This paper describes the design of the Thomson scattering system at the Wendelstein 7-X stellarator. For the first operation campaign we installed a 10 spatial channel system to cover a radial half profile of the plasma cross section. The start-up system is based on one Nd:YAG laser with 10 Hz repetition frequency, one observation optics, five fiber bundles with one delay line each, and five interference filter polychromators with five spectral channels and silicon avalanche diodes as detectors. High dynamic range analog to digital converters with 14 bit, 1 GS/s are used to digitize the signals. The spectral calibration of the system was done using a pulsed super continuum laser together with a monochromator. For density calibration we used Raman scattering in nitrogen gas. Peaked temperature profiles and flat density profiles are observed in helium and hydrogen discharges.
The Thomson scattering system at Wendelstein 7-X
Contributed paper, published as part of the Proceedings of the 21st Topical Conference on High-Temperature Plasma Diagnostics, Madison, Wisconsin, USA, June 2016.
E. Pasch, M. N. A. Beurskens, S. A. Bozhenkov, G. Fuchert, J. Knauer, R. C. Wolf, W7-X Team; The Thomson scattering system at Wendelstein 7-X. Rev. Sci. Instrum. 1 November 2016; 87 (11): 11E729. https://doi.org/10.1063/1.4962248
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