Aspects of steady-state operation of the Wendelstein 7-X stellarator

Geiger, J.; Wolf, R. C.; Beidler, C. D.; Cardella, A.; Chlechowitz, E.; Erckmann, V.; Gantenbein, G.; Hathiramani, D.; Hirsch, M.; Kasparek, W.; Kißlinger, J.; König, R.; Kornejew, P.; Laqua, H. P.; Lechte, C.; Lore, J.; Lumsdaine, Arnold; Maaßberg, H.; Marushchenko, N. B.; Michel, G.; Otte, M.; Peacock, Alan T.; Pedersen, T. S.; Thumm, M.; Turkin, Y.; Werner, A.; Zhang, D

doi:10.1088/0741-3335/55/1/014006

Cited by 26 publications

(26 citation statements)

References 19 publications

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“…To avoid undue heat fluxes on the edges of the divertor tiles, which are not designed for 10 MW/m 2 , mitigation schemes have been proposed. These include a so-called scraper element protecting these edges or electron cyclotron current drive [30], [31]. To test the mitigation schemes during OP 1.2, two of the ten divertor units will be equipped with such a scraper element.…”

Section: ) Establishing Equilibria For High-power Divertor Operationmentioning

confidence: 99%

Wendelstein 7-X Program—Demonstration of a Stellarator Option for Fusion Energy

Wolf

Beidler

Dinklage

et al. 2016

IEEE Trans. Plasma Sci.

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The superconducting stellarator Wendelstein 7-X is currently being commissioned. First plasmas are expected for the second half of 2015. W7-X is designed to overcome the main drawbacks of the stellarator concept and simultaneously demonstrate its intrinsic advantages relative to the tokamaki.e., steady-state operation without the requirement of current drive or stability control. An elaborate optimization procedure was used to avoid excessive neoclassical transport losses at high plasma temperature, while simultaneously achieving satisfactory equilibrium and stability properties at high β in combination with a viable divertor concept. In addition, fastion confinement must be consistent with the requirements of alpha-heating in a power plant. Plasma operation of Wendelstein 7-X follows a staged approach following the successive completion of the in-vessel components. The main objective of Wendelstein 7-X is the demonstration of steady-state plasma at fusion relevant plasma parameters. Wendelstein 7-X will address major questions for the extrapolation of the concept to a power plant. These include divertor operation at high densities, plasma fueling at high central temperatures, avoiding impurity accumulation, and an assessment of the effect of neoclassical optimization on turbulent transport and fast-ion confinement. A power plant concept based on an extrapolation from Wendelstein 7-X, the helical advanced stellarator, has been developed.Index Terms-Fusion power plant, steady-state magnetic confinement, stellarator.

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Section: ) Establishing Equilibria For High-power Divertor Operationmentioning

confidence: 99%

Wendelstein 7-X Program—Demonstration of a Stellarator Option for Fusion Energy

Wolf

Beidler

Dinklage

et al. 2016

IEEE Trans. Plasma Sci.

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“…Electron cyclotron resonance heating (ECRH) is the main heating mechanism in the device [1][2][3]. In its first experimental campaign, OP1.1, it was equipped with 4 MW of ECRH power as a sole source of heating.…”

Section: Introductionmentioning

confidence: 99%

Experimental investigation of the ECRH stray radiation during the start-up phase in Wendelstein 7-X

et al. 2017

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Abstract. Electron cyclotron resonance heating (ECRH) is the main heating mechanism in the Wendelstein 7-X stellarator (W7-X). W7-X is equipped with five absolutely calibrated sniffer probes that are installed in each of the five modules of the device. The sniffer probes monitor energy flux of unabsorbed ECRH radiation in the device and interlocks are fed with the sniffer probe signals. The stray radiation level in the device changes significantly during the start-up phase: plasma is a strong microwave absorber and during its formation the stray radiation level in sniffer probes reduces by more than 95%. In this paper, we discuss the influence of neutral gas pressure and gyrotron power on plasma breakdown processes.

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“…1 Electron cyclotron resonance heating (ECRH) at 140 GHz is used as the main heating mechanism in the machine. [1][2][3][4] The ECRH system will deliver up to 10 MW of microwave power in continuous regime. 2 The ECRH system is a main source of stray radiation in Wendelstein 7-X and the contribution of ECE is negligible.…”

Section: Introductionmentioning

confidence: 99%

“…6 Accurate knowledge of the stray radiation energy flux is vital for proper protection of the collective Thomson scattering diagnostic which is installed or planed on many machines [7][8][9][10] and will be installed in Wendelstein 7-X in the next experimental campaign. Hence a set of diagnostics is installed in order to monitor and control the level of non-absorbed microwave power: sniffer probes, microwave bolometers, 4 electron cyclotron absorption (ECA) diagnostic, 11 (near) infrared (IR) video cameras. 12 Sniffer probes 13 belong to the standard set of diagnostics for device safety and are, for example, installed in ASDEX Upgrade, 14 LHD.…”

Section: Introductionmentioning

confidence: 99%

Absolute calibration of sniffer probes on Wendelstein 7-X

Moseev

Laqua

Marsen

et al. 2016

Review of Scientific Instruments

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Moseev, D.; Laqua, H.P.; Marsen, S.; Stange, T.; Braune, H.; Erckmann, V.; Gellert, F.J.; Oosterbeek, J.W. Published in:Review of Scientific Instruments DOI:10.1063/1.4960349Published: 01/08/2016 Document VersionPublisher's PDF, also known as Version of Record (includes final page, issue and volume numbers)Please check the document version of this publication:• A submitted manuscript is the author's version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Here we report the first measurements of the power levels of stray radiation in the vacuum vessel of Wendelstein 7-X using absolutely calibrated sniffer probes. The absolute calibration is achieved by using calibrated sources of stray radiation and the implicit measurement of the quality factor of the Wendelstein 7-X empty vacuum vessel. Normalized absolute calibration coefficients agree with the cross-calibration coefficients that are obtained by the direct measurements, indicating that the measured absolute calibration coefficients and stray radiation levels in the vessel are valid. Close to the launcher, the stray radiation in the empty vessel reaches power levels up to 340 kW/m 2 per MW injected beam power. Furthest away from the launcher, i.e., half a toroidal turn, still 90 kW/m 2 per MW injected beam power is measured. [http://dx

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Aspects of steady-state operation of the Wendelstein 7-X stellarator

Cited by 26 publications

References 19 publications

Wendelstein 7-X Program—Demonstration of a Stellarator Option for Fusion Energy

Wendelstein 7-X Program—Demonstration of a Stellarator Option for Fusion Energy

Experimental investigation of the ECRH stray radiation during the start-up phase in Wendelstein 7-X

Absolute calibration of sniffer probes on Wendelstein 7-X

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