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Secondary radiation from alpha particles?

  1. Apr 30, 2009 #1
    This is probably a naive question, but I've been trying for awhile to figure it out myself and just don't have the background to do so. I know that beta particles can generate x-rays through bremsstrahlung processes, and that some materials excited by alpha particles can generate light through subsequent electron relaxation, such as Zinc Sulfide. I also know that alpha particles can eject neutrons from lightweight materials, like beryllium. However, I was curious about whether alpha particles of ordinary velocity (e.g. 5.5MeV) can induce high energy emanations (such as x-rays or gamma rays) through some process I'm not aware of from different types of materials (e.g. ordinary air vs. aluminum vs. steel vs. silicon) that they bombard. I'm not very familiar with the energy that is emitted when ions recombine or when electrons jump between shells (except for visible light), but I'm guessing those processes would be the sources of most "secondary radiation" from alpha particles. The thing that got me thinking about these possibilities was pondering the construction of smoke detectors that have alpha particles hitting air and whatever metal they use for shielding, and even silicon computer processors that experience periodic alpha particle bombardment from their packaging. I know all that energy from the alpha particles has to go somewhere, and wonder if any of it ends up as high-energy rays. Thanks!
     
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  3. Apr 30, 2009 #2

    Astronuc

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    The interaction of alpha particles with Be nucleus is a special case. For other nuclei, the alphas scatter or ionize atoms. Those atoms remove atomic electrons as they slowdown. As electrons recombine with atoms, they release photons which are characteristic of the energy levels in those atoms which are in the range of IR, visible, UV and low energy X-ray.

    I'm not aware that silicon computer processors experience bombardment from their packaging. Alpha emitters are heavy elements Po on up.
     
  4. Apr 30, 2009 #3
    "In the early days" radiation was a problem (random, non-recurring errors). It turned out to be from the packaging. As I recall, it was only the ceramic packages.

    Sorry, no references.

    Neil
     
  5. Apr 30, 2009 #4

    Astronuc

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    I know that some Si was 'doped' by neutron irradiation, but I believe that was Si logs loaded in a neutron source, e.g. a small nuclear reactor. Perhaps the Si became contaminated(?) by ballistic mixing with neutron activated capsule material (?).

    Light elements (Bi and below) undergo beta decay (with some gamma emission), positron emission, or electron capture.
     
  6. May 1, 2009 #5

    jtbell

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    Maybe the packaging was made from Fiesta Ware. :biggrin:
     
  7. May 1, 2009 #6

    Vanadium 50

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    That's not too far from the truth. There are trace amounts of uranium and especially thorium pretty much everywhere, unless you take steps to prevent it. Likewise with lead-210, if its been near anywhere with radon.

    People who do experiments requiring radiopurity have to work quite hard to keep these isotopes away.
     
  8. May 1, 2009 #7
    Very interesting! In the references I read on alpha particle shielding they didn't mention the possibility of any shielding materials generating x-rays as a by-product of alpha particle "absorption." Do you think that's just because the amount of alpha particle energy converted to x-rays is too low-level to pose any danger?
     
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