ABSTRACT

This report reviews the status of electronic applications of superconducting materials in Japan, with particular focus on comparisons with relevant activities in the United States. It is complementary to a report published by WTEC in 1997 covering high power (e.g., electric utility) applications of superconducting materials. The particular focus of this study was on R&D activities related to radio frequency (rf) and microwave applications of passive devices. Both low temperature superconductivity (LTS) and high temperature superconductivity (HTS) materials are covered. Specific topics include HTS materials and thin films; rf and microwave applications; digital applications; superconducting quantum interference device (SQUID) applications; refrigeration and packaging; collaborative superconducting electronics projects in Japan; and Japan's International Superconductivity Technology Center (ISTEC). The report includes site reports for visits conducted by the panel members to leading research laboratories and systems developers in Japan. The panel's conclusions include the following: (1) Japan is leading in the science of thin films, in both LT and HTSQUID systems, in LTS digital memory, in development of commercial refrigerators, and in cryopackaging of SQUID systems; (2) the United States is ahead in all aspects of rf and microwave applications; (3) Japan is now more innovative than the United States in its development of SQUID systems; (4) the United States has advanced more rapidly than Japan in LTS circuit fabrication (U.S. fabrication capability is now comparable to that in Japan); (5) in the critical technology of refrigeration, the United States is judged to be leading in the development of miniature refrigerators, in the engineering of the Dewar package for rf and microwave systems, and in advanced concepts of refrigeration, however, refrigerator companies in Japan are well ahead of their U.S. counterparts in the development and sale of pulse-tube refrigerators, and many of the compressors used in U.S. commercial cryocoolers are manufactured in Japan; (6) the two countries are at parity in the areas of LTSQUID sensors, LTS digital processing, and LTS digital switching circuits. These and other conclusions are reviewed in detail in the panel's executive summary.
Published: August 1998; WTEC Hyper-Librarian