The Majorana Experiment will use arrays of enriched HPGe detectors to search
for the neutrinoless double-beta decay of 76Ge. Such a decay, if found, would
show lepton-number violation and confirm the Majorana nature of the neutrino.
Searches for such rare events are hindered by obscuring backgrounds which must
be understood and mitigated as much as possible. A potentially important
background contribution to this and other double-beta decay experiments could
come from decays of alpha-emitting isotopes in the 232Th and 238U decay chains
on or near the surfaces of the detectors. An alpha particle emitted external to
an HPGe crystal can lose energy before entering the active region of the
detector, either in some external-bulk material or within the dead region of
the crystal. The measured energy of the event will only correspond to a partial
amount of the total kinetic energy of the alpha and might obscure the signal
from neutrinoless double-beta decay. A test stand was built and measurements
were performed to quantitatively assess this background. We present results
from these measurements and compare them to simulations using Geant4. These
results are then used to measure the alpha backgrounds in an underground
detector in situ. We also make estimates of surface contamination tolerances
for double-beta decay experiments using solid-state detectors.Comment: 10 pages, 11 figures, submitted to NIM
