The radiation change in structure of silica glass

Full text: We studied of radiation change in the structure of neutron-irradiated silica glass by optical, dielectric and X-ray spectroscopic methods. It is established that at fluences from F=1·1019 till F=4·1019 cm-2 rapid changes of the dielectric permittivity, structure parameters takes place in glass. At higher fluences the dose dependencies of intensify saturate. Apparently, stress concentration near defects occurs and damages until the additional energy of the glass network reaches a critical value. Than in all probability, a rapid transitions of silica glass into a metamict state occurs. The value of the micro parameters - electrical polarizability calculated from the Lorentz-Lores formula for a fluences to 1021 cm-2 is shows, that at the initial stage of irradiation to 1019 cm-2 a plates this parameters change little. A noticeable reduction in it occurs for a fluency higher that 1019 cm-2, when a rapid transition takes place type silica glass-metamict state. The micro parameter decreases upon irradiation to 9·1019 cm-2 and then remains constant at the crystalline silica irradiated with the same fluency. The coincidence of this parameter for two amorphous states obtained on irradiation on silica - crystals and glass with the same dose suggests that the transition goes to completion at a fluency of about 9·1019 cm-2, when both modifications pass to metamict state. It is of particular interest to study the effect of high doses, which at fluency higher than 1020 cm-2 modify metamict state. It is found that the dose dependencies of the electronic polarizability exhibit breaks and that saturate. This suggests that some parameter of the radiation modified metamict state stabilize at high irradiation fluences. The results was calculated the secondary parameter - the total polarizability in the reactor irradiated silica glass shows to be nonmonotonic this function with an upturn around 4·1019 cm-2 . This is caused by a transition silica glass - metamict state. One should mark, that presence of critical point in the dose dependencies of this parameters coincides with that obtained by X-ray methods, has been found, when leap change of structural parameter of the first halo (this intensity) on the curves of the dose dependencies as intensity causes, probably, by transition into metamict state, was marked out. Analysis of the dose dependence for two type of polarizability reveals is not correlation between them, this is shaved difference of the radiation stabilize of atomic and electronic subsystem of silica glass