The Cryogenic Dark Matter Search (CDMS) experiment is an effort to detect dark matter
in the form of weakly interacting massive particles (WIMPs). CDMS utilizes cryogenic semiconductor
detectors in order to accomplish this. At the University of Minnesota the testing
and characterization of these detectors is one of the main responsibilities. To further improve
characterization of the detectors, it is important to reduce the number of background events
from reaching the detector as best as possible. This is especially significant in the case of
neutrons since they produce nuclear recoils in the crystal similar to what is expected of a WIMP;
these signals would be indistinguishable from each other in the data. Thus, the project was
to build a neutron shield made of high-density polyethylene which would surround the dilution
refrigerator where the detector was operated. Data was taken with the detector exposed to a Cf-
252 (neutron) source with and without the shield in order to determine the shielding capability
of the polyethylene. The data was analyzed and the results demonstrated a consistent shielding
effect on events appearing as nuclear recoils, suggesting that the neutron shield is fulfilling its
University of Minnesota M.S. thesis. Major: Physics. Advisor: Vuk Mandic. 1 computer file (PDF); viii, 65 pages.
Design, construction, and assessment of a neutron shield for CDMS test facilities..
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