Internal measurement of magnetic turbulence in ELMy H-mode tokamak plasmas

Chen, J.; Brower, D. L.; Ding, W. X.; Yan, Z.; Osborne, T.H.; Strait, E. J.; Curie, M.; Hatch, D. R.; Kotschenreuther, M.; Xiang, Jian; Halfmoon, Michael; Mahajan, S. M.

doi:10.1063/5.0029996

Cited by 21 publications

(38 citation statements)

References 30 publications

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“…The MTM has been theoretically/numerically predicted to be unstable in the pedestal [15,25], which is also suggested by experimental observations [23,26,27]. However, a comprehensive analysis of experimental data using first principles simulation to confirm MTMs to be the dominant mechanism in controlling the pedestal gradient is still lacking.…”

Section: Introductionmentioning

confidence: 82%

“…The magnetic turbulence is inferred to exist in the pedestal region since it is correlated with the pedestal evolution as indicated by the periodic synchronization between the magnetic turbulence amplitude and the D α signal (figures 1(e) and (f)) transiently emitted when ELMs occur. Magnetic turbulence is weakest after the pedestal collapses after the ELM and becomes stronger with advancing time until the next ELM event [26]. Such an observation does not seem to apply to the fluctuations <100 kHz, suggesting it is unlikely to be relevant to the pedestal behavior and is out of interest in this paper.…”

Section: Experimental Observation and Mtm Identificationmentioning

confidence: 88%

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Gyrokinetic simulation of pedestal degradation correlated with enhanced magnetic turbulence in a DIII-D ELMy H-mode discharge

Jian,

Chen,

Holland

et al. 2024

Plasma Phys. Control. Fusion

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Gyrokinetic simulation of a dedicated pedestal density ramping-up discharge on DIII-D can reproduce the enhancement of magnetic turbulence in the pedestal, which is identified to be caused by micro-tearing modes (MTM). Increase of MTM amplitude results in higher electron thermal diffusivity, consistent with experimentally observed lower electron temperature gradient and degraded pedestal height. Gyrokinetic simulation identifies the major cause of MTM enhancement to be the increase of collisionality, which has a significant impact on the MTM intensity and is beyond the description of any (quasi-)linear theory.

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Section: Introductionmentioning

confidence: 82%

Section: Experimental Observation and Mtm Identificationmentioning

confidence: 88%

Gyrokinetic simulation of pedestal degradation correlated with enhanced magnetic turbulence in a DIII-D ELMy H-mode discharge

Jian,

Chen,

Holland

et al. 2024

Plasma Phys. Control. Fusion

Self Cite

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show abstract

“…Furthermore, while the destabilization mechanism studied here relies on the absence of strong long-wavelength turbulence, in the Hmode pedestal ion transport is often reduced to neoclassical levels [29]. However, the interaction of broad-scale ETG with long-wavelength electromagnetic instabilities like microtearing modes (MTMs) that are often present in the pedestal [30] is computationally challenging but may also need to be considered.…”

Section: Mechanism Bmentioning

confidence: 99%

Flow-shear destabilization of multiscale electron turbulence

Belli,

Candy,

Sfiligoi

2024

Plasma Phys. Control. Fusion

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The impact of sheared $\exb$ flow on multiscale turbulence is studied with nonlinear gyrokinetic simulations. Simulations are based on DIII-D-like, high-confinement mode (H-mode) pedestal parameters in the regime of low ion temperature gradient drive, where there is a broad spectrum of electron temperature gradient (ETG)-driven turbulence. It is found that $\exb$ shear can have a significant effect on ETG-driven electron transport, with an unexpected transition from a turbulence stabilization regime at moderate to large shearing rates $\gamma_E$ to a novel turbulence destabilization regime at low levels of $\gamma_E$. In the turbulence stabilization regime, the electron energy flux decreases monotonically with $\gamma_E$, even when $\gamma_E$ is small compared to electron mode growth rates. The stabilizing effect comes dominantly from the electron, not ion, gyrokinetic equation. In the novel destabilization regime, reduction of zonal energy results from the interaction of $\gamma_E$-modulated nonlinear drive in the zonal ion gyrokinetic equation, increasing the electron transport over a broad range of shearing rates. Neither of these effects have been observed in previous electron-scale simulations.

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“…The magnetic fluctuation B measurement can provide experimental verification of the theory and model of magnetic turbulence [7], especially in high beta plasma. In tokamak plasma, the magnetic fluctuation is typically measured by magnetic coils [3], motional stark effect (MSE) [8], polarimetry [4,9], etc. .…”

Section: Introductionmentioning

confidence: 99%

Design of the cross-polarization scattering diagnostic on the HL-2A tokamak

Tong¹,

Zhong²,

Wen³

et al. 2022

J. Inst.

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A new cross-polarization scattering (CPS) diagnostic has been developed on HL-2A, which aims to measure the local magnetic fluctuation inside the plasma. It is based on the scattering of an incident microwave beam into the perpendicular polarization by magnetic fluctuations. The CPS diagnostic has been designed in the Q-band (33–50 GHz), which consists of the electronic system, quasi-optical, and polarization rejector. The ray-tracing code is used to simulate the propagation of the probe and scattered rays. To test the performance of the quasi-optical system, a 3D test platform is built and detailed test results are shown. Two methods are developed for polarization rejector on HL-2A: wire grid polarizer and dual-polarized horn antenna (DPHA). The laboratory test result shows that the polarization rejection of both methods is better than 30 dB, which meets the needs for magnetic fluctuation detection. In the future, the CPS diagnosis will be used to study the electromagnetic turbulence behavior in the high-performance plasma of the HL-2A tokamak.

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Internal measurement of magnetic turbulence in ELMy H-mode tokamak plasmas

Cited by 21 publications

References 30 publications

Gyrokinetic simulation of pedestal degradation correlated with enhanced magnetic turbulence in a DIII-D ELMy H-mode discharge

Gyrokinetic simulation of pedestal degradation correlated with enhanced magnetic turbulence in a DIII-D ELMy H-mode discharge

Flow-shear destabilization of multiscale electron turbulence

Design of the cross-polarization scattering diagnostic on the HL-2A tokamak

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