DIAMOND COATINGS AND WINDOWS FOR MILLIMETER MICROWAVE TUBES

THE UNIQUE PROPERTIES OF DIAMOND MAKE IT ATTRACTIVE AS A MATERIAL FOR USE IN HIGH FREQUENCY, HIGH POWER, MILLIMETER MICROWAVE TUBES AND TRANSMISSION LINES. RECENT ADVANCES IN GYROTRONS AND FREE ELECTRON LASERS (FELS) AS POWER SOURCES, AND EXCELLENT PHYSICS RESULTS FROM THE T-10 TOKAMAK IN THE U.S.S.R. AND BIG-D AT GA TECHNOLOGIES IN THE U.S., HAVE HAD A MAJOR IMPACT ON THE FUSION PROGRAM. AN EXPERIMENT TO USE AN FEL TO HEAT A HIGH DENSITY TOKAMAK, MTX, IS UNDER WAY AT LAWRENCE LIVERMORE NATIONAL LABORATORY (LLNL). THE NEXT GENERATION OF FUSION MACHINES IS EXPECTED TO TAKE ADVANTAGE OF THESE TECHNOLOGIES FOR HEATING AND PROFILE CONTROL. IT IS VERY DESIRABLE FOR THESE RF SOURCES AND TRANSMISSION LINES TO HAVE SUITABLE WINDOWS FOR RELIABILITY AND FOR TRITIUM CONTROL. DEPOSITION OF DIAMOND FILMS BY PLASMA CHEMICAL VAPOR DEPOSITION (CVD) HAS RECENTLY BEEN DEMONSTRATED. PRACTICAL PRODUCTION OF DIAMOND WINDOWS CAN BE ADVANCED WITH IMPROVED TECHNIQUES FOR PLASMA CVD. NEW PLASMA SOURCES, USING THE HIGH PRESSURE MICROWAVE AND ELECTRON CYCLOTRON RESONANCE CONCEPTS, HAVE SIGNIFICANTLY ADVANCED THE TECHNOLOGY FOR DIAMOND DEPOSITION. THESE SOURCES PROVIDE LARGE AREA, UNIFORM PLASMAS THROUGH PROPRIETARY TECHNOLOGY. DIAMOND FILMS WILL BE DEPOSITED WITH A THICKNESS GREATER THAN 0.1 MMAND A DIAMETER GREATER THAN 2 INCHES. THESE FILMS WILL BE GROWN ON A SUBSTRATE SUCH AS NICKEL, SILICON, OR SAPPHIRE. THE FILM-SUBSTRATE COMBINATION OR THE FREE-STANDING FILM, SEPARATED BY DISSOLVING THE SUBSTRATE, WILL BE EVALUATED. THE REAL AND IMAGINARY COMPONENTS OF THEDIELECTRIC CONSTANT OF THE FILMS WILL BE MEASURED IN THE MILLIMETER RANGE, AND THE FRACTURE STRENGTH WILL BE MEASURED IN ORDER TO EVALUATE THE FEASIBILITY OF GROWING THICK DIAMOND FILMS FOR WINDOW AND INDEX APPLICATIONS.