Design and optimization of a HTS insert for solenoid magnets

With the availability of High-Temperature Superconducting (HTS) prototype cables, based on high-performance REBCO Coated Conductor (CC) tapes, new designs can now be made for large bore high field inserts in superconducting solenoids, thus extending the magnet operating point to higher magnetic fields. In this work, as an alternative approach to the standard trial-and-error design process, an optimization procedure for a HTS grading section design is proposed, including parametric electromagnetic and structural analyses, using the ANSYS software coupled with a numerically-efficient optimization algorithm. This HTS grading section is designed to be inserted into a 12 T large bore Low Temperature Superconducting (LTS) solenoid (diameter about 1 m) to increase the field up to a maximum value of at least 17 T. The optimization variables taken into consideration are the number of turns and layers and the circle-in-square jacket inner diameter in order to minimize the total needed conductor length to achieve a peak field of at least 17 T, while guaranteeing the structural integrity and manufacturing constraints. By means of the optimization, an optimal 360 m total conductor length was found, achieving 17.2 T with an operating current of 22.4 kA and a coil comprised of 18 x 12 turns, shortened of about 20% with respect to the best initial candidate architectural design. The optimal HTS insert has a bore compatible with manufacturing constraints (inner bore radius larger than 30 cm). A scaled HTS insert for validation purposes, with a reduced conductor length, to be tested in an advanced experimental facility currently under construction, is also mentioned. (C) 2016 Published by Elsevier Ltd.