Development of a gamma ray monitor using a CdZnTe semiconductor detector

The aim of this study was to develop a new X ray and gamma ray monitor using the CdZnTe semiconductor detector, which has high sensitivity at room temperature. The pulse height spectra and the detection efficiencies of a 10 mm x 10 mm by 2 mm thick CdZnTe detector were measured in the energy range of 10 keV to 1.8 MeV by using monoenergetic X ray and gamma ray sources. The measured results showed very good agreement with the results calculated using the EGS4 Monte Carlo code taking into account the charge collection efficiency in the detector. By using two CZT detectors of 10 mm x 10 mm x 2 mm and 3 mm x 3 mm x 2 mm coupled with a filter, the weighted sum of a few energy channels with different cut-off energies was finally found to achieve a flat energy response with an equivalent dose (counts per microSv) within +/-30% or +/- 10% deviation.