Multi-Diagnostic Approach To Geodezic Acoustic Mode Study

Yashin, A. V.

doi:10.22323/1.240.0175

Cited by 3 publications

(5 citation statements)

References 8 publications

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“…Similar observations of GAMs existing only near the separatrix were made earlier in the DIII D tokamak [19] and in the spherical MAST torus [9]. In limiter tokamaks GAMs are also located near the last closed flux surface [12,13]. As can be seen in figure 4 there is no significant change in the GAM frequency for the different cutoff layer positions, although the electron temperature and sound velocity are changed more than twice within this radial interval.…”

Section: Conditions For Gam Existence and Gam Featuressupporting

confidence: 83%

“…The GAM frequency is estimated to be significantly lower than the frequency calculated using the usual formula excluding elongation and finite aspect ratio and it corresponds to the frequency as predicted by the kinetic approach and by modeling [7]. The GAM narrow location near the separatrix is similar to the GAM location as observed in the DIII-D tokamak [19] or in the TUMAN-3 M tokamak with limiter [13]. It was discovered that the transition to the limitcycle oscillation regime occurs with a gradual increase of the GAM oscillation amplitude.…”

Section: Discussionsupporting

confidence: 51%

“…As GAMs manifest themselves as E × B velocity oscillations they can be detected by Doppler reflectometry (DR) [10]. DR was successfully used for GAM detection in the divertor tokamaks ASDEX-Upgrade [10] and TCV [11], and in the limiter tokamaks Tore Supra [12] and TUMAN-3 M [13]. Recently zonal flows have been studied in the DIII-D tokamak using a multichannel DR [2].…”

Section: Introductionmentioning

confidence: 99%

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Geodesic acoustic mode observations in the Globus-M spherical tokamak

et al. 2014

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The results of geodesic acoustic mode (GAM) studies in the spherical torus Globus-M via Doppler reflectometry are presented. The intermittent character of the GAM evolution is similar to the limit-cycle oscillation behavior of zonal flows. The evident correlation between the GAM rotational velocity and both Dα emission and plasma density oscillations is exhibited and discussed. The obtained experimental results are compared with those from tokamaks with large aspect ratios.

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Section: Conditions For Gam Existence and Gam Featuressupporting

confidence: 83%

Section: Discussionsupporting

confidence: 51%

Section: Introductionmentioning

confidence: 99%

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Geodesic acoustic mode observations in the Globus-M spherical tokamak

et al. 2014

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“…Here we explore GAMs in discharges with and without trans ition to the Ohmic H-mode [19] with specific attention to the GAMturbulence interplay and dynamics. Preliminary results have been reported in [20]. The Doppler backscattering (DBS) (also known as Doppler reflectometry) has been employed as the main diagnostic tool allowing measurement of the E × B velocity [15,[21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37].…”

Section: Introductionmentioning

confidence: 99%

GAM observation in the TUMAN-3M tokamak

Bulanin

Askinazi

Belokurov

et al. 2016

Plasma Phys. Control. Fusion

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Results of an experimental study of geodesic acoustic modes (GAM) in the TUMAN-3M tokamak are reported. With Doppler backscattering (DBS) the basic properties of the GAM such as frequency, conditions for the GAM existence and the GAM radial location have been identified. The two-frequency Doppler reflectometer system was employed to reveal an interplay between low frequency sheared poloidal rotation, ambient turbulence level and the GAM intensity. Bicoherence analysis of the DBS data evidences the presence of a nonlinear interaction between the GAM and plasma turbulence.

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“…The geodesic acoustic mode (GAM) is still actively explored in the attempt to determine their nonlinear interaction with plasma drift turbulence [1]. It has been shown that GAMs, -oscillations of the radial electric field or the E × B flowscan be detected by various diagnostics such as HIBP [2][3][4], Langmuir probes [5][6][7][8][9][10][11] or microwave methods [12][13][14][15][16][17][18], respectively. The application of various diagnostics is also required to identify GAM oscillations of the plasma density and the magnetic field, as predicted by theories [19][20][21].…”

Section: Introductionmentioning

confidence: 99%

Geodesic acoustic mode investigation in the spherical Globus-M tokamak using multi-diagnostic approach

et al. 2015

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Owing to the active researches of intermediate regime which is known as limit cycle oscillation (LCO) regime, it is important to investigate oscillations of velocity of zonal flows, plasma density and magnetic field simultaneously. The geodesic acoustic mode (GAM) investigations using multi-diagnostic were carried out on the spherical tokamak Globus-M (R = 0.36 m, a = 0.24 m, Ip = 150 kA, BT = 0.3 T). Variation of GAM intensity showed features of LCO regime. The key implement for researches was a method of Doppler microwave backscattering, or Doppler reflectometry (DR). The diagnostic consisted of two Doppler reflectometers, which were apart in poloidal direction. Oscillations of plasma density at GAM frequencies were investigated using electrostatic probes and detectors of Dα intensity emission, which were detected at different lines of sight. Structure of magnetic field perturbation has been investigated using poloidal and toroidal Mirnov probe arrays. Correlation analysis shown that the structure of ExB velocity oscillations had corresponded to n=0, m=0. The main structure of density fluctuations at GAM frequency had n=0, m=0 mode numbers. Besides the n=0, m=1 component is also presented. The mode structure for magnetic field disturbance was established. To interpret an origin of plasma density global perturbation at GAM frequency plausible model was suggested.

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Multi-Diagnostic Approach To Geodezic Acoustic Mode Study

Cited by 3 publications

References 8 publications

Geodesic acoustic mode observations in the Globus-M spherical tokamak

Geodesic acoustic mode observations in the Globus-M spherical tokamak

GAM observation in the TUMAN-3M tokamak

Geodesic acoustic mode investigation in the spherical Globus-M tokamak using multi-diagnostic approach

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