Track Reconstruction and Performance of DRIFT Directional Dark Matter Detectors using Alpha Particles

TL;DR

This study analyzes alpha particle tracks in DRIFT dark matter detectors to characterize detector performance and understand alpha decay progeny charge states, advancing directional dark matter detection technology.

Contribution

It provides the first detailed analysis of alpha particle tracks in DRIFT detectors, measuring drift velocities and identifying uncharged progeny fractions, aiding detector optimization.

Findings

Measured drift velocities of 59.3 m/s and 57 m/s in DRIFT-IIa and IIb.

Identified uncharged fractions of 22% for Po-218 and 100% for Po-216 progeny.

Reconstructed 3D alpha tracks and energy spectra for decay analysis.

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)] m/s based on an analysis of naturally-occurring alpha-emitting background. The drift velocity in DRIFT-IIb was [57 +/- 1 (stat) +/- 3 (sys)] m/s determined by the analysis of alpha particle tracks from a Po-210 source. 3D range reconstruction and energy 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) are produced with no net charge in 40 Torr CS2. For Po-216 progeny (from Rn-220 decay) the uncharged fraction is (100 +0 -35)%.