Sensitivity of Divertor Operating Conditions on Plasma Parameters in a Next Step Device

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Abstract
Divertor power loads and electron temperatures, obtained numerically using the Braams Plasma Edge Code, B2, are reported and interpreted for the parameter range of a Next Step device. A guideline for terminating a B2 run is proposed: the power balance should follow a ‘strict’ exponential decay when the plasma is approaching its final state. Evidence is presented that erroneous solutions can be obtained if this is not the case. A comparison of results for imposed core density (at fixed plate porosity) and imposed core particle flux (with plate porosity adjusted to match this flux) is made. It is found that external pumping has no effect as long as the flux removed at the divertor plate stays in the range of a few tenths of a percent. We document the effect of an adhoc fluxlimiter. It is shown that similar ‘low’ plasma temperatures can be obtained without a flux limiter, by a small increase of the upstream density, and that the scaling relations are unaffected.

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