Equilibrium Calculation with Toroidal Flow in NIMEQ

Abstract

The focus of this work is to demonstrate the importance of incorporating toroidal rotation in calculating tokamak-like equilibria with axisymmetry. Specifically, this work will focus on showing the impact toroidal flow had on the particle density, poloidal magnetic flux, and toroidal current density. We utilize the analytical form of the thermal pressure, for purely toroidal flow in the isothermal limit. Modifications to NIMROD’s equilibrium solver, NIMEQ, are made to integrate toroidal flow and to ensure NIMEQ's solution fields are self-consistent. The modifications to NIMEQ are benchmarked by the code FLOW created by L. Guazzotto. Results for a low-beta and high-beta tokamak like equilibrium are shown. It is found that for both equilibria the peak particle density significantly shifts and the addition of large rotational inertia causes the toroidal current to be pushed outward. Shift in the max poloidal magnetic flux is found to only be significant for the high-beta equilibrium, due to toroidal flow's influence on the now dominant thermal pressure. It is expected that the addition of poloidal flow will even further alter equilibrium configurations.