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Charpak, Georges

particle multiwire proportional detector

(1924– ) Polish–French physicist: inventor of multiwire and drift particle detectors.

Charpak was born in Poland and became a naturalized French citizen at the end of the Second World War. He studied as a mining engineer before taking a PhD in experimental nuclear physics at the Collège de France, and working at the CNRS. From 1959 he worked at CERN and in 1968 published his invention of the multiwire proportional counter, which later won him the Nobel Prize. A problem for particle physicists is that it is often only one interaction in a billion that is of interest, and selection from photos of events in bubble chambers and the like was too time-consuming. Charpak began instead with the Geiger Müller tube or proportional counter which uses a single wire at the centre of a cm diameter tube, with a strong electric field between the two. A particle causes an avalanche or cascade of ionization, registered as a click of current, an electronic response. Charpak produced a sheet-like multiwire proportional detector using fine wires about 2 mm apart, between two sheets of closely spaced wires at a strong negative potential. He then obtained a similar response from a cell of the detector when a particle passed, due to a localized cascade. The signals were amplified and fed directly into a computer, which registered and sifted the many particles, at high speed. This invention and its variants formed the basis for virtually all particle detection made since, and allowed discovery of the charm quark in 1974 (by and ) and the intermediate boson in 1983 (by and VAN DER MEER ).

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