Influence of the winding geometry on the critical currents and magnetic fields of cylindrical coils made of Bi(2223)Ag anisotropic tapes

A theoretical model for the calculation of the critical currents of cylindrical magnets made of Bi(2223)Ag tapes has been developed. The model takes into account the real angle dependence of the critical current versus external magnetic field of a short sample, which enables to estimate the critical currents of individual turns of the winding. As a result figures in a 3-D representation showing the position of the weak spots in the winding were obtained. Consequently, a detailed analysis of the influence of the winding geometry on the critical currents and magnetic fields of the cylindrical magnets formed from the set of pancake coils was performed. It is shown that when optimizing the magnet geometry with respect to the inner bore diameter and the overall tape length, there exists only one winding configuration for which the central magnetic field has a maximum. An example of the optimum magnet design, utilizing the data measured on a 55 filament Bi(2223)Ag tape of Vacuumschmelze GmbH production, is presented.