cloud chamber

cloud chamber

noun

Definition of CLOUD CHAMBER

: a vessel containing air saturated with water vapor whose sudden expansion reveals the passage of an ionizing particle by a trail of visible droplets

First Known Use of CLOUD CHAMBER

1897

cloud chamber

noun    (Concise Encyclopedia)

Radiation detector developed by C.T.R. Wilson. Its detecting medium is a supersaturated vapour (see saturation) that condenses around ions produced by the passage of energetic charged particles, such as alpha particles, beta particles, or protons. In a Wilson cloud chamber, supersaturation is caused by the cooling induced by a sudden expansion of the saturated vapour by the motion of a piston or an elastic membrane. In a diffusion chamber, the saturated vapour is cooled to supersaturation as it diffuses into a region kept cold by a coolant such as solid carbon dioxide or liquid helium.