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

The Large Volume Plasma Device (LVPD) has successfully demonstrated excitation of the Electron Temperature Gradient (ETG) driven turbulence in the finite plasma beta (beta similar to 0.06 - 0.4) condition, where the threshold condition for ETG turbulence is, eta(ETG) = L-n/L-T > 2/3 satisfied, where, L-n = [1/n dn/dx](-1) is the density scale length and L-Te = [1/T-e dT(e)/dx](-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(perpendicular to) rho(e) <= 1 << k(perpendicular to) rho(i), Omega(i) < omega << Omega(e), where k(perpendicular to) is the perpendicular wave vector, rho(e), rho(i) are Larmor radii of the electron and ion, respectively, and Omega(i), Omega e, omega are the ion, electron gyro frequencies and the mode frequency, respectively. Simultaneous measurement of fluctuations in electron temperature, delta T-e similar to (10 - 30) %, plasma density, delta n(e) similar to (5 - 12) %, and potential delta V-f similar to (1 - 10)% are obtained. A strong negative correlation with correlation coefficients C delta n-delta phi similar to -0.8 and C delta T-delta phi similar to -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. Published under license by AIP Publishing.