Test Results of a 100 kA NbTi CICC

Abstract

For the secondary winding of the flux pump (superconducting transformer) of the EDIPO test facility at CRPP Villigen, a NbTi cable-in-conduit conductor (CICC) was designed at CRPP and procured at the industry. From a left section of the CICC a SULTAN sample, nicknamed TRASEK, has been assembled and tested.In the conductor design, high Cu:non-Cu ratio in the strand (no copper segregation), low void fraction and SnAg5 coating of the strand surface are selected to allow smooth current redistribution and enhance the take-off voltage. The DC tests are carried out before and after solder filling the sample termination and current sharing is observed up to 80 kA. Eventually, the DC conductor performance is limited by the self field of the sample in the U-bend region.In normal operation, the secondary coil of the transformer is not exposed to significant magnetic field sweeps. The AC loss is expected to be large according to the design choices (tin coating, low void fraction). The AC loss characterization in SULTAN includes over 400 load cycles.The pressure drop vs. mass flow rate is measured in SULTAN to complement the data base for friction factor of CICC's.

Test Results of Three Poloidal Field Superconducting Samples in SULTAN

“…7 shows the take-off electric fields of conductors versus the NbTi current density; it is seen that a big Cu:non-Cu ratio enhances the take-off electric field at low superconducting current density only and does not bring a big advantage at high superconducting current density. Recently tested "TRASEK" and ITER Correction Coil conductors [6], [7] show an advantage of rectangular shape in enhancing of take-off electric field: the fraction of the cable space exposed to the peak field is much larger in rectangular conductor compared to the round ones, mitigating the self-field instabilities.…”