Internal helical modes in a plasma high pressure tokamak with noncircular section

Effect of small ellipticity and triangular confuguration of tokamak case section on stability of large-scale inner helical modes m>=1 resulted from toroidal properties and initial value of plasma pressure has been investigated. It is suggested that gradient of longitudinal current density is low, and plasma pressure is not very high. Given is an equation of small oscillations describing behaviour of inner helical modes m>=1 in noncircular section tokamak at high plasma pressure. The effect of ellipticity and triangular configuration on the mode m=n=1 has been considered. Stability of the highest inner helical modes m>1 is investigated. Technique of taking account of the effect of noncircularity due to toroidal properties of magnetic field is presented. An expression for quasicylindrical contribution of ellipticity has been derived. Stability criteria for the inner helical mode m=n=1 and the highest inner helical modes m>1 have been also obtained. It is elucidated that in the case of Dform tokamak it is possible to get stability of large-scale inner helical modes m>=1 by means of corresponding choice of ellipticity and triangular configuration of case section at a high plasma pressure. This permits to obtain a considerable improvement of parameter values <β>