Space- and time-resolved measurements of ion temperature with the CVI 5292-Å charge-exchange recombination line after subtracting background radiation

An ion temperature profile has been obtained with the CVI 5292-Å (n=8 7) charge-exchange recombination (CXR) line using a space- and wavelength-resolving visible spectrometer installed on the JIPP TII-U tokamak. Two sets of 50-channel optical-fiber arrays, one viewing a fast neutral hydrogen beam (CXR channels) and the other viewing off the neutral beamline (background channels), are arranged on the entrance slit of the spectrometer. This spectrometer is coupled to an image intensifier and CCD detector at the focal plane, and provides a temperature profile every 1/60 s. An ion temperature is derived from the Doppler-broadened line profile after subtracting the simultaneously measured cold component (background channels), which is due to electron excitation and/or charge-exchange recombination in the plasma periphery. An alternative approach to obtain the ion temperature profile without CXR is also demonstrated. This method is based on an Abel inversion technique for each wavelength separately