Development of a wide-band HE11 mode window for a W-band gyro-TWA

Microwave windows are a critical component in gyrotron-traveling wave amplifiers (gyro-TWAs). They are used to couple in or out microwave power whilst maintaining the vacuum inside the beamtube. Broadband windows are very difficult to manufacture, especially for microwave amplifiers which require a very low reflection. Presented in this paper is the design, simulation and measurement of a wide-band (90 to 100 GHz) multilayer microwave window using the HE11 mode as the input microwave mode. The simulated performance shows a better than −30 dB reflection over a 10% bandwidth of 90–100 GHz. The measured window is in very good agreement with the simulated results.