Track reconstruction and performance of DRIFT directional dark matter detectors using alpha particles

S. Burgos, J. Forbes, C. Ghag, M. Gold, V. A. Kudryavtsev, T. B. Lawson, D. Loomba, P. Majewski, D. Muna, A. St J. Murphy, G. G. Nicklin, S. M. Paling, A. Petkov, S. J. S. Plank, M. Robinson, N. Sanghi, N. J. T. Smith, D. P. Snowden-Ifft, N. J. C. Spooner, T. J. SumnerJ. Turk, E. Tziaferi, Alex Murphy

Research output: Contribution to journalArticlepeer-review

Abstract

First results are presented from an analysis of data from the DRIFT-IIa and DRIFT-IIb directional dark matter detectors at Boulby Mine in which alpha particle tracks were reconstructed and used to characterise detector performance-an important step towards optimising directional technology. The drift velocity in DRIFT-IIa was 59.3 +/- 0.2 (stat)+/- 7.5 (sys) ms(-1) based on an analysis of naturally occurring alpha-emitting background. The drift velocity in DRIFT-IIb was 57 +/- 1 (stat)+/- 3 (sys) ms(-1) determined by the analysis of alpha particle tracks from a Po-210 source. Three-dimensional range reconstruction and range spectra were used to identify alpha particles from the decay of Rn-222, Po-218, Rn-220 and Po-216. This study found that (22 +/- 2)% of Po-218 progeny (from Rn-222 decay) did not plate out and remained suspended in the 40Torr CS2 gas fill until they decayed. A likely explanation for this is that some of the polonium progeny are produced in an uncharged state. For Po-216 progeny (from Rn-220 decay) the undeposited fraction was apparently much higher at (100(-35)(+0))% most likely due to a shorter lifetime, causing a larger fraction of the progeny to decay whilst drifting to the cathode plane. This explanation implies a much slower drift time for positively charged polonium progeny compared to CS2 ions.

Original languageEnglish
Pages (from-to)114-128
Number of pages15
JournalNuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Volume584
Issue number1
DOIs
Publication statusPublished - 1 Jan 2008

Keywords

  • dark matter
  • WIMPs
  • TPC
  • gas detector
  • directional detector
  • negative ion drift
  • alpha spectrometry

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