Investigations on ETG turbulence in finite beta plasmas of LVPD

Abstract

This paper presents the first controlled observations on electron temperature gradient (ETG) driven turbulence in finite beta (β ∼ 0.6) plasmas of the Large Volume Plasma Device (LVPD). The observed instability is investigated in the core region of the target plasma when a ∼ 2 m diameter magnetic electron energy filter is used. The observed instability in the lower hybrid range of frequencies has electromagnetic fluctuations associated with it and is characterized by broadband spectra with central frequency, ν 10 kHz, and wave number, k ⊥ = (0.1-0.2) cm −1 , which satisfies the condition k ⊥ ρ e 1 where ρ e is the electron Larmor radius. It is also observed that the observed mode satisfies the condition, k /k ⊥ 1. A confirmation of it as ETG turbulence is demonstrated by its absence when ∇T e is made vanishingly small.

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

“…We carried out investigations for confirming performance of EEF for producing a Maxwellian plasma by validating the relationship φ p = φ f + 5.4T e in the target region of LVPD plasma. A detailed characterization of the plasma in the presence of EEF was reported by Sushil et al 16 , where it was shown that various scale lengths of density (n e ) and electron temperature(T e ) are possible by suitably configuring various elements of EEF.…”

From Electrojet to ITER: India's Journey in Experimental Plasma Physics

“…The most recent observation is that of electron temperature gradient (ETG) driven turbulence in the laboratory plasma [31]. Removal of unutilized primary ionizing and non-thermal electrons from uniform density plasma and imposition and control of gradient in electron temperature are all achieved by placing a large (2m, diameter) magnetic Electron Energy Filter (EEF) in the middle of the device.…”

The study of the transition regime between slab and mixed slab-toroidal electron temperature gradient modes in a basic experiment

“…10-17. And although there was some debate over some of the early results, 10,14 the controversy within the simulation community appears to have been resolved. 15 Experimentally, direct observations of ETG are complicated due to the small spatial scales and fast time scales that characterize ETG turbulence, but in recent years several observations of ETG have been made in basic plasma experiments [18][19][20][21] and tokamaks. [22][23][24][25] Prior work in Columbia Linear Machine (CLM) was able to create and positively identify ETG modes, 18 and numerical validation was done quickly thereafter 26 using the previously developed Gyrokinetic Toroidal Code (GTC).…”