A feasibility study for the use of core charge exchange recombination spectroscopy on ITER has
shown that accurate measurements on the helium ash require a spectrometer with a high etendue
of 1mm2sr to comply with the measurement requirements [S. Tugarinov et al., Rev. Sci. Instrum.
74, 2075 (2003)]. To this purpose such an instrument has been developed consisting of three separate
wavelength channels (to measure simultaneously He/Be, C/Ne, and H/D/T together with the
Doppler shifted direct emission of the diagnostic neutral beam, the beam emission (BES) signal),
combining high dispersion (0.02 nm/pixel), sufficient resolution (0.2 nm), high efficiency (55%),
and extended wavelength range (14 nm) at high etendue. The combined measurement of the BES
along the same sightline within a third wavelength range provides the possibility for in situ calibration
of the charge eXchange recombination spectroscopy signals. In addition, the option is included
to use the same instrument for measurements of the fast fluctuations of the beam emission
intensity up to 2 MHz, with the aim to study MHD activity.