Cyclotron

A cyclotron is a type of particle accelerator invented by Ernest O. Lawrence in 1934 in which charged particles accelerate outwards from the centre along a spiral path. The particles are held to a spiral trajectory by a static magnetic field and accelerated by a rapidly varying (radio frequency) electric field. Lawrence was awarded the 1939 Nobel prize in physics for this invention. Cyclotrons were the most powerful particle accelerator technology until the 1950s when they were superseded by the synchrotron, and are still used to produce particle beams in physics and nuclear medicine. The largest single-magnet cyclotron was the 4.67 m (184 in) synchrocyclotron built between 1940 and 1946 by Lawrence at the University of California at Berkeley, which could accelerate protons to 730 MeV. The largest cyclotron is the 17.1 m (56 ft) multimagnet TRIUMF accelerator at the University of British Columbia in Vancouver, British Columbia which can produce 500 MeV protons.

There are over 1200 cyclotrons used in nuclear medicine worldwide for the production of radionuclides.

The cyclotron was conceived in Germany in the 1920s. At Aachen University in 1926, the cyclotron was proposed by a co-student of Rolf Widerøe, who rejected the idea as too complicated to construct. In 1927, Max Steenbeck developed the concept of the cyclotron at Siemens, but a misunderstanding prevented him from publishing and building the apparatus. The first cyclotron patent was filed by Hungarian physicist Leo Szilard in 1929, while working at Humboldt University of Berlin. The cyclotron was finally developed and patented by Ernest Lawrence of the University of California, Berkeley, where it was first operated in 1932. Lawrence went on to actually make a working cyclotron using large electromagnets from Poulsen arc radio transmitters provided by the Federal Telegraph Company. A graduate student, M. Stanley Livingston, did much of the work of translating the idea into working hardware. Lawrence read an article about the concept of a drift tube linac by Rolf Widerøe, who had also been working along similar lines with the betatron concept. At the Radiation Laboratory of the University of California at Berkeley Lawrence constructed a series of cyclotrons which were the most powerful accelerators in the world at the time; a 69 cm (27 in) 4.8 MeV machine (1932), a 94 cm (37 in) 8 MeV machine (1937), and a 152 cm (60 in) 16 MeV machine (1939). He also developed a 467 cm (184 in) synchrocyclotron (1945).

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