Ion bombardment damage in α-quartz at 50–295 K

Backscattering/channeling measurements have been used to analyse the damage produced in single crystals of α-quartz bombarded with 15–120 keV Ne+, Ar+, Kr+, Sb+ and Bi+ ions at 50 and 295 K. Damage production rates of up to 20 times those predicted by linear cascade theory have been observed. The damage versus dose (φ) behaviour is determined and related to the average cascade energy density, θν, and average fractional damage, FD, occurring within the individual cascade. It appears that, when FD ≲ 2%, the damage buildup with dose exhibits three distinct regions of different behaviour: (1) at low values of φ the damage increases linearly with φ; (2) at intermediate values of φ, it appears that the damage is ∝ φ2; (3) at the highest values of φ, the damage level attains a saturation value. For FD ≳ 7%, the intermediate region (∝ φ2) does not appear. We have also measured the damage production rate due to the 2 MeV He+ ions used in the backscattering/channeling measurements. The damage production cross-sections are found to be approximately two orders of magnitude greater than the values calculated by assuming elastic scattering to be the only mechanism responsible for such damage production. Preliminary indications suggest that the MeV He+ ion damage results primarily from the inelastic energy deposition whereas the keV heavy ion damage results from elastic collision events.