The absolute determination of the 2e/h done by B. N. Taylor et al based on the AC Josephson effect in terms of the emf standard of the National Bureau of Standards is introduced. The voltage intervals between sharp current steps which take place when a Josephson junction is irradiated by microwave power of appropriate frequency is so definitely related to the microwave frequency that the effect might offer a powerfull base of the atomic standard of the emf in the future. This circumstance is explained in conjunction with the present status of the electrical units and attempts on the atomic standards of electrical units.
General description are given on the recent trends of storage, transportation and coldness utilization of liquefied natural gas. Three different types of storage tanks……namely above ground tank, insulated below ground tank and frozen earth tank…are constructed. There are two alternative construction systems of cargotanks of LNG ocean tanker. One is self-supporting type and other is membrane type. We can find many reports on the research and reviews on the coldness utilization of LNG, and no apparent commercial instances of it.
A hydrogen bubble chamber with 200 liters of liquid, 78cm in diameter is under construction at Institute of Nuclear Study, University of Tokyo. A simple Linde refrigeration cycle is provided, as such a system meets the design considerations of this chamber. In order to establish the required capacity of the refrigerator, the static and dynamic heat loads were analyzed. Designing for a cycling rate of two expansions per second gives an estimated total heat load of 920 watt, including safety factors. A refrigerator with a capacity of 1, 000 watt at 26°K, therefore, was designed for this chamber, and brief descriptions of this refrigerator are given. For the precise control of the temperature of the chamber liquid, an elaborate temperature control loop configuration was considered, and the hydrogen temperature circuit schematic is shown.
One of the important factors which stabilize the copper claded superconducting wire is boiling heat transfer from superconducting wire to liquid helium. To improve the cooling effect of stabilized superconducting wire, the cooling effect of the channel (6.3mm wide, 12.83mm long) digged on the surface of copper was investigated. The channel oriented horizontally in liquid helium was effective in nucleate boiling heat transfer but it had little effect on maximum nucleate boiling heat flux qmax, minimum film boiling heat flux qmin and film boiling heat transfer even if it became 0.9mm deep. On the other hand, the channel oriented vertically was found effective in all over the region of cooling character curve. In every case, there were the relatively enormous hysteresis in nucleate boiling heat transfer.
Studies of the field energy removal from four superconducting magnets were done by a parallel resistor method. The rate of energy removal as a function of the resistance was not fully agree with the theoretical curve. The maximum rate of energy removal -90% in every coil. The values of the resistance at the high rate was few ohms and had not a functional relation with self-inductances of coils. The relation between the resistance and rate of energy removal depended on the growth of resistance appeared at quenching. After a resistive region had extended in the wide range of the superconducting magnet, it is too late to remove field energy.
A continuous level indicator of the liquid helium was constructed by using the superconducting Nb-25% Zr wire as a sensing element. The idea of this new device is based on the following facts: (1) There exists a difference of the cooling efficiency between the vapour and the liquid of helium. (2) It is able from this difference to propagate artificially a normal region only in the part of the wire above the liquid level. Thus, the measurement of the voltage across the total length of the wire gives a continuous detection of the liquid level. The main characteristics of this level indicator are summarized as follows: (1) This device is simple in construction and inexpensive. (2) The magnitude of the voltage is precisely proportional to the length of the Nb-25% Zr wire above the liquid level. (3) The response time for a variation of the level is very short.