P. Ouvrier-Buffet

Cea Leti, Grenoble, Rhône-Alpes, France

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Publications (12)6.86 Total impact

  • Andrea Brambilla · P. Ouvrier-Buffet · G. Gonon · J. Rinkel · V. Moulin · C. Boudou · Loick Verger
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    ABSTRACT: A growing interest has recently been observed in high flux X-ray imaging detectors with energy discrimination or spectroscopy capabilities. In this study we evaluate the performances of energy sensitive CdTe and CdZnTe detectors for X-ray imaging at fluxes of up to 2 107 X/mm2/s in the 20-150 keV energy range. Linear array detectors made from 3 mm thick single CdTe or CdZnTe crystals have 16 pixels with an 800 in pitch. These detectors were coupled to an innovative custom-designed 16-channel fast spectroscopy front-end electronic circuit. For each channel, the signal is continuously digitized and a FPGA controls acquisition and reconstructs the energy spectra on 256 bins for each channel. The detector was tested under X-rays for fluxes in the 105 to 2 × 107 X/mm2/s range. The main problem encountered at such high fluxes is the multiplication of pile-up events that reduces count rate and degrades energy resolution. When a very short shaping time was used, dead time was lower than 50 ns, and an energy resolution of 11 keV full width at half maximum (FWHM) at 2 × 106 X/mm2 s and 20 keV (FWHM) at 107 X/mm2/ s was achieved. We also show imaging results that illustrate the interest of the spectral information provided by each pixel.
    No preview · Article · Feb 2013 · IEEE Transactions on Nuclear Science
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    ABSTRACT: This paper aims to experimentally evaluate a new material multidimensional method for material identification using a new CdTe spectrometric detector. LETI has developed a 16-channel fast read-out system capable of taking spectrometric measurements at count rates of more than 10<sup>7</sup> counts/s. This read-out system was coupled to CdTe linear array pixel detectors. A multidimensional analysis of the measured spectra has been conducted to perform material identification. The results show a decrease in false detection rate by a factor of up to 2 compared to an optimized dual counting approach applied on the same spectrometric raw data. Compared to a sandwich detector, the false detection rate decreases by a factor of more than 3 for thin objects. As a rule, the paper quantitatively demonstrates the continuous increase in performance and robustness with the number of detector energy counters.
    No preview · Article · Nov 2011 · IEEE Transactions on Nuclear Science
  • J. Rinkel · G. Beldjoudi · G. Gonon · A. Brambilla · V. Rebuffel · C. Boudou · P. Ouvrier-Buffet · L. Verger
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    ABSTRACT: This paper presents multi dimensional approaches for material identification applied on experimental X-ray measurements obtained with CdTe spectrometric detector. LETI has been developing a 16 channels fast read-out electronics capable to perform spectrometric measurements at count rates above 10<sup>7</sup> counts/s. The read-out electronics was coupled to CdTe linear array pixel detectors. A multidimensional analysis of the measured spectra has been developed to perform material identification. The results show a decrease of false detection rate by a factor up to 2 compared to an optimised dual counting approach applied on the same spectrometric raw data. Compared to a sandwich detector, the false detection rate is decreasing by a factor higher than 3 for thin objects. Generally, the paper demonstrates quantitatively the continuous performance and robustness increase with the number of detector energy channels.
    No preview · Conference Paper · Dec 2010
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    A. Brambilla · C. Boudou · P. Ouvrier-Buffet · F. Mougel · G. Gonon · J. Rinkel · L. Verger
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    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 10<sup>5</sup> to 2 10<sup>7</sup> photons.mm<sup>-2</sup>.s<sup>-1</sup>. An energy resolution of 15% at 50 keV (7.5 keV FWHM) was obtained at 10<sup>7</sup> photons.mm<sup>-2</sup>.s<sup>-1</sup>. Additionally, first X-ray images in counting mode obtained with a 16-channels linear detector module are shown.
    Preview · Conference Paper · Dec 2009
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    L. Verger · P. Ouvrier-Buffet · F. Mathy · G. Montemont · M. Picone · J. Rustique · C. Riffard
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    ABSTRACT: A new cadmium zinc telluride (CZT) portable spectrometric system called OMEGA has been developed at CEA/LETI for high-energy applications like spent fuel assay in response to needs in the nuclear industry. The unit has been designed to operate at room temperature under water. The CZT OMEGA system is based on a single 10×10×10 mm<sup>3</sup> CZT detector associated with a single electronics channel. To improve performance, the system incorporates several technologies including: an electrode design named the "Mixed" electrode which combines a noncontacting Frisch grid and the pixel field effect to obtain maximum sensitivity from the 10×10×10 mm<sup>3</sup> CZT detector, a single hybrid preamplifier designed to reduce noise, an electronics board configured to enhance count rate capabilities and finally, electron bi-parametric (BP) correction (pulse height corrected via measurement of rise time) to improve both energy resolution and detection efficiency. This paper reports the most recent results obtained with the CZT OMEGA spectrometric system at high energy (<sup>137</sup>Cs and <sup>152</sup>Eu sources) at both low and high count rate: spectrometric performance shows an energy resolution of 1% FWHM at 662 keV (0.8% at 1408 keV) from 1 kcps to 50 kcps, deteriorating to 2% FWHM at 200 kcps.
    Full-text · Article · Nov 2005 · IEEE Transactions on Nuclear Science
  • A. Ghis · P. Ouvrier-Buffet · N. Rolland · A. Benlarbi-Delai
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    ABSTRACT: n° de priorité : FR20010006365 20010515 ; également publié en tant que : WO02093182 (A1) 2002-11-21 ; EP1390769 (A1) 2004-02-25 ; US2004145391 (A1) 2004-07-29 ; FR2824969 (B1) 2004-04-02 ; US6954087 (B2) 2005-10-11 ; EP1390769 (B1) 2010-07-07
    No preview · Article · Nov 2002
  • A. Ghis · P. Ouvrier-Buffet · N. Rolland · A. Benlarbi-Delai · P.A. Rolland · D. Glay · D. Jaeger
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    ABSTRACT: A new technique leading to an accurate sampling of single shot high frequency signals is described. This technique provides 20 GHz sampling of electrical pulses up to 8 GHz bandwidth with a 60 dB dynamic range. The prototype of a transient digitizer involving this new principle is tested, with the goal of a new product development. We present the theory of the sampling operations, the outline of the prototype, the design and fabrication of an innovative set of specific GaAs MMICs, the assembling of the complete system and the first results obtained in performance characterization
    No preview · Conference Paper · Feb 2002
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    ABSTRACT: High-energy X-ray photons are generated by linear accelerators or flash X-ray sources. These pulsed sources produce a high number of photons in a very short time (from a few picoseconds to a few microseconds). CdZnTe detectors are well suited to detect such photons because of their high density and good sensitivity. The possible dynamic range can be very high (from 1 to more than 10 000 photons per pulse). Because of the short X-ray pulse duration, and the transport properties of the semiconductor, photon counting mode operation is not adopted. The only possibility is to integrate the charge provided by all the photons. In this paper, we will first present the behaviour of different HPBM CZT and THM CdTe:Cl single detectors under high-energy X-rays exposure. Then the performances such as dynamic range, linearity, signal-to-noise ratio and spatial resolution of a 2D detector prototype are presented. This detector is devoted to 60 ns flash radiography at several MeV. It is made by piling up 16×20×1 mm striped plates. Finally, the detector has 64×32 pixels of 1×1 mm2 surface and 40 mm in depth.The next step will be a 16×16×4×cm3 detector for high-energy flash radiography.
    Full-text · Article · Feb 2001 · Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment
  • A. Ghis · B. Riondet · N. Rolland · A. Benlarbi-Delai · P.A. Polland · D. Glay · P. Ouvrier-Buffet
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    ABSTRACT: A new technique leading to an accurate sampling of single shot high frequency signals is described. This technique provides 20 GHz sampling of electrical pulses up to 8 GHz bandwidth with a 60 dB dynamic range. The prototype of a transient digitizer involving this new principle is currently being tested, with the goal of a new product development. We will present the theory of the sampling operations, and the outline and conception of the prototype. For this purpose, a specific set of MMIC has been developed in a fast GaAs technology. The performance predicted from full wave circuits simulations will be presented.
    No preview · Conference Paper · Feb 2001

  • No preview · Article · Jan 2001
  • L. Verger · J. P. Bonnefoy · F. Glasser · P. Ouvrier-Buffet
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    ABSTRACT: There has been considerable recent progress in II-VI semiconductor material and in methods for improving performance of the associated radiation detectors. New high resistivity CdZnTe material, new contact technologies, new detector structures, new electronic correction methods have opened the field of nuclear and x-ray imaging for industrial and medical applications. The purpose of this paper is to review new developments in several of these fields. In addition, we will present some recent results at LETI concerning first the CdTe 2-D imaging system (20 × 30 mm2 with 400 × 600 pixels) for dental radiology and second the CdZnTe fast pulse correction method applied to a 5 × 5 × 5 mm3 CdZnTe detector (energy resolution = 5% for detection efficiency of 85% at 122 keV) for medical imaging.
    No preview · Article · Jan 1997 · Journal of Electronic Materials
  • L. Verger · J. P. Bonnefoy · A. Gliere · P. Ouvrier-Buffet · M. Rosaz
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    ABSTRACT: Simulated and associated experimental results of a high efficiency CdZnTe (CZT) radiation detector response for gamma-ray imaging applications are presented. The model of a high efficiency semiconductor gamma ray detector takes into account several different physical phenomena involved in the detection and correction processes, namely the geometry of the irradiation, the gamma-ray's interaction with the crystal, the physics of the semiconductor's charge collection, the electric field distribution and the pulse height correction method. A few important decoupling assumptions allow us to use a one dimensional charge collection simulation with a two-dimensional field model and a full three dimensional Monte-Carlo calculation of the gamma ray interactions. The model allows calculation of charge collection and gamma ray spectra for non uniform electric field distribution in either planar, striped or pixellated detector.The model takes also into account the new CZT fast pulse correction method and its associated noise by considering the pulse height and the rise time of electron signals (Bi-Parametric spectrum) for all gamma ray interactions. Specific simulated and experimental spectra at 122 keV are presented for CZT. First, basic spectral changes are calculated for variations in crystal and detector properties like mobility, trapping lifetime and electric field profilesSecond, new experimental results of the fast pulse correction method applied to different CZT detector grades are presented. This method allows to achieve a high detection efficiency (> 80 %) with a good energy resolution (< 6 % FWHM) at 122 keV for a 4×4×6 mm3 CZT detector. No specific contact geometry is needed and the unusual low applied bias voltage allows to limit the ageing and break voltage effects and also the dark current and its associated noise. This fast correction method is expected to be useful for medical imaging and other applications.Finally, simulated Bi-Parametric (BP) spectra expected with the fast pulse correction method according to the detector properties (electric field profiles, electron lifetime) are simulated and a qualitative comparison is provided.
    No preview · Article · Dec 1996 · MRS Online Proceeding Library