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Description
This study presents the conduction-cooled current injection design/thermal gradient and cyclic testing for a ReBCO canted cos-theta magnet designed and Fabricated by LBNL (magnet C2). This coil has been measured at 77 K (LN2) and 4.2 K (liquid helium), as previously reported by LBNL, but in this case, we used a large conduction cooled cryostat available at OSU. Testing this coil in a conduction cooled mode has relevance for the advanced accelerator program in the US, as there are continuing incentives to move away from 100% liquid cryogen cooling, including the development of “green” accelerator technologies. The coil had four layers, each wound with ReBCO coated conductor based CORC cable. The magnet itself was 613 mm long, and the total length with current leads was 1.5 m (our size limit). The magnet mass was 75 kg, with an OD of 127 mm, and a 77 K nominal Ic of 300A. The coil was mounted on a Cu cold ring which was cooled by two Sumitomo RDK 415D cold heads with a total cooling of 3 W at 4.2 K, and with cooling of 150 W (total) at 77 K. The magnet and current leads were left on the G-10 strongback, which was laid across the Cu cooling ring, and clamped down. Conduction cooling was performed with the use of a series of Cu straps which were attached to the magnet end rings, and also a thermal radiation shield, and then to the cold ring. We then tested the base temperature, and then performed a number of cooling cycles, and measured the thermal gradient. The results of these measurements and the comparison to FEM models is discussed. HTS sister connections were made to the current injection lugs of the magnet, and low level currents (up to 10 A) were injected at 77 K to explore the development of thermal gradients with current injection, and these results are reported.
This work is supported by the United States Department of Energy, Office of Science, Division of High Energy Physics under Grant DE-SC0011721.
