SYNTHETIC QUARTZ GLASS WITH RADIAL DISTRIBUTION OF FAST AXES OF BIREFRINGENCE AND PROCESS FOR PRODUCING THE SAME

摘要

The present invention provides a synthetic quartz glass having a diameter of 100 mm or more for using in an optical apparatus comprising a light source emitting a light having a wavelength of 250 nm or less, the synthetic quartz glass having, in a region located inward from the periphery thereof by 10 mm or more in a plane perpendicular to the optical axis of the synthetic quartz glass: a birefringence of 0.5 nm or less per thickness of 1 cm with respect to a light having a wavelength of 193 nm; an OH group concentration of 60 ppm or less; an averaged differential OH group concentration from the center of the synthetic quartz glass toward a peripheral direction thereof, normalized with respect to the radius of the synthetic quartz glass, of not less than -60 ppm and less than -8 ppm; and an unbiased standard deviation s of a differential OH group concentration from the center of the synthetic quartz glass toward a peripheral direction thereof, normalized with respect to the radius of the synthetic quartz glass, of 10 ppm or less, the unbiased standard deviation s being determined with the following formula (1): (1) providing; (a): differential OH group concentration at measurement point i normalized with respect to the radius R of the synthetic quartz glass; (b): OH group concentration at measurement point i in terms of moving average for three points including the two points before and after the measurement point i; (c): radius at measurement point i normalized with respect to the radius R of the synthetic quartz glass; (d): average of OH group concentrations Xi in the whole evaluation region; and n: number of measurement points in the evaluation region (integer of 2 or more).