Bulk and surface charge collection: CDMS detector performance and design implications

C. N. Bailey, Z. Ahmed, D. S. Akerib, S. Arrenberg, D. Balakishiyeva, L. Baudis, D. A. Bauer, J. Beaty, R. l. Brink, T. Bmch, R. Bunker, B. Cabrera, D. O. Caldwell, K. Clark, J. Cooley, R. Cushman, F. DeJongh, M. R. Dragowsky, L. Duong, E. Figueroa-FelicianoJ. Filippini, M. Fritts, S. R. Golwala, D. R. Grant, J. Hall, R. Hennings-Yeomans, S. Hertel, A. Hojem, D. Homgren, L. Hsu, M. E. Huber, O. Kamaev, M. Kiveni, M. Kos, S. W. Leman, S. R. Mahapatra, V. Mandic, D. Moore, K. A. McCarthy, N. Mirabolfathi, H. Nelson, R. W. Ogburn, M. Pyle, X. Qiu, E. Ramberg, W. Rau, A. Reisetter, T. Saab, B. Sadoulet, J. Sander, R. W. Schnee, D. N. Seitz, B. Serfass, K. M. Sundqvist, A. Tomada, G. Wang, M. Whilden, S. Yellin, J. Yoo, B. A. Young

Research output: Chapter in Book/Report/Conference proceedingConference contribution

2 Scopus citations


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 languageEnglish (US)
Title of host publicationLow Temperature Detectors LTD-13 - Proceedings of the 13th International Workshop
Number of pages4
StatePublished - 2009
Event13th International Workshop on Low Temperature Detectors, LTD-13 - Stanford, CA, United States
Duration: Jul 20 2009Jul 24 2009

Publication series

NameAIP Conference Proceedings
ISSN (Print)0094-243X
ISSN (Electronic)1551-7616


Other13th International Workshop on Low Temperature Detectors, LTD-13
CountryUnited States
CityStanford, CA


  • CDMS
  • Charge Collection
  • Dark Matter
  • SuperCDMS

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