GB1034645A - Improvements in high frequency electrical oscillation generators - Google Patents

Abstract

1,034,645. Discharge apparatus. NATIONAL RESEARCH DEVELOPMENT CORPORATION. Jan. 28, 1964 [Feb. 8, 1963], No. 5279/63. Heading H1D. [Also in Division H3] A microwave generator employing a high intensity cold cathode arc discharge coupled both to a microwave power source and to means for extracting energy at a desired harmonic frequency-of the type disclosed in Specification 944,983-includes first and second arc electrodes of metal rod or wire, and means for operating the discharge in an inert gas at a pressure of between 1000 and 4000 lbs. per square inch. Three orthogonal bores in a brass block 10 provide, respectively, a rectangular input waveguide 11 connected through a quartz window to a klystron, a circular output waveguide 40 connected through a quartz window to a load, and mounting assemblies for a platinum cathode 22 mounted within a molybdenum sheath 23, and a platinum anode 28 mounted within a tuning plunger 31 and an insulating sleeve 36. The free ends of the two waveguides are sealed by tuning plungers, and electrodes 22 and 28 and sheath 23 and plunger 31 are all independently axially adjustable. A conduit, Fig. 1 (not shown), permits the introduction into the hermetically sealed structure of argon with 4% to 15% of hydrogen. Electrode 28 is capacitively coupled to block 10 by a mica sheet 35, and is also connected by a change-over switch to one terminal of either a D.C. or a 200-5000 c/s. A.C. current supply, the other terminal of which, together with the block 10 and cathode 22, is earthed. Preferably, the device is operated initially with D.C., such that platinum is transferred from the cathode to form a molten ball on the tip of the anode, which is allowed to grow until its size is such that it becomes resonant at a desired harmonic of the input frequency, whereafter the electrodes are switched to the A.C. supply to prevent further change of drop size. It is suggested that the arc is maintained predominantly by thermionically enhanced field emission caused by the dense plasma in the high pressure gas. The device can provide energy in excess of 1000 Gc/s.