DESIGN OF A 60 GHz, 100 kW CW GYROTRON FOR PLASMA DIAGNOSTICS

Abstract

Gyrotrons are high power microwave/millimeter wave sources capable of producing hundreds of kilowatts of long pulse to CW power. They are being used in a variety of Industrial—Scientific—Medical (ISM) applications ranging from plasma heating in thermonuclear fusion reactors to industrial heating of materials (particularly nano powders). It is basically an electron cyclotron maser (ECM) in which the electromag-netic energy is radiated by relativistic elecrons gyrating in an external longitudinal magnetic field. In this work, the design studies of a 60 GHz, 100 kW, CW gyrotron are presented. Mode selection is carefully studied with the aim of minimizing mode competition; few operating modes are chosen which are capable of giving a perfect solid beam output through a synthetic double—disc window with a suitable dimpled—wall quasi—optical launcher. Cavity design and interaction computations are then carried out. In addition, preliminary design of the launcher, window, magnetic guidance and beam optic system are presented. Thus, a comprehensive conceptual study is pre-sented which indicates that the operation of such a gyrotron is possible and can give power in excess of 100 kW at > 35% efficiency. A Graphical User Interface package "GDS V.01" (Gyrotron Design Suit Ver.01) has been developed in MATLAB R2006a on HP xw6400 Workstation having 3 GB RAM. The software incorporates the mode selection procedure, starting current calculations, gun synthesis and design of coils, resonator design and RF—behavior calculations, launcher design, non—linear taper design and window design. This package can be used to carry, out feasibility studies and conceptualization of specific gyrotrons. iii