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Ionization, neutralization, electrical breakdown etc.

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tendor
#1
Mar23-14, 08:00 AM
P: 11
Hi,
could someone direct me or recommend me some materials which deal with those problems?

I would like to get deeper understanding of it (I know it requires qm), see how exactly such things happens and be able to quantify it (not just with phenomenological theory).

For example when I get charged and move myself near enough to the metal door frame a spark will occur, or when I take piezo lighter - the electrode has "big enough charge/at same sharper places big enough electric field" that it's able to ionize the air around it.

But does it use already existing ions, or is it strong enough to create new ones? What exactly happens in processes of ionization and neutralization between an atom of particular gas and a certain metal (more elaborately than simple statement that electron jumps/tunnels from one thing to another)? Does an ion of some gas always neutralize itself when it "collides" with zero voltage (grounded) piece of metal? And so on...
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ZapperZ
#2
Mar23-14, 08:50 AM
Emeritus
Sci Advisor
PF Gold
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P: 29,238
The phenomenon is more complex that most people realize. In fact, in accelerator/high gradient studies, this is still an ongoing research area.

The most popular model for breakdown in vacuum, for example, has the following steps:

1. Surface geometry that is sharp has high field-enhancement factor.

2. High fields cause electrons to be emitted via field-emission (tunneling). Regions around high field enchancement factor will emit more since the field is higher there.

3. The field-emitted electrons gain energy from the external field.

4. These electrons collide with residual gasses, creating ions.

5. As this goes on, the ions and electrons separate due to the external field. The ions are attracted towards the emitter surface while the electrons are pushed away.

6. The ions that crash onto the surface may, in turn, generate even more residual gas specie into the region above the surface of the emitter.

7. This process continues until you get a trigger point in which this ignites a plasma cascade that we call a "spark".

The process in air occurs earlier and easier than in vacuum due to the higher density of gasses to be ignited.

If you have access to IEEE articles, the best paper to read is by F. Schwirzke, IEEE Trans. Plasma Science v.18, p.690 (1991).

Zz.


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