  Low-pressure gas Time Projection Chambers being developed for directional
dark matter searches offer a technology with strong particle identification
capability combined with the potential to produce a definitive detection of
Galactic Weakly Interacting Massive Particle (WIMP) dark matter. A source of
events able to mimic genuine WIMP-induced nuclear recoil tracks arises in such
experiments from the decay of radon gas inside the vacuum vessel. The recoils
that result from associated daughter nuclei are termed Radon Progeny Recoils
(RPRs). We present here experimental data from a long-term study using the
DRIFT-II directional dark matter experiment at the Boulby Underground
Laboratory of the RPRs, and other backgrounds that are revealed by relaxing the
normal cuts that are applied to WIMP search data. By detailed examination of
event classes in both spatial and time coordinates using 5.5 years of data, we
demonstrate the ability to determine the origin of 4 specific background
populations and describe development of new technology and mitigation
strategies to suppress them.
