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Updated: Jun 13, 2025

Spatial Separation of Molecular Conformers and Clusters
Published on: January 9, 2014
Measurement of Stark-split beam and carbon charge exchange emissions for simultaneous B-field and
R Albosta1, B Geiger1, G McKee1
1Department of Engineering Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
Abstract:
A set of two newly designed, single-channel Czerny-Turner spectrometers has been deployed at the DIII-D tokamak for measurements of the motional Stark effect (MSE) split beam emission and the C6+ (CVI) carbon charge exchange recombination (CER) emission at high spectral (δλ = 0.13 nm) and temporal (1-5 kHz) resolution. High throughput optics (f/# = 2.8) allow for good signal-to-noise at high time resolution using fast EMCCD detectors. The MSE emission allows for spectral fitting of the magnitude and direction of the local B-field, while the carbon emission yields local ion temperature and toroidal rotation information. To reduce so-called Doppler broadening of the MSE emission, a new channel-specific variable lens-masking approach has been developed. Experimental data collected from the 2023 DIII-D experimental campaign demonstrate the signal quality and instrument fidelity for both diagnostic measurements. Moreover, initial CER data analysis shows a clear evolution of the toroidal rotation during edge localized modes. Initial progress on the advanced MSE model, including a new validated ray-trace model of the DIII-D collection optics, is shown via sensitivity analysis.
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