Cd1-xZnxTe gamma-ray detector systems for monitoring special nuclear material

There is a widespread need for light-weight, low-power gamma-ray spectrometers suitable for monitoring special nuclear material (SNM) in safeguards applications. The detectors should be inexpensive to produce, have high energy resolution and sensitivity, and ideally they would be operable at room temperature. The focus of the present work is to (1) develop a field-ready, low power detector system for monitoring SNM storage containers as part of Sandia National Laboratories' Straight-Line Project and to (2) demonstrate the potential of a prototype system which has high energy resolution. The authors have investigated the use of cadmium zinc telluride (CZT) because it is one of the most promising solid state detector materials at this time. Due to its high average atomic number, CZT detectors have high gamma-ray stopping efficiency for U and Pu emissions. With proper system design, CZT detection systems can be made very portable and consume little power (< 20 mW). Thus, CZT detectors are ideal for use in portable systems that must operate for long periods of time from batteries. This paper describes the implementation of CZT detectors for SNM monitoring applications with emphasis on low power electronic readout. Methods for obtaining better energy resolution from CZT detectors are discussed and some results are presented using these methods