GB744315A - Improvements in or relating to electron tubes - Google Patents

Abstract

744,315. Thermionic valves. WALLMARK, J. T. March 13, 1953 [March 14, 1952], No. 7027/53. Class 39 (1). In a " space-charge deflection valve " of the kind described in the Proceedings of the Institute of Radio Engineers, Volume 40, pages 41-48, current and voltage conditions in the deflection space are chosen so that the " beam deflection transconductance " decreases with increasing current and that the total transconductance (which is the product of the beam deflection transconductance and the " beam current transconductance " which necessarily increases with increasing current) is, over a substantial region, independent of beam current. This is shown'in Fig. 5, in which beam current transconductance g<SP>1</SP>m, beam deflection transconductance g<SP>11</SP>m, and total transconductance g m , are plotted as a function of #, the ratio of the actual current to the maximum current at which a virtual cathode forms at the reflector. The valve comprises cathode 1, control grid 2 and screen grid 3, which produce two symmetrical beams travelling within deflection electrode 5 to the output system consisting of interceptor 6 and anode 7 with or without dynode 8 and focusing members such as 9. The beam 4 is reflected to an extent which depends upon the space charge and thus the distribution of the beam between electrode 6 and 7 depends upon the current variation produced by grid 2, and assists it. The conditions under which the total transconductance is rendered independent of the beam current and hence of undesired fluctations in working conditions is explained in detail with reference to diagrams. Generally, # is between 1 and 2, so that a virtual cathode is present at the reflector; and the ratio of voltage on electrode 3 to the absolute value of the negative voltage on 5 is best at about 0.005 and ceases to be useful above 0.25.