spark chamber, in physics, device for recording the passage of elementary particles produced by reactions in a particle accelerator. Particles pass through a stack of metal plates or wire grids that are maintained with high voltage between alternate layers. A high-pressure gas fills the gaps between the plates and is ionized along the path of the traversing charged particle. As a result, sparks jump between adjacent, oppositely charged plates and the trail of sparks left by the particle is seen as a series of dashes. The spark chamber has replaced the bubble chamber in certain applications. Although the particle paths are recorded more accurately in the bubble chamber, the bubble chamber indiscriminately records all events that occur in a comparatively long interval. The spark chamber operates much more rapidly and can be made highly selective by using auxiliary detectors to screen out unwanted events. Because of its selectivity, the spark chamber is most useful in searching for very rare events. Spark chambers can be highly automated, with data collected and stored electronically instead of photographically, as is necessary with the bubble chamber. The analysis of the data can then be accomplished by a high-speed computer, which may operate simultaneously with the experiment and thereby provide immediate evaluation of the quality of the data and allow optimum operating conditions to be maintained at all times.