Honor A n inexpensive acoustic wave transducer developed by NIST mechanical engineers has been selected as one of the top 100 technologies for the year 2000 by Research and Development Magazine . The device, known as the lensless line-focus broadband transducer, helps acoustic microscopes perform ultrasonic examinations of alloys, ceramics, crystals, composites and other industrially important materials simply, cheaply and with easier interpretation of the data. The transducer sends a pulsed sound wave through a test sample that is submerged in water. Current acoustic microscopes use lenses to focus the ultrasonic beam and may cost hundreds of thousands of dollars. The cost savings result from NIST's use of an inexpensive piezoelectric, plastic film for the curved transducer.
Electrical signals cause the film to emit relatively low-frequency, pulsed sound waves.
The curvature of the film focuses the sound waves in the same way that curved mirrors are used in telescopes to focus light from distant stars. The transducer is positioned above the sample and then scanned or rotated through different angles to get a full picture of the material's elastic properties. Although image plates have been used for higher energy applications such as X-ray crystallography, no one previously had evaluated them for far UV spectroscopy. When an image plate is exposed to energetic radiation, electron-hole traps are created in the phosphor that can persist for very long periods of time, even weeks. When illuminated with a red laser, the traps decay by fluorescing in the blue.