Structural Changes of the K-208 Glass Surface after Proton Irradiation of Different Intensity

Changes in the structure of the surface of K-208 glass irradiated in vacuum (10–4 Pa) by protons with energies of 30 keV have been studied. It has been established that the nature of the changes depends on the proton flux density (φр). At φр < 3.0 × 1010 cm–2 s–1, the changes are mainly associated with the emergence of percolation channels on the irradiated surface. Percolation channels during proton irradiation of glass are formed as a result of migration of Na+ ions in the field of the charge injected into the glass. As φр increases, the formation of gas-filled bubbles begins to play a significant role. The appearance of bubbles is due to the fact that the field migration of Na+ ions is accompanied by the release of nonbridge oxygen atoms, which provided electrical neutrality in the vicinity of the localization of these ions. At values of φ > 2 × 1011 cm–2 s–1, gas-filled bubbles and sodium microarrays form and grow in pairs. The authors believe that under these irradiation conditions the accelerated field migration of sodium ions through the percolation channel ensures intensive release of nonbridge oxygen atoms in its vicinity, followed by their migration and the formation of gas-filled bubbles.