Calibration of a superconducting transformer by measuring critical current of a NbTi Rutherford cable

Large high field superconducting magnets often require high current superconducting cables. To develop these cables, a facility capable of providing a high magnetic field with large sampling area as well as electrical current of tens of kA is essential. A superconducting transformer (SCT) is an energy-efficient and low-cost way to provide large current to superconducting cables. Previously, we co-developed an SCT and successfully tested it to a maximum output current of 45 kA in zero magnetic field. In this work, this SCT is installed to the 12 T split solenoid magnet at the National High Magnetic Field Laboratory (NHMFL). We calibrated it by using this facility to measure the critical current of an NbTi Rutherford cable as a function of magnetic field up to 10 T, and compared the results with those available in the literature. In addition, a strand extracted from the NbTi cable was tested for critical current. The critical current of the extracted strand is scaled and compared with the critical current of the cable. The accuracy of the critical current measurement using this SCT is discussed in detail. This work concludes the commissioning of this SCT, which combined with the 12 T split magnet will provide a unique cable testing capability for future cable development for the NHMFL and its users.

Automated summary

This study introduces a superconducting transformer (SCT) installed on a 12 T split solenoid magnet for testing the critical current of NbTi Rutherford cable. The accuracy of critical current measurement using SCT is discussed through calibration and comparison of results. The commissioning of SCT combined with the 12 T split magnet provides a unique cable testing capability for future cable development for the NHMFL and its users.