Porous glass preform production apparatus

A method of producing a porous glass preform using a porous glass preform production apparatus with a reaction vessel including 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, the method comprising:

• supplying raw materials for glass, a combustible gas, and a combustion supporting gas to burners disposed in the apparatus;
• and
• depositing glass microparticles generated by a flame hydrolysis reaction of the glass raw materials to produce a porous glass preform such that, during deposition, the floor of the upper deposition chamber is disposed at a height between a lower end of a straight body part and a deposition tip of the porous glass preform and a regular airflow passes through the connection opening from the lower deposition chamber to the upper deposition chamber, wherein
• 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,
• the second wall includes a substantially vertical wall segment above the exhaust outlet and facing the first air supply inlet, and
• the wall segment extends from the upper end of the exhaust outlet to a ceiling of the upper deposition chamber.