Cloud Chamber

[Can detect: Alpha, Beta and Gamma]

Figure above shows a simple form of cloud chamber, a device which enables the tracks of charged particles to be seen.
The felt ring round the top of the chamber is soaked in alcohol. The bottom of the chamber is cooled by ‘dry ice’ (solid carbon dioxide) to around -80 °C.
As the alcohol vapour spreads downward through the chamber, it is cooled beyond the point at which it would normally condense.

Alpha-particle tracks:	Beta-particle tracks:	Gamma-ray:

Thick and straight, with the occasional deflection if an alpha particle collides with an air molecule.	Thin and crooked. The particles cause much less ionization and, being light, are continually being pushed off; caused by air molecules nearby.	Don’t produce tracks as such. The tracks seen are those caused by electrons which have absorbed energy from photons and have escaped from atoms.