Georges Charpak

(b. 1924)

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(1924–) French physicist

Charpak, who was born in Dabrovica, Poland, was educated at the Ecole des Mines, Paris. He was imprisoned at Dachau from 1943 until 1945. He then worked in France on nuclear research, mainly at the Centre National de la Recherche Scientifique (CNRS). He moved in 1959 to CERN (Conseil Européen pour la Reserche Nucléaire; European Laboratory for Particle Physics), in Geneva, where he has since remained.

By the time Charpak arrived at CERN nuclear physicists had begun to search for ever-more-elusive particles. To detect their fleeting and rare appearances could require the examination of thousands of particle tracks. Yet the older particle detectors – bubble chamber, cloud chamber, etc. – could handle only a small proportion of the data pouring from the newer and more powerful accelerators.

In 1968 Charpak described his newly designed drift chamber in which charged wires are strung 1.2 mm apart, layer on layer, in a gas-filled container. A voltage is applied to the wires in such a way that the central wires are charged positively, and the outer ones negatively. If a charged particle enters the detector, it ionizes atoms of gas, and the ions drift to the central wires, triggering a signal. As the wires criss-cross through the chamber it is possible to reconstruct a three-dimensional picture of the ion's tracks from the signals obtained.

When linked to computers the drift chamber can handle a million nuclear events per second. It played a vital role in the 1983 discovery of the W and Z bosons by Carlo Rubbia. It also won for Charpak the 1992 Nobel Prize for physics.

In more recent times Charpak has turned his attention to biochemical reactions.

Subjects: Science and Mathematics.

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