Why the plasma gather in center of the inner grid?

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jpnms
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Why the plasma gather in center of the inner grid?

Post by jpnms »

Under low rough vacuum, the plasma cover the inner grid like the picture, [img][img][/img][/img]but under high vacuum, it gather in center of inner grid.

What is the difference between the two situations theoretically?
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Richard Hull
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Re: Why the plasma gather in center of the inner grid?

Post by Richard Hull »

Higher pressures only cause the item to act like a gas glow lamp. A simple NE-2 bulb fed with DC will have only one electrode glow brightly as the neon is at a relatively high pressure.

At lower pressures, in a fusor, the glow appears only at the electrostatic focus of the system, (center), where ions and electrons collide and de-ionize to cause the glow. This special region is very narrow and difficult to maintain by the neophyte, but much easier once experience is gained. This is where the device can start to do fusion under the right voltages and pressures.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Dan Tibbets
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Re: Why the plasma gather in center of the inner grid?

Post by Dan Tibbets »

The appearance of the glow discharge varies based on several factors, the pressure probably being the greatest contributor. A major consideration is the Mean Free Path of an electron or ion. This is based on the density and the temperature of the gas/ plasma. It may be as little as sub Microns (micrometers) to kilometers. Then you can consider Debye lengths, Ashton Breakdown voltage, etc. There have been books written about it. Back in the day of vacuum tubes, good understanding of these processes was required, now it is not studied much in main stream physics, except for perhaps the vacuum coating and plasma processing fields.

A place to start if you wish to gain a moderate understanding may be this link:

https://www.google.com/search?q=glow+di ... 66&bih=634


Dan Tibbets
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