The Plasmatron, A Continuously Controllable Gas-Discharge Developmental Tube

The "plasmatron," a new type of continuously controllable gas tube, is described and its operation analyzed. This tube utilizes an independently generated gas-discharge' plasma as a conductor between a hot cathode and an anode. Continuous modulation of the anode current can be effected either by variation of the conductivity or the effective cross section of the plasma. The first of these is accomplished by the modulation of the electron ionizing beam which controls the plasma density and hence its conductivity. The second method makes use of the gating action of positive-ion sheaths which surround the wires of a grid located between the anode and cathode. The plasmatron appears to have considerable promise for such applications as motor drive, direct loudspeaker drive, high-efficiency rectification and inversion, and the many other uses which require the high-current and low-voltage operation that the high-impedance vacuum tube cannot supply.