Study of plasma equilibrium reconstruction on HL-2A

An equilibrium reconstruction code is a basic tool for determining the plasma position, boundary, shape and current density profile in a tokamak discharge. The equilibrium reconstruction code CPF has been written to make these calculations. It uses a polynomial to describe the spatial distribution of current density. The coefficients of the polynomial are determined by the best least squares fit to the internal and external magnetic measurement data. A finite difference method is used to solve the Grad-Shafranov equation. The equilibrium magnetic surfaces satisfying the convergence criterion is obtained by Picard iteration. The CPF equilibrium reconstruction is also checked by comparing to results obtained by the equilibrium code SWEQU. The CPF code is stable and has been used for several years.