Contribution to improvement of mechanical stability in superconducting coils using DFRP bobbins

A moving of the superconducting wire due to an electromagnetic force induces heat, and that is one factor of instabilities in superconducting coils. There is a wire motion under a DC operation; on the other hand, there is a mechanical loss under an AC operation. To prevent those movements, it is effective to enhance the winding tension at coil-operating temperature. For that purpose, we propose the use of a Dyneema fiber reinforced plastic (DFRP), which has a negative thermal expansion coefficient, as the bobbin of the superconducting coils. To investigate a contribution to improvement of stability due to the DFRP, we performed DC and AC experiments. In the DC experiment, rates of the attainment to the critical current were evaluated by quench training measurements, and in the AC experiment, losses were measured. In both experiments, the thermal expansion characteristics of the DFRP prevented the wire's movement, therefore it was demonstrated that the use of the DFRP bobbin was effective about the improvement of stability.