Observation of Radially Inward Turbulent Particle Flux in ETG dominated Plasma of LVPD

TL;DR

This study reports the observation of radially inward turbulent particle flux driven by electron temperature gradient (ETG) turbulence in the core plasma of LVPD, with measurements aligning well with theoretical predictions.

Contribution

First experimental evidence of inward particle flux driven by ETG turbulence in a laboratory plasma, confirming theoretical models.

Findings

Inward electrostatic particle flux observed in ETG conditions

Flux magnitude is approximately 10^5 times larger than electromagnetic flux

Phase angle measurements agree with ETG turbulence theory

Abstract

Radially inward turbulent particle flux is observed in the core region of target plasma of Large Volume Plasma Device(LVPD). The region satisfy conditions for ETG turbulence, i.e. threshold condition, $ \eta_e = L_{n_e} / L_{T_e} > 2/3 $ , where density scale length, $ L_{n_e} \sim 300 cm $ and temerature scale length, $ L_{T_e} \sim 50cm $[S.K. Mattoo et al., Phys. Rev. Lett., 108, 255007(2012)\cite{Mattoo_PRL}]. The measured flux is dominantly electrostatic ($\Gamma_{es} \approx 10^{5} \Gamma_{em}$) although the nature of the measured turbulence is electromagnetic($\beta \approx 0.6 $). The turbulence has been established as a consequence of electron temperature gradient (ETG) driven modes. Experimental observations of phase angle between density ($ n_e $) and potential ($\phi $) fluctuations, $ \theta_{\tilde{n}_e, \tilde{\phi}} $ and electrostatic particle flux, $ \Gamma_{es} $ shows good agreement with the corresponding theoretical estimates for ETG turbulence.