Laboratory testing of the space-charge-sheath electric thruster concept

The mechanism of ion extraction from a weakly ionized plasma has been investigated using a quadrupole mass spectrometer. The plasma was generated in a flow system by means of a high frequency discharge.It could be shown that the picture given by PAHL has to be extended by considering a space charge sheath spread over several mean free ion paths in front of the plane extraction probe, used. Two effects, resulting from the space charge, have been found observing the behaviour of nitrogen ions. First, the directional distribution of the extracted ions may be different for different ions. Second, ion-molecule reactions may be caused by the field strength within the sheath varying with both ion number density and probe voltage. In the case of N4+ ions the Varney reaction seems already to start in the static sheath. In order to minimize influences from the space charge, it is suitable to apply a slightly positive potential with respect to the container wall.

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Asymptotic theory of a collision-dominated space-charge sheath with a velocity-dependent ion mobility

Journal of Plasma Physics ◽

10.1017/s0022377801001556 ◽

2002 ◽

Vol 67 (2-3) ◽

pp. 163-173 ◽

Cited By ~ 10

Author(s):

M. S. BENILOV ◽

R. N. FRANKLIN

Keyword(s):

Electric Field ◽

Space Charge ◽

Ion Mobility ◽

Asymptotic Theory ◽

General Structure ◽

Debye Length ◽

Path Model ◽

Rigid Spheres ◽

Space Charge Sheath ◽

Quasineutral Plasma

The method of matched asymptotic approximations is used to examine an ordering of the physical quantities in a collisional plasma–collisional sheath model that has not been previously explored, namely in the constant ion mean free path model with high electric field. The asymptotic theory for a collision- dominated space-charge sheath at a negative surface is developed for the case when the ions interact with neutral particles as rigid spheres while the electric field is high both in the sheath and in the quasineutral plasma. The ion mobility is inversely proportional to the square root of the electric field in such a case. The ratio λD/L of the Debye length at the center of the quasineutral plasma to a characteristic dimension of the plasma is considered as a small asymptotic parameter. The general structure of the asymptotic solution obtained is similar to that in the case of low electric field (or in the framework of the model of constant collision frequency), considered by previous workers; however, the scalings are different. In particular, the thickness of the sheath is found to have the order λ4/5DL1/5, while the respective order in the case of low electric field is λ2/3DL1/3.

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Transition from plasma to space-charge sheath near the electrode in electrical discharges

IEEE Transactions on Plasma Science ◽

10.1109/tps.2005.856484 ◽

2005 ◽

Vol 33 (5) ◽

pp. 1481-1486 ◽

Cited By ~ 20

Author(s):

M. Keidar ◽

I.I. Beilis

Keyword(s):

Space Charge ◽

Electrical Discharges ◽

Space Charge Sheath

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The Influence of Collisions in the Space Charge Sheath on the Ion current Collected by a Langmuir Probe

Contributions to Plasma Physics ◽

10.1002/ctpp.2150350102 ◽

1995 ◽

Vol 35 (1) ◽

pp. 3-14 ◽

Cited By ~ 17

Author(s):

P. Spanel ◽

D. Smith ◽

O. Chudacek ◽

P. Kudrna ◽

M. Tichy

Keyword(s):

Space Charge ◽

Langmuir Probe ◽

Ion Current ◽

Space Charge Sheath

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