Radiation Effects of Bombardment of Quartz and Vitreous Silica by 7.5-kev to 59-kev Positive Ions

Abstract

Bombardment of quartz or vitreous silica by positive ions produces a surface layer of altered refractive index whose depth and refractive index is found from reflection coefficient measurements at 650 m\ensuremath{\mu}, 600 m\ensuremath{\mu}, 550 m\ensuremath{\mu}, 500 m\ensuremath{\mu}, and 450 m\ensuremath{\mu}. The layer depths and the changes in refractive index versus integrated flux are given for ${\mathrm{H}}_{2}^{+}$, ${\mathrm{D}}_{2}^{+}$, ${\mathrm{He}}^{+}$, ${\mathrm{Ne}}^{+}$, ${\mathrm{A}}^{+}$, ${\mathrm{Kr}}^{+}$, and ${\mathrm{Xe}}^{+}$ ions with energies from 7.5 kev to 59 kev. All bombardments give approximately equal changes in refractive index for a given energy input per unit volume of material as long as the ion energy is low enough so that energy loss by ionization is negligible. The changes produced by ion bombardment are attributed to direct lattice displacements and are shown to be consistent with the known changes produced in quartz and vitreous silica by fast neutron bombardment. Thermal spikes produced by knock-on atoms in quartz and vitreous silica are experimentally shown to be unimportant for knock-on energies near 45 kev.