Cloud chamber
A cloud chamber is a device which was used in the early twentieth century to detect sub-atomic particles.
It’s a sealed container, with a mist made of very cold water (or sometimes alcohol vapour) inside. The mist is like a cloud; that’s where the cloud chamber gets its name.
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When a particle travels through the mist inside the chamber, it leaves a track through the mist behind it, similar to the condensation trail left behind by a high-flying aircraft. |
Force fields affect the particles
The cloud chamber also has powerful electric and magnetic fields inside it, and these force fields affect the path that each sub-atomic particle takes through the chamber.
| Each type of particle makes its own distinctive track. The particles themselves are too small to see, but by studying the tracks they leave, we can tell which types of particle have passed through the cloud chamber, and how they interacted with each other. |  |
Anderson’s famous cloud chamber
Carl Anderson with his cloud chamber in 1937
Cloud chambers aren’t used much nowadays. Instead, we more often use a bubble chamber to detect sub-atomic particles, but Carl Anderson was using a cloud chamber when he saw and recognised antimatter for the very first time.
