There was a comment a while back about emission from a tungsten-thoria
filament being the result of carburization. I had been under the impression
that the thorium was used to enhance emission. And that as it evaporated, the
emission would decrease. Well, here's the answer from Eimac's Web site:
"By proper processing during vacuum pumping of the tube envelope, the metallic
thorium is brought to the surface of the filament wire, and emission increases
approximately 1000 times. The thoriated tungsten filament is also carburized.
The small amount of tungsten carbide formed in the carburizing process reduces
the evaporation rate of the thorium and thus increases the life of the
filament."
FYI, the URL is: http://www.eimac.com/cf.htm
73's
Chris, KF0FX
KF0FX@aol.com
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