Segmentation of the Outer Contact on P-Type Coaxial Germanium Detectors

Segmented germanium detector arrays are needed by the DOE for the characterization of low-level radioactive samples. In addition, the same detector arrays could perform important fundamental physics measurements, including the search for rare-events like neutrinoless double-beta decay. However, because of their complexity, these segmented coaxial detectors are expensive and available only after relatively long lead times. Improved fabrication techniques would greatly reduce costs and improve the availability of these segmented detectors for the low-level counting community. Therefore, this project will experimentally investigate alternative techniques for making segmented contacts on p-type coaxial germanium detectors, which would be a much cheaper alternative to the segmented n-type coaxial detectors currently proposed. However, the difficulties associated with the segmentation of conventional thick lithium-diffused contacts must be addressed. Phase I experimentally evaluated detector fabrication techniques appropriate for segmented p-­type coaxial detectors, and a fabrication recipe was established. In Phase II, the viability of alternative segmented detector contacts, as a competitive solution to the contacts established during Phase I, will be established. The best overall technique will be used to fabricate a large segmented p-­type coaxial detector as a demonstration. Commercial Applications and other Benefits as described by the awardee: The new germanium detector technology should provide better detector performance at lower cost for the measurement of low-activity radioactive sources. Applications of interest include national security (nuclear nonproliferation, nuclear explosion monitoring), areas of scientific importance (e.g., new levels of sensitivity in the Majorana search for neutrinoless double­beta decay), medical imaging, and x-ray detection