Effect of the scrape-off layer in AORSA full wave simulations of fast wave minority, mid/high harmonic, and helicon heating regimes

Bertelli, N.; Jaeger, E. F.; Lau, C.; Blazevski, Daniel; Green, D. L.; Berry, L. A.; Bonoli, P. T.; Gerhardt, S. P.; Hosea, J. C.; LeBlanc, B.P.; Perkins, R. J.; Phillips, C. K.; Pinsker, R. I.; Prater, R.; Qin, Chengming; Ryan, P. M.; Taylor, G.; Valeo, E. J.; Wilson, J. R.; Wright, J. C.; Zhang, X. J.

doi:10.1063/1.4936475

Cited by 3 publications

(2 citation statements)

References 17 publications

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“…Collisions in this model are also used as a proxy for possible deleterious physical mechanisms for LH SOL absorption that could be due to parametric decay, Landau damping of high n || modes, or electron-neutral collisions [37]. Given that it is unclear how large an effect these physical mechanisms have on the LH SOL losses, a collisional proxy damping mechanism [38,39] can be used to provide insight into the effect of turbulence on the LH wave propagation. This model certainty has limitations and cannot quantitatively predict SOL losses or the LH electric field magnitude.…”

Section: D Cold Plasma Full Wave Modelmentioning

confidence: 99%

Full-wave model for the lower hybrid wave electric field vector with synthetic turbulence on Alcator C-Mod

Lau¹,

Martin²,

Shiraiwa³

et al. 2020

Nucl. Fusion

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The effects of synthetic turbulence on lower hybrid (LH) wave field magnitude and polarization are studied on Alcator C-Mod. Three synthetic turbulence models are evaluated to assess the impact of filaments, holes, and periodic fluctuations on the LH wave electric fields. For all three cases, the synthetic turbulence can greatly impact the LH wave magnitude and polarization. Back scattering, interference and edge/SOL absorption of the LH wave is observed. This impact is shown to depend on the wavelength and amplitude of the fluctuations. The strongest effect appears for fluctuations at high amplitudes and wavelengths comparable to the LH wavelength. This synthetic turbulence model can be used as inputs into a synthetic diagnostic to calculate the lower hybrid wave field magnitude and direction measured by dynamic Stark effect spectroscopy. It will be shown that fluctuations at these high amplitudes and wavelengths may explain the experimentally measured results. The effect of fluctuations on modifying LH polarization are also shown to be anti-correlated with SOL power losses, similar to recently observed experimental trends on Alcator C-Mod. These SOL losses may have detrimental impact on LHCD efficiency.

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Section: D Cold Plasma Full Wave Modelmentioning

confidence: 99%

Full-wave model for the lower hybrid wave electric field vector with synthetic turbulence on Alcator C-Mod

Lau¹,

Martin²,

Shiraiwa³

et al. 2020

Nucl. Fusion

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“…AORSA also currently can solve the helicon wave problem only in a rectangular domain and cannot simulate realistic tokamak vessel geometry. Given that possible standing waves can be sensitive to vacuum vessel geometry [15], realistic geometry could greatly affect the results.…”

Section: Introductionmentioning

confidence: 99%

Cold plasma finite element wave model for helicon waves

Lau

Berry²,

Jaeger³

et al. 2019

Plasma Phys. Control. Fusion

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Helicon waves have been recently proposed as an off-axis current drive actuator due to their expected high current drive efficiency in the mid-radius region in high beta tokamaks. This current drive efficiency has mostly been calculated ignoring the effects of the plasma in the scrape-off-layer (SOL) in the modeling. The net core current drive efficiency will decrease if helicon power is lost to the SOL. Previous efforts to estimate the loss of helicon power in the SOL have used the hot plasma code AORSA. The large computational cost of AORSA prevents large parametric scans, so to further the understanding of helicon power loss in the SOL, a reduced finite element, full wave plasma model with effective collision frequency for collisional and Landau damping has been developed to study the helicon wave power lost to the SOL. It will be shown that the reduced finite element model (FEM) can reproduce the magnitude and trends of helicon |E| field patterns and power loss in the SOL of the hot plasma AORSA model. The reduced FEM provides significant advantages over AORSA in reducing the computational time and memory requirements, and in simulating arbitrary tokamak vessel geometry. Parametric scans of antenna parallel refractive index, antenna location, minimum SOL density, SOL density gradient, and vacuum vessel geometry will be carried out to determine the dependencies of the helicon power lost to the SOL as a function of important parameters. The helicon cutoff density is shown to be an important quantity in determining helicon power lost to the SOL. Losses due to antenna loading and wave accessibility are also observed at different antenna and plasma parameters.

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Survey of heating and current drive for K-DEMO

et al. 2018

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We present calculations of heating and current drive by neutral injection and by electromagnetic waves in the ion cyclotron, helicon, lower hybrid, and electron cyclotron frequency ranges for the steady state burn conditions in a K-DEMO configuration with I p = 12.3 MA, a = 2.1 m, R o = 6.8 m, B o = 7.4 T, n e = 1.1 × 10 20 m −3 , T(0) = 40 keV, and Z eff = 1.5. Lower hybrid wave current drive calculations comprise a 2D scan over poloidal launcher location and launched n , at a fixed frequency of 5 GHz. An ICRF frequency scan over 50-100 MHz is based on an ITER-like ICRF midplane antenna; the absorption calculation includes thermal D, T, He, Ar, and W as well as suprathermal beam ions and alphas. Helicon fast wave performance is surveyed by varying frequency over 0.6-2.5 GHz, launched n from −1.6 to −3, and launcher position from top to bottom on the low-field side. An ITER-like 1 MeV neutral beam system with quasi-tangential geometry is scanned over elevation to vary the targeted minor radius. The electron cyclotron survey varies the frequency (190-300 GHz), launcher poloidal location, and the poloidal and toroidal direction of the launched waves. We report for each system the range of minor radius in which current is driven, the current drive efficiency, the optimal system parameters, and typical profiles of driven current. Electron and ion heating profiles are reported for the ICRF and NBI systems.

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Effect of the scrape-off layer in AORSA full wave simulations of fast wave minority, mid/high harmonic, and helicon heating regimes

Cited by 3 publications

References 17 publications

Full-wave model for the lower hybrid wave electric field vector with synthetic turbulence on Alcator C-Mod

Full-wave model for the lower hybrid wave electric field vector with synthetic turbulence on Alcator C-Mod

Cold plasma finite element wave model for helicon waves

Survey of heating and current drive for K-DEMO

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