Design a two-dimensional alpha surface contamination monitoring system using micro-pattern gaseous detectors (MPGDs) (original) (raw)
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Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2018
In this study, the design, simulation and construction of three micro pattern gas-detectors, THGEM, with different geometric dimensions are presented. Moreover, their ability of operation in SQS mode to determine the incident rays position without using any conventional imaging system is investigated. In the presence of UV absorbing gas mixtures, the proportional mode of the gas detector operation is followed by SQS mode as soon as the visible light column appears at the ray entrance location. In the method employed, each THGEM hole as an image pixel independent of other holes can operate in SQS mode with emerging a light column. As a consequence, it can be used for alpha beam imaging since the brightness of each hole at a certain voltage is proportional to the number of primary electrons entering the hole.
Advances in the Micro-Hole & Strip Plate gaseous detector
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2003
We report on the performance of a new gaseous electron multiplier: the Micro-Hole & Strip Plate (MHSP). It consists of two independent charge-amplification stages in a single, double-sided micro-structured electrode, deposited on a thin insulating substrate. Charge gains in excess of 10 3 were obtained in a MHSP operated with soft X-rays in Ar/CO 2 (70/ 30). We present the results of a systematic study of the MHSP properties and those of a double-stage GEM+MHSP multiplier. Applications to gaseous photomultipliers are discussed. r
Imaging of alpha emitters in a field environment
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2015
Imaging of alpha emitters Optical detection of alpha emitters Stand-off detection of alpha emitters a b s t r a c t Cameras sensitive to ultraviolet light can be applied to detection of surface contamination induced by alpha particle emitters. When absorbed in air, alpha particles excite nitrogen molecules and the radiative relaxation creates a faint light emission. This radioluminescence can be used for detection purposes, provided that background lighting levels are low. In this work, three low-light sensitive camera technologies (CCD, EMCCD and ICCD) were utilized in a nuclear facility, and their performance in detecting alpha emitters was investigated. The results show that low readout noise is essential for the detection of radioluminescence, as it allows short exposure times to be used. The ICCD camera was found to perform slightly better than the EMCCD camera in the field, while both enable the detection of MBq level alpha activities in 100 s in the test configuration (camera-target distance 0.5 m). Overall, the cameras and techniques used in this study are shown to be effective in detecting alpha emitters in a standard glovebox. This technology can be applied to nuclear security, safety and safeguards, when stand-off detection of alpha emitters is required.
2018
The characterization and the localization of the radiological contamination on surfaces is of first importance for the decommissioning process of a nuclear facility. Yet, there is cur-rently no device capable of giving a real-time image of the surface contamination by et945; or et946; emitters. The MAUD project (supported by the French agency ANDRA) is aiming at develop-ing a new type of portable detector capable of reconstructing the image of the radioactivity, in real-time, on a solid surface.In this paper, we present the technological developments we performed in order to real-ize the prototype of the MAUD project. We discuss the optimization of the detector type, size and thickness as well as the choice of the read-out electronic. The characterization of the detector response to ionizing radiations will be shown and compared to the numerical simulation used during the development.
Development of an alpha dust monitor using a GPS scintillator plate
Radiation Measurements, 2019
A dust monitor with a silicon surface barrier detector (SSBD) is introduced at a nuclear fuel facility to detect airborne contamination of 238 Pu and 239 Pu released by past accidents. However, an SSBD frequently produces false alarms, especially in a room with high humidity. To develop a highly reliable dust monitor, we developed an alpha-particle spectrometer based on a cerium-doped Gd 2 Si 2 O 7 (GPS) scintillator plate and a photomultiplier tube (PMT). The GPS scintillator plate is hexagonal and 50 mm in diameter, and the scintillator layer is approximately 40 μm. An output signal from the PMT is amplified by a preamp and transferred to an MCA. Then, an energy spectrum is displayed in real time. The 241 Am alpha source, Rn progeny collected on the air filter, and a PuO 2 particle were measured by our developed spectrometer. The energy resolution for 5.5-MeV alpha particles was ∼11.9% ± 0.2% of the FWHM. The efficiency was 92%, and it had a uniform sensitivity. By applying an energy window, the count-rate of the Rn progeny decreased by 77%. The GPS scintillator plate was able to measure the alpha spectrum even though the GPS scintillator got wet. Therefore, the alpha dust monitor using the GPS scintillator plate is ideal for detecting alpha-particle emitters in places lacking temperature and humidity controls, such as the outside of buildings.
The BetaCage, an ultra-sensitive screener for surface contamination INTRODUCTION AND DETECTOR DESIGN
Material screening for identifying low-energy electron emitters and alpha-decaying isotopes is now a prerequisite for rare-event searches (e.g., dark-matter direct detection and neutrinoless double-beta decay) for which surface radiocontamination has become an increasingly important background. The BetaCage, a gaseous neon time-projection chamber, is a proposed ultra-sensitive (and nondestructive) screener for alpha-and beta-emitting surface contaminants to which existing screening facilities are insufficiently sensitive. Sensitivity goals are 0.1 betas keV −1 m −2 day −1 and 0.1 alphas m −2 day −1 , with the former limited by Compton scattering of photons in the screening samples and (thanks to tracking) the latter expected to be signal-limited; radioassays and simulations indicate backgrounds from detector materials and radon daughters should be subdominant. We report on details of the background simulations and detector design that provide the discrimination, shielding, and radiopurity necessary to reach our sensitivity goals for a chamber with a 95 × 95 cm 2 sample area positioned below a 40 cm drift region and monitored by crisscrossed anode and cathode planes consisting of 151 wires each.
Progress with micro-pattern gas detectors
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2002
Micro-pattern gas detectors are position-sensitive proportional counters whose sense electrodes are constructed using micro-electronics, thin-film or advanced PCB techniques. The feature size attainable using these methods is of the order of a few microns and the detectors demonstrate excellent spatial resolution and fast charge collection.
Imaging gaseous detector based on micro-processing technology
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1999
The development of gaseous detectors has been exciting again since the appearance of a MicroStrip Gas Chamber(MSGC) in 1988, which is made using a microelectronics technology. These days lots of variations of the advanced gaseous detectors are being intensively studied in the world. We have developed the two-dimensional MSGC having a 10 cm square detection area and the ultra fast readout system for a real time X-ray imaging. The MSGC was made using Multi-Chip Module (MCM) technology, and has a very thin substrate of 17 µm, lots of thin anodes and back strips both with 200 µm pitches. This enables us to get fast digital X-ray images with recording both the timing and an energy of each X-ray photon. In addition, an intermediate gas multiplier has been realized using a capillary plate having a conductive surface of a capillary. The MSGC combined with the conductive capillary plate can be steadily operated with a high gain under intense irradiation. Here we also report new approaches of X-ray crystal structure analyses using timing information obtained by the MSGC.
Simulation and First Test of a Microdosimetric Detector Based on a Thick Gas Electron Multiplier
IEEE Transactions on Nuclear Science, 2000
We present design of a new microdosimetry detector based on thick gas electron multiplier (THGEM). A prototype detector was designed for a cylindrical sensitive volume with 5 mm diameter and 5 mm height. To optimize the avalanche gain, the electron avalanche process was modeled by varying THGEM thickness, hole diameter and high voltage bias for the tissue-equivalent propane gas. For a THGEM with 0.6 mm thickness and 0.3 mm hole diameter, the theoretical avalanche gain reached 200 at a 800 V THGEM bias. The prototype detector was fabricated and tested using the McMaster 7 Li(p n) neutron source.
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Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1999