1) Scientific instrument 2) Tracer for ionizing particles 
A hodoscope (from the Greek `hodos` for way or path, and `skopos:` an observer) is an instrument used in particle physics experiments to detect passing charged particles and determine their trajectories. Hodoscopes are characterized by being made up of many segments; the combination of which segments record a detection is then used to infer wh...
instrument for tracing paths of ionizing particles
[n] - (physics) scientific instrument that traces the path of a charged particle
hodoscope In physics, an assembly of particle detectors used for observing the paths of cosmic-ray and other particles; used to study cosmic radiation or to study particles in accelerator experiments.
noun (physics) scientific instrument that traces the path of a charged particle