Critical Current Densities of 482 A/mm² in HTS CrossConductors at 4.2 K and 12 T

High temperature superconductors (HTS) CrossConductor (HTS CroCo) is a twisted stacked tape conductor optimized for a high current density and simple long-length fabrication. We report on recent achievements in the fabrication of HTS CroCos of only 3.6-mm diameter made from 3- and 2-mm-wide rare-earth-barium-copper-oxide tapes. These conductors showed a critical current of 1.5 kA at T = 77 K, self-field in agreement with the expectations from single tapes. In order to investigate the performance, also at low temperatures and high magnetic fields, a dedicated sample holder was designed to allow temperature- and field-dependent measurements in the force magnetic field current (FBI) test facility. We observed critical currents of nearly 5 kA at T = 4.2 K and B = 12 T leading to an engineering critical current density of 482 A/mm 2 . At elevated temperatures, the sample's performance followed well the expectation from the individual tapes. With the availability of tapes with thinner substrates, it can be extrapolated that the current density could reach more than 1000 A/mm 2 at T = 4.2 K and B = 12 T.