Divertor parameters and divertor operation in ASDEX

Fußmann, G.; Ditte, U.; Eckstein, W.; Grave, T.; Keilhacker, M.; McCormick, K.; Mürmann, H.; Röhr, H.; Elshaer, M.; Steuer, K.-H.; Szymański, Z.; Wagner, F.; Becker, G.; Bernhardi, K.; Eberhagen, A.; Gehre, O.; Gernhardt, J.; Gierke, G. von; Glock, E.; Gruber, O.; Haas, G.; Hesse, Michael; Janeschitz, G.; Karger, F.; Kissel, S.; Klüber, O.; Kornherr, M.; Lisitano, G.; Mayer, H. M.; Meisel, D.; Müller, E.; Poschenrieder, W.; Ryter, F.; Rapp, H.; Schneider, F.; Siller, G.; Smeulders, P.; Söldner, F. X.; Speth, E.; Stäbler, A.; Vollmer, O.

doi:10.1016/0022-3115(84)90377-5

Cited by 48 publications

(41 citation statements)

References 7 publications

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“…The ratio of Separatrix location determined by the peak in plasma pressure (≈ n e T e ) is denoted by the vertical dashed line at −3cm. The T e profile is similar to that found in ASDEX [14] exhibiting a broad temperature "shoulder". electrons in the plasma divided by the nominal electrons supplied by the gas fueling rates is interpreted as a fueling efficiency.…”

Section: Resultssupporting

confidence: 61%

Modification Of The Electron Energy Distribution Function During Lithium Experiments On The National Spherical Torus Experiment

Jaworski¹,

Gray²,

Kaita³

et al. 2011

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The National Spherical Torus Experiment (NSTX) has recently studied the use of a liquid lithium divertor (LLD). Divertor Langmuir probes have also been installed for making measurements of the local plasma conditions. A non-local probe interpretation method is used to supplement the classical probe interpretation and obtain measurements of the electron energy distribution function (EEDF) which show the occurrence of a hot-electron component. Analysis is made of two discharges within a sequence that exhibited changes in plasma fueling efficiency. It is found that the local electron temperature increases and that this increase is most strongly correlated with the energy contained within the hot-electron population. Preliminary in- scrape-off layer (SOL) plasma. The decrease in plasma fueling efficiency, increase in local temperature, and increase in hot-electron fraction are all consistent with an absorbing surface intercepting the SOL plasma.

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Section: Resultssupporting

confidence: 61%

Modification Of The Electron Energy Distribution Function During Lithium Experiments On The National Spherical Torus Experiment

Jaworski¹,

Gray²,

Kaita³

et al. 2011

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“…In this section, we investigate the possibility to use the Langmuir probes to measure the temperature at the wall in detached conditions, which is generally considered to be a difficult regime for Langmuir probe measurement interpretation. [30][31][32] Indeed, it has been seen in several tokamaks, 33,34 including TCV, 31,32 that in detached conditions, the Langmuir probe analysis yields electron temperature higher than that one would expect from other diagnostics such as spectroscopy, [35][36][37] Thomson scattering, 29,38 or simulations. 31 Several mechanisms might be responsible for this effect, such as the role of plasma resistance 1,39 or the fluctuations of the floating potential.…”

Section: Application To Detached Plasmasmentioning

confidence: 99%

Analysis of wall-embedded Langmuir probe signals in different conditions on the Tokamak à Configuration Variable

Février

Theiler

Oliveira

et al. 2018

Review of Scientific Instruments

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This paper presents the current wall-embedded Langmuir probe system installed on the Tokamak à Configuration Variable (TCV), as well as the analysis tool chain used to interpret the current-voltage characteristic obtained when the probes are operated in swept-bias conditions. The analysis is based on a four-parameter fit combined with a minimum temperature approach. In order to reduce the effect of plasma fluctuations and measurement noise, several current-voltage characteristics are usually averaged before proceeding to the fitting. The impact of this procedure on the results is investigated, as well as the possible role of finite resistances in the circuitry, which could lead to an overestimation of the temperature. We study the application of the procedure in a specific regime, the plasma detachment, where results from other diagnostics indicate that the electron temperature derived from the Langmuir probes might be overestimated. To address this issue, we explore other fitting models and, in particular, an extension of the asymmetric double probe fit, which features effects of sheath expansion. We show that these models yield lower temperatures (up to approximately 60%) than the standard analysis in detached conditions, particularly for a temperature peak observed near the plasma strike point, but a discrepancy with other measurements remains. We explore a possible explanation for this observation, the presence of a fast electron population, and assess how robust the different methods are in such conditions.

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“…The assumption for Maxwellian EEDF in fusion plasma is generally accepted and used in most cases of evaluating the main plasma parameters. However, there appeared theoretical predictions [21][22][23] and experimental evidence [24][25][26][27][28][29] that the EEDF can deviate from the Maxwellian in the vicinity of the last closed flux surface (LCFS) and in the divertor region of the tokamaks. To the best of our knowledge, only the first-derivative probe technique (FDPT), presented and discussed in detail in the review paper [8], could estimate the real EEDF if it deviates from the Maxwellian.…”

Section: First-derivative Probe Techniquementioning

confidence: 99%

Advantages of the first-derivative probe technique over the three- and four-parameter probe techniques in fusion plasmas diagnostics

et al. 2018

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In this work, the advantages are presented and discussed of the first-derivative probe technique over the three- and the four-parameter conventional probe techniques for diagnostics of fusion plasmas. The conventional probe techniques for estimation of the plasma potential and the electron temperature and density can only be used when the electron energy distribution function (EEDF) is Maxwellian. The first-derivative probe technique can provide reliable results for the plasma potential and the real EEDF when the latter deviates from Maxwellian. To exemplify the application of the results obtained by different techniques, results on the parallel power-flux density distribution in the divertor region of the COMPASS tokamak, IPP.CR, are presented and discussed.

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Divertor parameters and divertor operation in ASDEX

Cited by 48 publications

References 7 publications

Modification Of The Electron Energy Distribution Function During Lithium Experiments On The National Spherical Torus Experiment

Modification Of The Electron Energy Distribution Function During Lithium Experiments On The National Spherical Torus Experiment

Analysis of wall-embedded Langmuir probe signals in different conditions on the Tokamak à Configuration Variable

Advantages of the first-derivative probe technique over the three- and four-parameter probe techniques in fusion plasmas diagnostics

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