REBCO Coil With Robust Behavior Against Local Defects Wound Using Two-Tape Bundle

Abstract

REBa2Cu3O7-δ (RE: rare earth/Y) coated conductors have good critical current characteristics under high magnetic fields. Their application to superconducting magnets generating above 25T is under active study. However, performance inhomogeneity along their length may cause damaging hotspots. Adapted winding technologies are needed to mitigate this phenomenon. One of such winding techniques is the twotape bundle co-winding method, where two REBCO tapes are co-wound along with an isolating tape to form the conductor. To test this solution, a double pancake coil was wound with one of the pancakes having an artificially degraded short section on one of the tapes, where the critical current is close to 0. The I-V characteristics of both damages and undamaged pancakes are compared and analyzed based on critical current density Jc(T,B, θ) data, in terms of operation margins. At low voltage levels, similar I-V characteristics for damaged and undamaged pancakes are observed. The behavior is found similar to the expected behavior of a coil whose critical current Ic is locally reduced by 50 %, demonstrating the effectiveness of two-tape bundle for current redistribution in case of local defect, even under high current density.

First Validation of Robust REBCO Insert Concept on a Large 20-Pancake Prototype Reaching Up to 25 T

“…The conductor is a bundle of two tapes in face to back configuration. In previous studies [9] this ensured sufficient current redistribution between the tapes in case of local degradation of the critical current even though the distance between layers is higher than in face-to-face configuration. The turn to turn electrical insulation is a co-wound Polyimide tape (50 µm thick in this case) with Fluorine coating, which as mentioned before serves also as non-stick layer to prevent delamination.…”

“…To reduce the risk that an local defect could prevent operation at nominal current, the conductor is formed of two REBCO tapes face -to-back, so that current can be shared [9].…”

The Application of X-ray Micro-CT in the Study of HTS Tape Coils

“…Modern second-generation high-temperature superconductors (HTS) are composite tapes consisting of a large number of layers with different physical properties [1]. It is known that a lot of experimental coils are produced in different research centers [2][3][4][5][6][7][8][9]. However, the manufacturing technology for HTS tapes is still improving, which has led to a change in their properties.…”

A High Performance Insulated REBCO Pancake With Conductive Cooling Capability

“…1 shows the configuration of the tapes in the winding. The pancake was wound with REBCO Fujikura FESC tapes with artificial pinning center [1,7]. The insulated Hastelloy reinforcement co-wind is actually a THEVA substrate.…”