Compensation of magnetization effects in superconducting accelerator magnets

Magnetization effects in the coils of superconducting accelerator magnets deteriorate the field quality at injection field level. The CERN field computation program ROXIE has recently been extended to calculate the persistent currents using a semi-analytical hysteresis model for hard superconductors. The model is combined with the coupling method of finite- and boundary-elements for the calculation of the nonlinear iron yoke. This numerical method avoids the meshing of air domains and of the superconducting coil. Disjoint ferromagnetic iron domains can be meshed independently. This allows the easy modeling of very thin layers of arbitrary shape.