Experimental Measurements on Small-Scale HTS Racetrack Coils at INFN for Future Particle Accelerators

Abstract

REBCO tapes stand out as the most promising conductors for a large variety of applications, despite the lack of a complete understanding on both the theoretical and experimental sides. For this purpose, within the PNRR-IRIS project currently at its final phase, a 10 T, all-HTS, cryogen-free dipole magnet demonstrator has been designed and is being manufactured, namely ESMA (Energy Saving Magnet for sustainable Accelerators). To keep up with the development of ESMA, as well as to further increase the technological readiness level of REBCO, aiming at future particle accelerators, an experimental campaign is being carried out. This campaign focuses on validating the conductor stack behaviour and performance using both 4 mm and 12 mm Faraday Factory Japan (FFJ) REBCO tape through small sample measurements and small coil winding and testing in LN2. For this aim, a racetrack coil design has been engineered with an eye on repeatability for the first two windings which have been fabricated and tested in LN2. The tests include charging and discharging the coil at different rates, transition measurements to the Normal Conducting (NC) state, and overcurrent powering. Measurement results have been collected using multiple distributed sensors such as voltage taps and Hall probes. The expected margins and central field of the windings have then been calculated and compared with experimental data. These results, along with the design and manufacturing details of the racetrack coil, will be described and discussed throughout the article.