A finite element procedure for radio-frequency sheath–plasma interactions based on a sheath impedance model

Kohno, Haruhiko; Myra, J. R.

doi:10.1016/j.cpc.2017.06.025

Cited by 19 publications

(25 citation statements)

References 25 publications

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“…where Stangeby [26] has proved that the Debye sheath disappears. A more generalized form of the sheath RF impedance was proposed by Myra and D'Ippolito [29] and realized in the FEM code by Kohno and Myra [30] recently. It releases the "immobile ion" assumption and both the resistive and capacitive part of the RF sheath are retained in their new model.…”

Section: Rf Sheath Bcs Under Tilted Bmentioning

confidence: 99%

Modelling of radio frequency sheath and fast wave coupling on the realistic ion cyclotron resonant antenna surroundings and the outer wall

Lu¹,

Colas²,

Jacquot³

et al. 2018

Plasma Phys. Control. Fusion

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In order to model the sheath rectification in a realistic geometry over the size of Ion Cyclotron Resonant Heating (ICRH) antennas, the Self-consistent Sheaths and Waves for ICH (SSWICH) code couples self-consistently the RF wave propagation and the DC SOL biasing via non-linear RF and DC sheath boundary conditions (SBCs) applied at plasma/wall interfaces. A first version of SSWICH had 2D (toroidal and radial) geometry, rectangular walls either normal or parallel to the confinement magnetic field B0 and only included the evanescent slow wave (SW) excited parasitically by the ICRH antenna. The main wave for plasma heating, the fast wave (FW) plays no role on the sheath excitation in this version. A new version of the code, 2D SSWICH-Full Wave, was developed based on the COMSOL software, to accommodate full RF field polarization and shaped walls tilted with respect to B0. SSWICH-Full Wave simulations have shown the mode conversion of FW into SW occurring at the sharp corners where the boundary shape varies rapidly. It has also evidenced "far-field" sheath oscillations appearing at the shaped walls with a relatively long magnetic connection length to the antenna, that are only accessible to the propagating FW. Joint simulation, conducted by SSWICH-Full Wave within a multi-2D approach excited using the 3D wave coupling code (RAPLICASOL), has recovered the double-hump poloidal structure measured in the experimental temperature and potential maps when only the SW is modelled. The FW contribution on the potential poloidal structure seems to be affected by the 3D effects, which was ignored in the current stage. Finally, SSWICH-Full Wave simulation revealed the left-right asymmetry that has been observed extensively in the unbalanced strap feeding experiment s , suggesting that the spatial proximity effects in RF sheath excitation, studied for SW only previously, is st ill important in the vicinity of the wave launcher under full wave polarizations.

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Section: Rf Sheath Bcs Under Tilted Bmentioning

confidence: 99%

Modelling of radio frequency sheath and fast wave coupling on the realistic ion cyclotron resonant antenna surroundings and the outer wall

Lu¹,

Colas²,

Jacquot³

et al. 2018

Plasma Phys. Control. Fusion

View full text Add to dashboard Cite

show abstract

“…(14). Our previous published work 25 has verified the rfSOL solutions for various constant density cases. The main point of interest here is in understanding the interaction of the waves with the sheath boundary condition in rfSOL using the wave-sheath impedance model as exemplified in Fig.…”

Section: B Results From Rfsolmentioning

confidence: 67%

“…(A8), Re y w2 = Re y w1 , and from Eq. (A9), Im y w2 = Im y w1 or equivalentlyIn this Appendix, we prove the equivalence of Eqs (25). and(26), i.eexplicit result for y w1 is not needed.…”

mentioning

confidence: 70%

“…The rfSOL code is a finite element code that solves the electromagnetic cold fluid RF wave equations in flexible geometry. 25 A sample domain and solution are illustrated in Fig. 9.…”

Section: A Geometry and Code Setupmentioning

confidence: 99%

“…Quasi-conducting and intermediate limits are also possible, including that of the sheath-plasma resonance. [23][24][25] It is of interest to know a priori, based on plasma and wave parameters, when various limiting cases can be expected and how one might broadly characterize the wave interaction with an RF sheath over a range of these plasma and wave parameters. That is the goal of the present paper.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

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

Myra

Kohno

2019

Physics of Plasmas

Self Cite

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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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A finite element procedure for time-dependent radio-frequency sheaths based on a two-dimensional microscale fluid model

Kohno

Myra

2023

Computer Physics Communications

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A finite element procedure for radio-frequency sheath–plasma interactions based on a sheath impedance model

Cited by 19 publications

References 25 publications

Modelling of radio frequency sheath and fast wave coupling on the realistic ion cyclotron resonant antenna surroundings and the outer wall

Modelling of radio frequency sheath and fast wave coupling on the realistic ion cyclotron resonant antenna surroundings and the outer wall

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

A finite element procedure for time-dependent radio-frequency sheaths based on a two-dimensional microscale fluid model

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