First results of stress effects on I/sub c/ of Nb/sub 3/Al cable in conduit fusion superconductors

Abstract

The effect of axial strain, F,, on the critical current, I,, of Nb3Al "Cable in Conduit" (CIC) subconductors has been measured firstly at I, 5 10 kA and a magnetic field of B = 12 T a t KfK, Karlsruhe. Like comparable NbaSn CTC cables this conductor exhibits a maximum of I, at e, = 0.7 YO, but the degradation of I, at e, = 0 and B = 12 T being only 20% for Nb3Al in comparison to 50 96 for the NbsSn cables. Furthermore, the I, vs Ea characteristic behaves completely reversible under both loaded and unloaded conditions up to the measured strain of e, = 1.7%. The Nb3A1 CIC subconductor has been developed within the 10 k N 1 2 T class for fusion magnets a t JEARI. A tripleted cable consisting of 36 strands was inserted into a circular stainless steel conduit with 30 c?c void fraction and then heat treated. JR processed Nb:{Al wires were used for the basic strands.

Dependence of critical current density on temperature and magnetic field in multifilamentary Nb/sub 3/Al strands made by the Jelly roll process

“…The strand was fabricated with a copper stabilized multifilamentary structure like Nb3Sn and NbTi strands using a jelly-roll process. The Nb3Al strand has been reported to achieve a critical current density over 700 A/mm at 12 T 141 and to be less sensitive to strain and stress than Nb3Sn strand in critical current density [5,6]. Like this, Nb3Al strand is available for application to ITER coil.…”

Fabrication of <inline-formula> <tex-math notation="TeX">$\hbox{Nb}_{3}\hbox{Al}$</tex-math></inline-formula> Superconducting Wires by the Mechanical Alloying Method

“…Compared with the Nb 3 Sn superconductor, as the low-temperature superconductor equally, Nb 3 Al is more suitable for high-field application because of its high critical field (H c2 ), 29.5 T at 4.2 K [2]. Moreover, what is more, the strain tolerance of Nb 3 Al is higher than that of the NbTi alloy, Nb 3 Sn and other A15 intermetallics, which have been commercialized [3]. However, according to the Nb-Al phase diagram, Nb(Al) ss and the other two intermetallics Nb 2 Al and NbAl 3 are so stable even the temperature rises above 1000 • C, and that it is difficult to obtain single Nb 3 Al phase by diffusion heat treatment.…”

Development of advanced Nb3Al superconductors for a fusion demo plant

“…A Nb 3 Al superconductor inherently has the outstanding features of a higher critical magnetic field [2] and an excellent strain tolerance in critical current performance [3], as can be seen in figure 1 [4], compared with the Nb 3 Sn superconductor. These features can provide the possibility of obtaining a fusion magnet that can be operated at around 16 T, higher than 13 T obtained by using Nb 3 Sn conductors in ITER [1].…”