GB703995A - Improvements in and relating to high frequency resonators - Google Patents

Abstract

703,995. Magnetic - induction accelerators. METROPOLITAN - VICKERS ELECTRICAL CO., Ltd. Nov. 17, 1950 [Nov. 29, 1949], No. 28188/50. Class 39(1) [Also in Group XL(b)] In a synchro-betatron of the type described in Specification 622,148, the resonator forms a section of the annular envelope enclosing the orbital path of the charged particles, and comprises a tubular section 30 of dielectric material of. approximately elliptical cross-section which may be attached to the envelope by means of rubber gaskets. The section 30 is coated internally and externally with a layer 30<SP>1</SP> of conductive material such as silver, and operates as a quarter-wave closed concentric line resonator at a particular excitation frequency. In order to reduce eddy currents and to suppress undesirable modes of oscillation, portions 31 of the coating are removed from the exterior surface to form a plurality of longitudinal conductive strips 32, the portions 31 being discontinuous near one end of section 30 to provide a peripheral conductive strip 33. In a like manner, portions 34 are removed from the inner coating to form a plurality of,longitudinal conductive strips 35, portions 34 being discontinuous to provide peripheral conductive strips 36 and 37. A peripheral gap 38 is provided by removing a portion between strips 36 and 37. The cyclically varying electric accelerating field is produced across this gap when the resonator is excited at the appropriate frequency. Portions 39 are removed from the end surfaces to provide a plurality of conductive strips 40 connecting the external and internal longitudinal strips 32 and 35. Sufficiently tight coupling to suppress undesirable modes may be obtained by utilizing only peripheral strips 33 and 36. In such event, these strips may be located at any convenient position along section 30, as long as they are approximately, opposite each other to ensure cancellation of eddy currents. The conductive layer 30<SP>1</SP> may be formed by applying a layer of silver paint to the section 30 and subsequently baking the layer to secure adherence. The thickness of the layer may then be increased by electroplating or by repeated painting and baking. The removal of the various portions from the layer may be effected by masking during the painting operation or, after baking and electroplating, by burning grooves with a tungsten disc which is rolled along the conductive surface carrying a heavy current through the contact area. In order to couple high frequency energy into the resonator, a coating portion 41 is removed to provide a longitudinally extending conductive strip 42 to which the inner conductor of a coaxial line is connected. The outer conductor of the line merges adjacent the resonator into a channel-shaped enlargement which is connected to the coating 30<SP>1</SP> and covers the removed portion 41 to afford high frequency shielding. The length of strip 42 may be varied to produce optimum tuning and matching of the system and the strip may be made entirely separate from the remainder of the coating by extending portion 41 to surround the strip. Auxiliary tuning and trimming may be accomplished by moving a metallic or metallized strip 48, Fig. 6, along a conductive strip 47 provided by removing a portion 46 of the coating. The strip 48 may be retained in position by adhesive material. Instead of using a conductive coating, the resonator may be formed by securing strips of conductive material to the surface of section 30 by means of an alkyd resin prepared by reacting. a polybasic acid and a polyhydric alcohol, such as phthalic anhydride and gylcerol. Conductive strips may be placed around the entire inner periphery of section 30. Specifications 585,992 and 654,373 also are referred to.