High thermal efficiency dispenser-cathode and method of manufacture therefor

摘要

A reservoir dispenser cathode structure having improved thermal efficiency is provided by inner and outer subassemblies. The inner subassembly has a molybdenum heater cup to which a tungsten-rhenium alloy cap is laser seam-welded. The outer subassembly has a tantalum support cylinder within which the inner subassembly is supported by means of a three-point suspension in the form of tabs that are lanced from the tantalum cylinder and spot-welded to the heater cup. The heater has a coiled-coil design wherein the coils are coated with Al3O3 and small particle tungsten powder to increase the coil's thermal emissivity. This thermally-efficient structure permits the achievement of high current density (greater than 3 Amperes per square centimeter) with heater power that is less than 1.3 Watts.