Measurement of Stark-split beam and Carbon charge exchange emissions for simultaneous B-field and temperature/rotation analysis at DIII-D*

A set of two newly designed, single-channel Czerny-Turner spectrometers [1] has been deployed at the DIII-D tokamak for simultaneous measurements of the full Motional Stark Effect (MSE) Split Deuterium or Hydrogen Beam Emission and the Carbon CVI charge exchange emission at high spectral (0.13 nm) and temporal resolution (2-10 kHz). 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. A new channel-specific lens-masking approach has been developed and installed to reduce the doppler broadening effect for the MSE emission. To that end, data has been collected from the 2023 DIII-D experimental campaign, focusing on measurements of fast changes in the magnetic field structure due to modifications of the bootstrap current – as well as rotation changes – during the ELM cycle. Initial results towards the evolution of the toroidal rotation and bootstrap current during ELMs will be presented. This requires fitting of the MSE emission, which involves generating tables of pyFIDASIM spectra and accounting for non-equilibrium excitation populations using a stark-shifted quantum collision model.

 

[1] Albosta R et al.: Rev Sci Instrum. 2022 Nov 1