Critical current density in superconducting Nb-Ti under proximity effect

✍ Scribed by E.S. Otabe; T. Matsushita

• Publisher: Elsevier Science
• Year: 1993
• Tongue: English
• Weight: 937 KB
• Volume: 33
• Category: Article
• ISSN: 0011-2275
• DOI: 10.1016/0011-2275(93)90250-r

✦ Synopsis

It has been found that the critical current density Jc in a multifilamentary superconducting Nb-Ti wire first increases and then reaches a peak, while the critical temperature decreases monotonically as the superconducting filament diameter is decreased by drawing to the submicrometre range. This behaviour originates from a variation in the morphology of the normal cz-Ti phase precipitated during heat treatment, coupled with the proximity effect between the superconducting matrix and normal cx-Ti. In this paper the elementary pinning force fn of ~-Ti ribbons is theoretically estimated for idealized multilayers of superconducting and normal regions, and Jc is calculated from a statistical summation of the elementary pinning interactions. The theoretical result predicts that Jc increases monotonically with drawing, owing to the increase in density of pin points, in spite of the decrease in fp. The reason for the observed degradation of Jc is discussed.