Hennequin, P.; Dubois, M.A.; Nakach, R. Association Euratom-CEA, Centre d'Etudes Nucleaires de Cadarache, 13 - Saint-Paul-lez-Durance (France). Dept. de Recherches sur la Fusion Controlee1991
[en] We analyse the effect of the separatrix shape on stochasticity onset and on diffusion in the two waves system, and in particular the role of the separatrix angle at the X-point. Introducing anharmonicity in the expression of the perturbation, we can adjust this angle, and eventually have it go to zero. We show that, in this latter case, stochasticity appears much sooner and that the diffusion coefficient is strongly enhanced. Applications to specific physical problems are discussed