The low-temperature solubility of helium in quartz

The solubility of helium in $\alpha$- and $\beta$-quartz single crystals, optical quartz crystals, and Pyrex glass has been studied by the method of thermal desorption of helium from crystals preliminarily saturated in the gaseous phase in the temperature range $T$ = 323–1123 K and saturated vapor pressure $P$ = 0.6–31 MPa. It has been shown that the behavior of the solubility of helium in quartz crystals is described by exponential dependences on the reciprocal temperature. The solubility of helium in quartz single crystals is almost independent of temperature. For all kinds of samples, the solubility varies in proportion to the saturated vapor pressure and attains values of (6.2 $\pm$ 0.3) $\times$ 10$^{15}$ cm$^{-3}$ in single crystals for $P$ = 25.5 MPa, $T$ = 873 K, and (8.64 $\pm$ 0.04) $\times$ 10$^{19}$ cm$^{-3}$ in optical quartz for $P$ = 31 MPa and $T$ = 373 K. It has been shown that the solubility of helium in quartz single crystals can increase upon an increase in the concentration of defects in the crystal as a result of multiple thermal cycling of samples in the course of measurements. Possible mechanisms of the dissolution of helium in quartz have been studied, and the results have been compared with those obtained by other authors.