Efficiency loss in HPGe detectors due to beta and gamma sum coincidence

Abstract

Among the secondary detection effects in gamma-ray spectroscopy with HPGe detectors that reduce the peak area and must be properly taken into account in accurate measurements, the less well known is counting loss by beta and gamma-ray sum coincidence. The fraction of lost counts was estimated assuming that a photon detection event can sum either with the coincident beta-ray or its bremsstrahlung in the detector capsule or surrounding materials. The beta-ray was tracked through all the materials between source and detector. The result was calculated as a sequence of integral expressions evaluated numerically, without resorting to simulation. It is shown that the counting losses due to this effect are negligible for most calibration sources in typical detector arrangements.

41K(n,γ)42K thermal and resonance integral cross section measurements

“…1524.6(3) 18.08(9) 312.60 (25) 0.336(20) 899.7 (4) 0.052(3) 1920.8 (10) 0.041(4) 1021.2 (9) 0.0201 (14) 2424.3 (7) 0.020(3) 692.0 (8) 0.0033 (7) 1228.0 (15) 0.0024 (11) Although most of these transitions can be seen in the gamma-ray spectra, as will be discussed in Sect. 2.5, only the transition with energy 1524.6 keV was used to measure the 42 K residual activity.…”

“…2.5, only the transition with energy 1524.6 keV was used to measure the 42 K residual activity. It is worth noticing that the electrons from the β − transition to 42 Ca ground-state can pile-up with gamma-rays due to its large intensity combined with the high end-point energy, causing many unwanted events in the gamma-ray detector [9]. The absorber used to reduce pile-up events, as detailed in Sect.…”

Efficiency stability of HPGe detectors under distinct count rates

“…It is known from practical experience that the gain of an HPGe detector can oscillate slowly and slightly over short periods, usually less than 0.1% if the system is in good shapein practical terms, this means that in a given spectrum, a gamma-ray peak may be found at energies up to 1 keV away from the expected value. On the other hand, while there are a few studies on their long-term efficiency stability [6][7][8][9], and a lot of studies on the quantification of secondary detection effects [10,11], there are very few experimental data on the short-term stability of the HPGe detectors' efficiency or in the dependence of this stability with the count rate.…”