Why the thermal diffusivity increases with plasma collisionality when the experimental profiles are used but not in the independent tests wih the transport model?
It is found that the safety factor q profile and the magnetic shear s profile can change the dependence. When the q and s profiles for the NSTX discharge 141031 are replaced with the corresponding profiles for the discharge 141040, the experimental dependence is partially recovered. The electron thermal diffusivity profiles on the figure below that is marked as hybrid31c is generated using the Weiland model in MMM8.1 with the plasma profiles for the discharge 141031 with the exception of the q and s profiles that are taken from the discharge 141040.
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