IEEE 2017 NSS/MIC/RTSD ControlCenter

Online Program Overview Session: R-02

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CZT Detectors I

Session chair: Andrea Zappettini
 
Shortcut: R-02
Date: Monday, October 23, 2017, 10:20
Room: Regency VI
Session type: RTSD Session

Contents

10:20 am R-02-1

Large Field of View XRD Imaging Detector System for Screening Baggage at Airports (#1727)

J. S. Iwanczyk1, N. Hartsough1, J. C. Wessel1, J. Kuksin1, W. Barber1

1 DxRay, Inc., Northridge, California, United States of America

Content

We have developed a very cost-effective direct-conversion compound semiconductor x-ray imaging array technology that easily scales to large area. This technology achieves much better energy resolution as compared to existing scintillation based detector technologies (indirect conversion) as well as emerging direct conversion solid state technologies from other groups. Our approach that achieves better energy resolution uses densely packed sensors in an edge-on configuration designed to achieve rapid complete charge collection in a compound semiconductor interconnected to a low noise application specific integrated circuit (ASIC) with the ability to readout the full spectral response from all individual array pixels. At the same time the large area and high spatial resolution of the detectors will allow systems to recognize diffraction patterns in a very short time.

Larger area detector arrays in a modular tile-able format will enable new spectroscopic imaging methods such as x-ray diffraction (XRD) to obtain the sensitivity and high output data speed (thus high speed of conveyer belts) to eliminate false alarms passed along from initial transmission imaging systems in real time or to operateas high speed stand alone XRD screening systems.The technical and engineering approach used to achieve large area involves the development of tile-able sensors and stackable panels, which can be tested individually before the construction of large area modules. Our XRD detectors provide an energy resolution of ~2 keV @ 60 keV full width at half maximum (FWHM) in a large area x-ray imaging array with high output count rates and a large dynamic range at room temperature.

Keywords: x-ray diffraction (XRD), x-ray imaging detector, screening baggage at airports
10:42 am R-02-2

Count rate and spectral performance of CdZnTe pixel arrays for high-flux x-ray applications (#3891)

M. Prokesch1

1 eV Products division, Kromek USA, Saxonburg, Pennsylvania, United States of America

Content

CdZnTe materials characterization and device testing for high-flux x-ray applications are the focus of this presentation. The crystals used in this study have been grown with the traveling heater method and are specifically engineered to support high-flux photon counting. Count rate and spectral response under x-ray fluxes up to 108pps/mm2 are evaluated on pixel array detectors. The effect of varying materials properties and operating conditions on device performance is illustrated.

Keywords: CZT, x-ray, high-flux, photon counting, CdZnTe, defects, polarization, characterization, THM
11:04 am R-02-3

 NANOPIX, IN-SITU VALIDATION OF THE MINIATURIZED GAMMA CAMERA (#4119)

V. Schoepff1, F. Carrel1, R. Abou Khalil2, A. Fauler3, M. Fiederle3, G. Amoyal1, Q. Adeline1, Z. Mekhalfa4, L. Tondut5

1 CEA, LIST, Sensors and Electronic Architectures Laboratory, GIF-SUR-YVETTE Cedex, France
2 AREVA, Direction Innovation, PARIS LA DEFENSE, France
3 X-ray Imaging Europe GmbH, FREIBURG, Germany
4 Areva -D&S-MSIS-Assitance, CEA Marcoule, Bagnols-Sur-Ceze, France
5 Areva NC, Establishment de La Hague, Beaumont Habgue, France

Content

Remote localization of radioactive hot spots is an important challenge for focusing on irradiating areas and reducing the exposition of workers during maintenance or decommissioning operations in nuclear facilities. To address this challenging issue, CEA LIST has been working since the nineties on the development of gamma cameras, which allow visualization of gamma-emitting spots in the field by the superimposition of gamma-ray images on a visible image of the scene. These developments led to two generations of gamma imagers, industrialized by Mirion Technologies (CANBERRA): CARTOGAM, in the mid-nineties and, more recently, GAMPIX, a second-generation gamma imager, based on Timepix pixelated detector, developed in the frame of the Medipix collaboration coordinated by CERN, hybridized to a 1 mm-thick CdTe sensor. GAMPIX, commercialized under the name iPIX, allowed reducing by a factor two the size of the system and by a factor ten its weight (15 cm for around 2 kg) compared to CARTOGAM (40 cm for around 20 kg).

Over the last two years, CEA LIST worked, in close collaboration with AREVA teams, on a further miniaturization of the system, named Nanopix. The development consisted in an important reduction of size and weight of each building blocks of GAMPIX imager, along with technological improvements. As an outcome of these developments, Nanopix reached a twice-smaller size and ten-time lighter weight than GAMPIX, with only 8 cm for a weight of 268 g. Since both its detector and collimator are based on the same architecture as GAMPIX, Nanopix performances were proven equivalent to GAMPIX during laboratory characterization. First results of characterization carried out by AREVA’s team, especially in La Hague processing plant, showed very good performances on each encountered situations.

This paper presents the development and performance evaluation of the gamma imager Nanopix in laboratory and field conditions. Current evolutions of the system will also be described.

Keywords: Gamma imaging systems, Gamma imager, Gamma camera, Timepix, CdTe sensor
11:26 am R-02-4

Transient current technique - Advantages and pitfalls of using it for characterization of radiation detectors (#1895)

E. Belas1, R. Grill1, J. Pekarek1, J. Pipek1, P. Praus1

1 Charles University, Institute of Physics, Prague 2, Czech Republic

Content

Transient current technique (TCT) is a powerful quick characterization method for testing the transport properties of detector-grade semiconducting materials and the charge collection efficiency (CCE) of radiation detectors. It provides direct information about the trapping and detrapping of generated charged carriers on shallow and deep traps and on the charge dynamics in biased detector and enables us to deduce both the lifetime of generated carriers and the electric field warping in the detector.

In this presentation we focus on the laser-induced TCT (L-TCT), which was selected for detail characterization of radiation detectors in our laboratory and existing setup allows us to measure current transients in multiple configurations and experimental arrangements involving tunable excitation intensity, wavelength, pulse frequency and focusing, time-correlated bias-to-pulse switching, temperature and additional steady-state optical excitation. Measurements on semiinsulating CdZnTe and GaAs are presented and advantages and disadvantages of using L-TCT for precise characterization of transport and spectroscopic properties of radiation detectors are discussed. Transport properties and CCE of prepared detectors are evaluated from the analysis of bias dependence of the shape of current waveforms (CWFs) based on the Shockley-Read-Hall trap assisted recombination model. The shape of CWFs using both continuous and pulsed bias modes is analyzed depending on the bias, illumination intensity, beam focusing, used preamplifier and metallization and surface processing. All experimental results are subjected to the theoretical analysis based on the Shockley-Read-Hall trap assisted recombination model using Monte Carlo simulation and the solution of the drift–diffusion and Poisson equations.

Keywords: Transient current technique, Transport properties, radiation detectors
11:48 am R-02-5

Gamma-Ray Imaging and Sensor Fusion: Gamma-Ray Vision in 3D and Color (#1938)

K. Vetter1, 2, A. Haefner2, R. Barnowski2, L. Mihailescu2, R. Pavlovsky1

1 UC Berkeley, Nuclear Engineering, Berkeley, California, United States of America
2 LBNL, Nuclear Science Division, Berkeley, California, United States of America

Content

Recent developments in the fabrication of compact and hand-portable gamma-ray imaging instruments in combination with the enormous advances in sensor technologies, data processing, and computer vision enable new means to fuse radiological with contextual information resulting in enhanced detection and localization capabilities relevant for nuclear safety and security. Employing contextual sensors such as visual cameras or LiDAR, it is now possible to reconstruct scenes and environments and to integrate gamma-ray image data into this scene in 3D in real time. The combination of a hand-portable and free-moving gamma-ray imager in combination with contextual sensors represents the analog to a photo camera, except that the picture is in 3D and in gamma-ray space. Adding energy sensitivity, we can represent the 3D gamma-ray picture also in "color". We have developed and demonstrated this concept of gamma-ray vision with our hand-portable High-Efficiency Multimode Imager HEMI, which was extended with visual cameras and structured light sensors. We have demonstrated the so-called scene-data fusion concept at the IAEA in Vienna or in evacuated areas in the Fukushima Prefecture in Japan. We have deployed this system in a hand-portable format and on an unmanned aerial helicopter in Japan. We will discuss the new concept of gamma-ray vision and show results from measurements in indoor and outdoor environments with the focus on the new capability to effectively map contamination in Fukushima. This not only enables the effective assessment of contamination in homes and neighborhoods in the Fukushima Prefecture, it helps concerned residents to "see" the radiation and to alleviate some of their fear.

Keywords: gamma-ray imaging, multi-modality data fusion, gamma-ray vision, fukushima