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

A novel Compton Scanner setup has been built, commissioned and operated at the Max-Planck-Institute for Physics in Munich to study pulse shapes from bulk events in high-purity germanium detectors. 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. This allows for the creation of position-dependent pulse shape libraries. 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. Selected pulses are compared to simulated pulses to demonstrate the power of such pulse shape libraries to better understand the charge carrier drift in germanium.Comment: 13 pages, 15 figure