A spark chamber is a type of instrument to detect charged particles, i.e., ions, electrons or positrons. A design is parallel plates with some voltage difference barely too far apart to allow spontaneous sparks. The presence of the charged particle between the plates "encourages" a spark, and monitoring the electrical characteristics of the circuit effectively detects the particle.
As general-purpose charged-particle detectors, spark chambers are no longer used much, but I've seen their use in gamma ray detectors in spacecraft. Detecting gamma rays is a challenge and a general strategy is to provide material for them to interact with, interactions that can produce or displace charged particles.