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Bulk and Surface Charge Collection: CDMS Detector Performance and Design Implications

Bailey, C. N. and Ahmed, Z. and Filippini, J. and Golwala, S. R. and Moore, D. and Ogburn, R. W. and Wang, G. (2009) Bulk and Surface Charge Collection: CDMS Detector Performance and Design Implications. In: Low Temperature Detectors, LTD 13. AIP Conference Proceedings. No.1185. American Institute of Physics , Melville, NY, pp. 643-646. ISBN 978-0-7354-0751-0.

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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.

Item Type:Book Section
Related URLs:
URLURL TypeDescription
Filippini, J.0000-0001-8217-6832
Golwala, S. R.0000-0002-1098-7174
Additional Information:© 2009 American Institute of Physics. Published online 16 December 2009. This work is supported in part by the National Science Foundation (Grant Nos. AST-9978911, PHY-0542066, PHY-0503729, PHY-0503629, PHY-0503641, PHY-0504224, PHY-0705052, PHY-0801536, PHY-0801708, PHY-0801712 and PHY-0802575), by the Department of Energy (Contracts DE-AC03-76SF00098, DE-FG02-91ER40688, DE-FG02-92ER40701, DEFG03-90ER40569, and DE-FG03-91ER40618), by the Swiss National Foundation (SNF Grant No. 20-118119), and by NSERC Canada (Grant SAPIN 341314-07).
Funding AgencyGrant Number
Department of Energy (DOE)DE-AC03-76SF00098
Department of Energy (DOE)DE-FG02-91ER40688
Department of Energy (DOE)DE-FG02-92ER40701
Department of Energy (DOE)DE-FG03-90ER40569
Department of Energy (DOE)DE-FG03-91ER40618
Swiss National Science Foundation (SNSF)20-118119
Natural Sciences and Engineering Research Council (Canada) (NSERC)SAPIN 341314-07
Subject Keywords:CDMS, SuperCDMS, Dark Matter, Charge Collection
Series Name:AIP Conference Proceedings
Issue or Number:1185
Classification Code:PACS: 95.35.+d, 14.80.Ly, 73.61.Jc, 74.78.-w, 85.25.Oj, 85.25.-j
Record Number:CaltechAUTHORS:20160511-143815913
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:67007
Deposited By: Ruth Sustaita
Deposited On:12 May 2016 00:04
Last Modified:10 Dec 2019 00:11

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