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Author(s):
W.X. Wang, N. Nakajima, S. Murakami and M. Okamoto
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Title:
An Accurate delta f Method for Neoclassical Transport Calculation
Date of publication:
Mar. 1999
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Key words:
neoclassical transport,, drift kinetic equation, delta f algorithm, Monte Carlo collision operator
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Abstract:
A delta f method, solving drift kinetic equation, for neoclassical transport calculation is presented in detail. It is demonstrated that valid results essentially rely on the correct evaluation of marker density g in weight calculation. A general and accurate weighting scheme is developed without using some assumed g in weight equation for advancing particle weights, unlike the previous schemes. This scheme employs an additional weight function to directly solve g from its kinetic equation using the idea of delta f method. Therefore the severe constraint that the real marker distribution must be consistent with the initially assumed g during a simulation is relaxed. An improved like-particle collision scheme is presented. By performing compensation for momentum, energy and particle losses arising from numerical errors, the conservations of all the three quantities are greatly improved during collisions. Ion neoclassical transport due to self-collisions is examined under finite banana case as well as zero banana limit. A solution with zero particle and zero energy flux (in case of no temperature gradient) over whole poloidal section is obtained. With the improvement in both like-particle collision scheme and weighting scheme, the delta f simulation shows a significantly upgraded performance for neoclassical transport study.
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