| 摘要 |
PURPOSE:To obtain the titled high-quality base material contg. no bubbles and water in good yield without deteriorating the work environment by supplying a feed gas into a furnace core tube provided with the discharge port of a specified structure at a rotating inlet position and thermally decomposing the gas. CONSTITUTION:A gas inlet 6 is provided at the farhtermost lower part from the rotating inlet part 9 of a furnace core tube 5 made of a heat and corrosion-resistant material, the upper lid 8 lapped to be fitted to the upper flange 7 is connected, the clearance between the opening of the upper lid 8 and a rotatable and vertically movable shaft 2 is regulated to <=1mm and the furnace core tube 5 is formed so that the atmosphere in the furnace core tube 5 and a gas flowing in from the upper part of the upper lid are discharged from the discharge port 11 of a small chamber 10 provided to the upper lid 8 through the rotating inlet part 9. The furnace core tube 5 is inserted into an electric furnace 3, gases such as He, Ar, Cl2, SiF4, etc., are introduced from the gas inlet 6, heating, dehydration, F addition and vitrification are carried out, glass fine particles are gown on a layer 1 while rotating the glass fine particle deposited layer 1 provided to the shaft 2 and the gas from the outside of the furnace core tube 5 is discharged along with the atmosphere in the tube 5 from the discharge port 11 while controlling the intrusion of the gas into the tube 5. |
