Site: Daikin Industries, Ltd.
3 Miyukigaoka, Tsukuba-shi
Ibaraki 305, Japan
Tel: 81-298-58-5036; Fax: 5082; E-mail: ko@mec.daikin.co.jp
Date Visited: January 28, 1997
WTEC Attendees: M. Nisenoff (report author), M. Beasley, G. Gamota, H. Morishita, F. Patten, R. Ralston, J. Rowell
Hosts: Dr. Yoon-Myung Kang (Rin-mei Ko), Section Chief Researcher, MEC Laboratory
K. Akaishi, General Manager
T. Shimadzu, Senior Research Manager (Planning)
Y. Hiratsuka
T. Kido
K. Murayama
K. Miura
    Mechanical Engineering Laboratory
    Sakai Plant
    1304  Kanaokacho, Sakai
    Osaka 591, Japan
    Tel:  81-722-87-8517; Fax:  52-6255

BACKGROUND

Daikin Industries, Inc., is the leading manufacturer in Japan of commercial and industrial air conditioning systems and of residential air conditioning equipment. The company was founded in 1924 and bases its products on mechanical engineering, electrical engineering, and chemistry. The gross income of the company in 1995 was about ¥400 billion (($3 billion) with a net profit of about ¥3 billion (~$25 million).1

The Research Center of Daikin Industries, Ltd. is located on a very attractive site in the Tsukuba Science Center about one hour by bus from Tokyo. It was built in the early 1990s and has excellent facilities -- large, well-equipped laboratories, wide hallways, and an impressive three-story atrium with original oil paintings hanging on the walls. The facility is now only partially occupied, as the level of research within Daikin has diminished over the past few years due to the overall economic conditions in Japan.

The Daikin manufacturing facilities for cryogenic refrigeration systems ("cryocoolers") are in Osaka, while its research and system applications work is done in Tsukuba. Its current product line in cryocoolers is primarily for cryogenic vacuum pumps and cryocoolers for magnetic resonance systems and other superconducting magnet systems such as Maglev. Recently, Daikin has begun research in small cryocoolers for SQUID magnetometers for biological applications. It has several joint ventures with foreign companies such as APD Cryogenic, Inc. (Allentown, PA, USA) in the development of compressors for cryogenic systems.

R&D ACTIVITIES

Daikin was a member of the Superconducting Sensor Laboratory (SSL) project, which completed its six-year program in 1996. The Daikin researchers who were assigned to SSL returned either to their parent organizations or to new employment. Daikin researchers transferred the niobium-based thin film SQUID technology from Electrotechnical Laboratory to their Research Center in Tsukuba and have fabricated SQUID sensors and electronics and integrated them with small cryocoolers. To reduce electromagnetic noise, the expander and the valve motor that is used to switch between the high pressure and low pressure gas are separated from each other as far as possible. Care is also taken to minimize any ferromagnetic material used in fabricating the cryocooler. The white noise of the typical SQUID system is between 10 and 20 femtotesla per root hertz with a noise peak at the drive frequency of 2 Hz of about 1 pT rms. The noise at the drive frequency and harmonics is caused by eddy currents induced by the reciprocating displacer. The periodic noise can be processed using a "noise template" and subtracting this "noise template" from the detected signal yielding more than 90% rejection. (Good MCG and MEG spectra can be obtained for these cryocooled SQUID systems.)

One cryocooled SQUID system is a single-channel horizontally oriented one in which the pick-up coils are within 2.5 mm of room temperature. The second is a 32-channel system with the sensor packages packaged in a 6 x 6 array with all of the pickup loops in a plane. This system was intended for use in magnetocardiography studies and to study the "inverse problem." The system is still under test, and Daikin is looking for potential clinical applications and commercial customers. The third SQUID system is a 61-channel system (oriented on a curved surface and mounted in a Dewar system with a concave tip) that was built for noninvasive studies of the brain and blood vessels. This appears to be an excellent example of the philosophy behind the establishment of the Superconducting Sensor Laboratory, in which this joint operation was to develop a viable SQUID magnetic sensor technology in Japan and, at the end of its lifetime, the researchers would return to their parent companies and begin to explore the commercial viability of this technology.

The Daikin cryogenics activity involves systems working near 80 K as well as near 4 K. One of its products is a 4 K machine, which consists of two Gifford-McMahon (GM) stages and two Joule-Thomson (JT) stages in series and provides 1-2 watts of cooling for about 5.1 kW input power. This cryocooler was reported to have 20,000-hour maintenance-free operation. It was intended for use with magnetic resonance imaging (MRI) equipment and for superconducting electronics devices, such as an SIS mixer for radioastronomy.

Daikin's 80 K cryocoolers are primarily Stirling cycle machines that employ linear drive motors and free expansion pistons. They range in cooling capacity from fractional watt (as small as 0.25 watts) up to about 5 watts. The testing of the 5 watt machine was in progress at the time of the panel's visit, and there were no reliability data yet available. This size of cryogenic refrigerators is commonly used by U.S. vendors who are developing HTS wireless base stations. The WTEC team's hosts at Daikin indicated that they have had conversations with several organizations about the possibility of joint ventures to provide cryocoolers for this application, but no agreements had as yet materialized.

There was also some indication that Daikin was exploring other potential applications of superconducting devices such as SQUIDs for nondestructive evaluation (NDE) and the possibility of developing HTS SQUIDs. Daikin researchers are making HTS films at Tsukuba and are considering beginning to make HTS SQUIDs. They have also examined the possible use of cryocoolers for cold CMOS and, as mentioned above, for HTS wireless filters, but thus far, the only work has been on magnetic systems for clinical applications.

In addition to the small Stirling machines, Daikin is also developing small pulse tube cryocoolers with about 0.5 W of cooling capacity at 70 K. These cryocoolers were still under development at the time of the team's visit, and performance and reliability data were not yet available. The usual advantage of pulse tube is supposed to be simplicity and low noise (due to no moving parts in the expander region), but results obtained at SSL did show some unexpected (magnetic or electrical) noise where the SQUID sensor was to be located.

For the various applications proposed for superconductivity, Daikin researchers believe that each has a unique requirement, such as low emitted (electric and magnetic) noise for SQUIDs, reliability for microwave applications, and cost for MRI. In the case of infrared camera applications, the driving requirement appears to be size. Daikin managers appear to be aggressively examining a large variety of applications for cryocoolers and were very interested in hearing how they might enter the superconducting wireless field and how they might enter the U.S. commercial market as a supplier of reliable cryogenic refrigeration systems.

CONCLUSIONS

Daikin Industries, Ltd., has a very strong, well balanced program in cryogenic refrigeration and in integration of these cryogenic refrigerators with superconducting devices, in particular with single- or multiple-channel SQUID magnetic systems. It has 14 years' experience in cryocoolers, starting with larger capacity machines for cryopumps and for cooling LTS magnet systems under the license of APD. As a member of the Superconducting Sensor Laboratory, Daikin learned about SQUID technology and its clinical applications and has been very successful in transferring SQUID technology to its own MEC Laboratory. Combining these two technologies the researchers have built complete SQUID systems combining 4 K cryocoolers and SQUID technology very successfully.

The cryogenics team at the MEC Laboratory in Tsukuba appears to be very well balanced and highly motivated and have achieved success in design and fabrication of small cryocoolers and the integration of these coolers with in-house built SQUID systems. It would appear that the necessary resources and talent are available to penetrate the small cryocooler market in Japan and worldwide. The introduction of the integrated SQUID system into the medical community and the eventual commercialization of this type of system will require new talents, such as rapport with the medical community and the ability to deal with routine maintenance and service calls for a clinical system.

REFERENCES

Daikin. n.d. Profile of Daikin: MEC and Systems (brochure).

Fukui, N., K. Sata, S. Fujimoto and Y.M. Kang. 1996. A Cryocooled SQUID system with minimal clearance between the pick-up coil and the specimen. In Proceedings of Biomag 96.

Sata, K., N. Fukui, E. Haraguchi, T. Kido, K. Nishiguchi, and Y. M. Kang. 1996. A 32-Channel MCG system cooled by a GM-JT cryocooler. In Proceedings of Biomag 96.

Sata, K., S. Fujimoto, N. Fukui, E. Haraguchi, T. Kido, K. Nishiguchi and Y. M. Kang. 1996. Development of a 61-channel MEG system cooled by a GM-JT cryocooler. In Proceedings of Biomag 96.

Utaka, Y., T. Kido and K. Kudo. 1996. Plastic-molded LTS DC-SQUIDs for multichannel biomagnetic measurement systems. In Proceedings of ASC 96.


1The exchange rate in 1995 was under ¥100/$.
Published: August 1998; WTEC Hyper-Librarian