The inaugural lecture presented in this paper (originally presented on 20 October 1988 at the University of Southampton) is a brief history of cryogenics. It considers not only the discoveries and technological advances made from 1877 to the present day, but also the factors which prompted and promoted them. The importance of interaction between research, training and industry is noted and some potential moves for the future are mentioned.
Pulse-tube refrigerators are attractive as long life and highly reliable coolers because of their mechanical simplisity. The early type of the device, which was first developed by Gifford and Longsworth in the early 1960's, is known as the “basic pulse-tube”. In the 1980's, the “orifice pulse-tube”, which originated from Mikulin's work, was shown by Radebaugh et al. to possess high cooling capability. This was the start of the boom of pulse-tube refrigerator research and development and many laboratories around world are now studying these devices. This paper briefly reviews the developments of several types of the pulse tube refrigerators, and an explanation of the cooling mechanism in terms of the thermoacoustic effect is presented. According to the thermoacoustical consideration, tremendous differences in refrigeration power between the basic and orifice types can be understood as follows; flow impedance of an orifice enhances the progressive-wave part of the working gas oscillations which causes large increases in heat transfer through a regenerator. Finally, some experimental data from the author's laboratory are shown and a qualitative interpretation by analogy with an AC circuit is described.
Fiber reinforced plastics (FRP) have been used in cryogenic application because of their good mechanical and thermal properties. In this paper, FRPs used at cryogenic environment are surveyed especially their reinforcements, matrices and molding methods are mentioned. The basic cryogenic properties of various FRPs are summarized and the development of high-performance FRP are discussed.
In order to improve the high field performance of superconducting magnets, the upper critical field Bc2 for practical multifilamentary alloy wires of NbTi, NbTiTa and NbTiHf were examined in respect with the usage of a pressurized superfluid cooling technique. The addition of Ta or Hf to NbTi enhanced by 0.5T for Bc2 at 1.8K. Although the addition of a heavy element such as Ta or Hf has been regarded as suppressing Pauli-paramagnetism so far, it was found that the mechanism for Bc2 enhancement by Hf addition is different from that by Ta addition.
Belyakov et al. reported in 1987 that they observed no Kapitza resistance when heat flowed from Superfluid helium (He II) to solid (copper). To verify this, we made an experimental apparatus similar to that used by them, which was composed of a cylindrical copper block, two small cells attached to the both ends of the copper block, heaters housed in the cells, and capillary tubes connecting the cells to the superfluid helium bath. Due to its symmetrical configuration, we could easily reverse the direction of heat flow, i.e. from/to He II to/from copper. The results of our measurements showed, however, that the Kapitza conductance was independent on the heat flow direction at the boundary. This fact reconfirms the common understanding on the reversibility of the Kapitza conductance.
A compact one-shot 3He cryostat has been fabricated for use of X-ray detector at a temperature of 0.4K. The cryostat employed two valves availably: one for controlling a charcoal adsorption pump, and the other for faciliating liquid helium handling. The use of two valves enabled us to decrease the amount of liquid helium including the transfer loss. Superconducting thin wires with a very low copper ratio were useful to generate a magnetic field of moderate strength, while suppressing the heat flow into the cryogenic region.