Influence of thermal treatments on the low temperature specific heat of Suprasil-W vitreous silica

We report specific heat results between 0.04 and 4 K in Suprasil-W vitreous silica submitted to thermal treatments at 1100 and 1300°C, on samples of different sizes. In the very low temperature range, i.e. below 0.5 K, the specific heat mainly due to the two-level systems is only slightly sensitive to the annealing. On the contrary, the large anomaly localized at 1–2 K is very sensitive to the conditions of the thermal treatments and to the shape of samples. Comparison is made with a similar anomaly induced in crystalline quartz by fast neutron irradiation at moderate doses.