Muon Detector — Design Notes and Sourcing Reality
The design
A slab of plastic scintillator glued to a silicon photomultiplier: a muon passing through the plastic makes a flash of light a few nanoseconds long, and the SiPM turns it into a pulse. One SiPM also fires constantly on thermal noise — so the instrument is two stacked units in coincidence, and only a pulse in both within nanoseconds counts as a muon. This follows the well-proven CosmicWatch lineage, adapted for our conditions and supply chain.
Why altitude is the experiment
Muons are born high in the atmosphere from cosmic-ray showers and decay on the way down, so the flux at the ground depends on how much atmosphere is above you. Nepal runs from 60 m to over 5,000 m of usable territory, and there are zero systematic muon flux measurements between 1,000 m and 5,000 m in this region. Each detector pairs with a pressure reading — the IESH's BMP280 already provides the atmospheric-depth reference the measurement needs.
Sourcing from Kathmandu
SiPMs and scintillator are not things you buy in New Road. Import routes, customs, and lead times currently dominate the schedule far more than any design question. The cost target is under NPR 25,000 per detector — the number that makes a school-hosted muon network plausible rather than rhetorical.
Status, honestly
Design study done; components being sourced; no assembled detector exists yet. This note will be followed by pulse traces when there are pulse traces, and not before.
Kathmandu, Nepal · 1350m asl