Topic/Type: 1. Plasma Simulation, Invited

The simulation effort for the basic plasma physics experiment TORPEX

P. Ricci1, S. Brunner1, A. Fasoli1, I. Furno1, B. Labit1, B.N. Rogers2, C. Theiler1, T.M. Tran1

1 Centre de Recherches en Physique des Plasmas, EPFL, Lausanne, Switzerland
2 Department of Physics and Astronomy, Dartmouth College, Hanover NH, USA

TORPEX is a toroidal device in which a vertical magnetic field superposed on a toroidal field creates helicoidal field lines with both ends terminating on the torus vessel. As in the scrape-off layer of magnetic fusion devices, the turbulence driven by magnetic curvature and plasma gradients causes plasma transport in the radial direction while at the same time plasma is progressively lost due to flows along the field lines. The configuration and physical conditions facilitates the experimental study of low frequency instabilities and related transport, as they allow more detailed experimental diagnostics and wider parameter scans than are usually possible in fusion devices. The relatively simple magnetic geometry of the TORPEX configuration also enables deep theoretical investigations, analytical development, and makes an accurate comparison between simulations and experiments possible.

We describe a global fluid code that solves the drift-reduced Braginskii equations in the whole TORPEX domain, taking into account the plasma source, plasma losses at the torus vessel, and plasma turbulence driven by the magnetic curvature and plasma gradients. The numerical algorithm uses finite differences for discretizing the spatial derivatives, in particular making use of the Arakawa scheme for handling the advection terms in the perpendicular direction, and a standard Runge-Kutta time stepping algorithm. The details of the parallelization are discussed. We show simulations results and their physical interpretation across a wide parameter space. Comparison with experimental results is discussed, establishing a framework to quantify the agreement between simulation and experimental results.

The simulation code can be easily adapted to perform simulations of other basic plasma physics experiments. In particular, we show the initial results of global simulations of the LAPD device.