Transport Simulation of Helical Plasmas Using the TASK/TX Code

概要

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It is widely accepted that the radial electric field strongly affects plasma confinement through the transport process. We have analysed the time evolution of the radial electric field and the radial transport in plasmas in a helical magnetic configuration by extending the TASK/TX code [M. Honda and A. Fukuyama, J. Comput. Phys. 227, 2808 (2008)]. TASK/TX is a one-dimensional dynamic transport code originally developed for axisymmetric plasmas. A set of flux-surface averaged fluid equations is solved simultaneously, rather than a set of diffusion equations based on the flux-gradient relations. TASK/TX consists of one-dimensional two fluids (electron and ion) equations, Maxwells equations and diffusion equations of neutrals. To apply TASK/TX to helical plasmas, we have included two additional effects; helical neoclassical viscosity force and diffusion due to magnetic braiding. Plasma transport simulation is carried out mainly using the LHD parameters. We obtained negative radial electric field (ion root) with ion heating and positive radial electric field (electron root) with electron heating. Effects of magnetic braiding are also studied.