C.T.R. Wilson - English Physicist
(1869-1959)
1911
Wilson invents the cloud chamber, which allows subatomic particles to be viewed for the first time.

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The Wilson Cloud Chamber is a particle detector in which the path of a fast charged particle is made visible by the formation of liquid droplets on the ions left by the particle as it passes through the gas in the chamber. The interior of a cloud chamber contains a mixture of a gas such as air, argon, or helium and a vapor such as water or alcohol. When such a mixture is made supersaturated in the vapor component by cooling of the gas (typically by expansion), the vapor tends to condense preferentially on charged ions in the gas. Since a fast moving charged particle produces many ions in its passage through the gas, condensation of the vapor leaves a trail of droplets to indicate the path of the particle. By placing the cloud chamber in a magnetic field and photographing the resulting trails, the mass, velocity and charge of the particle can be determined.

Cloud Chamber Compressed

Cloud Chamber Expanded

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