Global geodesic acoustic mode in a tokamak with positive magnetic shear and a monotonic temperature profile

Ilgisonis, V. I.; Khalzov, Ivan; Lakhin, V. P.; Smolyakov, Andrei; Sorokina, E. A.

doi:10.1088/0741-3335/56/3/035001

Cited by 19 publications

(24 citation statements)

References 26 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…There are already some experiments on the JIPPT-IIU tokamak [33,34] and T-10 tokamak [35,36] about the global feature of GAM. Furthermore, as the width of the CM peak is narrow, it may be an evidence of the global eigenmode [37][38][39]. We conclude that the CM is a poloidally symmetric (m = 0)…”

Section: The Geodesic Acoustic Mode In the Velocity Fluctuationsmentioning

confidence: 74%

Investigation of zonal flows by using the collective scattering measurement of density fluctuations

Shen

Lan

et al. 2015

Nucl. Fusion

View full text Add to dashboard Cite

The poloidal × E B r T rotation velocities in the core plasma region are studied using the instantaneous frequency method (IFM) with the density fluctuations measured by the CO 2 laser collective scattering diagnostics on the HT-7 tokamak. A coherent mode is observed in the fluctuations of poloidal velocities with the mode frequency from 10 to 20 kHz. It is identified as geodesic acoustic mode (GAM) zonal flow with poloidal symmetry (m = 0) and its mode frequency coinciding with the theoretical expected GAM frequency. The nonlinear interactions are investigated by applying the envelope analysis on the density fluctuations. The results confirm that the envelope modulation in the high frequency density fluctuations only comes from the shearing by GAM. The comparison between IFM and envelope analysis is also discussed.

show abstract

Section: The Geodesic Acoustic Mode In the Velocity Fluctuationsmentioning

confidence: 74%

Investigation of zonal flows by using the collective scattering measurement of density fluctuations

Shen

Lan

et al. 2015

Nucl. Fusion

View full text Add to dashboard Cite

show abstract

“…A good general agreement is found in the central region of interest, where the GAM intensity, measured in the experiments, is peaked. On the other hand, the linear dispersion relation 4 can not explain neither the staircase nature (the plateaus) of the frequencies nor the GAM peak splitting that is observed experimentally at the radius positions ρ = 0.922 or ρ = 0.932 (although the presence of GAM eigenmodes has been suggested by simplified analytical models [37,38], whose detailed analysis is out of the scope of this paper). For this reason, we can conjecture Figure 6: Comparison of the experimental GAM frequencies [26] to the numerical values, obtained with the formula given in Eq.…”

Section: Comparison With Experimental Datamentioning

confidence: 81%

Linear gyrokinetic investigation of the geodesic acoustic modes in realistic tokamak configurations

et al. 2017

View full text Add to dashboard Cite

Geodesic acoustic modes (GAMs) are studied by means of the gyrokinetic global particle-in-cell code ORB5. Linear electromagnetic simulations in the lowβ e limit have been performed, in order to separate acoustic and Alfvénic time scales and obtain more accurate measurements. The dependence of the frequency and damping rate on several parameters such as the safety factor, the GAM radial wavenumber and the plasma elongation is studied. All simulations have been performed with kinetic electrons with realistic electron/ion mass ratio. Interpolating formulae for the GAM frequency and damping rate, based on the results of the gyrokinetic simulations, have been derived. Using these expressions, the influence of the temperature gradient on the damping rate is also investigated. Finally, the results are applied to the study of a real discharge of the ASDEX Upgrade tokamak.

show abstract

“…Analytical work [13] has shown that finite Larmor radius effects lead to the existence of global GAM eigenmodes, which could potentially explain the observations. Analytical work based on MHD [14] also found conditions for the existence of a global GAM. However, for the TCV experiments reported here, the single frequency regime is observed at frequencies below the local GAM frequency, whereas the above-mentioned analytical works predict a global GAM propagating at frequencies above the local GAM frequency.…”

Section: Introductionmentioning

confidence: 93%

Experimental observations of modes with geodesic acoustic character from the core to the edge in the TCV tokamak

Huang¹,

Coda²,

Merlo³

et al. 2018

Plasma Phys. Control. Fusion

View full text Add to dashboard Cite

The geodesic acoustic mode (GAM) is a coherently oscillating mode, related to the zonal flows that can regulate turbulence in magnetized toroidal plasmas. Modes possessing geodesic acoustic character have been widely observed in the TCV tokamak. A transition has been observed in the course of a single discharge from a continuum regime to a radially extended single-frequency regime. The mode has been also observed and characterized for the first time in the scrapeoff layer, primarily by Langmuir probes, suggesting a particle flow to the edge modulated at the mode frequency. These experimental observations are consistent with nonlinear global gyrokinetic simulations, reported in a companion paper [1]. These also suggest a possible coupling with radial avalanche phenomena.

show abstract

Global geodesic acoustic mode in a tokamak with positive magnetic shear and a monotonic temperature profile

Cited by 19 publications

References 26 publications

Investigation of zonal flows by using the collective scattering measurement of density fluctuations

Investigation of zonal flows by using the collective scattering measurement of density fluctuations

Linear gyrokinetic investigation of the geodesic acoustic modes in realistic tokamak configurations

Experimental observations of modes with geodesic acoustic character from the core to the edge in the TCV tokamak

Contact Info

Product

Resources

About