Electron Gun and Output Coupling System for a 220-/251.5-GHz, 2-MW Triangular Corrugated Coaxial Cavity Gyrotron

In this paper, design studies of a common electron gun and output coupling system for the dual regime operation of a 2-MW coaxial cavity gyrotron are presented. The operating frequencies (220/251.5 GHz) are selected, such that the proposed gyrotron can be used for plasma heating applications in the future experimental fusion reactors. A coaxial magnetron injection gun (MIG) is designed for the generation of hollow electron beam with the desired parameters. Initial geometry of the electron gun is determined through our in-house code Gyrotron Design Suite version 4.1 2016 (GDSv4.1 2016). The MIG is further optimized and simulated through the beam trajectory code ESRAY. A nonlinear taper (NLT) is designed with maximum transmission efficiency at both the operating frequencies. A quasi-optical launcher (QOL) is designed and numerically optimized through the commercial software, launcher optimization tool. The designed launcher efficiently converts both the operating modes into Gaussian-like mode. A single-disk RF window is designed for the extraction of high-power output beam from the gyrotron at their respective operating frequencies. The design of the NLT and the RF window are carried out through GDSv4.1 2016.