MW Level 280 GHz 2nd Harmonic Coaxial Gyrotron Cavity with Variable Corrugation Depth

The demand for high-power gyrotrons at frequencies above 200 GHz is increasing. This is anticipated to provoke a growing interest in harmonic high-power gy-rotrons. Interacting with the second cyclotron harmonic facilitates a doubling of the output frequency in gyro-devices using the same magnet system. Since the coupling of the electron beam with TE modes becomes inherently weaker, with increasing harmonic number, a suitable method must be found to suppress fundamental modes. The use of impedance corrugated inserts in coaxial gyrotron cavities has been presented in this regard. In order to increase the output power while main taining the ohmic wall loading on the inner conductor at continuous wave compatible levels, we have devised a technique that enhances the efficiency of suppressing fundamental modes by employing a tapered corruga-
tion depth on the inner conductor. This approach also increases the range of stable operation of the gyrotron and reduces the susceptibility of the operation to electron beam quality.