Today, working spark chambers are mostly found in science museums and educational organisations, where they are used to demonstrate aspects of particle physics and astrophysics.
Spark chambers consist of a stack of metal plates placed in a sealed box filled with a gas such as helium, neon or a mixture of the two.
In order to control when this voltage is applied, a separate detector (often containing a pair of scintillators placed above and below the box) is needed.
When this trigger senses that a cosmic ray has just passed, it fires a fast switch to connect the high voltage to the plates.
A streamer chamber, in contrast, typically has only two plates, at least one of which is transparent (e.g. wire mesh or a conductive glass).