Thermal and Mechanical Analysis of High Power Microwave

High Power microwave vacuum windows are an essential component in developing 1 MW/CW gyrotrons. The thesis focuses on thermal and mechanical analysis of three different microwave window designs. These include the present double disk window, a distributed window being developed by General Atomics and a single-disk diamond window design. The output microwave window is currently the limiting factor in obtaining high power (1 MW) long pulse and cw operation. The present design has a maximum power handling capability of 450 kW. The double disk window consists of two thin 12.7 cm sapphire disks which are face cooled by a fluorocarbon, which exhibits low microwave absorption. A thorough study of the present window has been made in order to learn more about the loss tangent, its temperature dependence and the film coefficient. 1D Analytical solutions for transient and steady state response of the double disk window have been developed as well as conducting 2 and 3D finite element simulations. The theoretical temperature calculations have been compared with temperature measurements of a, sapphire double disk window that were conducted in conjunction with Varian Associates on a 500 kW gyrotron long pulse gyrotron and good agreement was found. 1 MW/CW power transminssion is achievable by utilizing two double disk windows in a dual output configuration with a lowered peaking factor, or by employing the General Atomics I)istributed or single disk diamond window. Thesis Supervisor: Doctor Richard J. Temkin Title: Senior Research Scientist, Physics Department Thesis Reader: Doctor Emanuel S. Bobrov Title: Lecturer, Mechanical Engineering Department