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Absorption of Gamma Radiation

  1. May 14, 2013 #1
    After performing this experiment, we will get different peaks on the computer screen, where on x-axis lies thickness of the absorber and on the y-axis the nb of channels. What do these represent exactly? Why do we have a high peak and a medium sized one?
    What are the significances of each?

    Thanks.
     
  2. jcsd
  3. May 14, 2013 #2

    ZapperZ

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    Don't you think that it will be significantly clearer if you describe in detail the experiment (i.e. what material were you looking at), and actually show the graph of the data you are referring to?

    Zz.
     
  4. May 14, 2013 #3
    I didn't because I thought it is a known experiment.
    So here's the graph, see attachment please.
    And this is experiment aims as its title says absorption of gamma radiation by some absorber (lead for example) in order to measure its attenuation.
    What we're changing through the experiment is the thickness of the absorber.

    What I don't get is the peaks? Why do we have different peaks?
     

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  5. May 14, 2013 #4

    jtbell

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    What is your gamma source (which isotope)?

    What kind of detector are you using? I'm guessing a sodium-iodide scintillator, because it's cheap and easy to use in an undergraduate lab.
     
  6. May 14, 2013 #5
    For all isotopes, similar graphs occur with different peaks. Am just asking why do different peaks appear? Am asking a theoretical question.
     
  7. May 14, 2013 #6

    Vanadium 50

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    You were asked nicely - twice - to describe what you are doing. Making us guess is neither efficient nor polite.
     
  8. May 14, 2013 #7

    jtbell

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    I was referring to the particular picture that you attached.
     
  9. May 14, 2013 #8

    jtbell

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  10. May 14, 2013 #9
    Thank you jtbell.
     
  11. May 14, 2013 #10

    jtbell

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    So I guessed correctly, then? :wink:
     
  12. May 15, 2013 #11
    Thank you but my question was not related to what of scintillator to be used. I was asking about the meaning of the peaks. What do they represent in general. That's why I said I was asking theoretical question and materials used didn't have to do with answer I thought. But thank you for your reply, jtbell.
     
  13. May 15, 2013 #12

    Vanadium 50

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    Since you refuse to provide necessary details, this thread is closed.
     
  14. May 16, 2013 #13

    Astronuc

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    It appears one is performing gamma spectroscopy. I doubt the x-axis is absorber thickness, but rather is related to the energy of the gamma. The y-axis should be the counts (gammas detected) in the corresponding channel (gamma energy bin) on the x-axis. So already, it seems one is misinterpreting the data presented.

    The type of detector (NaI, GeLi or other) affects the resolution of the peaks.

    When one mentions absorber, it is not clear if one is refering to the detector material, or some attenuator.

    Some gamma emitters, e.g., Co-60, have two gamma peaks. The spectum in one's attachment appears to that of Co-60. Other radionuclides, e.g., Cs-137, emit one predominant gamma ray.

    The detector will also respond to lower energy gammas from internal conversion, Compton effect, and pair production.
     
    Last edited: May 16, 2013
  15. May 16, 2013 #14

    jtbell

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    It is dangerous to do this, because people may guess the missing details incorrectly. This causes people to give answers which may not be appropriate for your situation, wasting both your time and theirs.

    We have seen it happen many times, that someone makes an incorrect guess about the questioner's situation, and then the questioner has to say "no, this is what it really was..." So we're not simply nit-picking.
     
    Last edited: May 16, 2013
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