GB1222624A - Josephson junctions - Google Patents

Abstract

1,222,624. Superconductor devices. MULLARD Ltd. 30 May, 1969 [11 April, 1968; 21 Jan., 1969], No. 40737/69. Divided out of 1,196,788. Addition to 1,196,788. Heading HlK. . The invention of the main Specification 1,196,788, which comprises an array of Josephson junctions constituted by a plurality of balls each separated from a superconductive part by a thin non-superconductive barrier, is modified by replacing the balls with members having one dimension very small compared with another dimension. A plate having conical or cylindrical projections on one face is placed with the projections in contact with a further plate, Fig. 1 (not shown). The projections or contacting plate may be self-oxidizable. The projections may be produced by machining, etching, or casting, or may be individually produced and soldered into holes in a plate. The projections may comprise parallel ridges produced by milling or etching grooves, Fig. 2 (not shown), and two such plates may be placed with their ridges contacting at right angles. The ridges may also be produced by securing a plurality of wires to a plate with solder or aluminium-loaded resin, Fig. 3 (not shown). The wires may be of circular or triangular cross-section. The plate contacted by the projections may have corresponding depressions and may be formed by pressing the projections into the surface of liquid mercury which is then frozen. The arrays may be operated as generators or detectors as described in the main patent. A stub aerial may comprise a large number of parallel oxide-coated wires (e.g. of Nb) embedded in solder with their ends projecting. The wires may be produced by forming projections integrally with a plate and casting solder, mercury, or lead between them, Fig. 5 (not shown). A three-dimensional array of Al or Nb wires or tubes may be assembled, Fig. 6 (not shown), and the materials may be varied within the array to broaden the bandwidth. A plurality of circular areas of superconductor material may be deposited on a quartz substrate with the edges of the areas just overlapping, Fig. 7 (not shown). Although no insulator is present between the areas it is stated that the overlapping portions form weak Josephson junctions the efficiency of which is improved by the parallel connection of further weak junctions. Alternatively a thin film having closely spaced circular apertures may be deposited on a substrate, the narrow necks of film between the apertures forming an array of weak Josephson junctions, Fig. 8 (not shown). Such a film may be deposited using an array of balls as a mask, the balls being mechanically oscillated to produce the desired pattern. A plurality of substrates may be stacked to form a three-dimensional array.