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Laser Amplified By Plasma

  1. Jun 17, 2007 #1
    Recently I read the thread "Giant Solar Laser" in the General Astronomy Forums. The author, Ruslan_Sharipov, writes
    I was just wondering if someone could explain specifically how a laser will be amplified when passing through plasma. Thank you for your time.
     
  2. jcsd
  3. Jun 18, 2007 #2

    Astronuc

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    I am not sure that a plasma - free ions and electrons - can be using in a lasing process like that in gas lasers. Lasers utilize metastable states in which an electron 'drops' to lower energy level when 'stimulated' by a photon of the characteristic energy difference. That is why lasers are monochromatic, more or less.

    I would like to see the theory and the wavelengths proposed.

    Hopefull Mr. Sharipov will submit his theory to Independent Research.
    https://www.physicsforums.com/forumdisplay.php?f=146

    Plasmas can be used for lasing, e.g. http://laserstars.org/history/plasma.html ,
    but that is not the same as a solar plasma.

    One would have to distinguished between partially ionized gas and highly ionized.

    Typically I think of gas lasers as various combinations of He-Ne-Ar-Kr-Xe-F and CO2, as opposed to solar plasmas which are mostly H and He.
     
    Last edited: Jun 18, 2007
  4. Jun 19, 2007 #3
    Thank you.
     
  5. Jun 20, 2007 #4
    It can as long as the ions aren't fully stripped, meaning the ions have bound electrons that can in the right circumstances be in metastable states. This is how laboratory x-ray lasers are made, and they work the same way as conventional lasers except they're typically amplified spontaneous emission rather than resonator cavities. A lot of work went into their development in the '80s and '90s, and a small x-ray laser research field still exists, though the hoped-for applications for the most part didn't pan out.

    Free electron lasers are rather different beasts, perhaps this is what he had in mind - http://en.wikipedia.org/wiki/Free_electron_laser. This requires a relativistic electron beam.

    I have no idea what he's thinking about based on what he posted.

    Edit: I just saw the related locked thread below and realized the idea appears not to be founded in science... Also, Astronuc, the Reagan-era SDI laser concepts were plasma-based x-ray lasers, not chemical lasers, though this can't have anything to do with the poster's ideas either.
     
    Last edited: Jun 20, 2007
  6. Jun 20, 2007 #5

    ZapperZ

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    Er... FEL is totally out of the question here. The requirement for the electron beam (i.e. ultra low emittance and low energy spread) would never be fulfilled by a plasma that is highly unstable. Even the high gradient achived in plasma accelerators have not touted that technique as being able to be used to generate FELs.

    Zz.
     
  7. Jun 20, 2007 #6

    mheslep

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    A bit of topic but this 'stripped' case is the one in which Im interested. Im well versed in the electron stimulation by quanta, but lack even the vocabulary to go googling for what happens when a photon hits a nucleus - ion w/ no electrons. I assume there must still be quantum energy states for nuclei? Are there there the equivalent absorption / emission processes? Id appreciate some pointers for where to begin, or even the appropriate terms.

    mheslep
     
    Last edited: Jun 20, 2007
  8. Jun 20, 2007 #7
    There have been proposals for gamma-ray lasers based on excited nuclear isomers, this link talks a bit about the idea and provides other links you can chase down if you're interested: http://en.wikipedia.org/wiki/Gamma_ray_laser. I think one major problem is gathering enough material to see a significant effect. But this can't have had anything to do with the poster's solar laser idea either...
     
  9. Jun 20, 2007 #8

    mheslep

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    Many thanks
     
  10. Jun 24, 2007 #9
    The solar plasma does not consist of fully stripped ions only. Remember the discovery of helium or read the following link: http://www-solar.mcs.st-and.ac.uk/~clare/Lockyer/helium.html.
     
  11. Jul 8, 2007 #10
    we all know that plasma cis a big source of radiations.i.e xrays,ions,electrons etc.i want to know tat how these xrays are emitted from plasma.plz tell me thanks
     
  12. Jul 8, 2007 #11

    Astronuc

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    I know. One of my professors in grad school was involved with nuclear-pumped lasers, including X-imer (Excimer), and other SDI concepts. Interesting stuff. :biggrin:

    My research interest was high power density systems capable both steady-state and transient power capability. It was dual-use technology, and I was interested in propulsion rather than weapons applications.

    Certainly. In my original response, I was primarily thinking of solar plasma, as opposed optically-pumped gas (He, Ne, Ar, . . .) lasers.

    I was hoping there would be a better description of the proposed "Giant Solar Laser".

    Certainly poly-electronic atoms can be partially ionized, i.e. lose one or more electrons and still have bound electrons.

    A proton is a hydrogen ion - there is only one electron. One could have H2+. However, in general, hydrogen plasmas are largely protons, electrons and some concentration of neutrals. Li and on up can certainly have poly-electronic positive ions.
     
    Last edited: Jul 8, 2007
  13. Jul 8, 2007 #12

    mheslep

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    I was only interested in nuclear excitation - no bound electrons, as in a plasma. From up thread, my question was what happens when a proton/nucleus is hit by a photon. The answer seems to be an excited nucleus or nuclear isomer can result if the photon is in the gamma ray range. If the photon is of lower energy then I'm not sure what happens. At much lower wavelengths/energies then I fall back on a simple E-M wave interaction w/ the nucleus where the E & M parts of the wave would oscillate the charged particle and simply push it around as it passes, but it is not a nuclear excitement.
     
  14. Jul 8, 2007 #13

    Astronuc

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    Well think about the energy of a gamma photon required to excite a nucleus - it has to come from a nuclear source in the first place or one heck of an EM interaction.

    The cross-section for photon-electron interaction is much greater than for a photon-nuclear interaction, and one is more likely to get pair-production for E(gamma) > 1.022 MeV, although there are a number of isotopes for which photo-neutron emission is a possible interaction.

    At lower gamma/X-ray energies, Compton and photoelectric effects dominate.
     
  15. Jul 9, 2007 #14

    mheslep

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    Yes I see that from here that only very large energies are allowed, apparently only at multiples of 1/2 spin? Though, I don't anything about why 1/2 spin is a fundamental nuclear quantity. Some Standard Model concept I suppose.
    Yes I see in Boyd and Sanderson's text that the ponderomotive force works by pushing electrons about which in turn creates an electrostatic gradient that pulls the +ions along.
     
  16. Jul 12, 2007 #15
    Just a guess, MIT? :smile:
     
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