THE EFFECT OF ELMS ON EDGE PLASMA SCALING IN DIII-D

In this paper we report results of scaling studies aimed at determining how the divertor conditions vary with plasma current, toroidal field, and neutral beam heating power in H-mode discharges with ELMs in the DIII-D tokamak. We find that ELMs produce relatively more direct particle losses (50% or more of the total) than energy losses (less-than-or-equal-to 20%). The time-average peak divertor heat flux in these plasmas is found to scale as q(d) is-proportional-to (P(NBI)I(p))(B(p,mp/B(p,div). The linear power dependence suggests that the plasma sheath at the targets is primarily responsible for limiting the parallel energy flow, while the I(p) variation may mean that the radial energy transport in the SOL decreases with increasing plasma current, just as it does in the core.