Design of CCT6: A Large Aperture, Nb$_3$Sn Dipole Magnet for HTS Insert Testing

We present the design of a four-layer, Canted Cosine Theta (CCT) Nb
$_3$
Sn dipole magnet as part of the general R&D program for high field superconducting magnets supported by the US Magnet Development Program (US-MDP). Future testing with High-Temperature Superconducting (HTS) inserts in a hybrid configuration motivates the design’s large clear aperture of 120 mm and target operating dipole field of 12 T at 4.2 K. First, we present a graded magnetic design utilizing existing Nb
$_3$
Sn cables which results in 30% operating current margin at the target field. We then share results from a 2D mechanical analysis which makes use of an idealized external structure to provide initial guidance for design studies. This mechanical analysis is extended to demonstrate compatibility of the CCT6 design with a mechanical support structure, based on key and bladder technology, currently considered for use within multiple US-MDP high-field magnet programs.