The total heat flux q arising in steady state from Ohmic and neutral beam heating is calculated for a series of power scan experiments on JET. A radial resolution of q at selected radii is made to examine the dependence of q upon local plasma parameters such as density ne, temperature Te, current I and their gradients. Non-linear regression analysis techniques are applied to fit the data on q to empirical expressions qfit, involving the local plasma parameters. The most plausible fit emerging from the analysis is qfit = − (C/I)ne ∇Te− qpinch, in which C is a constant, I the current enclosed by a plasma surface and qpinch a constant so-called heat pinch. The net heat diffusivity inferred from this relationship agrees with estimates from heat pulse propagation measurements and it leads to a scaling law for the incremental energy confinement time which agrees with the one determined experimentally. There is a substantial amount of scatter in the data due to approximations made in the analysis and due to uncertainties in the experimental measurements.
Resistive versus ideal plasma response to RMP fields in DIII-D: roles of q95 and X-point geometry