Prospects of X-ray imaging spectrometers for impurity transport: Recent results from the stellarator Wendelstein 7-X (invited)

Langenberg, A.; Pablant, N.; Wegner, Thomas; Traverso, P.; Marchuk, O.; Bräuer, T.; Geiger, B.; Fuchert, G.; Bozhenkov, S.; Pasch, E.; Grulke, O.; Kunkel, F.; Killer, C.; Nicolai, D.; Satheeswaran, G.; Hollfeld, K. P.; Schweer, B.; Krings, Th.; Drews, P.; Offermanns, Guido; Pavone, A.; Svensson, J.; Alonso, A.; Burhenn, R.; Wolf, R. C.; Team, W X

doi:10.1063/1.5036536

Cited by 32 publications

(38 citation statements)

References 39 publications

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“…This reduction of about 3% is caused by the decreasing plasma energy following the impurity injection. Other impurity transport studies show similar results regarding the transport time which is in the same order of magnitude 48 .…”

Section: Resultssupporting

confidence: 75%

Design, capabilities, and first results of the new laser blow-off system on Wendelstein 7-X

Wegner

Geiger

Kunkel

et al. 2018

Review of Scientific Instruments

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We present a detailed overview and first results of the new laser blow-off system on the stellarator Wendelstein 7-X. The system allows impurity transport studies by the repetitive and controlled injection of different tracer ions into the plasma edge. A Nd:YAG laser is used to ablate a thin metal film, coated on a glass plate, with a repetition rate of up to 20 Hz. A remote-controlled adjustable optical system allows the variation of the laser spot diameter and enables the spot positioning to non-ablated areas on the target between laser pulses. During first experiments, clear spectral lines from higher ionization stages of the tracer ions have been observed in the X-ray to the extreme ultraviolet spectral range. The temporal behavior of the measured emission allows the estimate of transport properties, e.g., impurity transport times in the order of 100 ms. Although the strong injection of impurities is well detectable, the global plasma parameters are barely changed.

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Section: Resultssupporting

confidence: 75%

Design, capabilities, and first results of the new laser blow-off system on Wendelstein 7-X

Wegner

Geiger

Kunkel

et al. 2018

Review of Scientific Instruments

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“…Lineaveraged ion temperatures and radial electric field information was provided by an X-Ray Imaging Crystal Spectrometer (XICS) 4,8,9 based on low levels of argon injection. Ion density information was available only in the form of some preliminary Bremsstrahlung based effective charge Z eff measurements 10 .…”

Section: Introductionmentioning

confidence: 99%

Charge exchange recombination spectroscopy at Wendelstein 7-X

Ford

Vanó

Alonso

et al. 2020

Review of Scientific Instruments

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The Charge Exchange Recombination Spectroscopy (CXRS) diagnostic has become a routine diagnostic on almost all major high temperature fusion experimental devices. For the optimised stellarator W7-X, a highly flexible and extensive CXRS diagnostic has been built to provide high-resolution local measurements of several important plasma parameters using the recently commissioned neutral beam heating. This paper outlines the design specifics of the W7-X CXRS system and gives examples of the initial results obtained including typical ion temperature profiles for several common heating scenarios, toroidal flow and radial electric field derived from velocity measurements, beam attenuation via beam emission spectra and finally, normalised impurity density profiles under some typical plasma conditions.

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“…There are many diagnostic systems dedicated to the observation of contamination in the Wendelstein 7-X plasmas [2][3][4]. One of them will be "C/O Monitor"-the dedicated spectrometer, designed for monitoring of four main light impurities, namely oxygen, nitrogen, carbon and boron.…”

Section: Introductionmentioning

confidence: 99%

Modelling of expected B, C, N and O Lyman-α line intensities emitted from W7-X plasmas and measured by means of the W7-X light impurity monitor system

et al. 2021

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The “C/O Monitor” for Wendelstein 7-X (W7-X) is a dedicated light impurity XUV spectrometer intended to measure Lyman-α transitions of hydrogen-like ions of four low-Z impurities—boron (4.9 nm), carbon (3.4 nm), nitrogen (2.5 nm) and oxygen (1.9 nm). Since the discussed diagnostic will deliver continuous information about the line intensities, it is crucial to understand the origin of the obtained signals with respect to the experimental plasma conditions (electron temperature and density). This, however, might be difficult because of the broad acceptance angle of the spectrometer and irregular shape of the plasma edge or SOL where the radiation is expected to mostly come from, depending on the plasma temperature. For that reason, numerous analyses assuming various ranges of electron density and temperature profiles of the W7-X plasmas have been performed (assuming corona equilibrium and neglecting impurity transport processes). The aim of this work is to estimate the expected radiant flux and determine the sensitivity of the system on impurity-level changes. It will allow to improve understanding between measured signal and impurity concentration.

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Prospects of X-ray imaging spectrometers for impurity transport: Recent results from the stellarator Wendelstein 7-X (invited)

Cited by 32 publications

References 39 publications

Design, capabilities, and first results of the new laser blow-off system on Wendelstein 7-X

Design, capabilities, and first results of the new laser blow-off system on Wendelstein 7-X

Charge exchange recombination spectroscopy at Wendelstein 7-X

Modelling of expected B, C, N and O Lyman-α line intensities emitted from W7-X plasmas and measured by means of the W7-X light impurity monitor system

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