GB1379894A - Tuning arrangements for resonant cavities - Google Patents

Abstract

1379894 Klystrons EMI-VARIAN Ltd 17 Dec 1971 [17 Dec 1970 (2)] 60046/70 and 60047/70 Heading H1D A klystron cavity is tuned by the provision in the cavity, or in a cavity coupled thereto, of an electrical path which includes a plurality of series connected diodes, such that the path can be selectively rendered conductive or non- conductive. As shown, the resonant cavities 1, 2, 3, 4 of a klystron are each provided with an auxiliary resonant cavity 12, ..., 15, of similar shape and provided with dummy drift tubes, the auxiliary cavities being tuned by the provision in each of a plurality of paths, Fig. la (and Fig. 1b, not shown) connecting opposite faces of the cavities and formed by series connected PIN diodes, different paths being rendered conductive by the connection thereto of a biasing potential by, e.g., a solid state switch, to provide desired resonant frequencies. The main and auxiliary cavities are separated by windows 16 to 19, located at voltage nodes, and the number of diodes connected in a path is made greater for those paths located in regions of higher field strength i.e. towards the centre of a cavity or, comparing corresponding paths in different cavities, in the cavities towards the output end of the klystron (Fig. 1(b), not shown). In a further arrangement, Fig. 4, permitting fine tuning, the diodes are mounted in glass or ceramic tubes 59 the ends of which project through slots in the cavity walls and are mounted in the ends of the arms 64, 65 of U-shaped members 66, which are movable towards and away from the beam axis 54 by adjusting screws 68.