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Medium density (3×109 cm−3) and high density (3×1012 cm−3) plasmas, generated by low and medium power rf techniques, have been used for the implantation of 10–20 keV nitrogen ions into mild steel targets which were immersed in the plasma and biased to −20 kV. Use of the high density plasma resulted in significant damage to the surface by arcing. At medium densities the nitrogen was implanted to a depth and dose consistent with expectations, there was no arcing damage, and tests showed improved wear and hardness compatible with the level of implantation.

Small aspect ratio tokamak configurations are produced by adding a toroidal magnetic field to the rotamak. Configurations with toroidal fields ranging up to ∼ 200 G at the magnetic axis are studied. Typical parameters are Itor ∼ 2 kA, Bpoi ∼ 50 G, q0 ∼ 1-3, ne (peak) ∼ 1019 m−3, Te ∼ 12 eV, τp ∼ 15 μs and τe ∼ 5μs for an RF input power of ∼ 40 kW. Most features of these configurations can be modelled by an MHD equilibrium code. The presence of the toroidal field is observed to have a significant influence on the rotating magnetic field current drive mechanism.

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A series of equilibrium configurations has been generated in the Australian Atomic Energy Commission's experimental rotamak device. All configurations have been sustained for the duration of the rotating magnetic field ( -10 ms). Control of the separatrix shape from oblate to prolate, and of the separatrix position, has been demonstrated. The electron temperature, electron number density and current density profiles have been determined for a prolate equilibrium configuration (typical maximum values are T, -10 eV; ne -6 x 10l8 m-3), A current carrying plasma sheath has been observed outside the separatrix. An M H D code has been used to model the equilibrium.