Peculiarities of electrode biasing experiments on the T-10 tokamak in regimes with Ohmic and ECR heating

Kirnev, G.; Budaev, V.P.; Dremin, M. M.; Gerasimov, E V; Grashin, S.A.; Khimchenko, L. N.; Krilov, S V; Pavlov, Yu.D.; Shelukhin, D. A.; Soldatov, S.; Timchenko, N.N.; Oost, G. Van; Vershkov, V.A.

doi:10.1088/0741-3335/45/4/302

Cited by 12 publications

(10 citation statements)

References 12 publications

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“…In this experiment only discharges with positive electrode bias were investigated. For negative bias the current is much lower, as expected, and in agreement with other works [3,5,10].…”

Section: Experimental Results and Data Analysissupporting

confidence: 93%

“…The pioneering work on biased electrode H-mode realized in 1989, in the CCT tokamak, by Taylor et al [2] opened the way to many other experiments in TEXTOR [3], TUMAN 3 [4] and PHAEDRUS [5] and more recently in TEXTOR [6,7], CASTOR [8,9], T-10 [10] and ISTTOK [11,12]. Emissive electrodes have been used with good success for obtaining negative biased H-mode [2,13,14] producing the necessary currents for arriving at the transition.…”

Section: Introductionmentioning

confidence: 99%

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Plasma confinement using biased electrode in the TCABR tokamak

et al. 2005

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Experimental data obtained on the TCABR tokamak (R = 0.61 m, a = 0.18 m) with an electrically polarized electrode, placed at r = 0.16 m, is reported in this paper. The experiment was performed with plasma current of 90 kA (q = 3.1) and hydrogen gas injection adjusted for keeping the electron density at 1.0 × 1019 m−3 without bias. Time evolution and radial profiles of plasma parameters with and without bias were measured. The comparison of the profiles shows an increase of the central line-averaged density, up to a maximum factor of 2.6, while Hα hydrogen spectral line intensity decreases and the C III impurity stays on the same level. The analysis of temporal behaviour and radial profiles of plasma parameters indicates that the confined plasma enters the H-mode regime. The data analysis shows a maximum enhanced energy confinement factor of 1.95, decaying to 1.5 at the maximum of the density, in comparison with predicted Neo–Alcator scaling law values. Indications of transient increase of the density gradient near the plasma edge were obtained with measurements of density profiles. Calculations of turbulence and transport at the Scrape-Off-Layer, using measured floating potentials and ion saturation currents, show a strong decrease in the power spectra and transport. Bifurcation was not observed and the decrease in the saturation current occurs in 50 µs.

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“…In this experiment only discharges with positive electrode bias were investigated. For negative bias the current is much lower, as expected, and in agreement with other works [3,5,10].…”

Section: Experimental Results and Data Analysissupporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Plasma confinement using biased electrode in the TCABR tokamak

et al. 2005

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“…V. In the past, many biasing experiments have focused on the impact of biasing on turbulence and the transport of particles and heat. 13,14,[25][26][27] We have observed a decrease in floating potential and I sat fluctuation amplitude ͑up to a frequency of 100 kHz͒ during bias, 8 but have yet to make the detailed turbulence and profile measurements necessary to draw firm conclusions about the impact of bias on transport. On the other hand, comparisons of QHS and mirror plasmas without bias have already demonstrated the reduction in orbit deviations from a flux surface 28 and the suppression of direct losses 29 in the QHS configuration, compared to the mirror case.…”

Section: -mentioning

confidence: 98%

Measurements and modeling of plasma flow damping in the Helically Symmetric eXperiment

et al. 2005

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Fusion Technology 27, 273 ͑1995͔͒ using a biased electrode to impulsively spin the plasma and Mach probes to measure the rotation. There is a distinct asymmetry between the spin-up when the bias is initiated and relaxation when the electrode current is broken. In each case, two time-scales are observed in the evolution of the plasma flow. These observations motivate the development of new neoclassical modeling techniques, including a new model where the fast increment of the electric field initiates the spin-up process. The flow in the quasisymmetric configuration rises more slowly and to a higher value than in a configuration with the quasisymmetry broken, and the rise time-scale is in reasonable agreement with the neoclassical spin-up model. The flows decay more slowly in the quasisymmetry configuration than in the configuration with the quasisymmetry broken, although the decay rates are significantly faster than the neoclassical prediction.

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“…However, after introducing a small emissive electrode, the efficiency of negative bias has been promoted greatly [21]. The results obtained in T-10 reveal that, the initial (pre-bias) states of plasma, such as the wall condition, may have an essential influence on the improved confinement performance [9].…”

Section: Introductionmentioning

confidence: 99%

The influence of electrode biasing on plasma confinement in the J-TEXT tokamak

Sun

Chen

Zhu

et al. 2013

Plasma Phys. Control. Fusion

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The influence of both positive and negative bias on global and plasma-edge parameters has been comparatively studied with a newly designed electrode biasing system in J-TEXT tokamak. Comparing to the 0V bias case, the global particle confinement of plasma is enhanced under bias with both polarities, with the increments of central line-averaged density and soft-X ray emission as well as the reduction of edge H α radiation level. The suppression of plasma-edge fluctuations and turbulent particle transport are obviously observed under bias, in different degrees with different polarities. The potential fluctuation amplitude is observed to be increased at the vicinity of limiter under positive bias, with the existence of a peaked low frequency mode (LFM) characterized as high coherence and near-zero cross-phase poloidally in the edge region, which is not found in the negative bias case. The poloidal correlation length of turbulence is greatly enhanced under bias with both polarities, and shows a positive correlation with the amplitude of poloidal phase velocity, which is mainly driven by the local J r × B torque at plasma edge under bias. The characteristic parameters of intermittent events (i.e. blobs), including amplitude, radial velocity, related particle flux and radial size, are decreased dramatically under bias in the edge region.

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Peculiarities of electrode biasing experiments on the T-10 tokamak in regimes with Ohmic and ECR heating

Cited by 12 publications

References 12 publications

Plasma confinement using biased electrode in the TCABR tokamak

Plasma confinement using biased electrode in the TCABR tokamak

Measurements and modeling of plasma flow damping in the Helically Symmetric eXperiment

The influence of electrode biasing on plasma confinement in the J-TEXT tokamak

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