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Why cosmic ray intensity needs correction with pressure?

  1. Nov 25, 2012 #1
    Hi guys,
    I cannot understand why we need to correct cosray intensity with pressure and why the equation that describes the phenomenon is I=Io*exp(-a(Δp))? I want to know the phsyical meaning of this(i assume,experimental) result...

    Thank you...
     
  2. jcsd
  3. Nov 25, 2012 #2

    mfb

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    More context would help.
    A correction where, and depending on which pressure?
     
  4. Nov 25, 2012 #3
    By pressure I mean the atmospheric pressure above the neutron monitor for example..The exact equation is:

    I=Io*exp(-a(Pi-Pm)) where:

    I=corrected with pressure intensity of cosray
    Io=the intensity recorded by the neutron monitor
    a= constant(namely the pressure coefficient)
    Pi=the atm. pressure at the time of measurment
    Po=the mean value of pressure in a particular amplitude where the measurment is taken

    thanks...
     
  5. Nov 25, 2012 #4

    Vanadium 50

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    The higher the pressure, the more material (air) is above you and the fewer cosmic rays get through.
     
  6. Nov 25, 2012 #5
    Look Vanadium 50,

    if the pressure is Pi>Pm then the argument in the exp is negative(a is positive) and exp(-a(Pi-Pm) is less than 1.So the corrected value I is less than the recorded Io,which doesn't make sense. In high pressure you supposed to record a value i.e. Io=40 and the correction should be I>Io because high pressure prevents you to count all events available,right?That's a contadiction if I am not wrong...
     
  7. Nov 25, 2012 #6

    Vanadium 50

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    Look, sctheorist (why so rude?) the sign of the correction depends on the sign of a.
     
  8. Nov 26, 2012 #7
    No no you misunderstood my friend...I used "look"' in a friendly manner..Maybe it's because I'm not american..Seriously I didn't mean to offend you or something..In my language this phrase has a different meaning..Anyway...

    I had a thought today about that..Maybe it has something to do with the equation I=Io*exp(-μχ) that refers to an absorber above your detector. χ being the length of the path within the absorber that the particle crosses..
     
  9. Nov 26, 2012 #8

    mfb

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    Maybe it is just the interpretation of the parameters:
    If I0 corresponds to Pm (I think this should be P0) and I corresponds to Pi and a is positive:
    Pi-Pm>0 (more pressure at i) corresponds to I<I0 (lower neutron flux at i).
     
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