Self consistent radio-frequency wave propagation and peripheral direct current plasma biasing: Simplified three dimensional non-linear treatment in the “wide sheath” asymptotic regime

Colas, L.; Jacquot, Jean-Pierre; Heuraux, Stéphane; Faudot, Eric; Crombé, Kristel; Kyrytsya, V.; Hillairet, Julien; Goniche, M.

doi:10.1063/1.4750046

Cited by 53 publications

(49 citation statements)

References 45 publications

(83 reference statements)

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“…perpendicular terms in the laplacian, and ω 0 is the antenna frequency. In SSWICH-SW's asymptotic mode [8], which we use in this paper, the boundary condition at the limiter surfaces is E = 0.…”

Section: Sswich-swmentioning

confidence: 99%

“…The SSWICH-SW code [7][8][9] self-consistently determines the nonlinear plasma sheath potential. Unlike RAPLICA-SOL, it is essentially 2D: it operates on consecutive 2D radial-parallel slices, as shown in figure 1, and neglects derivatives in the vertical direction.…”

Section: Sswich-swmentioning

confidence: 99%

“…• SSWICH-SW (Self-consistent Sheaths and Waves for Ion Cyclotron Heating (Slow Wave) [7][8][9]) to selfconsistently determine the nonlinear plasma sheath potential and related quantities.…”

Section: Introductionmentioning

confidence: 99%

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3-Dimensional density profiles in edge plasma simulations for ICRF heating

et al. 2017

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Abstract. In this paper we discuss improvements made to two codes for the simulation of ICRF waves in edge plasmas: SSWICH-SW, which self-consistently models the interplay between sheath physics and radiofrequency waves (the slow wave), and RAPLICASOL, a Finite Element solver for Maxwell's equations in the cold plasma approximation. We have extended both to be able to handle 3D plasma density profiles. A comparison between a 1D and a 3D simulation reveals that the density profile dimensionality has a relatively small effect on E at the aperture, but a large effect on the sheath potential at the antenna limiters

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Section: Sswich-swmentioning

confidence: 99%

Section: Sswich-swmentioning

confidence: 99%

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3-Dimensional density profiles in edge plasma simulations for ICRF heating

et al. 2017

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“…The SSWICH [13][14][15] code follows a three-field approach to self-consistently model the interplay between RF waves and edge plasma DC biasing. In the SSWICH-SW version which is used in this study, the RF waves are reduced to the slow magnetosonic wave (SW) only.…”

Section: Sswich-sw Asymptoticmentioning

confidence: 99%

Sequential modelling of ICRF wave near RF fields and asymptotic RF sheaths description for AUG ICRF antennas

et al. 2017

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Abstract. A sequence of simulations is performed with RAPLICASOL and SSWICH to compare two AUG ICRF antennas. RAPLICASOL outputs have been used as input to SSWICH-SW for the AUG ICRF antennas. Using parallel electric field maps and the scattering matrix produced by RAPLICASOL, SSWICH-SW, reduced to its asymptotic part, is able to produce a 2D radial/poloidal map of the DC plasma potential accounting for the antenna input settings (total power, power balance, phasing). Two models of antennas are compared: 2-strap antenna vs 3-strap antenna. The 2D DC potential structures are correlated to structures of the parallel electric field map for different phasing and power balance. The overall DC plasma potential on the 3-strap antenna is lower due to better global RF currents compensation. Spatial proximity between regions of high RF electric field and regions where high DC plasma potentials are observed is an important factor for sheath rectification.

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“…In Europe, these are implemented in the Self-consistent Sheaths and Waves for Ion Cyclotron Heating (SSWICH) code [1], [2], [3], using the Newton-Raphson scheme in the multiphysics solver COMSOL. As an intermediate step the code also computes the complex oscillating voltages V RF at sheath boundaries.…”

Section: Icrf Antennas As Active Plasmafacing Componentsmentioning

confidence: 99%

SOL RF physics modelling in Europe, in support of ICRF experiments

Colas¹,

Jacquot

et al. 2017

EPJ Web Conf.

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Abstract.A European project was undertaken to improve the available SOL ICRF physics simulation tools and confront them with measurements. This paper first reviews code upgrades within the project. Using the multi-physics finite element solver COMSOL, the SSWICH code couples RF full-wave propagation with DC plasma biasing over "antenna-scale" 2D (toroidal/radial) domains, via non-linear RF and DC sheath boundary conditions (SBCs) applied at shaped plasma-facing boundaries. For the different modules and associated SBCs, more elaborate basic research in RF-sheath physics, SOL turbulent transport and applied mathematics, generally over smaller spatial scales, guides code improvement. The available simulation tools were applied to interpret experimental observations on various tokamaks. We focus on robust qualitative results common to several devices: the spatial distribution of RF-induced DC bias; left-right asymmetries over strap power unbalance; parametric dependence and antenna electrical tuning; DC SOL biasing far from the antennas, and RF-induced density modifications. From these results we try to identify the relevant physical ingredients necessary to reproduce the measurements, e.g. accurate radiated field maps from 3D antenna codes, spatial proximity effects from wave evanescence in the near RF field, or DC current transport. Pending issues towards quantitative predictions are also outlined. ICRF antennas as active PlasmaFacing ComponentsThe phased strap arrays used to launch Ion Cyclotron Range of Frequency (ICRF, 30-80MHz) waves into magnetic fusion devices poorly radiate in vacuum: efficient coupling of the fast wave to the main plasma necessitates minimizing the distance from the straps to a critical peripheral density: the R-cutoff layer. In the Scrape-Off Layer (SOL) the antennas then behave as Plasma-facing Components (PFCs), subject to PlasmaSurface Interactions (PSI). As RF-field-emitting structures, ICRF antennas are active PFCs able to create RF-specific PSI and to modify locally their environment: enhanced ion energies, heat loads, erosion and density modifications have been observed locally. These phenomena are critical in the prospect of long-pulse machines with high-Z plasma-facing materials. Predicting the magnitude and spatial location of these processes, in relation with plasma parameters, launcher design and electrical settings, remains challenging. So far, realistic tokamak predictions relied on very simple models of oscillating double probes. A European project was undertaken to improve the available SOL RF physics simulation tools and confront them with measurements. This paper first reviews code improvements and associated basic research within the project. The available simulation tools are then applied to interpret experimental observations on various machines. From these results we exhibit qualitative properties common to the various devices, identify relevant physical ingredients necessary to reproduce the measurements, as well as pending issues towards quantitative predictions. I...

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Self consistent radio-frequency wave propagation and peripheral direct current plasma biasing: Simplified three dimensional non-linear treatment in the “wide sheath” asymptotic regime

Cited by 53 publications

References 45 publications

3-Dimensional density profiles in edge plasma simulations for ICRF heating

3-Dimensional density profiles in edge plasma simulations for ICRF heating

Sequential modelling of ICRF wave near RF fields and asymptotic RF sheaths description for AUG ICRF antennas

SOL RF physics modelling in Europe, in support of ICRF experiments

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