Muon Detector Could Thwart Nuclear Smugglers

Ben Sullivan writes "Cosmic rays that bombard Earth could help catch smugglers trying to bring nuclear weapons into the U.S. Los Alamos scientists say they've developed a detector that can see through lead or other heavy shielding in truck trailers or cargo containers to detect uranium, plutonium or other n-bomb materials. Their technique, muon radiography, is reportedly far more sensitive than x-rays, with none of the radiation hazards of x-ray or gamma-ray detectors now used at border crossings. From Science Blog."

Why muons go straight through

[PiMuNu]

The reason muons don't stop inside our bodies is because they (a) don't interact with atomic nuclei much and (b) are quite heavy.

So there are lots of different particles, like protons and neutrons or electrons, that you could use.

But protons bounce off atomic nuclei because they see something called the "strong force". This means they stop very quickly.

On the other hand, electrons don't see the strong force, which means they don't bounce off the atomic nuclei much at all. In fact, electrons spend all their time bouncing off the electrons that whizz round the outside of the atom.

The thing is though that electrons are much lighter than protons, so even though they only see the electrons in the atom, they still bounce right off them. The same goes with photons (e.g. light, x-rays).

This means that the electrons (and x-rays) get stopped very quickly too.

So both the electrons and protons get stopped very quickly, which means they deposit much more energy inside you = nasty radiation damage!

Muons, OTOH, will zip straight through as they don't see the atomic nuclei and are relatively heavy. This means they do less radiation damage, and you need fewer of them.

This is why you can get away with using atmospheric muons. It also explains why the atmospheric muons are there in the first place - all the other particles get stopped in the atmosphere.*

*Except some special particles called neutrinos - but let's not go there.

Here's a general particle physics wikipedia [wikipedia.org]

Re:Safety

[Anonymous Coward]

This system doesn't produce anything it merely detects changes in existing particles. Because the system relies on existing radiation rather than trying to make it's own there are no safety issues with regard to the radiation used.