Two-Parameter Modified Rigid Rotor Radial Equilibrium Model For Field-Reversed Configurations

A new equilibrium pressure profile is proposed that extends the rigid rotor (RR) model with a simple unified expression P = P(psi; beta(s), alpha, sigma) for both inside and outside the separatrix. A new method is described for solving the field-reversed configuration (FRC) one-dimensional (1D) equilibrium with only two parameters. The radial normalized FRC equilibrium profiles for pressure, magnetic field, and current density can be uniquely determined by the dimensionless parameters of beta(s)equivalent to P-s/B-e(2)/2 mu(0)) and delta(s) equivalent to L-ps/R-s. This modified rigid rotor (MRR) model has sufficient flexibility to accommodate narrow scrape-off layer (SOL) widths and hollow current density profiles, and can be used to fit experimental measurements. A database of 1D plasma equilibria in the (beta(s), delta(s)) space is provided for the convenience of real-time approximate FRC equilibrium reconstruction. The detailed one-dimensional (1D) characteristics of the equilibrium models are investigated analytically and numerically. The 1D results from the MRR models are also validated using two-dimensional (2D) Grad-Shafranov (G-S) equilibrium solutions.