Method and device for producing a blank mold from synthetic quartz glass by using a plasma-assisted deposition method

The invention relates to a method for producing a blank mold from synthetic quartz glass by using a plasma-assisted deposition method, according to which a hydrogen-free media flow containing a glass starting material and a carrier gas is fed to a multi-nozzle deposition burner. The glass starting material is introduced into a plasma zone by the deposition burner and is oxidized therein while forming SiO2 particles, and the SiO2 particles are deposited on a deposition surface while being directly vitrified. In order to increase the deposition efficiency, the invention provides that the deposition burner ( 1 ) focuses the media flow toward the plasma zone ( 4 ) by. A multi-nozzle plasma burner, which is suited for carrying out the method and which is provided with a media nozzle for feeding a media flow to the plasma zone, is characterized in that the media nozzle ( 7 ) is designed so that it is focussed toward the plasma zone ( 4 ). The focussing is effected by a tapering ( 6 ) of the media nozzle ( 7 ).