Dynamics of the L - H transition

Rozhansky, V.; Тендлер, М.; Voskoboinikov, S. P.

doi:10.1088/0741-3335/38/8/031

Cited by 26 publications

(48 citation statements)

References 7 publications

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“…force balance equation [7,34] given in eq.5. It is seen from (5), that the E r follows the contributions from v tor and v pol , dominated by v pol (cf.…”

Section: Data and First Resultsmentioning

confidence: 99%

Charge exchange recombination spectroscopy on a diagnostic hydrogen beam—measuring impurity rotation and radial electric field at the tokamak TEXTOR

Coenen

Schweer

Clever

et al. 2010

J. Phys. B: At. Mol. Opt. Phys.

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To cite this version:J W Coenen, M Clever, U Samm, O Schmitz, B Schweer, et al.. Charge exchange recombination spectroscopy on a diagnostic hydrogen beammeasuring impurity rotation and radial electric field at the tokamak TEXTOR. Journal of Physics B: Atomic, Molecular and Optical Physics, IOP Publishing, 2010, 43 (14) Abstract. In this work we present an overview on the CXRS diagnostic operated with the modulated diagnostic hydrogen beam at the Tokamak TEXTOR. The diagnostic setup combines two observation systems used for the measurement of the poloidal (v pol ) and the toroidal (v tor ) ion velocity component.At TEXTOR a differential Doppler spectroscopy approach (accurate absolute rotation scale) is combined with the high intensity and spatial resolution of a direct imaging system necessary for accurate poloidal rotation measurements on a shot by shot basis. This setup allows the full utilization of the a 2D CCD detector in the spectral and radial direction. In case of the poloidal system this allows spatial resolution in the range of mm to cm depending on the intensity requirements for the velocity. The toroidal system is comprised of a fiber-optic array. The combination of the two measurements with a low power diagnostic beam can in principal be operated during any available heating scenario without interfering with the discharge. Time resolution is limited by the necessary averaging process, typically a stable plateau of 3 s during a TETXOR pulse is used. The TEXTOR tokamak has the ability to apply momentum input with two tangential neutral beam heating injectors, allowing for measurements under various heating and momentum input scenarios. With the presented diagnostic half the plasma minor radius at a spatial resolution of ∼ 1cm is covered. With the CVI line at 529.053 nm an accuracy of 0.7km/s for the poloidal and ∼ 5 km/s for the toroidal system is given. The temperature is measured with an accuracy of a few eV. The presented work illustrates the capability of the system during a toroidal momentum scan, showing the self-consistent determination of the radial electric field from experimental CXRS data based on the radial force balance.Confidential: not for distribution.

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“…force balance equation [7,34] given in eq.5. It is seen from (5), that the E r follows the contributions from v tor and v pol , dominated by v pol (cf.…”

Section: Data and First Resultsmentioning

confidence: 99%

Charge exchange recombination spectroscopy on a diagnostic hydrogen beam—measuring impurity rotation and radial electric field at the tokamak TEXTOR

Coenen

Schweer

Clever

et al. 2010

J. Phys. B: At. Mol. Opt. Phys.

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“…The key element in the transition to high H-mode is the origin of a strong radial electric field near the separatrix and the suppression of a turbulence level by a strong poloidal rotation (see reviews [1][2][3][4]). As a result, the transport coefficients are strongly reduced, and the edge transport barrier (ETB) is formed.…”

Section: Radial Electric Field In the Edge Plasmamentioning

confidence: 99%

“…The reason for this is the fact that in the parallel momentum balance equation for ions the classical (neoclassical) ion viscosity dominates over the turbulent perpendicular transport of the parallel momentum. Indeed the averaged parallel momentum balance equation has the form [4][5][6] …”

Section: Radial Electric Field In the Edge Plasmamentioning

confidence: 99%

Drifts, Currents, and Radial Electric Field in the Edge Plasma with Impact on Pedestal, Divertor Asymmetry and RMP Consequences

Rozhansky

2014

Contrib. Plasma Phys.

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Methanol is considered a promising liquid fuel in context with electrochemical energy conversion and storage for mobile applications. It is shown here that a direct methanol fuel cell can be used for spontaneous charging and discharging a supercapacitor (SC) for intermediate storage of chemical energy. Thereby, protons and electrons of the methanol‐derived hydrogen are stored separately in the electrical double layer of the SC electrode. The charging and discharging of this fuel cell–SC hybride device is investigated in experiments of spontaneous conditions (closed circuit) and also under externally enforced constant voltage sweep rate (cyclic voltammetry) and under constant current conditions. Alternatively, gas phase hydrogen is generated from methanol in an electro‐reforming process. When more efficient anode electrocatalysts become available this may become the method of choice for on‐board and on demand hydrogen production in mobile applications.

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“…Since the radial electric field in the SOL is positive and the ion pressure is decreasing with radius, the PS flux is maximal by absolute value at the outer and inner equatorial midplanes and is zero at the top and bottom. The second one is the flux compensating the E × B drift in the radial electric field to keep the same poloidal flux in the presence of drifts as without drifts [1]. The corresponding value is…”

Section: Parallel Flowsmentioning

confidence: 99%

“…In recent years it has been recognized that the impact of electric fields and the corresponding E × B drifts are rather important for the redistribution of plasma and impurities at the edge of a tokamak [1]. At present it is also well understood that the key element in the L-H transition physics is the origin of a strong radial electric field and the suppression of a turbulence fluctuation level by a strong poloidal rotation in the E × B fields (see reviews [2]- [4]).…”

Section: Introductionmentioning

confidence: 99%

Modelling of the Edge Plasma with Account of Self-Consistent Electric Fields

Rozhansky

2006

Contrib. Plasma Phys.

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Recent results on the simulation of the edge plasma parameters are discussed with emphasis on the role of self-consistent electric fields. It is demonstrated that simulation with B2SOLPS5.0 code as well as with the other codes is consistent with the neoclassical nature of the radial electric field in the core region 1-2 cm inside the separatrix. Near the separatrix the viscous layer exists, where the impact of the parallel fluxes of the SOL is important and electric field deviates from the neoclassical value. It is shown that the experimental dependence of the L-H transition threshold on the local and global plasma parameters might be explained on the basis of the simulations. The impact of the geometrical factors on the radial electric field structure is discussed. It is shown that the change of the parallel fluxes in the scrape-off layer, which are transported through the separatrix due to turbulent viscosity and diffusivity, should result in variation of the radial electric field. The parallel (toroidal) fluxes in the SOL and mechanisms of their formation are analyzed for different geometry and directions of the magnetic field. Currents in the SOL and in the core region are analyzed and compared with the analytical predictions.

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Dynamics of the L - H transition

Cited by 26 publications

References 7 publications

Charge exchange recombination spectroscopy on a diagnostic hydrogen beam—measuring impurity rotation and radial electric field at the tokamak TEXTOR

Charge exchange recombination spectroscopy on a diagnostic hydrogen beam—measuring impurity rotation and radial electric field at the tokamak TEXTOR

Drifts, Currents, and Radial Electric Field in the Edge Plasma with Impact on Pedestal, Divertor Asymmetry and RMP Consequences

Modelling of the Edge Plasma with Account of Self-Consistent Electric Fields

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