Design and Calibration of a Polychromator for the Thomson Scattering at Wendelstein 7-X

Schmuck, S.; Dinklage, A.; Fischer, R.; Knauer, J.; Kurzan, B.; Mürmann, H.; Pasch, E.

doi:10.1063/1.2909107

Cited by 4 publications

(4 citation statements)

References 9 publications

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“…The spectral analysis of the scattered light is performed with filter based polychromators. The preliminary arrangement of W7-X polychromators was discussed in [26]. The optical design is for numerical aperture of 0.37 and fiber bundles with diameter of 3 mm.…”

Section: The W7-x Thomson Scattering Systemmentioning

confidence: 99%

The Thomson scattering diagnostic at Wendelstein 7-X and its performance in the first operation phase

et al. 2017

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The optimized stellarator Wendelstein 7-X started operation in December 2015 with a 10 week limiter campaign. Divertor experiments will begin in the second half of 2017. The W7-X Thomson scattering system is an essential diagnostic for electron density and temperature profiles. In this paper the Thomson scattering diagnostic is described in detail, including its design, calibration, data evaluation and first experimental results. Plans for further development are also presented. The W7-X Thomson system is a Nd:YAG setup with up to five lasers, two sets of light collection lenses viewing the entire plasma cross-section, fiber bundles and filter based polychromators. To reduce hardware costs, two or three scattering volumes are measured with a single polychromator. The relative spectral calibration is carried out with the aid of a broadband supercontinuum light source. The absolute calibration is performed by observing Raman scattering in nitrogen. The electron temperatures and densities are recovered by Bayesian modelling. In the first campaign, the diagnostic was equipped for 10 scattering volumes. It provided temperature profiles comparable to those measured using an electron cyclotron emission diagnostic and line integrated densities within 10% of those from a dispersion interferometer.

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Section: The W7-x Thomson Scattering Systemmentioning

confidence: 99%

The Thomson scattering diagnostic at Wendelstein 7-X and its performance in the first operation phase

et al. 2017

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“…Nd:YAG lasers are the working horse in many TS systems worldwide, because the lasers are robust. The wavelength (λ =1064 nm) is in the near infrared region were plasma background light is low and sensitive detectors 5 (silicon avalanche diodes) for the detection of the scattered light are available. The well-known λ =1064.14 (1064) nm transition provide the lowest threshold of laser lines in Nd:YAG crystals 4 and is therefore widely used; the W7-X TS diagnostic is now equipped with three such lasers 3 .…”

Section: Double Wavelength System Layoutmentioning

confidence: 99%

“…This paper will discuss the layout of the double laser set-up, its benefits, and demonstration for its use as an in-situ calibration method. A detailed description of the TS system layout and TS data analysis in W7-X can be found in the literature 3,4,5 .…”

Section: Introductionmentioning

confidence: 99%

Dual-laser wavelength Thomson scattering at Wendelstein 7-X

Pasch

Beurskens

Bozhenkov

et al. 2018

Review of Scientific Instruments

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This paper presents the approach of the dual-laser wavelength Thomson scattering (TS) system for the Wendelstein 7-X stellarator. The dual-laser wavelength TS method is based on two lasers with different wavelength fired quasi-simultaneously. This method has two advantages compared to a single laser wavelength TS system. First, the dual laser availability allows an in-situ spectral calibration and secondly, higher electron temperatures can be measured without any change of the spectral filter setup of the polychromators. The W7-X dual-laser wavelength TS concept is based on high power lasers: a set of standard Nd:YAG lasers with λ=1064 nm wavelength and a Nd:YAG laser with λ=1319 nm wavelength newly developed for this application. This laser uses a different transition line with 34% efficiency compared to the main 1064nm Nd:YAG line. Simulations of the expected performance of the new dual-laser wavelength system show, that electron temperatures up to Te =15 keV can be measured compared to the original design parameter up to Te=10 keV. The in-situ spectral calibration can be performed using a range of temperatures from 1keV to 10 keV using TS measurements of the 1064 nm versus 1319 nm TS simultaneously.

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“…The scattered light is collected onto optical fiber bundle arrays and relayed a long distance to the polychromator, which are located at the Thomson diagnostic room. The shape of each fiber bundle input is designed to be rectangular with a fixed surface (7 mm 2 ) which corresponds to the circular shape (3 mm diameter) of each fiber bundle output according to the polycromator design 2 . The optics are optimized for spectral range from 700 nm up to 1064 nm according to the Thomson scattering spectra of electron temperature up to 10 keV.…”

Section: Optical Designmentioning

confidence: 99%

Design and Study of the Observation Optics for the Thomson Scattering Planned at Wendelstein 7-X

Cantarini

Knauer²,

Pasch

2008

AIP Conference Proceedings

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The main aim of the Thomson scattering system is the measurement of electron temperature and density profiles with high time and spatial resolution. To cover the whole laser beam line (1.6 m) through the plasma cross section, two ports are provided for the observation optics, which image the scattering volumes (each with 28 mm length and 9 mm diameter) onto fiber bundles. The observation optics are important components of the diagnostic set-up, because their imaging properties determine the spectral and spatial resolution of the whole system. Therefore the design of the optics must be optimized according to the geometrical constrains of the observation ports in terms of position and dimensions. To optimize this optical engineering, the commercial ZEMAX program is used. The composition of the optical system is elaborated to minimize losses of collected light with wavelength from 700 nm up to 1064 nm. Environmental criteria (e.g. neutrons, ECR plasma heating and temperature) will be considered choosing optical materials. First results of calculations will be presented.

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Design and Calibration of a Polychromator for the Thomson Scattering at Wendelstein 7-X

Cited by 4 publications

References 9 publications

The Thomson scattering diagnostic at Wendelstein 7-X and its performance in the first operation phase

The Thomson scattering diagnostic at Wendelstein 7-X and its performance in the first operation phase

Dual-laser wavelength Thomson scattering at Wendelstein 7-X

Design and Study of the Observation Optics for the Thomson Scattering Planned at Wendelstein 7-X

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