Measurements of the ion drift velocities in the presheaths of plasmas with multiple ion species

We have used a variety of diode lasers to perform laser-induced fluorescence (LIF) measurements that were the first to test the Bohm Criterion for multiple ion species plasmas. These measurements led to the discovery that a collective effect, ion-ion instability enhanced friction, is important for sheath formation in multiple ion species plasmas. New LIF schemes were pioneered in order to complete these experiments with diode lasers. With respect to a new LIF scheme for KrII, accessible to diode lasers, challenges remain fielding an ion flow diagnostic in low temperature plasmas