Effective Low Magnetic Field Jc(B) Scaling of ITER Nb3Sn Strands by Magnetization and Critical Current Measurements

For the International Thermonuclear Experimental Reactor magnets, a significant fraction of the Nb
₃
Sn conductors will be operating at a low field (
B
< 4 T), such as the outer turns of the central solenoid modules and toroidal field winding packs, while so far, the
I_c
(
B,T, Ɛ
) parameterization has been derived from measurements carried out at higher fields (
B
≥ 7 T). It may not be accurate enough to adopt this parameterization for the extrapolation of the conductors’ operating performance in terms of critical current (
I_c
) and current sharing (
T_cs
). The critical current characteristic can be effectively extended to the lower field region by means of a relation between the magnetization and critical current. The parameterization of the derived critical current scaling law
J_c
(
B
) is processed for the field range of the magnetization measurement (0 <
B
≤ 9 T) and the critical current measurements (7 ≤
B
< 12 T) in order to cover the full range up to 12 T.