Radial current and rotation profile tailoring in highly ionized linear plasma devices

Kolmes, Elijah; Ochs, Ian E.; Mlodik, M. E.; Rax, Jean-Marcel; Gueroult, Renaud; Fisch, Nathaniel J.

doi:10.1063/1.5115788

Cited by 25 publications

(32 citation statements)

References 39 publications

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“…In a non-neutral plasma the electric field is the space charge field (Davidson 2001). On the other hand, the electric field in a quasi-neutral plasma requires in steady-state maintaining a small uniform space charge , and a DC or RF power input is thus needed to maintain this small deviation from quasi-neutrality against short circuiting radial currents (Kolmes et al 2019; Rax et al 2019).…”

Section: Brillouin Rotation Of a Magnetised Plasma Columnmentioning

confidence: 99%

Faraday–Fresnel rotation and splitting of orbital angular momentum carrying waves in a rotating plasma

Rax

Gueroult

2021

J. Plasma Phys.

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Rotational Fresnel drag – or orbital Faraday rotation – in a rotating magnetised plasma is uncovered and studied analytically for Trivelpiece–Gould and whistler–helicon waves carrying orbital angular momentum (OAM). Plasma rotation is shown to introduce a non-zero phase shift between OAM-carrying eigenmodes with opposite helicities, similarly to the phase shift between spin angular momentum eigenmodes associated with the classical Faraday effect in a magnetised plasma at rest. By examining the dispersion relation for these two low-frequency modes in a Brillouin rotating plasma, this Faraday–Fresnel rotation effect is traced back to the combined effects of Doppler shift, centrifugal forces and Coriolis forces. In addition, the longitudinal group velocity in the presence of rotation is shown to depend both on rotation and azimuthal mode, therefore predicting the Faraday–Fresnel splitting of the envelope of a wave packet containing a superposition of OAM-carrying eigenmodes with opposite helicities.

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Section: Brillouin Rotation Of a Magnetised Plasma Columnmentioning

confidence: 99%

Faraday–Fresnel rotation and splitting of orbital angular momentum carrying waves in a rotating plasma

Rax

Gueroult

2021

J. Plasma Phys.

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“…In a rotating plasma an additional contribution to perpendicular conductivity stems from inertia 50,51 . For a fully ionized plasma with limited shear, it writes 51…”

Section: B Contribution Of Inertia In Rotating Plasmasmentioning

confidence: 99%

A necessary condition for perpendicular electric field control in magnetized plasmas

2019

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The electrostatic model proposed by Poulos [Phys. Plasmas (2019), 26, 022104] to describe the electric potential distribution across and along a magnetized plasma column is used to shed light onto the ability to control perpendicular electric fields. The effective electrical connection between facing end-electrodes is shown to be conditioned upon the smallness of a dimensionless parameter τ function of the plasma column aspect ratio and the square root of the conductivity ratio σ ⊥ /σ . The analysis of a selected set of past end-electrodes biasing experiments confirms that this parameter is small in experiments that have successfully demonstrated perpendicular electric field tailoring. On the other hand, this parameter is O(1) in experiments that failed to demonstrate control, pointing to an excessively large ion-neutral collision frequency. A better understanding of the various contributions to σ ⊥ is needed to gain further insights into end-biasing experimental results.

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“…However, this charge transport is ordered down by 2 relative to the motion of each individual charge, where ∼ ρ i /L, with ρ i the gyroradius and L the characteristic scale length of the electric field variation. This scaling leads to cross field-currents consistent with the Braginskii perpendicular viscosity 59,66 and collisional gyrokinetics 67,68 , and can be seen as a Larmor-radius-scale random walk of momentum.…”

Section: A a Note On Viscositymentioning

confidence: 64%

“…We begin in Section II by reviewing the deep link between momentum conservation and charge transport in a magnetized plasma 58,59 . To eliminate confounding processes that might muddy the subsequent analysis, we work in the simplest possible magnetic geometry: a slab with a uniform magnetic field.…”

Section: Figmentioning

confidence: 99%

Momentum Conservation in Current Drive and Alpha-Channeling-Mediated Rotation Drive

Ochs,

Fisch

2022

Preprint

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Alpha channeling uses waves to extract hot ash from a fusion plasma, while transferring energy from the ash to the wave. Intriguingly, it has been proposed that the extraction of this charged ash could create a radial electric field, efficiently driving E × B rotation. However, existing theories ignore the response of the nonresonant particles, which play a critical role in enforcing momentum conservation in quasilinear theory. Because cross-field charge transport and momentum conservation are fundamentally linked, this non-consistency throws the whole effect into question.Here, we review recent developments that have largely resolved this question of rotation drive by alpha channeling. We build a simple, general, self-consistent quasilinear theory for electrostatic waves, applicable to classic examples such as the bump-on-tail instability. As an immediate consequence, we show how waves can drive currents in the absence of momentum injection even in a collisionless plasma. To apply this theory to the problem of ash extraction and rotation drive, we develop the first linear theory able to capture the alpha channeling process. The resulting momentum-conserving linear-quasilinear theory reveals a fundamental difference between the reaction of nonresonant particles to plane waves that grow in time, versus steady-state waves that have nonuniform spatial structure, allowing rotation drive in the latter case while precluding it in the former. This difference can be understood through two conservation laws, which demonstrate the local and global momentum conservation of the theory. Finally, we show how the oscillation-center theories often obscure the time-dependent nonresonant recoil, but ultimately lead to similar results. I. BACKGROUND AND INTRODUCTION

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Radial current and rotation profile tailoring in highly ionized linear plasma devices

Cited by 25 publications

References 39 publications

Faraday–Fresnel rotation and splitting of orbital angular momentum carrying waves in a rotating plasma

Faraday–Fresnel rotation and splitting of orbital angular momentum carrying waves in a rotating plasma

A necessary condition for perpendicular electric field control in magnetized plasmas

Momentum Conservation in Current Drive and Alpha-Channeling-Mediated Rotation Drive

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