France
Paul Langevin
1872–1946 Physicist; developer of ultrasonic submarine detection, 1915–1918
Born in Paris, Paul Langevin studied at ESPCI Paris and the École normale supérieure, worked under Joseph John Thomson at Cambridge and took his doctorate in 1902. In 1909 he was appointed to the chair of general and experimental physics at the Collège de France. In 1915 he began work on detecting submarines with ultrasound, taking up a proposal by the Russian engineer Constantin Chilowsky, and they filed a patent in 1916. Langevin later used quartz crystals to send and receive the sound pulses. According to an IEEE Milestone citation, the system could detect submerged submarines at ranges up to 1,300 meters, but the war ended before it became operational. Arrested in 1940 and later held under house arrest, he died in Paris in 1946.