Method of rapid determination of MHD equilibrium properties with the modified version of the SURFAS code

摘要

Rapid determination of MHD eqilibrium properties of tokamak plasmas is carried out by means of an approximation method based on the use of database files. These are computed a priori from MHD equilibrium solutions obtained by performing reconstruction to match experimental measurements, which include motional Stark effect (MSE) data. The procedure carries out a single iteration of Newton's method to determine the poloidal variation of the toroidal plasma current density in the equilibrium form j(sub (phi)) = (minus)2(pi)((mu)(sub 0)Rp(prime) + FF(prime)/R) by representing p(prime)((psi)) and F((psi))F(prime)((psi)) in series expansions of Chebyshev polynomials. The polynominal expansion coefficients are obtained through a least-squares data fitting process similar to that used in the equilibrium reconstruction. Knowing the current density j(phi) allows the determination of the internal q-profile from the MSE data. This important stability parameter is generally unavailable from a current filament model. Numerical results calculated in this approach are compared with those determined from an accurate solution of the Grad-Shafranov equation, subject to a similar set of magnetic and pressure measurement constraints.