Laser induced fluorescence of argon ion in plasma presheaths

Abstract

Summary form only given. A tunable diode laser system has been used to measure ion velocity distribution functions of ArII in plasma presheaths using laser-induced fluorescence (LIF). The diode laser system can examine the velocity distribution function with marginally greater resolution than the dye laser owing to their smaller line width (0.001 nm) (Severn et al., 1998). LIF of ArII requires excitation at 668.61 nm. The diode laser is centered at that wavelength with a tuning range of 0.15 nm and the optical amplifier (MOPA) is at 10 nm. LIF measurements of presheaths as a function of pressure (0.5-3 mTorr) were made in a DC hot-filament produced multidipole plasma discharge near a negatively biased plate. The ion velocity has range of 10/sup 3/ cm/s-10/sup 5/ cm/s for presheaths thickness 0.5 cm-5 cm. These measurements are compared with results obtained by using a double sided Langmuir probe (Mach probe) and an emissive probe.