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Re: Color Fades in discharges



Original poster: FIFTYGUY@xxxxxxx


Interesting stuff, Mike!
I would think one of the first things to do would be to put gases of known composition into your big discharge tube. Probably start with just pure N2, O2, CO2, Ar, H2O, O3, NOx's, etc, just for control. Then see what happens to a discharge in pure N2 as you add a trace of the others. Maybe by finding out what isn't getting "burnt" will help nail down what is.
I think by our minimum BPS for long sparks that there's some time-dependent effect that lasts only a few mS to allow the streamers to extend. A lifetime of a "burnt" product in the air?
Might be interesting to also run a Tesla coil discharge through your discharge tube before and after you "burn" the air (and other gases).
One wonders if the "burning" is actually due to heating by the arc, ionization of the gas, UV or other radiation, or a chemical reaction with something that IS a direct product of the discharge. Simulating the temperature of an arc without an arc might be tough, but could you illuminate/irradiate gas in the discharge tube first by exposing it to a discharge in a sealed but transparent adjacent chamber? Or could you introduce pure O3 and/or NOx's into the chamber until the air behaves "burned"?
Whatabout doing your burning in short bursts, to minimize the long-term heating effects? Is it still the same cumulative time to burn a mixture as it takes to burn it all at once?
Seems like an easy thing for us hobbyists to experiment with, as the color change is permanent, visible anywhere near standard conditions, and is apparent in ordinary air. Heck, it's not even dependent on RF, AC, or DC! Unfortunately, it may be pretty important to exclude trace contaminants.
Obviously, plasma globes don't "burn" their contents in a few minutes. Fluorescent, neon, and HID lights also last a while (although metal-halide lights do undergo a major color change early and late in their lives, and this probably due to a completely different effect?). Gas tubes don't wear out that quick, do they? Thyratrons and such last for a while, at least. So what's different about air and these gases? Doesn't oxygen "poison" plasma globes effectively?
This sounds neato. I'll play with this a bit and report back...


-Phil LaBudde