Signal Processing for Energy and Position Measurement in Gamma-ray Detector Arrays

139 Signal Processing for Energy and Position Measurement in Gamma-Ray Detector Arrays--X-ray Instrumentation Associates, 2513 Charleston Road, Suite 207, Mountain View, CA 94043-1607; (415) 903-9980 Dr. Bradley H. Nelson, Principal Investigator Dr. William K. Warburton, Business Official DOE Grant No. DE-FG03-97ER82510 Amount: $75,000 Arrays of germanium detectors are used in nuclear physics experiments, at DOE supported facilities such as the GAMMASPHERE, to observe excited nuclear states that decay by emitting multiple gamma rays. These experiments currently reject so-called "Compton scatter" events, in which a gamma ray is not completely absorbed in one detector. An experiment called Gamma Ray Energy Tracking Array (GRETA) is being proposed that will use energy and position measurements within multiple detectors to reconstruct Compton scatter events, thereby increasing the efficiency for observing complex decays by as much as 1,000 times. However GRETA will require significantly more sophisticated pulse measurement electronics and computation than is currently employed. The Phase I of this project will develop a digital signal processing unit capable of measuring both energy and position of gamma rays in a detector array by analyzing the pulse shapes. In Phase II the end product will be a computer-controlled unit in the VXI instrument standard, which handles 12 or more detector channels. Commercial Applications and Other Benefits as described by the awardee: The first commercial application will be a unit for use in germanium detector array experiments. With only modest algorithm changes, this application can be extended to making pulse-shape corrections in arrays of mercuric iodide or cadmium zinc telluride room-temperature gamma-ray detectors, such as are used in nuclear inspection and nonproliferation detection work. Single channels of the instrument would make an excellent low-cost gamma-ray spectrometer, particularly for portable applications.