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Abstract

The CONUS experiment operates four p-type High Purity Germanium (HPGe) detectors
with a total mass of 4 kg to measure Coherent Elastic neutrino Nucleus Scattering (CE_NS)
in the fully coherent regime. It is located in close vicinity (17 m) to the reactor core
of the nuclear power plant in Brokdorf, Germany. Next to a high neutrino flux and
a sub-keV detector energy threshold, a low background is crucial to measure CE_NS
with a high sensitivity. A new Data AcQuisition (DAQ) system for the ongoing RUN-5
allows the recording of the pulse shapes for the individual events. The Pulse Shape
Discrimination (PSD) method, optimized and further developed in this work, aims to
discriminate background events that originate from the outer, semi-active volume of the
HPGe diodes. It is based on a rise time ( ) study of each single event. Accounting for the
electronic response of the DAQ and preamplifier and by modeling the influence of the noise,
trustworthy physical pulses from a function generator are used to calibrate the PSD-cut in
the Region Of Interest (ROI) for CENS (sub-keV range). Based on a plausible definition
of figures of merit the signal efficiencies are optimized to achieve the best sensitivity for
CENS when applying the PSD-cut. With efficiencies between 94 and 97 %, an average
background reduction in all four detectors of about 15 % is achieved within the ROI.