Ionization Produced by Energetic Germanium Atoms within a Germanium Lattice

Abstract

The energy dependence of the ionization produced in germanium by energetic germanium atoms was measured. Germanium solid-state detectors served simultaneously as crystalline Ge sample, neutron target, and ionization detector. The spectrum of ionization produced by prompt Ge recoil atoms energized by monoenergetic neutron bombardment was observed in a pulse-height analyzer, and the edge of the spectrum was identified with the ionization produced by Ge recoil atoms having the calculated maximum recoil energy. The electron-hole pair production of Ge recoils was measured in this manner from 21.4 to 997 keV, using monoenergetic neutrons from 400 keV to 18.6 MeV. In this energy range, the ratio of the ionization produced by a Ge recoil relative to that of an electron of the same energy increased from ~0.15 to ^0.7. At very low Ge recoil energies, most of the energy goes into atomic processes. At high recoil energies, where electronic processes become important, the ionization produced by a Ge recoil appears to approach that for an electron of the same energy. The corresponding partition of energy between electronic processes and atomic processes for an energetic Ge atom in a Ge lattice agrees favorably with predictions of the theory of Lindhard et al. These data together with the earlier results of ionization produced by energetic Si atoms within a Si lattice agree with the A and Z dependence of the partition of energy predicted by Lindhard.

Measurement of the response of heat-and-ionization germanium detectors to nuclear recoils

“…The elastic collisions of neutrons with atoms in the detector volume produce nuclear recoils. The energy of the recoils is constrained by the use of monoenergetic neutron beams, the detection of the neutron scattering angle and/or its time-of-flight [5,6,7,8,9,10]. It is then observed that the ionization yield for a nuclear recoil is a factor Q ∼ 0.25 smaller than that produced by an electron recoil of equal energy.…”

A survey of energy loss calculations for heavy ions between 1 and 100kev

“…To reduce the theoretical difficulties, the attention is focused on pure substances: hence only symmetric projectile/target atom combinations will be investigated. From all the avail-able measurements, known to the authors, the following are then selected: Si [3,4], Ge [5,6], and liquid Xe [7,8,9,10]. Liquid Ar will also be considered on account of its interest for dark matter searches.…”

A model of nuclear recoil scintillation efficiency in noble liquids

“…Thus, the dominant uncertainties come from the uncertainties in the Lindhard theory at very low energy. However, it is usually believed that the Lindhard the- ory describes experimental data well [41,42,43,44], although the experimental uncertainties are quite large at low energy.…”