Air-Cooled Kenotrons
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Kenotrons are vacuum rectifying hot-cathode valves of the diode type,
used until the Seventies in the high tension circuits of x-ray tubes. The
first Kenotron was introduced by Saul Dushman in 1914 (the K3 of General
Electric).
Early kenotrons were of a remarkably large size in order to ascertain
adequate cooling in the ambient air. Later makes were fitted,
like x-ray tubes, with some sort of metal heat radiator fixed to the anode
end of the tube. But finally, like x-ray tubes, kenotrons became smaller in
their external size and were oil immersed in the high-tension
transformer tank of the x-ray unit.
In the late Sixties and during the Seventies semi-conductor rectifiers
replaced kenotrons in the high tension generators. Most modern x-ray units
are presently equipped with electronically controlled high frequency
generators.
Prior to the invention of the kenotron in 1914, rectifiers were of the
cold cathode (filament-less) type. Two of them are presented in this
series. |