IMPROVED PROPERTIES IN NB 46.5 WEIGHT % TI MATERIALS FOR SSCBY REDUCING THE SEPARATION BETWEEN FILAMENTS

IN THE LAST SIX OR SEVEN YEARS, VERY SIGNIFICANT INCREASES HAVE BEEN ACHIEVED IN THE CRITICAL CURRENT DENSITIES (JCS) IN BOTH MONOFILAMENTARY AND MULTIFILAMENTARY NIOBIUM (NB)-46.5 WT.% TITANIUM (TI). SEVERAL QUESTIONS ARE FREQUENTLY RAISED THAT REMAIN UNANSWERED. THESE QUESTIONS INCLUDE THE FOLLOWING: (1) HOW CLOSE TO THE THEORETICAL JC PREDICTED BY PINNING THEORY CAN BE ACHIEVED IN PRACTICE IN MONOFILAMENTS AND IN MULTIFILAMENTARY MATERIALS, (2) WHAT ARE THE MOST IMPORTANT EXTRINSIC FACTORS LIMITING THE JC IN MULTIFILAMENTARY MATERIALS, AND (3) WHAT IS THE RELATIONSHIP BETWEEN PIECELENGTH, JC, AND FILAMENT SIZE? THIS PROJECT ATTEMPTS TO ANSWER THESE QUESTIONS AS THEY AFFECT MULTIFILAMENTARY NBTI MATERIALS SUCH AS THOSE USED INTHE SUPERCONDUCTING SUPER COLLIDER (SSC). IN PHASE I, THE EFFECT ON JC OF REDUCING THE SPACING-TO-DIAMETER RATIO BELOWTHAT NORMALLY USED IN THE STANDARD SSC MATERIAL IS ILLUSTRATED BY THE USE OF SMALL TRIAL BILLETS. THE EFFECTS ARE BEING OBSERVED AT DIFFERENT FILAMENT DIAMETERS TO ILLUSTRATE WHAT, IF ANY, PRICE IS PAID IN JC OF THE NBTI BY REQUIRING FINE FILAMENTS. IN PHASE II, SCALE-UP WILL BE CARRIED OUT AND EFFORTS MADE TO DETERMINE THE EFFECTS OF THEVARIOUS CONDITIONS ON PIECELENGTH AS WELL AS JC.