bubble chamber

A device for detecting the paths of sub-atomic particles, devised in 1952 by Donald Glaser. The chamber contains a liquid prevented from boiling by pressure. The pressure is briefly released. Before general boiling can take place, the passage of a particle produces a local instability which initiates boiling, forming visible bubbles of gas along its path. The phenomenon is very brief and is operated cyclically. The track patterns are photographed for later analysis. In the 1970s the large Gargamelle bubble chamber at CERN, Geneva, containing 18 tonnes of liquid Freon, saw important discoveries in weak nuclear interactions.

A bubble chamber is a vessel filled with a superheated transparent liquid used to detect electrically charged particles moving through it. The charged particle deposits sufficient energy in the liquid that it begins to boil along its path, forming a string of bubbles. As the particles enter the chamber, a piston suddenly decreases the pressure in the chamber. This brings the liquid to a superheated state, in which a tiny effect, such as the passing of a charged particle near an atom, is sufficient to nucleate a bubble of vaporized liquid. The magnetic field causes charged particles to travel in helical paths whose radius is determined by the ratio of charge to mass of the particle.

Bubble chambers have largely been replaced by wire chambers, which allow particle energies to be measured at the same time.

Recent uses of bubble chambers: searches for dark matter (WIMPs): COUPP web site