Development of a low background environment for the cryogenic dark matter search

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 in...

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Main Author: Da Silva, Angela Jane
Language:English
Published: 2009
Online Access:http://hdl.handle.net/2429/6243
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spelling ndltd-LACETR-oai-collectionscanada.gc.ca-BVAU.2429-62432014-03-14T15:41:00Z Development of a low background environment for the cryogenic dark matter search Da Silva, Angela Jane 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. 2009-03-19T23:19:01Z 2009-03-19T23:19:01Z 1996 2009-03-19T23:19:01Z 1996-05 Electronic Thesis or Dissertation http://hdl.handle.net/2429/6243 eng UBC Retrospective Theses Digitization Project [http://www.library.ubc.ca/archives/retro_theses/]
collection NDLTD
language English
sources NDLTD
description 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.
author Da Silva, Angela Jane
spellingShingle Da Silva, Angela Jane
Development of a low background environment for the cryogenic dark matter search
author_facet Da Silva, Angela Jane
author_sort Da Silva, Angela Jane
title Development of a low background environment for the cryogenic dark matter search
title_short Development of a low background environment for the cryogenic dark matter search
title_full Development of a low background environment for the cryogenic dark matter search
title_fullStr Development of a low background environment for the cryogenic dark matter search
title_full_unstemmed Development of a low background environment for the cryogenic dark matter search
title_sort development of a low background environment for the cryogenic dark matter search
publishDate 2009
url http://hdl.handle.net/2429/6243
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