Speaker
Description
Thallium Bromide (TlBr) semiconductor, known for its high stopping power and wide energy band gap, holds promise as a room temperature gamma ray detector. In this study, we fabricated and characterized a TlBr detector, assessing its performance in energy resolution and timing capability through simultaneous analysis of electric charge and Cherenkov light. TlBr crystals (5 mm × 5 mm × 5 mm) equipped with Tl electrodes were utilized, featuring a planar cathode (3.9 × 3.9 mm²) and a pixelated anode (1.5 × 1.5 mm²) surrounded by an additional Tl electrode with 1 mm width. Au wire linked the pixelated electrode to a charge-sensitive preamplifier. A single-pixel silicon photomultiplier (SiPM) was employed to detect Cherenkov light, mounted between the Tl electrodes, and connected to the preamplifier, with the crystal surface covered by Teflon tape for enhanced conversion efficiency. Operating at a bias voltage of 500 V, waveform analysis revealed charge signal rise times of approximately 10 µs and Cherenkov light rise times in the nanosecond range. Gamma irradiation from a Cs-137 source was used to evaluate the performance of detector, with output waveforms processed using a trapezoidal filter. Depth of interaction (DoI) correction enhanced energy resolution, improving from 4.5% full width at half maximum (FWHM) to 1.96% FWHM at 662 keV energy. A linear relationship between DoI parameter and drift time was observed, with drift times of electron ranging from a few to about 20 µs for DoI parameters between 0 and 1. Time resolution was assessed using Cherenkov light signals from two TlBr systems exposed to 511 keV photon pairs from a Na-22 source, with anticipated time resolution values reaching several hundred picoseconds. TlBr detector shows a potential as a room temperature gamma ray detector, demonstrating promising characteristics even under stringent requirements for energy resolution and timing performance.
