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HV capacitors which emit x-rays?!!!

Discussion in 'Electronic Design' started by [email protected], Nov 27, 2006.

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  1. Guest

    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
    UW Chem Dept, Bagley Hall RM74
    Box 351700, Seattle, WA 98195-1700
    ph425-222-5066 http//staff.washington.edu/wbeaty/
     
  2. Sorcerer

    Sorcerer Guest

    |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
    | UW Chem Dept, Bagley Hall RM74
    | Box 351700, Seattle, WA 98195-1700
    | ph425-222-5066 http//staff.washington.edu/wbeaty/

    Carry on testing. I'd suggest using a TV LOPT if you have equipment
    problems.
    http://www.worldinnovations.co.uk/moreinfo.php?product_id=383&category_from=14
     
  3. 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.
     
  4. Salmon Egg

    Salmon Egg Guest

    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
     
  5. Double-A

    Double-A Guest


    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
     
  6. JoeBloe

    JoeBloe Guest

    Whenever an electron beam (even a leak discharge) or plasma strikes
    a metal surface x-rays are emitted.

    It's a rule.
     
  7. JoeBloe

    JoeBloe Guest

    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
     
  8. Do consider the kinetic energy of free electrons. In corona in air,
    that's going to be only a couple to a few eV. I don't see silicone being
    airtight enough to improve upon that much from metal reacting with air
    unless you have a vacuum pump hooked up and running.
    Even if you do remove all oxygen and nitrogen, there will be argon - at
    a pressure greater than that inside most fluorescent lamps.

    - Don Klipstein ()
     
  9. Bill, there's a question involving transfer of electrical energy on
    sci.physics.research which might benefit from your input.

    --
    Dirk

    http://www.onetribe.me.uk - The UK's only occult talk show
    Presented by Dirk Bruere and Marc Power on ResonanceFM 104.4
    http://www.resonancefm.com
     
  10. Bob Weiss

    Bob Weiss Guest

    Does it date this website?

    http://www.belljar.net/xray.htm

    Bob Weiss N2IXK
     
  11. Chris Jones

    Chris Jones Guest

  12. Bob Eld

    Bob Eld Guest

    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.
     
  13. JoeBloe

    JoeBloe Guest

    The key then would be to laminate the plate segments to their
    insulative layer with a vacuum process during construction. Should
    probably bake out any water as well. THEN seal the edges of the plate
    layers, and one could even pull a vacuum on that assembly prior to
    cure.
     
  14. smuggie

    smuggie Guest

    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 ??
     
  15. Guest


    Isn't there a vacuum inside TV picture tubes?
     
  16. Bill Beaty

    Bill Beaty Guest

    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
    UW Chem Dept, Bagley Hall RM74
    Box 351700, Seattle, WA 98195-1700
    ph425-222-5066 http://staff.washington.edu/wbeaty/
     
  17. Bill Beaty

    Bill Beaty Guest

    Definitely. But go look up "ion pump." Apparently they're common
    in small high-vac systems. No moving parts.

    If you have metal with high enough negative voltage, slowly it will
    scavange up all the remaining gas as accelerated ions become
    embedded.

    On the other hand, if the mean free path for electrons is shorter than
    the empty space inside the cap, then all you need is electrons and
    a strong enough e-field.

    ((((((((((((((((((((((( ( ( (o) ) ) )))))))))))))))))))))))
    William J. Beaty Research Engineer
    UW Chem Dept, Bagley Hall RM74
    Box 351700, Seattle, WA 98195-1700
    ph425-222-5066 http://staff.washington.edu/wbeaty/
     
  18. Bill Beaty

    Bill Beaty Guest

    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
    UW Chem Dept, Bagley Hall RM74
    Box 351700, Seattle, WA 98195-1700
    ph425-222-5066 http://staff.washington.edu/wbeaty/
     
  19. Salmon Egg

    Salmon Egg Guest

    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
     
  20. Guest

    Sure. And the electron energy is around 25-30 keV. that's
    significant.

    Mati Meron | "When you argue with a fool,
    | chances are he is doing just the same"
     
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