Re: High count with LSCh

[Ninni Jacob <njacob@gsosun1.gso.uri.edu>]

On Mon, 16 Mar 1998, HALEEM  MAHMOUD SAID wrote:

> Date: Mon, 16 Mar 1998 14:46:49 -0600 (CST)
> 
> I have this question regarding high count rate with the liquid 
> scintillation counter.  Whenever a sample of oil vacuum pump of 
> anccelerator is counted I get high count rate with initial count.
> However, when the sample is counted again latter on, the response is 
> numerical value, and the value keep decreasing when counted repeatedly 
> over time until stalbilizes latter on like 24 hours latter.  The same 
> thing occurred when counting saliva samples.  I was wondering if any of 
> you could give an explanation for this situation either from past 
> experience or an educated guess.  Your help is very much appreciated.
> Thanks.
> 
> 

The high counts are due to "Chemoluminescence", that is:"random single
photon events which are generated as a result of the chemical interaction
of sample components". It is due to the presence of certain chemicals in
the sample.
Yes, the counts do go down with time.
It also helps to "dark adapt" the samples.


Ninni Jacob
Radiation Safety Officer
University of Rhode Island/
Rhode Island Nuclear Science Center
16 Reactor Road
Narragansett,RI 02882

Phone: (401) 789-9391
Fax:   (401) 782-4201
email: njacob@gsosun1.gso.uri.edu