A New Type of Gas-Filled Amplifier Tube

The Raytheon Laboratories have had under development for several years a gas-or vapor-filled amplifier tube. This paper describes the general features of this type of tube and gives the detailed characteristics of some typical designs. A distinctive feature of these gas-filled tubes is the introduction of an auxiliary grid-form electrode which serves as the anode for an ionizing discharge and at the same time as a cathode for the main electron stream which is controlled in the same manner as in an ordinary high vacuum tube. Due to the close spacing of the main electrodes and the relatively low gas or vapor pressure employed, the main electron stream or plate current can be continuously controlled by the voltage applied to the control grid, increasing as the negative bias on the control grid is decreased and decreasing to cutoff as the grid bias is made more negative. Within the voltage limits of each particular design of tube the presence of gas ions between the main electrodes only serves to neutralize partially the space charge, the general form of the characteristics being the same as for high vacuum tubes. The plate resistance however is characteristically low and the mutual conductance much higher than in high vacuum tubes of comparable size. Because of the low space-charge characteristic it also follows that high values of plate current and mutual conductance may be obtained at relatively low values of plate voltage, although normal characteristics are also obtained with plate voltages of several hundred volts.