Survey of Electron Heat Diffusion Driven by Sawtooth Crashes in J-TEXT Tokamak*

A soft X-ray diagnostic system has been established on the J-TEXT tokamak aiming to observe and survey the MHD activities, in particular, sawtooth behavior. The system consists of 8 cameras stretching to 128 collimated viewing chords which can cover the cross section of the tokamak. Investigation and analysis of the propagation of heat-pulses due to sawtooth crashes can provide the possibility to evaluate the electron heat diffusivity $\chi _{ep}$. The value deduced by heat pulse measurements on J-TEXT tokamak is about 7$\sim $18 m$^{2}$/s, 4 $\sim $ 9 times of $\chi _{e}$ ($\approx $2 m$^{2}$/s) which is predicted by power balance calculations. By applying externally resonant magnetic perturbations (RMPs), it is found that $\chi _{ep}$ is lower than that value without RMPs. More experimental results and the analysis will be presented in the meeting.