Cross Sections for Atomic Displacements in Solids by Gamma Rays

Abstract

Cross sections for the displacement of lattice atoms by gamma rays for energies up to 5 Mev have been calculated. The principal contribution is found to come from the Compton effect, in which the atoms are displaced by electrons produced by the incident gamma rays. The calculations have been based on the assumption of a sharp threshold energy for displacement, but cross sections have been computed as a function of the assumed threshold energy. Thus, from the present work it is relatively easy to obtain cross sections based upon other displacement functions.

Bulk damage effects in irradiated silicon detectors due to clustered divacancies

“…16 The scattered electrons from 60 Co photons typically have energies of only a few hundred keV on average, 17 which is insufficient to displace more than one or two silicon atoms 18 from their lattice positions. The generation of divacancy states is therefore limited and most defects are of the vacancy-impurity type distributed uniformly throughout the bulk silicon.…”

“…The leakage current damage constant α cl , (for the cluster contribution) can be expressed (16) where η cl is the cluster introduction rate and V cl represents the volume of the terminal clusters. The damage constant can then be expressed in terms of the V 2 introduction rate η V 2 , and the clustered V 2 density N t as…”

Anomalies in fracture experiments, and energy exchange between vibrations and nuclei

“…Compton scattering of the incident gammas would be effective in causing atomic displacements [78], which provides a source of high frequency THz acoustic vibrations; an interpretation of these experiments is that nuclear energy is going into the acoustic modes (in contrast to the two-laser experiment mentioned above) since the receive the majority of the external stimulation, which results in (coherent) disintegration of the host metal atoms through inverse fractionation. Implicit in this discussion is that elemental transmutations in the fracture experiments share the same underlying mechanism with these experiments.…”

Neutron-enhanced annealing of radiation damage formed by self-ion implantation in silicon

“…18 We roughly estimated atomic displacements by gamma rays based on the method using MckinleyFeshbach cross sections, 19 assuming a gamma-ray energy of 2 MeV. 18 A displacement rate by gamma rays at the irradiation facility was about 1 ϫ 10 −10 dpa/ s, while the displacement rate by neutrons was 3.2ϫ 10 −8 dpa/ s. Therefore, the displacements by gamma rays are negligible in this study.…”