AVS 49th International Symposium
    Plasma Science Tuesday Sessions
       Session PS-TuP

Paper PS-TuP9
On the Limits of Operation of a Species-selective Gauge Based on the Penning Discharge Configuration@footnote 1@

Tuesday, November 5, 2002, 5:30 pm, Room Exhibit Hall B2

Session: Plasma Applications
Presenter: C.C. Klepper, HY-Tech Research Corporation
Authors: C.C. Klepper, HY-Tech Research Corporation
R.C. Hazelton, HY-Tech Research Corporation
F. Barakat, HY-Tech Research Corporation
J. Niemel, HY-Tech Research Corporation
M.D. Keitz, HY-Tech Research Corporation
J.P. Verboncoeur, University of California, Berkeley
Correspondent: Click to Email
A Penning discharge tube has been used as the excitation source for optical detection of gaseous species concentrations in a neutral gas. This type of diagnostic has been primarily used in magnetic fusion energy experiments for the detection of minority species in the effluent gas (e.g. for helium detection in a deuterium background). Recent innovations@footnote 2@ have allowed for extension of the operation range from <1Pa to as high as 100Pa and possibly beyond. This is done by dynamically varying the gauge parameters to keep the optical signals nearly constant (or at least away from a non-linear dependence on the pressure). However, there are limitations to this approach, because the Penning discharge can manifest itself in a number of modes, each exhibiting a different spatial emission pattern. As a result, varying the discharge parameters can cause the gauge to undergo transitions between these modes, disrupting any intended monotonic dependence of the overall emission on the varied parameter and hence any predicable impact on the emission. This paper discusses some of the modes observed experimentally. It also presents some progress made to date in using a particle-in-cell (PIC) code to predict these modes and mode transitions. The hope is that a good understanding of the physics involved in the mode transitions may allow for methods of either avoiding or suppressing such modes. This would aid in broadening the use of this plasma-based sensor technology. @FootnoteText@ @footnote 1@ Research sponsored in part by the US Department of Energy under contract # DE-FG02-98ER82592-A001 (Phase II SBIR) with HY-Tech Research Corporation. @footnote 2@ C.C. Klepper et al., "Species-selective pressure gauge with extended operation", US Patent No.6351131, granted Feb. 26, 2002