Cyclotrons

One method for examining the nucleus of atoms is to bombard them with protons and alpha particles (two protons and two neutrons). However, electromagnetic forces repel these positive particles away from the nucleus. In order to create a collision, the bombarding particles need to have a very high speed.

Before 1930, scientists used radioactive materials as a source for alpha particles. They were relatively low energy and couldn't penetrate into the heavier nuclei.

In 1928, Ernest Lawrence came up with a plan to accelerate protons around a circle adding velocity with magnets placed around the "track." As the protons raced around the circle they would gain energy until they reached the outside diameter and shot out toward their target.

Lawrence won the Nobel prize for physics for his cyclotron in 1939. The basic idea is still used today in research and medicine, and was the basis for larger the design of larger and more powerful particle accelerators.       

Related Web Sites

Ernest O. Lawrence
Figures in Radiation History -- Michigan State University