drag the glowing source rod · click the chamber to call down a cosmic ray · Space for a shower · H for the guide
FIELD GUIDE
This is a diffusion cloud chamber — a sealed volume of isopropanol vapour cooled at its base (the frosty plate, ≈ −78 °C) and warmed at its top. A thin layer above the cold plate becomes supersaturated: when a charged particle ionises the vapour, droplets condense along its path and the track glows. The layer is deepest and most sensitive just above the plate, so tracks bloom into view as they sink into it. Units are scaled for beauty, but the choreography is faithful.
READING THE TRACKS
Muon (μ⁻) — long, straight, faint icy lines raining from the sky: cosmic rays at several GeV
Alpha (α) — fat, bright, short golden threads from the source rod. Watch for the Bragg blob: a final flare as it stops
Beta (e⁻) — thin wandering threads, easily scattered, curled into tight spirals by the magnet
Positron (e⁺) — a beta that spirals the other way; born paired with an electron in a V-fork
Gamma (γ) — invisible. Betrayed only by the Compton electrons it kicks loose, or by an e⁺e⁻ pair appearing from empty space
THINGS TO TRY
Drag the glowing source rod anywhere on the plate; pick Am-241 (α), Sr-90 (β) or thorium ore (α+β+γ)
Slide the magnet: the Helmholtz coils light up and every charged track curls — betas into corkscrews, muons into stately arcs, pairs into trumpets. Flip the sign to flip the curl
Press Space — a high-energy cosmic ray triggers an electromagnetic cascade: γ → e⁺e⁻ → bremsstrahlung γ → …
Press B to fire the muon beam line on the +X port; with the magnet on, the momentum spread fans out like a spectrometer
Click anywhere inside the chamber to aim a cosmic muon at that spot
The Geiger counter clicks faster near heavy ionisation — its CPM is in the top-left readout
SHORTCUTS
Space shower · B beam · P pause · M sound · A auto-orbit · S snapshot · Q quality · 1–4 presets · H guide
PHYSICS NOTES
Tracks are integrated with the Lorentz force q·v×B under continuous energy loss and multiple Coulomb scattering. Alphas show a Bragg peak (rising ionisation before stopping); betas straggle; gammas follow an exponential attenuation law, Compton-scatter below the 1.022 MeV pair threshold and convert above it. Cascades multiply by bremsstrahlung and pair production until the shower falls below critical energy. Droplets sink, diffuse and fade like real condensation trails.