Mode structure of disruption precursors in TFTR enhanced reversed shear discharges

The mode structure of the disruption precursors in the TFTR enhanced reversed shear parameters has been studied by using T e uctuation proles and q proles obtained from Electron Cyclotron Emission(ECE) and Motional Stark Eect(MSE) measurements.The observed proles of the radial displacement associated with the MHD modes were consistent with the displacement proles expected from the ideal MHD external kink mode.The observed mode frequencies dier from the plasma toroidal rotation frequency measured with CVI charge-exchange recombination light.The independence of the mode frequency from the plasma rotation frequency supports the ideal MHD hypothesis.Possible causes of the frequency dierence are discussed.