Effect of E×B driven transport on the deposition of carbon in the outer divertor of ASDEX Upgrade

Aho-Mantila, L.; Wischmeier, M.; Krieger, K.; Rohde, V.; Müller, Hans; Coster, D.; Groth, M.; Kirschner, A.; Neu, R.; Potzel, S.; Sieglin, B.; Wolfrum, E.

doi:10.1016/j.jnucmat.2010.10.080

Cited by 13 publications

(14 citation statements)

References 9 publications

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“…The deposition efficiencies reported earlier for Ex fwd [4] and Ex rev [5] are recalculated Figure 2. Calculated injection rates from pressure measurements with the baratron installed in the methane reservoir (top) [4].…”

Section: Experimental Results From Local 13 C Injection Experiments Imentioning

confidence: 99%

“…Recently, large discrepancies were found when comparing these rates with the in-vessel pressure measurements in AUG [5]. More dedicated recalibration efforts, by means of a two chamber experiment, have shown that the measurements inside the gas chamber underestimate the actual injection rate by a factor of ∼3, see figure 2.…”

Section: Experimental Results From Local 13 C Injection Experiments Imentioning

confidence: 99%

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Outer divertor of ASDEX Upgrade in low-density L-mode discharges in forward and reversed magnetic field: II. Analysis of local impurity migration

et al. 2012

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Abstract. Part I presented a detailed analysis of outer divertor plasma conditions in low-density L-mode discharges in ASDEX Upgrade. In this paper, we analyse the local migration of carbon that originates from 13 CH 4 injected into these plasmas from the vertical outer target. Notable changes are observed in the local carbon deposition patterns when reversing the magnetic field in the experiments. Kinetic impurity-following simulations are performed using the 3D ERO code package with 2D background plasma solutions calculated with the SOLPS5.0 code package. The modelling shows that the measured changes are due to the changes in plasma collisionality, dissociation and ionization rates, and E × B drift of the impurities. These conditions affect the direction and rate of impurity migration inside and out of the divertor, having wider consequences on the global migration of impurities in a divertor tokamak. It is further shown, that the migration pathways are largely determined by carbon ions and, hence, relevant for impurities in general. Neutral carbon and hydrocarbons are deposited only in the near vicinity of the injection, where they affect the local re-deposition efficiency. In this limited region, a perturbation of the local plasma conditions by the methane puff appears likely, yielding a significant uncertainty for interpreting the deposition efficiencies. The local deposition is largely influenced by the magnetic presheath electric field, the structure of which is the main uncertainty in the SOLPS5.0-ERO simulations.

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Section: Experimental Results From Local 13 C Injection Experiments Imentioning

confidence: 99%

Section: Experimental Results From Local 13 C Injection Experiments Imentioning

confidence: 99%

Outer divertor of ASDEX Upgrade in low-density L-mode discharges in forward and reversed magnetic field: II. Analysis of local impurity migration

et al. 2012

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“…Particularly at the locations of 13 CH 4 injection, both the absolute value and the gradients along the target are reproduced in the simulations for all three measured quantities. T pk e,ot is reduced compared to previous modelling efforts in [13,14], which is largely a result of changes in assumptions for P in , n sep , and cross-field transport, with minor contribution from code development. The LP data do not cover the whole strike point and, thus, cannot be used to verify the modelled density peak at that location.…”

Section: Divertor Conditions In Forward Fieldmentioning

confidence: 92%

Outer divertor of ASDEX Upgrade in low-density L-mode discharges in forward and reversed magnetic field: I. Comparison between measured plasma conditions and SOLPS5.0 code calculations

et al. 2012

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Abstract. The scrape-off layer and divertor plasma conditions have been carefully analysed in dedicated ASDEX Upgrade experiments consisting of lowdensity L-mode discharges, with both forward and reversed toroidal magnetic field and plasma current. In forward field, the outer divertor plasma is in a lowrecycling regime with peak target temperature above 25 eV. In reversed field with similar main plasma parameters, the target temperature is below 15 eV and the density is 5 times as high as in forward field, indicating a higher recycling regime in the outer divertor. The SOLPS5.0 code package is used to model these divertor plasmas. Specifically, it is tested whether a combination of input assumptions exists that enables matching the code solution to all outer divertor diagnostic measurements, and whether these assumptions are compatible with constraints imposed by measurements outside the outer divertor. In forward field, a good level of agreement with multiple outer target measurements is found with assumptions that simultaneously match the measured density and temperature profiles at the outer midplane, where the uncertainty in radial position of the separatrix is ±0.5 cm. Similar approaches made previously for higher recycling regimes have not led to such a good consistency between all modelled and measured outer divertor parameters. In reversed field with higher recycling in the outer divertor, a solution consistent with the outer target Langmuir probe measurements cannot be obtained, at least not without significantly compromising the match to the upstream profile measurements. Significant mismatches are observed also between the modelled and measured upstream Mach number in forward field. These discrepancies question the global validity of the plasma solutions, and their origin is not yet clear. In Part II, the analysis of outer divertor conditions is complemented by local impurity migration studies, using the divertor plasma solutions presented in this paper.

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“…For local impurity modelling the leading European code is ERO [8,9] -a 3D Monte Carlo impurity transport code that has been applied to several limiter and divertor tokamaks as well as linear plasma experiments, see, e.g., [10][11][12][13][14][15] . ERO depends crucially on high-quality data for PWI as well as for dissociation, ionization and emission data for impurities in the plasma.…”

Section: Introductionmentioning

confidence: 99%

Modelling the erosion of beryllium carbide surfaces

Mehine¹,

Björkas²,

Vörtler³

et al. 2011

Journal of Nuclear Materials

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Effect of E×B driven transport on the deposition of carbon in the outer divertor of ASDEX Upgrade

Cited by 13 publications

References 9 publications

Outer divertor of ASDEX Upgrade in low-density L-mode discharges in forward and reversed magnetic field: II. Analysis of local impurity migration

Outer divertor of ASDEX Upgrade in low-density L-mode discharges in forward and reversed magnetic field: II. Analysis of local impurity migration

Outer divertor of ASDEX Upgrade in low-density L-mode discharges in forward and reversed magnetic field: I. Comparison between measured plasma conditions and SOLPS5.0 code calculations

Modelling the erosion of beryllium carbide surfaces

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