Performance tests of large area position-sensitive planar germanium detectors with conventional and amorphous contacts

Abstract

Large area position-sensitive planar germanium wafers are increasingly being used for a variety of gamma-ray imaging and tracking tasks. Position sensitivity can be achieved through measuring charge collected on orthogonal strip electrodes, and by digital pulse shape analysis. However, the development of this detector technology has been slow, and criteria to measure improved performance have not been well established. We have studied 93 and 88 mm square segmented detectors of 20 mm thickness made with conventional boron and lithium electrodes, and two 100 mm circular segmented detectors of 14 mm thickness with amorphous germanium contacts. We have compared these detectors with a planar detector of 15 mm thickness. Conventional energy resolution tests of individual strips are insufficient to fully categorize the performance of the position sensitive detectors. We propose some basic tests which can rapidly quantify any segmented detector characteristics, and show potential inadequacies which become important when imaging or tracking is attempted.