Discrimination of nuclear and electronic recoil events using plasma effect in germanium detectors

Abstract

We report a new method of using the plasma time difference, which results from the plasma effect, between the nuclear and electronic recoil events in high-purity germanium detectors to distinguish these two types of events in the search for rare physics processes. The physics mechanism of the plasma effect is discussed in detail. A numerical model is developed to calculate the plasma time for nuclear and electronic recoils at various energies in germanium detectors. It can be shown that under certain conditions the plasma time difference is large enough to be observable. The experimental aspects in realizing such a discrimination in germanium detectors is discussed.

Bulk and surface event identification in p-type germanium detectors

“…Events produced by different particles (electrons, gammas, neutrons) exhibit similar bulk rise-time distributions in Ge detectors with the current generation of technology. Previous work indicated no difference of bulk risetime distributions for γ-sources and nuclear recoil [20], and recent work reported that electron and nuclear events may differ in their rise-time by about ∼10 ns due to plasma effects [21], much faster than the typical Ge detectors 80 rise-time of ∼1 µs. Differentiation of these signals are at the forefront of research, the success of which would represents a major advance in Ge-detector techniques and applications.…”