Experimental Observation of Convective Cell Formation due to a Fast Wave Antenna in the Large Plasma Device

Martin, M. J.; Gekelman, Walter; Compernolle, B. Van; Pribyl, Patrick; Carter, T.

doi:10.1103/physrevlett.119.205002

Cited by 23 publications

(44 citation statements)

References 25 publications

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“…Thermionic electrons are emitted from plasma-facing surfaces in many systems. Important examples include tokamak divertors [1], hypersonic vehicles [2], dusty plasmas [3], emissive probes [4,5], the Large Plasma Device [6], thermionic discharges [7], and arcs [8]. Emission alters the sheath potential and energy balance, thereby affecting the interior plasma properties [9].…”

mentioning

confidence: 99%

Thermionic Cooling of the Target Plasma to a Sub-eV Temperature

Campanell

Johnson

2019

Phys. Rev. Lett.

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Contemporary models of bounded plasmas assume that the target plasma electron temperature far exceeds the temperature of the cold electrons emitted from the target, Temit. We show that when the sheath facing a collisional plasma becomes inverted, the target plasma electron temperature has to equal Temit even if the upstream plasma is hotter by orders of magnitude. This extreme cooling effect can alter the plasma properties and the heat transmission to thermionically emitting surfaces in many applications. It also opens a possibility of using thermionic divertor plates to induce detachment in tokamaks.

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confidence: 99%

Thermionic Cooling of the Target Plasma to a Sub-eV Temperature

Campanell

Johnson

2019

Phys. Rev. Lett.

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“…RF-driven convection in lower-hybrid (LH) experiments was also observed in Alcator C-Mod especially on field lines that were magnetically connected to the LH launcher (Lau et al 2013). ICRF-driven convective cells were also observed in the linear LAPD device (Martin et al 2017).…”

Section: Rf-driven Convectionmentioning

confidence: 91%

A tutorial on radio frequency sheath physics for magnetically confined fusion devices

Myra

2021

J. Plasma Phys.

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Radio frequency (RF) sheaths occur under a wide variety of conditions when RF waves, material surfaces and plasma coexist. RF sheaths are of special importance in describing the interaction of ion cyclotron range of frequency (ICRF) waves with the boundary plasma in tokamaks, stellarators and other magnetic confinement devices. In this article the basic physics of RF sheaths is discussed in the context of magnetic fusion research. Techniques for modelling RF sheaths, their interaction with RF wave fields and the resulting consequences are highlighted. The article is intended as a guide for the early-career ICRF researcher, but it may equally well serve to provide an overview of basic RF sheath concepts and modelling directions for any interested fusion scientist.

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“…To proceed further we introduce the dielectric tensor (12) which yields the admittance of a plane wave with wave-vector k in the present geometry as…”

Section:  mentioning

confidence: 99%

“…[1,2]. They have also been investigated in recent experiments on many tokamaks, [3][4][5][6][7][8][9][10] and linear test stands 11,12 and they have been the subject of a number of dedicated modeling efforts. [13][14][15][16][17][18][19][20] Since RF sheaths are thought to play a central role in understanding the observations, developing models for sheaths and their interaction with RF waves is an important aspect of the work and is the subject of the present paper.…”

Section: Introductionmentioning

confidence: 99%

Radio frequency wave interactions with a plasma sheath: The role of wave and plasma sheath impedances

Myra

Kohno

2019

Physics of Plasmas

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Radio frequency (RF) sheaths form near surfaces where plasma and strong RF fields coexist. The effect of these RF sheaths on wave propagation near the boundary can be characterized by an effective sheath impedance that includes both resistive and capacitive contributions describing RF sheath rectification and RF power absorption in the sheath [J. R. Myra and D. A. D'Ippolito, Phys. Plasmas 22, 062507 (2015)]. Here we define a dimensionless parameter, the ratio of incoming wave impedance to the sheath impedance, which determines the characteristics of the interaction, ranging from quasi-conducting to quasi-insulating, or in the case of matched impedances, to either perfect absorption or a sheath-plasma resonance. A semianalytical analysis is carried out for electrostatic slow waves in the ion cyclotron range of frequencies (ICRF). For the propagating slow wave case, where the incident wave is partially reflected, the fraction of power dissipated in the sheath is calculated. For the evanescent slow wave case, which admits a sheath-plasma resonance, an amplification factor is calculated. Using the impedance ratio approach, RF sheath interactions are characterized for a range of RF wave and plasma parameters including plasma density, magnetic field angle with respect to the surface, wave frequency and wave-vector components tangent to the surface. For a particularly interesting example case, results are compared with the rfSOL code [H. Kohno and J. R. Myra, Comput. Phys. Commun. 220, 129 (2017)]. Finally electromagnetic effects, absent from the semi-analytical analysis, are assessed.

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Experimental Observation of Convective Cell Formation due to a Fast Wave Antenna in the Large Plasma Device

Cited by 23 publications

References 25 publications

Thermionic Cooling of the Target Plasma to a Sub-eV Temperature

Thermionic Cooling of the Target Plasma to a Sub-eV Temperature

A tutorial on radio frequency sheath physics for magnetically confined fusion devices

Radio frequency wave interactions with a plasma sheath: The role of wave and plasma sheath impedances

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