Charge trapping correction and energy performance of the MAJORANA DEMONSTRATOR

P-type point contact (PPC) high-purity germanium detectors are an important technology in astroparticle and nuclear physics due to their superb energy resolution, low noise, and pulse shape discrimination capabilities. Analysis of data from the MAJORANA DEMONSTRATOR, a neutrinoless double-beta decay experiment deploying PPC detectors enriched in 76Ge, has led to several novel improvements in the analysis of PPC signals. In this work we discuss charge trapping in PPC detectors and its effect on energy resolution. Small dislocations or impurities in the crystal lattice result in trapping of charge carriers from an ionization event of interest, attenuating the signal, and degrading the measured energy. We present a modified digital pole-zero correction to the signal energy estimation that counters the effects of charge trapping and improves the energy resolution of the MAJORANA DEMONSTRATOR by approximately 30% to around 2.4 keV full width at half-maximum at 2039 keV, the 76Ge Q value. An alternative approach achieving similar resolution enhancement is also presented.

Automated summary

P-type point contact (PPC) high-purity germanium detectors are important in astroparticle and nuclear physics for their high performance. Analysis of data from the MAJORANA DEMONSTRATOR has led to improvements in the analysis of PPC signals, addressing the issue of charge trapping and improving energy resolution. A modified digital pole-zero correction is presented, resulting in a 30% enhancement in energy resolution, and an alternative approach achieving similar results is also discussed.