MERCIER AND RESISTIVE INTERCHANGE INSTABILITIES IN 3-D CODE STELLARATOR EQUILIBRIA
Evaluation of Mercier's criterion in 3D flux variable code (e.g. BETA) equilibria yields insights into several critical aspects of stellarators. Results are presented for W VII-AS, Heliac, ATF and some of its modifications, and l=1,2,3 equilibria, in which the classical PS component of the parallel current density is eliminated. The dominant stabilizing and destabilizing mechanisms are the geometric deepening of the magnetic well, the square of the parallel current density and its dependence on the three-dimensionality of the equilibrium, and the product of the shear S and the quantity H-an averaged parallel current density-absent in the resistive criterion. The above types of stellarators exhibit quite different stability behaviour. W VII-AS becomes unstable at <beta> approximately equal 0.01; ATF remains ideally stable up to <beta> approximately equal 0.03 because of the favourable contribution S.H, but a resistively unstable for beta as low as <beta> approximately equal 0.01. For Heliac and l=1,23 equilibria, the difference between the ideal and the resistive criteria is virtually vanishing. Because of the favourable stability results for helically symmetric Heliac equilibria, <beta> approximately equal 0.3, the beta limit of currently known resistively stable equilibria is really a limit on aspect ratio.
Bibliographic Reference: 5TH INTERNATIONAL WORKSHOP ON STELLARATORS, SCHLOSS RINGBERG, BAVARIA (GERMANY), SEPT. 24-28, 1984 VOL. I PP. 339-356, EUR 9618 EN (1985) FS, VOL. I AND VOL. II, 787 P., BFR 3500 (BOTH VOLUMES), EUROFFICE, LUXEMBOURG, POB 1003
Record Number: 1989124119900 / Last updated on: 1987-01-01
Available languages: en