SAPPHIRE-METAL JOINING FOR LOW-LOSS GYROTRON WINDOWS

A NEW TECHNIQUE, PULSED ELECTRON BEAM (PEB) JOINING, WILL BE APPLIED TO THE PROBLEM OF JOINING, LOW-LOSS CERAMIC MATERIALS USED FOR WINDOWS IN HIGH FREQUENCY MICROWAVE DEVICES TO THE METAL VACUUM ENVELOPE OF THE MICROWAVE DEVICE. THE PEB TECHNIQUE ALLOWS SELECTIVE HEATING OF THE SPECIMEN TO BE JOINED THROUGH PREFERENTIAL ENERGY DEPOSITION THAT IS CONTROLLED BY A COMBINATION OF THE ELECTRON BEAM PARAMETERS AND THE PROPERTIES OF THE SPECIMEN. TEST SPECIMENS TO BE JOINED IN PHASE I WILL CONSIST OF SAPPHIRE PLATES AND THIN COPPER SHEETS. THE MICROSTRUCTURE OF THE TEST SPECIMENS WILL BE EXAMINED USING SCANNING ELECTRON MICROSCOPY, AND COMPARISONS WILL BE MADE WITH EXPECTATIONS BASES UPON MONTE CARLO COMPUTER SIMULATIONS OF THE PEB ENERGY DEPOSITION PROFILE. THE MECHANICAL STRENGTH OF THE TEST SPECIMENS WILL THEN BE EVALUATED USING MICROINDENTATION TECHNIQUES. BASED UPON THESE DATA, JOINING PARAMENTERS WILL BE IDENTIFIED FOR PHASE II TEST SPECIMENS THAT WILL ALLOW DETERMINATION OF THE PROPERTIES OF PEB-PRODUCED JOINTS UNDER CONDITIONS THAT SIMULATE WINDOW DESIGNS FOR GYROTRON OSCILLATORS.