Seventy years of particle accelerators

12 June 2002

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Seventy years ago, on 17 June 1932, the Royal Society received a paper* describing the observation of the first nuclear transmutations produced by artificially accelerated particles. John Cockcroft and Ernest Walton at the  Cavendish Laboratory in Cambridge had built  a machine that accelerated protons through voltages of  up to about 700 kilo volts. When the protons (hydrogen nuclei)  interacted with a lithium target at the end of the machine, they produced helium nuclei - alpha particles. Cockcroft and Walton were rewarded with the Nobel prize in 1951. Accelerators that work on the same principle are in operation today at many laboratories around the world, often as the first stages for higher energy machines. This image shows the Cockcroft Walton voltage multiplier that supplies 665 kV to accelerate negative hydrogen ions at the ISIS facility at the Rutherford Appleton Laboratory in the UK. In the image, an earthing stick is being applied to the high voltage terminal of the voltage multiplier stack.

(The ISIS Cockcroft-Walton preinjector is scheduled to be replaced by an RFQ accelerator in 2003.)
(*see Proc Roy Soc vol A137, p 229, 1932)

Credit: CLRC / David Findley
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