| 摘要 |
1,261,543. Resonant cavities. UNION CARBIDE CORP. 14 Jan., 1969 [30 Jan., 1968], No. 2111/69. Heading H1W. [Also in Division C7] An A.C. superconducting device, e.g. an RF cavity, is made by depositing a superconducting layer upon a highly finished substrate which is subsequently removed. The Figure depicts an intermediate step in the electrodeposition of highly pure niobium upon a substrate 1 to form a tubular RF cavity 2. The substrate may be made of copper, nickel, iron or iron alloy and is polished to obtain an extremely smooth finish, e.g. a roughness less than 5 Á inches RMS. The deposition is carried out using a fused-salt bath consisting of KF, NaF, LiF and K 2 NbF 7 , the proportions of the constituents, temperature, current density &c. being chosen to obtain a dense, fine grain deposit. After the deposition slip, a layer 3 of a porous, refractory material having good thermal conductivity, is deposited over the electroplated niobium, e.g. by plasma plating, electroplating, vapour deposition or a powder metallurgy process. This layer may consist of molybdenum, tantalum, niobium, tungsten, graphite, indium, platinum or a ceramic. |
