Following an introductory review of the concept of macroscopic quantization, simple physical notions underlying the understanding of the properties of superconductors involving weak links is given. A brief treatment of the Josephson effect is given as an introduction to the application of macroscopic quantum coherence effects to scientific devices. Special emphasis is given to the description of devices involving double or single weak links for measurements of very small magnetic fields and voltages. Advantages and limitations of various methods is briefly described together with problems and possibilities involved in future application of the A. C. Josephson effect.
The superconducting power line is one of the new systems which will be developed to transmit the electric power for a long distance or in populated city. The first purpose of this method is not the leveling up of the electrical efficiency but the density of the transmission energy. There are yet problems to be solved in this line such as whether DC or AC system, the electrical insulation in low temperature, the position of the refrigeration station, the thermal contraction and the technique of protection. Of the many examples the auther introduces the designs of Gauster et al and Garwin et al, and the experimental result of the model which succeeded in BICC in the United Kingdom.
This article is a survey of the processes for making β-W type structure superconducting compound materials. These processes are classified as follows: (1) Diffusion process: V3Ga is easily formed by a improved diffusion technique at 700°C. Nb3Sn and V3Si are formed by the diffusion treatment around 950°C while the formation of Nb3Ga and Nb3Al requires much higher diffusion temperatures. (2) Chemical vapour deposition process: Nb3Sn, V3Si and Nb3Ga are deposited by the hydrogen reduction of mixed chloride gases of the constitutional elements. (3) Vacuum vapour deposition process: Nb3Sn is made by the simultaneous vapour deposition of Nb and Sn in high vacuum. Processing of high Tc compound Nb3(Al0.8Ge0.2) is also being studied. (4) Plasma spray process: Nb3Sn coil can be made directly by this process without wire windings. High field superconducting Nb3Sn tapes have already been made commercially by the process (1) and (2). V3Ga tape also seems to be promising for practical use.