Further developments in multi-layer heaters for use in dispenser cathodes

In order to operate at optimum emission current density, dispenser cathodes must achieve a specific temperature while a specific heater power is applied. A coiled wire heater is commonly used to generate this power. These heaters are typically manufactured from Tungsten-Rhenium wire which is wound into a non-inductive coil. As the heater geometry is constrained by the material properties and electrical isolation needs of the wire, the coiled wire heater is often an inefficient use of available space and results in increased cost for the cathode assembly. Printed ceramic heater technology exists, but, to date, has not been usable in dispenser cathodes due to the manufacturing tolerances. This paper discusses the present status of a project to use ink-jetted tungsten particles on a ceramic substrate as an alternate approach to the multi-layer heater design.