Neutron Interactions as Seen by A Segmented Germanium Detector

TL;DR

This paper investigates neutron interactions in a segmented germanium detector used in GERDA, analyzing neutron-induced backgrounds and comparing experimental data with Geant4 simulations to improve background understanding for neutrinoless double beta decay searches.

Contribution

It provides detailed experimental data on neutron interactions in germanium detectors and evaluates the accuracy of Geant4 simulations, highlighting areas needing physics process improvements.

Findings

Neutron interactions produce identifiable peaks in the energy spectra.

Geant4 simulations accurately model many photon peaks but miss some physics processes.

Segment information helps distinguish neutron-induced signals.

Abstract

The GERmanium Detector Array, GERDA, is designed for the search for ``neutrinoless double beta decay'' (0-nu-2-beta) with germanium detectors enriched in Ge76. An 18-fold segmented prototype detector for GERDA Phase II was exposed to an AmBe neutron source to improve the understanding of neutron induced backgrounds. Neutron interactions with the germanium isotopes themselves and in the surrounding materials were studied. Segment information is used to identify neutron induced peaks in the recorded energy spectra. The Geant4 based simulation package MaGe is used to simulate the experiment. Though many photon peaks from germanium isotopes excited by neutrons are correctly described by Geant4, some physics processes were identified as being incorrectly treated or even missing.