The DRIFT-IId dark matter detector is a m3-scale low-pressure TPC with directional sensitivity to WIMP-induced nuclear recoils. Its primary backgrounds were due to alpha decays from contamination on the central cathode. Efforts to reduce these backgrounds led to replacing the 20 \mu m wire central cathode with one constructed from 0.9 \mu m aluminized mylar, which is almost totally transparent to alpha particles. Detailed modeling of the nature and origin of the remaining backgrounds led to an in-situ, ppt-sensitive assay of alpha decay backgrounds from the central cathode. This led to further improvements in the thin-film cathode resulting in over 2 orders of magnitude reduction in backgrounds compared to the wire cathode. Finally, the addition of O2 to CS2 gas was found to produce multiple species of electronegative charge carriers, providing a method to determine the absolute position of nuclear recoils and reject all known remaining backgrounds while retaining a high efficiency for nuclear recoil detection.
@article{arxiv.1404.2253,
title = {Background Assay and Rejection in DRIFT},
author = {Jeff Brack and Ed Daw and Alexei Dorofeev and Anthony Ezeribe and Jean-Luc Gauvreau and Michael Gold and John Harton and Randy Lafler and Robert Lauer and Eric R. Lee and Dinesh Loomba and John Matthews and Eric H. Miller and Alissa Monte and Alex Murphy and Sean Paling and Nguyen Phan and Steve Sadler and Andrew Scarff and Daniel Snowden-Ifft and Neil Spooner and Sam Telfer and Daniel Walker and Matt Williams and Leonid Yuriev},
journal= {arXiv preprint arXiv:1404.2253},
year = {2015}
}
Comments
7 pages, 14 figures. To appear in the Proceedings of the TAUP 2013 Conference (F. Avignone & W. Haxton, editors, Physics Procedia, Elsevier)