High-rate and high-energy gamma-ray spectroscopy using charge trapping and ballistic deficit correction circuits

A study of the resolution of large, coaxial, reverse electrode, HPGe detectors was performed over the energy range from 100 keV to 10 MeV and triangular amplifier shaping times from 0.5 μs to 6 μs. Resolutions were calculated using an approach based on the Trammell-Walter equation. The effect of ballistic deficit was included in the calculations by the introduction of a term, the ballistic efficiency, to the Trammell-Water equation. Experimental data were collected over an energy range from 122 keV to 2.6 MeV on three detectors with relative efficiencies of 76%, 56%, and 29%. For these three detectors, the data indicated that the triangular shaping amplifier with charge trapping and ballistic deficit correction offered better resolution than a gated integrator for shaping times ⩾2 μs, while the gated integrator produced better resolution for shaping times ⩽1 μs. The data also show the added importance of charge trapping correction at high energies. For example, the detector with a relative efficiency of 29% had an uncorrected resolution of 1.98 keV with a 6-μs shaping time and at an energy of 1.33 MeV. However, at 10 MeV, the uncorrected resolution was predicted to be 7.3 keV, while an extrapolation of the data predicts a corrected resolution of 5.6 keV