Observation of radially inward turbulent particle flux in ETG dominated plasma of LVPD

Abstract

Radially inward turbulent particle flux is observed in the core region of target plasma of Large Volume Plasma Device where electron temperature gradient (ETG) driven turbulence conditions are satisfied with threshold, ηETG=Ln/LT>2/3 [Mattoo et al., Phys. Rev. Lett. 108, 255007 (2012)]. The observed mode satisfies the scale length and frequency ordering of ETG (k⊥ρe≤1≪k⊥ρi,Ωi<ω≪Ωe), where k⊥ is the perpendicular wave vector, ρe ,ρi are Larmor radii of electron and ion, respectively, and Ωi,Ωe, and ω are the ion, electron gyro frequencies, and the mode frequency, respectively. The measured flux is dominantly electrostatic (Γes≈105Γem), although the nature of the turbulence is electromagnetic (β∼0.1−0.6). Experimental observations of the phase angle between density and potential fluctuations, θñ,ϕ̃, and turbulent particle flux, Γes, shows good agreement with the theoretical estimations derived for ETG turbulence.