Laser-induced fluorescence measurement of argon in argon-xenon plasma sheath boundary with tunable diode laser

Summary form only given. The Bohm sheath criterion in single and two-species plasma is studied with laser-induced fluorescence (LIF) using a diode laser. Xenon is added to a low pressure argon unmagnetized DC hot filament discharge confined by surface multidipole magnetic fields. The argon II transition sequence at 668.614 nm is adopted for optical pumping to detect the fluorescence from the plasma. The laser diagnostic system is first calibrated with an iodine cell and wavelength meter because of its small mode-hop free regions. The regions of the plasma sheath and presheath are determined from the plasma potential profile measured by an emissive probe. The ion concentrations of the two-species in the bulk plasma are calculated from measured ion acoustic wave phase velocity. The measured phase velocity combined with the argon data from LIF is used to determine the xenon ion velocity. The spatial profiles of ion drift velocities are compared to predictions of mobility-limited flow velocities and to the generalized Bohm sheath criterion