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Watanabe, Kenichi*; Hitomi, Keitaro*; Nogami, Mitsuhiro*; Maeda, Shigetaka; Ito, Chikara; Tanno, Takashi; Onabe, Hideaki*
no journal, ,
TlBr is a compound semiconductor with a high atomic number, high density and a wide bandgap, and is being developed as a gamma-ray detector material that can be operated at room temperature and has high detection efficiency. There is neutron diffraction in order to establish a crystal quality evaluation method for improving the yield in device fabrication, but the facilities that can be implemented are limited to large facilities such as J-PARC. The Electron Backscatter Diffraction (EBSD) image, which is one of the electron beam diffractions, can be obtained with an electron microscope, but only the information on the crystal surface can be obtained. In this study, the crystal orientation image was acquired for the TlBr crystal by neutron Bragg dip imaging, which is one of the neutron diffractions, and EBSD. By comparing both images, the applicability to a simple EBSD crystal quality evaluation method was examined.
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.