RAMP RATE INSTABILITY OF MULTIFILAMENTARY SUPERCONDUCTORS DUE TO LONGITUDINAL MAGNETIC-FIELD

Ramp rate instability due to an external longitudinal magnetic field o f Cu/NbTi multifilamentary superconductor was studied experimentally a nd theoretically. Quench current was measured when transport current a nd external magnetic field with transverse and longitudinal component were ramped up simultaneously, At increasing ramp rate, quench current of S-twisted (anticlockwise-twisted) multifilamentary superconductor was degraded in the positive longitudinal magnetic field parallel to t he transport current, The calculated stability limit agreed with the e xperimental quench current within an error of 17 %. Furthermore, we nu merically estimated the dependence of stability limit on ramp rate and longitudinal magnetic field for a multifilamentary superconductor in practical large scale devices.