The stability and the low m, n Alfven spectrum of the generalized Haas equilibrium, characterized by three parameters (ellipticity b/a, shift of the magnetic axis delta , triangularity lambda ) and analysed previously, are studied by both analytical and numerical methods. To that end, an energy principle is derived for the description of Alfven modes in high-beta Tokamaks. Based on a non-orthogonal flux coordinate system, general representations for both the plasma and the vacuum energy are presented. The influence of beta and triangularity on the spectrum of the pressureless plasma cylinder is calculated using a perturbation analysis in delta and lambda . It is shown that the degeneracy of the zero-order system is removed and that the various mode couplings cause additional instabilities. With the help of numerical program HIBAT, the lowest branches of the spectrum and the eigenfunctions are computed numerically for arbitrary values of b/a, lambda and delta . The convergence of the method is discussed.
Excitation of toroidal Alfvén eigenmode by energetic particles in DTT and effect of negative triangularity