JOINING ALUMINA TO SAPPHIRE FOR COPPER VAPOR LASER TUBES

THE PROPOSED PHASE I RESEARCH HAS SEVERAL ELEMENTS. THREE APPROACHES TO JOINING SAPPHIRE TO ALUMINA WILL BE EXPLORED: 1) SOLID-STATE OR DIRECT JOINING, 2) USE OF A METALLIC (NB OR PT OR THEIR ALLOYS) INTERLAYER, AND 3) JOINING WITH A DEVITRIFIABLE GLASS. BOND STRENGTH, VACUUM TIGHTNESS, THERMOCHEMICAL COMPATIBILITY (OF THE BOND) WITH COPPER, AND RESISTANCE TO FAILURE DURING THERMAL CYCLING UP TO 1500 DEG C WILL BE EVALUATED AND WILL INDICATE THE RELATIVE STRENGTHS AND WEAKNESSES OF THE THREE APPROACHES. THIS INFORMATION, IN CONJUNCTION WITH AN ASSESSMENT OF THE RELATIVE EASE OF APPLYING THESE TECHNIQUES TO (LARGER-SCALE) COPPER VAPOR LASER SYSTEMS, WILL BE USED TO DETERMINE AND PRIORITIZE THE RESEARCH APPROACHES TO BE USED DURING PHASE II. PHASE II WORK WOULD FOCUS ON FABRICATION AND EVALUATION OF SEALED TUBES. SINCE LONG-TERM CONTAINMENT OF COPPER VAPOR AND SUSTAINED LASER OPERATION ARE THE GOALS OF SEALED-TUBE TECHNOLOGY, PHASE II RESEARCH WOULD ALSO ADDRESS THE CRITICAL ISSUES OF LONG-TERM MICROSTRUCTURAL, THERMOMECHANICAL AND THERMOCHEMICAL STABILITY.