In order to access to the ignition regime of the fusion reactor, the impurity radiation loss and plasma density limit are critical, as well as the energy confinement degradation and plasma beta limit. The density limit might be related to the impurity radiation power loss in helical systems, and be relevant to the radiation and current instability effects in tokamaks. Moreover, to clarify the radial profile and the local energy balance is important for the access to the ignited helical reactor plasma, which was shown using the TOTAL (toroidal transport analysis linkage) code in Ref. [1].
For studying the transport of plasma and impurity ions in fusion reactors, we used several models: zero-D (zero-dimensional) fixed radial profile model, the 1-D transport simulation model and 1-D transport/3-D Equilibrium time-dependent simulation model [1] with low-Z gas and high-Z metal impurity dynamics. The plasma equilibria with arbitrary 3-D shapes are calculated by VMEC code for tokamaks and helical systems including advanced shaped stellarators [2]. The radial electric filed is determined by the neoclassical transport flux in helical system, and the impurity ion transport is analysed using neoclassical and anomalous transport models. For the impurity dynamics, the rate equation and diffusion equation are solved using IMPDYN code with ADPAC code, and the line, bremsstrahlung and synchrotron radiations are evaluated comparing with non-local CYTRAN synchrotron radiation results [3].
In the conference, we will show the simulation model of impurity transport in tokamak and helical plasmas, suggest the relation between the density limit and the impurity radiation loss, clarify the permissible impurity level for reactor ignition access, and discuss on the neoclassical and anomalous transport of impurity ions in 3-D shaped plasmas. Finally we will summarize the role of impurity ions on the toroidal fusion plasma dynamics

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