Background coming from the 42Ar decay chain is considered to be one of
the most relevant for the GERDA experiment, which aims to search of the
neutrinoless double beta decay of 76Ge. The sensitivity strongly relies on
the absence of background around the Q-value of the decay. Background coming
from 42K, a progeny of 42Ar, can contribute to that background via
electrons from the continuous spectrum with an endpoint of 3.5 MeV. Research
and development on the suppression methods targeting this source of background
were performed at the low-background test facility LArGe. It was demonstrated
that by reducing 42K ion collection on the surfaces of the broad energy
germanium detectors in combination with pulse shape discrimination techniques
and an argon scintillation veto, it is possible to suppress the 42K
background by three orders of magnitude. This is sufficient for Phase II of the
GERDA experiment