Nonlinear double tearing mode in negative shear cylindrical tokamaks

For negative shear cylindrical tokamaks, nonlinear behavior of double tearing modes (DTMs) with (m, n)=(3, 1), (2, 1) and (1, 1) has been studied for 0.90.4, γ ∝ S-3/5, and transition behavior is seen for 0.1<Δr<0.4. It is noted that nonlinear destabilization of DTM is seen for this case, which means that DTM produces a completely flat q-profile or a full reconnection within the external resonant surface, although γ ∝ S-3/5 roughly in the linear phase. Generally the lower m mode generates the full reconnection for the wider distance between the two resonant surfaces. (author)