On the Role of the Proton Component in the Evolution of the Morphology of K-208 Glass under Combined Electron–Proton Irradiation

Abstract

By the methods of atomic force microscopy (AFM) we investigate the surfaces of samples of K-208 glass after separate and combined irradiation in a vacuum chamber with a residual pressure of p_v = 10⁻⁴ Pa with protons and electrons with energies of 20 and 30 keV, respectively. At flux densities of protons φ_p and electrons φ_e from 10¹¹ to 5 × 10¹² cm^–2 s^–1, the fluences of the particles Φ_p and Φ_e vary in the range of 10¹⁴–5 × 10¹⁶ cm^–2. The obtained results allow us to state the following: the character of changes in the morphology of the samples under the action of protons and electron–proton plasma for φ_p <5 × 10¹² cm^–2 s^–1 at φ_e: φ_p < 3 coincides and is due to radiation-stimulated stresses, reorganization of the glass network and the formation of gas-filled bubbles; at φ_p ≥ 5 × 10¹² cm^–2 s^–1, the change in the morphology of the glass is determined by the mass transfer caused by local heating of the near-surface layer. In the case of proton irradiation, a model is proposed that describes the process of the field migration of sodium ions, which plays a key role in restructuring of the glass microstructure and the release of atoms of non-bridging oxygen.