Verification of the 170/204 GHz Quasi-Optical Output Coupler of the 2 MW Coaxial-Cavity Gyrotron using a Mode Generator Setup

At KIT, a 2 MW single-frequency 170 GHz coaxial-cavity short-pulse pre-prototype gyrotron has been upgraded towards to dual-frequency operation at 170 GHz and 204 GHz. That upgrade includes a modification of the quasi-optical output coupler system. For validation of the proper design a verification of that sub-system at low power is vital. Therefore, an automated quasi-optical mode generator has been developed for the excitation of the high-order rotating TE34,19 cavity mode excited at 170 GHz and the TE 40,23 mode excited at 204 GHz. The TE 40,23 mode is the mode with the highest eigenvalue ever excited in cold tests with a high mode purity. The measurements results of the quasi-optical output coupler system shows an excellent agreement with the simulation.