Improvement in stability of superconducting coil by different mechanical properties of bobbins

The Dyneema ® fiber reinforced plastic (DFRP) expands to a direction of the Dyneema fibers during cooling process. Therefore, a winding angle in Dyneema fibers of the DFRP bobbin manufactured by the filament winding method makes possible to control thermal expansion/contraction properties to the circumferential direction on the bobbin. Moreover, DFRP’s frictional coefficients are considerably low. These properties are extremely different from those of GFRP which is generally used as the spacers and the bobbins of superconducting coils. In this paper, the coils fabricated with DFRP and GFRP bobbins are examined in DC and AC operating experiments. When the coil was operated under DC current, the low frictional properties of the coils having DFRP bobbins improved the instability due to the wire motion, on the other hand, in case of AC operating test, the thermal expansion properties of DFRP bobbin could reduce the mechanical losses between the wire and the bobbin.