BE and FE solutions to open boundary potential problems with helical symmetry

The authors present boundary element (BE) and finite element (FE) solutions to open boundary potential problems with helical symmetry. The BE and FE equations are introduced in the twisted coordinates in which helical potential fields can be regarded as being two-dimensional. In the FE analysis, `transfinite´ elements are used for modeling open boundaries. Magnetic fields around a helical solenoid are analyzed using the above-mentioned methods and those numerical solutions are shown to be in good agreement with analytic solutions. Moreover, electric fields around a twisted-pair line are calculated, and it is shown that the fields come to be concentrated in the vicinity of the lines as the helical pitch is increased