Optimization of winding geometry of Bi(2223)Ag coils with respect to external magnetic field

A theoretical model, which enables to estimate the critical currents distribution in the winding of HTS cylindrical coils exposed to external magnetic field, was developed. The model takes into account the real angular dependence (anisotropy) of the I/sub c/(B) characteristic of Bi(2223)Ag tape. It is shown how the change in the winding geometry within the same overall tape length and the value of applied external magnetic field parallel with the magnet axis influences both, the critical current and the resulting magnetic field generated by the magnet itself. It is predicted that applying a low magnetic field parallel to the HTS magnet axis may result in a relatively high increase in the magnet critical current (up to 30-40%) if compared with the magnet critical current achieved without the presence of external magnetic field. An example of optimizing the magnet winding geometry by using the different lengths of the Bi(2223)Ag multifilamentary tape of Vacuumschmelze GmbH production is presented.