A novel wide-angle Compton Scanner setup to study bulk events in germanium detectors

TL;DR

This paper introduces a new wide-angle Compton Scanner setup for studying bulk events in germanium detectors, enabling efficient pulse shape analysis and validation of simulation models.

Contribution

The paper presents a novel, fully automated Compton Scanner setup with wide-angle acceptance, detailed construction, alignment procedures, and initial pulse shape library creation for germanium detectors.

Findings

Successful construction and operation of the Compton Scanner.

Validation of spatial reconstruction with surface pulse comparison.

First comparison showing the scanner's effectiveness in testing simulation models.

Abstract

A novel Compton Scanner setup has been built, commissioned and operated at the Max-Planck-Institute for Physics in Munich to collect pulses from bulk events in high-purity germanium detectors for pulse shape studies. In this fully automated setup, the detector under test is irradiated from the top with 661.660 keV gammas, some of which Compton scatter inside the detector. The interaction points in the detector can be reconstructed when the scattered gammas are detected with a pixelated camera placed at the side of the detector. The wide range of accepted Compton angles results in shorter measurement times in comparison to similar setups where only perpendicularly scattered gammas are selected by slit collimators. In this paper, the construction of the Compton Scanner, its alignment and the procedure to reconstruct interaction points in the germanium detector are described in detail. The creation of a first pulse shape library for an n-type segmented point-contact germanium detector is described. The spatial reconstruction along the beam axis is validated by a comparison to measured surface pulses. A first comparison of Compton Scanner pulses to simulated pulses is presented to demonstrate the power of the Compton Scanner to test simulation inputs and models.