Role of zonal flow staircase in electron heat avalanches in KSTAR L-mode plasmas

Qi, Lei; Choi, M.; Kwon, Jae-Min; Hahm, Tae Soo

doi:10.1088/1741-4326/abc976

“…A zonal flow conserving Krook operator 21 is employed to control discrete particle noises and to provide source energy for maintaining the temperature and density profiles so that their averages in time remain close to initial values. The simulation program has been successfully applied to study CTEM turbulence in various situations 22 – 24 .…”

Section: Methodsmentioning

confidence: 99%

Energy transfer of trapped electron turbulence in tokamak fusion plasmas

Qi

¹

2022

Sci Rep

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3

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The first principle gyrokinetic simulations of trapped electron turbulence in tokamak fusion plasmas demonstrate the energy transfers from the most linearly unstable modes at high $$k_\theta \rho _i\sim 1$$ k θ ρ i ∼ 1 to intermediate $$k_\theta$$ k θ via parametric decay process in a short period of linear-nonlinear transition phase. Dominant nonlinear wave-wave interactions occur near the mode rational surface $$m\simeq nq$$ m ≃ n q . In fully nonlinear turbulence, inverse energy cascade occurs between a cutoff wave number $$k_c$$ k c and $$k_\theta \rho _i\sim 1$$ k θ ρ i ∼ 1 with a power law scaling $$|\phi (k_\theta )|^2\propto k^{-3}$$ | ϕ ( k θ ) | 2 ∝ k - 3 , while modes with $$k<k_c$$ k < k c are suppressed. The numerical findings show fair agreement with both the weak turbulence theory and realistic experiments on Tore Supra tokamak.

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“…radius and time. One clearly observes the radially oscillating zonal pattern known as 'staircase' [13,14,15,19,20,21,27,28,29,30,31,32,33]. The time-trace of electron .…”

Section: Response-time Comparison With Gyrokinetic Simulations Of Cte...mentioning

confidence: 99%

“…Hydrogen is the main ion m i /me = 1836 and plasma elongation κ = 2. The turbulent transport of this plasma is dominated by CTEM [22,21]. A limitcycle type of dynamics between Γ e and n 7a].…”

Section: Response-time Comparison With Gyrokinetic Simulations Of Cte...mentioning

confidence: 99%

“…The rest of this article is organized as follows: In Section 2, we describe the Lotka-Volterra Predator-Prey model, and we derive its time-dependent solution analytically. In Section 3, we apply the newly-found solutions to understand the predator-prey dynamics between zonal density perturbations and the turbulent particle flux observed in global gyrokinetic simulations of collision-less trapped-electron mode turbulence (CTEM) [19,21,22,23]. Finally in Section 4, we discuss the results and give a conclusion.…”

Section: Introductionmentioning

confidence: 99%

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Limit Cycle Oscillations, response time and the time-dependent solution to the Lotka-Volterra Predator-Prey model

Leconte,

Masson,

Qi

2021

Preprint

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In this work, the time-dependent solution for the Lotka-Volterra Predator-Prey model is derived with the help of the Lambert W function. This allows an exact analytical expression for the period of the associated limit-cycle oscillations (LCO), and also for the response time between predator and prey population. These results are applied to the predator-prey interaction of zonal density corrugations and turbulent particle flux in gyrokinetic simulations of collisionless trapped-electron model (CTEM) turbulence. In the turbulence simulations, the response time is shown to increase when approaching the linear threshold, and the same trend is observed in the Lotka-Volterra model.

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“…Their fluctuations cause complex structures and dynamics not only in configuration space, e.g. turbulent spreading [20][21][22][23], avalanches and bursts [24][25][26][27][28][29], finescale pressure corrugations, referred to as staircase [30][31][32][33][34][35][36], etc. but also in velocity space, e.g.…”

Section: Introductionmentioning

confidence: 99%

Characteristics of constrained turbulent transport in flux-driven toroidal plasmas

Kishimoto

¹

,

Imadera

²

,

Ishizawa

³

et al. 2023

Phil. Trans. R. Soc. A.

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We study the dynamics of turbulence transport subject to a constraint on the profile formation and relaxation, dominated by the ion temperature gradient modes, within the framework of adiabatic electron response using a flux-driven global gyro-kinetic toroidal code, GKNET. We observe exponentially constrained profiles, with two different scale lengths, that are spatially constant in each region in higher input power regimes. The profiles are smoothly connected in the knee region located at 1 / 2 − 2 / 3 of the minor radius, outside which the gradient is steepened and shows a weak confinement improvement. Based on the probability density function analysis of heat flux eddies, the power law demonstrates a dependence on the eddy size S , as P ∼ S − α , which distinguishes events into diffusive and non-diffusive parts including the validation of quasi-linear hypotheses. Radially localized avalanches and global bursts, which exhibit different spatial scales, play central roles in giving rise to constrained profiles on an equal footing. It is also found that the E × B shear layers are initiated by the global bursts, which evolve downward on a slow time scale across the knee region and play a role in adjusting the profile by increasing the gradient. This article is part of a discussion meeting issue ‘H-mode transition and pedestal studies in fusion plasmas’.

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Role of zonal flow staircase in electron heat avalanches in KSTAR L-mode plasmas

Cited by 21 publications

References 33 publications

Energy transfer of trapped electron turbulence in tokamak fusion plasmas

Energy transfer of trapped electron turbulence in tokamak fusion plasmas

Limit Cycle Oscillations, response time and the time-dependent solution to the Lotka-Volterra Predator-Prey model

Characteristics of constrained turbulent transport in flux-driven toroidal plasmas

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