108/140/171 GHz multi-mode multi-frequency gyrotron output window design

For multi-frequency operation, the output windows are required to have excellent transmission for all operating frequencies. The output windows for 108/140/171 GHz multi-mode multi-frequency gyratory have been designed with Boron Nitride as the material and the design parameters are given so that the output windows can efficiently transmit high power microwaves at 108 GHz, 140 GHz and 171 GHz. The reflection coefficients S11 are less than -20 dB in the frequency bands 106.71-108.57 GHz, 138.72-140.58 GHz, and 171.33-173.23 GHz.