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

Journal Article · Fri Apr 01 04:00:00 EST 1994 · Physics of Plasmas; (United States)

DOI:https://doi.org/10.1063/1.870924· OSTI ID:6685134

Goeckner, M J; Malik, S M ^[1]; Conrad, J R ^[2]; Breun, R A ^[1]

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1. Engineering Research Center for Plasma Aided Manufacturing, The University of Wisconsin, Madison, Wisconsin 53706-1608 (United States)
2. Department of Nuclear Engineering and Engineering Physics, The University of Wisconsin, Madison, Wisconsin 53706-1687 (United States)

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[sup +][sub 2] [the P12 component of the [ital X] [sup 2][Sigma][sup +][sub [ital g]]([nu]=0)[r arrow][ital B] [sup 2][Sigma][sup +][sub [ital u]]([nu]=0) band] in a N[sub 2] 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 [minus]5 kV pulse to a polished planar electrode in the plasma source ion implantation device [J. R. Conrad [ital et] [ital al]., J. Vac. Sci. Technol. A [bold 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, [ital t][lt]1 [mu]s, and then slows to approximately the ion-acoustic velocity after 6 [mu]s. In addition to the LIF measurements, a biased probe was used far from the cathode to determine the sheath edge location. Good agreement is found when the LIF and probe data are compared. The LIF data also are compared to the predictions of a simulation that is based on a time-varying two-fluid model of the sheath [G. A. Emmert and M. A. Henry, J. Appl. Phys. [bold 71], 113 (1992)]. While the predictions of the model show moderate agreement with the data, substantial discrepancies are observed.

• OSTI ID: 6685134
• Journal Information: Physics of Plasmas; (United States), Journal Name: Physics of Plasmas; (United States) Vol. 1:4; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700350* -- Plasma Production
Heating
Current Drive
& Interactions-- (1992-)
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
WALL EFFECTS