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Fakultät für Physik - Digitale Hochschulschriften der LMU - Teil 05/05 Podcast
Alpha-event characterization for germanium detectors

Alpha-event characterization for germanium detectors

Fakultät für Physik - Digitale Hochschulschriften der LMU - Teil 05/05 vor 10 Jahren

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A detailed study of alpha interactions on the passivated surface of
a germanium detector is presented. Germanium detectors can be used
to search for both neutrinoless double beta decay of 76Ge and
direct interaction of dark matter. In order to increase the
sensitivity to both neutrinoless double beta decay and dark matter
beyond the current state of the art, the next generation of
germanium-based experiments has to have a mass of about one ton and
has to reduce the background by a factor of ten. The choices of
detector technology facilitating both searches and the background
reduction are one of the biggest challenges for such an experiment.
Surface contaminations on the material close to the detectors or on
the detectors themselves, can generate a background due to alpha
particles, which was found to be limiting in some experiments. The
characterization of events induced by alpha particles will help to
identify such events and thus eliminate them as sources of
background. An especially designed segmented true-coaxial detector
was probed with alpha particles from an 241Am source inside the
test-stand GALATEA, located at the MPI f¨ur Physik in Munich. Pulse
shape analysis was performed to identify the characteristics of
alpha events. The properties of the detector directly underneath
the passivation layer on the end-plate were also studied. As part
of the detector characterization, the thickness of the effective
dead layer was determined. The studies presented here suggest
improvements on detector design, which would allow an effective
reduction of alpha background in next generation of germanium-based
experiments.