Improving the Radiation Damage Resistance of Germanium Detectors

Arrays of germanium gamma-ray detectors are used for nuclear physics experiments at DOE particle accelerator facilities. Energetic massive particles from the accelerator degrade the performance of the detectors and ultimately limit their use. This problem pertains to the currently-existing Gammasphere detector array at Argonne National Laboratory as well as to the next generation detector arrays to be instrumented at the Rare Isotope Accelerator. This project will develop detector cooling technology to greatly reduce or eliminate the radiation damage problem. Phase I will identify the coldest detector temperature practically achievable with Stirling-cycle mechanical coolers. Tests will be conducted to identify noise problems that may be introduced by the vibrations of the cooler. If the detector temperature can be made cold enough, without significant noise from the cooler, the colder temperature can greatly reduce or eliminate radiation damage effects in germanium detectors. Commercial Applications And Other Benefits as described by the Applicant: These ultra-cold mechanically-cooled detectors should be more reliable and have better performance for longer time durations in nuclear physics beam line environments. Other potential applications that face radiation damage include satellite-based detectors (from energetic cosmic rays), oil well logging, and neutron activation analysis. Aside from the improvements with respect to radiation damage, this technology eliminates the liquid-nitrogen requirement for large volume germanium detectors, allowing the detectors to be used in a wider range of environments where liquid nitrogen may not be available.