Effects of Magnetic Fields on HPGe Tracking Detectors

TL;DR

This study investigates how magnetic fields influence the position resolution and energy response of hyper-pure germanium detectors, revealing that fields above 0.1 T can impair resolution and above 1 T can affect energy accuracy.

Contribution

It provides a detailed analysis of charge carrier drift trajectories under combined electric and magnetic fields, offering realistic estimates of magnetic field impacts on detector performance.

Findings

Magnetic fields > 0.1 T affect position resolution.

Fields > 1 T degrade energy response.

Transverse position deviations are the major effect.

Abstract

We present a study of magnetic fields effects on the position resolution and energy response of hyper-pure germanium detectors. Our results provide realistic estimates of the potential impact on the resolving power of tracking-arrays from (fringe) magnetic fields present when operating together with large spectrometers. By solving the equations of motion for the electron and holes in the presence of both electric and magnetic fields, we analyzed the drift trajectories of the charge carriers to determine the deviations in the positions at the end point of the trajectories, as well as changes in drift lengths affecting the energy resolution and peak shift due to trapping. Our results show that the major effect is in the deviation of the transverse (to the electric field direction) position and suggest that, if no corrective action is taken in the pulse-shape and tracking data analysis procedures, a field strength $\gtrsim$ 0.1 T will start to impact the intrinsic position resolution of 2 mm (RMS). At fields above $\sim$1 T, the degradation of the energy response becomes observable.