A major problem currently facing astrophysics and cosmology is the question of dark
matter. Although there is little doubt about the existence of dark matter, there is considerable
uncertainty about the abundance and nature of this matter. One possibility is
that dark matter consists of weakly interacting massive particles (WIMPs), such as the
lightest stable particle in supersymmetry models.
Direct detection experiments look for nuclear recoils from WIMPs scattering in a
detector. The first generation of direct detection experiments were ultimately limited by
radioactive backgrounds. The Cryogenic Dark Matter Search (CDMS) is a direct detection
experiment based on novel particle detectors operated at millikelvin temperatures that
provide intrinsic background rejection. This capability, however, is not 100% effective.
Therefore a low background environment is essential to the experiment.
To create such an environment, all possible background sources have been extensively
studied both by measuring the background contribution from muons, photons and neutrons
and by performing detailed Monte Carlo simulations of the photon and neutron
backgrounds. The results of this investigation, as discussed in this thesis, have influenced
all aspects of the CDMS experiment.
The initial site for the CDMS experiment is the Stanford Underground Facility. The
relatively high muon flux at this site due to its shallow depth was balanced against the
convenience of a local site with the unlimited access necessary for operating a complicated
cryogenic system and developing new detector technology. The cryostat used to house the detectors was designed to accommodate the extensive shielding necessary to reduce
the ambient backgrounds to acceptable levels and to minimize the amount of radioactive
contamination near the detectors. Simulations and measurements of the local backgrounds
led to a layered shield design that consists primarily of plastic scintillators to veto muons,
lead and copper to attenuate photons and polyethylene to moderate neutrons.
With the background rejection capabilities of the cryogenic detectors and the low background
environment created in the Stanford Underground Facility, we expect to extend
the current limit on WIMP dark matter by more than an order of magnitude and begin
testing models for the lightest supersymmetric particle. / Science, Faculty of / Physics and Astronomy, Department of / Graduate
| Identifer | oai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/6243 |
| Date | 05 1900 |
| Creators | Da Silva, Angela Jane |
| Source Sets | University of British Columbia |
| Language | English |
| Detected Language | English |
| Type | Text, Thesis/Dissertation |
| Format | 10416139 bytes, application/pdf |
| Rights | For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use. |
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