shea, V; Palviainen, T; Paolini, C; Parkes, C; Passeri, D; Pein, U; Pellegrini, G; Perera, L; Petasecca, M; Piatkowski, B; Piemonte, C; Pignatel, G U; Pinho, N; Pintilie, I; Pintilie, L; Polivtsev, L; Polozov, P; Popa, A I; Popule, J; Pospísil, S; Pucker, G; Radicci, V; Rafí, J M; Ragusa, F; Rahman, M; Rando, R; Röder, R; Rohe, T; Ronchin, S; Rott, C; Roy, A; Roy, P; Ruzin, A; Ryazanov, A; Sadrozinski, H F W; Sakalauskas, S; Scaringella, M; Schiavulli, L; Schnetzer, S; Schumm, B; Sciortino, S; Scorzoni, A; Segneri, G; Seidel, S; Seiden, A; Sellberg, G; Sellin, P J; Sentenac, D; Sevilla, S G; Shipsey, I; Sícho, P; Sloan, T; Solar, M; Son, S; Sopko, B; Spencer, N; Stahl, J; Stavitski, I; Stolze, D; Stone, R; Storasta, J; Strokan, N; Strupinski, W; Sudzius, M; Surma, B; Suuronen, J; Suvorov, A; Svensson, B G; Tipton, P; Tomasek, M; Troncon, C; Tsvetkov, A; Tuominen, E; Tuovinen, E; Tuuva, T; Tylchin, M; Uebersee, H; Uher, J; Ullán, M; Vaitkus, J V; Vanni, P; Velthuis, J; Verbitskaya, E; Verzellesi, G; Vrba, V; Wagner, G; Wilhelm, I; Worm, S; Wright, V; Wunstorf, R; Zabierowski, P; Zaluzhny, A; Zavrtanik, M; Zen, M; Zhukov, V; Zorzi, N; de Boer, Wim

    2005-01-01

    An option of increasing the luminosity of the Large Hadron Collider (LHC) at CERN to 10/sup 35/ cm-/sup 2/s-/sup 1/ has been envisaged to extend the physics reach of the machine. An efficient tracking down to a few centimetres from the interaction point will be required to exploit the physics potential of the upgraded LHC. As a consequence, the semiconductor detectors close to the interaction region will receive severe doses of fast hadron irradiation and the inner tracker detectors will need to survive fast hadron fluences of up to above 10 /sup 16/ cm-/sup 2/. The CERN-RD50 project "Development of Radiation Hard Semiconductor Devices for Very High Luminosity Colliders" has been established in 2002 to explore detector materials and technologies that will allow to operate devices up to, or beyond, this limit. The strategies followed by RD50 to enhance the radiation tolerance include the development of new or defect engineered detector materials (SiC, GaN, Czochralski and epitaxial silicon, oxygen enriched Flo...

  12. Simulation of charge transport in pixelated CdTe

    OpenAIRE

    Kolstein, M.; Ariño, G.; Chmeissani, M.; De Lorenzo, G.

    2014-01-01

    The Voxel Imaging PET (VIP) Pathfinder project intends to show the advantages of using pixelated semiconductor technology for nuclear medicine applications to achieve an improved image reconstruction without efficiency loss. It proposes designs for Positron Emission Tomography (PET), Positron Emission Mammography (PEM) and Compton gamma camera detectors with a large number of signal channels (of the order of 106). The design is based on the use of a pixelated CdTe Schottky detector to have op...

  13. Charge collection properties of a CdTe Schottky diode for x- and γ-rays detectors

    International Nuclear Information System (INIS)

    The electrical characteristics of x-ray and γ-ray detectors with Schottky diodes on the basis of CdTe crystals of n-type conductivity with a resistivity of 102–103 Ω cm (300 K) are investigated. The necessary parameters of the diode structures are determined to interpret the detection characteristics of the detectors. The dependences of the charge-collection efficiency in the detectors on the carrier lifetime and concentration of uncompensated donors are obtained and the conditions for the total collection of charges generated by the photon absorption are established. Taking into account drift and diffusion photocurrent components, the spectral distribution of the quantum detection efficiency is calculated. The comparative analysis of the detection efficiency of Schottky diodes based on low-resistivity p-CdTe and n-CdTe shows the advantages of the latter, especially in a low x-ray energy region

  14. Electric Field and Current Transport Mechanisms in Schottky CdTe X-ray Detectors under Perturbing Optical Radiation

    Directory of Open Access Journals (Sweden)

    Isabella Farella

    2013-07-01

    Full Text Available Schottky CdTe X-ray detectors exhibit excellent spectroscopic performance but suffer from instabilities. Hence it is of extreme relevance to investigate their electrical properties. A systematic study of the electric field distribution and the current flowing in such detectors under optical perturbations is presented here. The detector response is explored by varying experimental parameters, such as voltage, temperature, and radiation wavelength. The strongest perturbation is observed under 850 nm irradiation, bulk carrier recombination becoming effective there. Cathode and anode irradiations evidence the crucial role of the contacts, the cathode being Ohmic and the anode blocking. In particular, under irradiation of the cathode, charge injection occurs and peculiar kinks, typical of trap filling, are observed both in the current-voltage characteristic and during transients. The simultaneous access to the electric field and the current highlights the correlation between free and fixed charges, and unveils carrier transport/collection mechanisms otherwise hidden.

  15. Possible use of CdTe detectors in kVp monitoring of diagnostic x-ray tubes

    OpenAIRE

    Krmar, M.; Bucalović, N.; Baucal, M.; Jovančević, N.

    2010-01-01

    It has been suggested that kVp of diagnostic X-ray devices (or maximal energy of x-ray photon spectra) should be monitored routinely; however a standardized noninvasive technique has yet to be developed and proposed. It is well known that the integral number of Compton scattered photons and the intensities of fluorescent x-ray lines registered after irradiation of some material by an x-ray beam are a function of the maximal beam energy. CdTe detectors have sufficient energy resolution to dist...

  16. Energy Calibration of a CdTe Photon Counting Spectral Detector with Consideration of its Non-Convergent Behavior

    OpenAIRE

    Jeong Seok Lee; Dong-Goo Kang; Seung Oh Jin; Insoo Kim; Soo Yeol Lee

    2016-01-01

    Fast and accurate energy calibration of photon counting spectral detectors (PCSDs) is essential for their biomedical applications to identify and characterize bio-components or contrast agents in tissues. Using the x-ray tube voltage as a reference for energy calibration is known to be an efficient method, but there has been no consideration in the energy calibration of non-convergent behavior of PCSDs. We observed that a single pixel mode (SPM) CdTe PCSD based on Medipix-2 shows some non-con...

  17. Voxel imaging pet pathfinder: a novel approach to positron emission tomography based on room temperature pixelated CdTe detector

    OpenAIRE

    Mikhaylova, Ekaterina

    2014-01-01

    El objetivo principal de esta investigación es la simulación y la evaluación de un nuevo concepto de escáner de tomografía por emisión de positrones (PET) basado en un detector pixelado de CdTe en el marco del proyecto “Voxel Imaging PET (VIP) Pathfinder”. El diseño se ha simulado con el programa “GEANT4-based Architecture for Medicine-Oriented Simulations” (GAMOS). El sistema se ha examinado siguiendo las prescripciones de los protocolos NEMA para la evaluación de los dispositivos PET. Varia...

  18. Voxel imaging pet pathfinder: a novel approach to positron emission tomography based on room temperature pixelated CdTe detector

    OpenAIRE

    Mikhaylova, Ekaterina; Fernandez Sanchez, Enrique

    2014-01-01

    El objetivo principal de esta investigación es la simulación y la evaluación de un nuevo concepto de escáner de tomografía por emisión de positrones (PET) basado en un detector pixelado de CdTe en el marco del proyecto "Voxel Imaging PET (VIP) Pathfinder". El diseño se ha simulado con el programa "GEANT4-based Architecture for Medicine-Oriented Simulations" (GAMOS). El sistema se ha examinado siguiendo las prescripciones de los protocolos NEMA para la evaluación de los dispositivos PET. Varia...

  19. A 2D 4×4 Channel Readout ASIC for Pixelated CdTe Detectors for Medical Imaging Applications

    OpenAIRE

    Macias-Montero, Jose-Gabriel; Sarraj, Maher; Chmeissani, Mokhtar; Martínez, Ricardo; Puigdengoles, Carles

    2015-01-01

    We present a 16-channel readout integrated circuit (ROIC) with nanosecond-resolution time to digital converter (TDC) for pixelated Cadmium Telluride (CdTe) gamma-ray detectors. The 4 × 4 pixel array ROIC is the proof of concept of the 10 × 10 pixel array readout ASIC for positron-emission tomography (PET) scanner, positron-emission mammography (PEM) scanner, and Compton gamma camera. The electronics of each individual pixel integrates an analog front-end with switchable gain, an analog to dig...

  20. Semiconductor Pixel detectors and their applications in life sciences

    International Nuclear Information System (INIS)

    Recent advances in semiconductor technology allow construction of highly efficient and low noise pixel detectors of ionizing radiation. Steadily improving quality of front end electronics enables fast digital signal processing in each pixel which offers recording of more complete information about each detected quantum (energy, time, number of particles). All these features improve an extend applicability of pixel technology in different fields. Some applications of this technology especially for imaging in life sciences will be shown (energy and phase sensitive X-ray radiography and tomography, radiography with heavy charged particles, neutron radiography, etc). On the other hand a number of obstacles can limit the detector performance if not handled. The pixel detector is in fact an array of individual detectors (pixels), each of them has its own efficiency, energy calibration and also noise. The common effort is to make all these parameters uniform for all pixels. However an ideal uniformity can be never reached. Moreover, it is often seen that the signal in one pixel can affect the neighbouring pixels due to various reasons (e.g. charge sharing). All such effects have to be taken into account during data processing to avoid false data interpretation. A brief view into the future of pixel detectors and their applications including also spectroscopy, tracking and dosimetry is given too. Special attention is paid to the problem of detector segmentation in context of the charge sharing effect.

  1. A semiconductor parameter analyzer for ionizing radiation detectors

    International Nuclear Information System (INIS)

    Electrometers and ion chamber are normally used to make several types of measurements in a radiation field and there is a unique voltage applied to each detector type. Some electronic devices that are built of semiconductor materials like silicon crystal can also be used for the same purpose. In this case, a characteristic curve of the device must be acquired to choose an operation point which consists of an electrical current or voltage to be applied to the device. Unlike ion chambers, such an electronic device can have different operation points depending on its current versus voltage curve (I x V). The best operation point of the device is also a function of the radiation, energy, dose rate and fluence. The purpose of this work is to show a semiconductor parameter analyzer built to acquire I x V curves as usually, and the innovation here is the fact that it can be used to obtain such a parametric curve when a quad-polar device is under irradiation. The results demonstrate that the system is a very important tool to scientists interested to evaluate a semiconductor detector before, during and after irradiation. A collection of results for devices under an X-ray beam and a neutron fluence are presented: photodiode, phototransistors, bipolar transistor and MOSFET. (author)

  2. Carrier Density and Compensation in Semiconductors with Multi Dopants and Multi Transition Energy Levels: The Case of Cu Impurity in CdTe: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Wei, S. H.; Ma, J.; Gessert, T. A.; Chin, K. K.

    2011-07-01

    Doping is one of the most important issues in semiconductor physics. The charge carrier generated by doping can profoundly change the properties of semiconductors and their performance in optoelectronic device applications, such as solar cells. Using detailed balance theory and first-principles calculated defect formation energies and transition energy levels, we derive general formulae to calculate carrier density for semiconductors with multi dopants and multi transition energy levels. As an example, we studied CdTe doped with Cu, in which VCd, CuCd, and Cui are the dominant defects/impurities. We show that in this system, when Cu concentration increases, the doping properties of the system can change from a poor p-type, to a poorer p-type, to a better p-type, and then to a poor p-type again, in good agreement with experimental observation of CdTe-based solar cells.

  3. Testing in a stratospheric balloon of a semiconductor detector altimeter

    International Nuclear Information System (INIS)

    An altimeter containing a semiconductor detector has been operated on flight. We have used a stratospheric balloon launched from AIRE-SUR-ADOUR with the C.N.E.S. collaboration. During this assay two apparatus have been used. The first allowed to follow the balloon during its ascension and descent, the second to follow its evolution at its maximum altitude. Informations transmitted by radio and recorded on Magnetophon, have been studied after the flight. Results are identical with these given by the barometer used by the C.N.E.S. in this essay. (authors)

  4. Semiconductor micropattern pixel detectors a review of the beginnings

    CERN Document Server

    Heijne, Erik H M

    2001-01-01

    The innovation in monolithic and hybrid semiconductor 'micropattern' or 'reactive' pixel detectors for tracking in particle physics was actually to fit logic and pulse processing electronics with µW power on a pixel area of less than 0.04 mm2, retaining the characteristics of a traditional nuclear amplifier chain. The ns timing precision in conjunction with local memory and logic operations allowed event selection at > 10 MHz rates with unambiguous track reconstruction even at particle multiplicities > 10 cm-2. The noise in a channel was ~100 e- r.m.s. and enabled binary operation with random noise 'hits' at a level 30 Mrad, respectively.

  5. Study of unfolding methods for X-ray spectra obtained with CDTE detectors in the mammography energy range

    International Nuclear Information System (INIS)

    Quality control parameters for an X-ray tube strongly depend on the accurate knowledge of the primary spectrum, but it is difficult to obtain it experimentally by direct measurements. Indirect spectrometry techniques such as Compton scattering can be used in X-ray spectrum assessment avoiding the pile-up effect in detectors. However, an unfolding method is required for this kind of measurements. In previous works, a methodology to assess primary X-ray spectra in the diagnostic energy range by means of the Compton scattering technique has been analysed. This methodology included a Monte Carlo simulation model, using the MCNP5 code, of the actual experimental set-up providing a Pulse Height Distribution (PHD) for a given primary spectrum. It reproduced the interaction of photons and electrons with the Compton spectrometer and with a High Purity Germanium detector. In this work, a CdTe detector is proposed instead of the HP Germanium. CdTe detector does not require a liquid nitrogen cooling system, but its resolution is poor for the same energy range and its efficiency comes down for energies greater than 55 keV being 70% at 90 keV. In despite of these disadvantages, CdTe detector has been considered due to its low cost and easy handling and portability. The model can provide a PHD and a Response Matrix, for different X-ray spectra, taken from the IPEM 78 catalogue. The primary spectrum can be estimated applying the MTSVD (Modified Truncated Singular Value Decomposition) and the Tikhonov unfolding method. Both unfolding methods cause some loss of information on the reconstructed primary spectra. In this paper, a comparison of the ability to obtain primary spectra using both MTSVD and Tikhonov unfolding methods has been done. As well a sensitivity analysis in order to test the proposed unfolding methods when they are applied to PHDs obtained with the MCNP model has been developed. A variation on parameters such as target materials and voltages over the mammography

  6. Signal formation and decay in CdTe x-ray detectors under intense irradiation.

    Science.gov (United States)

    Jahnke, A; Matz, R

    1999-01-01

    The response of Cd(Zn)Te Schottky and resistive detectors to intense x-rays is investigated in a commercial computed tomography (CT) system to assess their potential for medical diagnostics. To describe their signal height, responsivity, signal-to-noise ratio (SNR), and detective quantum efficiency the devices are modeled as solid-state ionization chambers with spatially varying electric field and charge collection efficiency. The thicknesses and pixel areas of the discrete detector elements are 0.5-2 mm and a few mm2, respectively. The incident spectrum extends from 26 to 120 keV and comprises 10(10) quanta/s cm2. It photogenerates a carrier concentration in the semiconductor that is two to three orders of magnitude above the intrinsic concentration, but remains to a similar extent below the charge densities on the device electrodes. Stable linear operation is achieved with the Schottky-type devices under high bias. Their behavior can be modeled well if negatively charged near-midgap bulk defects with a concentration of 10(11)-10(13) cm-3 are assumed. The bulk defects explain the amount and time constant (about 100 ms) of the detrapping current measured after x-ray pulses (afterglow). To avoid screening by the trapped space charge the bias voltage should exceed 100(V) x [detector thickness/mm]2. Dark currents are of the order of the generation-recombination current, i.e., 300 pA/mm3 detector volume. With proper device design the signal height approaches the theoretical maximum of 0.2 A/W. This high responsivity, however, is not exploited in CT since the SNR is determined here by the incident quantum noise. As a consequence of the detrapping current, the response speed does not meet CT requirements. A medium-term effort for crystal growth appears necessary to achieve the required reduction of the trap density by an order of magnitude. Scintillation based detectors are, therefore, still preferred in fast operating medical diagnostic systems. PMID:9949396

  7. Edge effects in a small pixel CdTe for X-ray imaging

    OpenAIRE

    Duarte, DD; Bell, SJ; Lipp, J; Schneider, A.; Seller, P; Veale, MC; Wilson, MD; Baker, MA; Sellin, PJ; Kachkanov, V.; Sawhney, KJS

    2013-01-01

    Large area detectors capable of operating with high detection efficiency at energies above 30 keV are required in many contemporary X-ray imaging applications. The properties of high Z compound semiconductors, such as CdTe, make them ideally suitable to these applications. The STFC Rutherford Appleton Laboratory has developed a small pixel CdTe detector with 80×80 pixels on a 250 µm pitch. Historically, these detectors have included a 200 µm wide guard band around the pixelated anode to reduc...

  8. Concentration of uncompensated impurities as a key parameter of CdTe and CdZnTe crystals for Schottky diode x/γ-ray detectors

    International Nuclear Information System (INIS)

    In this paper we report on the strong impact of the concentration of uncompensated impurities on the detection efficiency of CdTe and Cd0.9Zn0.1Te Schottky diodes. The results of our study explain the observed poor detection properties of some Cd0.9Zn0.1Te detectors with resistivity and lifetime of carriers comparable to those of good CdTe detectors. We show that the concentration of uncompensated impurities in a highly efficient CdTe Schottky diode detector is several orders of magnitude higher than that of a CdZnTe, which does not register the gamma spectra of commonly used isotopes (59–662 keV) by using photoelectric measurements. The significant difference of the concentration of uncompensated impurities between CdTe and Cd0.9Zn0.1Te crystals is confirmed by our study of the temperature change of the resistivity and of the Fermi level energy. The degree of compensation of the donor complex, responsible for the electrical conductivity of the material, is much lower in the CdTe crystal compared to that in the Cd0.9Zn0.1Te crystal. The calculations of the detection efficiency of x/γ-radiation by a Schottky diode result in a dependence on the concentration of uncompensated impurities described by a curve with a pronounced maximum. The position of this maximum occurs at a concentration of uncompensated impurities which ranges from 3 × 1010 to 3 × 1012 cm−3 depending on the registered photon energy of x/γ-rays and on the lifetime of the charge carriers. Our measurements and calculations lead to the conclusion that the concentration of uncompensated impurities in this range is a necessary condition for the effective operation of x- and γ-ray Schottky diode detectors based on CdTe and Cd1−xZnxTe crystals

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

    Energy Technology Data Exchange (ETDEWEB)

    Zumbiehl, A. E-mail: zumbiehl@phase.c-strasbourg.fr; Hage-Ali, M.; Fougeres, P.; Koebel, J.M.; Regal, R.; Rit, C.; Ayoub, M.; Siffert, P

    2001-08-11

    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: after showing our approach for the weighting potential calculation, we present our results performed by a 'pseudo-Monte Carlo' simulation. Results are supported by a few experimental comparisons. We argue about the optimum sizes with clarifying the problems caused by too small and too large pixel sizes. The study field is chosen to be vast, i.e. pixel size to detector thickness ratios (W/L) of 1/8-1, and detector thickness of 1.0-8.0 mm. In addition, several electrical transport properties are used. Since efficiency is often of primary interest, thick detectors could be very attractive, which are shown to be really feasible even on CdTe.

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

    Science.gov (United States)

    Zumbiehl, A.; Hage-Ali, M.; Fougeres, P.; Koebel, J. M.; Regal, R.; Rit, C.; Ayoub, M.; Siffert, P.

    2001-08-01

    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: after showing our approach for the weighting potential calculation, we present our results performed by a "pseudo-Monte Carlo" simulation. Results are supported by a few experimental comparisons. We argue about the optimum sizes with clarifying the problems caused by too small and too large pixel sizes. The study field is chosen to be vast, i.e. pixel size to detector thickness ratios ( W/ L) of 1/8-1, and detector thickness of 1.0-8.0 mm. In addition, several electrical transport properties are used. Since efficiency is often of primary interest, thick detectors could be very attractive, which are shown to be really feasible even on CdTe.

  11. p-i-n CdTe multi-pixel detector for gamma-ray imaging fabricated by excimer laser processing

    International Nuclear Information System (INIS)

    A multi-pixel gamma-ray imaging detector unit, which has a high-energy resolution with room temperature operation, was fabricated using the diode-type CdTe detector. The diode structure was prepared by indium-doped n-type CdTe thin layer formed by excimer laser doping on one-side of high resistivity p-like single crystal CdTe wafer, and a gold electrode as a Shottkey electrode evaporated on the opposite side of the wafer. This diode-detectors showed good diode I-V characteristics with low leakage current. This CdTe detectors were pixelized in the 2mm x 2mm, and the 128 chips (32x4 chips) were mounted on the ceramic printed circuit boards at 3 mm interval with 1 mm gap. The printed circuit boards are directly connected the MCSA-EXI ASIC chip and 128 ch radiation spectrum analyzer systems. When using the Am-241 and the Co-57 as radioisotopes, the spectral response from all the pixels within 4,4 ke V of FWHM at 122 ke V peak of Co-57 for radiation performed at room temperature. The intensities of the peak from pixels were also uniform (Authors)

  12. Energy resolution in semiconductor gamma radiation detectors using heterojunctions and methods of use and preparation thereof

    Science.gov (United States)

    Nikolic, Rebecca J.; Conway, Adam M.; Nelson, Art J.; Payne, Stephen A.

    2012-09-04

    In one embodiment, a system comprises a semiconductor gamma detector material and a hole blocking layer adjacent the gamma detector material, the hole blocking layer resisting passage of holes therethrough. In another embodiment, a system comprises a semiconductor gamma detector material, and an electron blocking layer adjacent the gamma detector material, the electron blocking layer resisting passage of electrons therethrough, wherein the electron blocking layer comprises undoped HgCdTe. In another embodiment, a method comprises forming a hole blocking layer adjacent a semiconductor gamma detector material, the hole blocking layer resisting passage of holes therethrough. Additional systems and methods are also presented.

  13. 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.

  14. Performance of a 6 mm thick CdTe detector for 166 keV gamma rays

    Science.gov (United States)

    McKee, B. T. A.; Goetz, T.; Hazlett, T.; Forkert, L.

    1988-11-01

    In order to extend the utility of CdTe detectors to higher gamma ray energies, yet avoid increasing the charge collection problems of thick detectors, a 6 mm thick detector configuration has been developed consisting of three crystals 2 mm thick and of 16 mm diameter. The active volume is over 1.0 cm 3. The performance of this detector has been evaluated for gamma rays of 166 keV energy by measuring the pulse height spectra and determining the intrinsic peak and total efficiencies over a range of bias voltages and amplifier time constants. A maximum peak and total efficiency of 41% and 80% were obtained with 200 V bias and 2 μs amplifier time constant, although under these conditions the noise width was almost 40 keV FWHM. A Monte Carlo model was used to simulate the gamma ray and electron interaction in this 6 mm detector. Charge collection, including trapping effects, was incorporated into the model. The model pulse height spectra could be approximately matched to the measured data using hole and electron effective mobility values of 60 and 600 cm 2/V s, and hole and electron mean trapping times of 25 and 15 μs. Our findings indicate that detectors such as this will not be useful for high resolution spectroscopic applications, but the high gamma ray stopping power will be of interest for applications where the noise width is acceptable. Results from the modelling imply that in this detector shallow trapping sites (reducing the effective mobility) are more important than deep trapping sites in contributing to incomplete charge collection.

  15. Performance of a 6 mm thick CdTe detector for 166 keV gamma rays

    Energy Technology Data Exchange (ETDEWEB)

    McKee, B.T.A.; Goetz, T.; Hazlett, T.; Forkert, L.

    1988-11-01

    In order to extend the utility of CdTe detectors to higher gamma ray energies, yet avoid increasing the charge collection problems of thick detectors, a 6 mm thick detector configuration has been developed consisting of three crystals 2 mm thick and of 16 mm diameter. The active volume is over 1.0 cm/sup 3/. The performance of this detector has been evaluated for gamma rays of 166 keV energy by measuring the pulse height spectra and determining the intrinsic peak and total efficiencies over a range of bias voltages and amplifier time constants. A maximum peak and total efficiency of 41% and 80% were obtained with 200 V bias and 2 ..mu..s amplifier time constant, although under these conditions the noise width was almost 40 keV FWHM. A Monte Carlo model was used to simulate the gamma ray and electron interaction in this 6 mm detector. Charge collection, including trapping effects, was incorporated into the model. The model pulse height spectra could be approximately matched to the measured data using hole and electron effective mobility values of 60 and 600 cm/sup 2//V s, and hole and electron mean trapping times of 25 and 15 ..mu..s. Our findings indicate that detectors such as this will not be useful for high resolution spectroscopic applications, but the high gamma ray stopping power will be of interest for applications where the noise width is acceptable. Results from the modelling imply that in this detector shallow trapping sites (reducing the effective mobility) are more important than deep trapping sites in contributing to incomplete charge collection.

  16. Technique of absolute efficiency determination for gamma radiation semiconductor detectors

    International Nuclear Information System (INIS)

    Simple technique is suggested to determine the absolute efficiency (E) of semiconductor detectors (SCD) which employes low-intensity neutron sources wide spread in scientific laboratories. The technique is based on using radioactive nuclide gamma radiation in decay chains of heavy element fission fragments, uranium-235, for example. Cumulative yields of a number of nulcides following heavy element fission are measured to a high accuracy (1-5%), which permits to . the value E is determined for a wide energy range (from X- ray to some MeV); using a nuclide with a well known decay scheme and measured to a high accuracy cumulative yield 140La, for example, one can calibrate in absolute values comparatively easily obtained plots of the SCD relative efficiency. The technique allows to determine the E value for extended plane (and volumetric) sources of an arbitrary form. Some nuclides, convenient for the determination of E, and their nuclear characteristics are tabulated

  17. Experimental study of the response of semiconductor detectors to low-energy photons

    CERN Document Server

    Lepy, M C; Laborie, J M; Plagnard, J; Stemmler, P; Teesdale, W J

    2000-01-01

    Six semiconductor detectors (Si(Li) and HPGe) are calibrated in the 1-10 keV energy range by means of tuneable monochromatised synchrotron radiation. Significant improvement in the quality of the response is observed in very recent detectors. A peak shape calibration is established using a modified Hypermet-type function to model the detector response for each energy step; electron effects induce individual background and tail shapes for each detector material. Fano factors for both semiconductor materials are experimentally derived. The efficiency calibration is determined using a proportional counter as reference: the front semiconductor layer acts as a partially active zone.

  18. Energy Calibration of a CdTe Photon Counting Spectral Detector with Consideration of its Non-Convergent Behavior

    Science.gov (United States)

    Lee, Jeong Seok; Kang, Dong-Goo; Jin, Seung Oh; Kim, Insoo; Lee, Soo Yeol

    2016-01-01

    Fast and accurate energy calibration of photon counting spectral detectors (PCSDs) is essential for their biomedical applications to identify and characterize bio-components or contrast agents in tissues. Using the x-ray tube voltage as a reference for energy calibration is known to be an efficient method, but there has been no consideration in the energy calibration of non-convergent behavior of PCSDs. We observed that a single pixel mode (SPM) CdTe PCSD based on Medipix-2 shows some non-convergent behaviors in turning off the detector elements when a high enough threshold is applied to the comparator that produces a binary photon count pulse. More specifically, the detector elements are supposed to stop producing photon count pulses once the threshold reaches a point of the highest photon energy determined by the tube voltage. However, as the x-ray exposure time increases, the threshold giving 50% of off pixels also increases without converging to a point. We established a method to take account of the non-convergent behavior in the energy calibration. With the threshold-to-photon energy mapping function established by the proposed method, we could better identify iodine component in a phantom consisting of iodine and other components. PMID:27077856

  19. Energy Calibration of a CdTe Photon Counting Spectral Detector with Consideration of its Non-Convergent Behavior

    Directory of Open Access Journals (Sweden)

    Jeong Seok Lee

    2016-04-01

    Full Text Available Fast and accurate energy calibration of photon counting spectral detectors (PCSDs is essential for their biomedical applications to identify and characterize bio-components or contrast agents in tissues. Using the x-ray tube voltage as a reference for energy calibration is known to be an efficient method, but there has been no consideration in the energy calibration of non-convergent behavior of PCSDs. We observed that a single pixel mode (SPM CdTe PCSD based on Medipix-2 shows some non-convergent behaviors in turning off the detector elements when a high enough threshold is applied to the comparator that produces a binary photon count pulse. More specifically, the detector elements are supposed to stop producing photon count pulses once the threshold reaches a point of the highest photon energy determined by the tube voltage. However, as the x-ray exposure time increases, the threshold giving 50% of off pixels also increases without converging to a point. We established a method to take account of the non-convergent behavior in the energy calibration. With the threshold-to-photon energy mapping function established by the proposed method, we could better identify iodine component in a phantom consisting of iodine and other components.

  20. CdZnTe and CdTe materials for X-ray and gamma ray radiation detector applications

    International Nuclear Information System (INIS)

    Good detection efficiency and high energy-resolution make Cadmium Zinc Telluride (CdZnTe) and Cadmium Telluride (CdTe) detectors attractive in many room temperature X-ray and gamma-ray detection applications such as medical and industrial imaging, industrial gauging and non-destructive testing, security and monitoring, nuclear safeguards and non-proliferation, and astrophysics. Advancement of the crystal growth and device fabrication technologies and the reduction of bulk, interface and surface defects in the devices are crucial for the widespread practical deployment of Cd1-xZnxTe-based detector technology. Here we review the effects of bulk, interface and surface defects on charge transport, charge transport uniformity and device performance and the progress in the crystal growth and device fabrication technologies aiming at reducing the concentration of harmful defects and improving Cd1-xZnxTe detector performance. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  1. Energy Calibration of a CdTe Photon Counting Spectral Detector with Consideration of its Non-Convergent Behavior.

    Science.gov (United States)

    Lee, Jeong Seok; Kang, Dong-Goo; Jin, Seung Oh; Kim, Insoo; Lee, Soo Yeol

    2016-01-01

    Fast and accurate energy calibration of photon counting spectral detectors (PCSDs) is essential for their biomedical applications to identify and characterize bio-components or contrast agents in tissues. Using the x-ray tube voltage as a reference for energy calibration is known to be an efficient method, but there has been no consideration in the energy calibration of non-convergent behavior of PCSDs. We observed that a single pixel mode (SPM) CdTe PCSD based on Medipix-2 shows some non-convergent behaviors in turning off the detector elements when a high enough threshold is applied to the comparator that produces a binary photon count pulse. More specifically, the detector elements are supposed to stop producing photon count pulses once the threshold reaches a point of the highest photon energy determined by the tube voltage. However, as the x-ray exposure time increases, the threshold giving 50% of off pixels also increases without converging to a point. We established a method to take account of the non-convergent behavior in the energy calibration. With the threshold-to-photon energy mapping function established by the proposed method, we could better identify iodine component in a phantom consisting of iodine and other components. PMID:27077856

  2. Detector modules for the endcaps of the ATLAS semiconductor tracker

    CERN Document Server

    Moorhead, G F

    2002-01-01

    The endcaps of the ATLAS Semiconductor Tracker will be composed of about 2000 detector modules of three different layouts. Up to four single-sided sensors are glued back-to-back with a small stereo angle to form double-sided modules. Five different wedge shaped sensor designs are needed, with a strip pitch varying in the range from 55 to 95 mu m. The sensors are read out by a copper/Kapton multilayer hybrid which carries 12 binary read-out ASICs and all components for the optical transmission of commands and data. Within the tight constraints imposed by the need for radiation hardness, high rate capability, low mass, low cost and overlap between neighbouring modules for detector hermiticity the design has been optimised for a thermal split between the read-out chips and the silicon sensors. The performance of prototype modules stand-alone, in multi-module system tests and in the testbeam will be shown. (9 refs).

  3. Development and characterization of the lead iodide semiconductor detector

    International Nuclear Information System (INIS)

    A methodology for purification and growth of PbI2 crystal as well as for its characterization as a room temperature radiation detector was developed in this work. Commercial salts were purified using the zone refining method and, for the purified material growth, the Bridgman method was used. To calculate the purification efficiency, studies of the decrease impurities concentrations were made in the salts and in three sections of the materials purified, using the neutron activation analysis technique. The results showed that the impurities segregate preferentially in the ingot final section. A significant decrease of the impurities concentration in function of the purification pass number was observed. The grown crystals presented good crystalline quality according to the results of the X-ray diffraction analysis. To evaluate the crystal as a semiconductor detector, measurements of dark leakage current, resistivity and the response of (241Am) alpha particle and (241Am, 57Co, 133Ba and 137Cs) gamma rays were carried out. The radiation response is strongly dependent on the crystals purity. The crystals purified with 500 passes exhibited energy resolution of 10% for 241 Am alpha particle and the gamma rays resolution was compatible with the literature. The photosensibility of the PbI2 crystal found in the wavelength from 400 to 600 nm range suggests an another application at this crystal as a photodetector to be coupled to scintillators. (author)

  4. Study of the spectrometric performances of monolithic CdZnTe / CdTe gamma ray detectors

    International Nuclear Information System (INIS)

    Pixelated monolithic CdTe/CdZnTe semiconductor gamma ray detectors are brought to replace scintillation detectors for medical applications, notably for single photon emission computed tomography (SPECT). In addition to compactness, they present better spectrometric performances: energy resolution, detection efficiency, and spatial resolution. Moreover, the photons depth of interaction in the crystal can be measured. This work aimed in studying experimentally and by simulation the correlations between anodes pitch, material physic properties (resistivity and electron transport properties), and detectors spectrometric performances. We have compared several methods of measuring the photon interaction depth, and have obtained an energy resolution ranging from 1.7% to 7% at 122 keV, according to material, for 5 mm thick detectors. Charge sharing between adjacent anodes has been studied and a measured data processing is proposed. (author)

  5. 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

  6. Extensive testing of Schottky CdTe detectors for the ECLAIRs X-Gamma-ray Camera on board the SVOM mission

    OpenAIRE

    Nadege, Remoue; Didier, Barret; Olivier, Godet; Pierre, Mandrou

    2010-01-01

    We report on an on-going test campaign of more than 5000 Schottky CdTe detectors (4x4x1 mm^3), over a sample of twelve thousands, provided by Acrorad Co., Ltd (Japan). 6400 of these detectors will be used to build the detection plane of the ECLAIRs camera on the Chinese-French gamma-ray burst mission SVOM. These tests are mandatory to fulfill the prime requirement of ECLAIRs to detect gamma-ray burst photons down to 4 keV. The detectors will be operated at -20C under a reverse bias of 600 V. ...

  7. Characterization of high-resistivity CdTe and Cd0.9Zn0.1Te crystals grown by Bridgman method for radiation detector applications

    Science.gov (United States)

    Mandal, Krishna C.; Krishna, Ramesh M.; Pak, Rahmi O.; Mannan, Mohammad A.

    2014-09-01

    CdTe and Cd0.9Zn0.1Te (CZT) crystals have been studied extensively for various applications including x- and γ-ray imaging and high energy radiation detectors. The crystals were grown from zone refined ultra-pure precursor materials using a vertical Bridgman furnace. The growth process has been monitored, controlled, and optimized by a computer simulation and modeling program developed in our laboratory. The grown crystals were thoroughly characterized after cutting wafers from the ingots and processed by chemo-mechanical polishing (CMP). The infrared (IR) transmission images of the post-treated CdTe and CZT crystals showed average Te inclusion size of ~10 μm for CdTe and ~8 μm for CZT crystal. The etch pit density was ≤ 5×104 cm-2 for CdTe and ≤ 3×104 cm-2 for CZT. Various planar and Frisch collar detectors were fabricated and evaluated. From the current-voltage measurements, the electrical resistivity was estimated to be ~ 1.5×1010 Ω-cm for CdTe and 2-5×1011 Ω-cm for CZT. The Hecht analysis of electron and hole mobility-lifetime products (μτe and μτh) showed μτe = 2×10-3 cm2/V (μτh = 8×10-5 cm2/V) and 3-6×10-3 cm2/V (μτh = 4- 6×10-5 cm2/V) for CdTe and CZT, respectively. Detectors in single pixel, Frisch collar, and coplanar grid geometries were fabricated. Detectors in Frisch grid and guard-ring configuration were found to exhibit energy resolution of 1.4% and 2.6 %, respectively, for 662 keV gamma rays. Assessments of the detector performance have been carried out also using 241Am (60 keV) showing energy resolution of 4.2% FWHM.

  8. Position sensitive detector with semiconductor and image electron tube comprising such a detector

    International Nuclear Information System (INIS)

    This invention concerns a position sensitive detector comprising a semiconducting substrate. It also concerns the electron tubes in which the detector may be incorporated in order to obtain an image formed at the tube input by an incident flux of particles or radiation. When a charged particle or group of such particles, electrons in particular, enter the space charge region of an inversely biased semiconductor diode, the energy supplied by these particles releases in the diode a certain number of electron-hole pairs which move in the field existing in the area towards the diode contacts. A corresponding current arises in the connections of this diode which constitutes the signal corresponding to the incident energy. Such a tube or chain of tubes is employed in nuclear medicine for observing parts of the human body, particularly by gamma radiation

  9. Digital performance improvements of a CdTe pixel detector for high flux energy-resolved X-ray imaging

    International Nuclear Information System (INIS)

    Photon counting detectors with energy resolving capabilities are desired for high flux X-ray imaging. In this work, we present the performance of a pixelated Schottky Al/p-CdTe/Pt detector (4×4) coupled to a custom-designed digital readout electronics for high flux measurements. The detector (4×4×2 mm3) has an anode layout based on an array of 16 pixels with a geometric pitch of 1 mm (pixel size of 0.6 mm). The 4-channel readout electronics is able to continuously digitize and process the signals from each pixel, performing multi-parameter analysis (event arrival time, pulse shape, pulse height, pulse time width, etc.) even at high fluxes and at different throughput and energy resolution conditions. The spectroscopic response of the system to monochromatic X-ray sources, at both low and high rates, is presented with particular attention to the mitigation of some typical spectral distortions (pile-up, baseline shifts and charge sharing). At a photon counting rate of 520 kcps/pixel, the system exhibits an energy resolution (FWHM at 59.5 keV) of 4.6%, 7.1% and 9% at throughputs of 0.9%, 16% and 82%, respectively. Measurements of Ag-target X-ray spectra also show the ability of the system to perform accurate estimation of the input counting rate up to 1.1 Mcps/pixel. The aim of this work is to point out, beside the appealing properties of CdTe detectors, the benefits of the digital approach in the development of high-performance energy resolved photon counting (ERPC) systems for high flux X-ray imaging

  10. Polarisation measurements with a CdTe pixel array detector for Laue hard X-ray focusing telescopes

    CERN Document Server

    Caroli, E; Pisa, A; Stephen, J B; Frontera, F; Castanheira, M T D; Sordo, S; Caroli, Ezio; Silva, Rui M. Curado da; Pisa, Alessandro; Stephen, John B.; Frontera, Filippo; Castanheira, Matilde T. D.; Sordo, Stefano del

    2006-01-01

    Polarimetry is an area of high energy astrophysics which is still relatively unexplored, even though it is recognized that this type of measurement could drastically increase our knowledge of the physics and geometry of high energy sources. For this reason, in the context of the design of a Gamma-Ray Imager based on new hard-X and soft gamma ray focusing optics for the next ESA Cosmic Vision call for proposals (Cosmic Vision 2015-2025), it is important that this capability should be implemented in the principal on-board instrumentation. For the particular case of wide band-pass Laue optics we propose a focal plane based on a thick pixelated CdTe detector operating with high efficiency between 60-600 keV. The high segmentation of this type of detector (1-2 mm pixel size) and the good energy resolution (a few keV FWHM at 500 keV) will allow high sensitivity polarisation measurements (a few % for a 10 mCrab source in 106s) to be performed. We have evaluated the modulation Q factors and minimum detectable polaris...

  11. Semiconductor Detector Developments for High Energy Space Astronomy

    CERN Document Server

    Meuris, Aline

    2014-01-01

    The rise of high energy astrophysics and solar physics in the 20th century is linked to the development of space telescopes; since the 1960s they have given access to the X-ray and gamma-ray sky, revealing the most violent phenomena in the Universe. Research and developments in imaging concepts and sensing materials haven't stopped since yet to improve the sensitivity of the X-ray and gamma-ray observatories. The paper proposes an overview of instrument realizations and focuses on the innovative detection techniques and technologies for applications from 0.1 keV to 10 MeV energy range. Solid-state detectors are prominent solutions for space instrumentation because of their excellent imaging and spectroscopic capabilities with limited volume and power resources. Various detection concepts based on semiconductors (Compton camera, Cd(Zn)Te pixel hybrids, DePFET active pixel sensors) are under design or fabrication for the near-future missions like Astro-H, BepiColombo, Solar Orbiter. New technologies on sensing ...

  12. High frame rate measurements of semiconductor pixel detector readout IC

    International Nuclear Information System (INIS)

    We report on high count rate and high frame rate measurements of a prototype IC named FPDR90, designed for readouts of hybrid pixel semiconductor detectors used for X-ray imaging applications. The FPDR90 is constructed in 90 nm CMOS technology and has dimensions of 4 mm×4 mm. Its main part is a matrix of 40×32 pixels with 100 μm×100 μm pixel size. The chip works in the single photon counting mode with two discriminators and two 16-bit ripple counters per pixel. The count rate per pixel depends on the effective CSA feedback resistance and can be set up to 6 Mcps. The FPDR90 can operate in the continuous readout mode, with zero dead time. Due to the architecture of digital blocks in pixel, one can select the number of bits read out from each counter from 1 to 16. Because in the FPDR90 prototype only one data output is available, the frame rate is 9 kfps and 72 kfps for 16 bits and 1 bit readout, respectively (with nominal clock frequency of 200 MHz).

  13. Semiconductor detector developments for high energy space astronomy

    International Nuclear Information System (INIS)

    The rise of high energy astrophysics and solar physics in the 20th century is linked to the development of space telescopes; since the 1960s they have given access to the X-ray and gamma-ray sky, revealing the most violent phenomena in the Universe. Research and developments in imaging concepts and sensing materials haven't stopped since yet to improve the sensitivity of the X-ray and gamma-ray observatories. The paper proposes an overview of instrument realizations and focuses on the innovative detection techniques and technologies for applications from 0.1 keV to 10 MeV energy range. Solid-state detectors are prominent solutions for space instrumentation because of their excellent imaging and spectroscopic capabilities with limited volume and power resources. Various detection concepts based on semiconductors (Compton camera, Cd(Zn)Te pixel hybrids, DePFET active pixel sensors) are under design or fabrication for the near-future missions like Astro-H, BepiColombo, Solar Orbiter. New technologies on sensing materials, front-end electronics, interconnect processes are under study for the next generation of instruments to push back our knowledge of star and galaxy formation and evolution

  14. High-resistance low-noise registor for spectrometers with a cooled semiconductor detector

    International Nuclear Information System (INIS)

    High-resistance 10-50 GΩ low-noise resistors for preamplifiers of spectrometers with cooled semiconductor detectors are designed and tested. The noise level of these resistors is four times lower than that of serial KVM type resistors

  15. Industrial workshop on LASL semiconductor radiation-detector research and development

    International Nuclear Information System (INIS)

    An Industrial Workshop on LASL Semiconductor Radiation Detector Research and Development was held at the Los Alamos Scientific Laboratory (LASL) in the spring of 1977. The purpose was to initiate communication between our detector research and development program and industry. LASL research programs were discussed with special emphasis on detector problems. Industrial needs and capabilities in detector research and development were also presented. Questions of technology transfer were addressed. The notes presented here are meant to be informal, as were the presentations

  16. Simulation of charge transport in pixelated CdTe

    International Nuclear Information System (INIS)

    The Voxel Imaging PET (VIP) Pathfinder project intends to show the advantages of using pixelated semiconductor technology for nuclear medicine applications to achieve an improved image reconstruction without efficiency loss. It proposes designs for Positron Emission Tomography (PET), Positron Emission Mammography (PEM) and Compton gamma camera detectors with a large number of signal channels (of the order of 106). The design is based on the use of a pixelated CdTe Schottky detector to have optimal energy and spatial resolution. An individual read-out channel is dedicated for each detector voxel of size 1 × 1 × 2 mm3 using an application-specific integrated circuit (ASIC) which the VIP project has designed, developed and is currently evaluating experimentally. The behaviour of the signal charge carriers in CdTe should be well understood because it has an impact on the performance of the readout channels. For this purpose the Finite Element Method (FEM) Multiphysics COMSOL software package has been used to simulate the behaviour of signal charge carriers in CdTe and extract values for the expected charge sharing depending on the impact point and bias voltage. The results on charge sharing obtained with COMSOL are combined with GAMOS, a Geant based particle tracking Monte Carlo software package, to get a full evaluation of the amount of charge sharing in pixelated CdTe for different gamma impact points

  17. Low-noise analog front-end signal processing channel integration for pixelated semiconductor radiation detector

    OpenAIRE

    Lin, Ming-Cheng

    2012-01-01

    In the research development of the medical nuclear imaging, the low noise performance has always been a mandatory requirement in the design of the semiconductor pixelated radiation detector system in order to achieve the high detectability of the charge signal. The noise-optimized analog front-end signal processing channel composed of the charge sensitive amplifier and the pulse shaper is used extensively in processing the radiation charge signals from the pixelated semiconductor detector. Th...

  18. Material reconstruction with the Medipix2 detector with CdTe sensor

    OpenAIRE

    Guni, Ewald; Durst, J.; Michel, T; Anton, G.

    2013-01-01

    The new generation of photon counting pixelated X-ray detectors like the Medipix2 detector are gaining increasing interest in medical imaging. In contrast to conventional systems which integrate the charge released in the sensor they are able to count single photons. With this imaging detector it is possible to determine the energy of the incoming X-rays which opens up a new field of applications. One application is the detection of contrast agents in medical imaging which was shown for a sil...

  19. 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...

  20. Portable gamma- and X-ray analyzers based on CdTe p-i-n detectors

    CERN Document Server

    Khusainov, A K; Bahlanov, S V; Derbin, A V; Ivanov, V V; Lysenko, V V; Morozov, F; Mouratov, V G; Muratova, V N; Petukhov, Y A; Pirogov, A M; Polytsia, O P; Saveliev, V D; Solovei, V A; Yegorov, K A; Zhucov, M P

    1999-01-01

    Several portable instruments are designed using previously reported CdTe detector technology. These can be divided into three groups according to their energy ranges: (1) 3-30 keV XRF analyzers, (2) 5-120 keV wide range XRF analyzers and (3) gamma-ray spectrometers for operation up to 1500 keV. These instruments are used to inspect several hundreds of samples in situ during a working day in applications such as a metal alloy verification at customs control. Heavy metals are identified through a 3-100 mm thick package with these instruments. Surface contamination by heavy metals (for example toxins such as Hg, Th and Pb in housing environmental control), the determination of Pb concentration in gasoline, geophysical control in mining, or nuclear material control are other applications. The weight of these XRF probes is about 1 kg and two electronic designs are used: one with embedded computer and another based on a standard portable PC. The instruments have good precision and high productivity for measurements...

  1. Optical characterization of wide-gap detector-grade semiconductors

    International Nuclear Information System (INIS)

    Wide bandgap semiconductors are being widely investigated because they have the potential to satisfy the stringent material requirements of high resolution, room temperature gamma-ray spectrometers. In particular, Cadmium Zinc Telluride (Cd1-xZnxTe, x∼0.1) and Thallium Bromide (Tl Br), due to their combination of high resistivity, high atomic number and good electron mobility, have became very promising candidates for use in X- and gamma-ray detectors operating at room temperature. In this study, carrier trapping times were measured in CZT and Tl Br as a function of temperature and material quality. Carrier lifetimes and tellurium inclusion densities were measured in detector-grade Cadmium Zinc Telluride (CZT) crystals grown by the High Pressure Bridgman method and Modified Bridgman method. Excess carriers were produced in the material using a pulsed YAG laser with a 1064 nm wavelength and 7 ns pulse width. Infrared microscopy was used to measure the tellurium defect densities in CZT crystals. The electronic decay was optically measured at room temperature. Spatial mapping of lifetimes and defect densities in CZT was performed to determine the relationship between defect density and electronic decay. A significant and strong correlation was found between the volume fraction of tellurium inclusions and the carrier trapping time. Carrier trapping times and tellurium inclusions were measured in CZT in the temperature range from 300 K to 110 K and the results were analyzed using a theoretical trapping model. Spatial mapping of carrier trapping times and defect densities in CZT was performed to determine the relationship between defect density and electronic decay. While a strong correlation between trapping time and defect density of tellurium inclusions was observed, there was no significant change in the trap energy. Carrier trapping times were measured in detector grade thallium bromide (Tl Br) and compared with the results for cadmium zinc telluride (CZT) in a

  2. System for numeric-pulsed correction of energetic characterization of semiconductor detectors

    International Nuclear Information System (INIS)

    The system of numeric-pulsed correction of energetic characterization of semiconductor detectors such as pulses from detector are amplified in amplifier, transmitted by main track of measuring system having amplitude discriminator and by track of correction system and then pulses from both tracks are summed up in the system of logical sum. 2 figs. (A.S.)

  3. Comparison of calculated absolute full-energy peak efficiencies of CdTe and NaI detectors in the photon energy region of 15-2000 keV

    International Nuclear Information System (INIS)

    A comparison of the calculated absolute full-energy peak efficiencies of CdTe and NaI detectors, i.e. the ratio of the number of counts under the full-energy peak (FEP) to the number of photons at the same energy emitted by the source, is made for six different detectors and three source sizes. The CdTe and NaI detectors are assumed to be of equal volume. The calculations are performed in the photon energy region 15-2000 keV using water, muscle and blood as source media. (author)

  4. An Approach to Unfold Neutron Spectra Measured by a 3He Semiconductor Detector

    International Nuclear Information System (INIS)

    In measurements of fast neutron spectra by a 3He semiconductor detector, the unfolding method is not usually required. The unfolding method based on principle of maximum likelihood that incorporates the Gaussian approximation of counting statistics is developed and implemented in the MLMHE31 numerical code for application in fast neutron spectrometry by 3He semiconductor detectors. The derived likelihood equations have been solved using method of the singular value decomposition of the response matrix. For this inverse problem, the detector responses were generated by the Monte Carlo technique. (author)

  5. Model-based pulse shape correction for CdTe detectors

    CERN Document Server

    Bargholtz, C; Maartensson, L

    1999-01-01

    We present a systematic method to improve energy resolution of CdTe-detector systems with full control of the efficiency. Sampled pulses and multiple amplifier data are fitted by a model of the pulse shape including the deposited energy and the interaction point within the detector as parameters. We show the decisive improvements of spectral resolution and photo-peak efficiency that is obtained without distortion of spectral shape. The information concerning the interaction depth of individual events can be used to discriminate between beta particles and gamma quanta. (author)

  6. Model-based pulse shape correction for CdTe detectors

    Science.gov (United States)

    Bargholtz, Chr.; Fumero, E.; Mårtensson, L.

    1999-02-01

    We present a systematic method to improve energy resolution of CdTe-detector systems with full control of the efficiency. Sampled pulses and multiple amplifier data are fitted by a model of the pulse shape including the deposited energy and the interaction point within the detector as parameters. We show the decisive improvements of spectral resolution and photo-peak efficiency that is obtained without distortion of spectral shape. The information concerning the interaction depth of individual events can be used to discriminate between beta particles and gamma quanta.

  7. Gamma spectroscopic measurements using the PID350 pixelated CdTe radiation detector

    CERN Document Server

    Karafasoulis, K; Seferlis, S; Papadakis, I; Loukas, D; Lambropoulos, C; Potiriadis, C

    2010-01-01

    Spectroscopic measurements are presented using the PID350 pixelated gamma radiation detectors. A high-speed data acquisition system has been developed in order to reduce the data loss during the data reading in case of a high flux of photons. A data analysis framework has been developed in order to improve the resolution of the acquired energy spectra, using specific calibration parameters for each PID350's pixel. Three PID350 detectors have been used to construct a stacked prototype system and spectroscopic measurements have been performed in order to test the ability of the prototype to localize radioactive sources.

  8. Cd1-xMnxTe semiconductor radiation detectors for medical applications

    International Nuclear Information System (INIS)

    Full text : This work tells about semiconductor nuclear radiation detectors which had experienced a rather rapid development in the last few years. They are now used in a large variety of fields, including nuclear physics, X-ray and gamma-ray astronomy and nuclear medicine. In recent years a substantial international effort had been invested in developing a range of compound semiconductors with wide band gap and high atomic number for X- and gamma-ray detectors. Among the compound semiconductors, cadmium manganese telluride were the most promising materials for radiation detectors with good energy resolution, high detection efficiency and room temperature operation. Also these detectors were suitable for the development of portable systems for mammographic X-ray spectroscopy.

  9. Semiconductor scintillator detector for gamma radiation; Detector cintilador semicondutor para radiacao gama

    Energy Technology Data Exchange (ETDEWEB)

    Laan, F.T.V. der; Borges, V.; Zabadal, J.R.S., E-mail: ftvdl@ufrgs.br, E-mail: borges@ufrgs.br, E-mail: jorge.zabadal@ufrgs.br [Universidade Federal do Rio Grande do Sul (GENUC/DEMEC/UFRGS), Porto Alegre, RS (Brazil). Grupo de Estudos Nucleares. Departamento de Engenharia Mecanica

    2015-07-01

    Nowadays the devices employed to evaluate individual radiation exposition are based on dosimetric films and thermoluminescent crystals, whose measurements must be processed in specific transductors. Hence, these devices carry out indirect measurements. Although a new generation of detectors based on semiconductors which are employed in EPD's (Electronic Personal Dosemeters) being yet available, it high producing costs and large dimensions prevents the application in personal dosimetry. Recent research works reports the development of new detection devices based on photovoltaic PIN diodes, which were successfully employed for detecting and monitoring exposition to X rays. In this work, we step forward by coupling a 2mm anthracene scintillator NE1, which converts the high energy radiation in visible light, generating a Strong signal which allows dispensing the use of photomultipliers. A low gain high performance amplifier and a digital acquisition device are employed to measure instantaneous and cumulative doses for energies ranging from X rays to Gamma radiation up to 2 MeV. One of the most important features of the PIN diode relies in the fact that it can be employed as a detector for ionization radiation, since it requires a small energy amount for releasing electrons. Since the photodiode does not amplify the corresponding photon current, it must be coupled to a low gain amplifier. Therefore, the new sensor works as a scintillator coupled with a photodiode PIN. Preliminary experiments are being performed with this sensor, showing good results for a wide range of energy spectrum. (author)

  10. Plasmonic Nanoslit Array Enhanced Metal-Semiconductor-Metal Optical Detectors

    CERN Document Server

    Eryilmaz, Sukru Burc; Okyay, Ali K

    2014-01-01

    Metallic nanoslit arrays integrated on germanium metal-semiconductor-metal photodetectors show many folds of absorption enhancement for transverse-magnetic polarization in the telecommunication C-band. Such high enhancement is attributed to resonant interference of surface plasmon modes at the metal-semiconductor interface. Horizontal surface plasmon modes were reported earlier to inhibit photodetector performance. We computationally show, however, that horizontal modes enhance the efficiency of surface devices despite reducing transmitted light in the far field.

  11. Continued development of room temperature semiconductor nuclear detectors

    Science.gov (United States)

    Kim, Hadong; Cirignano, Leonard; Churilov, Alexei; Ciampi, Guido; Kargar, Alireza; Higgins, William; O'Dougherty, Patrick; Kim, Suyoung; Squillante, Michael R.; Shah, Kanai

    2010-08-01

    Thallium bromide (TlBr) and related ternary compounds, TlBrI and TlBrCl, have been under development for room temperature gamma ray spectroscopy due to several promising properties. Due to recent advances in material processing, electron mobility-lifetime product of TlBr is close to Cd(Zn)Te's value which allowed us to fabricate large working detectors. We were also able to fabricate and obtain spectroscopic results from TlBr Capacitive Frisch Grid detector and orthogonal strip detectors. In this paper we report on our recent TlBr and related ternary detector results and preliminary results from Cinnabar (HgS) detectors.

  12. Fast photoconductor CdTe detectors for synchrotron x-ray studies

    International Nuclear Information System (INIS)

    The Advanced Photon Source will be that brightest source of synchrotron x-rays when it becomes operational in 1996. During normal operation, the ring will be filled with 20 bunches of positrons with an interbunch spacing of 177 ns and a bunch width of 119 ps. To perform experiments with x-rays generated by positrons on these time scales one needs extremely high speed detectors. To achieve the necessary high speed, we are developing MBE-grown CdTe-base photoconductive position sensitive array detectors. The arrays fabricated have 64 pixels with a gap of 100 μm between pixels. The high speed response of the devices was tested using a short pulse laser. X-ray static measurements were performed using an x-ray tube and synchrotron radiation to study the device's response to flux and wavelength changes. This paper presents the response of the devices to some of these tests and discusses different physics aspects to be considered when designing high speed detectors

  13. X-ray diffraction study of epitaxial heterostructures of II-VI CdTe and ZnTe semiconductors; Etude par diffraction de rayons X d`heterostructures epitaxiees a base des semi-conducteurs II-VI CdTe et ZnTe

    Energy Technology Data Exchange (ETDEWEB)

    Bouchet-Boudet, N.

    1996-10-07

    This work deals with the structural study of II-VI semiconductor (CdTe and ZnTe) heterostructures by X-ray diffraction and reflectivity. These heterostructures have a high lattice parameter misfit and are grown by Molecular Beam Epitaxy. Two main subjects are developed: the characterization of ZnTe wires, grown by step propagation on a CdTe (001) vicinal surface, and the study of the vertical correlations in Cd{sub 0.8}Zn{sub 0.2}Te / CdTe superlattices and superlattices made of ZnTe fractional layers spaced by CdTe. The growth of organised system is up to date; its aim is to realize quantum boxes (or wires) superlattices which are laterally and vertically ordered. The deformation along the growth axis induced by a ZnTe fractional layer inserted in a CdTe matrix is modelled, in the kinematical approximation, to reproduce the reflectivity measured around the substrate (004) Bragg peak. The lateral periodicity of the wires, deposited on a vicinal surface is a new and difficult subject. Some results are obtained on a vertical superlattice grown on a 1 deg. mis-cut surface. The in-plane and out-of-plane correlation lengths of a Cd{sub 0.8}Zn{sub 0.2}Te / CdTe superlattice are deduced from the diffused scattered intensity measured at grazing incidence. The calculations are made within the `distorted Wave Born Approximation`. The vertical correlation in ZnTe boxes (or wines) superlattices can be measured around Bragg peaks. It is twice bigger in a superlattice grown on a 2 deg. mis-cut substrate than a nominal one. (author). 74 refs.

  14. Exploring graphene field effect transistor devices to improve spectral resolution of semiconductor radiation detectors

    Energy Technology Data Exchange (ETDEWEB)

    Harrison, Richard Karl [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Howell, Stephen Wayne [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Martin, Jeffrey B. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Hamilton, Allister B. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2013-12-01

    Graphene, a planar, atomically thin form of carbon, has unique electrical and material properties that could enable new high performance semiconductor devices. Graphene could be of specific interest in the development of room-temperature, high-resolution semiconductor radiation spectrometers. Incorporating graphene into a field-effect transistor architecture could provide an extremely high sensitivity readout mechanism for sensing charge carriers in a semiconductor detector, thus enabling the fabrication of a sensitive radiation sensor. In addition, the field effect transistor architecture allows us to sense only a single charge carrier type, such as electrons. This is an advantage for room-temperature semiconductor radiation detectors, which often suffer from significant hole trapping. Here we report on initial efforts towards device fabrication and proof-of-concept testing. This work investigates the use of graphene transferred onto silicon and silicon carbide, and the response of these fabricated graphene field effect transistor devices to stimuli such as light and alpha radiation.

  15. Advanced radiation detector development: Advanced semiconductor detector development: Development of a oom-temperature, gamma ray detector using gallium arsenide to develop an electrode detector

    International Nuclear Information System (INIS)

    The advanced detector development project at the University of Michigan has completed the first full year of its current funding. Our general goals are the development of radiation detectors and spectrometers that are capable of portable room temperature operation. Over the past 12 months, we have worked primarily in the development of semiconductor spectrometers with open-quotes single carrierclose quotes response that offer the promise of room temperature operation and good energy resolution in gamma ray spectroscopy. We have also begun a small scale effort at investigating the properties of a small non-spectroscopic detector system with directional characteristics that will allow identification of the approximate direction in which gamma rays are incident. These activities have made use of the extensive clean room facilities at the University of Michigan for semiconductor device fabrication, and also the radiation measurement capabilities provided in our laboratory in the Phoenix Building on the North Campus. In addition to our laboratory based activities, Professor Knoll has also been a participant in several Department of Energy review activities held in the Forrestal Building and at the Germantown site. The most recent of these has been service on a DOE review panel chaired by Dr. Hap Lamonds that is reviewing the detector development programs supported through the Office of Arms Control and International Security

  16. Development of the ''X'tal cube''. The next generation PET detector using semiconductor photo-detectors

    International Nuclear Information System (INIS)

    We are engaged in the development of an ''X'tal cube'' which is a three-dimensional (3D) block detector for the next-generation positron emission tomography (PET) system. It consists of a 3D array of cubic crystal segments (a crystal block) and semiconductor photo-detectors such as Avalanche photodiodes (APD) or Multi-Pixel Photon Counters (MPPC). By identifying the light-emitted crystal segments, it is possible to obtain 3D position information of gamma-rays absorbed in the crystal block. In the crystal block, there are no reflectors inserted between the crystal segments, and the photo-detectors are located on the surface area of the crystal block. This detector arrangement minimizes light attenuation in the crystal block as the path length from the scintillation points to the photo-detectors is minimum so as to achieve favorable detector performance. By sparsely arranging the photo-detectors on the surface of the crystal block, it is possible to reduce the number of photo-detectors. The area not coupled to the photo-detectors is covered with reflectors. We have investigated crystal identification performance as a function of the photo-detector arrangement as a preliminary study to the development of an X'tal cube. (author)

  17. Comparison of beam quality parameters computed from mammographic x-ray spectra measured with different high-resolution semiconductor detectors

    International Nuclear Information System (INIS)

    In this work, the x-ray spectra of standard mammographic radiation qualities were measured with Si(Li), SDD and CdTe detectors. The x-ray source was an industrial x-ray tube with an Mo anode, operating at constant tube potentials between 20 and 35 kV, and adapted with filters of Mo and Al, in order to reproduce standard mammographic beam qualities. The measured spectra were corrected by the energy response of each detector, which were determined using Monte Carlo simulation. From the corrected spectra, values of HVL and mean energies were computed. The results show that, after correction by the energy response functions, all detectors provided similar bremsstrahlung spectra, whereas greater differences were observed in the characteristic peaks, due to the different energy resolutions of the detection systems. The comparison between values of HVL and mean energies calculated from the spectra obtained with each detector also show good agreement, with differences up to 5.5%. For most of the conditions studied, the differences between the measured values of HVL and those computed from the corrected spectra are lesser than the experimental uncertainties. Finally, our results show that, although the detectors Si(Li), SDD and CdTe provide similar spectra, the use of the first two detectors, which combine high energy resolution and low spectral distortions, is recommended, since they provide more accurate spectra from which several quality parameters can be determined. - Highlights: ► The Si(Li), SDD and CdTe detectors were applied for mammographic x-ray spectroscopy. ► The x-ray spectra measured with these detectors are similar, showing differences only in the characteristic peaks. ► The mean energies and values of HVL computed from the measured spectra with these detectors also show small differences. ► The use of Si(Li) detectors and SDD is advantageous due to their better energy resolution

  18. Epitaxial silicon semiconductor detectors, past developments, future prospects

    International Nuclear Information System (INIS)

    A review of the main physical characteristics of epitaxial silicon as it relates to detector development is presented. As examples of applications results are presented on (1) epitaxial silicon avalanche diodes (ESAD); signal-to-noise, non-linear aspects of the avalanche gain mechanism, gain-bandwidth product, (2) ultrathin epitaxial silicon surface barrier (ESSB) detectors, response to heavy ions, (3) an all-epitaxial silicon diode (ESD), response to heavy ions, charge transport and charge defect. Future prospects of epitaxial silicon as it relates to new detector designs are summarized

  19. Nanosecond X-ray detector based on high resistivity ZnO single crystal semiconductor

    Science.gov (United States)

    Zhao, Xiaolong; Chen, Liang; He, Yongning; Liu, Jinliang; Peng, Wenbo; Huang, Zhiyong; Qi, Xiaomeng; Pan, Zijian; Zhang, Wenting; Zhang, Zhongbing; Ouyang, Xiaoping

    2016-04-01

    The pulse radiation detectors are sorely needed in the fields of nuclear reaction monitoring, material analysis, astronomy study, spacecraft navigation, and space communication. In this work, we demonstrate a nanosecond X-ray detector based on ZnO single crystal semiconductor, which emerges as a promising compound-semiconductor radiation detection material for its high radiation tolerance and advanced large-size bulk crystal growth technique. The resistivity of the ZnO single crystal is as high as 1013 Ω cm due to the compensation of the donor defects (VO) and acceptor defects (VZn and Oi) after high temperature annealing in oxygen. The photoconductive X-ray detector was fabricated using the high resistivity ZnO single crystal. The rise time and fall time of the detector to a 10 ps pulse electron beam are 0.8 ns and 3.3 ns, respectively, indicating great potential for ultrafast X-ray detection applications.

  20. Simulation of one-dimensionally polarized X-ray semiconductor detectors

    OpenAIRE

    Engel, K.J.; C. Herrmann

    2011-01-01

    Abstract: A pixelated X-ray semiconductor detector (=“direct converter”) is studied which contains an inhomogeneous electric field parallel to the depth axis caused by different concentrations of p- or n-doping. The X-ray energy deposition and charge movement within the detector is modeled in Monte-Carlo simulations which give access to astatistical analysis of electron drift times and current pulse widths for various degrees of static polarization. Integral charges induced on the pixel elect...

  1. Avalanche Process in Semiconductor Photo Detectors in the Context of the Feedback Theory

    Czech Academy of Sciences Publication Activity Database

    Kushpil, Vasilij

    Rijeka : InTech, 2012 - (Gateva, S.), s. 207-230 ISBN 978-953-51-0358-5. - (Electrical and Electronic Engineering) R&D Projects: GA MŠk LA08015 Institutional support: RVO:61389005 Keywords : avalanche process * photo detectors Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders http://www.intechopen.com/books/photodetectors/avalanche-process-in-semiconductor-photo-detectors-in-the-context-of-the-feedback- theory -

  2. Study of semiconductor detectors applied to diagnostic X-ray

    International Nuclear Information System (INIS)

    This work aims an evaluation of procedures for photons spectrum determination, produced by a X ray tube, normally used for medical diagnoses which operation voltage ranges from 20 to 150 kVp, to allow more precise characterization of the photon beam. The use of spectrum analysis will contribute to reduce the uncertainty in the ionization camera calibrations. For this purpose, two kind of detectors were selected, a Cadmium Zinc Telluride (CZT) and a planar HPGe detector. The X ray interaction with the detector's crystal produces, by electronic processes, a pulse high distribution as an output, which is no the true photon spectrum, due to the presence of K shell escape peaks, Compton scattering and to the fact that the detectors efficiency diminish rapidly with the increase of the photon energy. A detailed analysis of the contributing factors to distortions in the spectrum is necessary and was performed by Monte Carlo calculation with the MCNP 4B computer code. In order to determine the actual photon spectrum for a X ray tube a spectra stripping procedure is described for the HPGe detector. The detector's response curves, determined by the Monte Carlo calculation, were compared to the experimental ones, for isotropic point sources. For the methodology validation, stripped spectra were compared to the theoretical ones, for the same X ray tube's settings, for a qualitative evaluation. The air kerma rate calculated with the photon spectra were compared to the direct measurement using an ionization chamber, for a quantitative evaluation. (author)

  3. Interface visualization of multiphase flow by using a fast x-ray CT scanner. Development of sensitive semi-conductor detector and its application to two-phase flow measurement

    International Nuclear Information System (INIS)

    Multi-dimensional interface dynamics in gas-liquid two-phase flow was measured by using a fast X-ray CT scanner recently developed with increased sensitivity in detector devices. CdTe, a composite semi-conductor material highly sensitive to X-ray, was employed in the sensing elements. Prior to installation into the CT system, the detector was placed in a line sensor format to examine their visualization capability. Hardware objects on a moving belt were successfully visualized. Using the CT system equipped with the CdTe detector module, measurement accuracy of interface area and volume of objects were evaluated by numerical simulation and by measuring plastic models representing typical interface shapes observed in two phase flow. By comparing the measurements with their corresponding known dimensions, we estimated the measurement accuracy of cross section and interface length of bubbles, which is a function of object diameter, moving velocity, and location at which the object was detected. With the knowledge of measurement accuracy, we applied the fast X-ray CT to gas-liquid two-phase flow. Gas-phase distribution in the cross section was visualized and analyzed to provide instantaneous void fraction and interface length, both quantities not available with previous techniques. Interface deformation was quantitatively measured by introducing the deformation factor. (author)

  4. Cryogenic Semiconductor Detectors: Simulation of Signal Formation & Irradiation Beam Test

    CERN Document Server

    AUTHOR|(CDS)2091318; Stamoulis, G; Vavougios, D

    The Beam Loss Monitoring system of the Large Hadron Collider is responsible for the pro- tection of the machine from damage and for the prevention of a magnet quench. Near the interaction points of the LHC, in the triplet magnets area, the BLMs are sensitive to the collision debris, limiting their ability to distinguish beam loss signal from signal caused due to the collision products. Placing silicon & diamond detectors inside the cold mass of the mag- nets, in liquid helium temperatures, would provide significant improvement to the precision of the measurement of the energy deposition in the superconducting coil of the magnet. To further study the signal formation and the shape of the transient current pulses of the aforementioned detectors in cryogenic temperatures, a simulation application has been developed. The application provides a fast way of determining the electric field components inside the detectors bulk and then introduces an initial charge distribution based on the properties of the radiat...

  5. Experimental characterization of semiconductor-based thermal neutron detectors

    Energy Technology Data Exchange (ETDEWEB)

    Bedogni, R., E-mail: roberto.bedogni@lnf.infn.it [IFNF—LNF, via E. Fermi n. 40, 00044 Frascati, Roma (Italy); Bortot, D.; Pola, A.; Introini, M.V.; Lorenzoli, M. [Politecnico di Milano, Dipartimento di Energia, via La Masa 34, 20156 Milano (Italy); INFN—Milano, Via Celoria 16, 20133 Milano (Italy); Gómez-Ros, J.M. [IFNF—LNF, via E. Fermi n. 40, 00044 Frascati, Roma (Italy); CIEMAT, Av. Complutense 40, 28040 Madrid (Spain); Sacco, D. [IFNF—LNF, via E. Fermi n. 40, 00044 Frascati, Roma (Italy); INAIL—DIT, Via di Fontana Candida 1, 00040 Monteporzio Catone (Italy); Esposito, A.; Gentile, A.; Buonomo, B. [IFNF—LNF, via E. Fermi n. 40, 00044 Frascati, Roma (Italy); Palomba, M.; Grossi, A. [ENEA Triga RC-1C.R. Casaccia, via Anguillarese 301, 00060 S. Maria di Galeria, Roma (Italy)

    2015-04-21

    In the framework of NESCOFI@BTF and NEURAPID projects, active thermal neutron detectors were manufactured by depositing appropriate thickness of {sup 6}LiF on commercially available windowless p–i–n diodes. Detectors with different radiator thickness, ranging from 5 to 62 μm, were manufactured by evaporation-based deposition technique and exposed to known values of thermal neutron fluence in two thermal neutron facilities exhibiting different irradiation geometries. The following properties of the detector response were investigated and presented in this work: thickness dependence, impact of parasitic effects (photons and epithermal neutrons), linearity, isotropy, and radiation damage following exposure to large fluence (in the order of 10{sup 12} cm{sup −2})

  6. On the Theory of Compensation in Lithium drifted Semiconductor Detectors

    International Nuclear Information System (INIS)

    The lithium ion drift method produces detectors with a highly but not perfectly compensated intrinsic region. The amount of fixed space charge left in the depleted layer and its dependence on drift and clean-up parameters is of great practical interest. The imperfect compensation is mainly due to the presence in the depletion layer of thermally generated electron-hole pairs swept apart by the voltage applied to the detector during drift. A theoretical model is developed which takes into account the influence on the fixed space charge of mobile carrier generation and recombination. When recombination of free electrons and holes is negligible the theory predicts the formation of linear space charge gradients. When recombination is strong a constant space charge throughout a large part of the compensated layer may result. The theoretical calculations are compared with experimental findings. The influence of space charge on detector performance is discussed

  7. Development of Thyroid Diagnostic Equipment Using Semiconductor Detector

    International Nuclear Information System (INIS)

    Current commercial gamma-ray imaging system are general purpose device designed to support a diagnosis for thyroid cancer. These generally require a reasonably large detector plate and the ability to image the thyroid. Recently, new applications of gamma-ray imaging system have emerged which place different demands on gamma-ray imaging system instrumentation, requiring high spatial resolution and sensitivity, in particular for imaging small volumes. These emerging applications, a large plate is not only not required but also limits the performance that can be achieved when imaging small volumes. Significant research has been undertaken in the development of read out schemes of scintillator crystal configurations in an attempt to improve the spatial resolution of gamma-ray imaging system. Silicon Photomultiplier (SiPM) detectors are attractive candidates for the replacement of Photomultiplier in nuclear imaging. Provide high gain with low voltage and fast response. We are developing a new gamma-ray imaging system detection module with depth of interaction capability. Pixilated scintillation crystals read out by SiPM 4 x 4 arrays form the basis of the new module. This article concentrates on comparison of the some kind of scintillator performance of the SiPM. In particular we are interested in measuring and quantitative improvement of the detector efficiency, linearity, and energy resolution of the SiPM based detector. Initial characterization of prototype detector consisting of a 4 x 4 SiPM array coupled to either the front surface of a 3 mm x 3 mm x 15 mm x 16 pics LYSO crystal. The readout system include SensL preamplifier circuit, anger logic circuit, Notice Scintillate ADC(FADC) and collect and analysis data software root. The parameters that have been measured are: detector efficiency, linearity, and energy resolution. Best energy resolution was experimentally measured 11% for 511 keV and spatial resolutions < 3 mm (22Na, luCi).. (authors)

  8. Organic semiconductors as real-time radiation detectors

    International Nuclear Information System (INIS)

    In this study, the possibility of using π-conjugated organic semiconducting polymers as real-time radiation detectors was explored. Polyaniline (PAni) was used to fabricate radiation sensors because of its relative long-term stability in air. Each fabricated sensor was then subjected to irradiation by α- and β-particles, and the real-time response was measured. The multichannel analyzer (MCA) data of the response signal for each irradiation was acquired and the detection efficiency, relative to the electrode bias voltage of the detector, was extracted

  9. The absolute calibration of semiconductor detectors in the Neutrino beam of CERN

    International Nuclear Information System (INIS)

    The report describes a method for the calibration of semiconductor detectors. A nuclear emulsion is exposed to charged particles (muons) immediately in front of the detector. The muons also scatter delta electrons which give traces in the emulsion. The traces can be counted under a microscope. The separation of the muons and delta electrons takes place by angular distribution. The muons are counted per area unit. The flow is related to the signal of the detector and an absolute counting is achieved. (G.B)

  10. Application of the TSVD unfolding method for reconstruction of primary X-ray spectra using semiconductor detectors

    International Nuclear Information System (INIS)

    A thorough knowledge of the primary spectrum is very important to perform a quality control (QC) of X-ray tubes. In previous works, a methodology to assess primary spectrum using a Compton spectrometer has been analyzed. In summary, this methodology consists of the use of a Monte Carlo model (normally the MCNP code is applied) to reproduce the physical phenomena involving the interaction of photons and electrons with the Compton spectrometer and with a high purity Germanium detector. By means of this Monte Carlo model, a response matrix can be built, relating the Pulse Height Distribution (PHD) registered in the detector, with the primary X-ray spectrum. Subsequently, an unfolding method based on the application of a Truncated Singular Value Decomposition (TSVD) is applied to the response matrix in order to assess the primary spectrum. Germanium detectors present an optimal Full Width at Half Maximum (FWHM) value for energies up to 150 keV covering mammographic and diagnostic energy range. However, the need of a liquid nitrogen cooling system introduces some troubles in the data acquisition process. In this work, two other detection systems are proposed, a Silicon and a Cadmium-Telluride detector (CdTe), which do not require liquid nitrogen cooling system, and consequently the acquisition process is simplified. The weak point of this kind of detectors is the loss of energy resolution. Despite their low resolution the Silicon and CdTe detector have been considered due to both their low cost and easy handling and portability. The main goal of this paper is to determine whether the TSVD unfolding method is adequate to provide an acceptable reproduction of characteristics lines despite the low resolution of the detectors considered. The MCNP5 code, based on the Monte Carlo method has been used to simulate the actual physic processes for spectra acquisition analysis with Germanium, Silicon and CdTe detectors. (author)

  11. X-ray imaging with photon counting hybrid semiconductor pixel detectors

    CERN Document Server

    Manolopoulos, S; Campbell, M; Snoeys, W; Heijne, Erik H M; Pernigotti, E; Raine, C; Smith, K; Watt, J; O'Shea, V; Ludwig, J; Schwarz, C

    1999-01-01

    Semiconductor pixel detectors, originally developed for particle physics experiments, have been studied as X-ray imaging devices. The performance of devices using the OMEGA 3 read-out chip bump-bonded to pixellated silicon semiconductor detectors is characterised in terms of their signal-to-noise ratio when exposed to 60 kVp X-rays. Although parts of the devices achieve values of this ratio compatible with the noise being photon statistics limited, this is not found to hold for the whole pixel matrix, resulting in the global signal-to-noise ratio being compromised. First results are presented of X-ray images taken with a gallium arsenide pixel detector bump-bonded to a new read-out chip, (MEDIPIX), which is a single photon counting read-out chip incorporating a 15-bit counter in every pixel. (author)

  12. X-ray imaging using single photon processing with semiconductor pixel detectors

    International Nuclear Information System (INIS)

    More than 10 years experience with semiconductor pixel detectors for vertex detection in high-energy physics experiments together with the steady progress in CMOS technology opened the way for the development of single photon processing pixel detectors for various applications including medical X-ray imaging. The state of the art of such pixel devices consists of pixel dimensions as small as 55x55 μm2, electronic noise per pixel 100 e- rms, signal-to-noise discrimination levels around 1000 e- with a spread 50 e- and a dynamic range up to 32 bits/pixel. Moreover, the high granularity of hybrid pixel detectors makes it possible to probe inhomogeneities of the attached semiconductor sensor

  13. X-ray imaging using single photon processing with semiconductor pixel detectors

    CERN Document Server

    Mikulec, Bettina; Heijne, Erik H M; Llopart-Cudie, Xavier; Tlustos, Lukas

    2003-01-01

    More than 10 years experience with semiconductor pixel detectors for vertex detection in high energy physics experiments together with the steady progress in CMOS technology opened the way for the development of single photon processing pixel detectors for various applications including medical X-ray imaging. The state of the art of such pixel devices consists of pixel dimensions as small as 55x55 um2, electronic noise per pixel <100 e- rms, signal-to-noise discrimination levels around 1000 e- with a spread <50 e- and a dynamic range up to 32 bits per pixel. Moreover, the high granularity of hybrid pixel detectors makes it possible to probe inhomogeneities of the attached semiconductor sensor.

  14. X-ray imaging with photon counting hybrid semiconductor pixel detectors

    Energy Technology Data Exchange (ETDEWEB)

    Manolopoulos, S.; Bates, R.; Campbell, M.; Snoeys, W.; Heijne, E.; Pernigotti, E.; Raine, C.; Smith, K. E-mail: k.smith@physics.gla.ac.uk; Watt, J.; O' Shea, V.; Ludwig, J.; Schwarz, C

    1999-09-11

    Semiconductor pixel detectors, originally developed for particle physics experiments, have been studied as X-ray imaging devices. The performance of devices using the {omega}3 read-out chip bump-bonded to pixellated silicon semiconductor detectors is characterised in terms of their signal-to-noise ratio when exposed to 60 kVp X-rays. Although parts of the devices achieve values of this ratio compatible with the noise being photon statistics limited, this is not found to hold for the whole pixel matrix, resulting in the global signal-to-noise ratio being compromised. First results are presented of X-ray images taken with a gallium arsenide pixel detector bump-bonded to a new read-out chip, (MEDIPIX), which is a single photon counting read-out chip incorporating a 15-bit counter in every pixel. (author)

  15. Current problems in semiconductor detectors for high energy physics after particle irradiations

    International Nuclear Information System (INIS)

    The use of semiconductor materials as detectors in high radiation environments, as expected in future high energy accelerators or in space missions, poses severe problems in long-time operations, due to changes in the properties of the material, and consequently in the performances of detectors. This talk presents the major theoretical areas of current problems, reviews the works in this field and the stage of their understanding, including author's contributions The mechanisms of interaction of the projectile with the semiconductor, the production of primary defects, the physical quantities and the equations able to characterise and describe the radiation effects, and the equations of kinetics of defects are considered. Correlation between microscopic damage and detector performances and the possible ways to optimise the radiation hardness of materials are discussed. (author)

  16. CDZNTE ROOM-TEMPERATURE SEMICONDUCTOR GAMMA-RAY DETECTOR FOR NATIONAL-SECURITY APPLICATIONS

    International Nuclear Information System (INIS)

    One important mission of the Department of Energy's National Nuclear Security Administration is to develop reliable gamma-ray detectors to meet the widespread needs of users for effective techniques to detect and identify special nuclear- and radioactive-materials. Accordingly, the Nonproliferation and National Security Department at Brookhaven National Laboratory was tasked to evaluate existing technology and to develop improved room-temperature detectors based on semiconductors, such as CdZnTe (CZT). Our research covers two important areas: Improving the quality of CZT material, and exploring new CZT-based gamma-ray detectors. In this paper, we report on our recent findings from the material characterization and tests of actual CZT devices fabricated in our laboratory and from materials/detectors supplied by different commercial vendors. In particular, we emphasize the critical role of secondary phases in the current CZT material and issues in fabricating the CZT detectors, both of which affect their performance

  17. Development of large area silicon semiconductor detectors for use in the current mode

    International Nuclear Information System (INIS)

    Large area silicon semiconductor detectors for use in the current mode, with their dimensions of φ40, φ50 and φ60 mm, their depletion thickness of 200-300 μm, have been developed. Their performance measurements have been made, which indicate that the developed detectors can satisfactorily meet the needs in expectation. Compared with the detectors commercially available on the market, authors' large PIN detectors can serve both as reliable and efficient high-resolution devices for nuclear counting experiments, as well as monitors of high-intensity radiation fields in the current mode under a bias of 100-1000 V, while the detectors commercially available are only for the counting use

  18. X-ray measurement with Pin type semiconductor detectors

    International Nuclear Information System (INIS)

    Here are presented the experimental results of the applications of Pin type radiation detectors developed in a National Institute of Nuclear Research (ININ) project, in the measurement of low energy gamma and X-rays. The applications were oriented mainly toward the Medical Physics area. It is planned other applications which are in process of implementation inside the National Institute of Nuclear Research in Mexico. (Author)

  19. Fine-pitch semiconductor detector for the FOXSI mission

    CERN Document Server

    Ishikawa, Shin-nosuke; Tajima, Hiroyasu; Tanaka, Takaaki; Watanabe, Shin; Odaka, Hirokazu; Fukuyama, Taro; Kokubun, Motohide; Takahashi, Tadayuki; Terada, Yukikatsu; Krucker, Sam; Christe, Steven; McBride, Steve; Glesener, Lindsay

    2015-01-01

    The Focusing Optics X-ray Solar Imager (FOXSI) is a NASA sounding rocket mission which will study particle acceleration and coronal heating on the Sun through high sensitivity observations in the hard X-ray energy band (5-15 keV). Combining high-resolution focusing X-ray optics and fine-pitch imaging sensors, FOXSI will achieve superior sensitivity; two orders of magnitude better than that of the RHESSI satellite. As the focal plane detector, a Double-sided Si Strip Detector (DSSD) with a front-end ASIC (Application Specific Integrated Circuit) will fulfill the scientific requirements of spatial and energy resolution, low energy threshold and time resolution. We have designed and fabricated a DSSD with a thickness of 500 {\\mu}m and a dimension of 9.6 mm x 9.6 mm, containing 128 strips with a pitch of 75 {\\mu}m, which corresponds to 8 arcsec at the focal length of 2 m. We also developed a low-noise ASIC specified to FOXSI. The detector was successfully operated in the laboratory at a temperature of -20 C and w...

  20. Monte Carlo simulations of the particle transport in semiconductor detectors of fast neutrons

    International Nuclear Information System (INIS)

    Several Monte Carlo all-particle transport codes are under active development around the world. In this paper we focused on the capabilities of the MCNPX code (Monte Carlo N-Particle eXtended) to follow the particle transport in semiconductor detector of fast neutrons. Semiconductor detector based on semi-insulating GaAs was the object of our investigation. As converter material capable to produce charged particles from the (n, p) interaction, a high-density polyethylene (HDPE) was employed. As the source of fast neutrons, the 239Pu–Be neutron source was used in the model. The simulations were performed using the MCNPX code which makes possible to track not only neutrons but also recoiled protons at all interesting energies. Hence, the MCNPX code enables seamless particle transport and no other computer program is needed to process the particle transport. The determination of the optimal thickness of the conversion layer and the minimum thickness of the active region of semiconductor detector as well as the energy spectra simulation were the principal goals of the computer modeling. Theoretical detector responses showed that the best detection efficiency can be achieved for 500 μm thick HDPE converter layer. The minimum detector active region thickness has been estimated to be about 400 μm. -- Highlights: ► Application of the MCNPX code for fast neutron detector design is demonstrated. ► Simulations of the particle transport through conversion film of HDPE are presented. ► Simulations of the particle transport through detector active region are presented. ► The optimal thickness of the HDPE conversion film has been calculated. ► Detection efficiency of 0.135% was reached for 500 μm thick HDPE conversion film

  1. A spectrometer using semi-conductor detectors; study and applications (1963)

    International Nuclear Information System (INIS)

    The low average energy, 2.5 to 3.5 eV, required to produce one hole-electron pair in a semiconductor allows an accurate measurement of the energy of the ionizing particles. A high resolution spectrometer has been built using semiconductor detectors. The limit of resolution, due to electronics associated to the detector, to the detector itself and to the source of particles is studied here. The present practical limit of resolution of the spectrometer is 1700 elementary electric charges (full width at half maximum of a ray of a spectrum) or 6 keV in terms of energy lost by a particle in a silicon detector. The physical resolution usually obtained is 20 keV (0.33 per cent) with α particles of the 212Bi (6.087 MeV). It depends a lot of the kind of detector used. Some results, concerning the background of the detectors and limit of measurements for low energies are given. Various applications are presented: spectrometry β, spectrometry γ and X, spectrometry of mixtures of α radioactive elements, collection of α spectra. (author)

  2. Progress report, Semiconductor Detector Group, April 1, 1974 to March 31, 1975

    International Nuclear Information System (INIS)

    This report is an annual progress report of Semiconductor Detector Group and describes the work made during one year between April 1, 1974 and March 31, 1975. The related themes to the Group were ''semiconductor detector development and application'' and ''fuel failure detector sodium in-pile loop test (III) ( a contract study between Power Reactor and Nuclear Fuel Development Corporation and J.A.E.R.I. )''. This includes a brief description of the results obtained in the following studies; portable Ge(Li) gamma-ray spectrometer fabrication, its application to gamma-ray spectrometry in Japan Research Reactor No.3 and to in-situ measurement of environmental gamma-rays, temperature cycling test of a hyperpure germanium detector, silicon detector fabrication by N+ ion implantation, PDP-8/L program development for an ND-50/50 multichannel analyser, X-ray spectrometry of Japan Fusion Tokamak No.2 plasma using a Si(Li) detector, sodium in-pile loop test of four types of fuel failure detection systems, and various kinds of technical service. The publications and lectures made in this period are also listed. (auth.)

  3. Inter-electrode charge collection in high-purity germanium detectors with amorphous semiconductor contacts

    International Nuclear Information System (INIS)

    High-purity germanium (HPGe) radiation detectors with segmented signal readout electrodes combine excellent energy resolution with fine spatial resolution, opening exciting possibilities in radiation imaging applications. Segmenting the electrodes provides the ability to determine the positions of radiation interactions in the detector, but it also brings potential challenges that can inhibit performance. A challenge unique to segmented electrode detectors is collection of charge carriers to the gap between adjacent electrodes rather than to the electrodes themselves, which gives a deficit in the summed energy. While amorphous semiconductor electrical contacts have enabled a simplified fabrication process capable of fine electrode segmentation, the amorphous semiconductor passivation layer between electrodes is prone to inter-electrode charge collection. This article presents a study of the impact of fabrication process parameters on the energy deficit due to inter-electrode charge collection for double-sided strip detectors. Eight double-sided strip HPGe detectors were fabricated with amorphous germanium (a-Ge) and amorphous silicon (a-Si) contacts formed by sputter deposition. Each detector was evaluated for inter-electrode charge collection performance, using as a metric the deficit in the summed signal of two adjacent electrodes. It is demonstrated that both a-Ge and a-Si contacts can be produced with nearly non-existent inter-electrode charge collection when the appropriate combination of sputter gas hydrogen content and gas pressure are selected

  4. Detection of fast neutrons from shielded nuclear materials using a semiconductor alpha detector

    International Nuclear Information System (INIS)

    The response of a semiconductor alpha detector to fast (>1 MeV) neutrons was investigated by using measurements and simulations. A polyethylene converter was placed in front of the detector to register recoil protons generated by elastic collisions between neutrons and hydrogen nuclei of the converter. The developed prototype equipment was tested with shielded radiation sources. The low background of the detector and insensitivity to high-energy gamma rays above 1 MeV are advantages when the detection of neutron-emitting nuclear materials is of importance. In the case of a 252Cf neutron spectrum, the intrinsic efficiency of fast neutron detection was determined to be 2.5×10−4, whereas three-fold greater efficiency was obtained for a 241AmBe neutron spectrum. - Highlights: • We investigated the response of a semiconductor alpha detector to fast neutrons emitted by nuclear materials. • Low background and insensitivity to gamma rays are advantages of the detector operating at ambient air pressure. • A polyethylene converter placed in front of the detector increased the detection efficiency by a factor of four. • Intrinsic detection efficiency for fast neutrons from unshielded 252Cf and 241AmBe sources was 2.5×10−4 and 7.6×10−4, respectively

  5. Use of different scintillation and semiconductor detectors for rapid estimation of internal contamination of people

    International Nuclear Information System (INIS)

    In radiological emergencies, it is necessary to evaluate among other possible internal contamination of people. The main tool for this purpose is whole body counter, however , when a large group of people could be affected or when a triage is necessary, simple rapid methods are important. Semiconductor and scintillation detectors (table 1) were calibrated with the use of point sources and phantoms, representing human body .Background of each of detector was measured in different surroundings -in shielding chamber of whole body counter, in the room and in partially shielded container of mobile whole body counter. Generally, all investigated detectors are suitable for rapid whole body counting. When contaminant is just one radionuclide, scintillation detectors could be used. For complicated mixture of radionuclides, either use of semiconductor detector is necessary or at least, preliminary determination of mixture of radionuclides has to be performed. New LaBr detector is suitable from the point of view of better resolution, however, it has to have in mind its higher intrinsic background. (authors)

  6. Radiation damage measurements in room-temperature semiconductor radiation detectors

    CERN Document Server

    Franks, L A; Olsen, R W; Walsh, D S; Vizkelethy, G; Trombka, J I; Doyle, B L; James, R B

    1999-01-01

    The literature of radiation damage measurements on cadmium zinc telluride (CZT), cadmium telluride (CT), and mercuric iodide (HgI sub 2) is reviewed and in the case of CZT supplemented by new alpha particle data. CZT strip detectors exposed to intermediate energy (1.3 MeV) proton fluences exhibit increased interstrip leakage after 10 sup 1 sup 0 p/cm sup 2 and significant bulk leakage after 10 sup 1 sup 2 p/cm sup 2. CZT exposed to 200 MeV protons shows a two-fold loss in energy resolution after a fluence of 5x10 sup 9 p/cm sup 2 in thick (3 mm) planar devices but little effect in 2 mm devices. No energy resolution effects were noted from a moderated fission spectrum of neutrons after fluences up to 10 sup 1 sup 0 n/cm sup 2 , although activation was evident. Exposures of CZT to 5 MeV alpha particles at fluences up to 1.5x10 sup 1 sup 0 alpha/cm sup 2 produced a near linear decrease in peak position with fluence and increases in FWHM beginning at about 7.5x10 sup 9 alpha/cm sup 2. CT detectors show resolution...

  7. Extensive testing of Schottky CdTe detectors for the ECLAIRs X-Gamma-ray Camera on board the SVOM mission

    CERN Document Server

    Nadege, Remoue; Olivier, Godet; Pierre, Mandrou

    2010-01-01

    We report on an on-going test campaign of more than 5000 Schottky CdTe detectors (4x4x1 mm^3), over a sample of twelve thousands, provided by Acrorad Co., Ltd (Japan). 6400 of these detectors will be used to build the detection plane of the ECLAIRs camera on the Chinese-French gamma-ray burst mission SVOM. These tests are mandatory to fulfill the prime requirement of ECLAIRs to detect gamma-ray burst photons down to 4 keV. The detectors will be operated at -20C under a reverse bias of 600 V. We found that 78% of the detectors already tested could be considered for the flight model. We measured a mean energy resolution of 1.8 keV at 59.6 keV. We investigated the polarization effect first at room temperature and low bias voltage for faster analysis. We found that the spectroscopic degradation in quantum efficiency, gain and energy resolution, starts as soon as the bias is turned on: first slowly and then dramatically after a time t_p which depends on the temperature and the voltage value. Preliminary tests unde...

  8. X-ray measurement with Pin type semiconductor detectors; Medicion de rayos X con detectores de semiconductor tipo PIN

    Energy Technology Data Exchange (ETDEWEB)

    Ramirez J, F.J. [Instituto Nacional de Investigaciones Nucleares, Departamento de Electronica, C.P. 52045 Salazar, Estado de Mexico (Mexico)

    2000-07-01

    Here are presented the experimental results of the applications of Pin type radiation detectors developed in a National Institute of Nuclear Research (ININ) project, in the measurement of low energy gamma and X-rays. The applications were oriented mainly toward the Medical Physics area. It is planned other applications which are in process of implementation inside the National Institute of Nuclear Research in Mexico. (Author)

  9. Investigation about semiconductor gamma ray detector - Evaluation of Ge(Li) detectors life expectation

    International Nuclear Information System (INIS)

    A list of germanium lithium gamma ray detectors has been drawn up by a working group after investigations in various laboratories. Authors analyse the historical account of each detector and try to give an answer about some questions as: - detectors life expectation, - deficiencies and death reasons, - influence of detector type and volume. Differents parameters are also collected by the working group for future works (standard geometry, low level measurements, etc.). In the list, the characteristics of 228 detectors, collected between january 1965 and december 1977 are put together. The principal conclusions of the authors are: - with a probability of 95%, half of the detectors is dead before 6.1 years, - the average age of dead population (33% of detectors) is 3.9 years, - resolution and efficiency evolution are good indicators of possible deficiency, - the fiability of vertical cryostat is better than the other systems

  10. The simulation of charge sharing in semiconductor X-ray pixel detectors

    CERN Document Server

    Mathieson, K; O'Shea, V; Passmore, M S; Rahman, M; Smith, K M; Watt, J; Whitehill, C

    2002-01-01

    Two simulation packages were used to model the sharing of charge, due to the scattering and diffusion of carriers, between adjacent pixel elements in semiconductors X-ray detectors. The X-ray interaction and the consequent multiple scattering was modelled with the aid of the Monte Carlo package, MCNP. The resultant deposited charge distribution was then used to create the charge cloud profile in the finite element semiconductor simulation code MEDICI. The analysis of the current pulses induced on pixel electrodes for varying photon energies was performed for a GaAs pixel detector. For a pixel pitch of 25 mu m, the charge lost to a neighbouring pixel was observed to be constant, at 0.6%, through the energies simulated. Ultimately, a fundamental limit on the pixel element size for imaging and spectroscopic devices may be set due to these key physical principles.

  11. Prototype gamma-camera system with CdZnTe semiconductor detectors

    International Nuclear Information System (INIS)

    The CdZnTe semiconductor detector, which works at room temperature, may lead to the development of next-generation gamma-camera systems due to its high spatial resolution and high energy resolution. We fabricated a prototype gamma-camera system with CdZnTe detectors to evaluate the feasibility of such a semiconductor gamma-camera. An energy resolution of 7.35% full width half maximum (FWHM) (at 140 keV) and an intrinsic spatial resolution of 1.8 mm FWHM were achieved. Single photon emission computed tomography (SPECT) images acquired using this gamma-camera system showed that the system can resolve hot and cold rods with a diameter of 3 mm. (author)

  12. Mercuric iodide (HgI/sub 2/) semiconductor devices as charged particle detectors

    Energy Technology Data Exchange (ETDEWEB)

    Beccetti, F.D.; Raymond, R.S.; Ristinen, R.A. (Colorado Univ., Boulder (USA). Nuclear Physics Lab.); Schnepple, W.F.; Ortale, C. (EG and G, Inc., Goleta, CA (USA). Santa Barbara Div.)

    1983-07-15

    The properties of HgI/sub 2/ semiconductor devices as charged particle detectors have been investigated. Nearly linear energy response with fwhm resolution of 5-15% is observed for sup(1.2)H and sup(3.4)He ions, E < 40 MeV. Fast proton damage is observed for > 10/sup 10/ protons/cm/sup 2/. However, based on measurements with the HgI/sub 2/ detectors, little fast neutron damage is apparent at fluences up to 10/sup 15/ neutrons/cm/sup 2/. This suggests considerably greater resistance to radiation damage than is observed for Si and other solid state devices.

  13. Mercuric iodide (HgI/sub 2/) semiconductor devices as charged-particle detectors

    Energy Technology Data Exchange (ETDEWEB)

    Becchetti, F.D.; Raymond, R.S.; Ristinen, R.A.; Schnepple, W.F.; Ortale, C.

    1981-01-01

    The properties of HgI/sub 2/ semiconductor devices as charged particle detectors have been investigated. Nearly linear energy response with FWHM resolution of 5 to 15% is observed for /sup 1/ /sup 2/H and /sup 3/ /sup 4/He ions, E < 40 MeV. Fast proton damage is observed for > 10/sup 10/ protons/cm/sup 2/. However, based on measurements with two HgI/sub 2/ detectors, little fast neutron damage is apparent at fluences up to 10/sup 15/ neutrons/cm/sup 2/. This suggests considerably greater resistance to radiation damage than is observed for Si and other solid state devices.

  14. Mercuric iodide (HgI2) semiconductor devices as charged particle detectors

    International Nuclear Information System (INIS)

    The properties of HgI2 semiconductor devices as charged particle detectors have been investigated. Nearly linear energy response with fwhm resolution of 5-15% is observed for sup(1.2)H and sup(3.4)He ions, E 1010 protons/cm2. However, based on measurements with the HgI2 detectors, little fast neutron damage is apparent at fluences up to 1015 neutrons/cm2. This suggests considerably greater resistance to radiation damage than is observed for Si and other solid state devices. (orig.)

  15. Mercuric iodide (HgI 2) semiconductor devices as charged particle detectors

    Science.gov (United States)

    Becchetti, F. D.; Raymond, R. S.; Ristinen, R. A.; Schnepple, W. F.; Ortale, C.

    1983-07-01

    The properties of HgI 2 semiconductor devices as charged particle detectors have been investigated. Nearly linear energy response with fwhm resolution of 5-15% is observed for 1,2H and 3,4He ions, E < 40 MeV. Fast proton damage is observed for 10 10 protons/cm 2. However, based on measurements with two HgI 2 detectors, little fast neutron damage is apparent at fluences up to 10 15 neutrons/cm 2. This suggests considerably greater resistance to radiation damage than is observed for Si and other solid state devices.

  16. Mercuric iodide (HgI2) semiconductor devices as charged-particle detectors

    International Nuclear Information System (INIS)

    The properties of HgI2 semiconductor devices as charged particle detectors have been investigated. Nearly linear energy response with FWHM resolution of 5 to 15% is observed for 12H and 34He ions, E 1010 protons/cm2. However, based on measurements with two HgI2 detectors, little fast neutron damage is apparent at fluences up to 1015 neutrons/cm2. This suggests considerably greater resistance to radiation damage than is observed for Si and other solid state devices

  17. Digital approach to high-resolution pulse processing for semiconductor detectors

    International Nuclear Information System (INIS)

    A new design philosophy for processing signals produced by high resolution, large volume semiconductor detectors is described. These detectors, to be used in the next generation of spectrometer arrays for nuclear research (i.e. EUROBALL, etc.), present a set of problems like resolution degradation due to charge trapping and ballistic defect effects, low resolution at a high count rate, poor long term stability, etc. To solve these problems, a new design approach has been developed, including reconstruction of the event charge, providing a pure triangular residual function, and suppressing low frequency noise. 5 refs., 4 figs

  18. Counting losses from pulsed optical-feedback preamplifiers used with semiconductor detectors

    International Nuclear Information System (INIS)

    Problems encountered with semiconductor detectors that are coupled to pulsed optical-feedback preamplifiers have been investigated theoretically. The resetting of the preamplifier causes a deadtime followed by a second deadtime during which counting of pulses in the multichannel analyzer is inhibited. Counts are lost also by the resetting itself, if this is not prevented by special electronics. In order to account for pile-up and deadtime losses the pulse-generator method is frequently applied. It is shown that this method is inadequate for the problem and that the counting losses depend on the detector- and generator-pulse amplitudes. (author)

  19. Counting losses from pulsed optical-feedback preamplifiers used with semiconductor detectors

    Energy Technology Data Exchange (ETDEWEB)

    Funck, E. (Physikalisch-Technische Bundesanstalt, Braunschweig (Germany, F.R.))

    1983-08-01

    Problems encountered with semiconductor detectors that are coupled to pulsed optical-feedback preamplifiers have been investigated theoretically. The resetting of the preamplifier causes a deadtime followed by a second deadtime during which counting of pulses in the multichannel analyzer is inhibited. Counts are lost also by the resetting itself, if this is not prevented by special electronics. In order to account for pile-up and deadtime losses the pulse-generator method is frequently applied. It is shown that this method is inadequate for the problem and that the counting losses depend on the detector- and generator-pulse amplitudes.

  20. Evaluation of a Fabricated Charge Sensitive Amplifier for a Semiconductor Radiation Detector

    International Nuclear Information System (INIS)

    A CSA(Charge Sensitive Amplifier) was designed and fabricated for application in a radiation detection system based on a semiconductor detector such as Si, SiC, CdZnTe and etc.. A fabricated hybrid.type CSA was evaluated by comparison with a commercially available CSA. A comparison was performed by using calculation of ENC (Equivalent Noise Charge) and by using energy resolutions of fabricated radiation detectors based on Si. In energy resolution comparison, a fabricated CSA showed almost the same performance compared with a commercial one. In this study, feasibility of a fabricated CSA was discussed

  1. Effects of nuclear fusion produced neutrons on silicon semiconductor plasma X-ray detectors

    CERN Document Server

    Kohagura, J; Hirata, M; Numakura, T; Minami, R; Watanabe, H; Sasuga, T; Nishizawa, Y; Yoshida, M; Nagashima, S; Tamano, T; Yatsu, K; Miyoshi, S; Hirano, K; Maezawa, H

    2002-01-01

    The effects of nuclear fusion produced neutrons on the X-ray energy responses of semiconductor detectors are characterized. The degradation of the response of position-sensitive X-ray tomography detectors in the Joint European Torus (JET) tokamak is found after neutron exposure produced by deuterium-deuterium and deuterium-tritium plasma fusion experiments. For the purpose of further detailed characterization of the neutron degradation effects, an azimuthally varying-field (AVF) cyclotron accelerator is employed using well-calibrated neutron fluence. These neutron effects on the detector responses are characterized using synchrotron radiation from a 2.5 GeV positron storage ring at the Photon Factory (KEK). The effects of neutrons on X-ray sensitive semiconductor depletion thicknesses are also investigated using an impedance analyser. Novel findings of (i) the dependence of the response degradation on X-ray energies as well as (ii) the recovery of the degraded detector response due to the detector bias applic...

  2. Development of a novel 2D position-sensitive semiconductor detector concept

    OpenAIRE

    Bassignana, D.; Fernández, M; Jaramillo, R.; Lozano Fantoba, Manuel; Muñoz Sánchez, F. J.; Pellegrini, Giulio; Quirion, D; Vila, Iván

    2011-01-01

    A novel 2D position-sensitive semiconductor detector concept has been developed employing resistive electrodes in a single-sided silicon microstrip sensor. The resistive charge division method has been implemented reading out each strip at both ends, in order to get the second coordinate of an ionizing event along the strips length. Two generations of prototypes, with different layout, have been produced and characterized using a pulsed near infra-red laser. The feasibility of the resistive c...

  3. An updated system of electronic modules for X-ray spectrometers with cooled semiconductor detectors

    International Nuclear Information System (INIS)

    An updated system of program-controlled analog and analog-to-digital modules for X-ray spectrometers with semiconductor detectors is reported. Ways to increase the count rate capacity of pulse-drain feedback charge-sensitive preamplifiers to 106 cps for EX=5.9 keV are considered in detail. A new analog processor model AP-007 incorporating Kandiah's cusp-shaper is described. Some problems of further improvements in the modular system are discussed. (orig.)

  4. The measurement of the radioactive aerosol diameter by position sensitive semiconductor detectors, 1

    International Nuclear Information System (INIS)

    The measurement of the diameter of radioactive aerosol, in particular plutonium aerosol, is very important for the internal dose estimation. Determination of the diameter of radioactive aerosol is performed by using position sensitive semiconductor detector (PSD). The filter paper with the radioactive aerosols is contacted to the PSD which is connected to the data processor so that the diameter of the aerosol is calculated from the measured radioactivity. This investigation was performed in cooperation with Rikkyo University. (author)

  5. Assessment of present and future large-scale semiconductor detector systems

    International Nuclear Information System (INIS)

    The performance of large-scale semiconductor detector systems is assessed with respect to their theoretical potential and to the practical limitations imposed by processing techniques, readout electronics and radiation damage. In addition to devices which detect reaction products directly, the analysis includes photodetectors for scintillator arrays. Beyond present technology we also examine currently evolving structures and techniques which show potential for producing practical devices in the foreseeable future

  6. 2010 IEEE Nuclear Science Symposium, Medical Imaging Conference, and Room Temperature Semiconductor Detectors Workshop

    Science.gov (United States)

    The Nuclear Science Symposium (NSS) offers an outstanding opportunity for scientists and engineers interested or actively working in the fields of nuclear science, radiation instrumentation, software and their applications, to meet and discuss with colleagues from around the world. The program emphasizes the latest developments in technology and instrumentation and their implementation in experiments for space sciences, accelerators, other radiation environments, and homeland security. The Medical Imaging Conference (MIC) is the foremost international scientific meeting on the physics, engineering and mathematical aspects of nuclear medicine based imaging. As the field develops, multi-modality approaches are becoming more and more important. The content of the MIC reflects this, with a growing emphasis on the methodologies of X-ray, optical and MR imaging as they relate to nuclear imaging techniques. In addition, specialized topics will be addressed in the Short Courses and Workshops programs. The Workshop on Room-Temperature Semiconductor Detectors (RTSD) represents the largest forum of scientists and engineers developing new semiconductor radiation detectors and imaging arrays. Room-temperature solid-state radiation detectors for X-ray, gamma-ray, and neutron radiation are finding increasing applications in such diverse fields as medicine, homeland security, astrophysics and environmental remediation. The objective of this workshop is to provide a forum for discussion of the state of the art of material development for semiconductor, scintillator, and organic materials for detection, materials characterization, device fabrication and technology, electronics and applications.

  7. Comparison of NaI(Tl), CdTe, and HgI2 surgical probes: physical characterization.

    Science.gov (United States)

    Barber, H B; Barrett, H H; Hickernell, T S; Kwo, D P; Woolfenden, J M; Entine, G; Ortale Baccash, C

    1991-01-01

    The physical properties of three surgical probes containing different radiation detectors are compared: a NaI(Tl) scintillator with a flexible, fiber-optic light guide, and two semiconductor detectors that operate at room temperature, CdTe and HgI2. Also compared are spectra, energy resolutions, and counting efficiencies measured at a variety of gamma-ray energies between 30 and 1000 keV. The energy resolution of the NaI probe is substantially poorer than that of either semiconductor probe due in part to light losses in coupling the scintillator to the fiber optics. The semiconductor probes have complex spectral response due to charge-carrier trapping and K x-ray escape, and not all photoelectric interactions in these detectors contribute to the useful part of the photopeak. Above 120 keV the counting efficiency for the NaI probe is an order of magnitude higher than for the CdTe and HgI2 probes. Both energy resolution and counting efficiency are slightly better for the HgI2 probe than for the CdTe probe. PMID:1870478

  8. Materials for infrared detectors and sources; Proceedings of the Symposium, Boston, MA, Dec. 1-5, 1986

    Science.gov (United States)

    Farrow, R. F. C.; Schetzina, J. F.; Cheung, J. T.

    The present conference discusses epitaxial semiconductor structures for the IR, materials requirements for IR detectors and imagers, HgCdTe for LWIR imagers and heterojunction devices, epitaxial IV-VI semiconductor films, the growth of bulk IR sensor-material crystals, structure-property relationships in semiconductor alloys, high quality growth of CdTe by the gradient-freeze method, the electronic properties and vacancy-formation energies of HgCdTe vs HgZnTe, and the structure of hydrogenated amorphous carbon IR coatings. Also discussed are tailored microstructures for IR detection, the X-ray characterization of IR materials, subsurface microlattice strain mapping, deep-level defects in CdTe, the MBE HgTe growth process, interdiffused multilayer processing in alloy growth, HgTe-CdTe superlattices grown by photo-MOCVD, InSb in IR detector applications, and CdTe films grown on InSb substrates by organometallic epitaxy.

  9. Materials for infrared detectors and sources; Proceedings of the Symposium, Boston, MA, Dec. 1-5, 1986

    Energy Technology Data Exchange (ETDEWEB)

    Farrow, R.F.C.; Schetzina, J.F.; Cheung, J.T.

    1987-01-01

    The present conference discusses epitaxial semiconductor structures for the IR, materials requirements for IR detectors and imagers, HgCdTe for LWIR imagers and heterojunction devices, epitaxial IV-VI semiconductor films, the growth of bulk IR sensor-material crystals, structure-property relationships in semiconductor alloys, high quality growth of CdTe by the gradient-freeze method, the electronic properties and vacancy-formation energies of HgCdTe vs HgZnTe, and the structure of hydrogenated amorphous carbon IR coatings. Also discussed are tailored microstructures for IR detection, the X-ray characterization of IR materials, subsurface microlattice strain mapping, deep-level defects in CdTe, the MBE HgTe growth process, interdiffused multilayer processing in alloy growth, HgTe-CdTe superlattices grown by photo-MOCVD, InSb in IR detector applications, and CdTe films grown on InSb substrates by organometallic epitaxy.

  10. Current applications of semiconductor x-ray detectors in chemical analysis

    International Nuclear Information System (INIS)

    In the last few years, semiconductor detectors have been used as X-ray detectors with great success, and the routine rapid accumulation of X-ray spectra is now possible. This review surveys the historical development of the detectors, the utilisation, and relative merits of various means of exciting the X-radiation from the elements in the sample, and compares the technique with other methods claiming to offer the capability of simultaneous multi-element analysis. It is concluded that it is of average sensitivity, but offers some advantages from its non-destructive nature, and in some cases its ability to offer information about the spatial distribution of elements in a sample. Other types of analysis may also be possible simultaneously. Sample preparation techniques are reviewed, especially techniques of manufacturing thin samples. An appendix contains details of the very wide variety of samples which have been analysed. More than 350 references are included. (auth.)

  11. Detection of fast neutrons from shielded nuclear materials using a semiconductor alpha detector.

    Science.gov (United States)

    Pöllänen, R; Siiskonen, T

    2014-08-01

    The response of a semiconductor alpha detector to fast (>1 MeV) neutrons was investigated by using measurements and simulations. A polyethylene converter was placed in front of the detector to register recoil protons generated by elastic collisions between neutrons and hydrogen nuclei of the converter. The developed prototype equipment was tested with shielded radiation sources. The low background of the detector and insensitivity to high-energy gamma rays above 1 MeV are advantages when the detection of neutron-emitting nuclear materials is of importance. In the case of a (252)Cf neutron spectrum, the intrinsic efficiency of fast neutron detection was determined to be 2.5×10(-4), whereas three-fold greater efficiency was obtained for a (241)AmBe neutron spectrum. PMID:24792122

  12. Provisional shielding for laboratory measurements of low level activities with semiconductor detectors

    International Nuclear Information System (INIS)

    The application of semiconductor spectrometry in low level counting requires the use of detector shielding to weaken the effect of ambient sources of ionizing radiation. The design is described of provisional shields of lead bricks for three different types of high-purity Ge detectors by Canberra. In the configuration of six polyethylene vessels around the detector with a total sample volume of 1200 ml, minimal detectable activities were determined of selected radionuclides. The experiment showed that the determination of minimal detectable activity in this configuration shows sufficient values for determining the content of natural and artificial radionuclides for monitoring samples from the environment of nuclear power plants. (Z.M.). 5 figs., 3 tabs., 2 refs

  13. CdTe quantum dots for an application in the life sciences

    International Nuclear Information System (INIS)

    This report highlights the results of the preparation of semiconductor CdTe quantum dots (QDs) in the aqueous phase. The small size of a few nm and a very high luminescence quantum yield exceeding 60% of these materials make them promisingly applicable to bio-medicine labeling. Their strong, two-photon excitation luminescence is also a good characteristic for biolabeling without interference with the cell fluorescence. The primary results for the pH-sensitive CdTe QDs are presented in that fluorescence of CdTe QDs was used as a proton sensor to detect proton flux driven by adenosine triphosphate (ATP) synthesis in chromatophores. In other words, these QDs could work as pH-sensitive detectors. Therefore, the system of CdTe QDs on chromatophores prepared from the cells of Rhodospirillum rubrum and the antibodies against the beta-subunit of F0F1–ATPase could be a sensitive detector for the avian influenza virus subtype A/H5N1

  14. Radiation hardness of semiconductor avalanche detectors for calorimeters in future HEP experiments

    Science.gov (United States)

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

    2016-02-01

    During the last years, semiconductor avalanche detectors are being widely used as the replacement of classical PMTs in calorimeters for many HEP experiments. In this report, basic selection criteria for replacement of PMTs by solid state devices and specific problems in the investigation of detectors radiation hardness are discussed. The design and performance of the hadron calorimeters developed for the future high energy nuclear physics experiments at FAIR, NICA, and CERN are discussed. The Projectile Spectator Detector (PSD) for the CBM experiment at the future FAIR facility, the Forward Calorimeter for the NA61 experiment at CERN and the Multi Purpose Detector at the future NICA facility are reviewed. Moreover, new methods of data analysis and results interpretation for radiation experiments are described. Specific problems of development of detectors control systems and possibilities of reliability improvement of multi-channel detectors systems are shortly overviewed. All experimental material is based on the investigation of SiPM and MPPC at the neutron source in NPI Rez.

  15. Characterization of CdTe Sensors with Schottky Contacts Coupled to Charge-Integrating Pixel Array Detectors for X-Ray Science

    CERN Document Server

    Becker, Julian; Shanks, Katherine S; Philipp, Hugh T; Weiss, Joel T; Purohit, Prafull; Chamberlain, Darol; Ruff, Jacob P C; Gruner, Sol M

    2016-01-01

    Pixel Array Detectors (PADs) consist of an x-ray sensor layer bonded pixel-by-pixel to an underlying readout chip. This approach allows both the sensor and the custom pixel electronics to be tailored independently to best match the x-ray imaging requirements. Here we present characterizations of CdTe sensors hybridized with two different charge-integrating readout chips, the Keck PAD and the Mixed-Mode PAD (MM-PAD), both developed previously in our laboratory. The charge-integrating architecture of each of these PADs extends the instantaneous counting rate by many orders of magnitude beyond that obtainable with photon counting architectures. The Keck PAD chip consists of rapid, 8-frame, in-pixel storage elements with framing periods $<$150 ns. The second detector, the MM-PAD, has an extended dynamic range by utilizing an in-pixel overflow counter coupled with charge removal circuitry activated at each overflow. This allows the recording of signals from the single-photon level to tens of millions of x-rays/...

  16. Toward VIP-PIX: A Low Noise Readout ASIC for Pixelated CdTe Gamma-Ray Detectors for Use in the Next Generation of PET Scanners.

    Science.gov (United States)

    Macias-Montero, Jose-Gabriel; Sarraj, Maher; Chmeissani, Mokhtar; Puigdengoles, Carles; Lorenzo, Gianluca De; Martínez, Ricardo

    2013-08-01

    VIP-PIX will be a low noise and low power pixel readout electronics with digital output for pixelated Cadmium Telluride (CdTe) detectors. The proposed pixel will be part of a 2D pixel-array detector for various types of nuclear medicine imaging devices such as positron-emission tomography (PET) scanners, Compton gamma cameras, and positron-emission mammography (PEM) scanners. Each pixel will include a SAR ADC that provides the energy deposited with 10-bit resolution. Simultaneously, the self-triggered pixel which will be connected to a global time-to-digital converter (TDC) with 1 ns resolution will provide the event's time stamp. The analog part of the readout chain and the ADC have been fabricated with TSMC 0.25 μm mixed-signal CMOS technology and characterized with an external test pulse. The power consumption of these parts is 200 μW from a 2.5 V supply. It offers 4 switchable gains from ±10 mV/fC to ±40 mV/fC and an input charge dynamic range of up to ±70 fC for the minimum gain for both polarities. Based on noise measurements, the expected equivalent noise charge (ENC) is 65 e(-) RMS at room temperature. PMID:24187382

  17. Dual radioisotopes simultaneous SPECT of 99mTc-tetrofosmin and 123I-BMIPP using a semiconductor detector

    OpenAIRE

    Yasuyuki Takahashi; Masao Miyagawa; Yoshiko Nishiyama; Naoto Kawaguchi; Hayato Ishimura; Teruhito Mochizuki

    2015-01-01

    Objective(s): The energy resolution of a cadmium-zinc-telluride (CZT) solid-state semiconductor detector is about 5%, and is superior to the resolution of the conventional Anger type detector which is 10%. Also, the window width of the high-energy part and of the low-energy part of a photo peak window can be changed separately. In this study, we used a semiconductor detector and examined the effects of changing energy window widths for 99mTc and 123 I simultaneous SPECT. ...

  18. Response function of semiconductor detectors, Ge and Si(Li); Funcao resposta de detectores semicondutores, Ge e Si(Li)

    Energy Technology Data Exchange (ETDEWEB)

    Zevallos Chavez, Juan Yury

    2003-07-01

    The Response Function (RF) for Ge and Si(Li) semiconductor detectors was obtained. The RF was calculated for five detectors, four Hp Ge with active volumes of 89 cm{sup 3} , 50 cm{sup 3} , 8 cm{sup 3} and 5 cm{sup 3}, and one Si(Li) with 0.143 cm{sup 3} of active volume. The interval of energy studied ranged from 6 keV up to 1.5 MeV. Two kinds of studies were done in this work. The first one was the RF dependence with the detection geometry. Here the calculation of the RF for a geometry named as simple and an extrapolation of that RF, were both done. The extrapolation process analyzed both, spectra obtained with a shielding geometry and spectra where the source-detector distance was modified. The second one was the RF dependence with the detection electronics. This study was done varying the shaping time of the pulse in the detection electronics. The purpose was to verify the effect of the ballistic deficit in the resolution of the detector. This effect was not observed. The RF components that describe the region of the total absorption of the energy of the incident photons, and the partial absorption of this energy, were both treated. In particular, empirical functions were proposed for the treatment of both, the multiple scattering originated in the detector (crystal), and the photon scattering originated in materials of the neighborhood of the crystal. Another study involving Monte Carlo simulations was also done in order to comprehend the photon scattering structures produced in an iron shield. A deconvolution method is suggested, for spectra related to scattered radiation in order to assess the dose delivered to the scatterer. (author)

  19. Design of a hybrid gas proportional counter with CdTe guard counters for 14C dating system

    International Nuclear Information System (INIS)

    Nowadays uniform, low-cost and large-size compound semiconductor detectors are available up to several square centimeters. We are trying to combine this technology with conventional gas detectors to upgrade an anticoincidence type proportional counter, Oeschger-type thin wall counter of 2.2 l, used for a 14C dating facility at the University of Tokyo. In order to increase the ratio of the signal to the background for smaller quantity of samples less than 1 g, an effective approach is to minimize the detector volume at higher gas pressure. However, the anticoincidence function suffers from such a small volume. Therefore we designed a new active wall gas counter of 0.13 l counting volume using CdTe compound semiconductor detectors as the wall of the gas proportional counter to perform anticoincidence. Simulation study showed that at noise thresholds less than 70 keV, the wall counters can reject above 99.8% of events arising from outer gamma rays. Measured noise levels of CdTe detectors were smaller than 24 keV which is low enough for 99.8% anticoincidence efficiency. The experiment showed an anticoincidence efficiency for outer gamma rays from 70% to 80%, similar to that of the old 14C counter. The lost anticoincidence efficiency results from the area of 21.74% which was not covered with CdTe due to two holes for the path of the center anode wire and slots between every two sides of CdTe detectors

  20. Design of a hybrid gas proportional counter with CdTe guard counters for {sup 14}C dating system

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, L. E-mail: lan@sophie.q.t.u-tokyo.ac.jp; Takahashi, H.; Hinamoto, N.; Nakazawa, M.; Yoshida, K

    2002-02-01

    Nowadays uniform, low-cost and large-size compound semiconductor detectors are available up to several square centimeters. We are trying to combine this technology with conventional gas detectors to upgrade an anticoincidence type proportional counter, Oeschger-type thin wall counter of 2.2 l, used for a {sup 14}C dating facility at the University of Tokyo. In order to increase the ratio of the signal to the background for smaller quantity of samples less than 1 g, an effective approach is to minimize the detector volume at higher gas pressure. However, the anticoincidence function suffers from such a small volume. Therefore we designed a new active wall gas counter of 0.13 l counting volume using CdTe compound semiconductor detectors as the wall of the gas proportional counter to perform anticoincidence. Simulation study showed that at noise thresholds less than 70 keV, the wall counters can reject above 99.8% of events arising from outer gamma rays. Measured noise levels of CdTe detectors were smaller than 24 keV which is low enough for 99.8% anticoincidence efficiency. The experiment showed an anticoincidence efficiency for outer gamma rays from 70% to 80%, similar to that of the old {sup 14}C counter. The lost anticoincidence efficiency results from the area of 21.74% which was not covered with CdTe due to two holes for the path of the center anode wire and slots between every two sides of CdTe detectors.

  1. CdZnTe semiconductor parallel strip Frisch grid radiation detectors

    International Nuclear Information System (INIS)

    CdZnTe wide band gap compound semiconducting material offers promise as a room temperature operated gamma ray spectrometer. Position-dependent free charge carrier losses during transport can prevent efficient charge carrier extraction from semiconductor detectors and severely reduce energy resolution. Hole trapping losses in CdZnTe radiation detectors are far worse than electron trapping losses and resolution degradation in CdZnTe detectors results primarily from severe hole trapping during transport. Coplanar radiation detectors improved energy resolution by sensing the induced charge primarily from the motion of electrons. Demonstrated is an alternative approach to single free charge carrier sensing, in which a parallel strip Frisch grid is fabricated on either side of a parallelepiped block. The detectors are three terminal devices, but require only one preamplifier for the output signal. The prototype devices demonstrate a considerable increase in energy resolution when operated in the true Frisch grid mode rather than the planar mode, with a demonstrated room temperature energy resolution for 662 keV gamma rays of 5.91 % at FWHM for a 10 mm x 2 mm x 10 mm device. Presently, high surface leakage currents prevent large voltages from being applied to the devices, which ultimately reduces their maximum achievable energy resolution. Further improvements are expected with the realization of reduced surface leakage currents

  2. Determination and stabilization of the altitude of an aircraft in space using semi-conductor detectors

    International Nuclear Information System (INIS)

    The device studied in this report can be used as altimeter or as altitude stabilizer (B.F. number PV 100-107, March 23, 1967). It includes essentially a 'surface barrier' semiconductor detector which counts alpha particles of a radioactive source. Two sources are used corresponding to two possible utilizations of the device. This report describes experiences made in laboratory which comprises electronic tests and a physic study. Systematic analysis of experimental errors is made comparatively with aneroid altimeters. An industrial device project is given. (author)

  3. The detector control system for the ATLAS semiconductor tracker assembly phase

    CERN Document Server

    Sfyrla, Anna; Basiladze, Sergei G; Brenner, Richard; Chamizo-Llatas, Maria; Codispoti, Giuseppe; Ferrari, Pamela; Mikulec, Bettina; Phillips, Peter; Sandaker, Heidi; Stanecka, Ewa

    2005-01-01

    The ATLAS Semiconductor Tracker (SCT) consists of 4088 silicon microstrip modules, with a total of 6.3 million readout channels. These are arranged into 4 concentric barrel layers and 2 endcaps of 9 disks each. The coherent and safe operation of the SCT during commissioning and subsequent operation is an essential task of the Detector Control System (DCS). The main building blocks of the SCT DCS, the cooling system, the power supplies and the environmental system, are described. First results from DCS testing are presented.

  4. Perfluorocarbons and their use in Cooling Systems for Semiconductor Particle Detectors

    CERN Document Server

    Vacek, V; Ilie, S; Lindsay, S

    2000-01-01

    We report on the development of evaporative fluorocarbon cooling for the semiconductor pixel and micro-strip sensors of inner tracking detector of the ATLAS experiment at the future CERN Large Hadron Collider (LHC). We proceeded with studies using perfluoro-n-propane (3M-"PFG 5030"; C3F8), perfluoro-n-butane (3M-"PFG 5040"; C4F10), trifluoro-iodo-methane (CF3I) and custom C3F8/C4F10 mixtures. Certain thermo-physical properties had to be verified for these fluids.

  5. Extensive simulation studies on the reconstructed image resolution of a position sensitive detector based on pixelated CdTe crystals

    CERN Document Server

    Zachariadou, K; Kaissas, I; Seferlis, S; Lambropoulos, C; Loukas, D; Potiriadis, C

    2011-01-01

    We present results on the reconstructed image resolution of a position sensitive radiation instrument (COCAE) based on extensive simulation studies. The reconstructed image resolution has been investigated in a wide range of incident photon energies emitted by point-like sources located at different source-to-detector distances on and off the detector's symmetry axis. The ability of the detector to distinguish multiple radioactive sources observed simultaneously is investigating by simulating point-like sources of different energies located on and off the detector's symmetry axis and at different positions

  6. Detection of secondary electrons with pixelated hybrid semiconductor detectors; Sekundaerelektronennachweis mit pixelierten hybriden Halbleiterdetektoren

    Energy Technology Data Exchange (ETDEWEB)

    Gebert, Ulrike Sonja

    2011-09-14

    Within the scope of this thesis, secondary electrons were detected with a pixelated semiconductor detector named Timepix. The Timepix detector consists of electronics and a sensor made from a semiconductor material. The connection of sensor and electronics is done for each pixel individually using bump bonds. Electrons with energies above 3 keV can be detected with the sensor. One electron produces a certain amount of electron-hole pairs according to its energy. The charge then drifts along an electric field to the pixel electronics, where it induces an electric signal. Even without a sensor it is possible to detect an electric signal from approximately 1000 electrons directly in the pixel electronics. Two different detector systems to detect secondary electrons using the Timepix detector were investigated during this thesis. First of all, a hybrid photon detector (HPD) was used to detect single photoelectrons. The HPD consists of a vacuum vessel with an entrance window and a cesium iodine photocathode at the inner surface of the window. Photoelectrons are released from the photocathode by incident light and are accelerated in an electric field towards the Timepix detector, where the point of interaction and the arrival time of the electron is determined. With a proximity focusing setup, a time resolution of 12 ns (with an acceleration voltage of 20 kV between photocathode and Timepix detector) was obtained. The HPD examined in this thesis showed a strong dependence of the dark rate form the acceleration voltage and the pressure in the vacuum vessel. At a pressure of few 10{sup -5} mbar and an acceleration voltage of 20 kV, the dark rate was about 800 Hz per mm{sup 2} area of the read out photocathode. One possibility to reduce the dark rate is to identify ion feedback events. With a slightly modified setup it was possible to reduce the dark rate to 0.5 Hz/mm{sup 2}. To achieve this, a new photocathode was mounted in a shorter distance to the detector. The

  7. LRAD, semiconductor, and other radiation detectors applied to environmental monitoring for alpha and beta contamination

    International Nuclear Information System (INIS)

    The very short range of alpha particles in air (typically 2 to 3 cm) has severely limited the use of traditional alpha monitors for detecting and identifying small amounts of alpha-producing contamination in soil, water, and other materials. Monitors based on the traditional alpha detector technology are often hard pressed to meet continually increasing sensitivity requirements. The long-range alpha detector (LRAD) avoids the distance restriction by detecting the ions produced by the interaction of alpha particles with air, rather than the alpha particles directly. The ions are swept into an ion detector either by a moving air current (generated by a fan) or a weak electric field. The LRAD is limited by the distance the ions can travel in the ∼5-s ion lifetime (1 to 100 m), rather than by the several-centimeter range of the alpha particles. The LRAD can be used to perform sensitive (less than 10 disintegrations per minute per 100 cm2) field scans of large surface areas (ranging from hundreds of square meters of concrete floor to thousands of square meters of soil). Because the 'active' element in a LRAD is a solid-metal ion collection plate, the detector is relatively inexpensive, easy to service, and quite rugged. However, the LRAD cannot supply any spectroscopic information to help identify the contaminant. Semiconductor, ionization chamber, and other types of particle detector can generate clean spectra from small samples of material and can identify trace amounts of surface contamination. Furthermore, these detectors are rugged enough to use routinely in a mobile laboratory for isotope identification of 'hot spots' located by the LRAD system. The combination of the LRAD with either an alpha spectrometer or a mobile laboratory with other particle detectors has applications for field beta-particle monitoring (such as would result from tritium contamination) as well as alpha particle detection. (author)

  8. Development of a novel 2D position-sensitive semiconductor detector concept

    CERN Document Server

    Bassignana, D; Jaramillo, R; Lozano, M; Munoz, F.J; Pellegrini, G; Quirion, D; Vila, I

    2012-01-01

    A novel 2D position-sensitive semiconductor detector concept has been developed employing resistive electrodes in a single-sided silicon microstrip sensor. The resistive charge division method has been implemented reading out each strip at both ends, in order to get the second coordinate of an ionizing event along the strips length. Two generations of prototypes, with different layout, have been produced and characterized using a pulsed near infra-red laser. The feasibility of the resistive charge division method in silicon microstrip detectors has been demonstrated and the possibility of single-chip readout of the device has been investigated. Experimental data were compared with the theoretical expectations and the electrical simulation of the sensor equivalent circuit coupled to simple electronics readout circuits. The agreement between experimental and simulation results validates the developed simulation as a tool for the optimization of future sensor prototypes.

  9. Gamma-Ray Assay with Lithium-Drifted Germanium Semiconductor Nuclear Detectors

    International Nuclear Information System (INIS)

    The characteristics and applications of the semiconductor nuclear radiation detectors which have been fabricated from germanium and compensated to high resistivity by the Pell lithium-drift method to obtain a large sensitive volume for gamma-ray detection are presented. Detector thicknesses of 1 mm to 4 mm are readily fabricated whereas 6 mm and greater are low-yield devices. Areas of 1 cm2 to 6 cm2 are available but the yield depends inversely upon the area. Gamma-ray resolutions of less than 10 keV are obtainable under standard laboratory conditions and less than 3 keV under ideal conditions. Such high resolutions will have immediate effect on gamma-ray assay as it may prove possible in many applications to remove the need for chemical separation. Results with 207Bi, 166Ho and other sources are given. (author)

  10. Very Low-Power Consumption Analog Pulse Processing ASIC for Semiconductor Radiation Detectors

    Energy Technology Data Exchange (ETDEWEB)

    Wessendorf, K.O.; Lund, J.C.; Brunett, B.A.; Laguna, G.R.; Clements, J.W.

    1999-08-23

    We describe a very-low power consumption circuit for processing the pulses from a semiconductor radiation detector. The circuit was designed for use with a cadmium zinc telluride (CZT) detector for unattended monitoring of stored nuclear materials. The device is intended to be battery powered and operate at low duty-cycles over a long period of time. This system will provide adequate performance for medium resolution gamma-ray pulse-height spectroscopy applications. The circuit incorporates the functions of a charge sensitive preamplifier, shaping amplifier, and peak sample and hold circuit. An application specific integrated circuit (ASIC) version of the design has been designed, built and tested. With the exception of the input field effect transistor (FET), the circuit is constructed using bipolar components. In this paper the design philosophy and measured performance characteristics of the circuit are described.

  11. 4. International Conference on Application of Semiconductor Detectors in Nuclear Physical Problems. Abstracts

    International Nuclear Information System (INIS)

    This was the fourth successive conference on semiconductor detectors (SD) of nuclear radiations that were held in Jurmala by the Riga Research and Development Institute for Radioisotope apparatus - the leading producer in the former USSR of SDs and equipment that use those. This conference used to attract leading experts of the USSR in physics and detector technology, as well as in other various fields of science and technology that use equipment with SDs. The main aim of the conference was to get together specialists who use SDs, consider problems they face and define the trends in development of appliances with SDs. Abstracts of this conference is arranged in following parts: Scientific researches, Radionuclide analysis for control of environmental objects, X-ray fluorescence and neutron activation analysis, Nuclear energetics, Medicine and biology, Special aspects of SD devices design

  12. Very Low-Power Consumption Analog Pulse Processing ASIC for Semiconductor Radiation Detectors

    International Nuclear Information System (INIS)

    We describe a very-low power consumption circuit for processing the pulses from a semiconductor radiation detector. The circuit was designed for use with a cadmium zinc telluride (CZT) detector for unattended monitoring of stored nuclear materials. The device is intended to be battery powered and operate at low duty-cycles over a long period of time. This system will provide adequate performance for medium resolution gamma-ray pulse-height spectroscopy applications. The circuit incorporates the functions of a charge sensitive preamplifier, shaping amplifier, and peak sample and hold circuit. An application specific integrated circuit (ASIC) version of the design has been designed, built and tested. With the exception of the input field effect transistor (FET), the circuit is constructed using bipolar components. In this paper the design philosophy and measured performance characteristics of the circuit are described

  13. 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.

  14. Operation of CdZnTe Semiconductor Detectors in Liquid Scintillator for the COBRA Experiment

    Energy Technology Data Exchange (ETDEWEB)

    Oldorf, Christian

    2015-08-15

    COBRA, the Cadmium-Zinc-Telluride O-neutrino double-Beta Research Apparatus, is an experiment aiming for the measurement of the neutrinoless double beta decay with several isotopes, in particular {sup 116}Cd, {sup 106}Cd and {sup 130}Te. A highly granular large scale experiment with about 400 kg of CdZnTe semiconductor detectors is currently under development. To provide evidence for the neutrinoless double beta decay of {sup 116}Cd, a background rate in the order of 10{sup -3} counts/keV/kg/a is needed to achieve the required half-life sensitivity of at least 2 . 10{sup 26} years. To reach this target, the detectors have to be operated in a highly pure environment, shielded from external radiation. Liquid scintillator is a promising candidate as a circum fluent replacement for the currently used lacquer. Next to the function as highly pure passivation material, liquid scintillator also acts as a neutron shield and active veto for external gammas. Within this thesis, the design, construction and assembly of a test set-up is described. The operation of four CdZnTe detectors after several years of storage in liquid scintillator is demonstrated. Next to extensive material compatibility tests prior to the assembly, the commissioning of the set-up and the characterization of the detectors are shown. Finally, results concerning the background reduction capability of liquid scintillator and the detection of cosmic muons are presented and compared to a Monte Carlo simulation.

  15. Development of gamma ray monitor using CdZnTe semiconductor detector

    Energy Technology Data Exchange (ETDEWEB)

    Rasolonjatovo, A.H.D.; Shiomi, T.; Nakamura, T. [Tohoku Univ., Department of Quantum Science and Energy Engineering, Sendai, Miyagi (Japan); Nishizawa, H.; Tsudaka, Y.; Fujiwara, H.; Araki, H.; Matsuo, K. [Mitsubishi Electric Corp., Amagasaki, Hyogo (Japan)

    2000-12-01

    In this study, we aimed to develop a new X-ray and gamma ray monitor using the CdZnTe semiconductor detector, which have high sensitivity at room temperature. The pulse height spectra and the detection efficiencies of 10x10 mm{sup 2} by 2 mm thick CdZnTe detector were measured in the energy range of 10 keV to 1.8 MeV by using monoenergetic X-ray and gamma ray sources. The measured results showed very good agreement with the results calculated using the EGS4 Monte Carlo code taking into account the charge collection efficiency in the detector. By using two CZT detectors of 10x10x2 mm{sup 3} and 3x3x2 mm{sup 3} coupled with a filter, the weighted sum of a few energy channels with different cut-off energies was finally found out to realize a flat energy response to equivalent dose (counts per mSv) within {+-}30% or {+-}10% deviation. (author)

  16. Picosecond timing of high-energy heavy ions with semiconductor detectors

    Science.gov (United States)

    Eremin, Vladimir; Kiselev, Oleg; Egorov, Nicolai; Eremin, Igor; Tuboltsev, Yuri; Verbitskaya, Elena; Gorbatyuk, Andrei

    2015-10-01

    Construction of new accelerating facilities to investigate reactions with heavy ions requires upgrading of the Time-of-Flight (TOF) systems for on-line ion identification. The requested time resolution of the TOF system developed for Super FRagment Separator in the frame of the FAIR program at GSI, Germany, is in the range of tens of picoseconds, which can be realized by using planar silicon detectors. Such resolution will allow characterization of relativistic ions from Lithium to Uranium. However, fast timing of heavy ions with semiconductor detectors is expected to be limited by the so-called plasma effect due to a high concentration of electron-hole pairs in tracks. Here the results of the experiment with relativistic 197Au ions (the energy of 920 MeV per nucleon) obtained with Si detectors are described, which showed the TOF time resolution around 14 ps rms. The physical mechanism of charge collection from high-density penetrating tracks of relativistic heavy ions is considered and the analysis of timing characteristics is performed taking into account track polarization. Polarization is shown to have a strong influence on the formation of the leading edge of the detector current response generated by relativistic heavy ions, which allows us to explain the observed high time resolution.

  17. Performance of CdZnTe geometrically weighted semiconductor Frisch grid radiation detectors

    International Nuclear Information System (INIS)

    Semiconductor Frisch grid radiation detectors have been manufactured and tested with encouraging results. Resolution enhancement occurs as a result of combining the geometric weighting effect, the small pixel effect and the Frisch grid effect. The devices are operated at ambient temperature without any pulse shape correction, rejection and compensation techniques. The new devices are manufactured from CdZnTe and do not require any cooling for operation. The geometrically weighted detectors have only one signal output to a standard commercially available Ortec 142A preamplifier. The detectors operate with simple commercially available NIM electronics, hence the device design can be coupled to any typical NIM system without the need for special electronic instruments or circuits. Geometrically weighted detectors that are 1 cubic centimeter in volume were fabricated from counter grade material, yet have shown room temperature energy resolution of 7.5% FWHM (at 29 C) for 57Co 122 keV gamma rays and 2.68% FWHM (at 23 C) for 137Cs 662 keV gamma rays

  18. Contribution to the three-dimensional simulation of semiconductor detectors in gamma rays spectrometry

    International Nuclear Information System (INIS)

    Parallel to the scientific investigations on gamma radioactivity, technological research on gamma ray detectors have rapidly developed. Gamma ray imaging is changing towards systems using room temperature semiconductors, whose principal advantages are compactness and intrinsic materials performances, due to the direct conversion of the gamma rays into electric charges. In the research field, the available solutions are numerous, thus justifying numerical simulation. Modelling presents a double interest for technological improvement and fast development of new techniques. A fully three-dimensional model of a semiconductor gamma ray detector is presented. It takes into account the physical phenomena involved in the detection process and models the readout electronic response and noise. The model successively involves the finite element transient computation of the adjoint transport equation, the Monte Carlo simulation of the photon transport and the electronic signal processing including an accurate noise model. The simulation outputs are pulse height spectra and bi parametric spectra (rise time versus pulse height). The validation carried out on each part of the simulator and also on the whole simulator confirms that the set of chosen models is correct and that our implementation is reliable. (author)

  19. MediSPECT: Single photon emission computed tomography system for small field of view small animal imaging based on a CdTe hybrid pixel detector

    Science.gov (United States)

    Accorsi, R.; Autiero, M.; Celentano, L.; Chmeissani, M.; Cozzolino, R.; Curion, A. S.; Frallicciardi, P.; Laccetti, P.; Lanza, R. C.; Lauria, A.; Maiorino, M.; Marotta, M.; Mettivier, G.; Montesi, M. C.; Riccio, P.; Roberti, G.; Russo, P.

    2007-02-01

    We describe MediSPECT, a new scanner developed at University and INFN Napoli, for SPECT studies on small animals with a small field of view (FOV) and high spatial resolution. The CdTe pixel detector (a 256×256 matrix of 55 μm square pixels) operating in single photon counting for detection of gamma-rays with low and medium energy (e.g. 125I, 27-35 keV, 99mTc, 140 keV), is bump bonded to the Medipix2 readout chip. The FOV of the MediSPECT scanner with a coded aperture mask collimator ranges from 6.3 mm (system spatial resolution 110 μm at 27-35 keV) to 24.3 mm. With a 0.30 mm pinhole the FOV ranges from 2.4 to 29 mm (where the system spatial resolution is 1.0 mm at 27-35 keV and 2.0 mm at 140 keV). MediSPECT will be used for in vivo imaging of small organs or tissue structures in mouse, e.g., brain, thyroid, heart or tumor.

  20. MediSPECT: Single photon emission computed tomography system for small field of view small animal imaging based on a CdTe hybrid pixel detector

    Energy Technology Data Exchange (ETDEWEB)

    Accorsi, R. [Department of Radiology, The Children' s Hospital of Philadelphia, Philadelphia, PA (United States); Autiero, M. [Dipartimento di Scienze Fisiche, Universita di Napoli Federico II, Naples (Italy); Celentano, L. [Dipartimento di Scienze Biomorfologiche e Funzionali, Universita di Napoli Federico II, Naples (Italy)] (and others)

    2007-02-01

    We describe MediSPECT, a new scanner developed at University and INFN Napoli, for SPECT studies on small animals with a small field of view (FOV) and high spatial resolution. The CdTe pixel detector (a 256x256 matrix of 55 {mu}m square pixels) operating in single photon counting for detection of gamma-rays with low and medium energy (e.g. {sup 125}I, 27-35 keV, {sup 99m}Tc, 140 keV), is bump bonded to the Medipix2 readout chip. The FOV of the MediSPECT scanner with a coded aperture mask collimator ranges from 6.3 mm (system spatial resolution 110 {mu}m at 27-35 keV) to 24.3 mm. With a 0.30 mm pinhole the FOV ranges from 2.4 to 29 mm (where the system spatial resolution is 1.0 mm at 27-35 keV and 2.0 mm at 140 keV). MediSPECT will be used for in vivo imaging of small organs or tissue structures in mouse, e.g., brain, thyroid, heart or tumor.

  1. MediSPECT: Single photon emission computed tomography system for small field of view small animal imaging based on a CdTe hybrid pixel detector

    International Nuclear Information System (INIS)

    We describe MediSPECT, a new scanner developed at University and INFN Napoli, for SPECT studies on small animals with a small field of view (FOV) and high spatial resolution. The CdTe pixel detector (a 256x256 matrix of 55 μm square pixels) operating in single photon counting for detection of gamma-rays with low and medium energy (e.g. 125I, 27-35 keV, 99mTc, 140 keV), is bump bonded to the Medipix2 readout chip. The FOV of the MediSPECT scanner with a coded aperture mask collimator ranges from 6.3 mm (system spatial resolution 110 μm at 27-35 keV) to 24.3 mm. With a 0.30 mm pinhole the FOV ranges from 2.4 to 29 mm (where the system spatial resolution is 1.0 mm at 27-35 keV and 2.0 mm at 140 keV). MediSPECT will be used for in vivo imaging of small organs or tissue structures in mouse, e.g., brain, thyroid, heart or tumor

  2. Electrical-modelling, design and simulation of cumulative radiation effects in semiconductor pixels detectors: prospects and limits

    CERN Document Server

    Fourches, Nicolas T; Chipaux, Rémi

    2014-01-01

    Silicon detectors have gained in popularity since silicon became a widely used micro/nanoelectronic semiconductor material. Silicon detectors are used in particle physics as well as imaging for pixel based detecting systems. Over the past twenty years a lot of experimental efforts have been focused on the effects of ionizing and non-ionizing radiation on silicon pixels. Some of this research was done in the framework of high luminosity particle physics experiments, along with radiation hardness studies of basic semiconductors devices. In its simplest form the semiconductor pixel detectors reduce to a PIN or PN structure partially or totally depleted, or in some MOS and APD (Avalanche PhotoDiode) structures. Bulk or surface defects affect considerably transport of free carriers. We propose guidelines for pixel design, which will be tested through a few pixel structures. This design method includes into the design the properties of defects. The electrical properties reduce to parameters, which can be introduced...

  3. A self-biased neutron detector based on an SiC semiconductor for a harsh environment.

    Science.gov (United States)

    Ha, Jang Ho; Kang, Sang Mook; Park, Se Hwan; Kim, Han Soo; Lee, Nam Ho; Song, Tae-Yung

    2009-01-01

    Neutron detector based on radiation-hard semiconductor materials like SiC, diamond and AlN has recently emerged as an attractive device for an in-core reactor neutron flux monitoring, a spent fuel characterization, and a home land security application. For the purpose of field measurement activity, a radiation detector having a low-power consumption, a mechanical stability and a radiation hardness is required. Our research was focused on the development of a radiation-resistive neutron semiconductor detector based on a wide band-gap SiC semiconductor. And also it will be operated at a zero-biased voltage using a strong internal electric field. The charge collection efficiency (CCE) was over 80% when the biased voltage was zero. When the biased voltage was applied above 20V, the charge collection efficiency reached 100%. PMID:19362006

  4. Development and characterization of the lead iodide semiconductor detector; Desenvolvimento e caracterizacao do detector semicondutor de iodeto de chumbo

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Icimone Braga de

    2001-07-01

    A methodology for purification and growth of PbI{sub 2} crystal as well as for its characterization as a room temperature radiation detector was developed in this work. Commercial salts were purified using the zone refining method and, for the purified material growth, the Bridgman method was used. To calculate the purification efficiency, studies of the decrease impurities concentrations were made in the salts and in three sections of the materials purified, using the neutron activation analysis technique. The results showed that the impurities segregate preferentially in the ingot final section. A significant decrease of the impurities concentration in function of the purification pass number was observed. The grown crystals presented good crystalline quality according to the results of the X-ray diffraction analysis. To evaluate the crystal as a semiconductor detector, measurements of dark leakage current, resistivity and the response of ({sup 241}Am) alpha particle and ({sup 241}Am, {sup 57}Co, {sup 133}Ba and {sup 137}Cs) gamma rays were carried out. The radiation response is strongly dependent on the crystals purity. The crystals purified with 500 passes exhibited energy resolution of 10% for {sup 241} Am alpha particle and the gamma rays resolution was compatible with the literature. The photosensibility of the PbI{sub 2} crystal found in the wavelength from 400 to 600 nm range suggests an another application at this crystal as a photodetector to be coupled to scintillators. (author)

  5. Spectroscopic imaging using Ge and CdTe based detector systems for hard x-ray applications.

    OpenAIRE

    Astromskas, Vytautas

    2016-01-01

    Third generation synchrotron facilities such as the Diamond Light Source (DLS) have a wide range of experiments performed for a wide range of science fields. The DLS operates at energies up to 150 keV which introduces great challenges to radiation detector technology. This work focuses on the requirements that the detector technology faces for X-ray Absorption Fine Structure (XAFS) and powder diffraction experiments in I12 and I15 beam lines, respectively. A segmented HPGe demonstrator det...

  6. A Monte Carlo simulation study of an improved K-edge log-subtraction X-ray imaging using a photon counting CdTe detector

    Science.gov (United States)

    Lee, Youngjin; Lee, Amy Candy; Kim, Hee-Joung

    2016-09-01

    Recently, significant effort has been spent on the development of photons counting detector (PCD) based on a CdTe for applications in X-ray imaging system. The motivation of developing PCDs is higher image quality. Especially, the K-edge subtraction (KES) imaging technique using a PCD is able to improve image quality and useful for increasing the contrast resolution of a target material by utilizing contrast agent. Based on above-mentioned technique, we presented an idea for an improved K-edge log-subtraction (KELS) imaging technique. The KELS imaging technique based on the PCDs can be realized by using different subtraction energy width of the energy window. In this study, the effects of the KELS imaging technique and subtraction energy width of the energy window was investigated with respect to the contrast, standard deviation, and CNR with a Monte Carlo simulation. We simulated the PCD X-ray imaging system based on a CdTe and polymethylmethacrylate (PMMA) phantom which consists of the various iodine contrast agents. To acquired KELS images, images of the phantom using above and below the iodine contrast agent K-edge absorption energy (33.2 keV) have been acquired at different energy range. According to the results, the contrast and standard deviation were decreased, when subtraction energy width of the energy window is increased. Also, the CNR using a KELS imaging technique is higher than that of the images acquired by using whole energy range. Especially, the maximum differences of CNR between whole energy range and KELS images using a 1, 2, and 3 mm diameter iodine contrast agent were acquired 11.33, 8.73, and 8.29 times, respectively. Additionally, the optimum subtraction energy width of the energy window can be acquired at 5, 4, and 3 keV for the 1, 2, and 3 mm diameter iodine contrast agent, respectively. In conclusion, we successfully established an improved KELS imaging technique and optimized subtraction energy width of the energy window, and based on

  7. Prompt gamma ray measurement in the KUR irradiation room by Cd-Zn-Te semiconductor detector for PG-SPECT

    International Nuclear Information System (INIS)

    Prompt gamma-rays from 10B(n,αγ)7Li reaction yielded in polyethylene plate containing 30 wt% 10B and/or 50 ppm 10B water phantom were measured in the medical irradiation room at the KUR-HWNIF, by Cd-Zn-Te semiconductor detector with tungsten collimator which has a hole of 3 mm diameter and 8 cm and/or 14 cm length. An application possibility of Cd-Zn-Te semiconductor detector to PG-SPECT was examined experimentally for BNCT. (author)

  8. Characterization of CdTe and CdZnTe detectors for gamma-ray imaging applications

    Science.gov (United States)

    Verger, L.; Boitel, M.; Gentet, M. C.; Hamelin, R.; Mestais, C.; Mongellaz, F.; Rustique, J.; Sanchez, G.

    2001-02-01

    CEA-LETI in association with Bicron and Crismatec has been developing solid-state gamma camera technology based on CZT. The project included gamma camera head systems development including front-end electronics with an integrated circuit (ASIC), material growth, and detector fabrication and characterization. One feature of the work is the use of linear correlation between the amplitude and the fast rise time of the signal - which corresponds to the electron transit time in the detector, a development that was reported previously and which allows more than 80% of the 122 keV γ-photons incident on HPBM material to be recovered in a ±6.5% 2D window. In the current work, we summarize other methods to improve CZT detector performance and compare them with the Bi-Parametric Spectrum (BPS) method. The BPS method can also be applied as a diagnositic. BPS curve shapes are shown to vary with electric field, and with electron transport properties, and the correction algorithims are seen to be robust over a range of values. In addition, the technique is found to improve detectors from a variety of sources including some with special electrode geometries. In all cases, the BPS method improves efficiency (>75%) without degrading energy resolution (± 6.5% 2D window) even for a monolithic detector. The method does not overcome bulk inhomogeneity nor noise which comes from low resistivity.

  9. Advanced radiation detector development: Advanced semiconductor detector development: Development of a room-temperature, gamma ray detector using gallium arsenide to develop an electrode detector. Annual progress report, September 30, 1994--September 29, 1995

    International Nuclear Information System (INIS)

    The advanced detector development project at the University of Michigan has completed the first full year of its current funding. The general goals are the development of radiation detectors and spectrometers that are capable of portable room temperature operation. Over the past 12 months, the authors have worked primarily in the development of semiconductor spectrometers with ''single carrier'' response that offer the promise of room temperature operation and good energy resolution in gamma ray spectroscopy. They have also begun a small scale effort at investigating the properties of a small non-spectroscopic detector system with directional characteristics that will allow identification of the approximate direction in which gamma rays are incident. These activities have made use of the extensive clean room facilities at the University of Michigan for semiconductor device fabrication, and also the radiation measurement capabilities provided in the laboratory in the Phoenix Building on the North Campus

  10. Picosecond timing of high-energy heavy ions with semiconductor detectors

    International Nuclear Information System (INIS)

    Construction of new accelerating facilities to investigate reactions with heavy ions requires upgrading of the Time-of-Flight (TOF) systems for on-line ion identification. The requested time resolution of the TOF system developed for Super FRagment Separator in the frame of the FAIR program at GSI, Germany, is in the range of tens of picoseconds, which can be realized by using planar silicon detectors. Such resolution will allow characterization of relativistic ions from Lithium to Uranium. However, fast timing of heavy ions with semiconductor detectors is expected to be limited by the so-called plasma effect due to a high concentration of electron–hole pairs in tracks. Here the results of the experiment with relativistic 197Au ions (the energy of 920 MeV per nucleon) obtained with Si detectors are described, which showed the TOF time resolution around 14 ps rms. The physical mechanism of charge collection from high-density penetrating tracks of relativistic heavy ions is considered and the analysis of timing characteristics is performed taking into account track polarization. Polarization is shown to have a strong influence on the formation of the leading edge of the detector current response generated by relativistic heavy ions, which allows us to explain the observed high time resolution. - HighLights: • The study on timing of relativistic Au ions using Time-Of-Flight method is performed. • Time resolution better than 20 ps rms is reached using Si planar detectors in TOF. • The model is proposed to explain high time resolution in timing of relativistic ions. • The model considers polarization in plasma state in high-density penetrating tracks

  11. Fast spectroscopic imaging with pixel semiconductor detector Timepix and parallel data reading

    International Nuclear Information System (INIS)

    Non-invasive techniques utilizing X-ray radiation offer a powerful tool for the inspection of the inner composition of a wide variety of objects. The highly sensitive hybrid semiconductor pixel detector Timepix is capable of detecting and resolving subtle and low-contrast differences in radiography measurements. Moreover the Timepix detector offers 65536 individual pixels with spectrometric capabilities. With proper per-pixel energy calibration this feature enables the application of various energy based imaging techniques - from basic energy windowing to fully spectroscopic imaging. The main limitations of these methods are the detector energy resolution and data acquisition speed of 100 frames per second - the necessity of taking frames with low occupancy for event by event cluster analysis leads to several hours long measurements. The latter nuisance can be overcome by the utilization of the newly developed modular read-out FITPix3 with the adapter chipboard designed for parallel data reading. This read-out version can acquire over 850 compressed frames per second which reduces the measurement time of many spectroscopic measurements by factor of ten (spectra with high enough statistics are taken in tens of minutes). The short description of the new FITPix3 parallel read-out together with the progression in spectroscopic multi-channel energy imaging demonstrated on model samples are presented in this contribution

  12. Monte Carlo simulation for the electron cascade due to gamma rays in semiconductor radiation detectors

    International Nuclear Information System (INIS)

    A Monte Carlo code was developed for simulating the electron cascade in radiation detector materials. The electron differential scattering cross sections were derived from measured electron energy-loss and optical spectra, making the method applicable for a wide range of materials. The detector resolution in a simplified model system shows dependence on the bandgap, the plasmon strength and energy, and the valence band width. In principle, these parameters could be optimized to improve detector performance. The intrinsic energy resolution was calculated for three semiconductors: silicon (Si), gallium arsenide (GaAs), and zinc telluride (ZnTe). Setting the ionization thresholds for electrons and holes is identified as a critical issue, as this strongly affects both the average electron-hole pair energy w and the Fano factor F. Using an ionization threshold from impact ionization calculations as an effective bandgap yields pair energies that are well matched to measured values. Fano factors of 0.091 (Si), 0.100 (GaAs), and 0.075 (ZnTe) were calculated. The Fano factor calculated for silicon using this model was lower than some results from past simulations and experiments. This difference could be attributed to problems in simulating inter-band transitions and the scattering of low-energy electrons.

  13. Monte Carlo simulation for the electron cascade due to gamma rays in semiconductor radiation detectors

    Energy Technology Data Exchange (ETDEWEB)

    Narayan, Raman D.; Miranda, Ryan; Rez, Peter [Department of Physics, Arizona State University, Tempe, Arizona 85287-1504 (United States)

    2012-03-15

    A Monte Carlo code was developed for simulating the electron cascade in radiation detector materials. The electron differential scattering cross sections were derived from measured electron energy-loss and optical spectra, making the method applicable for a wide range of materials. The detector resolution in a simplified model system shows dependence on the bandgap, the plasmon strength and energy, and the valence band width. In principle, these parameters could be optimized to improve detector performance. The intrinsic energy resolution was calculated for three semiconductors: silicon (Si), gallium arsenide (GaAs), and zinc telluride (ZnTe). Setting the ionization thresholds for electrons and holes is identified as a critical issue, as this strongly affects both the average electron-hole pair energy w and the Fano factor F. Using an ionization threshold from impact ionization calculations as an effective bandgap yields pair energies that are well matched to measured values. Fano factors of 0.091 (Si), 0.100 (GaAs), and 0.075 (ZnTe) were calculated. The Fano factor calculated for silicon using this model was lower than some results from past simulations and experiments. This difference could be attributed to problems in simulating inter-band transitions and the scattering of low-energy electrons.

  14. Study of gain phenomenon in lateral metal-semiconductor-metal detectors for indirect conversion medical imaging

    Science.gov (United States)

    Abbaszadeh, Shiva; Allec, Nicholas; Wang, Kai; Chen, Feng; Karim, Karim S.

    2011-03-01

    Previously, metal-semiconductor-metal (MSM) lateral amorphous selenium (a-Se) detectors have been proposed for indirect detector medical imaging applications. These detectors have raised interest due to their high-speed and photogain. The gain measured from these devices was assumed to have been photoconductive gain; however the origin of this gain was not fully understood. In addition, whether or not there was any presence of photocurrent multiplication gain was not investigated. For integration-type applications photocurrent multiplication gain is desirable since the total collected charge can be greater than the total number of absorbed photons. In order to fully appreciate the value of MSM devices and their benefit for different applications, whether it is counting or integration applications, we need to investigate the responsible mechanisms of the observed response. In this paper, we systematically study, through experimental and theoretical means, the nature of the photoresponse and its responsible mechanisms. This study also exposes the possible means to increase the performance of the device and under what conditions it will be most beneficial.

  15. Development of the mercury iodide semiconductor crystal for application as a radiation detector

    International Nuclear Information System (INIS)

    In this work, the establishment of a technique for HgI growth and preparation of crystals, for use as room temperature radiation semiconductor detectors is described. Three methods of crystal growth were studied while developing this work: physical vapor transport (PVT); saturated solution of HgI2, using two different solvents; (a) dimethyl sulfoxide (DMSO) and (b) acetone, and the Bridgman method. In order to evaluate the obtained crystals by the three methods, systematic measurements were carried out for determining the stoichiometry, structure, orientation, surface morphology and impurity of the crystal. The influence of these physical chemical properties on the crystals development was studied, evaluating their performance as radiation detectors. The X-ray diffractograms indicated that the crystals were, preferentially, oriented in the (001) e (101) directions with tetragonal structure for all crystals. Nevertheless, morphology with a smaller deformation level was observed for the crystal obtained by the PVT technique, comparing to other methods. Uniformity on the surface layer of the PVT crystal was detected, while clear incrustations of elements distinct from the crystal could be viewed on the DMSO crystal surface. The best results as to radiation response were found for the crystal grown by physical vapor transport. Significant improvement in the HgIz2 radiation detector performance was achieved for purer crystals, growing the crystal twice by PVT technique. (author)

  16. Development of novel semiconductor detectors for the detection of ionizing radiation

    International Nuclear Information System (INIS)

    The present thesis treats the development of novel energy- and position-resolving semiconductor detectors: Fully depletable pn CCD's. In experiments of high-energy physics they are suited as highly resolving position-sensitive detectors for minimally ionizing particles. In nuclear and atomic physics they can be applied as position-resolving energy spectrometers. Increasing interest detectors of this type find also at synchrotron-radiation sources with photon energies from 20 eV to 50 keV. As focal instruments of X-ray telescopes they are in astrophysical measurements in an energy range from 100 eV to 15 keV of use. The required accuracy in the energy measurement amounts to 100 eV (FWHM) at an X-ray energy of 1 keV, at a simultaneous precision of the position determination of 50 μm. The measurement results which are here presented on the first fully depletable CCD's show that the components posses the potential to fulfill these requirements. (orig.)

  17. A comparison of various strategies to equalize the lower energy thresholds of a CdTe Medipix2 hexa detector for X-ray imaging applications

    Energy Technology Data Exchange (ETDEWEB)

    Koenig, T; Zuber, M; Schuenke, P; Nill, S; Oelfke, U [German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, 69120 Heidelberg (Germany); Zwerger, A; Fauler, A; Fiederle, M, E-mail: t.koenig@dkfz.de [Freiburg Materials Research Center (FMF), Stefan-Meier-Strasse 21, 79104 Freiburg (Germany)

    2011-01-15

    Technological advances have made possible the development of pixelized photon counting semiconductor detectors, many of which are used in X-ray imaging to resolve the spectral composition of the incident photons. Here, in a so-called Hexa detector, we employ a 3 x 2 array of Medipix2 MXR readout chips, bump bonded to a cadmium telluride sensor of 1 mm thickness with a pixel pitch of 165 {mu}m. Each pixel in this assembly offers two variable energy thresholds, which enables counting of only those photons within an energy range of interest. As manufacturing tolerances cause deviations in each of the pixel's responses, the two thresholds can be calibrated for every pixel to render their response to radiation more homogeneous. In this work, we compare various methods that we chose to equalize the lower thresholds: a) the noise edge of the detector electronics, the characteristic X-rays from b) silver and c) tantalum foils as well as flat fields obtained at d) 40 and e) 120 kVp. It will be shown that the energy dependence in the resulting adjustment bit maps are only small, whereas the question as to which strategy to choose (peak position vs. image homogeneity) will have a greater influence on the resulting corrections. Additionally, we observed a decrease in the mean adjustment values with increasing distance from the central axis of the Hexa detector under study.

  18. Dental x-ray spectrometry with cadmium telluride detectors

    International Nuclear Information System (INIS)

    Cadmium telluride (CdTe) semiconductor detectors provide high detection efficiency for use in the diagnostic x-rays energy range, due to the high atomic number and density of the crystal. This kind of detector has been utilized in diagnostic x-ray spectroscopy, mainly in the mammography energy range, but only scarce information about its use in dental x-ray beams has been published. In this way, a portable 3x3x1 mm3 CdTe solid state detector (XR-100T CdTe, Amptek, Inc.) with electronic system, tungsten pinhole collimators, alignment device and associated software was utilized in this work. A single-phase dental unit with adjustable kVp and mA was employed and the x-ray spectra were experimentally determined at 50, 60 and 70 kVp with a tube current of 0.5 mA and 1.5mm Al additional filtration. An experimental setup was developed to guarantee a perfect alignment between the detector and the focal spot. The detector to focal spot distance was 3.0 m. Two 2mm thick tungsten pinholes (Amptek EXVC kit) with 0.4 mm and 1.0 mm collimator aperture diameters were positioned close to the detector in order to reduce the pulse pile-up events at high counting rates. A stripping procedure was implemented to correct the pulse height distribution in order to determine the photon spectra. The calculation of the CdTe response, used to correct the measured spectra, was simulated using the GEANT4 Monte Carlo toolkit. The x-ray spectra were compared with the spectra obtained with a high-purity germanium detector (EGP200-13-TR, Eurisys Mesures) with associated electronic devices and software. The reasonable agreement between the results obtained with both detectors shows that CdTe detectors can be successfully utilized for dental x-ray spectrometry. (author)

  19. PC based analysis of gamma ray spectra generated by semiconductor detectors

    International Nuclear Information System (INIS)

    This report describes a spectrum analysis method and computer program for analysis of gamma spectra obtained by using semiconductor detectors and multichannel analysers. The analysis steps incorporated are smoothing, peak location using signal processing method of convolution, selectable background subtraction viz linear, polynomial and step like, peak fitting both for singlets and doublets using Mukoyama's method for evaluation of full width at half maximum and area evaluation including errors in its evaluation. The program also provides a facility for energy calibration. Typical results of analysis for singlets and doublets are included. This report is based on Wilson's report which has been modified and extended. The program is written in BASIC and its listing is included in the appendices. (author). 20 refs., 2 figs., 2 tabs

  20. High-efficiency microstructured semiconductor neutron detectors for direct 3He replacement

    International Nuclear Information System (INIS)

    High-efficiency Microstructured Semiconductor Neutron Detectors (MSNDs) have been tiled and arranged in a cylindrical form factor in order to serve as a direct replacement to aging and increasingly expensive 3He gas-filled proportional neutron detectors. Two 6-in long by 2-in diameter cylinders were constructed and populated with MSNDs which were then directly compared to a 4 atm Reuter Stokes 3He detector of the same dimensions. The Generation 1 MSND-based 3Helium-Replacement (HeRep Mk I) device contained sixty-four 1-cm2 active-area MSNDs, each with an intrinsic neutron detection efficiency of approximately 7%. A Generation 2 device (the HeRep Mk II) was populated with thirty 4-cm2 active-area MSNDs, with an intrinsic thermal neutron detection efficiency of approximately 30%. The MSNDs of each HeRep were integrated to count as a single device. The 3He proportional counter and the HeRep devices were tested while encased in a cylinder of high-density polyethylene measuring a total of 6-in by 9-in. The 3He counter and the HeRep Mk II were each placed 1 m from a 54-ng 252Cf source and tested for efficiency. The 3He proportional counter had a net count rate of 17.13±0.10 cps at 1 m. The HeRep Mk II device had a net count rate of 17.60±0.10 cps, amounting to 102.71±2.65% of the 3He gas counter while inside of the moderator. Outside of moderator, the 3He tube had a count rate of 3.35±0.05 cps and the HeRep Mk II device reported 3.19±05, amounting to 95.15±9.04% of the 3He neutron detector

  1. Study of a New Design of P-N Semiconductor Detector Array for Nuclear Medicine Imaging by Monte Carlo Simulation Codes

    OpenAIRE

    Hajizadeh-Safar, M.; Ghorbani, M.; Khoshkharam, S.; Ashrafi, Z.

    2014-01-01

    Gamma camera is an important apparatus in nuclear medicine imaging. Its detection part is consists of a scintillation detector with a heavy collimator. Substitution of semiconductor detectors instead of scintillator in these cameras has been effectively studied. In this study, it is aimed to introduce a new design of P-N semiconductor detector array for nuclear medicine imaging. A P-N semiconductor detector composed of N-SnO2 :F, and P-NiO:Li, has been introduced through simulating with MCNPX...

  2. Treatment verification and in vivo dosimetry for total body irradiation using thermoluminescent and semiconductor detectors

    International Nuclear Information System (INIS)

    The objective of this work is the characterization of thermoluminescent and semiconductor detectors and their applications in treatment verification and in vivo dosimetry for total body irradiation (TBI) technique. Dose measurements of TBI treatment simulation performed with thermoluminescent detectors inserted in the holes of a “Rando anthropomorphic phantom” showed agreement with the prescribed dose. For regions of the upper and lower chest where thermoluminescent detectors received higher doses it was recommended the use of compensating dose in clinic. The results of in vivo entrance dose measurements for three patients are presented. The maximum percentual deviation between the measurements and the prescribed dose was 3.6%, which is consistent with the action level recommended by the International Commission on Radiation Units and Measurements (ICRU), i.e., ±5%. The present work to test the applicability of a thermoluminescent dosimetric system and of a semiconductor dosimetric system for performing treatment verification and in vivo dose measurements in TBI techniques demonstrated the value of these methods and the applicability as a part of a quality assurance program in TBI treatments. - Highlights: • Characterization of a semiconductor dosimetric system. • Characterization of a thermoluminescent dosimetric system. • Application of the TLDs for treatment verification in total body irradiation treatments. • Application of semiconductor detectors for in vivo dosimetry in total body irradiation treatments. • Implementation of in vivo dosimetry as a part of a quality assurance program in radiotherapy

  3. Photoinduced tellurium precipitation in CdTe

    Science.gov (United States)

    Sugai, Shunji

    1991-06-01

    Tellurium precipitation in CdTe is found to be induced by photoirradiation with energy higher than the energy gap at 240 W/sq cm. It is suggested that this photoinduced precipitation is related with the strong electron-phonon interactions, possibly self-trapped excitons. This irreducible tellurium precipitation may cause a serious problem for the life of semiconductor devices.

  4. Semiconductor diodes as neutron detectors for position-sensitive measurements and for application in personal neutron dosimetry

    Science.gov (United States)

    Balzhaeuser, Michael; Dehoff, A.; Engels, R.; Hoengesberg, F.; Lauter, J.; Luth, Hans; Reetz, M.; Reinartz, Richard; Richter, H.; Schelten, Jim; Schmitz, Th.; Steffen, A.; Vockenberg, Th.

    1997-02-01

    A new design for a position-sensitive detector system for thermal neutrons is introduced. The detection principle with a thin 6LiF converter on the surface of a semiconductor diode is described. In experiments with thermal neutrons, a spatial resolution of 1.25 mm was obtained. The detector is insensitive to (gamma) -rays with energies up to 1.5 MeV. The design of a detector with an improvement of the detection efficiency for thermal neutrons from 2.5 percent up to 35 percent is also proposed and the present state of the process development for its fabrication is described.

  5. Dynamic defectoscopy with flat panel and CdTe Timepix X-ray detectors combined with an optical camera

    Czech Academy of Sciences Publication Activity Database

    Vavřík, Daniel; Fauler, A.; Fiederle, M.; Jandejsek, Ivan; Jakůbek, J.; Tureček, D.; Zwerger, A.

    2013-01-01

    Roč. 8, April (2013), C04009. ISSN 1748-0221. [International Workshop on Radiation Imaging Detector s /14./. Figueira da Foz, Coimbra, 01.07.2012-05.07.2012] R&D Projects: GA ČR(CZ) GA103/09/2101 Institutional support: RVO:68378297 Keywords : X-ray digital radiography * fracture mechanics * crack path * X-ray defectoscopy Subject RIV: JM - Building Engineering Impact factor: 1.526, year: 2013 http://iopscience.iop.org/1748-0221/8/04/C04009/

  6. Development of a (Hg, Cd)Te photodiode detector, Phase 2. [for 10.6 micron spectral region

    Science.gov (United States)

    1972-01-01

    High speed sensitive (Hg,Cd)Te photodiode detectors operating in the 77 to 90 K temperature range have been developed for the 10.6 micron spectral region. P-N junctions formed by impurity (gold) diffusion in p-type (Hg, Cd) Te have been investigated. It is shown that the bandwidth and quantum efficiency of a diode are a constant for a fixed ratio of mobility/lifetime ratio of minority carriers. The minority carrier mobility and lifetime uniquely determine the bandwidth and quantum efficiency and indicate the shallow n on p (Hg,Cd) Te diodes are preferable as high performance, high frequency devices.

  7. Fast front-end electronics for semiconductor tracking detectors: Trends and perspectives

    International Nuclear Information System (INIS)

    In the past few years, extensive research efforts pursued by both the industry and the academia have lead to major improvements in the performance of Analog to Digital Converters (ADCs) and Time to Digital Converters (TDCs). ADCs achieving 8–10 bit resolution, 50–100 MHz conversion frequency and less than 1 mW power consumption are the today's standard, while TDCs have reached sub-picosecond time resolution. These results have been made possible by architectural upgrades combined with the use of ultra deep submicron CMOS technologies with minimum feature size of 130 nm or smaller. Front-end ASICs in which a prompt digitization is followed by signal conditioning in the digital domain can now be envisaged also within the tight power budget typically available in high density tracking systems. Furthermore, tracking detectors embedding high resolution timing capabilities are gaining interest. In the paper, ADC's and TDC's developments which are of particular relevance for the design front-end electronics for semiconductor trackers are discussed along with the benefits and challenges of exploiting such high performance building blocks in implementing the next generation of ASICs for high granularity particle detectors

  8. Fast front-end electronics for semiconductor tracking detectors: Trends and perspectives

    Energy Technology Data Exchange (ETDEWEB)

    Rivetti, Angelo

    2014-11-21

    In the past few years, extensive research efforts pursued by both the industry and the academia have lead to major improvements in the performance of Analog to Digital Converters (ADCs) and Time to Digital Converters (TDCs). ADCs achieving 8–10 bit resolution, 50–100 MHz conversion frequency and less than 1 mW power consumption are the today's standard, while TDCs have reached sub-picosecond time resolution. These results have been made possible by architectural upgrades combined with the use of ultra deep submicron CMOS technologies with minimum feature size of 130 nm or smaller. Front-end ASICs in which a prompt digitization is followed by signal conditioning in the digital domain can now be envisaged also within the tight power budget typically available in high density tracking systems. Furthermore, tracking detectors embedding high resolution timing capabilities are gaining interest. In the paper, ADC's and TDC's developments which are of particular relevance for the design front-end electronics for semiconductor trackers are discussed along with the benefits and challenges of exploiting such high performance building blocks in implementing the next generation of ASICs for high granularity particle detectors.

  9. In vivo dosimetry with semiconductor and thermoluminescent detectors applied to head and neck cancer treatment

    International Nuclear Information System (INIS)

    In vivo dosimetry in radiotherapy, i. e, the assessment of the doses received by patients during their treatments, permits a verification of the therapy quality. A routine of in vivo dosimetry is, undoubtedly, a direct benefit for the patient. Unfortunately, in Brazil and in Latin America this procedure is still a privilege for only a few patients. This routine is of common application only in developed countries. The aim of this work is to show the viability and implementation of a routine in vivo dosimetry, using diodes semiconductors and thermoluminescent dosimeters (TLD), at the radiotherapy section of the National Institute of Cancer in Brazil, in the case of head and neck cancer treatment. In order to reach that aim, the characteristics of the response of diodes ISORAD-p and LiF:Mg;Ti (TLD-100) thermoluminescent detectors in powder form were determined. The performance of those detectors for in vivo dosimetry was tested using an RANDO Alderson anthropomorfic phantom and, once their adequacy proved for the kind of measurements proposed, they were used for dose assessment in the case of tumour treatments in the head and neck regions, for Cobalt-60 irradiations. (author)

  10. Optical cross-talk effect in a semiconductor photon-counting detector array

    Science.gov (United States)

    Prochazka, Ivan; Hamal, Karel; Kral, Lukas; Blazej, Josef

    2005-09-01

    Solid state single photon detectors are getting more and more attention in various areas of applied physics: optical sensors, communication, quantum key distribution, optical ranging and Lidar, time resolved spectroscopy, opaque media imaging and ballistic photon identification. Avalanche photodiodes specifically designed for single photon counting semiconductor avalanche structures have been developed on the basis of various materials: Si, Ge, GaP, GaAsP and InGaAs/InGaAsP at the Czech Technical University in Prague during the last 20 years. They have been tailored for numerous applications. Recently, there is a strong demand for the photon counting detector in a form of an array; even small arrays 10x1 or 3x3 are of great importance for users. Although the photon counting array can be manufactured, there exists a serious limitation for its performance: the optical cross-talk between individual detecting cells. This cross-talk is caused by the optical emission of the avalanche photon counting structure which accompanies the photon detection process. We have studied in detail the optical emission of the avalanche photon counting structure in the silicon shallow junction type photodiode. The timing properties, radiation pattern and spectral distribution of the emitted light have been measured for various detection structures and their different operating conditions. The ultimate limit for the cross-talk has been determined and the methods for its limitation have been proposed.

  11. Design and implementation of a photo detector using a complementary metal-oxide semiconductor

    International Nuclear Information System (INIS)

    In this paper, we present a photo detector using a complementary metal-oxide semiconductor (CMOS) for plastic optical fiber (POF) applications. Generally, the PIN photodiode and optical receiver front-end circuit are made from III-V compound materials, such as GaAs, InP, and HEMT (High Electron Mobility Transistor), due to their high speed and low noise characteristics. However, silicon deep-submicron CMOS technology is more attractive due to its low cost and high integration capacity. A PIN photodiode using a CMOS suffers from a low responsivity (R) a slow spreading speed of drift and diffusion current generated by photon. To overcome the low responsivity of the CMOS PIN photodiode, we exploit a PN junction between the N-well and the P-substrate. We propose a finger-shaped arrangement of the P-substrate to compensate for the slow spreading speed of the drift currents. The implemented CMOS PIN photodiode exhibits 0.12-A/W responsivity and 4.5-pF parasitic capacitance. Also, the optical receiver front-end circuit for the POF applications is integrated with the CMOS PIN photodiode. The designed photo detector exhibits a 112-MHz 3-dB bandwidth and consumes only 3-mA of DC current from a single 3.3 V supply voltage.

  12. Fast front-end electronics for semiconductor tracking detectors: Trends and perspectives

    Science.gov (United States)

    Rivetti, Angelo

    2014-11-01

    In the past few years, extensive research efforts pursued by both the industry and the academia have lead to major improvements in the performance of Analog to Digital Converters (ADCs) and Time to Digital Converters (TDCs). ADCs achieving 8-10 bit resolution, 50-100 MHz conversion frequency and less than 1 mW power consumption are the today's standard, while TDCs have reached sub-picosecond time resolution. These results have been made possible by architectural upgrades combined with the use of ultra deep submicron CMOS technologies with minimum feature size of 130 nm or smaller. Front-end ASICs in which a prompt digitization is followed by signal conditioning in the digital domain can now be envisaged also within the tight power budget typically available in high density tracking systems. Furthermore, tracking detectors embedding high resolution timing capabilities are gaining interest. In the paper, ADC's and TDC's developments which are of particular relevance for the design front-end electronics for semiconductor trackers are discussed along with the benefits and challenges of exploiting such high performance building blocks in implementing the next generation of ASICs for high granularity particle detectors.

  13. Alternative collimator for CdTe (model XR-100T), when it is used for a direct measurements of radiodiagnostic spectra; Colimador alternativo para um detector de CdTe (modelo XR-100T), usado em medidas diretas de espectros de radiodiagnostico

    Energy Technology Data Exchange (ETDEWEB)

    Soares, C.; Guevara, M.V. Manso; Milian, F. Mas; Garcia, F., E-mail: mvictoria.mansoguevara@gmail.com [Universidade Estadual de Santa Cruz (CPqCTR/UESC), Ilheus, BA (Brazil). Departamento de Ciencias Exatas; Nieto, L. [Universidade Estadual do Sudoeste da Bahia (UESB), Itapetinga, BA (Brazil)

    2014-01-15

    The spectrum simulation is a powerful instrument of great practical and pedagogical usefulness, because it helps to understand the technical and the instrumental limits of parameters in optimized measurements of magnitudes of interest in physics. Monte Carlo models, based on particle and radiation transport, provide easy and flexible tools for simulating complex geometries and materials. Particularly, MCNPX code is used to compare, manipulate, and quantify simulated and measured spectra. The purpose of this work is to use this tool set to estimate the characteristics of a collimation device, avoiding permanent and temporary damages into the diode-pin detector, during direct measurements of the Bremsstrahlung's spectrum, which was generated from diagnosis tubes with medical purpose. The simulations were made with a maximum voltage of 150 kVp, and typical charges used in radiological protocols in the medical area. Also, differential high pulse spectra, simulated and measured with a CdTe Detector, are reported. (author)

  14. Angle software for semiconductor detector gamma-efficiency calculations: applicability to radioactive waste characterization

    International Nuclear Information System (INIS)

    ANGLE software for semiconductor detector efficiency calculations in its various forms has been in use for 15 years now in numerous gamma-spectrometry based analytical laboratories all around. It goes about a semi-empirical approach, which combines advantages of both absolute and relative methods to determining sample activity by gamma-spectrometry, while conciliating and minimizing their drawbacks. Physical model behind is the concept of the effective solid angle - a parameter calculated upon the input data on geometrical, physical and chemical (composition) characteristics of: 1) The source (incl. its container vessel); 2) The detector (incl. crystal housing and end-cap); and 3) Counting arrangement (incl. intercepting layers between the latter two). It was shown earlier that only simultaneous differential treatment of gamma attenuation, counting geometry and detector response - as is the case with ANGLE - is essentially justified for this type of calculations. Attempting the other-way-round, i.e. to separately calculating these three phenomena, generally lead to (over)simplifications, which further require complex corrections with limited success. The program can be applied to practically all situations encountered in gamma-laboratory practice: point, disc, cylindrical or Marinelli samples, small and large, of any matrix composition. No standards are required, but a start-up 'reference efficiency curve' should be obtained ('once for ever') by measuring a set of calibrated point sources at a large source-to-detector distance (e.g. 20-30 cm, to avoid true coincidence effects). Calibration sources are chosen to cover gamma-energy region of analytical interest (e.g. 50-3000 keV). This initial effort is largely paid back in future exploitation. Briefly, ANGLE is characterized by: 1) A broad application range; 2) Pretty fair accuracy for this type of calculations (of a few percent order); 3) Comfortable data manipulation (under WINDOWS); 4) Short computation times; 5

  15. Study of correlation between the structural defects and inhomogeneities of CDTE based radiation detectors used for medical imaging

    International Nuclear Information System (INIS)

    In the present Ph.D. thesis, we investigate microstructural defects in a chlorine-doped cadmium telluride crystal (CdTe:Cl), to understand the relationship between defects and performance of CdTe-based radiation detectors. Characterization tools, such as diffraction topography and chemical etching, are used for bulk and surface investigations of the distribution of dislocations. Dislocations are arranged into walls. Most of them appear to cross the whole thickness of the sample. Very good correlation is observed between areas with variations of dark-current and photo-current, and positions of the dislocation walls revealed at the surface of the sample. Then spectroscopic analysis of these defects was performed at low temperatures. It highlighted that dislocation walls induce non-radiative recombination, but it didn't show any Y luminescence usually attributed to dislocations in the literature. Ion Beam Induced Current (IBIC) measurements were used to evaluate the influence of dislocation walls on charge carrier transport properties. This experiment shows that they reduce the mobility-lifetime product of the charge carriers. A very clear correlation was, in fact, established between the distribution of the dislocation network and the linear defects revealed by their lower CIE on the device. (author)

  16. Dosimetric evaluation of semiconductor detectors for application in neutron dosimetry and microdosimetry in nuclear reactor and radiosurgical facilities

    International Nuclear Information System (INIS)

    The main objective of this research is the dosimetric evaluation of semiconductor components (surface barrier detectors and PIN photodiodes) for applications in dose equivalent measurements on low dose fields (fast and thermal fluxes) using an AmBe neutron source, the IEA-R1 reactor neutrongraphy facility (epithermal and thermal fluxes) and the Critical Unit facility IPEN/MB-01 (fast fluxes). As moderator compound to fast neutrons flux from the AmBe source was used paraffin and boron and polyethylene as converter for thermal and fast neutrons measurements. The resulting fluxes were used to the irradiation of semiconductor components (SSB - Surface Barrier Detector and PIN photodiodes). A mixed converter made of a borated polyethylene foil (Kodak) was also used. Monte Carlo simulation methodology was employed to evaluate analytically the optimal paraffin thickness. The obtained results were similar to the experimental data and allowed the evaluation of emerging neutron flux from moderator, as well as the fast neutron flux reaching the polyethylene covering the semiconductor sensitive surface. Gamma radiation levels were evaluated covering the whole detector with cadmium foil 1 mm thick, allowing thermal neutrons blockage and gamma radiation measurements. The IPEN/MB-01 facility was employed to evaluate the detector response for high neutron flux. The results were in good agreement with other studies published. Using the obtained spectra an approach to dose equivalent calculation was established. (author)

  17. Angle Software for Semiconductor Detector Gamma-Efficiency Calculations: Applicability to Reactor Neutron Flux Characterization

    International Nuclear Information System (INIS)

    Angle software for semiconductor detector efficiency calculations in its various forms has been in use for 15 years now in numerous gamma-spectrometry based analytical laboratories all around. It goes about a semi-empirical approach, which combines advantages of both absolute and relative methods to determining sample activity by gamma-spectrometry, while conciliating and minimizing their drawbacks. Physical model behind is the concept of the effective solid angle - a parameter calculated upon the input data on geometrical, physical and chemical (composition) characteristics of (1) the source (incl. its container vessel), (2) the detector (incl. crystal housing and end-cap) and (3) counting arrangement (incl. intercepting layers between the latter two). It was shown earlier that only simultaneous differential treatment of gamma attenuation, counting geometry and detector response, as is the case with Angle, is essentially justified for this type of calculations. Attempting the other-way-round, i.e. to separately calculate these three phenomena, generally lead to (over)simplifications, which further require complex corrections with limited success. The program can be applied to practically all situations encountered in gamma-laboratory practice: point, disc, cylindrical or Marinelli samples, small and large, of any matrix composition. No standards are required, but a start-up 'reference efficiency curve' should be obtained (''once for ever'') by measuring a set of calibrated point sources at a large source-to-detector distance (e.g. 20-30cm, to avoid true coincidence effects). Calibration sources are chosen to cover gamma-energy region of analytical interest (e.g. 50-3000 keV). This initial effort is largely paid back in future exploitation. Briefly, ANGLE is characterized by (1) a broad application range, (2) good accuracy for this type of calculations (of a few percent order), (3) comfortable data manipulation (Windows), (4) short computation times, (5

  18. Development of Three-Dimensional Position-Sensitive Room Temperature Semiconductor Gamma-Ray Spectrometers

    International Nuclear Information System (INIS)

    Semiconductor detectors can provide better spectroscopic performance than scintillation or gas-filled detectors because of the small ionization energy required to generate each electron-hole pair. Indeed, cryogenically cooled high-purity germanium detectors have played the dominant role whenever the best gamma-ray spectroscopy is required. A decades-long search for other semiconductor detectors that could provide higher stopping power and could operate at room temperature has been ongoing. Wide-bandgap semiconductors, such as CdTe, CdZnTe, and HgI2, have captured the most attention. However, the use of these semiconductors in detectors has been hindered primarily by problems of charge trapping and material nonuniformity. Introduced in 1994, single-polarity charge sensing on semiconductor detectors has shown great promise in avoiding the hole-trapping problem, and the newly demonstrated three-dimensional position-sensing technique can significantly mitigate the degradation of energy resolution due to nonuniformity of detector material. In addition, three-dimensional position sensitivity will provide unique imaging capabilities of these gamma-ray spectrometers. These devices are of interest for nuclear nonproliferation, medical imaging, gamma-ray astronomy, and high-energy physics applications. This paper describes the three-dimensional position-sensing method and reports our latest results using second-generation three-dimensional position-sensitive semiconductor spectrometers

  19. Development of neutron/gamma generators and a polymer semiconductor detector for homeland security applications

    Science.gov (United States)

    King, Michael Joseph

    -energetic gamma generators that operate at low-acceleration energies and leverage neutron generator technologies. The dissertation focused on the experimental characterization of the generator performance and involved MCNPX simulations to evaluate and analyze the experimental results. The emission of the 11.7 MeV gamma-rays was observed to be slightly anisotropic and the gamma yield was measured to be 2.0*105 gamma/s-mA. The lanthanum hexaboride target suffered beam damage from a high power density beam; however, this may be overcome by sweeping the beam across a larger target area. The efficient detection of fast neutrons is vital to active interrogation techniques for the detection of both SNM and explosives. Novel organic semiconductors are air-stable, low-cost materials that demonstrate direct electronic particle detection. As part of the development of a pi-conjugated organic polymer for fast neutron detection, charge generation and collection properties were investigated. By devising a dual, thin-film detector test arrangement, charge collection was measured for high energy protons traversing the dual detector arrangement that allowed the creation of variable track lengths by tilting the detector. The results demonstrated that an increase in track length resulted in a decreased signal collection. This can be understood by assuming charge carrier transport along the track instead of along the field lines, which was made possible by the filling of traps. However, this charge collection mechanism may be insufficient to generate a useful signal. This dissertation has explored the viability of a new generation of radiation sources and detectors, where the newly developed ion source technologies and prototype generators will further enhance the capabilities of existing threat detection systems and promote the development of cutting-edge detection technologies.

  20. Thin film cadmium telluride charged particle sensors for large area neutron detectors

    Energy Technology Data Exchange (ETDEWEB)

    Murphy, J. W.; Smith, L.; Calkins, J.; Mejia, I.; Cantley, K. D.; Chapman, R. A.; Quevedo-Lopez, M.; Gnade, B., E-mail: gnade@utdallas.edu [Materials Science and Engineering, University of Texas at Dallas, Richardson, Texas 75080 (United States); Kunnen, G. R.; Allee, D. R. [Flexible Display Center, Arizona State University, Phoenix, Arizona 85284 (United States); Sastré-Hernández, J.; Contreras-Puente, G. [Escuela Superior de Física y Matemáticas, Instituto Politécnico Nacional, Mexico City 07738 (Mexico); Mendoza-Pérez, R. [Universidad Autónoma de la Ciudad de México, Mexico City 09790 (Mexico)

    2014-09-15

    Thin film semiconductor neutron detectors are an attractive candidate to replace {sup 3}He neutron detectors, due to the possibility of low cost manufacturing and the potential for large areas. Polycrystalline CdTe is found to be an excellent material for thin film charged particle detectors—an integral component of a thin film neutron detector. The devices presented here are characterized in terms of their response to alpha and gamma radiation. Individual alpha particles are detected with an intrinsic efficiency of >80%, while the devices are largely insensitive to gamma rays, which is desirable so that the detector does not give false positive counts from gamma rays. The capacitance-voltage behavior of the devices is studied and correlated to the response due to alpha radiation. When coupled with a boron-based neutron converting material, the CdTe detectors are capable of detecting thermal neutrons.

  1. Low-noise front-end electronics for semiconductor x-ray and gamma-ray detectors

    International Nuclear Information System (INIS)

    This thesis deals with improving the performance of semiconductor X-ray and gamma-ray detection systems with the help of low-noise analog electronics. Several methods were used to improve the performance of the detection systems: using optimum preamplifier topologies, cooling the detector and input FET in order to reduce leakage currents and noise, using low-noise JFETS as input devices of the preamplifier, matching the JFET capacitance as closely as possible with the detector capacitance, using good-quality low-loss materials for mounting the detector and the JFET in order minimize the dielectric noise, and using rise-time discrimination at the pulse-shaping amplifier in order to reduce the effect of photon events that have experienced charge carrier trapping in the detector materials

  2. Measurement stand for diagnosis of semiconductor detectors based on IBM PC/XT computer (4-way spectrometric analysis of pulses)

    International Nuclear Information System (INIS)

    The technical assumptions and partial realization of our technological stand for quality inspection of semiconductor detectors for ionizing radiation manufactured in the INP in Cracow are described. To increase the efficiency of the measurements simultaneous checking of 4 semiconductor chips or finished products is suggested. In order to justify this measurement technique a review of possible variants of the measurement apparatus is presented for the systems consisting of home made units. Comparative parameters for the component modules and for complete measuring systems are given. The construction and operation of data acquisition system based on IBM PC/XT are described. The system ensures simultaneous registration of pulses obtained from 4 detectors with maximal rate of up to 500 x 103 pulses/s. 42 refs., 6 figs., 3 tabs. (author)

  3. Triggering on hadronic tau decays in ATLAS: Semiconductor tracking detectors in action

    International Nuclear Information System (INIS)

    Identifying the decay of the hadronic tau leptons plays a crucial role in the search for physics beyond the Standard Model as well as in Standard Model measurements. However, these decays are difficult to identify and trigger on due to their resemblance to QCD jets. Given the large production cross-section of QCD processes, designing and operating a trigger system with the capability to efficiently select hadronic tau decays, while maintaining the rate within the bandwidth limits, is a difficult challenge. This contribution will summarize the status and performance of the ATLAS tau trigger system during the 2011 data taking period, emphasizing the key role of semiconductor tracking detectors for tracking and vertexing. Different methods that have been explored to obtain the trigger efficiency curves from data will be shown. Finally, in light of the vast statistics collected in 2011, future prospects for triggering on hadronic tau decays in this exciting new period of increased instantaneous luminosity will be presented. -- Highlights: ► The ATLAS Tau trigger successfully operated during the 2011 run. ► Tracking is a core part of the triggering process of ATLAS. ► The system attained very high levels of efficiency for track reconstruction. ► Data/simulation comparisons of tau trigger show very good agreement.

  4. Diagnostic analysis of silicon strips detector readout in the ATLAS Semi-Conductor Tracker module production

    International Nuclear Information System (INIS)

    The ATLAS Semi-Conductor Tracker (SCT) Collaboration is currently in the production phase of fabricating and testing silicon strips modules for the ATLAS detector at the Large Hadron Collider being built at the CERN laboratory in Geneva, Switzerland. A small but relevant percentage of ICs developed a new set of defects after being mounted on hybrids that were not detected in the wafer screening. To minimize IC replacement and outright module failure, analysis methods were developed to study IC problems during the production of SCT modules. These analyses included studying wafer and hybrid data correlations to finely tune the selection of ICs and tests to utilize the ability to adjust front-end parameters of the IC in order to reduce the rejection and replacement rate of fabricated components. This paper will discuss a few examples of the problems encountered during the production of SCT hybrids and modules in the area of ICs performance, and will demonstrate the value of the flexibility built into the ABCD3T chip

  5. Diagnostic analysis of silicon strips detector readout in the ATLAS Semi-Conductor Tracker module production

    CERN Document Server

    Ciocio, Alessandra

    2005-01-01

    The ATLAS Semi-Conductor Tracker (SCT) Collaboration is currently in the production phase of fabricating and testing silicon strips modules for the ATLAS detector at the Large Hadron Collider being built at the CERN laboratory in Geneva, Switzerland. A small but relevant percentage of ICs developed a new set of defects after being mounted on hybrids that were not detected in the wafer screening. To minimize IC replacement and outright module failure, analysis methods were developed to study IC problems during the production of SCT modules. These analyses included studying wafer and hybrid data correlations to finely tune the selection of ICs and tests to utilize the ability to adjust front-end parameters of the IC in order to reduce the rejection and replacement rate of fabricated components. This paper will discuss a few examples of the problems encountered during the production of SCT hybrids and modules in the area of ICs performance, and will demonstrate the value of the flexibility built into the ABCD3T ...

  6. Purification of bismuth (III) iodide for application as radiation semiconductor detector

    Energy Technology Data Exchange (ETDEWEB)

    Ferraz, Caue de Mello; Armelin, Maria Jose A.; Oliveira, Rene Ramos de; Martins, Joao F. Trencher; Omi, Nelson M.; Hamada, Margarida M., E-mail: cauemferraz@gmail.com [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2015-07-01

    This work describes the experimental procedure of a purification method of BiI{sub 3} powder, aiming a future application of these semiconductor crystals as room temperature radiation detector. The Repeated Vertical Bridgman Technique applied to the purification, based on the melting and nucleation phenomena. An ampoule filled with a maximum of 25% by volume of BiI{sub 3} powder mounted into the Bridgman furnace and vertically moved at a speed of 2 millimeters per hour, inside the furnace with programmed thermal gradient and temperature profile, at a maximum temperature of 530 deg C. The reduction of the impurities in the BiI, after each purification procedure, analyzed by the Instrumental Neutron Activation Analysis (IINAA), in order to evaluate the efficiency of the purification technique established in this work, to trace metal impurities. It demonstrated that the Repeated Bridgman is effective to reduce the concentration of many impurities in BiI{sub 3}, such as Ag, As, Br, Cr, K, Mo, Na and Sb. The crystalline structure of the BiI{sub 3} crystal purified twice and three times was similar to the BiI{sub 3} pattern. However, for BiI{sub 3} powder and purified once, an intensity contribution of BiOI observed in the diffractograms. (author)

  7. Calibration of Ge(Li) semiconductor detector by method using agar volume source

    International Nuclear Information System (INIS)

    The Ge(Li) semiconductor detector was calibrated for measurements of environmental samples. The radioisotopes used for standard sources are 22Na, 51Cr, 56Co, 57Co, 133Ba, 137Cs, 144Ce and 241Am. These are mixed with hot agar aqueous solution and fixed uniformly in a cylindrical plastic case in cooling. The agar volume source is advantageous in handling over the fluid aqueous source. The prepared cylindrical standard sources are in diameters 6 and 8 cm and thicknesses 1, 5, 10, 20, 30 and 40 mm (only for 8 cm diameter). The radioactivities of prepared standard sources are between 0.03 μCi and 0.2 μCi. It takes only a week to make the calibration except data processing. The obtained full energy peak efficiency curves include 5 - 10% error due to preparation of agar source, reference radioactivity data of purchased standard solutions, reference data of branching ratio of gamma-ray and sum effect. The efficiency curves, however, are sufficient for quantitative analysis of environmental samples. (author)

  8. Purification of bismuth (III) iodide for application as radiation semiconductor detector

    International Nuclear Information System (INIS)

    This work describes the experimental procedure of a purification method of BiI3 powder, aiming a future application of these semiconductor crystals as room temperature radiation detector. The Repeated Vertical Bridgman Technique applied to the purification, based on the melting and nucleation phenomena. An ampoule filled with a maximum of 25% by volume of BiI3 powder mounted into the Bridgman furnace and vertically moved at a speed of 2 millimeters per hour, inside the furnace with programmed thermal gradient and temperature profile, at a maximum temperature of 530 deg C. The reduction of the impurities in the BiI, after each purification procedure, analyzed by the Instrumental Neutron Activation Analysis (IINAA), in order to evaluate the efficiency of the purification technique established in this work, to trace metal impurities. It demonstrated that the Repeated Bridgman is effective to reduce the concentration of many impurities in BiI3, such as Ag, As, Br, Cr, K, Mo, Na and Sb. The crystalline structure of the BiI3 crystal purified twice and three times was similar to the BiI3 pattern. However, for BiI3 powder and purified once, an intensity contribution of BiOI observed in the diffractograms. (author)

  9. Microscopic defect level characterization of semi-insulating compound semiconductors by TSC and PICTS. Application to the effect of hydrogen in CdTe

    Science.gov (United States)

    Hage-Ali, M.; Yaacoub, B.; Mergui, S.; Samimi, M.; Biglari, B.; Siffert, P.

    1991-06-01

    Thermally stimulated current (TSC) and photo-induced current transient spectroscopy (PICTS) methods have been developed for the microscopic defect characterization in semi-insulating compound semiconductors. The capabilities of these methods are demonstrated by investigating the effects of hydrogen implantation or diffusion into semi-insulating cadmium telluride.

  10. CdTe and related compounds: physics, defects, hetero- and nano-structures, crystal growth, surfaces and applications

    CERN Document Server

    Triboulet, Robert

    Almost thirty years after the remarkable monograph of K. Zanio and the numerous conferences and articles dedicated since that time to CdTe and CdZnTe, after all the significant progresses in that field and the increasing interest in these materials for several extremely attractive industrial applications, such as nuclear detectors and solar cells, the edition of a new enriched and updated monograph dedicated to these two very topical II-VI semiconductor compounds, covering all their most prominent, modern and fundamental aspects, seemed very relevant and useful.

  11. Multidirectional channeling analysis of epitaxial CdTe layers using an automatic RBS/channeling system

    Energy Technology Data Exchange (ETDEWEB)

    Wielunski, L.S.; Kenny, M.J. [CSIRO, Lindfield, NSW (Australia). Applied Physics Div.

    1993-12-31

    Rutherford Backscattering Spectrometry (RBS) is an ion beam analysis technique used in many fields. The high depth and mass resolution of RBS make this technique very useful in semiconductor material analysis [1]. The use of ion channeling in combination with RBS creates a powerful technique which can provide information about crystal quality and structure in addition to mass and depth resolution [2]. The presence of crystal defects such as interstitial atoms, dislocations or dislocation loops can be detected and profiled [3,4]. Semiconductor materials such as CdTe, HgTe and Hg+xCd{sub 1-x}Te generate considerable interest due to applications as infrared detectors in many technological areas. The present paper demonstrates how automatic RBS and multidirectional channeling analysis can be used to evaluate crystal quality and near surface defects. 6 refs., 1 fig.

  12. Design of a hybrid gas proportional counter with CdTe guard counters for sup 1 sup 4 C dating system

    CERN Document Server

    Zhang, L; Hinamoto, N; Nakazawa, M; Yoshida, K

    2002-01-01

    Nowadays uniform, low-cost and large-size compound semiconductor detectors are available up to several square centimeters. We are trying to combine this technology with conventional gas detectors to upgrade an anticoincidence type proportional counter, Oeschger-type thin wall counter of 2.2 l, used for a sup 1 sup 4 C dating facility at the University of Tokyo. In order to increase the ratio of the signal to the background for smaller quantity of samples less than 1 g, an effective approach is to minimize the detector volume at higher gas pressure. However, the anticoincidence function suffers from such a small volume. Therefore we designed a new active wall gas counter of 0.13 l counting volume using CdTe compound semiconductor detectors as the wall of the gas proportional counter to perform anticoincidence. Simulation study showed that at noise thresholds less than 70 keV, the wall counters can reject above 99.8% of events arising from outer gamma rays. Measured noise levels of CdTe detectors were smaller t...

  13. Medipix2 based CdTe microprobe for dental imaging

    International Nuclear Information System (INIS)

    Medical imaging devices and techniques are demanded to provide high resolution and low dose images of samples or patients. Hybrid semiconductor single photon counting devices together with suitable sensor materials and advanced techniques of image reconstruction fulfil these requirements. In particular cases such as the direct observation of dental implants also the size of the imaging device itself plays a critical role. This work presents the comparison of 2D radiographs of tooth provided by a standard commercial dental imaging system (Gendex 765DC X-ray tube with VisualiX scintillation detector) and two Medipix2 USB Lite detectors one equipped with a Si sensor (300 μm thick) and one with a CdTe sensor (1 mm thick). Single photon counting capability of the Medipix2 device allows virtually unlimited dynamic range of the images and thus increases the contrast significantly. The dimensions of the whole USB Lite device are only 15 mm × 60 mm of which 25% consists of the sensitive area. Detector of this compact size can be used directly inside the patients' mouth.

  14. Dual radioisotopes simultaneous SPECT of 99mTc-tetrofosmin and 123I-BMIPP using a semiconductor detector.

    Directory of Open Access Journals (Sweden)

    Yasuyuki Takahashi

    2015-01-01

    Full Text Available Objective(s: The energy resolution of a cadmium-zinc-telluride (CZT solid-state semiconductor detector is about 5%, and is superior to the resolution of the conventional Anger type detector which is 10%. Also, the window width of the high-energy part and of the low-energy part of a photo peak window can be changed separately. In this study, we used a semiconductor detector and examined the effects of changing energy window widths for 99mTc and 123 I simultaneous SPECT. Methods: The energy “centerline” for 99mTc was set at 140.5 keV and that for 123I at 159.0 keV. For 99mTc, the “low-energy-window width” was set to values that varied from 3% to 10% of 140.5 keV and the “high-energy-window width” were independently set to values that varied from 3% to 6% of 140.5 keV. For 123I, the “low energy-window-width” varied from 3% to 6% of 159.0 keV and the high-energy-window width from 3% to 10% of 159 keV. In this study we imaged the cardiac phantom, using single or dual radionuclide, changing energy window width, and comparing SPECT counts as well as crosstalk ratio. Results: The contamination to the 123I window from 99mTc (the crosstalk was only 1% or less with cutoffs of 4% at lower part and 6% at upper part of 159KeV. On the other hand, the crosstalk from 123I photons into the 99mTc window mostly exceeded 20%. Therefore, in order to suppress the rate of contamination to 20% or less, 99mTc window cutoffs were set at 3% in upper part and 7% at lower part of 140.5 KeV. The semiconductor detector improves separation accuracy of the acquisition inherently at dual radionuclide imaging. In, this phantom study we simulated dual radionuclide simultaneous SPECT by 99mTc-tetrofosmin and 123 I-BMIPP. Conclusion: We suggest that dual radionuclide simultaneous SPECT of 99mTc and 123I using a CZT semiconductor detector is possible employing the recommended windows.

  15. Exploration of Pixelated detectors for double beta decay searches within the COBRA experiment

    International Nuclear Information System (INIS)

    The aim of the COBRA experiment is the search for neutrinoless double beta decay events in Cadmium Zinc Telluride (CdZnTe) room temperature semiconductor detectors. The development of pixelated detectors provides the potential for clear event identification and thus major background reduction. The tracking option of a semiconductor is a unique approach in this field. For initial studies, several possible detector systems are considered with a special regard for low background applications: the large volume system Polaris with a pixelated CdZnTe sensor, Timepix detectors with Si and enriched CdTe sensor material and a CdZnTe pixel system developed at the Washington University in St. Louis, USA. For all detector systems first experimental background measurements taken at underground laboratories (Gran Sasso Underground Laboratory in Italy, LNGS and the Niederniveau Messlabor Felsenkeller in Dresden, Germany) and additionally for the Timepix detectors simulation results are presented.

  16. Exploration of Pixelated detectors for double beta decay searches within the COBRA experiment

    Energy Technology Data Exchange (ETDEWEB)

    Schwenke, M., E-mail: schwenke@asp.tu-dresden.de [Institut fuer Kern- und Teilchenphysik, Technische Universitaet Dresden, Zellescher Weg 19, 01069 Dresden (Germany); Zuber, K.; Janutta, B. [Institut fuer Kern- und Teilchenphysik, Technische Universitaet Dresden, Zellescher Weg 19, 01069 Dresden (Germany); He, Z.; Zeng, F. [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, Michigan 48109-2104 (United States); Anton, G.; Michel, T.; Durst, J.; Lueck, F.; Gleixner, T. [Erlangen Centre for Astroparticle Physics, Friedrich-Alexander-Universitaet Erlangen-Nuernberg, Erwin-Rommel-Str. 1, 91058 Erlangen (Germany); Goessling, C.; Schulz, O.; Koettig, T. [Technische Universitaet Dortmund, Physik E IV, 44221 Dortmund (Germany); Krawczynski, H.; Martin, J. [Department of Physics, Washington University in St. Louis, Campus Box 1105, One Brookings Drive, St. Louis, MO 63130-4899 (United States); Stekl, I.; Cermak, P. [Institute of Experimental and Applied Physics, Czech Technical University in Prague, Horska 3a/22, 128 00 Prague (Czech Republic)

    2011-09-11

    The aim of the COBRA experiment is the search for neutrinoless double beta decay events in Cadmium Zinc Telluride (CdZnTe) room temperature semiconductor detectors. The development of pixelated detectors provides the potential for clear event identification and thus major background reduction. The tracking option of a semiconductor is a unique approach in this field. For initial studies, several possible detector systems are considered with a special regard for low background applications: the large volume system Polaris with a pixelated CdZnTe sensor, Timepix detectors with Si and enriched CdTe sensor material and a CdZnTe pixel system developed at the Washington University in St. Louis, USA. For all detector systems first experimental background measurements taken at underground laboratories (Gran Sasso Underground Laboratory in Italy, LNGS and the Niederniveau Messlabor Felsenkeller in Dresden, Germany) and additionally for the Timepix detectors simulation results are presented.

  17. Microbial toxicity of ionic species leached from the II-VI semiconductor materials, cadmium telluride (CdTe) and cadmium selenide (CdSe).

    Science.gov (United States)

    Ramos-Ruiz, Adriana; Zeng, Chao; Sierra-Alvarez, Reyes; Teixeira, Luiz H; Field, Jim A

    2016-11-01

    This work investigated the microbial toxicity of soluble species that can potentially be leached from the II-VI semiconductor materials, cadmium telluride and cadmium selenide. The soluble ions tested included: cadmium, selenite, selenate, tellurite, and tellurate. Their toxicity towards the acetoclastic and hydrogen-consuming trophic groups in a methanogenic consortium as well as towards a bioluminescent marine bacterium, Aliivibrio fischeri (Microtox(®) test), was assessed. The acetoclastic methanogenic activity was the most affected as evidenced by the low 50% inhibiting concentrations (IC50) values obtained of 8.6 mg L(-1) for both cadmium and tellurite, 10.2 mg L(-1) for tellurate, and 24.1 mg L(-1) for selenite. Both tellurium oxyanions caused a strong inhibition of acetoclastic methanogenesis at low concentrations, each additional increment in concentration provided progressively less inhibition increase. In the case of the hydrogenotrophic methanogenesis, cadmium followed by selenite caused the greatest inhibition with IC50 values of 2.9 and 18.0 mg L(-1), respectively. Tellurite caused a moderate effect as evidenced by a 36.8% inhibition of the methanogenic activity at the highest concentration tested, and a very mild effect of tellurate was observed. Microtox(®) analyses showed a noteworthy inhibition of cadmium, selenite, and tellurite with 50% loss in bioluminescence after 30 min of exposure of 5.5, 171.1, and 458.6 mg L(-1), respectively. These results suggest that the leaching of cadmium, tellurium and selenium ions from semiconductor materials can potentially cause microbial toxicity. PMID:27494313

  18. Multichannel, time-resolved picosecond laser ultrasound imaging and spectroscopy with custom complementary metal-oxide-semiconductor detector

    International Nuclear Information System (INIS)

    This paper presents a multichannel, time-resolved picosecond laser ultrasound system that uses a custom complementary metal-oxide-semiconductor linear array detector. This novel sensor allows parallel phase-sensitive detection of very low contrast modulated signals with performance in each channel comparable to that of a discrete photodiode and a lock-in amplifier. Application of the instrument is demonstrated by parallelizing spatial measurements to produce two-dimensional thickness maps on a layered sample, and spectroscopic parallelization is demonstrated by presenting the measured Brillouin oscillations from a gallium arsenide wafer. This paper demonstrates the significant advantages of our approach to pump probe systems, especially picosecond ultrasonics.

  19. Single-charge-carrier-type sensing with an insulated Frisch ring CdZnTe semiconductor radiation detector

    International Nuclear Information System (INIS)

    Performance optimization of an insulated Frisch ring design was investigated for a 3x3x6 mm CdZnTe planar semiconductor detector. The Frisch ring was composed of copper and was insulated from the detector surface with Teflon. Optimization variables included the Frisch ring length and the bias voltage. Optimized overall device performance was found using a 5 mm long Frisch ring extending from the cathode toward the anode, leaving a 1 mm separation between the Frisch ring and the anode. The best energy resolution observed was 1.7% full width at half maximum at 662 keV with the ring extending 4 mm from the cathode toward the anode

  20. SOI metal-oxide-semiconductor field-effect transistor photon detector based on single-hole counting.

    Science.gov (United States)

    Du, Wei; Inokawa, Hiroshi; Satoh, Hiroaki; Ono, Atsushi

    2011-08-01

    In this Letter, a scaled-down silicon-on-insulator (SOI) metal-oxide-semiconductor field-effect transistor (MOSFET) is characterized as a photon detector, where photogenerated individual holes are trapped below the negatively biased gate and modulate stepwise the electron current flowing in the bottom channel induced by the positive substrate bias. The output waveforms exhibit clear separation of current levels corresponding to different numbers of trapped holes. Considering this capability of single-hole counting, a small dark count of less than 0.02 s(-1) at room temperature, and low operation voltage of 1 V, SOI MOSFET could be a unique photon-number-resolving detector if the small quantum efficiency were improved. PMID:21808317

  1. X-ray diffuse scattering for evaluation of wide bandgap semiconductor nuclear radiation detectors

    International Nuclear Information System (INIS)

    The crystalline perfection of solid state radiation detectors was examined using triple axis x-ray diffraction. Triple axis techniques provide a means to analyze the origin of diffraction peak broadening: the effects of strain (due to deviations in alloy composition or stoichiometry) and lattice tilts (mosaic structure) can be separated. Cd1-xZnxTe (x∼0.1), HgI2, and GaAs detector materials were studied. In the cases of Cd1-xZnxTe and HgI2 the crystalline properties of detectors with different spectral responses to γ-radiation were determined. Increased mosaicity was universally found to be related to deteriorated detector properties. For Cd1-xZnxTe, detectors with poor performance possessed greater levels of diffuse scatter due to lattice tilts than did high quality detectors. For GaAs, low angle grain boundaries were attributed to impaired detector performance. Additionally, in large HgI2 detectors, deviations from stoichiometry were also related to reduced performance. Interestingly, HgI2 detectors which possessed a sharp spectral response to γ-radiation but also showed polarization were of comparable crystallinity to those detectors which did not exhibit polarization effects. This initial analysis suggests that polarization is related to native point defects or chemical impurities which do not significantly alter the crystallinity of the material. Overall, within a given class of materials, improved detector performance (better spectral response) always correlated with better material quality. (orig.)

  2. MIS structure as a N-P junction and an electrode of a cadmium telluride nuclear detector

    International Nuclear Information System (INIS)

    The surface of a high resistivity CdTe is investigated by AES and ELS. The ELS spectra have demonstrated the presence of TeO2 layer on an outer side of the electrochemically etching surface. The interface TeO2/CdTe represents thick region of inverse or depleted conductivity. The thickness of TeO2 layer can be reduced by anodic treatment. By evaporating a metallic layer the metal-oxide-semiconductor structure is obtained. The electrical characteristics of a metal-CdTe surface are as of a MIS structure ones and an electrode of a nuclear detector. The advantage of such detector with a metal-dielectric-semiconductor electrode is emphasized. 9 refs., 5 figs. (orig.)

  3. Analysis and modelling of the performance of a new solid-state detector in nuclear medicine: from Anger- to Semiconductor-detectors

    International Nuclear Information System (INIS)

    Myocardial single-photon emission computed tomography (SPECT) is considered as the gold standard for the diagnosis of coronary artery disease. Developed in the 1980's with rotating Anger gamma cameras, this technique could be dramatically enhanced by new imaging systems working with semiconductor detectors and which performances are clearly enhanced. Two semiconductor cameras, dedicated to nuclear cardiology and equipped with Cadmium Zinc Telluride detectors, have been recently commercialized: the Discovery NM- 530c (General Electric) and the DSPECT (Spectrum Dynamics). The performances of these CZT cameras were compared: 1) by a comprehensive analysis of phantom and human SPECT images considered as normal and 2) with the parameters commonly recommended for SPECT recording and reconstruction. The results show the superiority of the CZT cameras in terms of detection sensitivity, spatial resolution and contrast-to-noise ratio, compared to conventional Anger cameras. These properties might lead to dramatically reduce acquisition times and/or the injected activities. However, the limits of these new CZT cameras, as well as the mechanism of certain artefacts, remain poorly known. This knowledge could be enhanced by a numerical modeling of the DSPECT camera, and this might also help to optimize acquisition and reconstruction parameters. We developed a simulator where the geometry of the detectors of the DSPECT camera and their energy response were modeled in the GATE platform. In order to validate this simulator, actually recorded data were compared with simulated data through three performance parameters: detection sensitivity, spatial resolution and energy resolution. Results were in agreement between simulated and actually recorded data. This observation validates the DSPECT simulator and opens the door to further studies planed to optimize the recorded and reconstruction processes, especially for complex protocols such as simultaneous dual-radionuclide acquisition

  4. Radiation detectors: needs and prospects

    International Nuclear Information System (INIS)

    Important applications for x- and γ-ray spectroscopy are found in prospecting, materials characterization, environmental monitoring, the life sciences, and nuclear physics. The specific requirements vary for each application with varying degrees of emphasis on either spectrometer resolution, detection efficiency, or both. Since no one spectrometer is ideally suited to this wide range of needs, compromises are usually required. Gas and scintillation spectrometers have reached a level of maturity, and recent interest has concentrated on semiconductor spectrometers. Germanium detectors are showing continuing refinement and are the spectrometers of choice for high resolution applications. The new high-Z semiconductors, such as CdTe and HgI2, have shown steady improvement but are limited in both resolution and size and will likely be used only in applications which require their unique properties

  5. Semiconductor arrays for nuclear medicine imaging

    International Nuclear Information System (INIS)

    Full text: Gamma-ray imaging of an injected radiotracer is used in nuclear medicine to determine organ function or locate the site of pathology such as cancer. Current gamma cameras use scintillation detectors with analog position estimation and are characterized by poor spatial resolution (0.4 cm) and poor energy resolution (11% FWHM at 140 keV). Energy resolution is important for suppressing the effects of Compton scattering in tissue. Single photon emission computed tomography (SPECT) is used to generate a three-dimensional representation of the source distribution. Another technique, positron emission tomography (PET), images the annihilation radiation from a positron emitter but is more costly than SPECT and is less widely available. Arrays of semiconductor detectors have long been considered an attractive alternative to scintillators for use in gamma cameras. Semiconductor detectors have excellent energy resolution and can be fabricated into large arrays of small pixel size and thus good spatial resolution using photolithography techniques. The best semiconductor detectors are Si and Ge, but these are less attractive for nuclear medicine purposes because of low gamma-ray stopping power or the need for expensive cryogenics. Most interest has centered on room-temperature semiconductor detectors such as CdTe and HgI2. However, until now, the main use of semiconductors in nuclear medicine has been as detectors in probes used to locate radiotracer-labelled tumors or other pathology at surgery or endoscopy. There are a number of reasons why a practical semiconductor camera has not yet been developed: semiconductor detectors are very expensive. Large detector areas (0.1 - 0.2 square meter) will be required for a camera. Electronics for reading out as many as a million separate detector pixels must be provided. Room-temperature semiconductor detectors suffer from charge carrier trapping that limits their useful efficiency. Current multibore collimators must trade off

  6. Adsorption smoke detector made of thin-film metal-oxide semiconductor sensor

    International Nuclear Information System (INIS)

    Based on results of investigations of the thin-film smoke sensors made of Bi2O3, irresponsive to a change in relative humidity of the environment, an absorption smoke detector processing circuit, where investigated sensor is used as a sensitive element, is proposed. It is shown that such smoke detector is able to function reliably under conditions of high relative humidity of the environment (up to 100%) and it considerably exceeds the known smoke detectors by the sensitivity threshold

  7. Adsorption smoke detector made of thin-film metal-oxide semiconductor sensor

    CERN Document Server

    Adamian, A Z; Aroutiounian, V M

    2001-01-01

    Based on results of investigations of the thin-film smoke sensors made of Bi sub 2 O sub 3 , irresponsive to a change in relative humidity of the environment, an absorption smoke detector processing circuit, where investigated sensor is used as a sensitive element, is proposed. It is shown that such smoke detector is able to function reliably under conditions of high relative humidity of the environment (up to 100%) and it considerably exceeds the known smoke detectors by the sensitivity threshold.

  8. Performance of thallium bromide semiconductor detectors produced by repeated Bridgman method

    International Nuclear Information System (INIS)

    TlBr crystals have been grown by the Repeated Bridgman method from commercial TlBr materials and characterized to be used as radiation detectors. We have shown that the Repeated Bridgman is effective to reduce the concentration of impurities in TlBr. It was observed that detectors fabricated from higher purity crystal exhibit significant improvement in performance compared to those produced from low purity crystals. However, problems still exist in TlBr detectors, due to the low charge carrier collection efficiency, which is probably caused by additional impurities or defects incorporated during crystal growth and detector fabrication processes. (author)

  9. Characterization of electroless Au, Pt and Pd contacts on CdTe and ZnTe by RBS and SIMS techniques

    International Nuclear Information System (INIS)

    Rutherford backscattering spectrometry (RBS) was applied to characterize Au, Pt and Pd contacts on II-VI semiconductor materials, CdTe and ZnTe, used as nuclear detectors. Electroless thin film depositions were prepared by changing the concentration of the reaction solution. Contrary to the deposition reaction time, it was observed that the amount of solution dilution degree had a considerable effect on increasing the thickness of the metal layer. Furthermore, PICTS electrical measurements confirmed the depth profile analysis performed by RBS and SIMS

  10. K-mean clustering algorithm for processing signals from compound semiconductor detectors

    International Nuclear Information System (INIS)

    The K-mean clustering algorithm was employed for processing signal waveforms from TlBr detectors. The signal waveforms were classified based on its shape reflecting the charge collection process in the detector. The classified signal waveforms were processed individually to suppress the pulse height variation of signals due to the charge collection loss. The obtained energy resolution of a 137Cs spectrum measured with a 0.5 mm thick TlBr detector was 1.3% FWHM by employing 500 clusters.

  11. Recent advances in the development of semiconductor detectors for very high luminosity colliders

    International Nuclear Information System (INIS)

    For the luminosity upgrade of the LHC, the SLHC, the tracking systems of the LHC experiments need to be replaced. A main concern is the extreme radiation hardness requirement up to 1x1016cm-2 1 MeV neutron equivalent. This paper describes an extract of recent results on radiation hardening technologies developed within the RD50 Collaboration (http://www.cern.ch/rd50) for the tracker upgrades. Silicon detectors have been designed and produced on n- and p-type wafers made by Float Zone, epitaxy and Czochralski technology. Their charge collection efficiency after proton, neutron and mixed irradiation has been studied. Novel detector concepts, as 3D detectors, have been designed, produced and studied as well. Radiation induced microscopic disorder has been also investigated and correlated with the performance degradation of irradiated detectors.

  12. Development of TiBr semiconductor crystal for applications as radiation detector and photodetector

    International Nuclear Information System (INIS)

    In this work, Tlbr crystals were grown by the Bridgman method from zone melted materials. The influence of the purification efficiency and the crystalline surface quality on the crystal were studied, evaluating its performance as a radiation detector. Due to significant improvement in the purification and crystals growth, good results have been obtained for the developed detectors. The spectrometric performance of the Tlbr detector was evaluated by 241Am (59 keV), 133Ba (80 e 355 keV), 57Co (122 keV), 22Na (511 keV) and 137 Cs (662 keV) at room temperature. The best energy resolution results were obtained from purer detectors. Energy resolutions of 10 keV (16%), 12 keV (15%), 12 keV (10%), 28 keV (8%), 31 keV (6%) and 36 keV (5%) to 59, 80, 122, 355, 511 and 662 keV energies, respectively, were obtained. A study on the detection response at -20 deg C was also carried out, as well as the detector stability in function of the time. No significant difference was observed in the energy resolution between measurements at both temperatures. It was observed that the detector instability causes degradation of the spectroscopic characteristics during measurements at room temperature and the instability varies for each detector. This behavior was also verified by other authors. The viability to use the developed Tlbr crystal as a photodetector coupled to scintillators crystals was also studied in this work. Due to its quantum efficiency in the region from 350 to 500 nm, Tlbr shows to be a promising material to be used as a photodetector. As a possible application of this work, the development of a surgical probe has been initiated using the developed Tlbr crystal as the radiation detector of the probe. (author)

  13. High-z semiconductor nuclear radiation detectors for room-temperature gamma-ray spectrometry

    International Nuclear Information System (INIS)

    A bibliographical review (182 articles of periodicals, conferences, reports, thesis and french patents) is presented, as addendum of the report CEA-BIB-210 (1974) on high-Z semiconductor compounds used as materials for the gamma and X-ray detection and spectrometry. This publication reviews issues from 1974 to 1977. References and summaries (in french) are incorporated into 182 bibliograhical notices. Index for authors, corporate authors, documents and periodicals, and subjects is included

  14. Comparison of ionisation chamber and semiconductor detector devices for measurement of the dose–width product for panoramic dental units

    International Nuclear Information System (INIS)

    Doses for panoramic dental radiography are assessed in terms of the dose–width product (DWP) or dose–area product, which gives a measure of the radiation through a whole exposure. The DWP can be measured using a pencil ionisation chamber (IC) similar to that used for computed tomography dose assessment. However, ICs are sensitive to radiation incident from all directions and so backscatter from the image receptor may increase the recorded dose. This study compares measurements performed using four options: a pencil IC mounted straight on the image receptor, the IC mounted with a steel plate to the rear to standardise scatter conditions, the IC mounted with a steel plate and lead collimators in front to minimise the effect of extra-focal radiation, and a Quart Dido employing a one square centimetre semiconductor detector (SD) designed for panoramic measurements. The results indicate that modification of the current method by incorporating a steel plate reduced the measurement dose by 7% on average, but the reduction was greater for units with semiconductor imaging plates. The measurements with the SD agree more closely with the IC with the steel plate to the rear. An IC with a backing plate to standardise scatter or a suitable SD is recommended for measurement on panoramic dental units. (paper)

  15. Study of a new design of p-N semiconductor detector array for nuclear medicine imaging by monte carlo simulation codes.

    Science.gov (United States)

    Hajizadeh-Safar, M; Ghorbani, M; Khoshkharam, S; Ashrafi, Z

    2014-07-01

    Gamma camera is an important apparatus in nuclear medicine imaging. Its detection part is consists of a scintillation detector with a heavy collimator. Substitution of semiconductor detectors instead of scintillator in these cameras has been effectively studied. In this study, it is aimed to introduce a new design of P-N semiconductor detector array for nuclear medicine imaging. A P-N semiconductor detector composed of N-SnO2 :F, and P-NiO:Li, has been introduced through simulating with MCNPX monte carlo codes. Its sensitivity with different factors such as thickness, dimension, and direction of emission photons were investigated. It is then used to configure a new design of an array in one-dimension and study its spatial resolution for nuclear medicine imaging. One-dimension array with 39 detectors was simulated to measure a predefined linear distribution of Tc(99_m) activity and its spatial resolution. The activity distribution was calculated from detector responses through mathematical linear optimization using LINPROG code on MATLAB software. Three different configurations of one-dimension detector array, horizontal, vertical one sided, and vertical double-sided were simulated. In all of these configurations, the energy windows of the photopeak were ± 1%. The results show that the detector response increases with an increase of dimension and thickness of the detector with the highest sensitivity for emission photons 15-30° above the surface. Horizontal configuration array of detectors is not suitable for imaging of line activity sources. The measured activity distribution with vertical configuration array, double-side detectors, has no similarity with emission sources and hence is not suitable for imaging purposes. Measured activity distribution using vertical configuration array, single side detectors has a good similarity with sources. Therefore, it could be introduced as a suitable configuration for nuclear medicine imaging. It has been shown that using

  16. The plasma decay time in semiconductor detectors for energetic heavy ions

    International Nuclear Information System (INIS)

    The decay times tsub(p) of the electron-hole plasma formed in the wake of fission fragments and alpha particles stopped in a number of silicon surface barrier detector are measured from the resulting current pulse rise times. Detector field and fragment mass and energy dependence data are presented for the five detectors used. Use of the field strength Fsub(c) at the charge centroid of the plasma column for both fragments and alphas removes or reduces a systematic detector resistivity dependence observable in the results obtained when the front face maximum detector field F0 is used as a parameter. We obtain tsub(p) approx. equal to Fsub(c)sup(0.85+-0.06) for fragments and tsub(p) approx. equal to Fsub(c)sup(-0.7+-0.1) for alphas. These are slightly weaker field dependences than the commonly used inversely proportional relationship, which we too observe when F0 is used. No appreciable fragment mass dependence is observed, while the fragment energy (E) dependence is tsub(p) approx. equal to Esup(0.47). These results are shown to accord with theoretical expectations. (orig.)

  17. Growth, fabrication, and testing of bismuth tri-iodide semiconductor radiation detectors

    International Nuclear Information System (INIS)

    Bismuth tri-iodide (BiI3) is an attractive material for high energy resolution radiation detectors. For the purpose of this research, detectors were fabricated using single crystals grown from ultra-pure BiI3 powder; synthesized by the Physical Vapor Transport (PVT) technique. This technique yielded powder with total impurity level of 7.9 ppm. Efforts were also made to purify commercial BiI3 powder using a custom-built Traveling Zone Refining (TZR) system. Initial trial runs were successful in reducing the total impurity level of the commercial powder from 200 ppm to less than 50 ppm. Using the modified vertical Bridgman technique and a customized sharp tip ampoule, a large BiI3 single crystal was grown. The crystal had a surface area of 2.2 cm2 and a thickness of 0.8 cm, which corresponds to a volume of 1.78 cm3. Radiation detectors were fabricated and then tested by measuring their electrical characteristics and radiation response. An alpha particle spectrum (using a 241Am α-source) was recorded at room temperature with a BiI3 detector 0.09 cm thick and with a surface area of 0.16 cm2. The electron mobility was estimated to be 433 ± 79 cm2/V. - Highlights: • Ultrapure BiI3 crystal was grown by the modified vertical Bridgman technique. • BiI3 radiation detectors were fabricated and tested. • The ultrapure detectors showed superior electrical characteristics. • Radiation response was measured by recording an α-spectrum at room temperature. • Electron mobility was estimated

  18. Micro and nanophotonics for semiconductor infrared detectors towards an ultimate uncooled device

    CERN Document Server

    Jakšic, Zoran

    2014-01-01

    The advent of microelectromechanic system (MEMS) technologies and nanotechnologies has resulted in a multitude of structures and devices with ultra compact dimensions and with vastly enhanced or even completely novel properties. In the field of photonics it resulted in the appearance of new paradigms, including photonic crystals that exhibit photonic bandgap and represent an optical analog of semiconductors and metamaterials that have subwavelength features and may have almost arbitrary values of effective refractive index, including those below zero. In addition to that, a whole new field of

  19. Investigation of temperature dependence of semiconductor detectors used in medicine for radiation measurements

    OpenAIRE

    Altunkok Simay Ozleyis; Tuncel Nina; Ucar Nazim

    2015-01-01

    In this study, the temperature dependence of p-type semiconductor diodes that are a part of in-vivo dosimetry system was assessed in Co-60 photon energy. The collimator and gantry angle on zero degree, SSD 100 cm, field size 20x20 cm2 was selected. The IBA EDP-5, EDP-10 and EDP-20 diode types that included in this study have different thickness of build-up material so the depth of measurements at water equivalent phantom by FC65-p ion chamber was selected at 5, 10 and 20 mm. Along the process...

  20. Using triple gamma coincidences with a pixelated semiconductor Compton-PET scanner: a simulation study

    Science.gov (United States)

    Kolstein, M.; Chmeissani, M.

    2016-01-01

    The Voxel Imaging PET (VIP) Pathfinder project presents a novel design using pixelated semiconductor detectors for nuclear medicine applications to achieve the intrinsic image quality limits set by physics. The conceptual design can be extended to a Compton gamma camera. The use of a pixelated CdTe detector with voxel sizes of 1 × 1 × 2 mm3 guarantees optimal energy and spatial resolution. However, the limited time resolution of semiconductor detectors makes it impossible to use Time Of Flight (TOF) with VIP PET. TOF is used in order to improve the signal to noise ratio (SNR) by using only the most probable portion of the Line-Of-Response (LOR) instead of its entire length. To overcome the limitation of CdTe time resolution, we present in this article a simulation study using β+-γ emitting isotopes with a Compton-PET scanner. When the β+ annihilates with an electron it produces two gammas which produce a LOR in the PET scanner, while the additional gamma, when scattered in the scatter detector, provides a Compton cone that intersects with the aforementioned LOR. The intersection indicates, within a few mm of uncertainty along the LOR, the origin of the beta-gamma decay. Hence, one can limit the part of the LOR used by the image reconstruction algorithm.

  1. Coal mining applications of CdTe gamma ray sensors

    Energy Technology Data Exchange (ETDEWEB)

    Entine, G.; Tiernan, T.; Waer, P.; Hazlett, T. (Radiation Monitoring Devices, Inc., Watertown, MA (USA))

    1990-01-01

    Cadmium telluride (CdTe) solid-state radiation detectors have been used in the development of instrumentation that improves the efficiency of coal-mining operations by helping to locate coal seams and preventing the mining of high-sulfur coal near the edges of the seam. CdTe detectors were selected for these applications because while they are small and durable, they offer good stopping power, deliver adequate spectral response and operate at low voltage. These CdTe-based instruments have passed the mine-safety standards and are now in operation in the mine. (author).

  2. Coal mining applications of CdTe gamma ray sensors

    International Nuclear Information System (INIS)

    Cadmium telluride (CdTe) solid-state radiation detectors have been used in the development of instrumentation that improves the efficiency of coal-mining operations by helping to locate coal seams and preventing the mining of high-sulfur coal near the edges of the seam. CdTe detectors were selected for these applications because while they are small and durable, they offer good stopping power, deliver adequate spectral response and operate at low voltage. These CdTe-based instruments have passed the mine-safety standards and are now in operation in the mine. (author)

  3. Next Generation Semiconductor-Based Radiation Detectors Using Cadmium Magnesium Telluride

    Energy Technology Data Exchange (ETDEWEB)

    Trivedi, Sudhir B [Brimrose Technology Corporation, Sparks Glencoe, MD (United States); Kutcher, Susan W [Brimrose Technology Corporation, Sparks Glencoe, MD (United States); Palsoz, Witold [Brimrose Technology Corporation, Sparks Glencoe, MD (United States); Berding, Martha [SRI International, Menlo Park, CA (United States); Burger, Arnold [Brimrose Technology Corporation, Sparks Glencoe, MD (United States)

    2014-11-17

    The primary objective of Phase I was to perform extensive studies on the purification, crystal growth and annealing procedures of CdMgTe to gain a clear understanding of the basic material properties to enable production of detector material with performance comparable to that of CdZnTe. Brimrose utilized prior experience in the growth and processing of II-VI crystals and produced high purity material and good quality single crystals of CdMgTe. Processing techniques for these crystals including annealing, mechanical and chemical polishing, surface passivation and electrode fabrication were developed. Techniques to characterize pertinent electronic characteristics were developed and gamma ray detectors were fabricated. Feasibility of the development of comprehensive defect modeling in this new class of material was demonstrated by our partner research institute SRI International, to compliment the experimental work. We successfully produced a CdMgTe detector that showed 662 keV gamma response with energy resolution of 3.4% (FWHM) at room temperature, without any additional signal correction. These results are comparable to existing CdZnTe (CZT) technology using the same detector size and testing conditions. We have successfully demonstrated detection of gamma-radiation from various isotopes/sources, using CdMgTe thus clearly proving the feasibility that CdMgTe is an excellent, low-cost alternative to CdZnTe.

  4. SU-C-201-03: Coded Aperture Gamma-Ray Imaging Using Pixelated Semiconductor Detectors

    Energy Technology Data Exchange (ETDEWEB)

    Joshi, S [Wayne State University, Detroit, MI (United States); Kaye, W; Jaworski, J [H3D, Inc., Ann Arbor, MI (United States); He, Z [University of Michigan, Ann Arbor, MI (United States)

    2015-06-15

    Purpose: Improved localization of gamma-ray emissions from radiotracers is essential to the progress of nuclear medicine. Polaris is a portable, room-temperature operated gamma-ray imaging spectrometer composed of two 3×3 arrays of thick CdZnTe (CZT) detectors, which detect gammas between 30keV and 3MeV with energy resolution of <1% FWHM at 662keV. Compton imaging is used to map out source distributions in 4-pi space; however, is only effective above 300keV where Compton scatter is dominant. This work extends imaging to photoelectric energies (<300keV) using coded aperture imaging (CAI), which is essential for localization of Tc-99m (140keV). Methods: CAI, similar to the pinhole camera, relies on an attenuating mask, with open/closed elements, placed between the source and position-sensitive detectors. Partial attenuation of the source results in a “shadow” or count distribution that closely matches a portion of the mask pattern. Ideally, each source direction corresponds to a unique count distribution. Using backprojection reconstruction, the source direction is determined within the field of view. The knowledge of 3D position of interaction results in improved image quality. Results: Using a single array of detectors, a coded aperture mask, and multiple Co-57 (122keV) point sources, image reconstruction is performed in real-time, on an event-by-event basis, resulting in images with an angular resolution of ∼6 degrees. Although material nonuniformities contribute to image degradation, the superposition of images from individual detectors results in improved SNR. CAI was integrated with Compton imaging for a seamless transition between energy regimes. Conclusion: For the first time, CAI has been applied to thick, 3D position sensitive CZT detectors. Real-time, combined CAI and Compton imaging is performed using two 3×3 detector arrays, resulting in a source distribution in space. This system has been commercialized by H3D, Inc. and is being acquired for

  5. Semiconductor detectors for medical tomography with high-energy heavy ions

    International Nuclear Information System (INIS)

    High-energy heavy ion beams are in use at the Lawrence Berkeley Laboratory for cancer therapy. In order to take full advantage of the very favorable depth-dose characteristics of those beams, it is necessary to determine the stopping characteristics of the ions in the complex media of a human with greater accuracy than obtainable with x-ray CAT scanning. Initial measurements with an array of Si dE/dx position sensitive detectors and a windowless thin planar Ge detector used in a side entry mode show the potential for fabricating an instrument for high accuracy on-line CAT scanning using the same ions to be used for therapy. It is estimated that one tomography can be obtained with a dose of 0.72 Rad-gm

  6. Canister cryogenic system for cooling germanium semiconductor detectors in borehole and marine probes

    Science.gov (United States)

    Boynton, G.R.

    1975-01-01

    High resolution intrinsic and lithium-drifted germanium gamma-ray detectors operate at about 77-90 K. A cryostat for borehole and marine applications has been designed that makes use of prefrozen propane canisters. Uses of such canisters simplifies cryostat construction, and the rapid exchange of canisters greatly reduces the time required to restore the detector to full holding-time capability and enhances the safety of a field operation where high-intensity 252Cf or other isotopic sources are used. A holding time of 6 h at 86 K was achieved in the laboratory in a simulated borehole probe in which a canister 3.7 cm diameter by 57 cm long was used. Longer holding times can be achieved by larger volume canisters in marine probes. ?? 1975.

  7. First investigation of a novel 2D position-sensitive semiconductor detector concept

    OpenAIRE

    Bassignana, D.; Fernández, M; Jaramillo, R.; Lozano Fantoba, Manuel; Muñoz Sánchez, F. J.; Pellegrini, Giulio; Quirion, D; Vila, Iván

    2011-01-01

    This paper presents a first study of the performance of a novel 2D position-sensitive microstrip detector, where the resistive charge division method was implemented by replacing the metallic electrodes with resistive electrodes made of polycrystalline silicon. A characterization of two proof-of-concept prototypes with different values of the electrode resistivity was carried out using a pulsed Near Infra-Red laser. The experimental data were compared with the electrical simulation of the sen...

  8. Quality assurance and testing before, during, and after construction of semiconductor tracking detectors

    International Nuclear Information System (INIS)

    We discuss the most frequent problems met with during the construction of three generations of microvertex detectors and a silicon-tungsten luminometer for the OPAL experiment, and during the many small projects and R and D work for other experiments and university projects. The emphasis will be on describing technical details and work practices adopted to prevent damage to and loss of expensive material, and the techniques preferred to prevent disaster during construction. (orig.)

  9. Photo detectors and sources of polarized light on the basis of strong anisotropic semiconductors

    International Nuclear Information System (INIS)

    Investigation of emitting and photo electrical properties of anisotropic GaSe, InSe, CdSnP2, CdIn2Se4 monocrystals and heterojunction on their basis established degree of anisotropy of electroluminescence and photoconductivity specified with anisotropy of electron condition. Principe of the creation of optoelectronic devises of new generation polar metric detectors and inverter of sources and collectors of the linearly polarized irradiation

  10. Optimizing the design and analysis of cryogenic semiconductor dark matter detectors for maximum sensitivity

    Energy Technology Data Exchange (ETDEWEB)

    Pyle, Matt Christopher [Stanford Univ., CA (United States)

    2012-01-01

    In this thesis, we illustrate how the complex E- field geometry produced by interdigitated electrodes at alternating voltage biases naturally encodes 3D fiducial volume information into the charge and phonon signals and thus is a natural geometry for our next generation dark matter detectors. Secondly, we will study in depth the physics of import to our devices including transition edge sensor dynamics, quasi- particle dynamics in our Al collection fins, and phonon physics in the crystal itself so that we can both understand the performance of our previous CDMS II device as well as optimize the design of our future devices. Of interest to the broader physics community is the derivation of the ideal athermal phonon detector resolution and it's T3 c scaling behavior which suggests that the athermal phonon detector technology developed by CDMS could also be used to discover coherent neutrino scattering and search for non-standard neutrino interaction and sterile neutrinos. These proposed resolution optimized devices can also be used in searches for exotic MeV-GeV dark matter as well as novel background free searches for 8GeV light WIMPs.

  11. Gamma-ray imaging and spectroscopy system using room-temperature semiconductor detector elements

    International Nuclear Information System (INIS)

    We report on the design, construction, and testing of a gamma-ray imaging system with spectroscopic capabilities. The imaging system consists of an orthogonal strip detector made from either HgI2 or CdZnTe crystals. The detectors utilize an 8x8 orthogonal strip configuration with 64 effective pixels. Both HgI2 or CdZnTe detectors are 1 cm2 devices with a strip pitch of approximately 1.2 mm (producing pixels of 1.2 mm x 1.2 mm). The readout electronics consist of parallel channels of preamplifier, shaping amplifier, discriminators, and peak sensing ADC. The preamplifiers are configured in hybrid technology, and the rest of the electronics are implemented in NIM and CAMAC with control via a Power Macintosh computer. The software used to readout the instrument is capable of performing intensity measurements as well as spectroscopy on all 64 pixels of the device. We report on the performance of the system imaging gamma-rays in the 20-500 keV energy range and using a pin-hole collimator to form the image. (author)

  12. Medical Compton cameras based on semiconductor detectors design and experimental development

    CERN Document Server

    Scannavini, M G

    2001-01-01

    The work presented in this thesis is aimed at the study of Compton scatter as an alternative method of collimating gamma-rays in nuclear medicine applications. Conventional approaches to radioisotope medical imaging and their current limitations are examined. The theory of electronic collimation based on Compton scatter is introduced and it is shown that in principle its application could provide an advantageous imaging method, with both high spatial resolution and high sensitivity. The current status of research in the field, of Compton cameras is assessed and potential niches for applications of clinical interest are suggested. The criteria for the design of a Compton scatter camera are examined. A variety of semiconductors are considered for the construction of an electronic collimator and results from Monte Carlo computer simulations are presented for photon energies of clinical interest. It is concluded that the most viable approach is to design a silicon collimator for the imaging of high-energy (511 ke...

  13. Status of radiation damage measurements in room temperature semiconductor radiation detectors

    International Nuclear Information System (INIS)

    The literature of radiation damage measurements on cadmium zinc telluride (CZT), cadmium telluride (CT), and mercuric iodide (HgI2) is reviewed for the purpose of determining their applicability to space applications. CZT strip detectors exposed to intermediate energy (1.3 MeV) proton fluences exhibit increased interstrip leakage after 1010 p/cm2 and significant bulk leakage after 1012 p/cm2. CZT exposed to 200 MeV protons shows a two-fold loss in energy resolution after a fluence of 5 x 109 p/cm2 in thick (3 mm) planar devices but little effect in 2 mm devices. No energy resolution effects were noted from moderated fission spectrum neutrons after fluences up to 1010 n/cm2, although activation was evident. CT detectors show resolution losses after fluences of 3 x 109 p/cm2 at 33 MeV for chlorine-doped detectors. Indium doped material may be more resistant. Neutron exposures (8 MeV) caused resolution losses after fluences of 2 x 1010 n/cm2. Mercuric iodide has been studied with intermediate energy protons (10 to 33 MeV) at fluences up to 1012 p/cm2 and with 1.5 GeV protons at fluences up to 1.2 x 108 p/cm2. Neutron exposures at 8 MeV have been reported at fluences up to 1015 n/cm2. No radiation damage was found under these irradiation conditions

  14. Qualification model of the space ISGRI CdTe gamma-ray camera

    CERN Document Server

    Limousin, O; Bonnin, C; Cretolle, J; Goldwurm, A; Horeau, B; Laurent, P; Lebrun, F; Leray, J P

    2001-01-01

    A new generation of large area semiconductor based gamma-ray camera for astrophysics space application has been developed through the gamma-ray IBIS (Imager on Board INTEGRAL Satellite) telescope program, on board the ESA INTEGRAL satellite. This instrument features a coded-mask aperture imaging system, active and passive shields and two detector arrays. The first one (ISGRI : INTEGRAL Soft Gamma-Ray Imager) is made of 16384 CdTe detectors (4x4 mm large, 2 mm thick) operating at room temperature and will operate between 15 keV and 1 MeV. The second detector array (PICsIT : Pixelated CsI Telescope) is made of 4096 CsI scintillators (9.2x9.2 mm large, 30 mm high) coupled to silicon PIN photodiodes working between 150 keV and 10 MeV. IBIS combine broad band energy, spectroscopic capabilities and high spatial resolution imaging (12 arcmin) over a wide field of view (approx 20 deg. x 20 deg., 50% sensitivity). A 'flight-like' model of the detectors has been built, integrated and successfully tested. After a descri...

  15. Digital X-ray microscopy of small biological samples using Medipix2 semiconductor pixel detector

    Czech Academy of Sciences Publication Activity Database

    Dammer, J.; Weyda, František; Jakůbek, J.; Sopko, V.; Žemlička, J.; Hanus, Robert

    Badajoz: Formatex, 2010 - (A. Méndez-Vilas, J.), s. 415-421. (Microscopy Book Series). ISBN 978-84-614-6189-9 R&D Projects: GA MŠk 2B06007; GA AV ČR IAA600550614; GA MŠk 2B06005 Grant ostatní: GA MŠk(CZ) 1P04LA211; GA MŠk(CZ) LC06041 Institutional research plan: CEZ:AV0Z40550506; CEZ:AV0Z50070508 Keywords : X-ray imaging * Digital radiography * Computed tomography (CT) * Photon and X-ray detectors Subject RIV: CC - Organic Chemistry

  16. Amplitude and rise time compensated timing optimized for large semiconductor detectors

    International Nuclear Information System (INIS)

    The ARC timing described has excellent timing properties even when using a wide energy range, eg from 10 keV to over 1 MeV. The detector signal from a preamplifier is accepted directly by the unit as a timing filter amplifier with a sensitivity of 1 mV is incorporated. The adjustable rise time rejection feature makes it possible to achieve a good prompt time spectrum with symmetrical exponential shape down to less than 1/100 of the peak value. A complete schematic of the unit is given together with results of extensive tests of its performance. For example the time spectrum for (1330+-20) keV of 60Co taken with a 43 ccm Ge(Li) detector has the following parameters: FWHM=2.2 ns, FW(.1)M = 4.4 ns and FW(.01)M = 7.6 ns and for (50+-10) keV of 22Na the following was obtained: FWHM =10.8 ns, FW(.1)M =21.6 ns and FW(.01)M = 34.6 ns. In another experiment with two fast plastic scintillators (NE 102A) and using a 20 % dynamic energy range the following was measured FWHM =280 ps, FW(.1)M = 470 ps and FW(.01)M =710 ps. (Auth.)

  17. Holmium-166m: multi-gamma standard to determine the activity of radionuclides in semiconductor detectors

    International Nuclear Information System (INIS)

    The efficiency and calibration curves as function of gamma-ray energy for a germanium detector are usually established by using many standard gamma ray sources of radionuclides decaying with few gamma rays or radionuclides having complex decay scheme, as 152Eu or 133Ba. But these radionuclides cannot be used alone, because they have a few gamma lines with high intensity and these lines have a irregular distribution in the energy spectrum. 166mHo is found to be a convenient single source for such calibration, because it decays by β- with subsequent emission of about 40 strong and well distributed gamma lines between 80 and 1500 keV. Moreover, its long half - life (1200 years) and X-rays characteristics between 40 and 50 keV makes it a good standard for calibration of germanium detectors. However, it is necessary to know with accuracy and precision the gamma ray intensities of their main lines, due to the fact that literature has showed discrepant values. Then, a methodology to determine the emission probability of its main lines is proposed by means of combined use of gamma spectrometry and coincidence 4πβ -γ techniques. The experimental results show consistence to the others authors, with lower or compatible uncertainties. (author)

  18. Investigation of temperature dependence of semiconductor detectors used in medicine for radiation measurements

    Science.gov (United States)

    Ozleyis Altunkok, Simay; Tuncel, Nina; Ucar, Nazim

    2015-07-01

    In this study, the temperature dependence of p-type semiconductor diodes that are a part of in-vivo dosimetry system was assessed in Co-60 photon energy. The collimator and gantry angle on zero degree, SSD 100 cm, field size 20x20 cm2 was selected. The IBA EDP-5, EDP-10 and EDP-20 diode types that included in this study have different thickness of build-up material so the depth of measurements at water equivalent phantom by FC65-p ion chamber was selected at 5, 10 and 20 mm. Along the process the room and phantom temperature was measured and recorded (19°C). The special water filled PMMA phantom was used for diode set-up on its surface and a thermometer for determine phantom temperature was employed. Each type of diodes irradiated separately for one minute and the signal to dose sensitivity and calibration was performed at room temperature (19°C) by OmniPro-InViDos software with DPD-12 electrometer. Examination was repeated from 33°C to 20°C temperatures. The temperature correction factors were found from slope of the linear drawings for each diode types. The obtained correction factor for EDP-5 and EDP-10 was 0.29 %°C/cGy and 0.30 %°C/cGy respectively, that higher than recommended factor (%0.25°C/cGy). While the more fluctuation for EDP-20 was realized.

  19. Orientational domains in metalorganic chemical vapor deposited CdTe(111) film on cube-textured Ni

    International Nuclear Information System (INIS)

    CdTe thin film was grown by metal organic chemical vapor deposition on cube-textured Ni substrate. The microstructures of the CdTe film and Ni substrate were studied using transmission electron microscopy (TEM) lattice imaging in cross sectional. The orientational relationships of multiple hetereoepitaxial domains in the CdTe film were examined by TEM diffraction. The observed epitaxy is [111]CdTe//[001]Ni. The adjacent domains in CdTe film have a 30° rotation with respect to each other as inferred by the observed different diffraction patterns obtained from different zone axes. The high resolution lattice imaging shows that lamellar twins dominate within each domain. Our results are compared with CdTe(111) film epitaxially grown on Si(001) substrate by molecular beam epitaxy reported in the literature. - Highlights: ► Epitaxial CdTe film grew on textured Ni at 350 °C despite of a large lattice mismatch. ► Epitaxial relationship is CdTe(111) parallel to Ni(001). ► 30° CdTe orientation domains inferred from transmission electron microscopy patterns ► Local inclined angle between CdTe and Ni at the interface is due to vertical mismatch. ► Single crystal-like epitaxial semiconductors can be grown on low cost metal sheet

  20. First investigation of a novel 2D position-sensitive semiconductor detector concept

    International Nuclear Information System (INIS)

    This paper presents a first study of the performance of a novel 2D position-sensitive microstrip detector, where the resistive charge division method was implemented by replacing the metallic electrodes with resistive electrodes made of polycrystalline silicon. A characterization of two proof-of-concept prototypes with different values of the electrode resistivity was carried out using a pulsed Near Infra-Red laser. The experimental data were compared with the electrical simulation of the sensor equivalent circuit coupled to simple electronics readout circuits. The good agreement between experimental and simulation results establishes the soundness of resistive charge division method in silicon microstrip sensors and validates the developed simulation as a tool for the optimization of future sensor prototypes. Spatial resolution in the strip length direction depends on the ionizing event position. The average value obtained from the protype analysis is close to 1.2% of the strip length for a 6 MIP signal.

  1. Excitability and optical pulse generation in semiconductor lasers driven by resonant tunneling diode photo-detectors.

    Science.gov (United States)

    Romeira, Bruno; Javaloyes, Julien; Ironside, Charles N; Figueiredo, José M L; Balle, Salvador; Piro, Oreste

    2013-09-01

    We demonstrate, experimentally and theoretically, excitable nanosecond optical pulses in optoelectronic integrated circuits operating at telecommunication wavelengths (1550 nm) comprising a nanoscale double barrier quantum well resonant tunneling diode (RTD) photo-detector driving a laser diode (LD). When perturbed either electrically or optically by an input signal above a certain threshold, the optoelectronic circuit generates short electrical and optical excitable pulses mimicking the spiking behavior of biological neurons. Interestingly, the asymmetric nonlinear characteristic of the RTD-LD allows for two different regimes where one obtain either single pulses or a burst of multiple pulses. The high-speed excitable response capabilities are promising for neurally inspired information applications in photonics. PMID:24103966

  2. First Investigation on a novel 2D position sensitive semiconductor detector concept

    CERN Document Server

    Bassignana, D; Jaramillo, R; Lozano, M; Munoz, F.J; Pellegrini, G; Quirion, D; Vila, I

    2012-01-01

    This paper presents a first study of the performance of a novel 2D position-sensitive microstrip detector, where the resistive charge division method was implemented by replacing the metallic electrodes with resistive electrodes made of polycrystalline silicon. A characterization of two proof-of-concept prototypes with different values of the electrode resistivity was carried out using a pulsed Near Infra-Red laser. The experimental data were compared with the electrical simulation of the sensor equivalent circuit coupled to simple electronics readout circuits. The good agreement between experimental and simulation results establishes the soundness of resistive charge division method in silicon microstrip sensors and validates the developed simulation as a tool for the optimization of future sensor prototypes. Spatial resolution in the strip length direction depends on the ionizing event position. The average value obtained from the protype analysis is close to 1.2% of the strip length for a 6 MIP signal.

  3. Ultrafast nuclear myocardial perfusion imaging on a new gamma camera with semiconductor detector technique: first clinical validation

    International Nuclear Information System (INIS)

    To assess the diagnostic performance of a novel ultrafast cardiac gamma camera with cadmium-zinc-telluride (CZT) solid-state semiconductor detectors for nuclear myocardial perfusion imaging (MPI). The study group comprised 75 consecutive patients (55 men, BMI range 19-45 kg/m2) who underwent a 1-day 99mTc-tetrofosmin adenosine-stress/rest imaging protocol. Scanning was performed first on a conventional dual-detector SPECT gamma camera (Ventri, GE Healthcare) with a 15-min acquisition time each for stress and rest. All scans were immediately repeated on an ultrafast CZT camera (Discovery 530 NMc, GE Healthcare) with a 3-min scan time for stress and a 2-min scan time for rest. Clinical agreement (normal, ischaemia, scar) between CZT and SPECT was assessed for each patient and for each coronary territory using SPECT MPI as the reference standard. Segmental myocardial tracer uptake values (percent of maximum) using a 20-segment model and left ventricular ejection fraction (EF) values obtained using CZT were compared with those obtained using conventional SPECT by intraclass correlation and by calculating Bland-Altman limits of agreement. There was excellent clinical agreement between CZT and conventional SPECT on a per-patient basis (96.0%) and on a per-vessel territory basis (96.4%) as shown by a highly significant correlation between segmental tracer uptake values (r=0.901, p<0.001). Similarly, EF values for both scanners were highly correlated (r=0.976, p<0.001) with narrow Bland-Altman limits of agreement (-5.5-10.6%). The novel CZT camera allows a more than fivefold reduction in scan time and provides clinical information equivalent to conventional standard SPECT MPI. (orig.)

  4. Ultrafast nuclear myocardial perfusion imaging on a new gamma camera with semiconductor detector technique: first clinical validation

    Energy Technology Data Exchange (ETDEWEB)

    Buechel, Ronny R.; Herzog, Bernhard A.; Husmann, Lars; Burger, Irene A.; Pazhenkottil, Aju P.; Treyer, Valerie; Valenta, Ines; Schulthess, Patrick von; Nkoulou, Rene; Wyss, Christophe A. [University Hospital Zurich, Cardiac Imaging, Zurich (Switzerland); Kaufmann, Philipp A. [University Hospital Zurich, Cardiac Imaging, Zurich (Switzerland); University of Zurich, Zurich Center for Integrative Human Physiology (ZIHP), Zurich (Switzerland)

    2010-04-15

    To assess the diagnostic performance of a novel ultrafast cardiac gamma camera with cadmium-zinc-telluride (CZT) solid-state semiconductor detectors for nuclear myocardial perfusion imaging (MPI). The study group comprised 75 consecutive patients (55 men, BMI range 19-45 kg/m{sup 2}) who underwent a 1-day {sup 99m}Tc-tetrofosmin adenosine-stress/rest imaging protocol. Scanning was performed first on a conventional dual-detector SPECT gamma camera (Ventri, GE Healthcare) with a 15-min acquisition time each for stress and rest. All scans were immediately repeated on an ultrafast CZT camera (Discovery 530 NMc, GE Healthcare) with a 3-min scan time for stress and a 2-min scan time for rest. Clinical agreement (normal, ischaemia, scar) between CZT and SPECT was assessed for each patient and for each coronary territory using SPECT MPI as the reference standard. Segmental myocardial tracer uptake values (percent of maximum) using a 20-segment model and left ventricular ejection fraction (EF) values obtained using CZT were compared with those obtained using conventional SPECT by intraclass correlation and by calculating Bland-Altman limits of agreement. There was excellent clinical agreement between CZT and conventional SPECT on a per-patient basis (96.0%) and on a per-vessel territory basis (96.4%) as shown by a highly significant correlation between segmental tracer uptake values (r=0.901, p<0.001). Similarly, EF values for both scanners were highly correlated (r=0.976, p<0.001) with narrow Bland-Altman limits of agreement (-5.5-10.6%). The novel CZT camera allows a more than fivefold reduction in scan time and provides clinical information equivalent to conventional standard SPECT MPI. (orig.)

  5. Investigation of temperature dependence of semiconductor detectors used in medicine for radiation measurements

    Directory of Open Access Journals (Sweden)

    Altunkok Simay Ozleyis

    2015-01-01

    Full Text Available In this study, the temperature dependence of p-type semiconductor diodes that are a part of in-vivo dosimetry system was assessed in Co-60 photon energy. The collimator and gantry angle on zero degree, SSD 100 cm, field size 20x20 cm2 was selected. The IBA EDP-5, EDP-10 and EDP-20 diode types that included in this study have different thickness of build-up material so the depth of measurements at water equivalent phantom by FC65-p ion chamber was selected at 5, 10 and 20 mm. Along the process the room and phantom temperature was measured and recorded (19°C. The special water filled PMMA phantom was used for diode set-up on its surface and a thermometer for determine phantom temperature was employed. Each type of diodes irradiated separately for one minute and the signal to dose sensitivity and calibration was performed at room temperature (19°C by OmniPro-InViDos software with DPD-12 electrometer. Examination was repeated from 33°C to 20°C temperatures. The temperature correction factors were found from slope of the linear drawings for each diode types. The obtained correction factor for EDP-5 and EDP-10 was 0.29 %°C/cGy and 0.30 %°C/cGy respectively, that higher than recommended factor (%0.25°C/cGy. While the more fluctuation for EDP-20 was realized.

  6. Applications of CdTe to nuclear medicine. Final report

    International Nuclear Information System (INIS)

    Uses of cadmium telluride (CdTe) nuclear detectors in medicine are briefly described. They include surgical probes and a system for measuring cerebral blood flow in the intensive care unit. Other uses include nuclear dentistry, x-ray exposure control, cardiology, diabetes, and the testing of new pharmaceuticals

  7. Characteristics of TlBr single crystals grown using the vertical Bridgman-Stockbarger method for semiconductor-based radiation detector applications

    Directory of Open Access Journals (Sweden)

    Jin Kim Dong

    2016-06-01

    Full Text Available TlBr single crystals grown using the vertical Bridgman-Stockbarger method were characterized for semiconductor based radiation detector applications. It has been shown that the vertical Bridgman-Stockbarger method is effective to grow high-quality single crystalline ingots of TlBr. The TlBr single crystalline sample, which was located 6 cm from the tip of the ingot, exhibited lower impurity concentration, higher crystalline quality, high enough bandgap (>2.7 eV, and higher resistivity (2.5 × 1011 Ω·cm which enables using the fabricated samples from the middle part of the TlBr ingot for fabricating high performance semiconductor radiation detectors.

  8. Fluorescence-suppressed time-resolved Raman spectroscopy of pharmaceuticals using complementary metal-oxide semiconductor (CMOS) single-photon avalanche diode (SPAD) detector

    OpenAIRE

    Rojalin, Tatu; Kurki, Lauri; Laaksonen, Timo; Viitala, Tapani; Kostamovaara, Juha; Gordon, Keith C.; Galvis, Leonardo; Wachsmann-Hogiu, Sebastian; Strachan, Clare J.; Yliperttula, Marjo

    2015-01-01

    In this work, we utilize a short-wavelength, 532-nm picosecond pulsed laser coupled with a time-gated complementary metal-oxide semiconductor (CMOS) single-photon avalanche diode (SPAD) detector to acquire Raman spectra of several drugs of interest. With this approach, we are able to reveal previously unseen Raman features and suppress the fluorescence background of these drugs. Compared to traditional Raman setups, the present time-resolved technique has two major improvements. First, it is ...

  9. Development of surgical gamma probes with TlBr semiconductors and CsI(Tl) scintillators crystals

    International Nuclear Information System (INIS)

    Radio guided surgery, using probes with radiation detectors, has been prominence in the medical area in the last decade. This technique consists in injecting a radioactive substance to concentrate in tumour and assist the localization during the surgical procedure. The radio guided surgeries allowing the identification of lymph node has revolutioned the behavior of tumour in initial stadium when are being spread by lymphatic way. The conditions imposed to the surgery due the proximity between some lymph nodes, demands of the probes, a small diameters and capacity of individual identification of these lymph nodes radiolabelled by a specific tracer. The international market supplies these probes with CdTe semiconductors and scintillators, but there is some time lack a promptly technical assistance in the Brazilian market. This work developed probes with national technology, using CsI(Tl) scintillators crystals and, in substitution to CdTe crystals semiconductors, the TlBr crystal, that is a new semiconductor detector in a world-wide development, with advantages in relation to the CdTe. Both crystals have been grown in IPEN. All the necessary electronics, specially, the preamplifier, that was also a restrictive factor for development of these types of probe in the country, have been developed with components found in the national market. Systematic measures of spatial resolution, spatial selectivity, maximum sensitivity and quality of the shielding have been carried the probes development. The results have shown that the probes, one with the CsI(Tl) crystal and another with TlBr semiconductor presented the requested performance in the international literature for radio guided probes. (author)

  10. Advanced semiconductor detector development: Development of a room-temperature, gamma ray detector using gallium arsenide to develop an electrode detector. Progress report, September 30, 1994--September 29, 1995

    International Nuclear Information System (INIS)

    Devices fabricated from wide bandgap materials that can be operated without cooling suffer from poor energy resolution and are limited to very small volumes; this arises largely from poor hole mobility in compound semiconductors. Three different device configurations are being investigated for possibly overcoming this limitation: buried grid-single carrier devices, trenched single carrier devices, and devices using patterned coplanar electrodes (CdZnTe). In the first, leakage problems were encountered. For the second, a set of specifications has been completed, and electron cyclotron resonance etching will be done at an off-campus facility. For the third, Aurora will supply 3 different CdZnTe detectors. An analytical study was done of the patterned electrode approach

  11. Solid-state cadmium telluride radiation detector

    International Nuclear Information System (INIS)

    The growth of CdTe single crystal and its application to CdTe detector array was studied for X-ray computed tomography (XCT) equipment. A p-type CdTe single crystal with 104 ohm.cm specific resistivity was grown in a quartz ampoule under vapor pressure control of Cd in a vertical Bridgman furnace. An 18-element detector array was fabricated with this single crystal. The detector was operated with no bias and the sensitivity was confirmed to be between 2.8 x 10-12 and 14 x 10-12 A.h/(R.mm2). Commercial CdTe single crystal was used to manufacture as 560-element detector array for XCT. Results show that CdTe detector is sensitive, linear and has high resolution. (author)

  12. CdTe Timepix detectors for single-photon spectroscopy and linear polarimetry of high-flux hard x-ray radiation

    Science.gov (United States)

    Hahn, C.; Weber, G.; Märtin, R.; Höfer, S.; Kämpfer, T.; Stöhlker, Th.

    2016-04-01

    Single-photon spectroscopy of pulsed, high-intensity sources of hard X-rays — such as laser-generated plasmas — is often hampered by the pileup of several photons absorbed by the unsegmented, large-volume sensors routinely used for the detection of high-energy radiation. Detectors based on the Timepix chip, with a segmentation pitch of 55 μm and the possibility to be equipped with high-Z sensor chips, constitute an attractive alternative to commonly used passive solutions such as image plates. In this report, we present energy calibration and characterization measurements of such devices. The achievable energy resolution is comparable to that of scintillators for γ spectroscopy. Moreover, we also introduce a simple two-detector Compton polarimeter setup with a polarimeter quality of (98 ± 1)%. Finally, a proof-of-principle polarimetry experiment is discussed, where we studied the linear polarization of bremsstrahlung emitted by a laser-driven plasma and found an indication of the X-ray polarization direction depending on the polarization state of the incident laser pulse.

  13. CdTe Timepix detectors for single-photon spectroscopy and linear polarimetry of high-flux hard x-ray radiation.

    Science.gov (United States)

    Hahn, C; Weber, G; Märtin, R; Höfer, S; Kämpfer, T; Stöhlker, Th

    2016-04-01

    Single-photon spectroscopy of pulsed, high-intensity sources of hard X-rays - such as laser-generated plasmas - is often hampered by the pileup of several photons absorbed by the unsegmented, large-volume sensors routinely used for the detection of high-energy radiation. Detectors based on the Timepix chip, with a segmentation pitch of 55 μm and the possibility to be equipped with high-Z sensor chips, constitute an attractive alternative to commonly used passive solutions such as image plates. In this report, we present energy calibration and characterization measurements of such devices. The achievable energy resolution is comparable to that of scintillators for γ spectroscopy. Moreover, we also introduce a simple two-detector Compton polarimeter setup with a polarimeter quality of (98 ± 1)%. Finally, a proof-of-principle polarimetry experiment is discussed, where we studied the linear polarization of bremsstrahlung emitted by a laser-driven plasma and found an indication of the X-ray polarization direction depending on the polarization state of the incident laser pulse. PMID:27131653

  14. NONLINEAR OPTICS: Energy exchange between optical waves due to self-diffraction by photorefractive gratings in a CdTe crystal

    Science.gov (United States)

    Borshch, A. A.; Brodin, M. S.; Burin, O. M.; Volkov, V. I.; Kukhtarev, N. V.; Semenets, T. I.; Smereka, Z. N.

    1990-07-01

    Theoretical and experimental investigations were made of a photorefractive nonlinearity of CdTe semiconductor crystals. Photorefractive gratings were formed in undoped CdTe and used to provide efficient energy exchange between nanosecond pulsed light beams (λ approx 1.06 μm) characterized by an exchange gain of ~ 0.13 cm - 1.

  15. Application of a CdTe gamma-ray spectrometer to remote characterization of high-level radioactive waste tanks

    Energy Technology Data Exchange (ETDEWEB)

    Keele, B.D.; Addleman, R.S.; Blewett, G.R.; McClellan, C.S.; Subrahmanyam, V.B.; Troyer, G.L.

    1991-10-01

    Small, shielded cadmium telluride (CdTe) semiconductor gamma-ray detectors have been used for in situ radiological characterization of underground high-level radioactive waste tanks. Remote measurements up to 700 R/h have been made in gamma radiation fields. Spectral data have been used to generate qualitative and quantitative radionuclide profiles of high-level radioactive waste tanks. Two electronic spectral enhancement techniques (pulse risetime discrimination and pulse risetime compensation) have been used in order to measure trace isotopes in the presence of large amounts of {sup 137}Cs. Spectral resolution better than 1.5% FWHM for the {sup 137}Cs 662 keV photopeak has been obtained. 4 refs., 7 figs.

  16. Highly luminescent water-soluble CdTe quantum dots

    OpenAIRE

    Wuister, SF; Swart, A.N.; van Driel, F; Hickey, SG; Donega, CD; Swart, Ingmar

    2003-01-01

    Colloidal CdTe quantum dots prepared in TOP/DDA (trioctylphosphine/dodecylamine) are transferred into water by the use of aminoethanethiol.HCl (AET) or mercaptopropionic acid (MPA). This results in an increase in the photoluminescence quantum efficiency and a longer exciton lifetime. For the first time, water-soluble semiconductor nanocrystals presenting simultaneously high band-edge photoluminescence quantum efficiencies (as high as 60% at room temperature), monoexponential exciton decays, a...

  17. CdTe ambulatory ventricular function monitor

    International Nuclear Information System (INIS)

    A prototype device consisting of two arrays of CdTe detectors, ECG amplifiers and gate, microprocessor, and tape recorder was devised to record simultaneous ECG and radionuclide blood pool data from the left ventricle for extended periods during normal activity. The device is intended to record information concerning both normal and abnormal physiology of the heart and to permit the evaluation of new pharmaceuticals under everyday conditions. Preliminary results indicate that the device is capable of recording and reading out data from both phantoms and patients

  18. Low power, low noise, charge sensitive amplifier in CMOS 0.18 μm technology for the readout of fine pitch pixelated CdTe detector

    International Nuclear Information System (INIS)

    Our group is currently developing a new project dedicated to the design of new Cd(Zn)Te spectro-imaging systems for future space borne astrophysics missions. The main goal is to build a spectro-imaging system with matrix ASIC hybridized to pixelated Cd(Zn)Te detector with typical pixel of 300 μm pitch and typical energy resolution of 0.5 keV at 60 keV. Before designing a complete matrix of readout channels, we designed a prototype ASIC to evaluate the microelectronic technology in terms of noise and tolerance to radiation. We designed an ASIC in the standard AMS 0.18 μm CMOS technology dedicated to the readout of very low capacitance (≤1 pF) and very low dark current (≤5 pA) Cd(Zn)Te detectors. The Caterpylar AMS is a set of 30 low noise low power Charge Sensitive Amplifiers (CSAs). All the CSAs have the same folded cascade architecture, only the type (PMOS or NMOS) and the geometry of the input transistors differ between CSAs. The noise performances of the technology are very good since a minimal ENC of 9 e(-)rms has been measured with power consumption in the CSA of 12 μW only. Influence of the W/L ratio and W * L product of input transistor on noise has been measured and discussed. We connected one of the CSA to a silicon diode and measured an energy resolution of 580 eV FWHM at 122 keV with a 57Co source and of 470 eV FWHM at 59.5 keV with a 241Am source. (authors)

  19. Multielement X-ray radiometric analysis with application of semiconductor detectors and automatic processing of the results of measurements

    International Nuclear Information System (INIS)

    Problems of complex extraction of useful components from the ores with compound composition demand to ensure multielement analysis having the accuracy which is sufficient for practical purposes. Great possibilities has the X-ray-radiometric analysis with application of semiconductor detectors (SD) and with processing the results of measurements by means of mini- or micro-computers. Present state in the detection and computation techniques permits to introduce the said instruments into the practical use in the analytical laboratories of the mining enterprises. On the base of discussion of the practical tasks in analysis of different types of ores, in the paper basic principles of the multielement X-ray-radiometric analysis for industrial purposes have been formulated. First of all it is an installation with few channels. The main requirement in creation of such installations is to ensure high relaibility and stability of their performance. A variant is given of such analyzer, constructed with use of SiLi or Ge detecting blocks. Possibility for quick change of the excitation sources made of the set of iron-55, cadmium-109, americium-241 or cobalt-57 ensures effective excitation of elements in the range from calcium to uranium. Some practical methods of analysis have been discussed in the paper. They are based both on the methods of passive and active experiments at the calibration stages. Accuracy of these methods is enough for change of ordinary chemical analysis by the radiometric one. Problems are discussed of application of mini- and micro-computers, permitting processing of information according to the metods of analysis having been developed. Some examples are given of practical realization of the multielement X-ray-radiometric analysis of the lead-zinc, cppper-molybdenum, lead-barite and some other types of ores and also of the products of processing of ores

  20. Development of a counting pixel detector for 'Digitales Roentgen'

    International Nuclear Information System (INIS)

    The development of a single photon counting X-ray imaging detector for medical applications using hybrid pixel detectors is reported. The electronics development from the first prototype derived from detector development for particle physics experiments (ATLAS) to the imaging chip MPEC (multi picture element counters) for medical applications is described. This chip consists of 32 x 32 pixels of 200 μm x 200 μm size, each containing the complete read out electronics, i.e. an amplifier, two discriminators with adjustable thresholds and two 18-bit linear feedback shift-counters allowing energy windowing for contrast increase. Results on electronics performance are shown as well as measurements with several semiconductor materials (Si, GaAs, CdTe). Important aspects like detection efficiency, sensor homogeneity, linearity and spatial resolution are discussed. (orig.)

  1. Measurement of the electrical properties of a polycrystalline cadmium telluride for direct conversion flat panel x-ray detector

    International Nuclear Information System (INIS)

    Cadmium telluride (CdTe) is one of the best candidate direct conversion material for medical X-ray application because it satisfies the requirements of direct conversion x-ray material such as high atomic absorption, density, bandgap energy, work fuction, and resistivity. With such properties, single crystal CdTe exhibits high quantum efficiency and charge collection efficiency. However, for the development of low-cost large area detector, the study of the improvement of polycrystalline CdTe property is desirable. In this study, in order to improve the properties of polycrystalline CdTe, we produced polycrystalline CdTe with different kinds of raw materials, high purity Cd and Te powder compounds and bulk CdTe compound synthesized from single crystal CdTe. The electric properties including resistivity, x-ray sensitivity, and charge transport properties were investigated. As a result, polycrystalline CdTe exhibited simular level of resistivity and x-ray sensitivity to single crystal CdTe. The carrier transport properties of polycrystalline CdTe showed poorer properties than those of single crystal CdTe due to significant charge trapping. However, the polycrystalline CdTe fabricated with bulk CdTe compound synthesized from single crystal CdTe showed better charge transport properties than the polycrystalline CdTe fabricated with CdTe powder compounds. This is suitable for diagnostic x-ray detectors, especially for digital fluoroscopy

  2. High-contrast X-ray micro-tomography of low attenuation samples using large area hybrid semiconductor pixel detector array of 10×5 Timepix chips

    International Nuclear Information System (INIS)

    State-of-the-art hybrid pixel semiconductor detectors provide excellent imaging properties such as unlimited dynamic range, high spatial resolution, high frame rate and energy sensitivity. Nevertheless, a limitation in the use of these devices for imaging has been the small sensitive area of a few square centimetres. In the field of microtomography we make use of a large area pixel detector assembled from 50 Timepix edgeless chips providing fully sensitive area of 14.3×7.15 cm2. We have successfully demonstrated that the enlargement of the sensitive area enables high-quality tomographic measurements of whole objects with high geometrical magnification without any significant degradation in resulting reconstructions related to the chip tilling and edgeless sensor technology properties. The technique of micro-tomography with the newly developed large area detector is applied for samples formed by low attenuation, low contrast materials such a seed from Phacelia tanacetifolia, a charcoalified wood sample and a beeswax seal sample

  3. High-contrast X-ray micro-tomography of low attenuation samples using large area hybrid semiconductor pixel detector array of 10 × 5 Timepix chips

    Science.gov (United States)

    Karch, J.; Krejci, F.; Bartl, B.; Dudak, J.; Kuba, J.; Kvacek, J.; Zemlicka, J.

    2016-01-01

    State-of-the-art hybrid pixel semiconductor detectors provide excellent imaging properties such as unlimited dynamic range, high spatial resolution, high frame rate and energy sensitivity. Nevertheless, a limitation in the use of these devices for imaging has been the small sensitive area of a few square centimetres. In the field of microtomography we make use of a large area pixel detector assembled from 50 Timepix edgeless chips providing fully sensitive area of 14.3 × 7.15 cm2. We have successfully demonstrated that the enlargement of the sensitive area enables high-quality tomographic measurements of whole objects with high geometrical magnification without any significant degradation in resulting reconstructions related to the chip tilling and edgeless sensor technology properties. The technique of micro-tomography with the newly developed large area detector is applied for samples formed by low attenuation, low contrast materials such a seed from Phacelia tanacetifolia, a charcoalified wood sample and a beeswax seal sample.

  4. Determination of spectrum-dose conversion operator for a pure germanium semi-conductor detector for environmental γ-ray measurement

    International Nuclear Information System (INIS)

    The G(E) functions of the spectrum-dose conversion operator for a cylindrical pure germanium semi-conductor detector to evaluate the exposure rate were determined. Effective volume of the detector is 106.5 cm3 (5.43 cm PHI x 4.6 cm), and the energy range of gamma-ray applicable for the G(E) function is from 40 keV up to 3 MeV. Authors have already determined G(E) functions for cylindrical NaI(TL) scintillation detectors and for spherical ones. However, as germanium detectors are far superior to NaI(TL) scintillation detectors in the point of energy resolution, they are very useful in the field of environmental gamma-ray measurement for gamma-ray energy analysis and exposure evaluation using their pulse height spectrum. The present G(E) functions are prepared for a pure germanium detector for environmental gamma-ray measurement. Exposure rate can be evaluated accurately and easily by using these G(E) functions. The measuring accuracy in the range of 40 keV up to 3 MeV for exposure unit are within about 5%. These G(E) functions are useful for interconnecting the results measured by various instruments in environmental monitoring. (author)

  5. PC/FRAM plutonium isotopic analysis of CdTe gamma-ray spectra

    CERN Document Server

    Vo, D T

    2002-01-01

    This paper reports the results of isotopics measurements of plutonium with the new CdTe gamma-ray spectrometer. These are the first wide-range plutonium gamma-ray isotopics analysis results obtained with other than germanium spectrometers. The CdTe spectrometer measured small plutonium reference samples in reasonable count times, covering the range from low to high burnup. The complete experimental hardware included the new, commercial, portable CdTe detector and two commercial portable multichannel analyzers. Version 4 of FRAM is the software that performed the isotopics analysis.

  6. PC/FRAM plutonium isotopic analysis of CdTe gamma-ray spectra

    Science.gov (United States)

    Vo, D. T.; Russo, P. A.

    2002-07-01

    This paper reports the results of isotopics measurements of plutonium with the new CdTe gamma-ray spectrometer. These are the first wide-range plutonium gamma-ray isotopics analysis results obtained with other than germanium spectrometers. The CdTe spectrometer measured small plutonium reference samples in reasonable count times, covering the range from low to high burnup. The complete experimental hardware included the new, commercial, portable CdTe detector and two commercial portable multichannel analyzers. Version 4 of FRAM is the software that performed the isotopics analysis.

  7. SU-E-T-231: Measurements of Gold Nanoparticle-Mediated Proton Dose Enhancement Due to Particle-Induced X-Ray Emission and Activation Products Using Radiochromic Films and CdTe Detector

    Energy Technology Data Exchange (ETDEWEB)

    Cho, J; Cho, S [Dept. of Radiation Physics, UT MD Anderson Cancer Center, Houston, TX (United States); Manohar, N [Dept. of Radiation Physics, UT MD Anderson Cancer Center, Houston, TX (United States); Medical Physics Program, Georgia Institute of Technology, Atlanta, GA (Georgia); Krishnan, S [Dept. of Radiation Oncology, UT MD Anderson Cancer Center, Houston, TX (United States)

    2014-06-01

    Purpose: There have been several reports of enhanced cell-killing and tumor regression when tumor cells and mouse tumors were loaded with gold nanoparticles (GNPs) prior to proton irradiation. While particle-induced xray emission (PIXE), Auger electrons, secondary electrons, free radicals, and biological effects have been suggested as potential mechanisms responsible for the observed GNP-mediated dose enhancement/radiosensitization, there is a lack of quantitative analysis regarding the contribution from each mechanism. Here, we report our experimental effort to quantify some of these effects. Methods: 5-cm-long cylindrical plastic vials were filled with 1.8 mL of either water or water mixed with cylindrical GNPs at the same gold concentration (0.3 mg Au/g) as used in previous animal studies. A piece of EBT2 radiochromic film (30-µm active-layer sandwiched between 80/175-µm outer-layers) was inserted along the long axis of each vial and used to measure dose enhancement due to PIXE from GNPs. Vials were placed at center-of-modulation (COM) and 3-cm up-/down-stream from COM and irradiated with 5 different doses (2–10 Gy) using 10-cm-SOBP 160-MeV protons. After irradiation, films were cleaned and read to determine the delivered dose. A vial containing spherical GNPs (20 mg Au/g) was also irradiated, and gamma-rays from activation products were measured using a cadmium-telluride (CdTe) detector. Results: Film measurements showed no significant dose enhancement beyond the experimental uncertainty (∼2%). There was a detectable activation product from GNPs, but it appeared to contribute to dose enhancement minimally (<0.01%). Conclusion: Considering the composition of EBT2 film, it can be inferred that gold characteristic x-rays from PIXE and their secondary electrons make insignificant contribution to dose enhancement. The current investigation also suggests negligible dose enhancement due to activation products. Thus, previously-reported GNP-mediated proton dose

  8. Thermoelectrically cooled semiconductor detectors for non-destructive analysis of works of art by means of energy dispersive X-ray fluorescence

    CERN Document Server

    Cesareo, R; Castellano, A

    1999-01-01

    Thermoelectrically cooled semiconductor detectors, such as Si-PIN, Si-drift, Cd sub 1 sub - sub x Zn sub x Te and HgI sub 2 , coupled to miniaturized low-power X-ray tubes, are well suited in portable systems for energy-dispersive X-ray fluorescence (EDXRF), analysis of archaeological samples. The Si-PIN detector is characterized by a thickness of about 300 mu m, an area of about 2x3 mm sup 2 , an energy resolution of about 200-250 eV at 5.9 keV and an entrance window of 25-75 mu m. The Si-drift detector has approximately the same area and thickness, but an energy resolution of 155 eV at 5.9 keV. The efficiency of these detectors is around 100% from 4 to 10 keV, and then decreases versus energy, reaching approx 9% at 30 keV. Coupled to a miniaturized 10 kV, 0.1 mA, Ca-anode or to a miniaturized 30 kV, 0.1 mA, W-anode X-ray tubes, portable systems can be constructed, which are able to analyse K-lines of elements up to about silver, and L-lines of heavy elements. The Cd sub 1 sub - sub x Zn sub x Te detector ha...

  9. SiliPET: Design of an ultra-high resolution small animal PET scanner based on stacks of semi-conductor detectors

    Science.gov (United States)

    Cesca, N.; Auricchio, N.; Di Domenico, G.; Zavattini, G.; Malaguti, R.; Andritschke, R.; Kanbach, G.; Schopper, F.

    2007-03-01

    We studied with Monte Carlo simulations, using the EGSnrc code, a new scanner for small animal positron emission tomography (PET), based on stacks of double-sided semiconductor detectors. Each stack is composed of planar detectors with dimension 70×60×1 mm 3 and orthogonal strips on both sides with 500 μm pitch to read the two interaction coordinates, the third being the detector number in the stack. Multiple interactions in a stack are discarded. In this way, we achieve a precise determination of the first interaction point of the two 511 keV photons. The reduced dimensions of the scanner also improve the solid angle coverage resulting in a high sensitivity. Preliminary results of scanners based on Si planar detectors are presented and the initial tomographic reconstructions demonstrate very good spatial resolution limited only by the positron range. This suggests that, this is a promising new approach for small animal PET imaging. We are testing some double-sided silicon detectors, equipped with 128 orthogonal p and n strips on opposite sides using VATAGP3 ASIC by IDEAS.

  10. SiliPET: Design of an ultra-high resolution small animal PET scanner based on stacks of semi-conductor detectors

    International Nuclear Information System (INIS)

    We studied with Monte Carlo simulations, using the EGSnrc code, a new scanner for small animal positron emission tomography (PET), based on stacks of double-sided semiconductor detectors. Each stack is composed of planar detectors with dimension 70x60x1 mm3 and orthogonal strips on both sides with 500 μm pitch to read the two interaction coordinates, the third being the detector number in the stack. Multiple interactions in a stack are discarded. In this way, we achieve a precise determination of the first interaction point of the two 511 keV photons. The reduced dimensions of the scanner also improve the solid angle coverage resulting in a high sensitivity. Preliminary results of scanners based on Si planar detectors are presented and the initial tomographic reconstructions demonstrate very good spatial resolution limited only by the positron range. This suggests that, this is a promising new approach for small animal PET imaging. We are testing some double-sided silicon detectors, equipped with 128 orthogonal p and n strips on opposite sides using VATAGP3 ASIC by IDEAS

  11. Nanoimprinted Hybrid Metal-Semiconductor Plasmonic Multilayers with Controlled Surface Nano Architecture for Applications in NIR Detectors

    OpenAIRE

    Akram A. Khosroabadi; Palash Gangopadhyay; Steven Hernandez; Kyungjo Kim; Nasser Peyghambarian; Norwood, Robert A.

    2015-01-01

    We present a proof of concept for tunable plasmon resonance frequencies in a core shell nano-architectured hybrid metal-semiconductor multilayer structure, with Ag as the active shell and ITO as the dielectric modulation media. Our method relies on the collective change in the dielectric function within the metal semiconductor interface to control the surface. Here we report fabrication and optical spectroscopy studies of large-area, nanostructured, hybrid silver and indium tin oxide (ITO) st...

  12. Temperature and illumination intensity dependence of photoconductivity in sputter-deposited heteroepitaxial (100)CdTe layers

    Science.gov (United States)

    Das, S. R.; Cook, J. G.; Mukherjee, G.

    1991-06-01

    The photoconductivity behavior and the Hall-effect of sputter-deposited heteroepitaxial (100)CdTe layers grown at temperatures between 300 and 325 C were investigated. The (100)CdTe epilayers were found to be highly photoconductive and exhibited photoconductivity/dark conductivity ratios as high as 1 x 10 to the 6th at around 200 K. Photoconductivity showed a sublinear dependence on the illumination intensity and was higher at higher temperatures. It is shown that the model of Simmons and Taylor (1974) developed to explain photoconductivity in amorphous semiconductors is also applicable to the (100)CdTe epitaxial layers.

  13. Characterization and comparison of lateral amorphous semiconductors with embedded Frisch grid detectors on 0.18μm CMOS processed substrate for medical imaging applications

    Science.gov (United States)

    Hristovski, Christos; Goldan, Amir; Majid, Shaikh Hasibul; Wang, Kai; Shafique, Umar; Karim, Karim

    2011-03-01

    An indirect digital x-ray detector is designed, fabricated, and tested. The detector integrates a high speed, low noise CMOS substrate with two types of amorphous semiconductors on the circuit surface. Using a laterally oriented layout a-Si:H or a-Se can be used to coat the CMOS circuit and provide high speed photoresponse to complement the high speed circuits possible on CMOS technology. The circuit also aims to reduce the effect of slow carriers by integrated a Frisch style grid on the photoconductive layer to screen for the slow carriers. Simulations show a uniform photoresponse for photons absorbed on the top layer and an enhanced response when using a Frisch grid. EQE and noise results are presented. Finally, possible applications and improvements to the area of indirect x-ray imaging that are capable of easily being implemented on the substrate are suggested.

  14. Low-Mass WIMP Sensitivity and Statistical Discrimination of Electron and Nuclear Recoils by Varying Luke-Neganov Phonon Gain in Semiconductor Detectors

    CERN Document Server

    Pyle, M; Cabrera, B; Hall, J; Schnee, R W; Thakur, R Basu; Yellin, S

    2012-01-01

    Amplifying the phonon signal in a semiconductor dark matter detector can be accomplished by operating at high voltage bias and converting the electrostatic potential energy into Luke-Neganov phonons. This amplification method has been validated at up to |E|=40V/cm without producing leakage in CDMSII Ge detectors, allowing sensitivity to a benchmark WIMP with mass = 8GeV and cross section 1.8e-42cm^2 assuming flat electronic recoil backgrounds near threshold. Furthermore, for the first time we show that differences in Luke-Neganov gain for nuclear and electronic recoils can be used to discriminate statistically between low-energy background and a hypothetical WIMP signal by operating at two distinct voltage biases. Specifically, 99% of events have p-value<1e-8 for a simulated 20kg-day experiment with a benchmark WIMP signal with mass =8GeV and cross section =3.3e-41cm^2.

  15. Review of three-dimensional position sensing in semiconductor spectrometers

    International Nuclear Information System (INIS)

    With the growing availability of ASICs for low-noise multichannel readout, there is increasing interest in extracting three-dimensional position information from semiconductor gamma ray spectrometers fabricated with segmented electrodes. This presentation will review the basic principles of charge induction due to the motion of charge carriers in arbitrary geometry, and demonstrate how the relative shapes and amplitudes of induced signals can be used to deduce the original position of the charge carriers. Examples will be shown of work at the University of Michigan in which independent pulse height spectra have been recorded from over 2000 separate voxels in a 1 cm 3 sample of CdZnTe. Position-resolved spectra have also been obtained from CdTe and HgI2 room-temperature semiconductor detectors. Work at other laboratories with cooled germanium detectors has demonstrated the feasibility of three-dimensional position sensing, using pulse shape analysis and the transient 'spectator electrode' signals induced on multiple electrodes. One application of these approaches is to compensate for nonuniformity in the response of spectrometers throughout their volume. We will show the improvements that can be made in room temperature semiconductor spectrometers by digital correction and recombination of the multiple signals. Another application is using the position and energy information to reconstruct the direction of the incident gamma ray. Conventional 'Compton cameras' make use of separate detector elements to provide this information. In principle, the same process can be carried out in a single detector if each gamma ray interaction can be adequately resolved in energy and position. Progress in this direction will be reviewed. (author)

  16. First principles modeling of grain boundaries in CdTe

    Science.gov (United States)

    Chan, Maria K. Y.; Sen, Fatih; Buurma, Christopher; Paulauskas, Tadas; Sun, Ce; Kim, Moon; Klie, Robert

    The role of extended defects is of significant interest for semiconductors, especially photovoltaics since energy conversion efficiencies are often affected by such defects. In particular, grain boundaries in CdTe photovoltaics are enigmatic since the achievable efficiencies of CdTe photovoltaics are higher in polycrystalline devices as compared to single crystalline devices. Yet, despite recent advances, the efficiency of poly-CdTe devices are still substantially below the theoretical maximum. We carry out an atomistic-level study using Scanning Transmission Electron Microscopy (STEM), together with first principles density functional theory (DFT) modeling, in order to understand the properties of specific bicrystals, i.e. artificial grain boundaries, constructed using wafer bonding. We discuss examples of bicrystals, including some involving large scale DFT calculations, and trends in defect and electronic properties. This work was funded by DOE SunShot BRIDGE program.

  17. The detector control system of the ATLAS SemiConductor tracker during macro-assembly and integration

    Czech Academy of Sciences Publication Activity Database

    Abdesselam, A.; Barr, A.; Basiladze, S.; Böhm, Jan; Šťastný, Jan

    2008-01-01

    Roč. 3, - (2008), P02007/1-P02007/29. ISSN 1748-0221 R&D Projects: GA MŠk LA08032; GA MŠk 1P04LA212 Institutional research plan: CEZ:AV0Z10100502 Keywords : solid state detectors * large detector systems for particle and astroparticle physics * detector control systems Subject RIV: BF - Elementary Particles and High Energy Physics Impact factor: 0.333, year: 2008

  18. Application of microchips AMPL-8.3 and DISC-8.3 for work with semiconductor strip detectors

    International Nuclear Information System (INIS)

    The objective of the work was to widespread the sphere of microchips AMPL-8.3 and DISC-8.3 application to the silicon strip detectors. As a result two versions of preamplifiers were designed for 16-channel PCB ADB-16, intended for gaseous detectors. At present this electronics is used for methodical researches of detectors, for stand tests and creation of prototype systems for new high energy physics experiments. (authors)

  19. Phosphorus Diffusion Mechanisms and Deep Incorporation in Polycrystalline and Single-Crystalline CdTe

    Energy Technology Data Exchange (ETDEWEB)

    Colegrove, Eric; Harvey, Steven P.; Yang, Ji-Hui; Burst, James M.; Albin, David S.; Wei, Su-Huai; Metzger, Wyatt K.

    2016-05-01

    A key challenge in cadmium telluride (CdTe) semiconductors is obtaining stable and high hole density. Group I elements substituting Cd can form ideal acceptors but easily self-compensate and diffuse quickly. For example, CdTe photovoltaics have relied on copper as a dopant, but copper creates stability problems and hole density that has not exceeded 1015 cm-3. If hole density can be increased beyond 10^16 cm-3, CdTe solar technology can exceed multicrystalline silicon and provide levelized costs of electricity below conventional energy sources. Group V elements substituting Te offer a solution, but are very difficult to incorporate. Using time-of-flight secondary-ion mass spectrometry, we examine bulk and grain boundary (GB) diffusion of phosphorous (P) in CdTe in Cd-rich conditions. We find that in addition to slow bulk diffusion and fast GB diffusion, there is a fast bulk diffusion component that enables deep P incorporation in CdTe. Detailed first-principles calculations indicate the slow bulk diffusion component is caused by substitutional P diffusion through the Te sublattice, whereas the fast bulk diffusion component is caused by P diffusing through interstitial lattice sites following the combination of a kick-out step and two rotation steps. The latter is limited in magnitude by high formation energy, but is sufficient to manipulate P incorporation. In addition to an increased physical understanding, this result opens up new experimental possibilities for Group V doping in CdTe materials.

  20. Applications of CdTe to nuclear medicine. Annual report, February 1, 1977--January 31, 1978

    Energy Technology Data Exchange (ETDEWEB)

    Entine, G.

    1978-01-01

    The development of CdTe has now progressed to the point where a wide variety of prototype medical applications are being explored. It appears that as the more dramatic applications such as the camera became widely known, expanded interest will be developed for the more mundane but medically still useful areas of medicine such as probes and small arrays. The basic limitation to the increased use of CdTe in medicine remains an economic one as all applications must bear a heavy cost of fundatmental CdTe crystal and device research. A second problem is the fact that the existence of CdTe detectors is not known to most medical researches. This latter problem is being successfully addressed by this contract.