Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2013
ABSTRACT In this paper we illustrate the core technologies at the basis of the European SPADnet p... more ABSTRACT In this paper we illustrate the core technologies at the basis of the European SPADnet project (www.spadnet.eu), and present the corresponding first results. SPADnet is aimed at a new generation of MRI-compatible, scalable large area image sensors, based on CMOS technology, that are networked to perform gamma-ray detection and coincidence to be used primarily in (Time-of-Flight) Positron Emission Tomography (PET). The project innovates in several areas of PET systems, from optical coupling to single-photon sensor architectures, from intelligent ring networks to reconstruction algorithms. In addition, SPADnet introduced the first computational model enabling study of the full chain from gamma photons to network coincidence detection through scintillation events, optical coupling, etc.
2009 IEEE Nuclear Science Symposium Conference Record (NSS/MIC), 2009
ABSTRACT The development of a novel energy resolved fast X-ray imaging detector is reported. The ... more ABSTRACT The development of a novel energy resolved fast X-ray imaging detector is reported. The device is based on pixellated cadmium telluride (CdTe) and cadmium zinc telluride (CdZnTe) detectors coupled to a custom designed 16-channel fast spectroscopy front-end electronic circuit. For each channel, a fast Analog to Digital Converter (ADC) continuously digitizes the signal from the detector pixel. A FPGA controls the acquisition and constructs the spectra on 256 energy bins for each channel. In this study, we measured the spectrometric performances with monochromatic X-rays from a synchrotron source at the European Synchrotron Radiation Facility (ESRF). We were able to acquire high-resolution pulse spectra for different X-ray energies and fluxes ranging from 105 to 2 107 photons.mm-2.s-1. An energy resolution of 15% at 50 keV (7.5 keV FWHM) was obtained at 107 photons.mm-2.s-1. Additionally, first X-ray images in counting mode obtained with a 16-channels linear detector module are shown.
Proceedings of SPIE - The International Society for Optical Engineering
Operating as a photoconductor, the sensitivity and the impulse response of semi-insulating materi... more 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 briefly discussed. Before developing picosecond measurements with integrated autocorrelation system, this paper explains high energy industrial tomographic application with large CdTe detectors (25 X 15 X 0.9 mm(superscript 3)) where spatial resolution, contrast, and wide dynamic are the main criteria. The excitation is typically microsecond(s) 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 a laser fusion experiment the excitation is in the range of 50 ps and we develop for such high band devices photoconductive structures able to study very short x-ray emission. Thin polycrystalline MOCVD CdTe films with picosecond response are an alte...
Conventional explosive detection systems (EDS) based on X-ray technologies are using dual-energy ... more Conventional explosive detection systems (EDS) based on X-ray technologies are using dual-energy radiography; they provide only a crude material characterization. Recently emerged semiconductors based X-ray detectors offer new capabilities in energy discrimination. This study is aiming at evaluating their interest for EDS. LETI-LDET laboratory has developed several pixellated CdTe/CZT detectors. For X-ray spectral radiography, a detector capable to operate at count rates above 10 7 counts/mm 2 s has been implemented, and associated to a multidimensional spectra analysis. We present the performance get for material identification on experimental data. Two complementary X-ray techniques are used in EDS: diffraction and backscatter techniques. Adapted detector prototypes have been developed. Experimental spectra are presented, and a dedicated processing method introduced for backscatter. For all these techniques, we discuss how CdTe/CdZnTe based spectrometric detectors are well-adapted.
IEEE Symposium Conference Record Nuclear Science 2004., 2004
ABSTRACT We report the timing performances between two cadmium zinc telluride (CZT) detectors equ... more ABSTRACT We report the timing performances between two cadmium zinc telluride (CZT) detectors equipped with a specific electrode geometry and a dedicated electronic setup for positron emission tomography (PET) application. The measured coincidence times reach 2,6ns Full Width at Half Maximum (FWHM) for a 500V bias voltage and 300keV energy threshold. Subsequently, a simulation study was carried out to assess the spatial and efficiency performances of these detectors which allow the Depth Of Interaction (DOI) measurement. Preliminary results show that the proposed design could reach a resolution better (1mm Full Width at Half Maximum instead of 2,5mm in the middle of the field of view) than what is achieved with the standard PET scintillation detectors. Experimental confirmation of this result is in progress.
The performances of standard gamma-cameras are limited by the well-known trade-off between spatia... more The performances of standard gamma-cameras are limited by the well-known trade-off between spatial resolution and sensitivity resulting from the collimator. To overcome this limitation, we have previously proposed a new approach named HiSens, which consists in the association of a pixelated CZT detector, new collimation geometry and dedicated reconstruction algorithms. Two major characteristics of the CZT detector are taken advantage of in this architecture: the availability of the depth of interaction (DOI) information and the fine pixelization.
ABSTRACT A new complete software tool for modeling EDXRD, called SinFullScat and based on the exi... more ABSTRACT A new complete software tool for modeling EDXRD, called SinFullScat and based on the existing simulator Sindbad has been developed in order to simulate diffracted spectra for any configurations. It enables to study the effects of all diffractometer's parameters on the output spectra. Depending on the application, inspected materials may have different structures, either amorphous (e.g. explosive liquids or tissues in medical application), either crystalline (drugs and explosive powders) or a mixture of both. SinFullScat aims to address all these kinds of materials.
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2013
ABSTRACT In this paper we illustrate the core technologies at the basis of the European SPADnet p... more ABSTRACT In this paper we illustrate the core technologies at the basis of the European SPADnet project (www.spadnet.eu), and present the corresponding first results. SPADnet is aimed at a new generation of MRI-compatible, scalable large area image sensors, based on CMOS technology, that are networked to perform gamma-ray detection and coincidence to be used primarily in (Time-of-Flight) Positron Emission Tomography (PET). The project innovates in several areas of PET systems, from optical coupling to single-photon sensor architectures, from intelligent ring networks to reconstruction algorithms. In addition, SPADnet introduced the first computational model enabling study of the full chain from gamma photons to network coincidence detection through scintillation events, optical coupling, etc.
2009 IEEE Nuclear Science Symposium Conference Record (NSS/MIC), 2009
ABSTRACT The development of a novel energy resolved fast X-ray imaging detector is reported. The ... more ABSTRACT The development of a novel energy resolved fast X-ray imaging detector is reported. The device is based on pixellated cadmium telluride (CdTe) and cadmium zinc telluride (CdZnTe) detectors coupled to a custom designed 16-channel fast spectroscopy front-end electronic circuit. For each channel, a fast Analog to Digital Converter (ADC) continuously digitizes the signal from the detector pixel. A FPGA controls the acquisition and constructs the spectra on 256 energy bins for each channel. In this study, we measured the spectrometric performances with monochromatic X-rays from a synchrotron source at the European Synchrotron Radiation Facility (ESRF). We were able to acquire high-resolution pulse spectra for different X-ray energies and fluxes ranging from 105 to 2 107 photons.mm-2.s-1. An energy resolution of 15% at 50 keV (7.5 keV FWHM) was obtained at 107 photons.mm-2.s-1. Additionally, first X-ray images in counting mode obtained with a 16-channels linear detector module are shown.
Proceedings of SPIE - The International Society for Optical Engineering
Operating as a photoconductor, the sensitivity and the impulse response of semi-insulating materi... more 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 briefly discussed. Before developing picosecond measurements with integrated autocorrelation system, this paper explains high energy industrial tomographic application with large CdTe detectors (25 X 15 X 0.9 mm(superscript 3)) where spatial resolution, contrast, and wide dynamic are the main criteria. The excitation is typically microsecond(s) 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 a laser fusion experiment the excitation is in the range of 50 ps and we develop for such high band devices photoconductive structures able to study very short x-ray emission. Thin polycrystalline MOCVD CdTe films with picosecond response are an alte...
Conventional explosive detection systems (EDS) based on X-ray technologies are using dual-energy ... more Conventional explosive detection systems (EDS) based on X-ray technologies are using dual-energy radiography; they provide only a crude material characterization. Recently emerged semiconductors based X-ray detectors offer new capabilities in energy discrimination. This study is aiming at evaluating their interest for EDS. LETI-LDET laboratory has developed several pixellated CdTe/CZT detectors. For X-ray spectral radiography, a detector capable to operate at count rates above 10 7 counts/mm 2 s has been implemented, and associated to a multidimensional spectra analysis. We present the performance get for material identification on experimental data. Two complementary X-ray techniques are used in EDS: diffraction and backscatter techniques. Adapted detector prototypes have been developed. Experimental spectra are presented, and a dedicated processing method introduced for backscatter. For all these techniques, we discuss how CdTe/CdZnTe based spectrometric detectors are well-adapted.
IEEE Symposium Conference Record Nuclear Science 2004., 2004
ABSTRACT We report the timing performances between two cadmium zinc telluride (CZT) detectors equ... more ABSTRACT We report the timing performances between two cadmium zinc telluride (CZT) detectors equipped with a specific electrode geometry and a dedicated electronic setup for positron emission tomography (PET) application. The measured coincidence times reach 2,6ns Full Width at Half Maximum (FWHM) for a 500V bias voltage and 300keV energy threshold. Subsequently, a simulation study was carried out to assess the spatial and efficiency performances of these detectors which allow the Depth Of Interaction (DOI) measurement. Preliminary results show that the proposed design could reach a resolution better (1mm Full Width at Half Maximum instead of 2,5mm in the middle of the field of view) than what is achieved with the standard PET scintillation detectors. Experimental confirmation of this result is in progress.
The performances of standard gamma-cameras are limited by the well-known trade-off between spatia... more The performances of standard gamma-cameras are limited by the well-known trade-off between spatial resolution and sensitivity resulting from the collimator. To overcome this limitation, we have previously proposed a new approach named HiSens, which consists in the association of a pixelated CZT detector, new collimation geometry and dedicated reconstruction algorithms. Two major characteristics of the CZT detector are taken advantage of in this architecture: the availability of the depth of interaction (DOI) information and the fine pixelization.
ABSTRACT A new complete software tool for modeling EDXRD, called SinFullScat and based on the exi... more ABSTRACT A new complete software tool for modeling EDXRD, called SinFullScat and based on the existing simulator Sindbad has been developed in order to simulate diffracted spectra for any configurations. It enables to study the effects of all diffractometer's parameters on the output spectra. Depending on the application, inspected materials may have different structures, either amorphous (e.g. explosive liquids or tissues in medical application), either crystalline (drugs and explosive powders) or a mixture of both. SinFullScat aims to address all these kinds of materials.
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