Measurements of magnetic field induced by screening currents in YBCO solenoidcoils

Abstract

Coated conductors are promising candidates for the construction of high-field magnets. Insolenoid magnets built with coated conductors, large screening currents are induced in thesuperconducting layer by the radial component of the magnetic field. The screeningcurrents generate a screening field that reduces the central magnetic field and affects theaxial uniformity and temporal stability of the magnetic field. The effects of the screeningfield on the central magnetic field have been measured in one short coil (minimum volumecriterion) and in one long coil (geometry similar to NMR coils). Depending on theoperating current, the reduction of the central field due to the screening fieldreached 14% in the short coil and 8% in the NMR-type coil. In the NMR-type coil,the temporal stability of the magnetic field was also measured: a drift of about10 ppm h − 1 after a holding time of 3 h was observed.