This proposal is a continued exploration of the non-recoverable changes that have been reported in the structure of vitreous SiO2 when compressed. This proposed experiment will explore the pressure range 10 to 20 GPa and data will be collected at 14, 17 and 20 GPa to augment data already obtained at 11 and 22 GPa. We have demonstrated that amorphous diffraction data can be obtained on PEARL and have developed techniques to both reduce background contributions to the total scattered signal and to evaluate the pressure-dependent contribution to the background for double and single-torroid pressure devices such that quantitative diffraction data can be obtained in principle up to pressures of 25 GPa. In this proposal 8 days are requested to obtain data for three pressure points, for three in situ measurements of background and two additional background measurements.