Enhancement of dispenser cathode fabrication with pre – design activation simulations and polymer doping

Abstract

This study includes dispenser cathode activation design including therefore cathode's peripheral parts and fabricating two different types of cathodes with some improvements. Activation which is a must for all of the dispenser cathodes is modeled for both M-type and scandate cathodes. The simulation results are verified with experimental data. This modeling study helps improve the thermal tests of cathodes. Besides the modeling studies, both cathodes are fabricated and tested. Polymer material and polymer-tungsten composition research is carried out also. The effects of polymer doping on the cathode matrix material on the surface roughness are investigated. Metal–polymer composition and its debinding process before sintering are also studied and new recipes are created. At the end of the study, it was examined that scandate cathodes operates at lower temperatures and their production has more controllable fabrication parameters. They can be used instead of M–type cathodes for the same current level at lower temperatures. Before the fabrication of the cathode, the components of the cathode are determined and designed with modeling, then polymer doping can be used to reduce surface roughness if pure tungsten is used. If there is an oxide compound in it, the polymer may not be needed. Scandate cathodes can be safely used for even its "as-sintered" form to operate at lower temperatures. Besides, the modeling study is also verified by commonly used cathodes and newly developed cathode types as well. It can be also used for any of the impregnated dispenser cathode types confidently.