A New Method to Calculate Conductor Magnetization in Accelerator Dipoles: Fid-Bau Portal

A New Method to Calculate Conductor Magnetization in Accelerator Dipoles

Avest, D. / Klundert, L. J. M.

Abstract During the ramping of superconducting dipole magnets as used in particle accelerators as the proposed SSC or CERN-LHC, magnetization in the conductor will manifest itself, perturbing the field homogeneity of the dipole. A numerical method was developed that covers the calculation of magnetic field inside the conductors, keystoned cables, current redistribution due to the variation of magnetic field with time as well as the multipole distribution in the dipole. For the calculation of current redistribution in a cable a keystoned cable geometry has been assumed, although the method applies to any geometry. The model incorporates saturation in the cable. In the case of an unsaturated cable the current redistribution can be described completely analytically. Also the model allows the calculation of the interstrand coupling loss as a function of the time-varying magnetic field. Finally, field remanency due to persistent currents in the filaments is described. The model was converted into a computer code and applied to the design of a CERN-LHC 10T dipole magnet. A relation will be presented that describes the dependence of the multipole distribution on the time varying field as well as on a few material properties. Also the effect of persistent currents on the multipole distribution will be demonstrated.