| 摘要 |
PURPOSE:To prepare the titled parent material having uniform quality in the axial direction at high growing rate by growing a porous parent material by the VAD process while making temp. distribution of the surface at an end of the growth side uniform by heating the neighbourhood of the growth end of the porous parent material with a heater. CONSTITUTION:A quartz glass rod 12 is inserted into a reaction vessel 11 and starting material gas is blown from a flame burner 13 to a foot end to desposit sooty fine glass particles. Said glass rod 12 is pulled upward while being revolved. Sooty fine glass particles deposit to the glass rod in the axial direction, allowing continuous growth of the porous parent material 14 comprising the sooty fine glass particles. At this stage, the neighbourhood of the growth end of the porous parent material 14 is heated with a heater 15. Thus, the temp. distribution near the growth end of the porous parent material 14 is made uniform, and the temp. distribution near the growth end is controlled by the heater facilitating appropriate control of flame. Thus, the loss of the starting material gas is prevented and improvement of the yield for the starting material is achieved. The rate of growth can be also enhanced. Furthermore, since the temp. difference at the growth end is hardly influenced by the fluctuation of flame, a parent material having uniform quality in the axial direction is obtd. |
