Speaker
Description
In this paper we will update the progress of the two types of advanced Nb3Sn conductors manufactured in Hyper Tech. One is ternary APC (Artificial Pinning Center) Nb3Sn strand by using internal oxidation technique to increase Jc in high field and lower the magnetization in low field; The other one is high specific heat (Cp) Nb3Sn strand to increase the energy margin against quenching by adding certain high Cp material in the strands. We are working on making kilometer length of both types of wires. The ternary APC Nb3Sn conductors with Ta and either Zr or Hf doping demonstrated substantial grain refinement and significantly increased Jc,nonCu, while retaining the high Bc2 values of the best ternary Nb3Sn conductors. These APC conductors reached the FCC Jc specification for both 61-stack and 217-stack wires. Compared with standard Nb3Sn, APC conductors have higher Birr and Bc2, and their Fp,max shifts to higher field. These two effects lead to flatter Jc-B curves, which enhances Jc at high fields (e.g., >10 T) but reduces Jc at low fields (e.g., < 5 T). This reduces magnetization at low fields, which is very desirable for suppressing low-field flux jumps, field errors, and a.c. loss. We successfully made kilometer length of high specific heat Nb3Sn conductors and demonstrated the Cp of the Wire is 10 times of the control wire at 1.9 K, and 4 times at 4.2 K, which will increase energy margin of the conductor.
