Evolution of magnetic islands in a Heliac

Abstract

Simulations of three-dimensional equilibria in the H-1 Heliac [Fusion Technol. 17, 123 (1990)] with the HINT code [Phys. Fluids B 4, 1539 (1992)] show that the size of a dangerous magnetic island should increase with plasma pressure, but that a destruction of the equilibrium at low β is avoided because the rotational transform evolves to exclude the rational surface concerned. At higher pressures there is evidence of near-resonant flux surface deformations, which may lead to an equilibrium limit. A reconnected equilibrium at still higher pressures exhibits a double island structure, which is similar to homoclinic phase portraits that have been observed after separatrix reconnection in Hamiltonian systems. Show more