Reduction of mechanical losses by use of ZFRP bobbins in AC superconducting coils

We have studied a technique to reduce mechanical losses under AC operation by use of a particular bobbin's material as a superconducting coil. The material is a Zylon fiber reinforced plastic (ZFRP). From a viewpoint of mechanical loss reduction, a winding tension at coil-operating temperature is an important element. Since the ZFRP bobbin makes the control of the tension possible, the losses of the coils having the ZFRP bobbins can also be controlled. To investigate the effect of the loss reduction, 9 sample coils whose winding tensions at cryogenic temperature are different from each other, are prepared. The results of the experiment show that the coils whose winding tensions at cryogenic temperature are strong make the reduction of mechanical losses possible. On the contrary, the mechanical losses are significantly greater in the coils having weak tensions. This paper reports that the ZFRP is effective as the superconducting coil's bobbin.