| Popis: |
Langevin’s work in ultrasonics, which resulted in about twenty publications and patents, will be reviewed. At the beginning of WWI, encouraged by Marie Curie, he started work on a directional ultrasonic system to detect submarines and for underwater communications, based on Chilowski’s proposal. Rejecting whistles, sirens and magnetic sources, he used a large mica ‘singing’ condenser for transmission, and proposed a large area carbon granule microphone as receiver. Noise problems with carbon receivers led Langevin, in early 1917, to test a single large slice of quartz, cut perpendicularly to one of its three electrical axes. This orientation differed from that used by Jacques and Pierre Curie’s quartz pi ezo- électrique, in which the stress and electrical axes are perpendicular. Later that year he demonstrated quartz as a transmitter, creating the enabling technology for later ultrasonic developments. The knowledge was freely disseminated to other Allied laboratories. After the war, Langevin gave the first ever course on theoretical and practical ultrasonics. He facilitated the technological transfer of pulse-echo technology from military to civil sectors and the establishment of a laboratory in Toulon for the certification of ultrasonic transducers. His co-workers went on to study magneto-strictive and high-frequency quartz transducers, therapeutic applications, and finite-amplitude propagation. |
