Performance test of a position sensitive planar germanium detector for phase-III DESPEC experiments

Abstract

The position sensitivity of a planar segmented double-sided germanium strip detector, with 10 × 10 electrical segmentation in orthogonal directions, has been studied using the coincidence method. The coincidences were set up between an imaging scanner and the PSPGe (Position Sensitive Planar Germanium) detector using a positron source, 22Na, and analyzed by employing the Positron Annihilation Correlation principle. A collimated 241Am source scan was also performed to find position resolution along X and Y axes using low energy gamma-ray source. The primary objective of this work is to study the charge carrier transportation for gamma-ray interactions inside the PSPGe detector. In order to select the electrodes of interest and to obtain the pulse shapes for each event, two-dimensional images have been processed. The net charge induced on the surface of the electrode, calculated using the pulse shape analysis procedure, has been used to profile the position resolution and gamma interaction depth. The present study is an input for the deployment of PSPGe detector in the future decay spectroscopy experiments to be performed at the Facility for Antiproton and Ion Research (FAIR) in Germany. This work investigates the gamma interaction depth by calculating the rise-time of traces stored for each gamma interaction inside the detector volume, providing ≈1 mm resolution along the depth. The position resolution of the detector in lateral directions, determined using the amplitude difference of the transient charges, has also been found to be ≈1 mm.