Patent ID: 8245542

Claim:
A method for producing a cylinder of synthetic quartz glass, said method comprising the following method steps: (a) forming SiO 2 particles by flame hydrolysis or oxidation of a silicon-containing start compound and layerwise deposition of said SiO 2 particles on a rotating carrier so as to form a cylindrical SiO 2 soot body having an inner portion and at least one free cylinder jacket surface surrounding the inner portion; (b) thermally drying the porous soot body by holding said porous soot body within a range of a drying temperature in such a way that a predetermined mean concentration of hydroxyl groups and a radial profile of the hydroxyl group concentration with a maximum in the inner portion of the soot body are obtained; and (c) vitrifying the dried soot body so as to form the cylinder of synthetic quartz glass, wherein the dried SiO 2 soot body that is present after method step (b) is subjected to a homogenizing method prior to said vitrifying, the homogenizing method comprising the following steps: (I) heating the soot body to a consolidation temperature to form a sealing layer in an area of the at least one cylinder jacket surface, the sealing layer sealing the inner portion to the outside; (II) cooling the soot body from the consolidation temperature; and (III) annealing the soot body by heating it in a range of a homogenization temperature during a period of at least 5 h so that the radial profile of the hydroxyl group concentration flattens in the inner portion.