ASA 126th Meeting Denver 1993 October 4-8

2pEA2. Development of a magnetostrictive sonar transducer using high-temperature superconducting coils.

C. H. Joshi J. P. Voccio

American Superconductor Corp., Two Technology Dr., Westborough, MA 01581

J. F. Lindberg

[Naval Undersea Warfare Ctr. NUWC), New London, CT 06320], and

A. E. Clark

[Naval Surface Weapons Ctr. NSWC), Silver Spring, MD 20903]

A low-frequency, dual-piston sonar transducer has been designed, built, and tested. This transducer uses a terbium--dysprosium magnetostrictive rod in combination with high-temperature superconductive HTS) coils as the driver element. Terbium--dysprosium, when operated at cryogenic temperatures, has the highest known magnetostrictive constant. In this transducer, two HTS coils, driven by a combined dc and ac signal, excite the magnetostrictive element. The resultant motion is transmitted through the vacuum cryostat enclosing the driver assembly to two head masses, which transmit the sound to the surrounding environment. The combination of the high magnetostriction and the absence of electrical dissipation in the HTS coils results in very high overall system efficiency. Modeling of this type of transducer shows overall efficiencies of 80% or more can be obtained. The driver assembly is cooled by a compact Stirling Cycle cryocooler. Performance testing in air and water show self-resonance occurs at 520 and 430 Hz, respectively. The overall system design, as well as measurements of acoustic output and efficiency, will be presented. [This project was funded by The Naval Undersea Warfare Center, New London, CT, through the Small Business Innovative Research SBIR) Program.]