Kerst, Donald William (1911-1993), an American physicist, developed a device called the betatron in 1940. The betatron was one of the earliest particle accelerators (devices that speed up the movement of tiny bits of matter). Inside the betatron, an electromagnet forces electrons to circle in a vacuum chamber, steadily increasing speed. The electrons can be directed at a tungsten target to produce X rays. Kerst used the betatron to study the atomic nucleus and to explore methods of treating cancer with radiation. He built a more powerful betatron for the University of Illinois in 1950. Industry still uses betatrons to look for flaws in manufactured materials in a process called industrial radiography.