Production process of synthetic quartz glass

A production process of a highly heat-resistant synthetic quartz glass having an absorption coefficient at 245 nm of 0.05 cm−1 or more, comprising the steps in the sequence set forth:

• preparing a silica porous body,
• conducting a reduction treatment to the silica porous body in an atmosphere containing a reducing gas at a reaction temperature of 100° C. or higher and 1,300° C. or lower for 30 minutes or more,
• conducting a baking treatment to the silica porous body at a reaction temperature of 1,300° C. or higher and 1,900° C. or lower, thereby forming a dense glass body having an absorption coefficient at 245 nm of 0.05 cm−1 or more,
• wherein said reducing gas is a volatile silicon compound containing nitrogen and/or carbon, and said volatile silicon compound is at least one kind of compound selected from the group consisting of a silazane and an organosilazane, after the reduction treatment, a heating treatment is carried out in an atmosphere containing hydrogen, followed by subjecting to a baking treatment, thereby obtaining a dense glass body and
• wherein the dense glass body has a natural logarithmic value of viscosity at 1280° C. in an approximate range of 11.7 and 12.4.

A production process of a highly heat-resistant synthetic quartz glass having an absorption coefficient at 245 nm of 0.05 cm−1 or more comprising the steps in the sequence set forth:

• preparing a silica porous body,
• conducting a reduction treatment to the silica porous body in an atmosphere containing a reducing gas at a reaction temperature of 100° C. or higher and 1,300° C. or lower for 30 minutes or more,
• conducting a baking treatment to the silica porous body at a reaction temperature of 1,300° C. or higher and 1,900° C. or lower, thereby forming a dense glass body having an absorption coefficient at 245 nm of 0.05 cm−1 or more,
• wherein said reducing gas is a volatile silicon compound containing nitrogen and/or carbon,
• wherein the volatile silicon compound is hexamethyldisilazane and
• wherein the dense glass body has a natural logarithmic value of viscosity at 1280° C. in an approximate range of 11.7 and 12.4.

A production process of a highly heat-resistant synthetic quartz glass having an absorption coefficient at 245 nm of 0.05 cm−1 or more comprising the steps in the sequence set forth:

• preparing a silica porous body,
• conducting a reduction treatment to the silica porous body in an atmosphere containing a reducing gas at a reaction temperature of 100° C. or higher and 1,300° C. or lower,
• conducting a baking treatment to the silica porous body at a reaction temperature of 1,300° C. or higher and 1,900° C. or lower for 30 minutes or more, thereby forming a dense glass body having an absorption coefficient at 245 nm of 0.05 cm−1 or more,
• wherein said reducing gas is a volatile silicon compound containing nitrogen and/or carbon,
• wherein the volatile silicon compound is hexamethyldisiloxane and
• wherein the dense glass body has a natural logarithmic value of viscosity at 1280° C. in an approximate range of 11.7 and 12.4.