On the ion and electron temperature recovery after the ELM-crash at ASDEX upgrade

Cavedon, M.; Dux, R.; Pütterich, T.; Viezzer, E.; Wolfrum, E.; Dunne, M.; Fable, E.; Fischer, R.; Harrer, G.; Laggner, F. M.; Mink, A. F.; Plank, U.; Stroth, U.; Willensdorfer, M.

doi:10.1016/j.nme.2018.12.034

Cited by 10 publications

(10 citation statements)

References 40 publications

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“…This paper extends our previous work [30][31][32] to the combined analysis of the ion and electron heat transport, as well as the behaviour of the momentum transport during the ELM cycle. Section 2 gives a brief review on the observations of the profile evolution during the ELM cycle.…”

Section: Introductionsupporting

confidence: 67%

Dynamics of the pedestal transport during edge localized mode cycles at ASDEX Upgrade

Viezzer

Cavedon

Cano-Megias

et al. 2020

Plasma Phys. Control. Fusion

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The dynamic behaviour of the ion and electron energy, particle and momentum transport measured during type-I edge localized mode (ELM) cycles at ASDEX Upgrade is presented. Fast measurements of the ion and electron temperature profiles revelead that the ion and electron energy transport recover on different timescales, with the electrons recovering on a slower timescale (Cavedon et al 2017 Plasma Phys. Control. Fusion 59 105007). The dominant mechanism for the additional energy transport in the electron channel that could cause the delay in the electron temperature gradient ( ∇ T e ) recovery is attributed to the depletion of energy caused by the ELM. The local sources and sinks for the electron channel in the steep gradient region are much smaller compared to the energy flux arriving from the pedestal top, indicating that the core plasma may dictate the local dynamics of the ∇ T e recovery during the ELM cycle. A model for the edge momentum transport based on toroidal torque balance that takes into account the existence of poloidal impurity asymmetries has been developed. The analysis of the profile evolution during the ELM cycle shows that the model captures the dynamics of the rotation both before the ELM crash and during the recovery phase.

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Section: Introductionsupporting

confidence: 67%

Dynamics of the pedestal transport during edge localized mode cycles at ASDEX Upgrade

Viezzer

Cavedon

Cano-Megias

et al. 2020

Plasma Phys. Control. Fusion

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“…Related gyrokinetic modeling will be reported in [20]. Collectively, these results suggest that MTMs are likely responsible for many of the most prominent magnetic fluctuations observed in the pedestal of tokamaks (see references [18,[21][22][23][24][25][26]).…”

Section: Introductionmentioning

confidence: 56%

Identifying the microtearing modes in the pedestal of DIII-D H-modes using gyrokinetic simulations

Hassan¹,

Hatch²,

Halfmoon³

et al. 2021

Nucl. Fusion

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Recent evidence points toward the microtearing mode (MTM) as an important fluctuation in the H-mode pedestal for anomalous electron heat transport. A study of the instabilities in the pedestal region carried out using gyrokinetic simulations to model an ELMy H-mode DIII-D discharge (USN configuration, 1.4 MA plasma current, and 3 MW heating power) is presented. The simulations produce MTMs, identified by predominantly electromagnetic heat flux, small particle flux, and a substantial degree of tearing parity. The magnetic spectrogram from Mirnov coils exhibits three distinct frequency bands---two narrow bands at lower frequency ($\sim$35-55 kHz and $\sim$70-105 kHz) and a broader band at higher frequency ($\sim$300-500 kHz). Global linear GENE simulations produce MTMs that are centered at the peak of the $\omega_*$ profile and correspond closely with the bands in the spectrogram. The three distinctive frequency bands can be understood from the basic physical mechanisms underlying the instabilities. For example (i) instability of certain toroidal mode numbers (n) is controlled by the alignment of their rational surfaces with the peak in the $\omega^*$ profile, and (ii) MTM instabilities in the lower n bands are the conventional collisional slab MTM, whereas the higher n band depends on curvature drive. While many features of the modes can be captured with the local approximation, a global treatment is necessary to quantitatively reproduce the detailed band gaps of the low-n fluctuations. Notably, the transport signatures of the MTM are consistent with careful edge modeling by SOLPS.

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“…We note that these values of η e are similar to observations in a number of other devices and operating scenarios. Analysis of electron density and temperature pedestal profiles in ASDEX-Upgrade observed that η e cluster around 1.5-2 in ELMy Hmode [75][76][77]. In Alcator C-mod, η e ∼ 1-2 in EDA H-mode, but becomes increasingly large to 2-4 in ELMy H-mode, or larger yet in I-mode [78,79].…”

Section: Linear Analysismentioning

confidence: 99%

Testing predictions of electron scale turbulent pedestal transport in two DIII-D ELMy H-modes

et al. 2021

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In this paper, we present linear and nonlinear gyrokinetic analyses in the pedestal region of two DIII-D ELMy H-mode discharges using the CGYRO code. The otherwise matched discharges employ different divertor configurations to investigate the impact of varying recycling and particle source on pedestal profiles. Linear gyrokinetic simulations find electrostatic ion-scale instabilities (ion temperature gradient and trapped electron modes, ITG–TEM) are present just inside the top of the pedestal with growth rates that are enhanced significantly by parallel velocity shear. In the sharp gradient region, E × B shearing rates are comparable or larger than ion scale growth rates, suggesting the suppression of ITG–TEM modes in this region. Instead, the electron temperature profiles are found to be correlated with and just above the electron temperature gradient (ETG) instability thresholds. Using gradients varied within experimental uncertainties, nonlinear electron-scale gyrokinetic simulations predict electron heat fluxes from ETG turbulence, that when added to neoclassical (NC) ion thermal transport simulated by NEO, account for 30%–60% of the total experimental heat flux. In addition, the NC electron particle flux is found to contribute significantly to the experimental fluxes inferred from SOLPS-ITER analysis. Additional nonlinear gyrokinetic simulations are run varying input gradients to develop a threshold-based reduced model for ETG transport, finding a relatively simple dependence on η e = L ne/L Te. Predictive transport simulations are used to validate this pedestal-specific ETG model, in conjunction with a model for NC particle transport. In both discharges, the predicted electron temperatures are always overpredicted, indicative of the insufficient stiffness in the ETG pedestal model to account for all of the experimental electron thermal transport. In the case of the closed divertor discharge with lower particle source, the predicted electron density is close to the experiment, consistent with the magnitude of NC particle transport in that discharge. However, the density profiles are overpredicted in the open divertor discharge (larger particle source), due to insufficient model transport. The implications for other mechanisms accounting for the remainder of transport in the sharp gradient region in the two discharges are discussed.

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On the ion and electron temperature recovery after the ELM-crash at ASDEX upgrade

Cited by 10 publications

References 40 publications

Dynamics of the pedestal transport during edge localized mode cycles at ASDEX Upgrade

Dynamics of the pedestal transport during edge localized mode cycles at ASDEX Upgrade

Identifying the microtearing modes in the pedestal of DIII-D H-modes using gyrokinetic simulations

Testing predictions of electron scale turbulent pedestal transport in two DIII-D ELMy H-modes

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