Installation of the soft X-ray multi-camera tomography system (XMCTS) in the Wendelstein 7-X stellarator

Brandt, Ch.; Broszat, T.; Thomsen, H.; Laube, R.; Marquardt, M.; Franz, P.; Schülke, M.; Sieber, T.; Weißflog, S.

doi:10.1016/j.fusengdes.2017.02.111

Cited by 12 publications

(23 citation statements)

References 8 publications

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“…At φ = 15 • a second Doppler reflectometer is also installed. The other two planes have been considered since the distance between them in φ is one fourth of a the machine period, the first of them being the frequently represented triangular plane where other essential diagnostics for impurity transport look at, like the soft-X rays Multi-Camera Tomography System (XMCTS) [48] or the bolometry cameras [49]. The difference between the figures on the left, with labels (a)-(d), and on the right, with labels (e)-(h), is that while the former show the results assuming adiabatic electrons, the latter do it for the cases considering kinetic electrons.…”

Section: Potential Variations In W7-x: Cerc Plasmas and Effect Of Kinmentioning

confidence: 99%

On-surface potential and radial electric field variations in electron root stellarator plasmas

García-Regaña

Estrada

Calvo

et al. 2018

Plasma Phys. Control. Fusion

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In the present work we report recent radial electric field measurements carried out with the Doppler reflectometry system in the TJ-II stellarator. The study focuses on the fact that, under some conditions, the radial electric field measured at different points over the same flux surface shows significantly different values. A numerical analysis is carried out considering the contribution arising from the radial dependence of Φ 1 as a possible correction term to the total radial electric field. Here Φ 1 is the neoclassical electrostatic potential variation over the surface. The comparison shows good agreement in some aspects, like the conditions under which this correction is large (electron-root conditions) or negligible (ion-root conditions). But it disagrees in others like the sign of the correction. The results are discussed together with the underlying reasons of this partial disagreement. In addition, motivated by the recent installation of the dual Doppler reflectometry system in Wendelstein 7-X (W7-X), Φ 1 estimations for W7-X are revisited considering Core-Electron-Root-Plasma (CERC) plasmas from its first experimental campaign. The simulations show larger values of Φ 1 under electron-root conditions than under ion root ones. The contribution from the kinetic electron response is shown to become important at some radii. All this results in a potential variation size noticeably larger than estimated in our previous work in W7-X [1] for other plasma parameters and another configuration.

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Section: Potential Variations In W7-x: Cerc Plasmas and Effect Of Kinmentioning

confidence: 99%

On-surface potential and radial electric field variations in electron root stellarator plasmas

García-Regaña

Estrada

Calvo

et al. 2018

Plasma Phys. Control. Fusion

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“…The SXR tomography diagnostic XMCTS is installed inside the plasma vessel of W7-X [18]. A schematic diagram of its mechanical design and location in the device is shown in figure 1.…”

Section: Methodsmentioning

confidence: 99%

“…The power of this method lies in the fact that, when using GPT, an objective criterion is available to guide the algorithm towards a choice of hyperparameter values that explains the data as good as possible, without requiring a too complex emission profile. The so-called evidence term in Bayes' formula (see equation (18) below) acts as a penalty for small length-scales of the inferred emission profile to limit the space of solutions to those just as complex as allowed for by the uncertainties of the observations (i.e. the measured photodiode signals).…”

Section: Methodsmentioning

confidence: 99%

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Soft x-ray tomograms are consistent with the magneto-hydrodynamic equilibrium in the Wendelstein 7-X stellarator

Schilling

Thomsen

Brandt

et al. 2021

Plasma Phys. Control. Fusion

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Soft x-ray tomograms are inferred from experimental data obtained during the recent operational phases of the superconducting, optimized stellarator Wendelstein 7-X. It is shown that the reconstructed soft x-ray emission profiles of the plasma are consistent with the numerically calculated magneto-hydrodynamic equilibrium of Wendelstein 7-X. In order to obtain reliable tomograms, the full chain of electrical and geometrical influences on the x-ray observation has to be taken into account. This has been achieved by formulation and application of an extended forward model. The forward model has been verified using phantom data derived from surrogate tomograms.

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“…The triple GEM detector was therefore proposed by ENEA in order to have a very performing and flexible device able to provide information, in combination with other diagnostics (e.g. soft X-ray multicamera tomography system [7]), to many physical processes occurring in the plasma, in particular for ambitious experiment like W7-X exploring, for the first time, an unknown territory. The ENEA proposal concerns the installation of a GEM 1D system on W7-X and is currently planned for the machine operation phase 2.0.…”

Section: W7-x Gem Installation Proposalmentioning

confidence: 99%

Results and performances of X-ray imaging GEM cameras on FTU (1-D), KSTAR (2-D) and progresses of future experimental set up on W7-X and EAST Facilities

et al. 2017

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Installation of the soft X-ray multi-camera tomography system (XMCTS) in the Wendelstein 7-X stellarator

Cited by 12 publications

References 8 publications

On-surface potential and radial electric field variations in electron root stellarator plasmas

On-surface potential and radial electric field variations in electron root stellarator plasmas

Soft x-ray tomograms are consistent with the magneto-hydrodynamic equilibrium in the Wendelstein 7-X stellarator

Results and performances of X-ray imaging GEM cameras on FTU (1-D), KSTAR (2-D) and progresses of future experimental set up on W7-X and EAST Facilities

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