Wilson, Charles Thomson Rees (1869–1959)

The cloud chamber devised by C T R Wilson was the first instrument to detect the tracks of atomic particles. It consisted originally of a cylindrical glass chamber fitted with a hollow piston, which was connected, via a valve, to a large evacuated flask. The piston falls rapidly when the valve is opened, reducing the pressure in the chamber, and water vapour condenses along the tracks of any particles in the chamber.

Scottish physicist who shared the Nobel Prize for Physics in 1927 for his invention in 1911 of the Wilson cloud chamber, an apparatus for studying subatomic particles.

Wilson was born near Edinburgh and studied at Manchester and Cambridge. He was professor at Cambridge 1925–34.

Wilson originally devised the cloud chamber to simulate clouds in his laboratory. From 1895 to 1899, he carried out many experiments and established that the nucleation of droplets can take place in the absence of dust particles. He also demonstrated that once the gas is supersaturated with water vapour, nucleation can occur and is greatly improved by exposure to X-rays. This showed that ions are the nucleation sites on which water droplets form in the absence of dust.

Wilson realized in 1910 that the cloud chamber could possibly show the track of a charged particle moving through it, and applying a magnetic field to the chamber would cause the track to curve, giving a measure of the charge and mass of the particle. The adapted Wilson cloud chamber immediately became vital to the study of radioactivity.

During 1900–10, Wilson studied electrical conduction in dust-free air by means of a gold-leaf electroscope he devised.