Threshold for Radiation Effects in Silica

Data are given for the initial compaction (negative dilatation) of vitreous silica per incident bombarding ion for 40- and 140-keV H⁺, D⁺, He⁺, Ne⁺, Ar⁺, and 80-keV He⁺. The slope of the logarithm of these data plotted against the logarithm of the energy above a threshold value dissipated in nuclear scattering indicates that the threshold energy for the compaction process is very low; much below the typical displacement threshold energy {~}25 eV. In contrast, when Hines and Arndt's data for the disordering of quartz in ion bombardment are treated in a similar fashion, a threshold energy {~}25 eV is obtained.