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A spark chamber is a type of instrument to detect charged particles, i.e., ions, electrons or positrons. One general design is parallel plates with some voltage difference, positioned just further apart than would lead to spontaneous sparks. The presence of the charged particle between the plates "encourages" a spark, and monitoring the electrical characteristics of the circuit providing the voltage 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.