Progress on the motional Stark effect with laser-induced fluorescence diagnostic (invited)

Abstract

The motional Stark effect with laser-induced fluorescence (MSE-LIF) diagnostic is presently under development as a new technique for measuring magnetic field pitch angle and magnitude in plasmas in a wide range of conditions. The technique is based on the observation of LIF from the set of H-alpha transitions in a diagnostic hydrogen neutral beam. As the beam passes at a high velocity through a background magnetic field, the H-alpha emission is split and polarized in a way that is dependent on the magnetic field. The magnitude can be determined from the line splitting and the direction from the polarization orientation. This paper will describe the principle of the technique and report on the present status, including the successful measurement and interpretation of an LIF enhancement phenomenon. The LIF signal from a 30kV beam in a background of neutral gas was found to be enhanced, and the fine-structure line amplitudes were seen to vary significantly with an applied perpendicular magnetic field of 0–0.01T. MSE-LIF for plasmas in the intermediate field range of greater than 0.1T, and potential advantages of MSE-LIF will also be covered.