William Coolidge

Born on 23 October 1873 in Hudson, Massachusetts, William Coolidge was a physical chemist and engineer whose innovative research on tungsten filaments and x-ray tubes revolutionized the lighting and medical imaging industries. Coolidge earned his electrical engineering degree from MIT in 1896 and his PhD in physics from the University of Leipzig in 1899. After returning to teach at MIT for five years, Coolidge was offered a research position at General Electric, where he would remain for the rest of his career. His first project was to improve the company’s Edison carbon-filament lamp, and over the next six years, he experimented with tungsten as a more energy-efficient, longer-lasting replacement material. His method of creating a ductile wire by doping tungsten oxide and forging the resulting metal powder transformed the lamp industry, and Coolidge’s ductile tungsten became the preferred filament in incandescent light bulbs. In 1913 Coolidge continued his experiments with tungsten to find a way to improve Crookes x-ray tubes, which were used in medical applications but were notoriously erratic. He found that he could make the tube more stable and controllable by replacing the cold aluminum cathode with a hot tungsten filament and outgassing the tube to create a vacuum. The Coolidge x-ray tube paved the way for modern x-ray machines used in medicine and dentistry. Over his career Coolidge proved himself to be a prolific inventor, receiving some 83 patents, as well as numerous awards and honorary degrees. In 1932 he was appointed director of GE; after retiring in 1944, he continued to serve as director emeritus and consultant. Coolidge died in 1975 at age 101. (Photo credit: AIP Emilio Segrè Visual Archives)

Date in History: 23 October 1873