Process of making a dense synthetic silica glass, a muffle furnace for performing the process, and silica glass obtained from said process

A process of making synthetic silica glass in a combustion chamber of a muffle furnace, said process comprising the steps of:

• a) producing a gas flow in the combustion chamber, said gas flow containing a fuel, a chemical oxidizing agent, and a gaseous silicon compound, which is converted by flame hydrolysis and/or by chemical oxidation to SiO2 particles;
• and
• b) depositing the SiO2 particles on a target surface of a target in the combustion chamber so as to form a roll-shaped silica glass body;
• wherein the combustion chamber is bounded by chamber walls and has a front end provided with a gas inlet and a rear end provided with a gas outlet, and said chamber walls and said outlets are arranged rotationally symmetric in relation to a longitudinal axis of the combustion chamber and said combustion chamber widens in a direction from the gas inlet to the gas outlet;
• wherein the gas flow is produced by at least three nozzles, said three nozzles comprising a central nozzle for supplying the silicon compound arranged at said front end of the combustion chamber, a first ring-shaped nozzle for supplying the oxidizing agent arranged concentric to and spaced from said central nozzle, and a second ring-shaped nozzle arranged concentric to the central nozzle, which has a diameter that is greater than a diameter of the first ring-shaped nozzle;
• wherein the first ring-shaped nozzle has a first ring gap and the second ring-shaped nozzle has a second ring gap and a ratio of an area of the second ring gap to an area of the first ring gap is from 1:4 to 1:6.1.