Background Assay and Rejection in DRIFT

Understand

The DRIFT-IId dark matter detector is a m$^3$-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.