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

Abstract

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 ( T i ) 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 ( T i ∼ 2  keV) prioritizing T i measurements while also considering the ion velocity flow resolution. The experimental set-up is shown and the diagnostic calibration procedure for T i 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 T i maps are presented and validated against standard Charge eXchange Recombination Spectroscopy T i profiles, finding excellent agreement.