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Finite-element analysis of the strain distribution due to bending in a REBCO coated conductor for canted cosine theta dipole magnet applications Permalink https://escholarship.org/uc/item/760535cn Journal IEEE Transactions on Applied Superconductivity, 29 (5) Abstract-High-current cables using REBCO tapes can be used to develop high-field dipole magnets. However, the strain accumulated during cable fabrication and coil winding may reduce the critical current of the conductor. Therefore, it is important to properly consider the strain when designing high-field magnets. In this work, we used structural finite element analysis to predict the strain experienced by a REBCO tape during bending in configurations relevant to the fabrication of high field accelerator magnets, in particular, the mechanical strain generated during cable fabrication and winding in a canted-cosθ (CCT) dipole configuration.We considered two different cable options: (A) flat tape that lay in the mandrel channel and (B) a REBCO tape helically wound around a circular copper core, the typical configuration of the conductor in round core cable (CORC®). Strain accumulated during tape winding is studied for different core diameters and winding tilt angles. FEA longitudinal strain results were compared with the simulations for configuration A, where higher strain was observed experimentally. Configuration B was verified indirectly by comparing experimentally measured Ic with the one predicted (based on the longitudinal strain) as function of the bending diameter. Good agreement was found up to a bending diameter of 30 mm. The presented results will help to understand the impact of bending on REBCO tapes and CORC ® wires to develop high-field magnets. Index Terms-High-temperature superconductors, yttrium barium copper oxide, superconducting cables, superconducting magnets This is the author's version of an article that has been published in this journal. Changes were made to this version by the publisher prior to publication.The final version of record is available at http://dx.

Interest for high magnetic fields (>16 T) for applications in high energy physics (HEP) and fusion machines, requires the development of high current cables capable to withstand the large forces, mechanical and electromagnetic, experienced during manufacturing and operations. The critical current (Ic) of REBCO tapes depends on strain, magnetic fields and operational temperatures. Understanding how these parameters affect the Ic of the conductor will be critical to develop robust high-current REBCO cables. However, there are limited reports on the strain dependence of Ic, in particular at high fields and elevated temperatures relevant for future high-field compact fusion reactor magnets.We present Ic of commercial REBCO tapes measured as a function of compressive and tensile strain (between -0.6% and +0.65%) at high magnetic fields (12 T and 15 T) and different temperatures (within 4.2 K-40 K). Results at 4.2 K and 20 K showed less than 5% reduction in the normalized Ic at high strain, while a stronger strain dependence was observed at 40 K. Samples tested at 12 T and 4.2 K showed similar strain dependence as 15 T and 4.2 K. In all tested conditions, the tape experienced reversible Ic reduction in both tension and compression. Finite element analysis was used to predict the residual thermal strain accumulated in the REBCO layer prior of testing to account for the effect of the cooldown. A method was also developed to account for the current sharing observed between the sample and the sample holder during the ramp of the current. Our results provide useful input for the development of high-field fusion and HEP magnets using REBCO conductors.Index Terms-High-field fusion magnets, high-temperature superconductors, strain measurement, superconducting cables, yttrium barium copper oxide. R This is the author's version of an article that has been published in this journal. Changes were made to this version by the publisher prior to publication.The final version of record is available at http://dx.

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