Due to time constraints and limited personnel, the WTEC panel was unable to fully assess the fields of refrigeration and cryopackaging as they relate to electronic applications of superconductivity in Japan. Given the importance of these fields, not only to electronics but also to power and other applications of superconductivity, it may be useful to conduct a separate study of refrigeration for all applications of superconductivity.

In terms of refrigeration for electronic applications of superconductivity, there is a much higher level of activity on pulse-tube refrigerators in Japanese industrial R&D laboratories than is the case in the United States. One company, Iwatani, is already selling a pulse-tube cooler, and Aisin Seiki intended to do so late in 1997. Japan would appear to be well positioned to supply pulse-tube coolers for both HTS applications and also to the cryopump market. Already, Japanese industry provides many of the compressors for civilian U.S. cooler manufacturers.

Despite Japan's potential for being very competitive not only in terms of technology but also in terms of cost in markets for cryocoolers, the cost of refrigerators presently manufactured and sold in Japan is significantly higher than that of similar machines made and sold in the United States.

Fig. 7.5. ATP program hybrid switch system (Conductus).

In terms of cryopackaging, Daikin has developed both MEG and MCG SQUID systems using cryocoolers rather than liquid cooling, as is common elsewhere. The WTEC panel did not see advanced system-level packages for wireless applications of the type already advertised by Conductus, ISC, SCT, and STI in the United States, which in 1997 were under test in base stations. The Japanese cellular provider DoCoMo was reported to be testing such prototype wireless systems on the roof of one of its buildings, but it is possible these systems were from U.S. companies. Also, the panel did not see hybrid LTS digital systems using cryocoolers, although such a system was demonstrated by Fujitsu at the end of the Josephson Computer Project, and one of the hybrid switch projects funded by FED mentions use of cryocoolers in the final system demonstration.

Published: July 1998; WTEC Hyper-Librarian