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Electron Cloud Confinement
Posted 07.01.2013, 13:08 GMT-5 Plasma Physics Version 4.3a 1 Reply
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I am trying to model the confinement of a cloud of electrons in the center of a spherical axisymetric system. The electrons are confined by an electric potential. I was wondering if anyone had recommendations for how to best approach this. I'm new to COMSOL, so I'm not too familiar with the limitations of the different modules.
I initially attempted to use the Drift Diffusion module, but I have been running into problems with it. Since I am modeling electrons without ions, would this module be appropriate? In this simulation, I am trying to find the steady state electron density distribution starting with virtually no electrons, and a constant electron production rate in the center. I want all electrons hitting the outer boundary to leave the system, but when I run this the electron density continues increasing indefinitely. I tried using the wall, electron outlet, and flux boundary conditions, but none of them seem to be working.
I am now attempting to use the Charged Particle Tracing module. Without using an electric force, this simulation takes < 30 seconds to run to 0.1 ms. I ran the simulation for 3 days with this force enabled, and it only got to 2.7e-4 seconds. I will probably need to run this simulation to 1 ms, which would obviously take longer. Should the computation be taking this long? Also, I want to consider the interactions between the electrons. Would it make sense to multiply the particle mass and charge number by a constant, since I want to consider many more electrons than the number of particles that can be simulated?
Any insight for which of these approaches sounds more appropriate would be appreciated.
Thanks
Hello Joshua Sloane
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In terms of the module you're using, I guess the drift-diffusion is the right one. As far as I know as long as the only charged particles in your simulation are electrons drift-diffusion is the one you're looking for.
About the increment of electron density, I have similar problem with my model. My model is a corona discharge which is practically a high voltage discharge between a needle (connected to positive voltage) and a plate (which is connected to ground). What I'm expecting is, under these circumstances in the area far from needle the number density of electrons should be decreased (due to attachment of electrons to neutral molecules) and the remaining electrons should be accelerated towards the needle. But what I see is quite different. Number density of electrons in the area far from the needle is increased up to a constant number and remains like that.
It gets more strange when I decrease the voltage level this constant number does not change.
Can you please let me know about the possible solution you found for your problem?
I appreciate any other insight on this issue.