Off-center hot spots; double thermocouple determination of the thermal gradient in a 1.27 cm (1/2 in.) CaF ₂ piston-cylinder furnace assembly

Abstract

Double-thermocouple experiments were carried out at 10 kbar in a 1.27 cm (1/2 in.) piston-cylinder apparatus to map the thermal gradient and locate the peak temperature of a CaF 2 -graphite furnace assembly over the temperature interval 900-1500 C. An unexpected but reproducible result was that the thermal peak is displaced upward significantly (toward the steel base plug) from the vertical center of the graphite heater tubes.