Kinetic ballooning mode under steep gradient: High order eigenstates and mode structure parity transition

Xie, Huasheng; Lu, Zhixin; Li, Bo

doi:10.1063/1.5025949

Cited by 9 publications

(11 citation statements)

References 36 publications

(61 reference statements)

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“…Rather, this appears to be an odd parity KBM, which will be labelled as an oKBM and will be represented with the filled green stars as seen in figure 8(a). This oKBM is a higher order eigenstate of the KBM and has been seen before in steep-gradient simulations [49]. If this is an oKBM, it should be seen when scanning through a/L T i .…”

Section: Impact Of Kinetic Profilessupporting

confidence: 65%

Linear gyrokinetic stability of a high β non-inductive spherical tokamak

et al. 2021

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Spherical tokamaks (STs) have been shown to possess properties desirable for a fusion power plant such as achieving high plasma β and having increased vertical stability. To understand the confinement properties that might be expected in the conceptual design for a high β ST fusion reactor, a 1 GW ST plasma equilibrium was analysed using local linear gyrokinetics to determine the type of micro-instabilities that arise. Kinetic ballooning modes and micro-tearing modes are found to be the dominant instabilities. The parametric dependence of these linear modes was determined and, from the insights gained, the equilibrium was tuned to find a regime marginally stable to all micro-instabilities at θ 0 = 0.0. This work identifies the most important micro-instabilities expected to generate turbulent transport in high β STs. The impact of such modes must be faithfully captured in first-principles-based reduced models of anomalous transport that are needed for predictive simulations.

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Section: Impact Of Kinetic Profilessupporting

confidence: 65%

Linear gyrokinetic stability of a high β non-inductive spherical tokamak

et al. 2021

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“…In addition, transition in the mode parity can occur, often related to discontinuous jumps in the mode frequency and to changes in the mode propagation direction (e.g., from the ion to the electron diamagnetic direction or vice versa). The presence of these unconventional modes can potentially influence the level of particle and heat turbulent transport in the H-mode pedestal (Fulton et al 2014;Xie et al 2017b;Pueschel et al 2019), and can possibility affect the commonly used mode identification criteria (Dickinson et al 2012;Xie et al 2018;Pueschel et al 2019).…”

Section: Microinstabilities In Steep Pressure Gradient Conditionsmentioning

confidence: 99%

Moment-Based Approach to the Flux-Tube linear Gyrokinetic Model

Frei¹,

D.²,

Ricci³

et al. 2022

Preprint

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This work reports on the development and numerical implementation of the linear electromagnetic gyrokinetic (GK) model in a tokamak flux-tube geometry using a moment approach based on the expansion of the perturbed distribution function on a velocity-space Hermite-Laguerre polynomials basis. A hierarchy of equations of the expansion coefficients, referred to as the gyro-moments (GM), is derived. We verify the numerical implementation of the GM hierarchy in the collisionless limit by performing a comparison with the continuum GK code GENE, recovering the linear properties of the ion-temperature gradient, trapped electron, kinetic ballooning, and microtearing modes, as well as the collisionless damping of zonal flows. A careful analysis of the distribution functions and ballooning eigenmode structures is performed. The present investigation reveals the ability of the GM approach to describe fine velocity-space scale structures appearing near the trapped and passing boundary and kinetic effects associated with parallel and perpendicular particle drifts. In addition, the effects of collisions are studied using advanced collision operators, including the GK Coulomb collision operator. The main findings are that the number of GMs necessary for convergence decreases with plasma collisionality and is lower for pressure gradient-driven modes, such as in H-mode pedestal regions, compared to instabilities driven by trapped particles and magnetic gradient drifts often found in the core. The accuracy of approximations often used to model collisions (relative to the GK Coulomb operator) is studied in the case of trapped electron modes, showing differences between collision operator models that increase with collisionality and electron temperature gradient. Such differences are not observed in other edge microinstabilities, such as microtearing modes. The importance of a proper collision operator model is also pointed out by analyzing the collisional damping of geodesic acoustic modes and zonal flows. The present linear analysis demonstrates that the GM approach efficiently describes the plasma dynamics for typical parameters of the tokamak boundary, ranging from the low-collisionality banana H-mode to the highcollisionality Pfirsch-Schlüter conditions.

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“…2019), and can possibility affect the commonly used mode identification criteria (Dickinson et al. 2012; Xie, Lu & Li 2018; Pueschel et al. 2019).…”

Section: Microinstabilities In Steep Pressure Gradient Conditionsmentioning

confidence: 99%

“…from the ion to the electron diamagnetic direction or vice versa). The presence of these unconventional modes can potentially influence the level of particle and heat turbulent transport in the H-mode pedestal (Fulton et al 2014;Xie et al 2017b;Pueschel et al 2019), and can possibility affect the commonly used mode identification criteria (Dickinson et al 2012;Xie, Lu & Li 2018;Pueschel et al 2019).…”

Section: Microinstabilities In Steep Pressure Gradient Conditionsmentioning

confidence: 99%

Moment-based approach to the flux-tube linear gyrokinetic model

Frei,

Hoffmann,

Ricci

et al. 2023

J. Plasma Phys.

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This work reports on the development and numerical implementation of the linear electromagnetic gyrokinetic (GK) model in a tokamak flux-tube geometry using a moment approach based on the expansion of the perturbed distribution function on a velocity-space Hermite–Laguerre polynomials basis. A hierarchy of equations of the expansion coefficients, referred to as the gyro-moments (GMs), is derived. We verify the numerical implementation of the GM hierarchy in the collisionless limit by performing a comparison with the continuum GK code GENE, recovering the linear properties of the ion temperature gradient, trapped electron, kinetic ballooning and microtearing modes, as well as the collisionless damping of zonal flows. An analysis of the distribution functions and ballooning eigenmode structures is performed. The present investigation reveals the ability of the GM approach to describe fine velocity-space-scale structures appearing near the trapped and passing boundary and kinetic effects associated with parallel and perpendicular particle drifts. In addition, the effects of collisions are studied using advanced collision operators, including the GK Coulomb collision operator. The main findings are that the number of GMs necessary for convergence decreases with plasma collisionality and is lower for pressure gradient-driven modes, such as in H-mode pedestal regions, compared with instabilities driven by trapped particles and magnetic gradient drifts often found in the core. The accuracy of approximations often used to model collisions (relative to the GK Coulomb operator) is studied in the case of trapped electron modes, showing differences between collision operator models that increase with collisionality and electron temperature gradient, consistent with the results of Pan et al. (Phys. Rev. E, vol. 103, 2021, L051202). Such differences are not observed in other edge microinstabilities, such as microtearing modes. The importance of a proper collision operator model is also confirmed by analysing the collisional damping of geodesic acoustic modes and zonal flows.

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Kinetic ballooning mode under steep gradient: High order eigenstates and mode structure parity transition

Cited by 9 publications

References 36 publications

Linear gyrokinetic stability of a high β non-inductive spherical tokamak

Linear gyrokinetic stability of a high β non-inductive spherical tokamak

Moment-Based Approach to the Flux-Tube linear Gyrokinetic Model

Moment-based approach to the flux-tube linear gyrokinetic model

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