The International Practical Temperature Scale of 1968″ is briefly introduced with emphasis on its utility for low temperature thermometry. The chief difference between IPTS-68 and IPTS-48 which had been in use until replaced by the former is described with remarks which may help experimentalists to use the new Scale. Technical informations in the textbook of IPTS-68 are summarized in tables.
Recently, resistive-cryogenic dc cable system or superconducting dc cable system is actively investigated as the underground cable transmission at each country. It is a very interesting problem to compare the each cable system from viewpoints of techniques and economics. We have done the economical comparison of conventional dc cable system, the resistive-cryogenic dc cable system and superconducting dc cable system. We get the results from this comparison as below, 1) The Break-even power of superconducting cable system was great effected by the value of transmitting voltage, for example, in case of 220kV of transmitting voltage, breakeven power is about 5GW, in case of 880kV, it is about 2GW. 2) In case of the transmitting power is more than 2GW, the superconducting cable system is the most economical system than any other cable system. 3) The economical domain of resistive-cryogenic cable system is small.
The specimen-freezer microscope intended for cryogenic research has been developed to such an extent that its results are used for frozen foods. Specimens cooled with liquid nitrogen can be examined with visual clarity even at a temperature as low as -100°C. The process of ice formation can be observed throughout refrigeration, irrespectial of quick or slow cooling which affects frozen pattern figures of specimens. Hot and cold ends are provided inside the compartment which serves as a thermal bridge to keep the specimen in a half frozen state, both solid and liquid co-existing in the same viewfield.
Copper is an important component to produce a stable and protected superconducting magnet. The electrical properties of commercially available copper under magnetic field and mechanical force are discussed. The resistivity of OFHC copper under magnetic field more than 10kG increases steadily with a gradient of about 4.5×10-10Ω-cm/kG. The gradient is independent of the amount of cold work. The resistivity ratio (ρ300°K/ρ4.2°K) of Electrolytic tough pitch copper is better than OFHC copper. The resistivity ratios of commercially available ETP copper are 150-350 and those of OFHC copper are 120-250.