| 摘要 |
PROBLEM TO BE SOLVED: To provide such a constitution as to avoid the fall and dispersion of the powder from fumed silica having a hyperfine porous structure due to vibration and the like and the constitution in which heat stress is hard to apply to a heating element as an upper heater. SOLUTION: There is such a constitution as to cover a reflection part 17 with a heat-insulating sheet 21 between the reflection part 17 of fumed silica and a heating element 18 in an upper heater 16 arranged on the top of a heating chamber 12. By this constitution, the fall and dispersion of the powder from the reflection part 17 are prevented, and the atmospheric temperature of the heating element 18 can be decreased. Moreover, the life of the heating element 18 can be extended.
|
