Fabrication of ceramic structures for MM-wave traveling wave tubes

We present the results of our investigations of fabrication technologies for ceramic photonic band gap (PBG) structures for mm-wave traveling-wave tubes (TWTs). There is a need for a high-bandwidth, high output power TWT operating at relatively low electron-beam voltages (20 keV). The key advance needed for this technology is the development of a novel high-frequency TWT structure. We proposed to put together a TWT with a sheet electron beam in an elliptical wide-bandwidth dielectric RF structure. PBG structures can be designed to be mode-selective and enable the required wide bandwidth and output power for the TWT. We conducted a feasibility study on fabrication of dielectric PBG structures in a high-epsilon ceramic material, designed suitable RF structure, drilled holes in high-dielectric ceramic blanks, measured them and studied the effect of hole's size variations and misalignments on the RF mode.