Signal Lab
Small interactive explainers for the physics that keeps turning up in our stories. Each one is built once and reused wherever a story needs it.
Alpha, beta and gamma
Why a plutonium source can sit harmlessly in a sealed capsule yet matter enormously if its contents are inhaled, and why a cesium source needs lead.
Signal Lab
Why some radiation stops at skin
Choose a type of radiation and watch where it stops.
Half-life
The same rule governs a PET tracer that is gone by the afternoon and a plutonium generator that will still be warm in the next century.
Signal Lab
What a half-life looks like
Each dot is one atom. Press play and watch them decay.
PET coincidence detection
A PET scanner never sees the tracer directly. It sees pairs of photons and works backward to where they came from.
Signal Lab
How a PET scanner finds a tumor
Each event sends two photons in opposite directions. Lines between the detectors they hit build the image.
Time, distance and shielding
Why a few steps back from a gamma source can matter as much as a slab of lead, and why a source hidden in the walls of a home kept exposing the people who lived there.
Signal Lab
Time, distance and shielding
Move the person and add lead. Watch how fast the dose rate falls with distance.
Isotope generators
How a nuclear pharmacy draws technetium-99m from a column of molybdenum-99, and how a cardiac PET lab has rubidium-82 ready again within minutes.
Signal Lab
How an isotope generator is milked
Press Play, then Elute. The daughter isotope grows back from its longer-lived parent.
Low-dose risk models
Three ways to draw the line between radiation dose and cancer risk, and why the low-dose end is still argued over.
Signal Lab
Three ways to draw low-dose risk
Drag the dose and compare what each model predicts.
Searching from the air
How survey crews hunt for a lost source: fly parallel lines, count photons, and look for the place where the counts climb above background.
Signal Lab
Finding a lost source from the air
Choose an altitude and line spacing, fly the survey, then reveal where the source was.
Nuclear batteries
A radioisotope generator turns decay heat into electricity, so its output runs down on the same half-life clock as its fuel.
Signal Lab
How long a nuclear battery stays warm
Drag the years forward and watch the heat output fall.
Cardiac CT and heart rate
Why a faster heart blurs the coronary arteries, and what faster scanners and motion correction buy back.
Signal Lab
Why a fast heart blurs a coronary CT
Raise the heart rate and change the scanner. Watch the artery on the right.
Neutron leakage and reactor size
Why a small reactor core loses a larger share of its neutrons through its surface, and what a reflector does about it.
Signal Lab
Why small reactor cores lose more neutrons
Release neutrons into cores of different sizes and build up the chart.
These simulations simplify the physics for clarity. They are teaching aids, not models of any specific scanner, source or patient.