Recently net currentfree plasma has been intensively investigated in stellarator and heliotron. In this paper both theoretical and experimental studies for the currentfree toroidal plasmas are described in the context of MHD equilibrium, MHD stability and transport.
Energy loss due to impurity ions in a high temperature plasma is discussed in connection with electron impact excitation rates of impurities. The influence of impurity transport process on radiative cooling rates is presented.
An analysis is made on the regeneration process of toroidal magnetic flux of RFP plasma based on Sato's nonlinear driven reconnection model. The expression of magnetic field perturbation due to helical kink instability indicates that resonant helical kink mode is not effective to regenerate the toroidal magnetic flux of RFP plasma. From the limit of the magnetic island width formed by the reconnection driven by the plasma flow due to helical kink mode, the saturation level of the generated toroidal magnetic flux is estimated.