Laser-induced fluorescence of helium ions in ITER divertor

Laser-induced fluorescence (LIF) on ITER will be used for local measurement of helium density n(He) and ion temperature T-i in divertor. The LIF diagnostic is combined with the divertor Thomson scattering (DTS) via common laser injection and signal collection optics. Collisional-radiative model developed for helium ions is used to estimate laser parameters required for robust measurement of laser-induced signals against plasma background radiation. The estimations demonstrate feasibility of measuring n(HeII) with laser parameters provided by available optical parametric oscillator pumped by Nd:YAG. New approach for measuring T-i is proposed and the expected errors are estimated using numerical simulations.