1D SIMULATION OF SAWTOOTH CRASH BASED ON TRANSPORT BIFURCATION

The crash of the temperature profile associated with a propagating tra nsport bifurcation between the L-mode and the magnetic braiding mode ( M-mode) in a tokamak plasma is presented. The magnetic braiding mode i s induced by the magnetic stochasticity. If the pressure gradient exce eds a threshold value a magnetic stochasticity sets in and the heat co nductivity is much enhanced (M-mode). The hack transition to the L-mod e occurs when the pressure gradient decreases to another threshold val ue. The model of the transport bifurcation is included in the 1D trans port code. The crash of the temperature profile and the propagation of the crash front (avalanche) are realized by this model. The collapse without a precursor oscillation is revealed.