| 摘要 |
PURPOSE:To obtain a high-purity quartz glass tube contg, little OH groups, little transition metals and no residual bubble by forming a quartz glass base material composed of a central portion of porous glass state and a peripheral portion of transparent glass state removing the porous central portion. CONSTITUTION:Oxhydrogen gas supplied to synthetic torch 21 forms flame 22, and in flame 22 glass fine particles of SiO2 or the like are synthesized from glass starting material such as SiCl4. The particles are sprayed upon the top of seed rod 23 and deposited to form a porous glass body. In synchronism with growth of the body rod 23 is pulled up while rotating with rotating and pulling unit 24, forming porous base material 25, which is then contracted with ringlike heating element 27. By adjusting transparently vitrifying conditions a peripheral portion along of the contracted material is transparently vitrified. The resulting quartz glass base material is treated with a hydrogen fluoride soln. to remove a portion of porous glass state. |
