Why freeze autorads?

klenchin at facstaff.wisc.edu klenchin at facstaff.wisc.edu
Thu Nov 21 08:57:25 EST 1996


In article <5712r4$1sha_003 at agri.huji.ac.il>,
   MARDER at agri.huji.ac.il (Jonathan B. Marder) wrote:
->In article <57008p$1nem at news.doit.wisc.edu>, klenchin at facstaff.wisc.edu 
wrote:
->>In article <3293A2DD.6BCF at pt.cyanamid.com>,
->>   "S. Silverman" <silvermans at pt.cyanamid.com> wrote:
->>->	The absorption and emission properties of the material in 
->>->intensifying screens depend on temperature.  The screens are more 
->>->efficient at low temp.  It will take someone with more familiarity 
with 
->>->molecular orbital theory than me to give you a more precice reason.  
->>
->>I don't think so. Intensifying screens emit light upon absorption of
->>high-energy particles. Light excites silver on film. Freezer is to 
->>increase sensitivity of latter. 
->>
->>- Dima
->
->The statement about temperature-sensitivity of the screens makes sense.
->Certainly for fluorescence, yield usually goes up at low temperature.
->This is because fluorescence competes with other deactivation processes 
->which generally slow down at low temp. With a scintillant, the same 
should 
->apply. The beta radiation excites the screen. If the excitation is lost
->by non-radiative decay, then there is no emission. Low temperature 
should 
->minimize this loss and increase the emission efficiency.

Yep. It does make sense. Yield should go up with temperature. Thank you 
(and the other poster who followed my erroneous post) for pointing this 
out. I wonder now how big is this increase? O.5 -> 0.6? Bigger? 

- Dima




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