Cold Cathode Valves and
Air-Cooled Kenotrons
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Cold Cathode Valves |
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Air-Cooled Kenotrons |
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Machlett ML8094/199 and Machlett-Raytheon
ML5578/200 |
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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, put on the
market years later).
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 solid state semiconductor rectifiers replaced kenotrons in 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,
rectifier valves were of the cold-cathode (filament-less) type. Four of them
are presented in this series.
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