Optimization of Internal Splicing for Non-Insulated HTS Magnets

Abstract

REBCO tapes stand out as the most promising conductors for various applications, spanning physics experiments and societal use. Manufactured through a now-consolidated yet intricate process, these tapes yield continuous pieces reaching hundreds of meters. However, this process limits the length of tape that can be wound into a coil without requiring internal splicing. Splices are inherently the weakest points in the coil due to heat generation and reduced current-carrying performance. While small non-insulated coils naturally self-protect against splice-related risks through current bypassing, larger coils, conduction-cooled, or partially insulated ones often experience a diminished self-protecting behaviour, necessitating careful consideration of splices in the coil design. Moreover, larger magnets often relies on multiple cable co-winding, making this issue more challenging to explore and to understand. To this purpose, this study aims at investigating various joint layouts for double tape HTS cable through electrical experiments. The manufacturing procedure, along with the measured performances of the different splice geometries produced using various brazing alloys and fluxes, is discussed. Finally, numerical models with lumped elements are utilized to analyse experimental results and to describe the joint behaviour. This work serves as an initial step toward a splice-inclusive design approach for magnets.