Laser-induced fluorescence for ITER divertor plasma

Laser-induced fluorescence diagnostics on ITER will be used for local measurements of helium density (nHeI) and ion temperature (Ti) in the divertor area. The diagnostics is combined with divertor Thomson scattering via common laser injection and signal collection optics. Multichannel filter polychromators with design similar to those developed for Thomson scattering will be used to perform spectral analysis of the fluorescent signals. Both the fluorescent signals and the background radiation are estimated using the collisional-radiative models developed for He I and He II. The estimations demonstrate the feasibility of measuring nHeI with the temporal resolution 20 ms and accuracy ΔnHeI