Contact resistance between two REBCO tapes under load and load-cycles

TL;DR

This study measures the contact resistance between REBCO tapes under various mechanical loads and cycles, revealing how pressure and cycling affect Rc, which is crucial for optimizing no-insulation superconducting magnet performance.

Contribution

The paper provides the first experimental measurements of Rc for REBCO tapes under load and cyclic conditions, linking results to Holm's contact theory.

Findings

Rc decreases with increasing pressure

Rc gradually increases with load cycles

Measured Rc ranges from 26 to 100 microOhm-cm^2

Abstract

No-insulation (NI) REBCO magnets have many advantages. They are self-protecting, therefore do not need quench detection and protection which can be very challenging in a high Tc superconducting magnet. Moreover, by removing insulation and allowing thinner copper stabilizer, NI REBCO magnets have significantly higher engineering current density and higher mechanical strength. On the other hand, NI REBCO magnets have drawbacks of long magnet charging time and high field-ramp-loss. In principle, these drawbacks can be mitigated by managing the turn-to-turn contact resistivity (Rc). Evidently the first step toward managing Rc is to establish a reliable method of accurate Rc measurement. In this paper, we present experimental Rc measurements of REBCO tapes as a function of mechanical load up to 144 MPa and load cycles up to 14 times. We found that Rc is in the range of 26-100 uOhm-cm2; it decreases with increasing pressure, and gradually increases with number of load cycles. The results are discussed in the framework of Holm's electric contact theory.