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Rodriguez, D.; Koizumi, Mitsuo; Rossi, F.; Takahashi, Tone
Proceedings of 2022 IEEE Nuclear Science Symposium, Medical Imaging Conference and Room Temperature Semiconductor Detector Conference (2022 IEEE NSS MIC RTSD) (Internet), 3 Pages, 2022/12
Nakamura, Tatsuya; To, Kentaro; Koizumi, Tomokatsu; Kiyanagi, Ryoji; Ohara, Takashi; Ebine, Masumi; Sakasai, Kaoru
Proceedings of 2022 IEEE Nuclear Science Symposium, Medical Imaging Conference and Room Temperature Semiconductor Detector Conference (2022 IEEE NSS MIC RTSD) (Internet), 2 Pages, 2022/11
A new thin position-sensitive scintillation neutron detectors have been developed to replace present scintillation detectors in SENJU diffractometer at J-PARC MLF. The SENJU diffractometer originally composed of 37 position-sensitive detectors, where each detector has neutron sensitive area of 256 
256 mm with a pixel size of 4 4 mm. To renew some original detectors the new detectors have been developed based on ZnS scintillator and wavelength-shifting fibers technology. The developed replacement detectors were designed with a thin thickness of 12 cm, which is 40% of the original detector. The new detectors have also improved detector performances to the original ones in terms of detection efficiency (
60% for 2-A neutrons) and count uniformity (5-8%). The produced six detector modules have been implemented to the beamline after checking their detector performances in the lab.
To, Kentaro; Nakamura, Tatsuya; Sakasai, Kaoru; Yamagishi, Hideshi*
Proceedings of 2022 IEEE Nuclear Science Symposium, Medical Imaging Conference and Room Temperature Semiconductor Detector Conference (2022 IEEE NSS MIC RTSD) (Internet), 3 Pages, 2022/11
A real-time data display and storage module was developed for time-of-flight neutron measurement. The module can display real-time experimental data from two-dimensional neutron detector in a two-dimensional image, one-dimensional projection images in X- and Y-axis, and time-of-flight spectra. The module has two modes of operation: standard mode, and simple-display mode. The simple-display mode only displays the experimental results on the monitor and can operate faster than that in the standard mode because the module uses the limited function. Therefore, the simple-display mode is also useful for measurement of high-counting rate neutrons. Operation test using test pulses were performed to confirm the operating speed of the module. The module in standard and simple-display mode could measure the continuous test pulses without counting losses with a frequency of 1.0 and 1.6 MHz, respectively.
Rossi, F.; Koizumi, Mitsuo; Rodriguez, D.; Takahashi, Tone
Proceedings of 2022 IEEE Nuclear Science Symposium, Medical Imaging Conference and Room Temperature Semiconductor Detector Conference (2022 IEEE NSS MIC RTSD) (Internet), 2 Pages, 2022/11
Kitayama, Yoshiharu; Nogami, Mitsuhiro*; Hitomi, Keitaro*
no journal, ,
Morishita, Yuki
no journal, ,
During the decommissioning process of nuclear facility sites, such as the Fukushima Daiichi Nuclear Power Station (FDNPS), radioactive contamination due to alpha, beta, and gamma nuclides is present. To accurately detect these nuclides, a new phoswich alpha/beta/gamma detector is proposed and developed. A portable alpha/beta/gamma radiation continuous air-monitoring system is also developed using the proposed phoswich detector for detecting unknown radioactive air contamination. The developed phowich detector features a 6 mm 6 mm 6 mm-stilbene scintillator (first layer) and a 6 mm 6 mm 6 mm-Gd
(Ga, Al)
O
(Ce) (GAGG) scintillator (second layer). The bottom of the GAGG scintillator is optically coupled to a silicon photomultiplier (SiPM). The proposed phoswich detector is capable of successfully separating alpha, beta, and gamma nuclides by applying the pulse-shape discrimination (PSD) technique. The alpha energy resolution of the 5.5 MeV alpha particles using was 22.1% at the full width at half maximum (FWHM), whereas the gamma energy resolution of the 0.662 MeV gamma rays was 10.3%FWHM. The energy spectra obtained from the simulations agree well with those obtained from measurements. Continuous alpha-nuclide air measurements were conducted in the basement of a concrete building, where the 
Rn concentration was approximately 200 Bq/m
, using the developed portable continuous air-monitoring system. The measured peaks, which correspond to 
Bi (6.1 MeV), 
Po (7.7 MeV), and Po (8.8 MeV), were observed in the alpha spectrum by separating beta and gamma rays. Therefore, the developed monitoring system can be potentially efficient for the early detection of unknown released radioactive materials.
Hitomi, Keitaro*; Maeda, Shigetaka; Nogami, Mitsuhiro*; Ito, Chikara; Watanabe, Kenichi*
no journal, ,
A 2-cm thick pixelated TlBr detector was fabricated in this study. A 50-mm diameter TlBr crystal was grown by the Bridgman-Stockbarger method using zone-purified materials. A pixelated TlBr detector was fabricated from the grown crystal with the dimension of 20 mm 20 mm 20 mm. The planar cathode and pixelated anodes were constructed on the crystal by vacuum evaporation of Tl. The anode consisted of 16-pixel electrodes (3 mm 3 mm) surrounded by a guard ring. A charge-sensitive preamplifier was connected to a pixel electrode on the device. The output signals from the preamplifier were recorded with a digitizer. The acquired signal waveforms were analyzed with a PC event by event for obtaining pulse-height spectra. The cathode surface of the pixelated TlBr detector was irradiated with an Am-241 gamma-ray source at room temperature. The applied bias voltage to the cathode was 2000 V. A clear full-energy peak corresponding to 59.5-keV gamma rays was obtained from the detector. The clear full-energy peak of 59.5-keV gamma-ray was reflecting the good electron transport property of the TlBr crystal.
Watanabe, Kenichi*; Nogami, Mitsuhiro*; Hitomi, Keitaro*; Maeda, Shigetaka
no journal, ,
Thallium bromide (TlBr) is a semiconductor attractive for gamma-ray detectors. TlBr detectors have been shown excellent energy resolution, however, these results were obtained from small crystal detectors. The next step of TlBr development is to increase the detector size and improve the yield rate of detector production. Therefore, we would like to establish a crystal quality evaluation procedure to improve the yield rate of detector production. As the crystal quality evaluation methods, we apply the neutron Bragg-dip imaging, which is based on the neutron diffraction technique, and the electron backscattering diffraction. The results obtained by the both techniques are compared. The both techniques shows almost the same information. We concluded that the TlBr crystal quality can be efficiently evaluated by complementarily combining the both techniques.
