Re: Light Sensitive GM Tube -Reply

[Bernard L Cohen <blc+@pitt.edu>]

Paul Frame's message agrees with my very extensive experience in 
1952-1958 when I was using 24 GM tubes continuously 24 hours per day over 
the 6-year period with time roughly equally split between samples and 
background so we really had good data on backgrounds -- in fact I 
published a paper on these backgrounds. We often noticed sensitivity to 
fluorescent lights, but as long as we kept the counters dark, there was 
no problem. We never changed a counter because of light sensitivity. 

Bernard L. Cohen
Physics Dept.
University of Pittsburgh
Pittsburgh, PA 15260
Tel: (412)624-9245
Fax: (412)624-9163
e-mail: blc+@pitt.edu


On Fri, 26 Jul 1996 FRAMEP@ORAU.GOV wrote:

> A couple of additional bits:
> 
> A hole in a GM is its death knell, unless its a gas flow system (a rare
> bird).
> 
> Organic quenched (helium fill gas) end window GMs are very commom.
> Most of our end windows are of that type.  As a rule they operate at
> higher voltages than halogen quenched tubes, say 1200 -1400 V.
> 
> GMs don't have to be light tight. The end windows can be transparent. In
> fact the early GM tubes were often entirely of clear colorless glass.
> 
> We too have had our systems become light sensitive. After a while the
> counts just start going up when the fluorescent lights are turned on. Its a
> charateristic they can acquire over time, its not inherent i.e. seen in new
> tubes.
> 
> Paul Frame
> Professional Training Programs
> ORISE
> framep@orau.gov