Diagnosing the pedestal magnetic field and magnetohydrodynamics radial structure with pedestal–scrape of layer electron cyclotron emission radiation inversion in H-mode plasma (invited)

Yu, Guangyang; Zhu, Yilun; Austin, M. E.; Chen, Y.; Cao, Jianyu; Diallo, A.; Kramer, G. J.; Li, Zeyu; Li, X.; Liu, X.; Nazikian, R.; Zheng, Yuan; Luhmann, Neville C.

doi:10.1063/5.0099348

Cited by 7 publications

(1 citation statement)

References 37 publications

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“…In contrast, if , called the optical thin area, the electron temperature can no longer be easily interpreted by the unless the optical thickness can be predicted in advance. Therefore, the optical thickness is crucial for data interpretation, especially at the edge of a tokamak where the optical thickness is normally thin [22][23][24]. In such cases, synthetic diagnostic using forward modeling can assist in interpreting experimental data even under these non-ideal conditions.…”

Section: I(ω)mentioning

confidence: 99%

A synthetic diagnostics platform for microwave imaging diagnostics in tokamaks

LI 李,

YANG 杨,

XU 徐

et al. 2024

Plasma Sci. Technol.

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Interpreting experimental diagnostics data in tokamaks, which accounts for non-ideal effects, is challenging due to the complexity of plasmas. To address this challenge, a general synthetic diagnostics (GSD) platform that serves for microwave imaging reflectometer (MIR) and electron cyclotron emission imaging (ECEI) has been established. This platform utilizes plasma profiles as input, and it incorporates finite difference time domain (FDTD), ray-tracing and radiative transfer equation to calculate the propagation of plasma spontaneous radiation and external electromagnetic field in plasmas. Benchmarks of classic cases have been conducted to verify the accuracy of every core module in GSD platform. Finally, a 2D imaging of a typical electron temperature distribution is reproduced by this platform and is consistent with the given real experimental data. This platform also has potential to be extended to 3D electromagnetic field simulations and to other microwave diagnostics such as cross-polarization scattering.

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Section: I(ω)mentioning

confidence: 99%

A synthetic diagnostics platform for microwave imaging diagnostics in tokamaks

LI 李,

YANG 杨,

XU 徐

et al. 2024

Plasma Sci. Technol.

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Understanding the negative triangularity ELM trigger and ELM free state on DIII-D with ECE-imaging

Kramer

et al. 2023

Physics of Plasmas

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The Electron Cyclotron Emission Imaging (ECEI) diagnostic was used to observe a finite-n interchange mode structure in the edge of negative triangularity shaped plasmas on DIII-D. At a small negative triangularity (δu = −0.2), the plasma is in the H-mode with ELMs that are triggered by a low-n interchange mode. At a larger negative triangularity (δu = −0.4) and low NBI power (2 MW), a dithering oscillation is observed that is triggered by a low-n interchange mode, whereas at higher NBI power (>2 MW), the edge reverts to L-mode and the low-n interchange mode is present continuously. In all cases, the edge pressure gradient is clamped when the interchange mode is present. It is concluded that the low-n interchange mode prevents the plasma from transitioning to H-mode at a large negative triangularity. This agrees with linear BOUT++ simulations which suggest that the interchange-type MHD can be a resistive ballooning mode whereby resistivity can significantly increase the finite-n ballooning mode growth rate. The absence of H-mode at large negative triangularity can, thus, be explained by the excitation of low-n pressure driven resistive ballooning modes in the plasma edge.

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Refined interpretation of electron temperature response to neutral beam injection at DIII-D

Zhao,

Austin

2023

Physics of Plasmas

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Accurate particle and power deposition profiles of neutral beam injection (NBI) are essential to transport studies, and that information is usually acquired through Monte Carlo simulations with a given collisional model. The deposition process of the energetic beam particles leads to the informative electron temperature (Te) evolution trajectory, which can be captured by electron cyclotron emission (ECE) system due to its good spatial and temporal resolution. Previously, some work has been done to interpret the Te responses to the pulsed NBI as a linear heating source with Fourier-based techniques, although that approach fell short when the fast ion slowing-down time becomes significant (∼100 ms). It has been observed in DIII-D that the modulated NBI pulses (10–50 Hz) reduce local core Te values ∼0.1 keV through cold electron dilution in high-Te (>2 keV) plasmas alongside accumulative heating. Here, a novel approach to interpret the Te response to NBI was developed by linearizing and modeling the detailed Te evolution trajectory using coherently averaged ECE data based on the different time scales of the terms in the local power and particle balance equations. The technique does not require absolute calibrations of ECE and is independent of collisional models. The resulting beam deposition profiles show good consistency and reasonable agreement with Monte Carlo calculations based on the atomic data from the Atomic Data and Analysis Structure (ADAS). Local electron density response measured by Thomson scattering (TS) also suggests the same features when the beam pulse is large enough for that diagnostic to resolve. The remaining discrepancies are also discussed.

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Diagnosing the pedestal magnetic field and magnetohydrodynamics radial structure with pedestal–scrape of layer electron cyclotron emission radiation inversion in H-mode plasma (invited)

Cited by 7 publications

References 37 publications

A synthetic diagnostics platform for microwave imaging diagnostics in tokamaks

A synthetic diagnostics platform for microwave imaging diagnostics in tokamaks

Understanding the negative triangularity ELM trigger and ELM free state on DIII-D with ECE-imaging

Refined interpretation of electron temperature response to neutral beam injection at DIII-D

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