Improved training in paraffin-wax impregnated Nb3Sn Rutherford cables demonstrated in BOX samples

TL;DR

This study demonstrates that paraffin wax impregnation in Nb3Sn Rutherford cables significantly reduces training requirements and enhances resilience to cycling, compared to traditional resin impregnation, in a specialized test platform.

Contribution

It introduces a novel impregnation method using paraffin wax that improves performance and reduces training in Nb3Sn magnet samples.

Findings

Paraffin wax-impregnated samples reached critical current without training.

Wax-impregnated samples showed high resilience to thermal and mechanical cycling.

Resin-impregnated samples exhibited extensive training and limited performance.

Abstract

Resin-impregnated high-field Nb3Sn type of accelerator magnets are known to require extensive training campaigns and even may exhibit performance-limiting defects after thermal or electromagnetic cycling. In order to efficiently explore technological solutions for this behaviour and assess a wide variety of impregnation material combinations and surface treatments, the BOnding eXperiment (BOX) sample was developed. BOX provides a short-sample test platform featuring magnet-relevant Lorentz forces and exhibits associated training. Here we report on the comparative behaviour of BOX samples comprising the same Nb3Sn Rutherford cable but impregnated either with common resins used in high-field magnets, or with less conventional paraffin wax. Remarkably, the two paraffin wax-impregnated BOX samples reached their critical current without training and are also resilient to thermal and mechanical cycling. These rather encouraging results strongly contrast to those obtained with resin impregnated samples, which show the characteristic extensive training and at best barely reach their critical current value.