Re:H-3 efficiency on LSC

[Max deLaubenfels <madness@u.washington.edu>]

	Regarding your question about LSC efficiency being related to the
cocktail being used, it has been my experience that it does.  Different
fluids will have different ingredients and will therefore respond to
radioactive emissions in slightly different ways.  Recently we decided to
switch from using a toluene based coctail to a sewer disposable one and I
was faced with the task of determining efficiencies with the new fluid. 
All of the standards available were toluene based so I had to make some
with the new stuff.  Its a long story, but in the end it worked quite
well and we had a nice efficiency/quench chart.  The new efficiencies were
about 12% smaller than we got with the old fluid, which is okay, but it
does illustrate the point in question.  The biggest challenge was finding
calibrated sources of activity that were in mediums miscible with the new
fluid.  If your coctail is compatible with water you can purchase
exact quantities of various nuclides from the National Bureau of
Standards.  If water is incompatible with the fluid you are using then you
may have more trouble finding sources that will work.  Perhaps there are
some people on the net that can help us out with that question.  Anyhow,
best of luck!

Max deLaubenfels
Radiation Safety, EH&S
University of Washington, Seattle, WA

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