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 an energetic particle.
When a muon flies through the detector, it will trigger two tubes simultaneously. By graphing which of the two tubes are triggered on an array of 81 LEDs, it gives an indication that a muon was detected as well as where it struck.
The detector minimises background radiation using some shielding (brass plates) between the layers of tubes and also method of called coincidence detection. Muons travel through matter very easily passing through the brass plates and both axes of the detector without effort, whereas the terrestrial radiation will not. Consequently anything detected in both axes of the detector simultaneously is more likely to be a muon than local background radiation in, around and near the detector.
Figure 1. Basic overview operation of the 81 (9x9) Pixel hodoscope
Figure 2 Primary overall circuit using a simple LED Matrix for coincidence detection.
Note: The IC used in this desing a 74HC14 and not 74LS14. The 74HC14 is a high-speed Si-gate CMOS device Low-power Schottky TTL. It provides six inverting buffers with Schmitt-trigger action. It transforms slowly changing input signals into sharply defined, jitter-free output signals.