The Thomson scattering system at Wendelstein 7-X

Pasch, E.; Beurskens, M.; Bozhenkov, S.; Fuchert, G.; Knauer, J.; Wolf, R. C.

doi:10.1063/1.4962248

Cited by 106 publications

(109 citation statements)

References 4 publications

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“…3). At t = 1.1 s, the Thomson scattering (TS) system 19 showed central electron density and temperature values of

n_{e 0} = 3.5 \times 10^{19}

m –3 and

T_{e 0} \geq 4

keV, respectively. The x-ray crystal imaging spectrometer (XICS) measured the central ion temperature to be

T_{i 0} = 2.2

keV at that point in time.…”

Section: Achieved and Predicted Triple Products For W7-xmentioning

confidence: 99%

Key results from the first plasma operation phase and outlook for future performance in Wendelstein 7-X

et al. 2017

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The first physics operation phase on the stellarator experiment Wendelstein 7-X was successfully completed in March 2016 after about 10 weeks of operation. Experiments in this phase were conducted with five graphite limiters as the primary plasma-facing components. Overall, the results were beyond the expectations published shortly before the start of operation [Sunn Pedersen et al., Nucl. Fusion 55, 126001 (2015)] both with respect to parameters reached and with respect to physics themes addressed. We report here on some of the most important plasma experiments that were conducted. The importance of electric fields on global confinement will be discussed, and the obtained results will be compared and contrasted with results from other devices, quantified in terms of the fusion triple product. Expected values for the triple product in future operation phases will also be described and put into a broader fusion perspective.

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“…3). At t = 1.1 s, the Thomson scattering (TS) system 19 showed central electron density and temperature values of

n_{e 0} = 3.5 \times 10^{19}

m –3 and

T_{e 0} \geq 4

keV, respectively. The x-ray crystal imaging spectrometer (XICS) measured the central ion temperature to be

T_{i 0} = 2.2

keV at that point in time.…”

Section: Achieved and Predicted Triple Products For W7-xmentioning

confidence: 99%

Key results from the first plasma operation phase and outlook for future performance in Wendelstein 7-X

et al. 2017

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“…In order to obtain relative Ar, Cl, S impurity content in the plasma, numerical simulations have been performed. In these simulations, for a relative comparison of impurity contamination, coronal equilibrium was assumed and experimental profiles of Te and ne from Thomson Scattering (TS) diagnostics [28] were taken. The use of corona equilibrium in the central part of the plasma is generally a good first approach for He-like ions which are distributed widely across the plasma cross-section due to the large step in its ionization energy to H-like states.…”

Section: Resultsmentioning

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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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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“…A multi-pulse Nd:YAG laser Thomson scattering system is installed at W7-X as a powerful diagnostic for electron temperature and density measurements 13 (for measurement of T e profiles with the XICS diagnostic see Section II D). In OP1.1 a reduced set of 10 fiber bundles was installed to cover a half profile of the plasma cross section, as shown in Fig.…”

Section: B Diagnostics For Plasma Profilesmentioning

confidence: 99%

Overview of diagnostic performance and results for the first operation phase in Wendelstein 7-X (invited)

Krychowiak

Adnan

Alonso

et al. 2016

Review of Scientific Instruments

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Wendelstein 7-X, a superconducting optimized stellarator built in Greifswald/Germany, started its first plasmas with the last closed flux surface (LCFS) defined by 5 uncooled graphite limiters in December 2015. At the end of the 10 weeks long experimental campaign (OP1.1) more than 20 independent diagnostic systems were in operation, allowing detailed studies of many interesting plasma phenomena. For example, fast neutral gas manometers supported by video cameras (including one fast-frame camera with frame rates of tens of kHz) as well as visible cameras with different interference filters, with field of views covering all ten half-modules of the stellarator, discovered a MARFE-like radiation zone on the inboard side of machine module 4. This structure is presumably triggered by an inadvertent plasma-wall interaction in module 4 resulting in a high impurity influx that terminates some discharges by radiation cooling. The main plasma parameters achieved in OP1.1 exceeded predicted values in discharges of a length reaching 6 s. Although OP1.1 is characterized by short pulses, many of the diagnostics are already designed for quasi-steady state operation of 30 min discharges heated at 10 MW of ECRH. An overview of diagnostic performance for OP1.1 is given, including some highlights from the physics campaigns.

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The Thomson scattering system at Wendelstein 7-X

Cited by 106 publications

References 4 publications

Key results from the first plasma operation phase and outlook for future performance in Wendelstein 7-X

Key results from the first plasma operation phase and outlook for future performance in Wendelstein 7-X

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

Overview of diagnostic performance and results for the first operation phase in Wendelstein 7-X (invited)

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