Metallic Superconducting Bolometers for Rare Particle Detection

One of the major objectives in high energy particle physics and a top priority for the Department of Energy is the elucidation of the nature of dark matter, a discovery which would truly be transformative. In many cases, the ability to advance the research further is limited by the capabilities of the available detectors. Fortunately, recent advances in cryogenic bolometers have significantly improved detector sensitivity and background rejection, with sub-keV thresholds now possible. In this proposed effort, we will investigate metallic super-conducting bolometers, made of zinc and aluminum single crystals, designed for detecting low energy recoils. Such detectors, when operated at temperatures of 10-50 mK, should reduce sensitivity to background electromagnetic radiation (X-rays, gamma-rays) while achieving high sensitivity to low energy recoils.Radiation Monitoring Devices, Inc. (RMD), in collaboration with Massachusetts Institute of Technology (MIT), has recently begun to develop processes to purify and grow high purity single crystals. This work is an outgrowth of previous work done on the preparation of very high purity scintillator crystals. Initial samples of zinc and aluminum crystals have already been prepared. Preliminary data taken with a zinc crystal show high purity and low contamination of radiogenics. The proposed DOE SBIR effort should lead to sensitive superconducting detectors that can be used for the detection of neutrinos and dark matter candidates, such as WIMPS and axions. The essence of the proposed research is to perform a rigorous investigation of the purification and crystal growth of zinc and aluminum single crystals, and to characterize the purity and detection properties of the crystals produced. Bolometer detectors will be built with the necessary size, and tested at low temperatures by our collaborators at MIT. Commercial Applications and Other Benefits: Commercial and societal benefits of the proposed technology result from its uses. The proposed work would provide a new supply of radio-pure bolometer crystals that would enable new, higher sensitivity physics experiments to be designed and performed, advancing the frontier of scientific knowledge. The detectors could also be used to monitor the neutrino flux emitted by nuclear reactors to provide real time information of the status of the reactor cores. Techniques developed for ultra-pure, low-radioactivity crystal manufacturing could also be applied to many other materials in all areas of technology where the performance of devices depends on material purity, such as other devices used in scientific research, optical components, non-destructive testing, and homeland security.