Called a Hodoscope (from the Greek “hodos” for way or path, and “skopos:” an observer) it is a type of detector commonly used in particle physics that make use of an array of detectors to determine the trajectory of a particle.
When a muon flies through both layers of the array, it will trigger two tubes simultaneously. By measuring the output coincidence detected between the top and bottom layers it indicates the location of where it passed through.
To further minimise background radiation shielding (brass plates) is also placed between the layers of tubes and also method of called coincidence detection.
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