Charge exchange recombination spectroscopy at Wendelstein 7-X

Ford, O.; Vanó, L.; Alonso, A.; Baldzuhn, J.; Beurskens, M.; Biedermann, C.; Bozhenkov, S.; Fuchert, G.; Geiger, B.; Hartmann, D.; Jaspers, R.; Kappatou, A.; Langenberg, A.; Lazerson, S.; McDermott, R. M.; McNeely, P.; Neelis, T. W. C.; Pablant, N.; Pasch, E.; Rust, N.; Schroeder, R.; Scott, E. R.; Smith, H. M.; Wegner, T.; Kunkel, F.; Wolf, R. C.; Team, W X

doi:10.1063/1.5132936

Cited by 42 publications

(60 citation statements)

References 38 publications

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“…2018; Ford et al. 2020). They have a generally good agreement with numerical neoclassical calculations by codes like the drift kinetic equation solver, DKES (Hirshman et al.…”

Section: Measurementsmentioning

confidence: 99%

“…Panel ( a ) shows the electron density, in and electron temperature, in keV, both measured by the Thomson scattering diagnostic, as well as the ion temperature, in keV, measured by charge exchange recombination spectroscopy (CXRS) (Ford et al. 2020). The vertical lines are measurement values with error bars which represent measurement uncertainties.…”

Section: Experimental Set-upmentioning

confidence: 99%

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Phase contrast imaging measurements and numerical simulations of turbulent density fluctuations in gas-fuelled ECRH discharges in Wendelstein 7-X

et al. 2021

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The fundamental nature of turbulent density fluctuations in standard Wendelstein 7-X (W7-X) stellarator discharges is investigated experimentally via phase contrast imaging (PCI) in combination with gyrokinetic simulations with the code GENE. We find that density fluctuations are ion-temperature-gradient-driven and radially localised in the outer half of the plasma. It is shown that the line-integrated PCI measurements cover the right range of wavenumbers and a favourable toroidal and poloidal location to capture some of the strongest density fluctuations in W7-X. Due to the radial localisation of fluctuations, measured wavenumber–frequency spectra exhibit a dominant phase velocity, which can be related to the $\boldsymbol {E\times B}$ rotation velocity at the radial position of a well in the neoclassical radial electric field. The match is robust against variations of heating power and line-integrated density, which is partly due to the localisation of fluctuations and partly due to effects of the radial gradient in the $\boldsymbol {E\times B}$ velocity profile on the wavenumber–frequency spectrum. The latter effect is studied with a newly built synthetic PCI diagnostic and global gyrokinetic simulations with GENE-3D.

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“…2018; Ford et al. 2020). They have a generally good agreement with numerical neoclassical calculations by codes like the drift kinetic equation solver, DKES (Hirshman et al.…”

Section: Measurementsmentioning

confidence: 99%

Section: Experimental Set-upmentioning

confidence: 99%

Phase contrast imaging measurements and numerical simulations of turbulent density fluctuations in gas-fuelled ECRH discharges in Wendelstein 7-X

et al. 2021

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“…Finally, the confined neutral density in the simulation is compared to an experimental measurement for 20180920.013 using high dynamic range H-alpha spectroscopy from a subset of spectrometers used in charge exchange analysis [22]. The measurement technique was based on the analysis technique from Fujii et al [23].…”

Section: Diagnostic Line Of Sight Comparisons With Emc3-eirenementioning

confidence: 99%

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

Winters

Reimold

König

et al. 2021

Plasma Phys. Control. Fusion

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In the Wendelstein 7-X stellarator, the main locations of particle sources are expected to be the carbon divertors, baffles and graphite heat shield first wall. In this paper, the heat shield is implemented in EMC3-EIRENE to understand the expected areas and magnitudes of the recycling flux to this component. It is found that in the simulation the heat shield is not a significant source of recycling neutrals. The areas of simulated recycling flux are shown to correlate well with footprints of plasma-wetting seen in post-experimental campaign in-vessel inspection photos. EMC3-EIRENE reconstruction of line-integrated H-alpha measurements at the heat shield indicate that the majority of emission does not come from local recycling neutrals. Rather, the H-alpha signals at the heat shield are dominated by ionization of neutrals which have leaked from the divertor/baffle region into the midplane. The magnitude of the H-alpha line emission from the synthetic reconstruction is consistent with the experiment, indicating that a large overestimation of heat shield recycling would occur if these measurements were assumed to be from local recycling sources. In the future, it may be possible to obtain some information of local recycling from the heat shield since it was found that the majority of the recycling flux occurs on two well-localized areas.

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“…A two-power profile is used for the ion and electron temperature profiles. During NBI operation the charge exchange recombination system (CXRS) measures parameters along the beam-line, including the ion temperature [13]. A two-power profile is used for the fit of this data, with the lookup table providing the mapping between cartesian space and ρ for each channel.…”

Section: Rapid Profile Fittingmentioning

confidence: 99%

“…Figure13. Reconstructed XICS electron temperature data for the medium density standard configuration discharge (20180821.12).…”

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confidence: 99%

Validation of the BEAMS3D neutral beam deposition model on Wendelstein 7-X

et al. 2020

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The neutral beam deposition model in the BEAMS3D code is validated against neutral beam attenuation data from Wendelstein 7-X (W7-X). A set of experimental discharges where the neutral beam injection system of W7-X was utilized were reconstructed.These discharges scanned the magnetic configurations and plasma densities of W7-X. The equilibrium reconstructions were performed using STELLOPT which calculates three-dimensional self-consistent ideal magnetohydrodynamic equilibria and kinetic profiles. These reconstructions leveraged new capabilities to incorporate electron cyclotron emission and X-ray imaging diagnostics in the STELLOPT code. The reconstructed equilibria and profiles served as inputs for BEAMS3D calculations of neutral beam deposition in W7-X. It is found that if reconstructed kinetic profiles are utilized, good agreement between measured and

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Charge exchange recombination spectroscopy at Wendelstein 7-X

Cited by 42 publications

References 38 publications

Phase contrast imaging measurements and numerical simulations of turbulent density fluctuations in gas-fuelled ECRH discharges in Wendelstein 7-X

Phase contrast imaging measurements and numerical simulations of turbulent density fluctuations in gas-fuelled ECRH discharges in Wendelstein 7-X

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

Validation of the BEAMS3D neutral beam deposition model on Wendelstein 7-X

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