EMC3-EIRENE simulation of first wall recycling fluxes in W7-X with relation to H-alpha measurements

Winters, V.; Reimold, F.; König, R.; Krychowiak, M.; Romba, T.; Biedermann, C.; Bozhenkov, S.; Drewelow, P.; Endler, M.; Feng, Y.; Frerichs, H.; Fuchert, G.; Geiger, J.; Gao, Yu; Harris, J. H.; Jakubowski, M.; Kornejew, P.; Kremeyer, T.; Niemann, H.; Pasch, E.; Puig-Sitjes, A.; Schlisio, G.; Scott, E. R.; Wurden, G. A.

doi:10.1088/1361-6587/abe39c

Cited by 19 publications

(25 citation statements)

References 21 publications

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“…The passive signal from the inner plasma region can therefore be neglected in active measurements. A recent study using the 3D-modeling tool EMC3-EIRENE combined with H𝛼-spectroscopy measurements agrees on the magnitude of the recycled neutral densities found with the presented simple model [35].…”

Section: Diagnostic Beam Neutralssupporting

confidence: 83%

Feasibility of neutral particle analysis for fast-ion measurements at W7-X

Bannmann¹,

Bozhenkov²,

Äkäslompolo³

et al. 2022

J. Inst.

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A preliminary study investigating capabilities of a planned but not yet installed neutral particle analyzer (NPA) [1,2] system combined with a diagnostic neutral beam at Wendelstein 7-X (W7-X) [3] is presented. Additionally two NPAs viewing the neutral beam injection (NBI) [4] source 8 beam and using it as neutral source are studied. The main focus is laid on what information about NBI fast-ion slowing down distributions can be inferred from active NPA measurements when altering the magnetic configuration, plasma β, density, electron temperature or radial electric field. For an order of magnitude estimation of the passive signal a model for penetration of neutral hydrogen recycling from the first wall is implemented. For the active signal a diagnostic neutral beam injector was simulated using FIDASIM [5]. The fast-ion slowing down distributions were calculated with ASCOT [6]. The synthetic NPA signal is found in general to be sensitive to changes in the fast-ion distribution function. Distinct features can be seen in the high energy active signal in the high-mirror configuration when changing β, especially, when looking at deeply trapped fast particles. However, for the initially planned installation geometry of the NPA diagnostic most fast-ion distributions exhibit only small differences in the magnitude and especially shape. In a high density case in the standard magnetic configuration with a central β of 8%, the fast-ion density in the core region is too low to provide a measurable flux of charge exchanged neutrals. The passive signal from the inner plasma regions is found to be negligible compared to the active signal.

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Section: Diagnostic Beam Neutralssupporting

confidence: 83%

Feasibility of neutral particle analysis for fast-ion measurements at W7-X

Bannmann¹,

Bozhenkov²,

Äkäslompolo³

et al. 2022

J. Inst.

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“…Even within uncertainties of up to 50% due to spectral filter choices and probe pin configurations, these values are smaller than typical tokamak experimental results or modelling assumptions [30,32,35,37]. In EMC3-EIRENE modelling of W7-X, D is typically assumed between 0.5 m 2 s −1 -1.5 m 2 s −1 to obtain plausible modelling results [36,38,39]. Therefore, the level of turbulent transport observed here advocates to use 0.5 m 2 s −1 or less in EMC3-EIRENE simulations.…”

Section: Discussionmentioning

confidence: 98%

Turbulent transport in the scrape-off layer of Wendelstein 7-X

2021

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Turbulent transport is widely considered to be the main driver for cross-field transport in the scrape-off layer (SOL) of toroidal magnetized plasmas. Here, reciprocating Langmuir probes are employed to measure both the plasma profiles and the turbulent particle transport in the SOL of the Wendelstein 7-X stellarator. The relation between turbulent radial particle flux Γ r and the local pressure gradient is often approximately linear across the entire SOL width, indicating that radial turbulence spreading is absent. This observation holds across a wide range of magnetic configurations and different plasma heating and density scenarios. The magnitude of the turbulent transport for a given gradient reveals a dependence on the magnetic configuration and the position in the SOL, which we relate to the cross-spectral characteristics of multi-tip floating potential measurements. Magnetic islands can add further complexity due to non-monotonic SOL profiles and the breaking of the transport-gradient relation. Finally, anomalous diffusion coefficients are determined from the probe measurements.

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“…The simulations will help to explore the capability of these configurations for long pulse operation from the PSI and plasma exhaust perspective. Moreover, the range of ERO2.0 simulations in standard divertor configuration will be expanded to plasmas with impurity seeding (Ne or N 2 ) and detached divertor conditions [46,71] once suitable EMC3-EIRENE simulations are available. Impurity seeded plasmas are one of the most promising candidates to comply with the power load restriction to the target plates with enlarged input power in W7-X.…”

Section: Discussionmentioning

confidence: 99%

Plasma–surface interaction in the stellarator W7-X: conclusions drawn from operation with graphite plasma-facing components

et al. 2021

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W7-X completed its plasma operation in hydrogen with island divertor and inertially cooled test divertor unit (TDU) made of graphite. A substantial set of plasma-facing components (PFCs), including in particular marker target elements, were extracted from the W7-X vessel and analysed post-mortem. The analysis provided key information about underlying plasma–surface interactions (PSI) processes, namely erosion, transport, and deposition as well as fuel retention in the graphite components. The net carbon (C) erosion and deposition distribution on the horizontal target (HT) and vertical target (VT) plates were quantified and related to the plasma time in standard divertor configuration with edge transform ι = 5/5, the dominant magnetic configuration of the two operational phases (OP) with TDU. The operation resulted in integrated high net C erosion rate of 2.8 mg s−1 in OP1.2B over 4809 plasma seconds. Boronisations reduced the net erosion on the HT by about a factor 5.4 with respect to OP1.2A owing to the suppression of oxygen (O). In the case of the VT, high peak net C erosion of 11 μm at the strike line was measured during OP1.2B which converts to 2.5 nm s−1 or 1.4 mg s−1 when related to the exposed area of the target plate and the operational time in standard divertor configuration. PSI modelling with ERO2.0 and WallDYN-3D is applied in an interpretative manner and reproduces the net C erosion and deposition pattern at the target plates determined by different post-mortem analysis techniques. This includes also the 13C tracer deposition from the last experiment of OP1.2B with local 13CH4 injection through a magnetic island in one half module. The experimental findings are used to predict the C erosion, transport, and deposition in the next campaigns aiming in long-pulse operation up to 1800 s and utilising the actively cooled carbon-fibre composite (CFC) divertor currently being installed. The CFC divertor has the same geometrical design as the TDU and extrapolation depends mainly on the applied plasma boundary. Extrapolation from campaign averaged information obtained in OP1.2B reveals a net erosion of 7.6 g per 1800 s for a typical W7-X attached divertor plasma in hydrogen.

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EMC3-EIRENE simulation of first wall recycling fluxes in W7-X with relation to H-alpha measurements

Cited by 19 publications

References 21 publications

Feasibility of neutral particle analysis for fast-ion measurements at W7-X

Feasibility of neutral particle analysis for fast-ion measurements at W7-X

Turbulent transport in the scrape-off layer of Wendelstein 7-X

Plasma–surface interaction in the stellarator W7-X: conclusions drawn from operation with graphite plasma-facing components

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