Simultaneous analysis of ECH modulation and sawtooth activity in the plasma core of the RTP tokamak

A model for the interaction between the sawtooth instability (ST) and modulated electron cyclotron heating (MECH) is presented and tested against electron temperature measurements in RTP tokamak plasmas. The simultaneous analysis of the ECH and ST induced heat waves, including the effect of their interaction, allows the extension of the determination of the incremental electron diffusivity (chi(inc)) to the plasma core region. The experimental data can be interpreted, in the typical range of frequencies of the RTP experiment (300-1500 Hz), in terms of a perturbed heat flux with a low (less than or similar to 0.3 m(2)/s) chi(inc) value inside the sawtoothing region and a larger (approximate to 5-6 m(2)/s) chi(inc) value outside with a sharp transition. A non-adiabatic sawtooth crash model provides a better fit to the RTP sawtooth heat pulse data than does an adiabatic crash model.