Improving the resistivity variation in multi-layer heaters for use in dispenser cathodes

Dispenser cathodes must operate at specific temperature while a specific heater power is applied. To achieve the required temperature, a coiled wire heater is commonly used. 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. The technology for a printed heater exists, but, so far, has been unable to meet the production resistivity requirements. This paper presents initial research using ink- jetted tungsten particles on a ceramic substrate as an alternate approach to the heater design.