Analytical solutions for global geodesic acoustic modes in tokamak plasmas

Ilgisonis, V. I.; Konovaltseva, Ludmila V.; Lakhin, V. P.; Sorokina, E. A.

doi:10.1134/s1063780x14110038

Cited by 16 publications

(36 citation statements)

References 25 publications

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“…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: 76%

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

Shen

Lan

et al. 2015

Nucl. Fusion

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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.

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Section: The Geodesic Acoustic Mode In the Velocity Fluctuationsmentioning

confidence: 76%

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

Shen

Lan

et al. 2015

Nucl. Fusion

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“…This is not the case of the experiments in the modern tokamaks where the local GAM frequency is monotonic as in figure 6. Some recent theoretical results [26,27] predict the global GAMs in discharges with positive magnetic shear and monotonic temperature profile. However, in this theory the mode originates from the centre, while in our experiment the mode seems to be excited at the edge.…”

Section: Discussionmentioning

confidence: 99%

The features of the global GAM in OH and ECRH plasmas in the T-10 tokamak

et al. 2015

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Zonal flows and their high-frequency counterpart, the geodesic acoustic modes (GAMs) are considered as a possible mechanism of the plasma turbulence self-regulation. In the T-10 tokamak GAMs have been studied by the heavy ion beam probing and multipin Langmuir probes. The wide range of the regimes with Ohmic, on-axis and off-axis electron cyclotron resonance heating (ECRH) were studied (B t = 1.5-2.4 T, I p = 140-300 kA, ne = (0.6-6.0) × 10 19 m −3 , P EC < 1.2 MW). It was shown that GAM has radially homogeneous structure and poloidal m = 0 for potential perturbations. The local theory predicts that f GAM ∼ √ T /m i /R, that means the frequency increases with the decrease of the minor radius. In contrast, the radial distribution of experimental frequency of the plasma potential and density oscillations, associated to GAM, is almost uniform over the whole plasma radius, suggesting the features of the nonlocal (global) eigenmodes. The GAM amplitude in the plasma potential also tends to be uniform along the radius. GAMs are more pronounced during ECRH, when the typical frequencies are seen in the narrow band from 22 to 27 kHz for the main peak and 25-30 kHz for the higher frequency satellite. GAM characteristics and the range of GAM existence are presented as functions of T e , density, magnetic field and P EC .

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“…На глобальный характер ГАМ также указывает отсутствие радиальной зависимости у амплитуды и частоты ГАМ [10]. В пользу глобального характера ГАМ свидетельствуют не только результаты, полученные на нескольких установках и описанные во Введении, но и результаты теоретических работ [28,29].…”

Section: обсуждение результатовunclassified

Long-Distance Correlations of Geodesic Acoustic Modes in T-10

Melnikov¹,

Eliseev²,

Лысенко³

et al. 2015

PAST-TF

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Геодезические акустические моды (ГАМ) рассматриваются в качестве механизма самостабилизации турбулентности. На токамаке Т-10 ГАМ на электростатическом потенциале и флуктуации плотности одновременно исследовались с помощью зондирования пучком тяжёлых ионов (ЗПТИ) и корреляционной рефлектометрии (КР). Изучались режимы с омическим и электронноциклотронным (ЭЦ) нагревом. ГАМ более выражены во время ЭЦ-нагрева, при этом их типичные частоты лежат в узкой полосе 22-27 кГц для основного пика и 25-30 кГц для более высокочастотного сателлита. Локальные значения электрического потенциала и флуктуаций демонстрируют заметную когерентность и постоянный фазовый сдвиг в диапазоне частот ГАМ. Существование дальних пространственных (1/4 тора) корреляций потенциала и плотности для ГАМ означает, что ГАМ является глобальной модой, что впервые показано на токамаке.

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Analytical solutions for global geodesic acoustic modes in tokamak plasmas

Cited by 16 publications

References 25 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

The features of the global GAM in OH and ECRH plasmas in the T-10 tokamak

Long-Distance Correlations of Geodesic Acoustic Modes in T-10

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