| Manufacturing options for shaping thermionic nano-composite tungsten cathodes developed by the UC Davis millimeter-wave research group into desired shapes with proper emission surface quality using conventional metal removal techniques are presented. These cathodes can produce high current density electron beams without sacrifice in life due to their uniform tungsten and scandium matrix that assists with consistent barium and oxygen resupply to the emission surface. Machining techniques that preserve this structure are presented in this thesis: high speed milling, nano CNC milling, low speed turning, and electric discharge machining. It was found that the best surface quality is obtained using high speed milling with a precision platform like Mori Seiki NN1000, but good quality surfaces can also be obtained by electric discharge machining, and low speed turning. Cathodes are machined after impregnation with emission materials reducing cathode manufacturing price and chances for contamination. |
