Kinetic simulations of X-B and O-X-B mode conversion

Arefiev, Alexey; Toit, E. J. Du; Köhn, A.; Holzhauer, E.; Shevchenko, V.; Vann, R. G. L.

doi:10.1063/1.4936540

Cited by 2 publications

(5 citation statements)

References 4 publications

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“…Using the described 1D and 2D setups, we have performed PIC simulations of EBW excitation by waves with a relatively low amplitude (10 5 and 5 × 10 4 V m −1 ). We have reproduced X-B and O-X-B mode conversion, with the O-mode, X-mode, and the excited EBW matching their linear dispersion relations [12]. These benchmarking runs confirm that PIC simulation is suitable for studies of EBW excitation and, most importantly, they identify the simulation parameters needed to correctly reproduce the mode conversion.…”

Section: D and 2d Pic Setups For Studying Ebw Excitationsupporting

confidence: 55%

“…In a recent publication [12], we proposed 1D and 2D setups that are suitable for simulation and clear identification of the EBW excitation using a standard PIC code (figure 1). Both setups have common features that need to be emphasized.…”

Section: D and 2d Pic Setups For Studying Ebw Excitationmentioning

confidence: 99%

“…A plane incoming wave is injected into a vacuum gap that is deliberately introduced between the plasma and the computational domain boundary on the injection side. A uniform One-and two-dimensional setups for PIC simulations of the X-B and O-X-B mode conversion (Reproduced from [12], with the permission of AIP Publishing). magnetic field B 0 that is parallel to the injection boundary is initialized throughout the simulation domain.…”

Section: D and 2d Pic Setups For Studying Ebw Excitationmentioning

confidence: 99%

“…One suitable approach is the particle-in-cell (PIC) framework that uses macro-particles to simulate electrons and ions kinetically. In a recent publication [12], we reported results of one-dimensional (1D) and two-dimensional (2D) simulations performed in a linear regime using the particle-in-cell code EPOCH [13]. (For another relevant project involving PIC simulations of upperhybrid (UH) waves see [14].)…”

Section: Introductionmentioning

confidence: 99%

“…Figure 1.One-and two-dimensional setups for PIC simulations of the X-B and O-X-B mode conversion (Reproduced from[12], with the permission of AIP Publishing).…”

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confidence: 99%

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Kinetic simulations of X-B and O-X-B mode conversion and its deterioration at high input power

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Spherical tokamak plasmas are typically overdense and thus inaccessible to externally-injected microwaves in the electron cyclotron range. The electrostatic electron Bernstein wave (EBW), however, provides a method to access the plasma core for heating and diagnostic purposes. Understanding the details of the coupling process to electromagnetic waves is thus important both for the interpretation of microwave diagnostic data and for assessing the feasibility of EBW heating and current drive. While the coupling is reasonably wellunderstood in the linear regime, nonlinear physics arising from high input power has not been previously quantified. To tackle this problem, we have performed one-and two-dimensional fully kinetic particle-in-cell simulations of the two possible coupling mechanisms, namely X-B and O-X-B mode conversion. We find that the ion dynamics has a profound effect on the field structure in the nonlinear regime, as high amplitude shortscale oscillations of the longitudinal electric field are excited in the region below the high-density cut-off prior to the arrival of the EBW. We identify this effect as the instability of the X wave with respect to resonant scattering into an EBW and a lower-hybrid wave. We calculate the instability rate analytically and find this basic theory to be in reasonable agreement with our simulation results.

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Section: D and 2d Pic Setups For Studying Ebw Excitationsupporting

confidence: 55%

Section: D and 2d Pic Setups For Studying Ebw Excitationmentioning

confidence: 99%

Section: D and 2d Pic Setups For Studying Ebw Excitationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…Figure 1.One-and two-dimensional setups for PIC simulations of the X-B and O-X-B mode conversion (Reproduced from[12], with the permission of AIP Publishing).…”

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Kinetic simulations of X-B and O-X-B mode conversion and its deterioration at high input power

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Parametric decay of plasma waves near the upper-hybrid resonance

Dodin

Arefiev²

2017

Physics of Plasmas

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An intense X wave propagating perpendicularly to dc magnetic field is unstable with respect to a parametric decay into an electron Bernstein wave and a lower-hybrid wave. A modified theory of this effect is proposed that extends to the high-intensity regime, where the instability rate γ ceases to be a linear function of the incident-wave amplitude. An explicit formula for γ is derived and expressed in terms of cold-plasma parameters. Theory predictions are in reasonable agreement with the results of the particle-in-cell simulations presented in a separate publication.

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Kinetic simulations of X-B and O-X-B mode conversion

Cited by 2 publications

References 4 publications

Kinetic simulations of X-B and O-X-B mode conversion and its deterioration at high input power

Kinetic simulations of X-B and O-X-B mode conversion and its deterioration at high input power

Parametric decay of plasma waves near the upper-hybrid resonance

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