Abstract
The Cryogenic Dark Matter Search (CDMS) searches for Weakly Interacting Massive Particles (WIMPs) with cryogenic germanium particle detectors. These detectors discriminate between nuclear-recoil candidate and electron-recoil background events by collecting both phonon and ionization energy from interactions in the crystal. Incomplete ionization collection results in the largest background in the CDMS detectors as this causes electron-recoil background interactions to appear as false candidate events. Two primary causes of incomplete ionization collection are suface and bulk charge trapping. Recent work has been focused on reducing surface trapping through the modification of fabrication methods for future detectors. Analyzing data taken with test devices shows that hydrogen passivation of the amorphous silicon blocking layer does not reduce the effects of surface trapping. Other data shows that the iron-ion implantation used to lower the critical temperature of the tungsten transition-edge sensors increases surface trapping, causing a degradation of the ionization collection. Using selective implantation on future detectors may improve ionization collection for events near the phonon side detector surface. Bulk trapping is minimized by neutralizing ionized lattice impurities. Detector investigations at testing facilities and at the experimental site in Soudan, MN have provided methods to optimize the neutralization process and monitor running conditions to maintain maximal ionization collection.
Original language | English (US) |
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Title of host publication | Low Temperature Detectors LTD-13 - Proceedings of the 13th International Workshop |
Pages | 643-646 |
Number of pages | 4 |
DOIs | |
State | Published - 2009 |
Externally published | Yes |
Event | 13th International Workshop on Low Temperature Detectors, LTD-13 - Stanford, CA, United States Duration: Jul 20 2009 → Jul 24 2009 |
Publication series
Name | AIP Conference Proceedings |
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Volume | 1185 |
ISSN (Print) | 0094-243X |
ISSN (Electronic) | 1551-7616 |
Other
Other | 13th International Workshop on Low Temperature Detectors, LTD-13 |
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Country/Territory | United States |
City | Stanford, CA |
Period | 7/20/09 → 7/24/09 |
Keywords
- CDMS
- Charge Collection
- Dark Matter
- SuperCDMS
ASJC Scopus subject areas
- General Physics and Astronomy