Re:H-3 efficiency on LSC

[ehsnet!hps (HPS)]

Reply-to: Dave.Derenzo@p0.f13.n233.z1.fidonet.org (Dave Derenzo)
Fido-To: romulus.ehs.uiuc.edu!gsosun1.gso.ur

A Packard service technician recently told me that their standards are assumed 
to be totally unquenched, but that the seal on them does not always remain 
completely intact.  These standards are originally purged with argon and flame 
sealed.  If air leaks into the standard, it is probably not unquenched any 
longer.  To tell if the seal is intact, shake the vial from side to side.  
Observe whether the bubles disappear immediately, or if a few of them hang 
around for a while after shaking.  The more bubbles that remain, and the 
longer they remain is more or less proportional to the amount of air that is 
in the vial.  Also, examine the color of the fluid.  If the fluid is somewhat 
brown or yellow, quenching has occurred.  The instructions for the quench 
standards that I have access to say that ultra-violet light will cause 
quenching (probably permanently).  One last thought is to count the standard 
on a Packard machine that has a H-3 quench curve loaded.  The counter should 
compensate for the amount of quenching by calculating what Packard calls the 
tSIE.  The DPM value should be very close to the amount stated on the vial.  A 
tSIE of 1.000 means no quenching has occurred at all.  Values lower than about 
0.9  or so should be considered suspect of quenching.  tSIE values greater 
than about 1.1 indicates the standard used to normalize the counter was 
probably quenched, and the standard is less quenched.  If you feel the 
standard used to normalize the counter is OK, and tSIEs are coming out 1.1 or 
greater, call service.

Hope this helps somewhat.   Dave Derenzo, University of Ill. at Chicago
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