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Paper PS-MoP16
A Novel Approach to Time Resolved Langmuir Probe Measurements

Monday, October 29, 2001, 5:30 pm, Room 134/135

Session: Plasma Diagnostics and Plasma-Surface Interactions Poster Session
Presenter: A.K. Jindal, University of Texas at Dallas
Authors: A.K. Jindal, University of Texas at Dallas
S.K. Kanakasabapathy, University of Texas at Dallas
M. Goeckner, University of Texas at Dallas
L.J. Overzet, University of Texas at Dallas
Correspondent: Click to Email
Langmuir Probes, when used carefully, have provided spatially resolved plasma density, potential, and electron temperature measurements. However, time resolved Langmuir Probe measurements are time consuming in triggered box car averaged systems. We present a novel approach to time resolved Langmuir Probe I-V curve acquisition. Probe Current and voltage are measured as functions of time, for a fixed applied DC bias, with a digitizing oscilloscope. These traces are collected and a new applied bias is set. By doing this repeatedly, we build up I-V-t profiles. Then, in an offline fashion, time is eliminated between these various traces and I-V curves are obtained for all instances of time in the pulse period. In contrast to state of the art triggered box car averaged systems, I-V curves are obtained with better time resolution and much faster. For example: I-V curves for 512 instances of time within a 1 msec pulse period with 300 points in voltage, is obtained in as little as 15 minutes. Once these time resolved I-V curves are obtained, appropriate probe theory is used for extracting time resolved plasma parameters using a Levenberg-Marquardt@footnote 1@ fitting algorithm. The high speed of data acquisition minimizes the effects of long-term plasma drift associated with slower techniques. We shall be presenting data from pulsed Chlorine and Argon discharges using this technique. . @FootnoteText@ @footnote 1@W.H. Press, S.A. Teukolsky, W.T. Vetterling, and B.P. Flannery. NUMERICAL RECIPIES in C: The Art of Scientific Computing. Cambridge University Press. .