BUBBLE CHAMBER

radiation detector that uses as the detecting medium a superheated liquid that boils into tiny bubbles of vapour around the ions produced along the tracks of subatomic particles. The bubble chamber was developed in 1952 by the American physicist Donald A. Glaser. The device uses a pressure-tight vessel containing liquid (often liquid hydrogen or deuterium) that is heated far above its boiling point and maintained under high pressure so that boiling is prevented. When the pressure on the liquid is suddenly reduced by an expansion device, the liquid becomes highly superheated, with the result that charged particles speeding through it create strings of tiny bubbles along their paths. By taking high-speed photographs of these bubble tracks through the strong glass windows of the chamber, it is possible to make precision measurements of the details of nuclear processes caused by the high-speed particles. Because of the relatively high density of the bubble-chamber liquid (as opposed to vapour-filled cloud chambers) collisions producing rare nuclear events are frequent and are observable in fine detail. New events can be recorded every few seconds when the chamber is exposed to bursts of high-speed particles from particle accelerators (or to showers of cosmic ray particles). The bubble chamber has proved very useful in the study of high-energy nuclear physics and subatomic particles.