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ion motion in DC plasma
Posted Dec 4, 2013, 12:05 p.m. EST Plasma Physics 2 Replies
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Hej there, I have a problem with the DC discharge plasma. I need to simulate a plasma in a tube with a gas flow. The plasma is generated through some decay reaction in the tube (in reality due to secondary electron production). I implemented that reaction and also an inverse reaction. I have also a potential on one side of the tube and on the walls. There is also some reflectin on the walls.
The model solves but the resulting potential in the tube is orders of magnitudes to large. And there is no flux of ions even though the ion density changes.
Is there anything I have to add to make my ions move? How can I let them leave the source, with the outlet feature of my ion species the model does not solve anymore...
The model solves but the resulting potential in the tube is orders of magnitudes to large. And there is no flux of ions even though the ion density changes.
Is there anything I have to add to make my ions move? How can I let them leave the source, with the outlet feature of my ion species the model does not solve anymore...
2 Replies Last Post Jan 9, 2014, 7:48 a.m. EST
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Posted:
1 decade ago
Hey,
positiv or negativ? your potential? hopefully positive.. check your potentials at all walls.. you may miss a loss mechanism somewhere. Isn't the secondary emission coefficient of electrons high? 0.25? (0,1 is my value, forgot where i found this)
do you know the meaning of the -11.5 (electron energy)/ 0 (collision cross section) in the first row of the cross-section table of the Ar metastable relaxation with electrons? (e+Ars=>e+Ar)
thank you,
lukas
positiv or negativ? your potential? hopefully positive.. check your potentials at all walls.. you may miss a loss mechanism somewhere. Isn't the secondary emission coefficient of electrons high? 0.25? (0,1 is my value, forgot where i found this)
do you know the meaning of the -11.5 (electron energy)/ 0 (collision cross section) in the first row of the cross-section table of the Ar metastable relaxation with electrons? (e+Ars=>e+Ar)
thank you,
lukas
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Posted:
1 decade ago
Hej, I am sorry for answearing that late...
I have tried out many things, but the problem with to high (negative) potential stays the same. I have implemented elctron losses at all walls of the tube (reflectio=0 and no sencondary emission) exept 1, there is total electron reflection. The ions (tritium ions) get absorbed at all walls through a wall reaction (T+=>T) .
Does all Ions an the wall get absorbed if I set the sticking coefficient to be 1? (I need that full absorbtion at the walls...)
In reality there is an outflow of tritium and tritium ions in tube direction and T+ absorbtion (neutralization) at the side walls.
There should be something like a saturation in Electron (and ion) density but even after 5 seconds the electron density growths further. I checked the situation with the Drift Diffusion Plasma (this is without ions) and there everything looks fine (saturation of electron density, reasonable potential distribution)
So can you tell me why my electron density doesn't saturate in the DC Discharge plasma?
Thanks
Laura
I have tried out many things, but the problem with to high (negative) potential stays the same. I have implemented elctron losses at all walls of the tube (reflectio=0 and no sencondary emission) exept 1, there is total electron reflection. The ions (tritium ions) get absorbed at all walls through a wall reaction (T+=>T) .
Does all Ions an the wall get absorbed if I set the sticking coefficient to be 1? (I need that full absorbtion at the walls...)
In reality there is an outflow of tritium and tritium ions in tube direction and T+ absorbtion (neutralization) at the side walls.
There should be something like a saturation in Electron (and ion) density but even after 5 seconds the electron density growths further. I checked the situation with the Drift Diffusion Plasma (this is without ions) and there everything looks fine (saturation of electron density, reasonable potential distribution)
So can you tell me why my electron density doesn't saturate in the DC Discharge plasma?
Thanks
Laura