Diamond Windows for High Power Microwave Transmission

70540 Microwave sources used in fusion research require microwave extraction windows with high thermal conductivity, low microwave absorption, and low resistance to thermal cracking. Newly developed, man-made diamond windows have all three of these properties, but these windows are expensive and unreliable. This limits the natural progress of these important technologies to higher powers and prevents additional applications. This project will develop a new process for manufacturing diamond windows using microwave plasma. A new trade off among the thermal, mechanical, and microwave transmission properties will be achieved by tailoring the microstructure of the diamond films, leading to greater reliability at lower costs. In Phase I, a small number of diamond windows with novel micro-structural properties will be deposited, with deposition rate higher than currently possible. The microwave transmission performance of the windows will be compared with existing diamond windows. Commercial Applications and Other Benefits as described by the awardee: In addition to fusion research, the new diamond windows should benefit industries involved with large scale industrial microwave heating; CO2 laser metal cutting; and microwave sources such as gyrotrons and traveling wave tubes used by both the civilian and military sectors.