High-resolution Compton-suppressed CZT and LaCl/sub 3/ detectors for fission products identification

Room temperature semiconductor CdZnTe (CZT) detectors are currently limited to total detector volumes of 1-2 cm³, which is dictated by the poor charge transport characteristics. Because of this size limitation, one of the problems in accurately determining isotope identification is the enormous background from Compton scattering events. Eliminating this background will not only increase the sensitivity and accuracy of measurements, but will also help to resolve peaks buried under the background and peaks in close vicinity of others. We are currently developing a fission products detection system based on the Compton-suppressed CZT and LaCl₃(Ce) detectors. In this application the detection system is required to operate in a high radiation field. Therefore, a small 10 mm times 10 mm times 5 mm CZT and Oslash13 mm times 15 mm LaCl₃ detector are placed inside the center of a well-shielded Oslash76 mm by 76 mm long NaI detector. So far, we have been able to successfully reduce the Compton background by a factor of 3.7 to 4.0 for a ¹³⁷Cs spectrum. In this work, we will discuss the performance of this detection system using both CZT and LaCl₃ detectors. The results are compared with MCNP calculations.