Application of positron agehyphen;momentum correlation measurement to the study of defects in electron irradiated synthetic silica glass

摘要

Agehyphen;momentum measurements and positron lifetime measurements were carried out in order to investigate vacancyhyphen;type defects produced in 3 MeV electron irradiated synthetic silica glasses, in which 1 ppm and 300 ppm of ndash;OH bonds were contained. A high formation probability of positronium (Ps) was found for unirradiated specimens. These Ps atoms were considered to be formed in openhyphen;volume defects (sim;7times;10minus;2nm3). The formation probability of Ps was drastically decreased by the electron irradiation, especially for the specimens which contained 1 ppm of ndash;OH bonds, even though the size of the openhyphen;volume defects and the momentum distribution of electrons at the openhyphen;volume defects are independent on the ndash;OH concentration and on the electron irradiation. Since the values of second lifetime components of positron lifetime spectra were sim;300 ps and very close to the estimated value of the lifetime of the positrons which are considered to be trapped in the monohyphen; or divacancies, the decrease of formation probability of Ps can be attributed to an increase of positron annihilation in vacancyhyphen;type defects generated by the electron irradiation. Positrons were suspected to be trapped in such defects. thinsp;