Formation of Microcracks on the Surface of a Glass Irradiated with 30-Kev Protons
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ion of Microcracks on the Surface of a Glass Irradiated with 30-Kev Protons R. H. Khasanshina, b, *, L. S. Novikovc, and D. A. Primenkob aJSC
Kompozit, Korolev, 141070 Russia Moscow State Technical University, Moscow, 105005 Russia c Moscow State University, Skobeltsyn Institute of Nuclear Physics, Moscow, 119991 Russia *e-mail: [email protected] bBauman
Received December 2, 2019; revised January 22, 2020; accepted January 25, 2020
Abstract—Changes in the surface structure of K-208 glass irradiation with 20- and 30-keV protons in a vacuum chamber with a residual pressure of 10–4 Pa are studied using atomic-force microscopy. It is found that on the surface of K-208 glass irradiated with 30-keV protons at a flux density of ϕp = 4.5 × 1010 cm–2 s–1 and fluences Φp = (1.1 × 1015–6.6 × 1015) cm–2, microcracks are formed, the size of which grows with increasing fluence. We believe that the formation of microcracks is due to: the appearance of tensile stresses in the surface layer as a result of restructuring of the glass microstructure caused by the migration of sodium ions in the field of the introduced charge; the formation of gas-filled bubbles; mass transfer to the irradiated surface; and, possibly, access to the irradiated surface of percolation channels of sodium and oxygen. For those values of ϕp and Φp, irradiation of K-208 glass with 20-keV protons is shown to not lead to the formation of microcracks. Keywords: proton irradiation, K-208 glass, compression of glass, atomic-force microscopy, microcrack, surface structure, ion field migration, gas-filled bubbles DOI: 10.1134/S1027451020050110
INTRODUCTION At present, silicate glasses are frequently used under conditions of increased radiation loads caused by the effect of flows of charged particles. For example, there are glasses used in spacecraft and affected by unshielded cosmic radiation [1–3]. Such glasses are used in different detectors, lenses and prisms, as well as protective coatings of elements of solar cells and heat sinks. To give the required properties to silicate glass, alkali metal oxides are introduced in its composition. For example, the addition of sodium oxide (Na2O) decreases the melting temperature, accelerates the vitrification process, and promotes glass clarification. Potassium oxide (K2O) is introduced to decrease the crystallization ability of glass, improve its transparency and brightening. The irradiation of glass can change its composition [4–6], the morphology of the irradiated surface [7–10], density [11–13] and microstructure, lead to the formation of gas-filled bubbles [13–16], the regeneration of radiation color centers, the accumulation of injected charges [17, 18], and it can be accompanied by other, often related, processes. The formation of molecular oxygen observed in borosilicate glasses irradiated with both electrons [13– 16] and ions of He [19], Ar [20], Kr [21] and Xe [22]
can be explained by the migration of alkali metal ions (Li+, Na+, and K+) in the injected-charge field. Their field migration has a key role in restruc
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