It is estimated in Japan that the demand for electric energy will reach the amount of 3.8×1011kWh and 80% of the quantity will be produced from the fossil and nuclear fuel in 1975. Moreover, numer ous consumers of electricity will converge on a narrow district so-called Tokaido megalopolis in days. Many problems includig political and economical matter must be solved to provide for the above future situation. In the technological field, the following thema of research and development are proposed. (1) Utilization of heat rejected from the thermal electric power plants. (2) Reduction of waste matter from the thermal plants. (3) High efficiency, new energy conversion devices. (4) Large capacity under ground transmission line. (5) Offshore and undersea power station. (6) Measure to counter the peak power demand. (7) Revolutional power distribution system suitable for the over-crowded city.
This paper deals with the considerations and an experiment concerning the reliability of the cryogenic refrigerator. On the basis of extensive investigation it is pointed out that one of the most important factors which affect the reliability of a conventional cryogenic refrigerator is the expansion engine. After making a fundamental study on expansion engines, on was designed for reliability testing, with NTBF (Mean Time Between Failures) aimed at 8, 000 hours aud the non-maintenance period at 4, 000 hours. The trial expansion engine which incorporates an auto-valve was incorporated into a Compact-sized helium liquefying refrigerator for cooling a large-sized super-conducting magnet which generates a persistent magnetic field of 55kilo gauss. The refrigerator was operated for a total of 2, 500 hours including a 1, 000-hour continuous unattended operation, without trouble. Thus, the non-maintenance period was estimated at 5, 000 hours.
Supercondcting intermetallic compounds, Nb3Al and Nb3(Al-Ge) were prepared by three methods: diffusion after dipping, diffusion after vacuum deposition and co-deposition. It is found that the intermetalic compounds can be formed at temperarures between 800°C and 1, 000°C by the co-deposition method. Intermetalic compohnds formed were identified using X-ray diffraction analysis, observation of anodically oxidized specimens and meaurement of the superconducting transition temperature. The critical current densities, Jc were measured for Nb3(Al-Ge) specimens prepared by codeposition method with a result Jc-104A/cm2 at 30KG. Refering to the literatures on Nb3Al, Nb3(Al-Ge), Nb3Sn, V3Si and V3Ga inter relations between the method of synthesis, the formation temperature and the superconducting properties were examined to find the way to raise the critical current density of Nb3Al and Nb3(Al-Ge).