Journal Article Turbulence simulation taking account of inhomogeneity of neutral density in linear devices

Kasuya, N.  ,  Abe, S.  ,  Sasaki, M.  ,  S.Inagaki  ,  Kobayashi, T.  ,  Yagi, M.

25pp.012314-1 - 012314-11 , 2018-03 , the American Institute of Physics
Description
It is important to consider a combination of inhomogeneities, which drive and/or damp instabilitiesin magnetized plasmas. The inhomogeneity of neutral particle density is taken into account foranalyzing turbulent states in linear devices by combining two kinds of simulations in this research.One is a simulation for 2D profiles of neutral particles and the other is that for resistive drift waveturbulence. Radial and axial profiles of neutral particles are calculated by the Monte Carlo methodwith a configuration of linear device PANTA. The ratio for ionization of neutral particles dependson the electron temperature, and the higher temperature in the operation range makes the neutraldensity smaller near the center of the plasma. Then, the radial profile of the ion-neutral collisionfrequency is set by introducing these neutral density profiles into resistive drift wave turbulencesimulations. Smaller ion-neutral collision frequency makes the instabilities more unstable, and itsinhomogeneity enhances mean electrostatic potential formation. The eigenmode structure ischanged with the inhomogeneous ion-neutral collision frequency, and convective derivative nonlinearitygenerates the azimuthal flow near the center of the plasma. Two roles of the neutral particleson the turbulence, the direct change in linear instabilities and formation of background flows,become clear.

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