Light Sensitive GM Tube -Reply

[FRAMEP@ORAU.GOV]

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