The Langmuir probe system in the Wendelstein 7-X test divertor

Rudischhauser, L.; Endler, M.; Höfel, U.; Hammond, K. C.; Kallmeyer, J. P.; Blackwell, B. D.; Team, W X

doi:10.1063/1.5143013

Cited by 19 publications

(13 citation statements)

References 55 publications

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“…Clarifying to what extent the error field, drifts and the impurity sources correlate with the impurity radiation in the magnetic island chain is subject to future work. The correlation between the thermal and particle load of the target, as measured by IR cameras [68,69], H α -cameras, and divertor Langmuir probe arrays [70], and the impurity radiation in the SOL region, where the connection length is short, is therefore attractive to investigate because it may provide further clues for exploring the role of divertor impurity sources.…”

Section: Theoretical Considerationsmentioning

confidence: 99%

Bolometer tomography on Wendelstein 7-X for study of radiation asymmetry

et al. 2021

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The algorithm for bolometer tomography at Wendelstein 7-X (W7-X) has been recently improved using a novel regularization functional, based on relative gradient smoothing of the sought radiation profile. It has been validated using radiation patterns provided by 3D modeling under real plasma conditions as phantoms and then applied to bolometer measurements performed during the first divertor operation phase of W7-X. The following results are presented: (1) edge-localized 2D radiation patterns with clearly resolved magnetic island radiation structures, (2) an up-down asymmetry in the impurity radiation that is not captured by the 3D edge plasma transport modeling, (3) reversal of the asymmetry with reversed magnetic field direction. Further analysis reveals a poloidal variation of the emissivity in the outer confined plasma region with a field-direction dependent asymmetry, also supported by the soft x-ray measurements. This asymmetry is considered to be related to asymmetric impurity distributions, driven by the pronounced ion-impurity friction force at the plasma edge where the collisionality of the W7-X plasma is sufficiently high to develop impurity asymmetry as predicted by neoclassical theory of parallel impurity transport.

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Section: Theoretical Considerationsmentioning

confidence: 99%

Bolometer tomography on Wendelstein 7-X for study of radiation asymmetry

et al. 2021

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“…The transition to detachment occurs at t ∼ 5.3 s, at which time the total radiated power P rad measured by the bolometer [14] slightly exceeds 3 MW (figure 1(a)), corresponding to a radiation fraction of f rad = P rad /P ECRH (P ECRH = ECRH port power ∼5.5 MW) ∼0.55. The detachment transition is reflected (and defined here) by the abrupt drop in the particle flux on the targets detected by the target LPs [15]. Most of the code-diagnostic comparisons will be performed in the two time windows highlighted in figure 1.…”

Section: Experiments and Diagnostics Chosen For Comparisonmentioning

confidence: 99%

First attempt to quantify W7-X island divertor plasma by local experiment-model comparison

et al. 2021

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As a complement to our recent work [1], which focused on understanding the basic detachment physics and general experimental and numerical trends observed in the W7-X island divertor, this paper compares EMC3-Eirene simulation results with different local diagnostics, including IR cameras, Langmuir probes, H α -cameras, and Thomson scattering. The main purposes are to (1) justify the simulation setup in the previous work, (2) identify the application limitations of the current EMC3-Eirene model, (3) verify the consistency of different diagnostics, and (4) isolate the main geometric and physical effects that need to be prioritized in further developing the EMC3-Eirene code and improving diagnostic capabilities. It turns out that the current version of the EMC3-Eirene code (without drifts) is not yet able to quantitatively reproduce all selected local measurements simultaneously under the current experimental conditions (in particular, the existence of error fields). Nevertheless, it can be shown that within a reasonable range of variation in magnetic configuration, cross-field transport, and SOL plasma state in the modeling, a region of overlap between the numerical results and the local measurements can be established. More accurate model-experiment comparisons will require clarification of error fields, implementation of drifts in EMC3, and improvement of diagnostic capabilities.

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“…To provide some examples of the functionality and experimental capabilities of the D-Mag laboratory, we will present some of the results from the latter two topics mentioned in more detail. For the deeper physical understanding on Langmuir probes and crystal cathode pressure gauges (CCPG), the reader is referred to [20] and [9,14], respectively.…”

Section: Specific Experiments In the D-mag Laboratorymentioning

confidence: 99%

D-Mag — a laboratory for studying plasma physics and diagnostics in strong magnetic fields

et al. 2023

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We have set up a diagnostic magnet (D-Mag) laboratory for a wide range of applications in plasma physics. It consists of a superconducting magnet for field strengths of up to 5.9 T. The main purpose is to provide an experimental environment for the development of plasma diagnostics for nuclear fusion studies and the investigation of dusty plasmas in strong magnetic fields. We describe in the article the setup and operation of the D-Mag. Some applications are presented for the development of plasma diagnostics, such as neutral pressure gauges and Langmuir probes that have to be operated in strong magnetic fields. Among the examples is the test of the long-pulse capability and stability of the diagnostic pressure gauge (DPG) for the ITER device.

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The Langmuir probe system in the Wendelstein 7-X test divertor

Cited by 19 publications

References 55 publications

Bolometer tomography on Wendelstein 7-X for study of radiation asymmetry

Bolometer tomography on Wendelstein 7-X for study of radiation asymmetry

First attempt to quantify W7-X island divertor plasma by local experiment-model comparison

D-Mag — a laboratory for studying plasma physics and diagnostics in strong magnetic fields

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