An Integrated Coil Form Test Coil Design for High Current REBCO DC Solenoids

REBCO high-temperature superconductors (HTS) are being utilized to extend the limits of dc solenoidal magnetic fields to 32 T in a user magnet. It is reasonable to expect that these field limits will continue to be surpassed resulting in higher stored energy coils. These larger coils will require kilo-amp level currents to reduce their inductance to manageable levels. Lower inductance coils will be necessary to eliminate unacceptably long ramp times and expensive high voltage isolation hardware by reducing inductive charging and quench voltages. A novel high-current coil concept, using an integrated coil form (ICF), is described here. The coil concept is being developed in combination with a high-current flux pump at the University of Cambridge. The first test coil will be charged to 5.6 kA and will demonstrate the ICF coil winding technique, current lead connections, layer transitions, and coil terminations, as well as ramping and quench performance. The test coil design is described

Double disordered YBCO coated conductors of industrial scale: high currents in high magnetic field

A significant increase of critical current in high magnetic field, up to 31 T, was recorded in long tapes manufactured by employing a double-disorder route. In a double-disordered high-temperature superconductor (HTS), a superimposing of intrinsic and extrinsic disorder takes place in a way that (i) the intrinsic disorder is caused by local stoichiometry deviations that lead to defects of crystallinity that serve as pining centers in the YBa2Cu3O x−δ matrix and (ii) the extrinsic disorder is introduced via embedded atoms or particles of foreign material (e.g. barium zirconate), which create a set of lattice defects. We analyzed possible technological reasons for this current gain. The properties of these tapes over a wider field-temperature range as well as field anisotropy were also studied. Record values of critical current as high as 309 A at 31 T, 500 A at 18 Tm and 1200 A at 5 T were found in 4 mm wide tape at 4.2 K and B perpendicular to tape surface. HTS layers were processed in medium-scale equipment that allows a maximum batch length of 250 m while 22 m long batches were provided for investigation. Abnormally high ratios (up to 10) of critical current density measured at 4.2 K, 19 T to critical current density measured at 77 K, self-field were observed in tapes with the highest in-field critical current. Anisotropy of the critical current as well as angular dependences of n and α values were investigated. The temperature dependence of critical current is presented for temperatures between 4.2 and 40 K. Prospects for the suppression of the dog-bone effect by Cu plating and upscale of processing chain to >500 m piece length are discussed