Discontinuous Galerkin modeling of plasma turbulence in a simple magnetized torus

Plasma turbulence in the Texas Helimak, a simple magnetized torus (SMT) experiment, has been simulated with fluid and gyrokinetic continuum models that employ the discontinuous Galerkin (DG) computational method. SMTs are physical approximations of a sheared cylinder and, with simple magnetic geometry and extensive diagnostics, are useful for validating numerical models. With helical, open field lines and magnetic shear, the Helimak is a good model of the plasma turbulence in the scrape-off layer (SOL) region of tokamaks or other fusion devices. This region lies outside the last closed magnetic flux surface and plays an important role in determining the exhaust of particles and heat, as well as setting conditions in the core plasma.

Simulation results were compared with experimental data, and, in particular, the gyrokinetic continuum model reproduced key features of experimental data. Differences in the comparison indicate which features are necessary to include in future models. Furthermore, the DG algorithms are well suited to run efficiently on highly parallel computer architectures and also maintain conservation properties of the Hamiltonian gyrokinetic system being modeled. A moment-conserving collision operator has been implemented in this model, and results are verified with analytic theory and previous simulations. In general, this research demonstrates the promise of efficient and accurate gyrokinetic modeling of plasma turbulence on open field lines, with important applications to plasma fusion research.