From: garcia22@llnl.gov (Manuel Garcia)
Newsgroups: sci.physics.plasma
Subject: Re: Modeling a plasma around a probe
Organization: Lawrence Livermore National Laboratory


In article <5ctfi9$bcn$1@jupiter.cs.uml.edu>, paal@dick.mi.uib.no (Paal
Berg) wrote:

>
> I'm trying to find a model for a probe in a plasma consisting of ions and electrons. The probe is held at a stationary potential and I'm interested in the particle trajectories given by electric(E) and magnetic(B) fields. Some facts about the problem:
>
> Spherical Langmuir probe
> Two diffent temperatures, one parallel with B and one perpendicular
> Cold plasma
> The particle density(n) is unknown
>
> If this looks familiar and you have a written code in Fortran, then tell me! One major problem is the temperature. If I'm using a Boltzmann distribution (n proportional to exp(-qp/T), where q is charge, p is potential and T is temperature) what is T? I'
>
> Literature about solving this numerically is hard to find. If anyone have some suggestions of literature, you can also mail me.
>
>
> Paal Berg

References to consider:

1) F.F.Chen, "Electric Probes," in "Plasma Diagnostic Techniques" by
R. H. Huddlestone, and S. L. Leonard, 1965, Academic Press.

2) Chung, Talbot Touryan, "Electric Probes in Stionary & Flowing Plasmas:
Theory & Application," 1975, Springer-Verlag.

3) Swift and Schwar (?) about 1971 (England?).

Much depends on the range of your parameters: collisional (fluid)?,
collisionless (particle)?, gyroradius versus probe diameter, gyrofrequency
versus collision frequency (magnetized?), Debye and sheath lengths versus
probe dimension. A topic similar to this is planar magnetron cathodes.
These are magnetized cathodes used in low density gas discharges as
sputtering sources. Modeling these involves similar issues: transverse
B-fields, sheaths, density gradients. Models here range from simplistic to
Monte Carlo (megasimplistic). Perhaps a sucessful modeler in this field can
give you a code you can adapt. Reference 2) has the most complete
discussion of the parameters and types of theories appropriate to each
parameter range, a good place to start. In the end the only theory that
will work will be your own.
--
Manuel Garcia
LLNL L-153
POB 808, Livermore, CA 94550
(510) 422-6017
garcia22@llnl.gov
garcia22@popgun.llnl.gov