Laser‐induced fluorescence measurement of the dynamics of a pulsed planar sheath

• Published in: Physics of plasmas 1994-04, Vol.1 (4), p.1064-1074
• Main Authors: Goeckner, M. J., Malik, Shamim M., Conrad, J. R., Breun, R. A.
• Format: Article
• Language: English
• Subjects: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; CHARGED PARTICLES; COLLISIONLESS PLASMA; ELECTRODES; ELECTROMAGNETIC RADIATION; EMISSION SPECTROSCOPY; FLUORESCENCE SPECTROSCOPY; ION ACOUSTIC WAVES; ION DENSITY; ION WAVES; IONS; LASER RADIATION; NITROGEN IONS; PLASMA; PLASMA SHEATH; PLASMA WAVES; RADIATIONS; SPECTROSCOPY 700350 > Plasma Production, Heating, Current Drive, & Interactions-- (1992-); WALL EFFECTS
• ISSN: 1070-664X; 1089-7674
• DOI: 10.1063/1.870924

Using laser‐induced fluorescence (LIF) the ion density near the edge of an expanding plasma sheath has been measured. These measurements utilized a transition of N+ 2 [the P12 component of the X 2Σ+ g (ν=0)→B 2Σ+ u (ν=0) band] in a N2 plasma. The strength of the laser‐induced fluorescence was used as a measure of the temporally and spatially varying ion density. The expanding sheath was produced by applying a −5 kV pulse to a polished planar electrode in the plasma source ion implantation device [J. R. Conrad et al., J. Vac. Sci. Technol. A 8, 3146 (1990)]. The laser beam was aligned normal to the surface and was reflected off the center of the electrode. The LIF diagnostic used here is nonperturbing whereas previous researchers have used Langmuir probes, which perturb the plasma, to make their measurements. As such, the data reported here represent a benchmark measurement of pulsed sheaths and allow a better comparison between experimental measurements and theoretical predictions. It has been found that the sheath edge moves approximately 16 times faster than the ion‐acoustic velocity during the early part of the pulse, t