Examples of Analytical Field Calculation
2-D field calculation
Modeling ideal cos Θ current distributions
To model a shell with an ideal cos Θ current distributions we use the COSPHI-option from the "Design Variables"-table. The COSPHI-option distributes conductors in the specified blocks over the given angle by adapting the inner outer conductor width such that ideal sector geometries are generated. It then varies the strand currents according to their angular position and according to the "Type of Coil/Ref. Field"-variable from "Global Information". The specified block current in the "Block Data 2-D"-table is used as the amplitude of the cos Θ current distribution. The number of conductors serves thus no other purpose than to specify a discretization of the cos Θ current distribution. About 50 conductors are used for the generation of the current distribution shown in Fig. 12.1 (left).
The following input produces the field configuration in Fig. 12.1 (left). The "Layer Definition"-option is 'on', but the COSPHI option works with the "Symmetric Coil"-option as well.
To obtain the pure sextupole field shown in Fig. 12.1 below (right) we specify the COSPHI angle in the design variable block to 30 deg. The number of conductors can be reduced to 20.
