First experimental measurements of a new fast ion driven micro-burst instability in a field-reversed configuration plasma

Deng, B. H.; Douglass, J. D.; Roche, T.; Белова, Е. В.; Beall, M.; Binderbauer, Michl; Clary, R.; Dettrick, Sean; Gota, H.; Granstedt, E.; Korepanov, S.; Magee, Richard; Nečas, Aleš; Onofri, M.; Putvinski, S.; Smirnov, A.; Song, Y.; Tajima, T.; Thompson, Matthew; Tuszewski, M.; Drie, A. D. Van; Yang, Xiaohu; Zhai, K.; Horton, W.

doi:10.1088/1741-4326/aae5df

Cited by 6 publications

(14 citation statements)

References 16 publications

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“…The micro-burst has been found to cause the density profile to become slightly steeper while under constant external field, suggesting it is not driven by the pressure gradient [27]. It was found to correlate strongly with neutral beam energy, suggesting that the instability is related to fast ion behavior [27]. Figure 7 shows the typical behavior of a micro-burst in C-2U.…”

Section: Mitigation Of the Micro-burst Instability In The C-2w Frcmentioning

confidence: 99%

“…The micro-burst instability (also referred to as the staircase mode) has been observed to be a macroscopic, non-destructive instability that occurred in the C-2U device [27]. It shares some qualitative features with the fishbone instability present in tokamaks, but unlike the fishbone instability it is not a kink mode, since kink modes are not possible in the FRC geometry [27]. A thorough examination of the physics of the micro-burst instability in C-2U was completed by Deng et al [27].…”

Section: Mitigation Of the Micro-burst Instability In The C-2w Frcmentioning

confidence: 99%

“…It shares some qualitative features with the fishbone instability present in tokamaks, but unlike the fishbone instability it is not a kink mode, since kink modes are not possible in the FRC geometry [27]. A thorough examination of the physics of the micro-burst instability in C-2U was completed by Deng et al [27]. For the ease of the reader, we will briefly outline the results of that work below.…”

Section: Mitigation Of the Micro-burst Instability In The C-2w Frcmentioning

confidence: 99%

“…Generally, a micro-burst in C-2U can be identified by a fluctuation measured with a far infrared interferometer, with frequencies of approximately 150 kHz, which quickly downchirp to 50 kHz [27]. The micro-burst has been found to cause the density profile to become slightly steeper while under constant external field, suggesting it is not driven by the pressure gradient [27]. It was found to correlate strongly with neutral beam energy, suggesting that the instability is related to fast ion behavior [27].…”

Section: Mitigation Of the Micro-burst Instability In The C-2w Frcmentioning

confidence: 99%

See 3 more Smart Citations

Enhancing historical electron temperature data with an artificial neural network in the C-2U FRC

Player¹,

Magee²,

Tajima³

et al. 2022

Nucl. Fusion

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The electron temperature is a vital parameter in understanding the dynamics of fusion plasmas, helping to determine basic properties of the system, stability, and fast ion lifetime. We present a method for improving the sampling rate of historical Thomson scattering data by a factor of 103 on the decommissioned beam-driven C-2U field reversed configuration device by utilizing an artificial neural network. This work details the construction of the model, including an analysis of input signals and the model hyperparameter space. The model’s performance is evaluated on both a random subset and selected ensemble of testing data and its predictions are found to agree with the Thomson measurements in both cases. Finally, the model is used to reconstruct the effect of the micro-burst instability in C-2U, and then compared to more recent results in C-2W, showing that the effects of the micro-burst on core electron temperature have been mitigated in C-2W.

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Section: Mitigation Of the Micro-burst Instability In The C-2w Frcmentioning

confidence: 99%

Section: Mitigation Of the Micro-burst Instability In The C-2w Frcmentioning

confidence: 99%

Section: Mitigation Of the Micro-burst Instability In The C-2w Frcmentioning

confidence: 99%

Section: Mitigation Of the Micro-burst Instability In The C-2w Frcmentioning

confidence: 99%

See 2 more Smart Citations

Enhancing historical electron temperature data with an artificial neural network in the C-2U FRC

Player¹,

Magee²,

Tajima³

et al. 2022

Nucl. Fusion

Self Cite

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show abstract

“…Although various models have been proposed to analyze the FRC experimental results, the RR model is the simplest one with clear physical meanings and is the most widely used [18,19]. Therefore, the MRR pressure profile model P = P(ψ) is based on the RR model, and is required to be as simple as possible, to have sufficient flexibility for fitting experimental data, and can be reduced to the RR model.…”

Section: The Mrr Equilibrium Modelmentioning

confidence: 99%

Two-parameter Radial Equilibrium Models for Field-Reversed Configurations

Ma,

Xie,

Bai

et al. 2020

Preprint

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A new equilibrium pressure profile extending the Rigid-Rotor (RR) model with a simple unified expression P = P(ψ;β s ,α,σ) for both inside and outside the separatrix is proposed, in which the radial normalized field-reversed configuration (FRC) equilibrium profiles for pressure, magnetic field, and current can be determined by only two dimensionless parameters β s ≡ P s /2µ 0 B 2 e and δ s ≡ L ps /R s , where P s is the thermal pressure at the separatrix, B e is the external magnetic field strength, L ps is the pressure profile scale length at the separatrix, and R s is the separatrix radius. This modified rigid rotor (MRR) model has sufficient flexibility to accommodate the narrow scrape of layer (SOL) width and hollow current density profiles, and can be used to fit experimental measurements satisfactorily. Detailed one-dimensional (1D) characteristics of the new MRR model are investigated analytically and numerically, and the results are also confirmed in two-dimensional (2D) numerical equilibrium solutions.

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Formation of hot, stable, long-lived field-reversed configuration plasmas on the C-2W device

Gota¹,

Binderbauer²,

Tajima³

et al. 2019

Nucl. Fusion

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TAE Technologies' research is devoted to producing high temperature, stable, long-lived field-reversed configuration (FRC) plasmas by neutral-beam injection (NBI) and edge biasing/control. The newly constructed C-2W experimental device (also called "Norman") is the world's largest compact-toroid (CT) device, which has several key upgrades from the preceding C-2U device such as higher input power and longer pulse duration of the NBI system as well as installation of inner divertors with upgraded electrode biasing systems. Initial C-2W experiments have successfully demonstrated a robust FRC formation as well as its translation into the confinement vessel through the newly installed inner divertor with adequate guide magnetic field. They also produced dramatically improved initial FRC parameters with higher plasma temperatures (Te up to 300 eV; total electron and ion temperature >1.5 keV) and more trapped flux (up to ~15 mWb, based on rigid-rotor model) inside the FRC immediately after the merger of collided two CTs in the confinement section. As for effective edge biasing/control on FRC stabilization, a number of edge biasing schemes have been tried via open-fieldlines, in which concentric electrodes located in both inner and outer divertors as well as end-on plasma guns are electrically biased independently. As a result of effective outer-divertor electrode biasing alone, FRC plasma diamagnetism duration has reached up to ~9 ms which is equivalent to C-2U plasma duration. Magnetic field flaring/expansion in both inner and outer divertors plays an important role in creating a thermal insulation on open-field-lines to reduce a loss rate of electrons, which leads to improvement of the edge as well as core FRC confinement properties.

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First experimental measurements of a new fast ion driven micro-burst instability in a field-reversed configuration plasma

Cited by 6 publications

References 16 publications

Enhancing historical electron temperature data with an artificial neural network in the C-2U FRC

Enhancing historical electron temperature data with an artificial neural network in the C-2U FRC

Two-parameter Radial Equilibrium Models for Field-Reversed Configurations

Formation of hot, stable, long-lived field-reversed configuration plasmas on the C-2W device

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