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

Srivastav, Prabhakar; Singh, Rameswar; Awasthi, L. M.; Sanyasi, A. K.; Srivastava, P. K.; Sugandhi, R.; Kaw, P. K.

doi:10.1063/1.5012093

Cited by 8 publications

(11 citation statements)

References 35 publications

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“…Now recall the expression for electrostatic electron flux from Ref [8]. In figure 11, we have made an attempt to estimate the experimentally observed particle flux due to electron and ion parallel motion, It was observed that the average electron and ion flux contribution differ significantly.…”

Section: A Quasilinear Theory For Electromagnetic Particle Fluxmentioning

confidence: 99%

“…In figure 12, the electromagnetic fluctuations driven radial electron flux is measured during the steady state period between (6)(7)(8)…”

Section: B Radial Profiles Of Ion and Electron Fluxes And Comparisonmentioning

confidence: 99%

“…The radial electromagnetic flux forms from correlation between parallel current, of charge species, and radial magnetic field fluctuations, . Although significant advancement in developing an understanding is achieved as far as electrostatic flux contribution is concerned [4][5][6][7][8] the electromagnetic fluctuations driven radial flux is still not completely explored. Although, the electromagnetic particle flux has been reported from many devices, namely, the tokamaks [9,10] , the stellerator [11] and reversed field pinch [12][13][14] etc.…”

Section: ̃ ̃mentioning

confidence: 99%

“…Poloidal derivative of poloidally averaged quantity is zero. So eventually the expression for flux becomes(8)…”

mentioning

confidence: 99%

“…The electrostatic particle flux ( ) and radial velocity (v x ) fluctuations. The velocity fluctuations are estimated from the cross product of fluctuating poloidal electric field ( y E  ) and ambient magnetic field, EB, where E is estimated from the floating potential fluctuations measured by a pair of poloidally separated Langmuir probes[8]. The electromagnetic flux derived from q" is the charge, is observed to be but is finite.…”

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confidence: 99%

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Observation of electromagnetic fluctuation induced particle transport in ETG dominated large laboratory plasma

Srivastav

Singh

Awasthi

et al. 2019

Plasma Phys. Control. Fusion

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The Large Volume Plasma device(LVPD), a cylindrically shaped, linear plasma device of dimension( m L m 3 , 2    ) have successfully demonstrated the excitation of Electron Temperature Gradient(ETG) turbulence[ Mattoo et al.,[1]]. The observed ETG turbulence shows significant power between ( ) ( ), corresponding to the wavenumber, ~ ( ) where, and ( ) ion cyclotron frequency and electron Larmor radius, respectively. The observed frequency and wave number matches well with theoretical estimates corresponding to Whistler-ETG mode. We investigated electromagnetic (EM) fluctuations induced plasma transport in high beta ( 2 2 /~0.01 0.4 oe nT B   ) ETG mode suitable plasma in LVPD. The radial electromagnetic (EM) electron (ion) flux () results primarily from the correlation between fluctuations of parallel electron current ( ) and radial magnetic field ( ). The electromagnetic particle flux is observed to be much smaller than the electrostatic particle flux, .The EM flux is small but finite contrary to the conventional slab ETG model. The electromagnetic flux is non-ambipolar. A theoretical model is obtained for the EM particle flux in straight homogeneous magnetic field geometry. The theoretical estimates are seen to compare well with the experimental observations. Sluggish parallel ion response is identified as the key mechanism for generation of small but finite electromagnetic flux.2

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Section: A Quasilinear Theory For Electromagnetic Particle Fluxmentioning

confidence: 99%

“…In figure 12, the electromagnetic fluctuations driven radial electron flux is measured during the steady state period between (6)(7)(8)…”

Section: B Radial Profiles Of Ion and Electron Fluxes And Comparisonmentioning

confidence: 99%

Section: ̃ ̃mentioning

confidence: 99%

“…Poloidal derivative of poloidally averaged quantity is zero. So eventually the expression for flux becomes(8)…”

mentioning

confidence: 99%

mentioning

confidence: 99%

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Observation of electromagnetic fluctuation induced particle transport in ETG dominated large laboratory plasma

Srivastav

Singh

Awasthi

et al. 2019

Plasma Phys. Control. Fusion

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Turbulence and transport by electron temperature gradient driven instability in large volume plasma device

Awasthi,

Srivastav,

Singh

et al. 2024

Rev. Mod. Plasma Phys.

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We present a topical review of the detailed experimental investigations of the Electron Temperature Gradient (ETG) instability-induced turbulence and associated transport that have been carried out in the Large Volume Plasma Device (LVPD) at the Institute for Plasma Research. These results pertaining to a high beta plasma are supported by theoretical modeling and their significance with relation to earlier ETG investigations are discussed. The removal of non-thermal electrons and control of electron temperature gradient, $$\nabla {T}_{e}$$ ∇ T e are achieved in a finite beta plasma (β ∼ 0.6) by making use of an Electron Energy Filter (EEF). It divides the plasma into source, EEF and target regions. In the core region ($$x\le 50$$ x ≤ 50 cm) of target plasma, the observed electromagnetic instability exhibits fluctuations in the lower hybrid range of frequencies ($$f=1-80 kHz$$ f = 1 - 80 k H z ), with a broad band spectra having its peak power at wave number, $${k}_{\perp }=\left(0.1-0.2\right)$$ k ⊥ = 0.1 - 0.2 cm−1 and frequency, f ~ 10 kHz satisfying condition $${k}_{\perp }{\rho }_{e}\le 1$$ k ⊥ ρ e ≤ 1 and $${k}_{\parallel }/{k}_{\perp }<$$ k ‖ / k ⊥ < 1, where $${\rho }_{e}$$ ρ e is the electron Larmor radius and $${k}_{\perp }$$ k ⊥ and $${k}_{\parallel }$$ k ‖ are the perpendicular and parallel wave numbers, respectively. It was demonstrated successfully that when $$\nabla {T}_{e}$$ ∇ T e is made significant such that$${\eta }_{e}\approx {L}_{n}/{L}_{Te}>2/3$$ η e ≈ L n / L Te > 2 / 3 , where $${L}_{n}$$ L n is density scale length and $${L}_{Te}$$ L Te is electron temperature scale length, the ETG scale turbulence gets excited in the presence of pre-excited Whistler mode. A linear theory of coupled Whistler-Electron Temperature Gradient (W-ETG) mode is developed using a two-fluid model applicable for the LVPD plasma. A comparison of the experimental and numerical results is found to be in good agreement. Upon identification of the ETG turbulence, the electrostatic and electromagnetic particle fluxes and energy flux induced by it in the target region of LVPD were investigated. We observed an inward directed radial particle flux, but total heat flux remained radially outward. The particle and thermal fluxes are compared with the numerically obtained values and are found to be in good agreement in the core plasma of LVPD.

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

et al. 2019

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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.

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

Cited by 8 publications

References 35 publications

Observation of electromagnetic fluctuation induced particle transport in ETG dominated large laboratory plasma

Observation of electromagnetic fluctuation induced particle transport in ETG dominated large laboratory plasma

Turbulence and transport by electron temperature gradient driven instability in large volume plasma device

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

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