Electron temperature gradient turbulence induced energy flux in the large volume plasma device

Abstract

The Large Volume Plasma Device (LVPD) has successfully demonstrated excitation of the Electron Temperature Gradient (ETG) driven turbulence in the finite plasma beta (β∼0.06−0.4) condition, where the threshold condition for ETG turbulence is, ηETG=Ln/LT>2/3 satisfied, where, Ln=1ndndx−1 is the density scale length and LTe=1TedTedx−1 is the temperature scale lengths [Mattoo et al., Phys. Rev. Lett. 108, 255007 (2012)]. The observed mode follows wave vector scaling and frequency ordering as k⊥ρe≤1 ≪ k⊥ρi, Ωi<ω ≪ Ωe, where k⊥ is the perpendicular wave vector, ρe, ρi are Larmor radii of the electron and ion, respectively, and Ωi, Ωe, ω are the ion, electron gyro frequencies and the mode frequency, respectively. Simultaneous measurement of fluctuations in electron temperature, δTe ∼ (10−30) %, plasma density, δne ∼ (5−12) %, and potential δVf ∼ (1−10) % are obtained. A strong negative correlation with correlation coefficients Cδn−δφ ∼−0.8 and CδT−δφ ∼−0.9 is observed between the density and potential and temperature and potential fluctuations, respectively. These correlated density, temperature, and potential fluctuations lead to the generation of turbulent heat flux. The measured heat flux is compared with the theoretically estimated heat flux from ETG model equations. The experimental result shows that the net heat flux is directed radially outward.