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Report No.

Dynamics of enhanced neoclassical particle transport of tracer impurity ions in ion temperature gradient driven turbulence

Idomura, Yasuhiro  ; Obrejan, K.*; Asahi, Yuichi  ; Honda, Mitsuru*

Tracer impurity transport in ion temperature gradient driven (ITG) turbulence is investigated using a global full-$$f$$ gyrokinetic simulation including kinetic electrons, bulk ions, and low to medium $$Z$$ tracer impurities, where $$Z$$ is the charge number. It is found that in addition to turbulent particle transport, enhanced neoclassical particle transport due to a new synergy effect between turbulent and neoclassical transports makes a significant contribution to tracer impurity transport. Bursty excitation of the ITG mode generates non-ambipolar turbulent particle fluxes of electrons and bulk ions, leading to a fast growth of the radial electric field following the ambipolar condition. The divergence of $$Etimes B$$ flows compresses up-down asymmetric density perturbations, which are subject to transport induced by the magnetic drift. The enhanced neoclassical particle transport depends on the ion mass, because the magnitude of up-down asymmetric density perturbation is determined by a competition between the $$Etimes B$$ compression effect and the return current given by the parallel streaming motion. This mechanism does not work for the temperature, and thus, selectively enhances only particle transport.



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Category:Physics, Fluids & Plasmas



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