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Why cosmic ray intensity needs correction with pressure?

by sctheorist
Tags: correction, cosmic, intensity, pressure
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sctheorist
#1
Nov25-12, 01:02 PM
P: 4
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...
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mfb
#2
Nov25-12, 02:17 PM
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P: 11,925
More context would help.
A correction where, and depending on which pressure?
sctheorist
#3
Nov25-12, 02:44 PM
P: 4
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...

Vanadium 50
#4
Nov25-12, 03:59 PM
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P: 16,385
Why cosmic ray intensity needs correction with pressure?

The higher the pressure, the more material (air) is above you and the fewer cosmic rays get through.
sctheorist
#5
Nov25-12, 06:11 PM
P: 4
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...
Vanadium 50
#6
Nov25-12, 07:34 PM
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P: 16,385
Look, sctheorist (why so rude?) the sign of the correction depends on the sign of a.
sctheorist
#7
Nov26-12, 10:55 AM
P: 4
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..
mfb
#8
Nov26-12, 11:01 AM
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P: 11,925
Maybe it is just the interpretation of the parameters:
Quote Quote by sctheorist View Post
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...
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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