Investigation of Nb3Sn superconducting wire for AC superconducting magnet

Research Project

Project/Area Number	60550190
Research Category	Grant-in-Aid for General Scientific Research (C)
Allocation Type	Single-year Grants
Research Field	電力工学
Research Institution	TOHOKU UNIVERSITY
Principal Investigator	ANAYAMA Takeshi Tohoku University Faculty of Engineering, 工学部, 教授 (20005177)
Co-Investigator(Kenkyū-buntansha)	SATO Michio Tohoku University Faculty of Engineering, 工学部, 助手 (30110654)
Project Period (FY)	1985 – 1986
Project Status	Completed (Fiscal Year 1986)
Budget Amount *help	¥2,100,000 (Direct Cost: ¥2,100,000) Fiscal Year 1986: ¥700,000 (Direct Cost: ¥700,000) Fiscal Year 1985: ¥1,400,000 (Direct Cost: ¥1,400,000)
Keywords	Twisted multifilamentary superconducting wire / Unsymmetrical AC magnetic field / AC loss / Copper matrix loss / Single layer coil
Research Abstract	Non-inductive coils consisted of 2,4 and 6 layers were made of both a twisted, multifilamentary, superconducting wire with a copper core and a twisted, multifilamentary, superconducting wire with uniformly distributed filaments. By transporting AC currnts to these coils, AC losses of twisted, multifilamentary, superconducting wires in unsymmetrical AC magnetic fields were measured. When amplitude of higher AC magnetic field ( <H_h> ) in unsymmetrical AC magnetic field is under lower critical field, it can be found that quantities of copper matrix losses are determined by the square of averaged value of AC magnetic fields( <H_h> , <H_1> ) on both out sides of superconducting wire. When amplitude of AC magunetic field( <H_h> ) is both 44200A/m and 61900A/m, it can be found that quantities of AC losses in lower friquency region become small remarkably with the increase of largeness of unsymmetry of unsymmetrical AC magnetic field in a twisted, multifilamentary, superconducting wire with a copper core. Four single layer coils which have different ratios of coil length(L) to coil diameter(D) were made of a twisted, multifilamentary superconducting wire with a copper core. (L/D) of four coils are 2.85,1.99,1.30,0.794. AC losses of four coils generated by transporting AC currents were measured. When n・I is 10600A/m (n is coil turns per unit length and I is amplitude of AC current), it can be found that AC losses(q) per unit length for four coils have same friquency dependencies, and quantities of AC losses(q) become smaller as (L/D) is smaller, and ratio of quantities of AC losses(q) is 1:0.93:0.82:0.67. It can be found that ratios of quantities of AC losses(q) for four coils are almost same with the limit of our experiments in which maximum n・I is 61900A/m and maximum friquency is 17Hz.