Re: [sdpd] intensity dimension

[pstephens...@notes.cc.sunysb.edu]

Arbitrary Units. 

One usually measures counts in a detector, but because the x-ray beam 
intensity from a synchrotron source generally varies in time, one 
normalizes that measured intensity to some kind of incident beam monitor. 
Furthermore, it is frequently the case that one wants to count longer at 
higher angles, but the analyzed data should represent intensity per unit 
incident dose. 

For example, data at NSLS X16C is usually (not always) handled as counts 
per 10^6 monitor counts.  The monitor is an ion chamber feeding a current 
amplifier feeding a voltage to frequency converter, so the 10^6 monitor is 
a rather indirect unit!  It happens to be approximately the usual average 
data collection time, so the a.u. are frequently on the order of the 
actual measured x-ray counts.

^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~
Peter W. Stephens
Professor, Department of Physics and Astronomy
Stony Brook University
Stony Brook, NY 11794-3800
fax 631-632-8176




"Seyed Reza" <alavi419...@yahoo.com> 
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[sdpd] intensity dimension









Hi all
I have a question that may be is very elementary.
I saw some graphs in articles that is about phase determination by
synchrotron rediation.
in vertical axis for intensity in the brackets it has been written
[a.u.] .
I want to know what does it mean?
Best regards 
Reza

 


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