TE/sub 01/ windows for high power klystron applications

Wideband klystrons traditionally use pillbox windows to transmit rf power from the vacuum envelope of the tube to the output waveguide. At high power levels, however, complications arise due to high electric fields at the interface between the window ceramic and the wall of the circular waveguide. High electric fields on the surface of the ceramic also lead to problems with the multipactor. Varian has developed a circular TE/sub 01/ mode window that significantly reduces these problems. The theoretical electric field at the ceramic-wall interface is reduced to zero, and the surface fields can be reduced by a factor of 5 or more. Issues related to the use of TE/sub 01/ overmoded windows are discussed and results presented for a high power window developed at Varian.<>