First measurements with a Coherence Imaging Charge Exchange Recombination Spectroscopy (CICERS) diagnostic at Wendelstein 7-X

Abstract

In this work, the Coherence Imaging Spectroscopy technique is exploited for active charge exchange radiation measurements to infer high spatial resolution 2D ion temperature (Ti) maps in the core region of Wendelstein 7-X plasmas. A synthetic model of the diagnostic is developed and used for the optimization of the hardware components for the expected ion temperatures (Ti ∼ 2 keV) prioritizing Ti measurements while also considering the ion velocity flow resolution. The experimental set-up is shown and the diagnostic calibration procedure for Ti measurements is introduced. A combination of both simulations and experimental calibrations enable high fidelity system group delay ( ∂ϕ ∂λ ) characterization in the whole visible spectral range. Finally, the signal processing techniques applied to the diagnostic signal are introduced and first measurements of 2D Ti maps are presented and validated against standard Charge eXchange Recombination Spectroscopy Ti profiles, finding excellent agreement.