Light sensitive G-M tubes

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

	In the mid-1950s, I continuously operated 24 end window G-M tubes 
in separate lead shields (we called them "pigs") 24 hours per day, 365 
days per year, for about 5 years. About half of the time was spent 
measuring backgrounds and the other half measuring samples, including 
standards, with frequent checks on plateaus. I therefore got very good 
information on backgrounds, and, in fact, published a paper on that 
subject. On many occasions, I noticed that counters were light sensitive, 
but as long as the door of the shield was closed, this did not make any 
difference and the counters operated routinely with no background 
problems -- presumably because they were in the dark. I never changed a 
counter because of its being sensitive to light, and some of them 
operated without problems for years in that condition. 

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