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Need to preionize xenon lamp with somethingium

  1. Jun 21, 2010 #1
    We're building a very high power xenon flashlamp with electrodes so far apart that some kind of pre-ionization is necessary to start the discharge. I dump 10,000 volts across the electrodes so I just need a few loose electrons to get the ball rolling.
    I've been using a Tesla coil to get a glow-discharge inside the bulb but that's a pain. The high-voltage high-frequencies like to go places they're not supposed to go (capacitor banks, furniture, people!), the corona scares people, and the ozone stinks. It can be immersed in transformer oil (I do) but the oil is messy. It's big & cumbersome.
    I can use a trigger electrode but that means another power supply - also a pain.
    I thought a little ionizing radiation might do the trick. I'd like to put something very very mildly radioactive just pressed against the outer wall of the bulb: thorium, americium, radium, some-other-ium. I don't want to put it inside the bulb since the plasma of a 100megawatt discharge get's kinda hot. So the radiation has to penetrate the 1/4 inch thick quartz wall of the bulb.
    Welding rods contain a little thorium to start the arc. As I understand it, thorium is mostly an alpha emitter and alpha particles don't penetrate much. Would alpha radiation penetrate that much quartz? If not, would beta or gamma or (shudder) neutron radiation do the job? What would be an easy (& safe) source. We don't want to sterilize any grad students. They're already grumpy.
  2. jcsd
  3. Jun 21, 2010 #2
    Use Krypton 86. It's a mild beta emitter used for exactly that purpose commercially.
  4. Jun 21, 2010 #3
    Krypton is a gas. I was thinking of something solid. I know Krypton is used in some bulbs. Is that the isotope commonly used? I could affix a small Krypton bulb to my big Xenon bulb.
  5. Jun 21, 2010 #4
    Yes, it's the commonly used gas, and yes you can include a small capsule of it nearby. A solid will vaporize and interfere with the lamp. Krypton being noble will not harm the optics of the lamp.
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