INCREASED TIN CONTENT IN A DUCTILE MATRIX FOR NIOBIUM TIN CONDUCTORS

AVAILIBILITY OF SILICON RADIATION DETECTORS WITH LARGE SENSITIVE DEPTHS HAS BEEN SERIOUSLY RESTRICTED BY LACK OF A GOOD SUPPLY OF VERY HIGH RESISTIVITY, HIGH QUALITY, SINGLE CRYSTALS OF SILICON. THIS PROGRAM IS DIRECTED AT A COST-EFFECTIVE AND RELIABLE METHOD FOR MAKING SILICON FOR DETECTORS WITH SENSITIVE DEPTHS BEYOND SEVERAL MILLIMETERS. THE METHOD IS BASED ON AN INNOVATIVE CONCEPT FOR CIRCUMVENTING THE PROBLEMS CAUSED BY NONUNIFORM DISTRIBUTION OF IMPURITIES. NONUNIFORM IMPURITY DISTRIBUTION HAS FRUSTRATED MANY PREVIOUS ATTEMPTS TO MAKE STABLE, COMPENSATED, VERY HIGH RESISTIVITY SILICON IN A PREDICTABLE AND COST-EFFECTIVE MANNER. PHASE I WILL CONCENTRATE ON DEVELOPING TECHNIQUES FOR SPECIALIZED MATERIAL EVALUATIONS, ON THE PROCESS FOR RESTORING CHARGE CARRIER LIFETIME AND TRAPFREE MATERIAL, AND ON PROVING THE FEASIBILITY OF THE CONCEPT. A PHASE II EFFORT WILL BE REQUIRED TO PRODUCE ENOUGH MATERIAL TO VERIFY THE REPRODUCIBLE QUALITY OF THE DETECTOR GRADE CRYSTALS AND THE ABILITY TO MAKE THEM IN QUANTITY AT A REASONABLE COST. A PREDICTABLE COMMERCIALLY VIABLE SOURCE OF ULTRA HIGH RESISTIVITY SILICON HAS ELUDED MANY PREVIOUS INTERNATIONAL EFFORTS. A SOLUTION TO THIS PROBLEM WILL REMOVE MANY DETECTOR DESIGN AND MANUFACTURING LIMITATIONS. BRONZE-PROCESSED NB(3)SN (NIOBIUM TIN) SUPERCONDUCTORS HAVE BEEN EXPLORED FOR THE LAST 20 YEARS, YIELDING CONSIDERABLE AND VALUABLE PROCESSING PARAMETERS AND TECHNIQUES. MUCH OF THE INTEREST IN BRONZE PROCESSING IS ROOTED IN THE FACT THAT THESE MATERIALS CAN BE PROCESSED AT ELEVATED TEMPERATURES, WHILE MAINTAINING A SOLID STATE. INCREASES INCURRENT DENSITIES HAVE BEEN HAMPERED BY THE WASTED VOLUME CREATED BY THE NON-SUPERCONDUCTING MATRIX. THE OBJECTIVE OFTHIS PROGRAM IS TO INCREASE THE AMOUNT OF SN IN THE MATRIX WHILE MAINTAINING REASONABLE DUCTILITY IN THE CONDUCTOR. THIS CAN BE ACHIEVED BY USING ALLOYING MATERIALS THAT CAN CARRY A HIGHER QUANTITY OF SN. EXPERIMENTS WILL USE SEVERAL DIFFERENT LEVELS OF SN TO DETERMINE ADVANTAGES AND DISADVANTAGES CONCERNING DUCTILITY AND CURRENT DENSITIES IN THE FINAL CONDUCTOR. THE CONDUCTOR WILL CONTAIN AMOUNTS OF SN HIGHER THAN THE 13.5 WT% FOUND IN CONVENTIONAL DUCTILE BRONZE, WHILE MAINTAINING DUCTILITY AND THE ABILITY TO BE PROCESSED AT ELEVATED TEMPERATURES.