To design a bias circuit (constant current source) for a plasma discharge, is there an "equivalent circuit model" for the plasma itself to simulate the circuit?
I'm trying to do both: DC and RF plasma and I need a constant DC & RF current
Thank you
If you don't care about the nonlinear of the plasma discharge, you can get a simple L-R series equivalent circuit by fluid model which is used to calculate the conductivity. You would find more details to find the equivalent circuit's parameters in this book "Principles of Plasma Discharges and Materials Processing" by Michael A. Lieberman.
Thanks Lige,
I tried what you said, however I cant find numerical values for several paramters including:
- electron and ion densities
- charge state
- ion mass
- electron neutral collision frequency
for Nitrogen plasma at atmospheric pressure
How can I calculate them ?
Note that I'm only trying to simulate the biasing circuit.
NO ! The volt-ampere values of a discharge must be measured empirically.
Plasma has well-defined electrical characteristics that can be reproduced by an equiv. cct, in which plasma impedances are modelled as the appropriate electrical components (R, C, L, etc.). This is simple and experimental values of impedance can be directly used in equations.
The sheath impedances are capacitive but include parallel resistive losses due to ipn acceleration through sheath.
The bulk impedance is resistive, due to electron-neutral collisions (hence a function of pressure), but at high frequency (RF) a parallel inductance must be included to take into account of electron inertia.
You have to measure the discharge characteristics (cur-vol) values of a discharge empirically.
The plasma discharge devices have specific I-V curve. It is in form of an S-Curve.
There are two types of models: the physical model and the behavioral model.
The simplest form of the behavioral model is the piece wise linear models. The I-V can be composed of the three linear pieces. The off branch, the on branch and the negative resistance part connecting the two pieces.
It has also a small signal linear model with R-C-L in parallel.
To operate the device into certain point it is advisable to use a consatnt current source. You can build this consatnt current source according to the measured characteristics of the tube.
It can be handled as any other electronic device.
Best wishes
Please look at the work by
Professor Serafim
from
Northeastern University
in
Boston, MA
on
Plasma
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