Equilibrium and stability analysis of L=2 helical Heliac devices

Summary form only given. A L=2 Helical Heliac is a newly proposed helical-axis configuration of a Heliac type in which toroidal coils and a center conductor is replaced by L=2 helical coils with a double helix. We have studied the equilibrium and stability properties of HH devices as well as the vacuum properties. The main results are as follows. (1) The values of rotational transform increase as the helical displacement of a helical coil axis increases. (2) The displacement of a magnetic axis outwards for finite beta plasma confinement is inversely proportional to the helical displacement of a helical coil axis. (3) There is an example of the L=2 HH magnetic configuration with a magnetic well depth /spl sim/4.5% and well region r/sub well//r/sub max/ /spl sim/100%. (4) By adjusting the vertical field coil current, plasma in some HH magnetic configurations turns into Mercier stable configurations in whole regions for beta values more than 1%.