The design and main characteristics of fourteen-channel dispersion interferometer for plasma profile measurement and control in TEXTOR tokamak are presented. The diagnostic is engineered on the basis of modular concept, the 10.6 µm CO 2 laser source and all optical and mechanical elements of each module are arranged in a compact housing. A set of mirrors and retro-reflectors inside the TEXTOR vacuum vessel provides full coverage of the torus cross-section with twelve vertical and two diagonal
An eight channel interferometer is developed for density feedback control and the continuous measurement of electron density profiles in the stellarator W7-X. An additional sightline is launched in the geometry of the Thomson scattering for cross calibration. Due to the W7-X coil geometry access is strongly restricted. This motivates the optimization of the sightline geometry and design studies for supplementary chords. In-vessel retroreflectors will be used and inserted in the first wall elements. To cope with associated mechanical vibrations and thermal drifts during the discharges with envisaged duration of 30min either two-color or second harmonic interferometry techniques must be applied. Optimum wavelengths are found to be about 10 and 5μm. A CO2∕CO interferometer (10μm∕5μm) will be tested and compared with an existing CO2∕HeNe test interferometer. A special difficulty of remotely operated diagnostics is the need of long transmission lines with a path length of about 60m required from the diagnostics location to the torus hall and back. Different arrangements will be compared.
Articles you may be interested in CO2 laser-based dispersion interferometer utilizing orientation-patterned gallium arsenide for plasma density measurements Rev. Sci. Instrum. 84, 093502 (2013);
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 Citation for published version (APA):König, R., Baldzuhn, J., Biel, W. . W., Biedermann, C., Burhenn, R., Bozhenkov, S., ... Zoletnik, S. (2010). Diagnostics design for steady-state operation of the Wendelstein 7-X stellarator. Review of Scientific Instruments, 81(10), 10E133-1/5. [10E133]. DOI: 10.1063/1.3483210 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. The status of the diagnostic developments for the quasistationary operable stellarator Wendelstein 7-X ͑maximum pulse length of 30 min at 10 MW ECRH heating at 140 GHz͒ will be reported on. Significant emphasis is being given to the issue of ECRH stray radiation shielding of in-vessel diagnostic components, which will be critical at high density operation requiring O2 and OXB heating.
Bayesian Experimental Design (BED) is a framework for the optimisation of diagnostics basing on probability theory. In this work it is applied to the design of a multi-channel interferometer at the Wendelstein 7-X stellarator experiment. BED offers the possibility to compare diverse designs quantitatively, which will be shown for beam-line designs resulting from different plasma configurations.The applicability of this method is discussed with respect to its computational effort.PACS numbers: I. DIAGNOSTIC DESIGN USING PROBABILITY THEORYFuture fusion experiments like ITER or Wendelstein 7-X are characterised by a complex interaction of scientific and technical requirements. In result, a combination of physical questions of interest and technical boundary conditions has to be taken into account for the design of the diagnostic set-up.To assure the gain of maximum information about the physical parameters of interest, a method for the optimisation of plasma diagnostic has to take into account these conditions. A probabilistic approach is given by Bayesian Experimental Design (BED), which offers a consistent mathematical ansatz independent of the diagnostic type and the physical question to be addressed.Figure of merit is a utility function U (D, η) (see [2] for discussion), which depends on the data D of future experiments and the design parameters η. These design parameters describe the diagnostic unit to be optimised, e.g. the geometry of the line-of-sight configuration of an interferometer. Because the future data is unknown, the utility function is marginalised over the expected data space, the Expected Utility (EU) reads as EU (η) = dD U (D, η) p(D|η).
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