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Photon + photon

  1. Jul 17, 2009 #1

    Edi

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    2 photons with energies of at least 0.511 MeV are crossing the same spot at the same time - there is 1.22 MeV energy in a point, enough to create electron and positron pair. Will it happen?
    If yes, isn't it a nice way to create antimatter, or at least anti-electrons?
    If it doesn't, then one could potentially store the energy of, for example, 1Kg in space smaller than an atom and there would be no mass. It could even be much much more energy, possibly infinite. Even if its for tiniest of time scale, still - either one could relatively easy create anti-matter, or ,potentianally, store +- infinite amounts of energy in a single point (or something close to a point) without any mass created ... OR?
     
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  3. Jul 17, 2009 #2

    Vanadium 50

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    Yes.

    Well, it's not very cost-effective. It's also not very convenient since you make positrons at or near rest right next to electrons, so they can then immediately annihilate.
     
  4. Jul 18, 2009 #3

    Edi

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    Hmm, so what about HiPER? That fusion reactor. Shouldn't there be electron and positron creation before the multiple laser beams hit the deuterium-tritium (?) ball?
     
  5. Jul 18, 2009 #4

    Vanadium 50

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    Of course not. You wrote yourself 0.511 MeV. No laser puts out photons of anywhere near that energy.
     
  6. Jul 19, 2009 #5
    Not "Yes". "Probably".

    But cross-section should be sizable (order of ~0.1 barn at resonance), since it's a crossing of Compton scattering.

    People are actually working on designing photon-photon colliders. It's not too difficult to modify an electron collider to produce bunches of energetic photons, main thing needed is a powerful laser. If ILC is ever built, one of its operating modes will probably be photon-photon.

    http://tesla.desy.de/new_pages/TDR_CD/PartVI/chapter1.pdf
     
    Last edited: Jul 19, 2009
  7. Jul 19, 2009 #6

    Vanadium 50

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    No, it's observed. You see it with bremsstrahlung photons in e+e- colliders.
     
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