PURPOSE: To simplify the production process of a superconducting material introduced with an artificial pinning center by overlapping and laminating foils made of a superconducting substance and foils made of a nonsuperconducting substance in turn to form a spiral object, burying the spiral object in an ordinary conducting metal material, then applying shrinkage machining.
CONSTITUTION: Foils of Nb and NbTi are overlapped and closely wound and inserted into a Cu billet. The billet is vacuum-sealed with an electron beam, then it is compressed by the CIP(cold isostatic pressure) method. It is formed into a hexagonal strand by hot extrusion machining. 278 strands are packed into the Cu billet, and it is formed into a linear shape by hot extrusion machining and draw machining. The space factor of Nb is set to 60% or below and the laminating cycle of Nb and NbTi must be set to 5nm<λ<100nm to increase the critical current density Jc in an Nb/NbTi filament.
MATSUMOTO KANAME
TANAKA YASUZO
SHIGA SHOJI
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