Second harmonic TE15,2 550 GHz gyrotron experiment at NRL

Summary form only given. Near-THz gyrotrons are of interest for applications such as re mote sensing, materials processing, and dynamic nuclear pola rization enhanced nuclear magnetic resonance applications1. At the Naval Research Laboratory, we are developing a second harmonic gyrotron designed to operate at 550 GHz.2 An interaction cavity based on the TE15,2 mode with an effective length of about 1 cm and a Q of 7400 has been designed and is in the process of being assembled within the gyrotron tube with the output coupler. To avoid complications arising from strict alignment requirements, a simple Vlasov-type output coupler with a single quasi- parabolic reflecting mirror has also been designed using newly derived design equations. The converter has been verified by numerical simulations to generate an output beam with approximately 97% fundamental Gaussian content, though approximately 25% of the gyrotron power is lost within the converter. Simulations show that this lost power is mostly due to diffraction and mode conversion at the launcher cut3. Design calculations and simulations for the cavity and output coupler will be presented in addition to preliminary experimental results.