The Influence of the Copper Stabilizer On the Current Carrying Capacity of REBCO Tapes and Stacks With Various Joints at High Ramp Rates

In this work, we experimentally investigate the current carrying capacity of single REBCO tapes and stacks made 5 12 mm REBCO tapes with a 25 μm copper stabilizer in liquid helium in comparison with those made of bare tapes with no stabilizer at current ramp rates up to 55 kA/s. The motivation for the research was checking the usability of REBCO stacks as basic sub-elements for high current superconducting cables operating in fast cycling modes at 4.2 K. An original experimental technique was employed to induce the extremely high ramp rates. During the tests, one or 5-folded stacks curled into rings 95 mm dia with different types of joints were charged in the external magnetic field generated by an outer solenoid at ramp rates up to 1.6 T/s. The curled REBCO stacks were either soft-soldered over their entire length or contained local joints only. The maximum screening current induced in the samples during the outer solenoid charging
I
_max
was registered. Our experiments showed that the current carrying capacity of the REBCO tapes and stacks was strongly affected by the absence or presence of the copper stabilizer as well as the type of the joint. The reasons for the
I
_max
limitation for the copper stabilized and bare samples are also briefly discussed.