Re: LSC and unexplained luminescence

[Sam Engelhard <mrnrge@lamar.colostate.edu>]

Melissa
In addition to what Otto mentioned you may also be experiencing Photo
luminescence the lights in your lab energize your cocktail. The solution I
use is to load your LSC and run your first count  on a blank for about a
half an hour. This gives your samples time to relax. Hope this helps.
Samuel A Engelhard (Sam) RRPT
Colorado State University Radiation Control Office
131 General Services Bldg.
Ft. Collins Co 80523-6021
(970)491-4835
MrNrge@lamar.colostate.edu

M. Woo wrote:

> Here's a puzzler...
>
> In the past couple of weeks, we've been getting very high (sometimes
> 70-80%!) luminescence readings on our liquid scintillation counter
> readouts... using *blank* samples as well as "real" samples.  Holding
> the LSC vials and recounting after a day reduces the luminescence to
> acceptable levels, so the problem is presumably not the LSC itself.
>
> The blank I made up last year is fine (<0.2% luminescence).  We have
> tried changing the scint fluid using a bottle from another lot #, as
> well as wiping the outside of the vials with water-moistened wipes and
> anti-static wipes to reduce any static buildup to no avail.  Actually,
> now that I'm thinking about it, we should probably try opening up a new
> flat of vials to eliminate them as a possibility.
>
> At this point, we're willing to accept aliens as the cause. :-)
> However, suggestions from RADSAFErs with more experience would be
> greatly appreciated.
>
> Thanks in advance!  My e-mail address should be below in my .sig.
>
> --
> Melissa Woo, Health Physicist <mailto:m-woo@uiuc.edu>
> Div. of Environmental Health & Safety
> 101 S. Gregory St., MC-225, Urbana, IL 61801
> office  217.244-7233 fax 217.244.6594 <www.uiuc.edu/ph/www/m-woo/>
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