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The lowest pressure for which the fluid equations COMSOL solves are valid is around 10 millitorr, or 1.5e-5 atm, for a typically sized inductively coupled plasma source.

Thanks a lot Daniel ...

Hello!

If the device is designed to work in outer space and vacuum, then what?
How to solve this problem? or COMSOL not able to solve these problems?
correct calculation of the plasma is done with a very low pressure (vacuum).

((Formulation which uses COMSOL for calculation of the plasma is not correct and I am ready to prove it if you are interested.))

BEST REGARDS

Hi, the answer to this really depends on the specifics of the problem. At or below around 10 millitorr, for an inductively coupled plasma, collisionless heating will become important. There are a couple of ways of handling this, one is to use a kinetic model for the description of the plasma which is not supported in COMSOL. The other way of including collisionless heating is to use an approximate method like the one described in this article:

iopscience.iop.org/0963-0252/17/2/025017

You could add this using the "General Power Deposition" feature, but it would be some work. In addition, at very low pressures the Navier-Stokes equations for the gas flow may not be valid. You may need to use one of the interfaces available in the Microfluidics module for rarefied flows. One final complication is that discharges in vacuum often include a static magnetic field to confine the discharge. Again, the fluid approximation is not valid at very low pressures when a static magnetic field is present. This is why it is not really possible to model a magnetron with a fluid model - the extreme anisotropy in the electron transport properties leads to unphysical electron loss mechanisms.

If any of the extreme conditions described above are present then you probably should use a PIC code.

Thank you very much for the detailed explanation.

Daniel, I don't understand what is PIC code!?

At Specification of the Microfluidics Module, described "vacuum Systems." is the same as 10 millitorr?

About formulas in "inductively coupled plasma", I must say that in the calculation of inductively coupled plasma in comsol, diffusion approximation is applied always, and it is a mistake!
Application of diffusion approximation depends on the pressure and size of the device and mean free path of particles.
Where not to apply the condition of the diffusion approximation, the program still take into account the diffusion approximation!
In the calculations, the program must apply thermal diffusion, but comsol doesn't to do this! (thermal diffusion factor is not used in the formulas). why?

best regards

Thank you very much for the detailed explanation.

Daniel, I don't understand what is PIC code!?

In which section I can find "microfluidics"?
I have not a separate microfluidics module!
Mikrofluidiks included in which module?

At Specification of the Microfluidics Module, described "vacuum Systems." is the same as 10 millitorr?

About formulas in "inductively coupled plasma", I must say that in the calculation of inductively coupled plasma in comsol, diffusion approximation is applied always, and it is a mistake!
Application of diffusion approximation depends on the pressure and size of the device and mean free path of particles.
Where not to apply the condition of the diffusion approximation, the program still take into account the diffusion approximation!
In the calculations, the program must apply thermal diffusion, but comsol doesn't to do this! (thermal diffusion factor is not used in the formulas). why?

best regards