Continued development of thallium bromide and related compounds for gamma-ray spectrometers

Abstract

Thallium bromide (TlBr) and related ternary compounds, TlBrI and TlBrCl, have been under development for room temperature gamma-ray spectroscopy due to high density, high Z and wide bandgap of the material. Low melting point and cubic crystal structure of selected compositions of these compounds facilitate crystal growth by melt techniques. Recent advances in material purification, crystal growth, and device processing have led to mobility–lifetime products of electrons in the mid 10 −3 cm 2/V range enabling working detectors of greater than 15 mm thickness to be fabricated. In this paper we report on our recent progress on TlBr detector development and first results from TlBr x Cl 1− x devices. Pulse height spectra will be presented from TlBr arrays as thick as 18 mm. Depth corrected spectra will also be presented. For a 5 mm thick TlBr array, energy resolution of less than 1% (FWHM at 662 keV) was obtained after depth correction.