Patent ID: 8656743

Claim:
A porous glass preform production apparatus for producing a porous preform, the apparatus comprising a reaction vessel which includes an upper deposition chamber having a first air supply inlet in a first wall and an exhaust outlet in a second wall opposing the first wall, a lower deposition chamber having a second air supply inlet and connected to the upper deposition chamber by a connection opening on a floor of the upper deposition chamber, and a top chamber disposed on top of the upper deposition chamber and adapted to lift and store a porous glass preform formed by deposition, wherein the second wall includes a substantially vertical wall segment above the exhaust outlet and facing the first air supply inlet, an angle of elevation θ from an upper end of the exhaust outlet to an upper end of the first air supply inlet satisfies the expression 5 degrees≦θ≦50 degrees, and the wall segment extends from the upper end of the exhaust outlet to a ceiling of the upper deposition chamber.