Lawrence earned his Ph.D. at Yale University in 1925. An assistant professor of physics at Yale (1927-28), he went to the University of California, Berkeley, as an associate professor and became full professor there in 1930. In 1939 he won the Nobel Prize for Physics for his invention of the cyclotron, the first particle accelerator to achieve high energies. He first conceived the idea for the cyclotron in 1929. One of his students, M. Stanley Livingston, undertook the project and succeeded in building a device that accelerated hydrogen ions (protons) to an energy of 13,000 electron volts (eV). Lawrence then set out to build a second cyclotron; when completed, it accelerated protons to 1,200,000 eV, enough energy to cause nuclear disintegration. One of Lawrence's cyclotrons produced technetium, the first element that does not occur in nature to be made artificially. With the cyclotron, he produced radioactive phosphorus and other isotopes for medical use, including radioactive iodine for the first therapeutic treatment of hyperthyroidism. In addition, he instituted the use of neutron beams in treating cancer.