Improving The Efficiency Of A Portable Room-temperature Czt Gamma-ray Spectrometer

Abstract. - We have characterized a prototype of a portable high-resolution room temperature gamma-ray spectrometer that works with 4x4 arrays of Cadmium-Zinc-Telluride (CZT) crystals to improve on its performance, compensate for crystal defects, and eliminate the necessity of buying high quality crystals at excessive costs to obtain a higher energy resolution. Lifetime and leakage current measurements were performed on the CZT crystal detectors to test their efficiency. To ensure that the crystals used in the arrays were fit for the task, the crystals were tested for carrier lifetime and leakage current, before testing the finished prototype and comparing its results with those of a High-purity Germanium (HPGe) detector. To measure carrier lifetime, two tests were performed: Time-of-Flight, which measures carrier drift time and amplitude, and spectroscopy to identify peak position and calculate lifetime through Hecht’s equation. Leakage current was measured in the bulk and surface of the crystals to analyze losses and noise in the collected data due to defects in the crystals, and they are compared to the leakage current of the whole crystals to see at what part of the crystal does most of the leakage current come from. The prototype was assembled and tested by identifying the following radioactive sources: 137Cs, 241Am, 238U, and 232Th. The radiation peaks were identified using Cambio software. Test results were plotted in OriginLab analyze the relation between amplitude and drift time on Time of Flight measurements, the relation between applied voltage and peak position in Hecht’s equation measurements, and the relation between applied voltage and amplitude of leakage current in leakage current measurements. Interactive Data Language (IDL) was used to calculate the carrier lifetime of the crystals, their resistivity, and to analyze the data given by the detector. A brick of unknow composition was used for shielding, and after realizing that it was radioactive, it was analyzed by the detector and the results were compared with those of a HPGe detector used on the same brick. The brick serves as a proof of the efficiency of the detector and all the potential applications it has.