High-temperature superconductors in high-field magnets

The properties of both BSCCO conductors and YBCO coated conductors and coils are studied to assess their applicability in high-field magnets. First, the magnetic field dependence of the critical current density in these HTS conductors is measured at 4.2 K in magnetic field conditions ranging from self-field to 45 T and described with equations. The suitability of the average grain misalignment angle to describe the anisotropy in the magnetic field dependence of the critical current density is experimentally verified. Second, the effect of the value of the anisotropy parameter on the magnet design in investigated, resulting in the observation that there are three distinctly different design regimes. Third, the relation between bending, stress, strain and the critical current density is experimentally determined, specifically the critical strain at which the critical current density irreversibly degrades. Small coils are exposed to large Lorentz forces to determine if the onset and propagation of strain induced degradation can be predicted based on conductor data. Fourth, the knowledge gained is used to design, build and test a BSCCO demonstration magnet that targeted and achieved a magnetic field increment of 5 T while operating at 4.2 K in a 20 T background magnetic field. Thus, for the first time, a central field of 25 T is reached inside a superconducting insert. Fifth, an outlook for 30 T superconducting magnets is presented, in the context of the first YBCO insert coils that have shown high strain tolerance and unprecedented current densities at magnetic fields exceeding 30 T.