Laser-induced quenching diagnostics of hydrogen atoms in fusion plasma

Laser-induced quenching (LIQ) is a new diagnostic technique developed for hydrogen and hydrogen-like ions with degenerate excited states. The technique is proposed for use in the local measurements of hydrogen parameters (density, temperature, velocity distribution etc) in the scrape-off-layer and divertor plasmas of tokamaks and other fusion devises. The H α quenching effect was simulated via a dynamic collision-radiative model developed for the hydrogen atom. The model has also been applied to both analyze the performance of various spectroscopic schemes and to evaluate saturation effects and quenching signals. It is suggested that the LIQ technique could be use to measure hydrogen density as well as electron density from analysis of the quenching-to-fluorescence ratio. Experimental testing was performed in a glow discharge plasma with a pulsed wavelength-tunable OPO laser and in a Globus-M2 tokamak with a time-modulated 1875 nm fiber laser.