Electromagnetic characteristics of geodesic acoustic mode in the COMPASS tokamak

Seidl, J.; Krbec, J.; Hron, M.; Adámek, Jiřı́; Hidalgo, C.; Markovič, T.; Melnikov, A. V.; Ştöckel, J.; Weinzettl, V.; Aftanas, M.; Bílková, P.; Bogar, O.; Böhm, P.; Eliseev, L.G.; Hacek, P.; Havlíček, J.; Horáček, J.; Imríšek, M.; Kovařík, K.; Mitošínková, K.; Pánek, R.; Tomeš, M.; Vondráček, P.

doi:10.1088/1741-4326/aa897e

Cited by 31 publications

(45 citation statements)

References 53 publications

(92 reference statements)

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“…The typical systematic discrepancy of 1 cm yields error of both T e LCFS and n LCFS e values by a factor of exp(1 cm/λ omp q ) > 10. It was attempted on COMPASS [35] and TCV [36] to identify the LCFS using various techniques, yielding to systematic shift outwards from the (EFIT or Liuqe) magnetic outer midplane separatrix by ≈2 cm on COMPASS and 0.5 cm on TCV. However, even though this method seems more precise than the magnetic equilibrium reconstruction, it is not regularly used on tokamaks since it is quite complex and requires special diagnostics.…”

Section: Main Result: Power Decay Length Scaling Candidatesmentioning

confidence: 99%

Scaling of L-mode heat flux for ITER and COMPASS-U divertors, based on five tokamaks

et al. 2020

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This contribution aims to improve existing scalings of the L-mode power decay length λ q o m p , especially for plasma configurations with strike points at the ITER-relevant location—closed vertical divertor targets. We propose 13 new λ q o m p scalings based on data from the tokamaks JET, EAST, MAST, Alcator C-mod and COMPASS, and validate them against the output of the 2D turbulence code HESEL. The analysis covers 500 divertor heat flux profiles (obtained by probes or IR cameras), measured in L-mode discharges with varying 12 global plasma parameters (all well predictable). We find that the two previously published scalings (Eich 2013 J. Nucl. Mat. 438 S72) and (Scarabosio 2013 J. Nucl. Mat. 438 S426), which were based on outer target data from AUG and JET, describe the JET, C-mod and COMPASS profiles well. This holds not only at the outer horizontal and vertical targets, but surprisingly also at the inner vertical targets. In contrast, EAST, HESEL and especially MAST data are poorly described by these two scalings. We therefore derive 13 new scalings, which account for 85–92 % of the measured λ q o m p variability across all five tokamaks. Although each of the scalings is based on a different parameter combination, their predictions for the ITER and COMPASS-Upgrade tokamaks are very similar. Just before the L-H transition in the ITER baseline scenario, the presented scalings predict values λ q o m p = 3.0 ± 0.5 mm. For the COMPASS-Upgrade tokamak, all the scalings predict λ q o m p = 2.1 ± 0.5 mm with a single exception of the scaling based on the stored plasma energy which predicts only 1.2 mm for both tokamaks. We encourage the reader to use as many of these scalings as possible, depending on available data. In attached plasma and using significant assumptions, our results imply steady-state surface-perpendicular heat flux around 10 MW/m2 for ITER, and 20 MW/m2 for COMPASS-Upgrade.

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Section: Main Result: Power Decay Length Scaling Candidatesmentioning

confidence: 99%

Scaling of L-mode heat flux for ITER and COMPASS-U divertors, based on five tokamaks

et al. 2020

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“…Mostly probes are used in multiple pin combinations or arrays (LPA) with both radial and poloidal/toroidal separations from which the Ẽr ≈ (φ 1 − φ 2 )/δr is approximated. LPs have been extensively employed on many devices: DIII-D [274], HT-7 [27], H1-NF [402], T-10 [292], JFT-2M [316], HL-2A [345], IST-TOK [361], CHS hybrid probe array [408], TEXTOR [342], MAST Gunderstrup reciprocating probe [374], J-TEXT [389] and COMPASS [394].…”

Section: Diagnostic Techniquesmentioning

confidence: 99%

Geodesic acoustic modes in magnetic confinement devices

Smolyakov

Ido

2021

Nucl. Fusion

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Geodesic acoustic modes (GAMs) are ubiquitous oscillatory flow phenomena observed in toroidal magnetic confinement fusion plasmas, such as tokamaks and stellarators. They are recognized as the non-stationary branch of the turbulence driven zonal flows which play a critical regulatory role in cross-field turbulent transport. GAMs are supported by the plasma compressibility due to magnetic geodesic curvature—an intrinsic feature of any toroidal confinement device. GAMs impact the plasma confinement via velocity shearing of turbulent eddies, modulation of transport, and by providing additional routes for energy dissipation. GAMs can also be driven by energetic particles (so-called EGAMs) or even pumped by a variety of other mechanisms, both internal and external to the plasma, opening-up possibilities for plasma diagnosis and turbulence control. In recent years there have been major advances in all areas of GAM research: measurements, theory, and numerical simulations. This review assesses the status of these developments and the progress made towards a unified understanding of the GAM behaviour and its role in plasma confinement. The review begins with tutorial-like reviews of the basic concepts and theory, followed by a series of topic orientated sections covering different aspects of the GAM. The approach adopted here is to present and contrast experimental observations alongside the predictions from theory and numerical simulations. The review concludes with a comprehensive summary of the field, highlighting outstanding issues and prospects for future developments.

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“…Radial propagation of the GAMs has been observed experimentally in several devices [9]- [21]. Unidirectional outward propagating GAMs have been observed in JFT-2M [9], TEXTOR [11], DIII-D [13], HL-2A [14], JET [15], and COMPASS [16]. Inward propagation of the GAMs has been observed in FT-2 [17], and ASDEX-Upgrade [18].…”

Section: Introductionmentioning

confidence: 99%

Propagation direction of geodesic acoustic modes driven by drift wave turbulence

Sasaki¹,

Itoh²,

Kobayashi³

et al. 2018

Nucl. Fusion

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Selection rule of the radial propagation direction of geodesic acoustic modes (GAMs) is investigated. Here, we study the influence of nonlinear coupling with drift wave turbulence on propagation direction of GAMs. Based on wave-kinetic equation for the turbulence, the phase-space dynamics is numerically solved and the nonlinear saturated states are obtained, where the phase-space consists of the real space and the wavenumber space. A wave pattern of the GAM in a nonlinear saturated state varies to form a standing wave, outward and inward propagating waves, depending on the peak radial wavenumber of the turbulence. The impact of nonlinear coupling with turbulence is discussed by deriving the GAM dispersion relation that includes the effect of the turbulence.

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Electromagnetic characteristics of geodesic acoustic mode in the COMPASS tokamak

Cited by 31 publications

References 53 publications

Scaling of L-mode heat flux for ITER and COMPASS-U divertors, based on five tokamaks

Scaling of L-mode heat flux for ITER and COMPASS-U divertors, based on five tokamaks

Geodesic acoustic modes in magnetic confinement devices

Propagation direction of geodesic acoustic modes driven by drift wave turbulence

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