Development of Reliable Segmented Germanium Planar Detector Systems for Nuclear Physics

72564-The nuclear physics research supported by DOE has a fundamental need for instruments that detect photons (x- and gamma rays). Segmented germanium detectors can provide better position and energy resolution than any other practical detector system. Although no fundamental technical roadblocks should prevent the ultimate production of commercially viable instruments based on segmented germanium detectors, this project will address several detailed technical issues that still must be solved. Phase I designed and fabricated a first generation, variable temperature detector system, which had 42 x 42 strips laid out on a 2-mm pitch. All the hardware needed to key, fixture, and fabricate the detector were built. A 13-mm thick 101-mm diameter high purity germanium wafer was obtained for the system. The feasibility of reliably using amorphous germaium contacts at temperatures up to at least ~97K was demonstrated. Phase II will design and fabricate two cryostats for measuring fundamental germanium detector physics properties (including surface channel effects, contact barrier heights, and charge collection effects caused by the gap between the strips). A second generation detector system, using 120-mm diameter wafer, will be designed, fabricated, and evaluated. The detector will be loaned to nuclear physicists for more extensive evaluation. Commercial Applications and Other Benefits as described by awardee: In addition to applications in nuclear physics, segmented germanium detectors should have very widespread commercial applications, with medical imaging likely to be the largest. Other applications include imaging detectors for Nuclear Nonproliferation and Homeland Defense and detectors for gamma ray astrophysics.