HAMILTONIAN MAPS FOR HELIAC MAGNETIC ISLANDS

Magnetic islands in toroidal heliac stellarator vacuum fields are explored with Hamiltonian chaos theory and the associated area-preserving maps. Magnetic field line island chains are examined first analytically, with perturbation theory, and then numerically to produce Poincare sections, which are compared with H-l Heliac stellarator puncture plot diagrams. Rotational transform profiles are chosen to permit the comparison of twist map and nontwist map predictions: with field line behaviour computed by a field line tracing computer program and observed experimentally.