Special nuclear materials monitoring An application of CdxZn1−xTe detectors

Special nuclear materials (SNMs) are radioactive sources containing either 235U or 239Pu; materials that can be used in nuclear weapons. To monitor the extensive stockpiles of these materials in the US and former Soviet Union requires specialized instrumentation. This instrumentation must contain a sensor capable of detecting the gamma emissions from 235U or 239Pu, yet the instrument must be extremely reliable and consume little power. The performance of a SNM monitoring system, developed under project “Straight-line” at Sandia National Laboratories will be discussed. The system makes use of room temperature CdxZn1−xTe (CZT) detectors. CZT detectors are a good choice for this application because they have excellent stopping power for 235U or 239Pu photon emissions, and they draw very little current. Particular emphasis will be given to the problem of providing a suitable charge sensitive preamplifier and electronic readout system for a CZT detector that consumes little power.