How can a gassy tube cause a flashover?>
You might read this:
http://www.allaboutcircuits.com/vol_3/chpt_13/9.html
You would expect the electrons to collide with gas molecules
within the
tube, hence to decrease plate current.>
Current in a tube with a control grid is limited by negative
electric fields that repel the electrons. Positive ions from
gas have the opposite effect.
Gas can also neutralize negative space charge around the
cathode increasing current, as well as ionize into a plasma
that has very low resistance.
Look at how much better an 866 mercury vapor rectifier
conducts than a high vacuum rectifier. Some gas rectifiers
like the 0Z4 didn't even need a hot cathode.
73 Tom
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