Bursting modes in the frequency range of the toroidicityinduced Alfvén eigenmode are observed in the plasma to which the negative-ion-based neutral beam (N-NB) is injected. A bursting mode changes its frequency by 10-20 kHz in 1-5 ms and is called fast frequency sweeping (fast FS) mode. Another bursting mode evolves explosively in ⩽400 µs and is called an abrupt large-amplitude event. The dependence of their saturation level was compared with the experimentally observed growth rate and damping rate. The mode amplitude increases with the observed growth rate for fast FS modes. The modes with large amplitude and a large enhanced transport were observed when a large neutron emission rate was observed. The burst period increases as the drop ratio of the neutron emission increases.
Recent experiments on Alfvén eigenmodes in MAST