Specific natures of ballooning mo-des stability in conventional stellarators

Results on studying ballooning modes stability in conventional stellarators obtained through application of three-dimensional codes, showed that an account of the systems three-dimensionality may essentially change botch the conditions of the ballooning modes stability and the structure of the most dangerous perturbations as compared to the results, obtained by the two-dimensional description of the equilibrium configuration in stellarator approximation. The three-dimensional calculations showed that most dangerous are the perturbations, the maximum whereof is located on the torus external contour by the longitudinal coordinate values, corresponding to vertically oriented ellipse of the magnetic surfaces cross section, where the curvature of force lines lest of ale promotes development of instability