| 摘要 |
PROBLEM TO BE SOLVED: To easily observe an article to be treated and to heat in a clean environment by disposing a heat source around the article, and further providing a plurality of transparent members each having high light transmittance in a visible light ray region and a low light transmittance in a radiant heat ray region therearound. SOLUTION: An article 1 heated to a high temperature or a radiating heat ray radiated from a heat source 2 is shut OFF to 50% or more by a transparent member 3c, and further shut OFF 50% or more by transmitting through transparent members 3b, 3a. Gaps 6a, 6b are held in a pressure reduced state by a vacuum pump 8 to suppress a convection heat transfer, and hence a heat insulating effect is further improved. When a temperature in a furnace is 800 deg.C, a temperature of the gap 6a is 540 deg.C, a temperature of the gap 6b is 270 deg.C, and an outer wall temperature can be lowered to 190 deg.C. Since the members 3a, 3b, 3c have each a high transmittance in a visible light ray region, the article can be observed, and an influence to give to the article is reduced without contamination of an atmosphere in a furnace caused by an evaporation of its constituting component.
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