26th IAEA Fusion Energy Conference - IAEA CN-234

Parallel Momentum Transport Induced by RF Waves and by Plasma Turbulence

19 Oct 2016, 14:00

4h 45m

Kyoto International Conference Center

Poster THW - Magnetic Confinement Theory and Modelling: Wave–plasma interactions; current drive; heating; energetic particles Poster 4

Speaker

Prof. Zhe Gao (Tsinghua University)

Description

Generation of plasma toroidal flow without or with low momentum input has been attracted much attention due to the key issue of plasma rotation on MHD stabilization and turbulence regulation. The general momentum equation is reached with a generalized ponderomotive force and then the drive and transport of parallel momentum are discussed in the case of rf injection and/or in the drift-wave turbulence background. With the injection of rf waves, a generalized ponderomotive force exerts on the plasma, which includes three parts. Firstly, the inhomogeneity of rf field results in the conventional ponderomotive force, which is nonresonant, but only in the direction of the inhomogeneity. Secondly, the wave-particle resonant interaction produces a dissipative drive force (DDF), in which the wave deposits the momentum on resonant particles like the well-known process of photon absorption. Thirdly, the inhomogeneity of resonant wave-particle interaction can induce a resonant momentum redistribution, which is called resonant ponderomotive force (RPF). The DDF and its induced radial flux can be used to explain the flow drive during the injection of low hybrid waves; while the parallel RPF might be responsible to the strong rotation in the experiment of the ion-cyclotron-frequency mode-conversion flow drive. The inhomogeneity of plasma profile can be integrated in the theory. For rf-driven case, this only contributes an additional factor in the local energy absorption rate without changing the expressions and the physical pictures of the rf forces. However, the theory can also be applied to study the momentum transport in turbulence background. By re-arranging the terms, it is found that the residual stress is indeed the pinch effect of parallel resonant velocity. The ion parallel momentum source term is the resonant parallel momentum transfer rate between resonant ions and waves. Then the conservation of the parallel momentum of resonant ions and waves is clearly presented. This work is supported by NSFC, under Grant Nos. 11325524 and 11261140327, and MOST of China, under Contract Nos. 2013GB112001.