ROOM-TEMPERATURE SEMICONDUCTOR-DETECTORS FOR SAFEGUARDS MEASUREMENTS

A summary is given of the principal areas of application where CdTe de tectors are presently used by the IAEA in nuclear material safeguards. Hemispheric detectors with a sensitive volume of about 20 mm(3) have their principal application in the verification of irradiated nuclear material. Larger volume hemispheric detectors are used for the verific ation of unirradiated material. Their availability, however, is still limited. Problems with the commercial supply of detectors and with rug gedizing the design of the miniature detection probes need to be solve d. New results which are relevant for future applications are describe d. it has been shown that hemispheric detectors made of CdZnTe provide a resolution of 3-4% and a peak/Compton ratio larger than two for Cs- 137. Large volume planar CdZnTe have been used in conjunction with pul se shape discrimination electronics. The detector efficiency, however, still remains below the values expected from their geometric dimensio ns. A new technique to achieve single charge collection in large volum e CdZnTe detectors has been developed. Planar detectors with PIN struc ture and Peltier cooling have further improved. However, the problem o f long term stability has not been solved yet. Silicon detectors are i ncreasingly used in unattended radiation monitoring systems. They have a proven long term stability and can cover a signal range of 5-6 deca des if used with fast pulse counting electronics.