Optimized digital filtering techniques for radiation detection with HPGe detectors

TL;DR

This paper presents advanced digital filtering techniques integrated into GEANA software for radiation detection with HPGe detectors, demonstrating improved energy resolution across a broad energy spectrum, including novel nonlinear ballistic deficit correction methods.

Contribution

Introduction of a nonlinear ballistic deficit correction combined with various shaping filters for enhanced radiation detection in HPGe detectors.

Findings

Achieved ~1.61 keV FWHM energy resolution at 1332.5 keV, surpassing manufacturer specifications.

Modified cusp filter without ballistic correction yields best low-energy resolution of 0.46 keV at 59.5 keV.

Ballistic deficit correction minimizes resolution loss across the energy range.

Abstract

This paper describes state-of-the-art digital filtering techniques that are part of GEANA, an automatic data analysis software used for the GERDA experiment. The discussed filters include a novel, nonlinear correction method for ballistic deficits, which is combined with one of three shaping filters: a pseudo-Gaussian, a modified trapezoidal, or a modified cusp filter. The performance of the filters is demonstrated with a 762 g Broad Energy Germanium (BEGe) detector, produced by Canberra, that measures {\gamma}-ray lines from radioactive sources in an energy range between 59.5 and 2614.5 keV. At 1332.5 keV, together with the ballistic deficit correction method, all filters produce a comparable energy resolution of ~1.61 keV FWHM. This value is superior to those measured by the manufacturer and those found in publications with detectors of a similar design and mass. At 59.5 keV, the modified cusp filter without a ballistic deficit correction produced the best result, with an energy resolution of 0.46 keV. It is observed that the loss in resolution by using a constant shaping time over the entire energy range is small when using the ballistic deficit correction method.