PARIS: Rogue states playing a shell game with atomic material or terrorists who try to smuggle a nuclear bomb into a city aboard a shipping container may one day be thwarted by a scanner said to be more accurate, cheaper, safer and more versatile than X-rays.

That is the hope of a team of physicists at the famous Los Alamos National Laboratory in New Mexico, where the first atomic bomb was pioneered.

Their invention is based on muons — sub-atomic particles that are part of the remains of cosmic rays. These rays are energy particles from space which disintegrate after they collide with the Earth’s troposphere.

Muons constantly bombard the Earth, but are harmless. They are, however, highly penetrative. A typical muon can penetrate water up to 30 metres (97.5 feet), for instance.

When a muon meets an object, it leaves it at an angle which is predictable and measurable. The size of the angle depends on the material — the denser the material, the bigger the angle.

The Los Alamos team have exploited this predictability by building a small test bench, comprising two upper trackers, to record the path of the muons as they arrived from the upper atmosphere, and two lower trackers, to record the path then made by the muons after passing through a test object.

A computer then processed this before-and-after tracking data into an image of the object — in this case, a small tungsten cylinder supported by a plastic plate and two steel support rails.

The experiment is a “proof-of-principle” endeavour to show that the idea works, and there is a long way to go before it emerges from the lab and into the public domain.—AFP