Method for producing multilayered silica glass body

A method for producing a multilayer-structure silica glass body, in which a transparent silica glass layer is provided on a surface of a siliceous substrate comprising a siliceous material, the method comprising:

• preparing the siliceous substrate;
• preparing a silica slurry in which silica particles are dispersed in a liquid;
• applying the silica slurry to the surface of the siliceous substrate;
• smoothing the silica slurry coated on the surface of the siliceous substrate by applying vibration to the siliceous substrate;
• drying the smoothed silica slurry;
• and
• vitrifying the dried silica slurry by means of heating to form the transparent silica glass layer;
• wherein the silica slurry contains silica large particles comprising a siliceous material and having a particle size of between 200 μm and 700 μm, and silica medium particles comprising a siliceous material and having a particle size of 30 μm or more, and less than 200 μm;
• the total mass of the silica large particles and the silica medium particles contained in the silica slurry is 80% or more of the mass of all particles comprising a siliceous material contained in the silica slurry;
• and
• the silica large particle mass/silica medium particle mass, which is a ratio of the mass of the silica large particles and the mass of the silica medium particles, is set at between 0.25 and 7.0.