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    Noise-Tested Cathode Activation

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    The plate current of an electron tube producing a reasonable shot-noise level reflects the variation of the oxide cathode activity during the activation and aging process. When operating several lots of tubes at different cathode temperatures in the range from 1000 to 1500 K under stand-by conditions a set of emission curves is obtained showing maxima. A straight line is obtained by plotting the activating temperature versus time corresponding to the maxima. This is the base for developing activation schedules giving optimum activity of the cathode in the shortest time. The solution of the problem consists in an activation procedure with several temperature steps while simultaneously considering electron bombardment of the electrodes that affect the cathode activity. The net result is an approximate parallel shift of the straight line responsible for the so-called single-step activation. The position and the slope of this line in semilogarithmic representation are affected by core material and processing.

    Tubes activated thermally often undergo an emission slump during aging when high voltages are applied, especially if passive core materials are used. This phenomenon, although influenced by several processing and operating parameters, has been used as a tool for studying the effect of cathode environment upon its activity. The experiments described in this paper were performed on a pentode equivalent to the type 6 BX 6.

    Author Information:

    Dlouhy, F.
    Telefunken G. m. b. H., Ulm (Donau),

    Schuetze, H. J.
    Telefunken G. m. b. H., Ulm (Donau),

    Committee/Subcommittee: F01.06

    DOI: 10.1520/STP41247S