Three-dimensional position reconstruction of orthogonal-strip planar high-purity germanium detectors using maximum likelihood estimation

TL;DR

This paper introduces a maximum likelihood estimation method for 3D position reconstruction in orthogonal-strip planar high-purity germanium detectors, significantly improving accuracy and noise resilience over traditional techniques.

Contribution

It presents a novel joint reconstruction approach using maximum likelihood estimation with integral-based parameters to enhance 3D position accuracy in HPGe detectors.

Findings

Reduced maximum Z reconstruction bias from 0.4 mm to 0.02 mm in the central region.

Mitigated resolution degradation under high-noise conditions.

Achieved position resolution between 0.07 mm and 0.44 mm depending on the direction.

Abstract

Orthogonal-strip planar high-purity germanium (HPGe) detectors can reconstruct three-dimensional (3D) positions of photon interactions through analysis of parameters extracted from multiple charge signals. The conventional method independently reconstructs positions in each dimension using amplitude-based parameters, leading to noise sensitivity and systematic biases. In this study, we propose a multi-parameter-joint reconstruction method based on maximum likelihood estimation (MLE) which establishes a mapping between pulse shape parameters and corresponding 3D positions. To mitigate the effects of electronic noise, we employ integral-based parameters. The reconstruction performance was evaluated using pulse shape simulations. For 100 keV photons under 1 keV root-mean-square (RMS) electronic noise, the maximum Z reconstruction bias was reduced from 0.4 mm to 0.02 mm in the central region and from 2 mm to 0.15 mm near the electrodes. The maximum reconstruction bias in the X/Y directions was reduced from 0.4 mm to 0.016 mm. Furthermore, the use of integral-based parameters mitigated the rapid degradation of resolution under high-noise conditions. The achieved position resolution ranged from 0.07 mm to 0.16 mm in the Z directions and from 0.07 mm to 0.44 mm in the X/Y direction. This method offers a promising approach to 3D position reconstruction with HPGe detectors for applications such as medical imaging and gamma-ray astronomy.