LAUSR

In this paper, the design studies of an output system [comprising a nonlinear taper, a quasi-optical launcher (QOL), and an RF window] for 220-/247.5-/275-GHz, triple-frequency gyrotron are presented. The precisely chosen mode-triplet is TE39,14/TE43,16/TE47,18 to support adequate power transfer at their corresponding frequencies of operation. The nonlinear uptaper is optimized using our in-house code Gyrotron Design Suite version 4.0 (GDSv4.0 2016) [7] in order to reduce the mode conversion for all the frequencies. A common dimpled wall QOL is designed and simulated using commercially available launcher optimization tool. A chemical vapor-deposited-diamond RF window is recommended with a decent transmission bandwidth for all the operating frequencies. The knowledge of correct phase of the Gaussian-like beam coming out of the RF window of any high-power gyrotron is most important for scheming a correct matching optic unit. Hence, the theoretical phase of the beams at a window plane is retrieved using an iterative phase retrieval algorithm.