Why freeze autorads?

Toumy Guettouche tguettou at newssun
Wed Nov 20 14:17:25 EST 1996

On 20 Nov 1996, Samuel C. Blackman wrote:

> My labmates and I, obviously with too much time on our hands, were 
> wondering why we put our 32P-labelled autorads in the freezer at -80C.
> Our advisor hypothesized that the low temp. promotes a more "focused"
> autorad, but without a good explanation for that.  The decay equation
> has no mention of temperature, so we're stumped.  Any ideas?
> -- Sam
> -- 
> Samuel C. Blackman        ! InterNet : blackman at tigger.uic.edu
> MD/PhD Student (4/8)      ! Disclaimer: I speak for me, not UIC!
> Univ. of Ill. at Chicago  ! Quote : "Quandro potro io finir di stupire?"
> Dept. of Pharmacology     ! Phone : 312/996-4983 (lab)  Fax: 312/996-1225

in order to get a signal on the film, silver grains in the film emulsion 
have to be excited by some stimuli( in your case x-rays). During long 
exposures some excited silver grains revert to an unexcited state and if you 
would keep your film at rt you would loose some signal. This process is, 
however, slowed down by low temperature. Ergo you can keep your cassette 
in the freezer for long excposures without the problem of loosing some signal.
I hope I did not make to many phyical terminology mistakes, but at least 
these are the basics.


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