Critical transverse compressive stresses of straight and bent CORC$^\circledR$ wires with and without impregnation

TL;DR

This study evaluates the critical transverse compressive stresses of CORC$^ extregistered$ wires under various conditions, including straight, bent, impregnated, and unimpregnated states, using a specialized experimental setup in liquid nitrogen.

Contribution

The paper introduces an experimental system to measure critical transverse stresses of CORC$^ extregistered$ wires considering bending and impregnation effects, relevant for accelerator magnet applications.

Findings

Bending and impregnation significantly influence the critical transverse pressure.

Critical pressures at 3% and 5% critical current reductions are quantified.

Impregnation with Stycast and paraffin wax alters the transverse stress response.

Abstract

CORC$^\circledR$ wires are a promising superconductor for accelerator magnet applications. While their excellent uniaxial tensile properties have been well established, potential degradation under transverse compression remains a significant concern for accelerator magnets, in which transverse compression is a primary stress experienced by superconductors. To evaluate the critical transverse compressive stresses of ReBCO conductors, we developed an experimental system that enables testing of samples both with and without impregnation in liquid nitrogen. Furthermore, because bending strain induced during coil winding may influence the critical compressive response of CORC$^\circledR$ wires, the apparatus was also modified to allow testing under the bending condition. In this study tests were conducted for five configurations: (1) straight wires without impregnation, (2) bent wires without impregnation, (3) straight wires with Stycast 2850 FT impregnation, (4) bent wires with Stycast 2850 FT impregnation, and (5) bent wires impregnated with paraffin wax. The transverse pressures corresponding to 3% and 5% reductions in the critical current are reported. The effects of wire bending and impregnation on the critical transverse pressure are analyzed, and the implications for transverse stress levels in accelerator magnet conductors are discussed.