Bubble chamber in action

A Sagitta bubble chamber detecting alpha and beta particles. Inside the chamber there is a thorium-doped welding rod (made of iron), which emits alpha particles (Helium nuclei). The bubble chamber is filled with vapor of isopropanol alcohol. The vapor condenses on the bottom of the chamber, which is kept at a low temperature. Minute "rain drops" of isopropanol are constantly seen. Alpha particles leave thick tracks, while beta particles (electrons) leave long narrow tracks. Scattering events are occasionally seen also.