Radial electric field evolution in the vicinity of a rotating magnetic island in the TUMAN-3M tokamak

Askinazi, L. G.; Golant, V.E.; Kornev, V. A.; Лебедев, С. В.; Tukachinsky, A. S.; Vildjunas, M. I.; Zhubr, N. A.

doi:10.1088/0741-3335/48/5a/s07

Cited by 30 publications

(30 citation statements)

References 9 publications

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“…1). Note a significant positive perturbation in the potential during the MHD activity burst in the interval between t = 38 and 45 ms, which was considered in detail previously [8,9]. The MHD oscillation frequency during the MHD activity burst amounts to 5-12 kHz and is significantly differ ent from the GAM frequency (~28-32 kHz).…”

Section: Evolution Of Geodesic Acoustic Mode In Ohmic H Mode In Tumanmentioning

confidence: 65%

Evolution of geodesic acoustic mode in ohmic H-mode in TUMAN-3M tokamak

et al. 2012

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The concept of geodesic acoustic mode (GAM) was introduced in 1968 by Winsor et al. [1] in order to explain strong low frequency oscillations observed in the Model C stellarator. Since then, similar oscilla tions have been observed in many toroidal installa tions. In recent years, GAMs and other zonal flows (GAMs being a particular kind of these) attracted much attention and have been extensively studied both experimentally and theoretically [2,3] in respect of their influence on the plasma confinement. While not participating directly in the radial transport of energy and particles, GAMs can nevertheless influence the level of turbulence, the intensity of turbulent transport in plasma, and eventually the efficiency of plasma and energy confinement. Interrelation of the background turbulence, GAMs, and confinement regime was demonstrated by experiments on many toroidal devices and, in particular, in recent experiments on the AUG tokamak [4].This Letter presents the results of experiments on the TUMAN 3M tokamak [5] in a regime with the ohmic LH transition for the following parameters of plasma: minor radius, 22 cm; major radius, 52 cm; tor oidal magnetic field, 0.7 T; plasma current, 130 kA; safety factor, 2.5-3.3; average plasma density: from (0.8-0.9) × 10 19 m -3 in L mode to (3-4) × 10 19 m -3 in H mode. Figure 1 shows the temporal variation of some parameters in the H mode. Oscillations of the plasma potential at the GAM frequency were observed at the initial stage of discharge using the heavy ion beam probing (HIBP) techniques [6,7]. In these experi ments, the HIBP measurements were performed using 70 keV K + probing ions. The point of secondary ion ization of the injected ions was situated near the plasma column center and shifted relative to the initial position as a result of the temporal variation of the tor oidal magnetic field: r HIBP ~ 2.7 cm at t = 35 ms;Abstract-The behavior of a geodesic acoustic mode (GAM) in the TUMAN 3M tokamak has been exper imentally studied using the heavy ion beam probing technique. Oscillations of the electric potential under the action of a GAM localized at the plasma periphery have been detected. The GAM was observed in the regime of low confinement (L mode) with low plasma density (~0.8 × 10 19 m -3 ) and disappeared upon the transition to a high confinement regime (H mode). The possible role of GAM as a precursor of the improved confine ment (LH transition) is discussed.

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Section: Evolution Of Geodesic Acoustic Mode In Ohmic H Mode In Tumanmentioning

confidence: 65%

Evolution of geodesic acoustic mode in ohmic H-mode in TUMAN-3M tokamak

et al. 2012

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“…Negative E r was registered only at the initial stage of the biase and it reached 5 V/cm. During the radial electric variations MHD activities excited such these influences have been seen experimentally in the TUMAN-3M tokamak 4 . It is important to note that the increase in MHD activities are observed in all 12 coils, but in the Fig.…”

Section: Experiments and Discussionmentioning

confidence: 79%

“…Edge biasing experiments have been investigated to improve plasma confinement [1][2][3][4][5] and modifying edge transport and turbulence, but the effects of biasing in edge fluctuations and its levels are different with bias voltage and devices operation. Experimental measurements of the radial electric field in the edge region and scrape-off layer (SOL) have been done in different tokamaks and are summarized in Ref.…”

Section: Introductionmentioning

confidence: 99%

The effect of limiter biasing on the plasma edge rotation and MHD activities

Lahazi

Khorshid

Ghoranneviss

2014

Int. J. Mod. Phys. Conf. Ser.

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Plasma edge rotations and magnetohydrodynamic behaviors have been studied during radial electric field variations in IR-T1 tokamak. An external positive limiter bias has been used as an external radial electric field. The profiles of radial electric field, floating potential, poloidal and toroidal rotation velocities and MHD activities have been studied during positive limiter bias. The poloidal and toroidal velocities reduced when the bias was applied and their fluctuations on the plasma edge became smoother furthermore A significant excitation in dominant mode (4, 1) oscillation amplitude and a sharp decrease in magnetic island rotation frequency have been seen.

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“…The reason for this behavior is not yet entirely clear to us. One possibility is the effect of inversion of the radial electric field, as observed in TUMAN-3M [31]. As it is well-known, the radial component of the ambipolar electric field plays a substantial role on plasma rotation and magnetic island evolution [12,32].…”

Section: Disruptive Dischargesmentioning

confidence: 99%

Interplay between intrinsic plasma rotation and magnetic island evolution in disruptive discharges

et al. 2016

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The behavior of the intrinsic toroidal rotation of the plasma column during the growth and eventual saturation of m/n = 2/1 magnetic islands, triggered by programmed density rise, has been carefully investigated in disruptive discharges in TCABR. The results show that, as the island starts to grow and rotate at a speed larger than that of the plasma column, the angular frequency of the intrinsic toroidal rotation increases and that of the island decreases, following the expectation of synchronization. As the island saturates at a large size, just before a major disruption, the angular speed of the intrinsic rotation decreases quite rapidly, even though the island keeps still rotating at a reduced speed. This decrease of the toroidal rotation is quite reproducible and can be considered as an indicative of disruption.

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Radial electric field evolution in the vicinity of a rotating magnetic island in the TUMAN-3M tokamak

Cited by 30 publications

References 9 publications

Evolution of geodesic acoustic mode in ohmic H-mode in TUMAN-3M tokamak

Evolution of geodesic acoustic mode in ohmic H-mode in TUMAN-3M tokamak

The effect of limiter biasing on the plasma edge rotation and MHD activities

Interplay between intrinsic plasma rotation and magnetic island evolution in disruptive discharges

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