High reliability sheathed, beryllia insulated, tungsten-rhenium alloy thermocouple assemblies- their fabrication and EMF stability

1.6 mm diameter tantalum sheathed, BeO insulated, W-3% Re/W-25% Re thermocouple assemblies have been fabricated and their emf drift determined during 2059 hours of exposure at 2073 K in a gaseous helium environment. The sheathed thermocouple assemblies were constructed from aged thermoelements, specially heat-treated BeO insulators, and specially cleaned and etched tantalum sheaths.