The discussion centers on the behavior of argon plasma when subjected to electric currents and its effects on solid objects, particularly in terms of field types and potential damage. When argon gas is ionized into plasma, it generates a negative charge on immersed objects due to the formation of a Langmuir sheath, which accelerates argon ions and can cause etching or destruction depending on the plasma's strength and temperature. The participants also explore methods for protecting machinery from plasma damage, such as using sacrificial foils and magnetic fields, and discuss the calculations needed to achieve specific pressures in a plasma system, referencing the ideal gas law and particle density.
PREREQUISITESResearchers, engineers, and hobbyists working with plasma technology, particularly those involved in plasma etching, ionization processes, and equipment protection in high-energy environments.
Khashishi said:A solid object immersed in a plasma will become negatively charged, due to the formation of a Langmuir sheath.
http://farside.ph.utexas.edu/teaching/plasma/Plasmahtml/node41.html
This negative charge will accelerate argon ions into the surface of the object, causing some etching on the surface.
If it's a weak plasma (low ionization fraction) at low temperature for a short time, then the damage might be negligible, or maybe just cosmetic. For a strong high temperature plasma, it will melt or sputter the materials it comes in contact with, and eventually destroy it.
also another thing, is there a way to protect the solid object immersed in plasma? Insulators coating or anything?Khashishi said:A solid object immersed in a plasma will become negatively charged, due to the formation of a Langmuir sheath.
http://farside.ph.utexas.edu/teaching/plasma/Plasmahtml/node41.html
This negative charge will accelerate argon ions into the surface of the object, causing some etching on the surface.
If it's a weak plasma (low ionization fraction) at low temperature for a short time, then the damage might be negligible, or maybe just cosmetic. For a strong high temperature plasma, it will melt or sputter the materials it comes in contact with, and eventually destroy it.
another issue i wish that you could help me with is that i need to calculate the amount of argon gas and the electric current so that when argon gas is transformed to plasma by electric current it exerts pressure X. How do i calculate the amount of gas needed and the amount of electric current needed to exert pressure X assuming it's in a certain container with volume of 10,000 litres. what is the formula itself?Khashishi said:You can cover your things with some sacrificial foil. How long that lasts depends on the parameters of the plasma. Magnetic fields can redirect the plasma so you could use magnets to protect certain parts of your equipment
thank you so much!Khashishi said:Well,
PV = nkT
where n is the density of particles in the plasma. If it's mostly neutral, then n would be the density of argon. I imagine your system is fairly low ionization fraction, so the pressure is probably close to the neutral pressure. But what do I know about your system
'If ionization is significant, then the density would be the sum of the electron density, ion density (of each ionization stage), and neutral density. The electrons and ions and neutrals probably have different temperatures, so you would add them.
##P = P_{ion} + P_{electron} + P_{neutral}##
where ##P_{ion} V = n_{ion} k T_{ion}##, etc...
It's kind of difficult to get quantitatively accurate values for the temperatures and densities of each ionization state. You can try looking at the description of the MIST code
R.A.Hulse, Nucl. Tech./Fus. 3, 259 (1983)
It's for fusion-like temperatures, which I imagine is much hotter than what you are working with, but maybe it could help you understand the equations.