To allow the long-time and continuous measurement of the temperature of melt having high temperature in quick response and with high accuracy by applying the constitution that a guide tube built into a gap formed in a nozzle is made of a ceramic inner tube for leading a metallic tube sheathed optical fiber, and a metallic outer tube for fixing the inner tube to an inner wall.
A nozzle 20 installed on a furnace wall for leading a metallic tube sheathed optical fiber 11 has a guide tube 21 led inside, and the optical fiber 11 is slidably fed to a furnace via the inside of the guide tube 21. In addition, nitrogen gas is fed to space between the guide tube 21 and an outer tube 51, and blown into the furnace from the end of the nozzle 20. In this case, the nozzle 20 is made of a magnesia carbon brick and a stainless steel tube 41 buried in the internal side thereof. Also, the guide tube 21 is made of the metallic outer tube 51 and a ceramic inner tube 52. For the inner tube 52, short pipes of alumina are used and an alumina adhesive is applied to the external surface of the short pipes. Also, a coating material is applied to the edges of the short pipes. Then, the short pipes are sequentially inserted and arranged in the outer tube 51 and secured with the adhesive.
KOMATANI MASANORI
IZAWA TOMOO
MIYATA YASUTO
