Ambipolar potential effect on a drift-wave mode in a tandem-mirror plasma

Mase, A.; Jeong, Jun‐Ho; Itakura, A.; Ishii, K.; Inutake, M.; Miyoshi, S.

doi:10.1103/physrevlett.64.2281

Cited by 53 publications

(42 citation statements)

References 13 publications

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“…The radial electric field E arising from the potential causes an E × B plasma rotation in the direction of the ion diamagnetic drift velocity, which may enhance instabilities, such as rotational flute and drift-wave modes, and degrade radial confinement. However, present studies show the suppression of low-frequency fluctuations of the density and the potential during axial confining potential formation during plug-ECH (P-ECH) [1][2][3][4][5][6]. Earlier works by Sanuki [7] and Chaudhry et al [8] discussed the effects of the ambipolar potential on the stability of drift waves.…”

Section: Introductionmentioning

confidence: 56%

“…1). The details on GAMMA 10 are provided elsewhere [1][2][3][4][5][6]. The x-axis and y-axis are perpendicular to the magnetic field in the vertical and horizontal directions, respectively.…”

Section: Tandem Mirror Gamma 10mentioning

confidence: 99%

“…In the tandem mirror GAMMA 10, an electrostatic potential for improving axial confinement is created by applying electron cyclotron resonance heating (ECH) in the end mirrors (plug/barrier cells) [1][2][3][4][5][6]. Two types of instability, a rotationally driven mode with the lowest azimuthal mode number and a drift-wave mode with high azimuthal mode numbers, are observed during the existence of confining potentials.…”

Section: Introductionmentioning

confidence: 99%

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Study of Fluctuation Suppression during Potential Formation in the Tandem Mirror GAMMA 10

Yoshikawa

Miyata

Mizuguchi

et al. 2010

Plasma and Fusion Research

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In the tandem mirror GAMMA 10, plasma confinement is achieved by not only a magnetic mirror configuration but also high potentials in both end regions. Before plug electron cyclotron resonance heating (P-ECH) was applied, drift-type fluctuations were observed in potential and density measurements. Potential and density fluctuation suppression during potential formation by the application of P-ECH was clearly observed using a gold neutral beam probe (GNBP) system. We study the relationship between the suppression levels of potential fluctuations and the effects of the produced potentials by varying the applied ECH power. Moreover, the particleflux-related values obtained by the phase difference between the potential and density fluctuations are measured using the GNBP. We can clearly show that radial anomalous transport induces radial particle transport, which decreases the plasma stored energy.

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Section: Introductionmentioning

confidence: 56%

Section: Tandem Mirror Gamma 10mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Study of Fluctuation Suppression during Potential Formation in the Tandem Mirror GAMMA 10

Yoshikawa

Miyata

Mizuguchi

et al. 2010

Plasma and Fusion Research

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“…In addition to the instabilities discussed above, it is expected that the SOL plasma would be unstable to drift-interchange modes driven by density/temperature gradients and the (moderate) field line curvature, as observed experimentally in a tandem mirror experiment with very similar plasma parameters [15]. Also, at moderate/high β finite Larmor radius (FLR) effects do not always restrict interchange instability to < 1 as discussed in [16].…”

Section: Introductionmentioning

confidence: 88%

Control of ion gyroscale fluctuations via electrostatic biasing and sheared E×B flow in the C-2 field reversed configuration

Schmitz¹,

Ruskov²,

Deng³

et al. 2016

AIP Conference Proceedings

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Abstract. Control of radial particle and thermal transport is instrumental for achieving and sustaining well-confined high-β plasma in a Field-Reversed Configuration (FRC). Radial profiles of low frequency ion gyro-scale density fluctuations (0.5 ≤ kρ s ≤ 40), consistent with drift-or drift-interchange modes, have been measured in the scrape-off layer (SOL) and core of the C-2 Field-Reversed Configuration (FRC), together with the toroidal ExB velocity. It is shown here that axial electrostatic SOL biasing controls and reduces gyro-scale density fluctuations, resulting in very low FRC core fluctuation levels. When the radial ExB flow shearing rate decreases below the turbulence decorrelation rate, fluctuation levels increase substantially, concomitantly with onset of the n=2 instability and rapid loss of diamagnetism. Low turbulence levels, improved energy/particle confinement and substantially increased FRC life times are achieved when ExB shear near the separatrix is maintained via axial SOL biasing using an annular washer gun.

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“…[1][2][3][4][5][6][7] The measurement of the fluctuation in the plasma is important for studying the improvement in plasma confinement by the formation of a plasma confinement potential. 1,2,8 Density fluctuation is observed using microwaves, such as interferometer, [8][9][10][11] reflectometry 8 and Fraunhofer diffraction ͑FD͒ methods, 9,10 and electrostatic probes. 11 Ultrashort-pulse reflectometry has an advantage of detecting fluctuation locally.…”

Section: Introductionmentioning

confidence: 99%

Electron density fluctuation measurements using a multichannel microwave interferometer in GAMMA 10

Yoshikawa

Shima

Matsumoto

et al. 2006

Review of Scientific Instruments

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Measurement of fluctuation in plasma is important for studying the improvement in plasma confinement by the formation of the plasma confinement potential. The density fluctuation is observed by microwaves by methods such as interferometry, reflectometry and Fraunhofer diffraction method. We have constructed a new multichannel microwave interferometer to measure the plasma density and fluctuation radial profiles in a single plasma shot. We successfully measured the time-dependent density and line-integrated density fluctuation radial profiles in a single plasma shot using the multichannel microwave interferometer. Thus, we have developed a useful tool for studying the improvement in plasma confinement by the formation of plasma confinement potential.

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Ambipolar potential effect on a drift-wave mode in a tandem-mirror plasma

Cited by 53 publications

References 13 publications

Study of Fluctuation Suppression during Potential Formation in the Tandem Mirror GAMMA 10

Study of Fluctuation Suppression during Potential Formation in the Tandem Mirror GAMMA 10

Control of ion gyroscale fluctuations via electrostatic biasing and sheared E×B flow in the C-2 field reversed configuration

Electron density fluctuation measurements using a multichannel microwave interferometer in GAMMA 10

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