Numerical Simulation of Non-inductive Startup in the Pegasus Toroidal Experiment

Nonlinear numerical computation is used to investigate DC helicity injection from washer-gun plasma sources in the Pegasus Toroidal Experiment (Univ. of Wisconsin). Resistive MHD simulations with the NIMROD code (nimrodteam.org) are used to model non-inductive startup, with emphasis on the relaxation of the non-axisymmetric current channels into a ``tokamak-like'' plasma. Simulations utilize fully three-dimensional, anisotropic, temperature-dependent thermal conductivity corrected for regions of low-magnetization [Braginskii, Reviews of Plasma Physics, 1965], temperature-dependent resistivity, and Ohmic heating. Off-diagonal Fourier-component coupling is investigated as a means of improving preconditioning of the temperature advance.