Cyclotron

For other uses, see Cyclotron (disambiguation).

Lawrence's 60-inch (152 cm) cyclotron, c. 1939, showing the beam of accelerated ions (likely protons or deuterons) exiting the machine and ionizing the surrounding air causing a blue glow

A cyclotron is a type of particle accelerator invented by Ernest Lawrence in 1929–1930 at the University of California, Berkeley,[1][2] and patented in 1932.[3][4] A cyclotron accelerates charged particles outwards from the center of a flat cylindrical vacuum chamber along a spiral path.[5][6] The particles are held to a spiral trajectory by a static magnetic field and accelerated by a rapidly varying electric field. Lawrence was awarded the 1939 Nobel Prize in Physics for this invention.[6][7]

The cyclotron was the first "cyclical" accelerator.[8] The primary accelerators before the development of the cyclotron were electrostatic accelerators, such as the Cockcroft–Walton generator and the Van de Graaff generator. In these accelerators, particles would cross an accelerating electric field only once. Thus, the energy gained by the particles was limited by the maximum electrical potential that could be achieved across the accelerating region. This potential was in turn limited by electrostatic breakdown to a few million volts. In a cyclotron, by contrast, the particles encounter the accelerating region many times by following a spiral path, so the output energy can be many times the energy gained in a single accelerating step.[4]

Cyclotrons were the most powerful particle accelerator technology until the 1950s, when they were surpassed by the synchrotron.[9] Nonetheless, they are still widely used to produce particle beams for nuclear medicine and basic research. As of 2020, close to 1,500 cyclotrons were in use worldwide for the production of radionuclides for nuclear medicine.[10] In addition, cyclotrons can be used for particle therapy, where particle beams are directly applied to patients.[10]

  1. ^ "Ernest Lawrence's Cyclotron". www2.lbl.gov. Retrieved 2018-04-06.
  2. ^ "Ernest Lawrence – Biographical". nobelprize.org. Retrieved 2018-04-06.
  3. ^ U.S. patent 1,948,384 Lawrence, Ernest O. Method and apparatus for the acceleration of ions, filed: January 26, 1932, granted: February 20, 1934
  4. ^ a b Lawrence, Earnest O.; Livingston, M. Stanley (April 1, 1932). "The Production of High Speed Light Ions Without the Use of High Voltages". Physical Review. 40 (1). American Physical Society: 19–35. Bibcode:1932PhRv...40...19L. doi:10.1103/PhysRev.40.19.
  5. ^ Nave, C. R. (2012). "Cyclotron". Dept. of Physics and Astronomy, Georgia State University. Retrieved October 26, 2014.
  6. ^ a b Close, F. E.; Close, Frank; Marten, Michael; et al. (2004). The Particle Odyssey: A Journey to the Heart of Matter. Oxford University Press. pp. 84–87. Bibcode:2002pojh.book.....C. ISBN 978-0-19-860943-8.
  7. ^ "Ernest Lawrence – Facts". nobelprize.org. Retrieved 2018-04-06.
  8. ^ Cite error: The named reference Serway was invoked but never defined (see the help page).
  9. ^ Bryant, P.J. (September 1992). "A Brief History and Review of Accelerators" (PDF). Proceedings, Vol. 2. CAS-CERN Accelerator School: 5th general accelerator physics course. Jyvaskyla, Finland: CERN. p. 12.
  10. ^ a b "MEDraysintell identifies close to 1,500 medical cyclotrons worldwide". ITN Imaging Technology News. March 10, 2020.