CONVERGENCE AND EXTRAPOLATION STUDIES WITH THE "FIT" 3-D CODE
The FIT Code, designed to compute ideal MHD equilibria, was tested on six configurations representative of stellarator research. The code was modified in the following points: 1) Iteration methods extended by conjugate gradient method for varying dependent inverse variables r,z, and lambda simultaneously; 2) The non-uniqueness of the variables eliminated by appropriate coupling of r and z coefficients in the Fourier series. The selected configurations are: 1) an axisymmetric Solov'ev equilibrium, (energy computed analytically); 2) an axisymmetric high-beta equilibrium (lambda not equal O) necessary to obtain reasonable numerical solutions); 3) a low aspect ratio (A approximately equal 4) l=2 configuration; 4) an ATF model; 5) a W VII-AS; and 6) a Heliac. The results are presented in detail and compared with those of other codes. Accuracy is checked by two scalars, energy and mean axis shift. Usually 20-26 coefficients in the r,z and lambda series were sufficient to eliminate poloidal and toroidal discretization errors in the 3D cases. The r-z coupling was adjusted. Extrapolation in the mesh size is necessary. For energy and axis shift a polynomial in DELTAs**2 was used. Energy errors are more than one order of magnitude below the respective values usually obtained with codes based on difference methods in all dimensions. Within the accuracy of FIT or BBG/BETA results the agreement is excellent.
Bibliographic Reference: 5TH INTERNATIONAL WORKSHOP ON STELLARATORS, SCHLOSS RINGBERG, BAVARIA (GERMANY), SEPT. 24-28, 1984 VOL. I, PP. 377-386, EUR 9618 EN (1985) FS, VOL. I AND VOL. II, 787 P., BFR 3500 (BOTH VOLUMES), EUROFFICE, LUXEMBOURG, POB 1003
Record Number: 1989124115500 / Last updated on: 1987-01-01
Available languages: en