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Tritium watch

  1. Apr 9, 2010 #1
    Is this real tritium in there? Is tritium expensive? Is it radioactive? How does it compare to natural sources of radioactivity?

  2. jcsd
  3. Apr 9, 2010 #2


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    Staff: Mentor

    It won't be surprising if it was real tritium, it is used in such applications. You can buy small tritium powered glow sticks on eBay.

    Yes, it is radioactive, it decays by beta decay, emitting an electron. From what I remember energy of the electron is too low to get outside of the vial or (in this case) clock, it is stopped by thin paper.

    Edit - that's what I meant:

  4. Apr 9, 2010 #3
    Oh, thanks for the technology update :)

    And there is no chance that the beta radiation will ionize something which itself will emit radiation which can leave the vial?

    And what about the Bremsstrahlung?
  5. Apr 9, 2010 #4


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    I'd like to see comparison pictures of the vials when they are 10 years old. I know they say that they are good for a quarter of a century but tritium's half-live is like 12.5 years or so. On my Speedmaster, after 12 years, the tritium is worthless. I would imagine they would really have to pack in the tritium or have found a much more efficient means of luminescing.
  6. Apr 9, 2010 #5


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    Staff: Mentor

    Actually - that's how it works. Energy from the beta radiation is converted to light which leaves the vial.

    I suppose your main question/concern here is how safe these things are and how does the amount of energy they can emit compare to that from natural sources. No idea. First thing to check would be to find out how much tritium each vial contains.

    Electron from the decay has energy in the keV range, that is converted to visible light - eV range. One decaying atom gives enough energy to emit thousands of visible light photons (probably much less in reality), so even such a single event should be easily visible and several per sec could give the impression of continuous light.

    But I am just guessing here.
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