a device for detecting ionizing radiation, consisting of two oppositely charged metal plates in a chamber containing inert gas, so that a particle passing through the chamber ionizes the gas and causes a spark to jump between the electrodes
spark chamber in American English
any of several devices for detecting charged subatomic particles, decay products, rays, etc., consisting usually of a large group of closely spaced, oppositely charged metal plates between which sparks will jump through an inert gas, as neon, along the ionized path created by the passage of radiation