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 reesolution 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.