Divertors and Impurity Control Control (Report on the IAEA Technical Committee Meeting, Garching, 1981)

Keilhacker, M.; Daybelge, U.

doi:10.1088/0029-5515/21/11/018

Cited by 32 publications

(37 citation statements)

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“…This was demonstrated for the first time also for the ion energy transport. The results reported here are consistent with similar observations of the poloidally asymmetric particle [8][9][10][11][12][18][19][20]) and electron energy [16][17][18][19][20] transport reported earlier.…”

supporting

confidence: 93%

“…[16][17][18]). Measurements in ASDEX and PDX in a double-null divertor configuration have demonstrated that the outer scrape-off layer carries about five times more particles and energy to the divertor as the inner scrape-off layer, providing strong evidence that the cross-field particle and energy transport is larger on the outboard side of the plasma [19]. Similar observations were reported from T-10 and were associated with balloning-like cross-field transport asymmetries [9].…”

Section: Introductionsupporting

confidence: 70%

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Comparison of scrape-off layer profiles in outboard-versus inboard-limited plasmas in Tore Supra

Kočan¹,

Gunn

2010

Plasma Phys. Control. Fusion

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In the Tore Supra tokamak, the scrape-off layer profiles of discharges limited either on the inboard or on the outboard side are compared. Inboard-limited discharges are characterized by substantially longer SOL e-folding lengths of ion and electron temperatures and electron density measured near the top of the plasma, providing strong evidence that the ion and electron energy transport across the SOL is enhanced on the outboard side, similar to the particle transport. The parallel heat flux density extrapolated to the last closed flux surface is found to be inversely proportional to its e-folding length in the SOL. The outboard limiters thus receive higher and more peaked heat loads than the inboard limiters. These results are important for the optimization of the plasma start-up scenario and design of the first wall in ITER.PACS 52.25.Fi, 52.25.Xz, 52.35.Ra, 52.55.Fa, 52.70.Ds IntroductionIn tokamaks, the intermittent expulsion of magnetic-field-aligned plasma filaments from the last closed flux surface (LCFS) is responsible for a large fraction of the effective radial transport to the wall [1][2][3][4][5][6]. Filament propagation appears to be governed by a ballooning-type instability in the unfavourable magnetic curvature region on the low field side. As the filaments propagate outward, they also expand freely along the magnetic field lines, driving pressure-driven field-direction-independent parallel flows. Mach probe measurements in many divertor tokamaks (e.g. [7] and references therein) show flow patterns consistent with this model (i.e. stagnant flow poloidally approximately halfway between the outer midplane and the X-point), in which the filaments can be seen as an important particle source in the scrape-off layer (SOL). Similar observations in limiter tokamaks [8][9][10][11][12] prove that enhanced radial particle transport on the outboard side of the plasma is a universal phenomenon, independent of the presence of an X-point divertor. The enhancement of the radial particle transport on the outboard side of the limiter plasmas was confirmed by the 3D fluid turbulence code TOKAM-3D [13]. When the plasma contact point is on the inboard limiters, the filaments propagate freely out to the wall, filling all the available volume outside the LCFS and leading to a broad SOL with nearly flat density profiles. On the other hand, it was demonstrated [12] that outboard modular limiters suppress the radial particle transport when they are near the LCFS, leading to a very thin SOL. It is probable [8] that the limiters act as simple mechanical barriers that intercept the parallel particle flux in the region in which the enhanced radial convection.

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supporting

confidence: 93%

Section: Introductionsupporting

confidence: 70%

Comparison of scrape-off layer profiles in outboard-versus inboard-limited plasmas in Tore Supra

Kočan¹,

Gunn

2010

Plasma Phys. Control. Fusion

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“…This mechanism of cross-field plasma transport was invoked in earlier papers in order to explain various aspects of power and particle flow at the plasma edge. The 'inside-outside asymmetry of particle and energy flow' was mentioned in [17] as an explanation for a much higher, by factor 5, particle and energy flows to the outside SOL than to the inner one in double-null divertor operation in ASDEX and PDX. Later, 'poloidally asymmetric diffusion' favouring outer, low-field side, with D ⊥ there exceeding that on the inner side by factor 5-30, was established by using poloidally distributed probe array in Alcator C, which showed large poloidal asymmetries of n e , T e and radial density e-folding length in the SOL [18].…”

Section: Drift Flows and Flows Due To 'Ballooning' Feature Of Cross-fmentioning

confidence: 99%

A possible role of radial electric field in driving parallel ion flow in scrape-off layer of divertor tokamaks

Chankin¹,

Coster²,

Asakura³

et al. 2007

Nucl. Fusion

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The radial electric field in known to be one of the drivers of parallel ion flow in the SOL. It contributes to the ion Pfirsch-Schlüter flow and also determines the 'return parallel flow' that can arise to compensate poloidal E×B drift. It was established recently that 2D fluid codes EDGE2D and SOLPS underestimate the predicted E r in the SOL compared to experimentally measured values. The underestimate is likely to be related with kinetic effects of parallel transport by heat-carrying electrons. The present work demonstrates that this underestimate can be responsible for the large discrepancy between measured and simulated parallel ion flows in the SOL observed in a number of experiments. Were the radial electric field modelled correctly by the codes, a significant increase in the predicted Mach number of the parallel ion flow could be expected. For the part of the ion flow that depends on the toroidal field direction, this would greatly reduce, or even possibly eliminate, the difference between the experiment and model, as concluded from the comparison between measured and simulated radial electric fields and Mach numbers of the parallel ion flow in JET and ASDEX Upgrade.2

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“…The overbar notation diat indicated an averaging operation along Z in eqs. (9) and (10) has now been dropped. Eliminating the E r terms by combining (11) and (12) where E r = -V r <I>,…”

Section: A Radial Fluxes and Currentsmentioning

confidence: 99%

“…On the other hand, data from many tokamaks devices indicate that particle and energy fluxes from the plasma core are poloidally asymmetric, showing higher cross field transport on the large major radius edge of the torus [8,9]. Thus, it may not be necessary to form a potential barrier around the full periphery of the plasma but only on the outside half of me torus where the cross-field transport is high.…”

Section: Introductionmentioning

confidence: 99%

Analysis of an m = 1 electrostatic barrier scrape-off layer as a technique for reducing and controlling the particle and energy losses on the large major radius edge of tokamak

LaBombard¹,

Conn²

1988

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Th's report was prepared m an account of work sponsored by an agency ol the United Stales Government Neither the United State!. Government nor any agency thereof, not any of the,r employees mattes any warranty, express or implied, or assumes any legal handily or responsi bility, ' for the accuracy, completeness, or usefulness of any information, apparatus, product, ot process disclosed, or reptcscnls that its use would not infringe privately owned rijltlt. Refer ence herein to any specific commercial producl. process, ot service by trade name, trademark, manufacturer, ot otherwise docs not necessarily constitute or imply its endorsement, recom mendation, or favoring by the Untied Stales Government or any agency thcteof. The views and opinions of authors expressed herein do nol necessarily slate 01 reflect ihosc of the United Stales Government oi any agency thereof. OCLA-PPG-H86 Analysis of an m-l FW, .

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Divertors and Impurity Control Control (Report on the IAEA Technical Committee Meeting, Garching, 1981)

Cited by 32 publications

References 0 publications

Comparison of scrape-off layer profiles in outboard-versus inboard-limited plasmas in Tore Supra

Comparison of scrape-off layer profiles in outboard-versus inboard-limited plasmas in Tore Supra

A possible role of radial electric field in driving parallel ion flow in scrape-off layer of divertor tokamaks

Analysis of an m = 1 electrostatic barrier scrape-off layer as a technique for reducing and controlling the particle and energy losses on the large major radius edge of tokamak

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