Fabrication of 2-cm thick TlBr detectors

Hitomi, Keitaro*; Maeda, Shigetaka   ; Nogami, Mitsuhiro*; Ito, Chikara   ; Watanabe, Kenichi*

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.