HV capacitors which emit x-rays?!!!

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 snipped-for-privacy@chem.washington.edu UW Chem Dept, Bagley Hall RM74 snipped-for-privacy@eskimo.com Box 351700, Seattle, WA 98195-1700 ph425-222-5066 http//staff.washington.edu/wbeaty/
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Carry on testing. I'd suggest using a TV LOPT if you have equipment problems. http://www.worldinnovations.co.uk/moreinfo.php?product_id83&category_from 
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I don't know about that, but I do remember a "science experiments" book from my high school library that suggested using a color television high voltage rectifier tube as an X-ray source.
That source (plus the fact no book would _dare_ suggest any such thing nowadays) dates the book.
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Michael Moroney wrote:

That's why those tubes have metal shielding.

When I hooked up a sheet of aluminum foil to an old TV high voltage supply, it sounded like ants were rustling across the aluminum as little blue sparks jumped off!
Double-A
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On Mon, 27 Nov 2006 17:52:05 +0000 (UTC), snipped-for-privacy@world.std.spaamtrap.com (Michael Moroney) Gave us:

Bone up on the forum you invade.
Quote who you are replying to.
http://tools.ietf.org/html/rfc1855 http://en.wikipedia.org/wiki/Top-posting
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Michael Moroney wrote:

Does it date this website?
http://www.belljar.net/xray.htm
Bob Weiss N2IXK
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Michael Moroney wrote:

You underestimate the internet!
http://www.belljar.net/xray.htm http://xray.uu.se/hypertext/VacNews2.html http://www.noah.org/science/x-ray /
Chris
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Michael Moroney wrote:

And anyway it doesn't work! Well, if you find an old enough tube I guess it does. In the 1970s they switched over to lead glass in the rectifiers and in the CRT faceplate.
If we ignore the cancer danger, x-rays aren't that bad. For example, a typical dental x-ray head cannot give you an x-ray burn. It takes a year or two to get enough of a dose to give the mildest burn, and your skin will heal faster than it's damaged. It's like weak sunlight: too dim to get a sunburn.
((((((((((((((((((((((( ( ( (o) ) ) ))))))))))))))))))))))) William J. Beaty Research Engineer snipped-for-privacy@chem.washington.edu UW Chem Dept, Bagley Hall RM74 snipped-for-privacy@eskimo.com Box 351700, Seattle, WA 98195-1700 ph425-222-5066 http://staff.washington.edu/wbeaty /
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There shouldn't be much radiation from the rectifiers. The current only flows in the forward direction and the voltage drop shouldn't be big enough for x-ray production.
The old sets used a shunt regulator for the high voltage. This definitely could be a problem.

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On 11/26/06 10:04 PM, in article snipped-for-privacy@14g2000cws.googlegroups.com, " snipped-for-privacy@eskimo.com"

I will try to discourage you. The light you see is probably corona. You need to have high energy electrons (tens of keV's) to get any x-rays with penetrating capability. Electrons traveling in a gas, ionized or not, will just not reach sufficient energy because of collisions with air molecules. If you end up gettering the air to get a vacuum you will not get electrons except from photoemission or field emission. If you apply a voltage high enough to achieve that, you are likely to destroy your metal coatings well before you get x-rays.
A similar technique has been used for image intensification. In that case, you might get electron energy in the tens of eV's. Look up image intensifiers.
Bill -- Fermez le Bush
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Box 351700, Seattle, WA 98195-1700

need
I agree, X-rays will not be generated because the electons in the corona have lost most of their energy in molecular collisions with the gases present. Secondly, even if X-rays were formed, they wold be very low energy because the voltage is low by X-ray standards. At best, the photons could only be a few kV or so and would barely penetrate a piece of paper.
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Wrong,
harmful X-rays were well known side effect of the first color TVs in the 1950's, and also of some high voltage tubes.
Why do you think there is 30 pounds of LEAD in today's 27 inch TV tube ??
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smuggie wrote:

Isn't there a vacuum inside TV picture tubes?
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snipped-for-privacy@gmail.com writes:

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Gave us:

Not true. Who ever fed you that crap?
ALL CRT type TVs emit *some* x-rays. It is from the electron beam striking the aperture grille (not lead either, btw). There are not now, nor have there ever been emissions from the sides of the tube, so no, there are NOT ANY 30 Lb lead linings in ANY CRTs.
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JoeBloe wrote:

Err... the faceplate of the typical color TV is LEADED GLASS, i.e. lead oxide dissolved in the silicate glass. It contains about 4 lb of lead, and it might have total weight of the glass equal 30 lb.
And the most important X-rays aren't from the aperture grille (which is typically chrome/nickel/iron) because those have mainly K line emission which is in the 4 keV range; not low enough for high number of photons, and not high enough to get through much shielding. The most important are from the phosphors (rare earth types) which have L edges at 8 keV or so, which is a tad more penetrating, as well as involving more candidate electrons per atom.
Simple plasma (St Elmo's fire) doesn't get to high enough temperature for significant X-ray output, though some laser plasma techniques can achieve this.
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On 29 Nov 2006 00:03:47 -0800, snipped-for-privacy@gmail.com Gave us:

No.... He said 30Lb of lead. That would be in addition to the glass weight.

Electrons striking metal is all that is needed. There are target materials that are better than others.
If a 25kV stream striking a palladium target gives off a flux, then a single static spark into the same target will give of an emission as well, it just may not be one we can easily detect or quantify. The same event occurs in both cases, it's just that in the case of the stream there are far more events.
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Salmon Egg wrote:

Agreed.
Wrong. What do you mean by "gas?" We have to consider the issue of pressure and mean free path for electrons.
For example, the old-style Roentgen x-ray tubes would stop working if pumped down to really hard vacuum. They did not operate by field-emission alone, instead they required electrode collisions with the trace of gas ions remaining. Before GE/Coolidge introduced hot-filament x-ray tubes around the 1930s, non-filament medical x-ray tubes would include a small gas-generator (such as a piece of coal) in a glass side-arm. If the internal pressure decreased too much because of ion-pumping effect,
the coal-chunk could be warmed in order to restore the (low) pressure.

Yet the old-style Roentgen tubes worked just fine.
If we slowly reduced the electrode spacing in those old tubes, what effects would arise that could prevent proper operation?
On the other hand, the dielectric sheets exposed to plasma would spew out ions and raise the gas pressure. Even quartz would generate oxygen. So use intrinsic silicon wafers as the dielectric?
:)
((((((((((((((((((((((( ( ( (o) ) ) ))))))))))))))))))))))) William J. Beaty Research Engineer snipped-for-privacy@chem.washington.edu UW Chem Dept, Bagley Hall RM74 snipped-for-privacy@eskimo.com Box 351700, Seattle, WA 98195-1700 ph425-222-5066 http://staff.washington.edu/wbeaty /
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On 11/28/06 9:54 AM, in article snipped-for-privacy@14g2000cws.googlegroups.com, "Bill Beaty"

Sorry about that. I agree. The mean free path has to be long enough for the electron to gain energy between collisions. I was not thinking about that for the small gaps at relatively high pressure found in capacitors.
Residual gas can help in the formation of electron beams. The ions can neutralize space charge repulsion effects and help keep beams focused.
Bill -- Fermez le Bush
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Salmon Egg wrote:

If plasma effects cause the capacitor to pump itself down, and if the (glass?) dielectric doesn't release too much gas under plasma bombardment, then the pressure within the capacitor might drop quite low.
Here's a 2005 paper where a small crude x-ray generator is made from a 2cm diameter PP plastic syringe pumped down to only 3e-2 Torr, with 2 to 3 KVDC applied. The photos show that it glows brightly. Apparently with close electrode spacing you can get significant x-ray output, even while the pressure is still high enough to give a bright visible discharge. But they did use a 150um Be window to let the soft x-rays get out. (Maybe even a neon sign produces x-rays, but they can't penetrate the glass?)
The paper shows a spectrum with a big peak around 2KeV or so, and a tail going up above 4KeV. I wonder if 2KeV x-rays would get through the metal foils and dielectric layers of a stacked-plate capacitor? If they do, then a large stack of layers would obviously contribute to x-ray intensity. But unless hydrogen ions would rapidly get ion-pumped deep into the metal foil layers, this whole plasma pump-down trick might not work with plastic or waxpaper dielectrics.
Simple X-ray Emitter, Murakami et. al. http://www.jstage.jst.go.jp/article/analsci/21/7/21_881/_article
((((((((((((((((((((((( ( ( (o) ) ) ))))))))))))))))))))))) William J. Beaty Research Engineer beaty chem.washington.edu UW Chem Dept, Bagley Hall RM74 billb eskimo.com Box 351700, Seattle, WA 98195-1700 ph425-222-5066 http://staff.washington.edu/wbeaty /
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