Patent GB-732738-A (GB)
Title: Improvements in and relating to gaseous arc high frequency generators
IPC: H03B11/08
Filed: 1953-04-20
Abstract: 732,738. High-frequency discharge apparatus. GENERAL ELECTRIC CO. April 20, 1953 [April 30, 1952], No. 10743/53. Class 39 (1). [Also in Group XL (c)] In an arc constriction oscillator comprising a gaseous arc-discharge tube provided with a cavity resonator whose excitation gap is positioned in the arc-discharge path, a member which defines the gap also defines an orifice constricting the cross-sectional area of the path. In the construction shown a generally toroidalshaped resonator 4 comprising upper and lower annular members 8 and 9 and an outer cylinder 10 is positioned in the discharge path between a mercury pool cathode 2 and an anode 3. The cross-section of the resonator may be circular, rectangular or otherwise shaped, provided that standing waves may be established at the desired output frequency. Two coaxial cylinders 6 and 7 connected respectively to the upper and lower members 8 and 9 provide a constricting orifice 5 for the arc discharge and a narrow annular excitation gap 11. The diameter of the orifice 5 is preferably less and its length greater than the mean free path of electrons in the gaseous discharge. If desired, the upper cylinder 6 alone can be dimensioned to define the limiting orifice and can be separately supported independent of the resonator. The mercury cathode 2 is contained in a cupshaped metallic member 12 the edge of which is sealed to a glass cylinder 13 which is in turn sealed to a metal ring 14 welded to the member 9. The anode 3 is supported by a resilient ring 15 sealed to a glass cylinder 16 which is in turn sealed to a metal ring 17 hermetically secured to the member 8. A plate 20 secured to the anode 3 covers a central bore therein and carries input and output tubes 21 and 22 for water or another fluid coolant. When mercury vapour is the ionizable medium, a starting electrode 23 supported by a rod 24 sealed through the cathode cup 12 is preferably employed to establish a cathode spot. If an ionizable gas such as hydrogen or an inert gas is employed, such starting means are not necessary. A concentric transmission line section 18 provides means for coupling energy from the resonator to a load such as an antenna. On connecting a battery 25 between the cathode 2 and anode 3 a gaseous arc is established with the aid of the starting electrode 23. An inductor 27 and an adjustable resistor 28 provide means for controlling the time constant of the charging circuit, which determines the time required for the discharge to increase to the quenching point. An intermediate tap of battery 25 is connected through a limiting resistor 26 to the resonator 4 and to ground, so that the lower surface 9 of the resonator serves as a holding anode to maintain the cathode spot after the discharge current through the orifice is extinguished. Alternatively, a conventional holding anode may be employed. Each time the arc is quenched a train of oscillations is established in the output circuit, the rate of damping depending principally upon the load coupled to the resonator. The repetition rate of the oscillation trains is determined by the circuit constants chosen for the charging circuit.