Probe edge measurements in JET X-point plasmas for various heating and plasma conditions

Tagle, J.A.; Clement, S.; Loarte, A.; Kock, L. de; Harbour, P.J.; O’Brien, Dennis P.; Erents, S.K.; Janeschitz, G.; Nicholson, C.; Vince, J.

doi:10.1016/s0022-3115(06)80069-3

Cited by 10 publications

(4 citation statements)

References 12 publications

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“…λ n ∼ q c 95 , where c = 0.35-1.5 (McCormick et al 1992a, b, Watkins et al 1992, Asakura et al 1995a. Where measured, most machines do indeed find λ n ∼ λ T to within a factor of three (Murmann and Huang 1985, Tagle et al 1992, Davies et al 1995, LaBombard et al 1995a, Asakura et al 1995a. There are, however, conflicting results as to the quantitative trends of λ n /λ T .…”

Section: Density Profiles-experimental Resultsmentioning

confidence: 94%

“…λ T ∼n a e P b tot , where a ∼ 0.5, b = 0.25-0.65. In experiments under conditions of low density, for example, some ohmic and L-mode discharges in JET (Tagle et al 1992) and JT-60U (Asakura et al 1995a), one usually finds λ T > λ n , with a relatively strong dependence of λ T on the discharge density, λ T ∝n b e , where b = 1-2. Both results are similar to limiter results in JET (Erents et al 1989) and might be explained by the low discharge density, which in JET results in conditions within the linear regime (Loarte et al 1995a, Monk et al 1995a, significant penetration of neutrals to the main plasma and evidently SOL behaviour similar to limiter discharges.…”

Section: Regimementioning

confidence: 99%

See 1 more Smart Citation

Experimental divertor physics

Pitcher

Stangeby

1997

Plasma Phys. Control. Fusion

370

394

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The physics of divertors in tokamaks is reviewed, primarily from an experimental point of view, although where possible simple analytic modelling is included. The paper covers the four main subject areas at issue in divertor research: (1) the wide dispersal of plasma power exhausted from the main plasma, (2) the production of sufficiently high gas pressures in the vicinity of pump ducts to enable the removal of fuel and helium ('ash') gas from the system, (3) the elimination or reduction of impurity production and (4) the screening of impurities produced, or intentionally added, at the plasma boundary from the plasma core. A simple analytic model, the 'two-point' model, is introduced early in the paper and provides a framework for comparison of the experimental results, drawn from many machines, with simply derived expectations. Conclusions regarding the direction of future research priorities are made.

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Section: Density Profiles-experimental Resultsmentioning

confidence: 94%

Section: Regimementioning

confidence: 99%

Experimental divertor physics

Pitcher

Stangeby

1997

Plasma Phys. Control. Fusion

370

394

View full text Add to dashboard Cite

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“…Plasmas with significant MHD activity were also avoided, in particular those shots with significant sawtooth instabilities. Finally as different divertor configurations are known to have an effect on L-H power threshold in global scaling studies, and because this effect may be the result of some unknown dependence in the ETB model, the data were collected only from shots with the MkII-GB-SRP divertor [26].…”

Section: Datamentioning

confidence: 99%

The application of classification methods in a data driven investigation of the JET L–H transition

Meakins¹,

McDonald²,

Contributors³

2010

Plasma Phys. Control. Fusion

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Understanding the processes which establish the H-mode edge transport barrier (ETB) and the scaling of those processes with the plasma properties local to the plasma edge is of critical importance for optimizing the performance of power-station scale fusion plasmas. In this paper, data from 67 JET pulses were assembled and classified by confinement mode. A neural network classification technique was applied to identify the nature of the dependence of the L-H boundary on plasma parameters local to the plasma edge. Strong dependences on T e , n e , B and a weak dependence on q 80 were found. In applying the neural network model as a confinement mode identification tool, the correct operating mode was identified for 98.86% of the time slices in a test data set. Using an extended data set the boundary predictions from five theoretical ETB models were evaluated. These models consider a range of different physical processes for the ETB. One model was clearly rejected. While other models proved more favourable, none of the tested models robustly described the JET L-H boundary.

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“…[3,15] This mechanism could perhaps explain the observation from TEXTOR that the SOL density decay length was up to a factor of 4 longer for ICRF heated than neutral beam heated plasmas [16] and similar observations were made on JET. [17] A typical ICRF antenna consists of the current straps housed in an antenna box with a In tokamaks, Faraday screens have become standard plasma facing antenna components despite being an impurity source [5]. In contrast, a shield-less antenna would have reduced RF losses and simpler antenna design.…”

Section: Introductionmentioning

confidence: 99%

RF plasma edge interactions and their impact on ICRF antenna performance in Alcator C-Mod

Wukitch

Lipschultz

Marmar

et al. 2007

Journal of Nuclear Materials

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In Alcator C-Mod, we have investigated the compatibility of high power ion cyclotron range of frequencies antenna with high performance plasmas and all high-Z plasma facing components, to provide operational information for future devices such as ITER.Boronization appears to be critical achieving low radiated power plasmas and is eroded rapidly such that the best performance is lost when the integrated injected RF energy reaches ~50 MJ. Since Ohmic H-modes with similar integrated input energy show a significantly slower degradation, an RF erosion mechanism is playing a significant role. RF-enhanced sheaths on flux tubes connected from the antennas to the top of the outer divertor are the most likely erosion mechanism. Antenna operation without a Faraday screen was found to degrade antenna performance through increased impurity sources. ______________________________________________

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Probe edge measurements in JET X-point plasmas for various heating and plasma conditions

Cited by 10 publications

References 12 publications

Experimental divertor physics

Experimental divertor physics

The application of classification methods in a data driven investigation of the JET L–H transition

RF plasma edge interactions and their impact on ICRF antenna performance in Alcator C-Mod

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