I stumbled across an odd idea.
If a home-built stacked-plate capacitor is operated with high-volt pulses, the thin air film trapped between the foils and the dielectric sheets should glow violet. (I verified this idea using a quickie test device made from a thin glass bowl, foil on the bottom, and salt-water on the top. Sure enough, there's a purple glow shining from the foil surface under the glass.)
Ah, but we know that plasma leads to pumping: both from ion pump effects where gas molecules embed into metal surfaces, and also from N2 turning into metal nitrides, and O2 turning into metal oxides. (Plasma does chemistry.) And there's not much air involved, so the pressure should plummet fairly fast.
So I use silicone to seal up the edges of the foil on the glass/saltwater cap, then run it for awhile. Sure enough, the purple glow changes color after a few minutes. Becomes greyish. Maybe even greenish. Might be a pressure change, or it might be contamination from the silicone caulk. I place it on the large ion chamber of a GM counter, but don't detect any rise above background count. I could keep running it for lots more minutes, but I'd burn down the contacts of my little "vacuum tester TC."
So... any Tesla coil capacitor which is sealed but which isn't vacuum-impregnated with oil is going to have plasma-filled air films, and the internal pressure is going to drop over time. And in theory, over time these air layers might pump down to non-glowing vacuum and then start emitting soft x-rays!
What to do? The whole problem might be a crackpot idea. It's all speculation (except for my glass/saltwater test.) Suggestion: paint the outside of your home-built well-sealed Tesla coil stacked-plate capacitors with ZnS glow-in-dark paint. Run them in a darkened room separate from the bright streamers and spark gap. Or instead make an xray alarm: a solar cell as sensor, painted with fluorescent paint and embedded in black epoxy or silicone.
First one to detect a dim green glow wins a prize: slightly irradiated gonads!
If the effect ever proves real, then does it mean we can replace the vacuum tube in the dentist office with a bunch of aluminum foil layers with spontaneously-appearing vacuum inside? (And would a cylindrically wrapped capacitor act as a line-source of x-rays?)
((((((((((((((((((((((( ( ( (o) ) ) ))))))))))))))))))))))) William J. Beaty Research Engineer email@example.com UW Chem Dept, Bagley Hall RM74 firstname.lastname@example.org Box 351700, Seattle, WA 98195-1700 ph425-222-5066 http//staff.washington.edu/wbeaty/