Process for the preparation of synthetic quartz glass

A process for producing synthetic quartz glass, comprising:

• (1) evaporating a feedstock containing at least one organosilicon starting compound to form a feedstock vapor;
• (2) feeding the feedstock vapor from (1) to a reaction zone in which the feedstock vapor is burned in a flame from a burner in the presence of oxygen and, if necessary, in the presence of combustible auxiliary gases and is converted to SiO2 soot particles by oxidation or by hydrolysis;
• (3) depositing the SiO2 soot particles resulting from (2) on a deposition surface to form a soot body;
• if necessary, drying and vitrification of the SiO2 particles resulting from (3) to form synthetic fused silica;
• characterized in that in (3), the deposition surface for the SiO2 soot particles is located at a distance from the burner for a period of at least 50% of the build-up time of the soot body, which lies between a position just behind the maximum (viewed from the burner) of the horizontally integrated luminous intensity [in candela/(mm of flame height] of the same flame mentioned above under un disturbed conditions (i.e. with removed deposition surface) up to a position behind the maximum (viewed from the burner) at which the horizontally integrated luminous intensity of the flame is still at least 2/3 of the maximum, wherein the luminous intensity of the flame is measured in candela/(mm2 of flame area).