Neutral diffusion and anomalous effects on collisional ion flow shear in tokamaks

Neutral diffusion and anomalous effects on collisional ion flow shear in tokamaks

Neutral diffusion and anomalous effects on collisional ion flow shear in tokamaks 150 150 Mathew

Neutral diffusion and anomalous effects on collisional ion flow shear in tokamaks

Ion plasma flow and flow shear just inside the last closed flux surface of a tokamak can be strongly altered by neutral atoms and anomalous effects. For a collisional edge, neutrals modify the standard Pfirsch–Schluter expression for the parallel ion flow through the strong coupling provided by ion–neutral collisions. Even for rather small neutral to plasma density ratios, the large diffusivity of the neutrals in combination with the ion–neutral coupling can directly modify the ion distribution function as well as cause neutral diffusion modifications to the parallel momentum constraint that determines the parallel ion flow. Direct modification of the ion distribution function only dominates at order unity aspect ratios, and was unimportant in an earlier plateau evaluation of the effects of neutrals on ion flow. Like the earlier work, anomalous effects are retained to maintain a steady state and demonstrate that large anomalous transport can alter neoclassical collisional ion flows.

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01/11/1998