Argon impurity transport studies at Wendelstein 7-X using x-ray imaging spectrometer measurements

Langenberg, A.; Pablant, N.; Marchuk, O.; Zhang, D.; Alonso, A.; Burhenn, R.; Svensson, J.; Valson, P.; Gates, D.; Beurskens, M.; Wolf, R. C.

doi:10.1088/1741-4326/aa70f4

Cited by 25 publications

(37 citation statements)

References 27 publications

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“…No significant changes of the impurity intensities are observed in these iota scans. It should be noted that due to the limited energy resolution, the intensity of the PHA Ar lines also contains the dielectronic recombination/innershell excitation satellites as observed by the XICS spectrometer [22,23], but this does not affect the overall trend. A clear difference in the impurity intensity, however, is observed when the level of the ECRH power is changed, which affects the bulk plasma properties.…”

Section: Resultsmentioning

confidence: 99%

“…All lines registered so far by the PHA diagnostic are listed in [20]. Ar is an impurity species which has been injected by the main gas inlet system into the W7-X vacuum chamber just before the plasma start (in order to derive the Ti profile by means of an imaging spectrometer [22,23]. The number of injected Ar particles from the the main gas inlet system was the same in each of the analyzed discharges.…”

Section: Methodsmentioning

confidence: 99%

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Study of impurity behaviour for first magnetic configuration changes in W7-X plasmas by means of PHA spectra

Czarnecka

Fornal

Gruca

et al. 2018

Fusion Engineering and Design

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Transport properties of impurities in stellarators are sensitive to potential variations on flux-surfaces, and thermodynamic forces from the bulk plasma which might be affected by changes in magnetic field properties. In this contribution, the effect of planar coil current changes on the core impurity behavior in the first operating phase of Wendelstein 7-X (W7-X) is described. Hydrogen plasmas, at different heating power levels were investigated showing Core-Electron-Root-Confinement (CERC) conditions, characterized by peaked Te profiles and positive radial electric fields in the plasma core. Impurity spectra in the x-ray emission range between 1 and 10 keV were measured by the Pulse Height Analysis (PHA) diagnostic. The line-integrated measurements of transitions in sulphur, chlorine and argon are in the focus of this analysis. First observations indicate that the scans of the magnetic configuration did not affect strongly the impurity concentration in the core. Clear differences in the impurity content, however, have been observed when the ECRH power was changed, which affects the bulk plasma properties.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Study of impurity behaviour for first magnetic configuration changes in W7-X plasmas by means of PHA spectra

Czarnecka

Fornal

Gruca

et al. 2018

Fusion Engineering and Design

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“…and W 46? arise in the central JET plasma, which may be considered as a zone of reduced transport [22,23]. The X-ray structures associated with Mo 32?…”

Section: X-ray Spectra Simulations In the Framework Of Collisional-ramentioning

confidence: 99%

Theoretical Modeling of High-Resolution X-ray Spectra Emitted by Tungsten and Molybdenum Ions from Tokamak Plasmas

et al. 2020

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In order to allow the advanced interpretation of the X-ray spectra registered by the high-resolution crystal KX1 spectrometer on the JET with an ITER-like wall, especially to determine how the relative emission contributions of tungsten and molybdenum ions change during a JET discharge, the X-ray spectra have been carefully modeled over a narrow wavelength range. The simulations have been done in the framework of Collisional-Radiative model implemented in Flexible Atomic Code for an electron density (n e = 2.5 9 10 19 m -3 ), and electron temperatures between T e = 3.0 keV and T e = 4.5 keV, typical for JET. Moreover, performed detailed analysis in the framework of the proposed procedure can be useful in determining temperature of a high temperature plasma generated in tokamaks.Keywords X-ray spectra Á Tokamak Á Tungsten M X-ray lines Á Molybdenum L X-ray lines Á High-resolution crystal spectrometer Journal of Fusion Energy https://doi.org/10.1007/s10894-020-00231-y( 0123456789().,-volV) (0123456789().,-volV)

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“…The emission is then collected on a CCD de-tector. The diagnostic layout and initial measurements during the first operational phase at W7-X have been described in [7][8][9][10][11] . The collected images have spatial resolution along vertical dimension, corresponding to different lines of sight, and wavelength resolution along the horizontal one.…”

Section: Application To Xics Diagnostic Data At W7-xmentioning

confidence: 99%

“…The ion temperature affects the Doppler broadening of the spectral lines, whereas the electron temperature affects the relative intensities. Given the electron density profile n e , the impurity density profiles can be obtained 8,12 . A forward model of the diagnostic 7 has been developed within the Minerva Bayesian modeling framework 13 , and it is used for the inference of the plasma profiles of interest.…”

Section: Application To Xics Diagnostic Data At W7-xmentioning

confidence: 99%

Bayesian uncertainty calculation in neural network inference of ion and electron temperature profiles at W7-X

Pavone

Svensson

Langenberg

et al. 2018

Review of Scientific Instruments

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We make use of a Bayesian description of the neural network (NN) training for the calculation of the uncertainties in the NN prediction. Having uncertainties on the NN prediction allows to have a quantitative measure for trusting the NN outcome and comparing it with other methods. Within the Bayesian framework, the uncertainties can be calculated under different approximations. The NN has been trained with the purpose of inferring ion and electron temperature profile from measurements of a X-ray imaging diagnostic at W7-X. The NN has been trained in such a way that it constitutes an approximation of a full Bayesian model of the diagnostic, implemented within the Minerva framework. The network has been evaluated on measured data and the uncertainties calculated under different approximations have been compared with each other, finding that neglecting the noise on the NN input can lead to an underestimation of the error bar magnitude in the range of 10% to 30%.

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Argon impurity transport studies at Wendelstein 7-X using x-ray imaging spectrometer measurements

Cited by 25 publications

References 27 publications

Study of impurity behaviour for first magnetic configuration changes in W7-X plasmas by means of PHA spectra

Study of impurity behaviour for first magnetic configuration changes in W7-X plasmas by means of PHA spectra

Theoretical Modeling of High-Resolution X-ray Spectra Emitted by Tungsten and Molybdenum Ions from Tokamak Plasmas

Bayesian uncertainty calculation in neural network inference of ion and electron temperature profiles at W7-X

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