Thursday, December 01, 2005

Muon-assured Defense

This is old news, but it deserves a mention just because of the coolness factor. Earlier this year, Los Alamos National Laboratory announced an advance in the detection of fissile material, such as that which could be smuggled into the country to detonate a nuclear explosion. Finding such material poses significant technological and financial problems. it is not practical to search everything that comes into the country, and there is no current technology that enables mass screening of import cargo containers.

LOS ALAMOS, N.M., Feb. 19, 2005 -- Trillions of cosmic rays that constantly bombard Earth could help catch smugglers trying to bring nuclear weapons or materials into the United States. Los Alamos National Laboratory scientists have developed a detector that can see through lead or other heavy shielding in truck trailers or cargo containers to detect uranium, plutonium or other dense materials. Their technique, muon radiography, is far more sensitive than x-rays, with none of the radiation hazards of x-ray or gamma-ray detectors now in use at U.S. borders.

This technique was discussed in an article in The Economist. Apparently, the cost would be about a billion dollars. They point out that one billion is far less than what we have spent on the "Star Wars" antibalistic missle defense system. And unlike Star Wars, this might actually work.

Fast-moving muons wreak havoc on air molecules as they pass by—stripping away electrons to create positively charged ions. That makes their passage easy to detect using banks of so-called drift tubes, which pick up the electrical signal generated by the ions. Dr Morris and Dr Chartrand's idea is to build boxes big enough for lorries to be driven into. Each box would have two layers of drift tubes above the lorry, and two below. This arrangement would allow muons to be tracked as they went into the lorry and as they came out. Any deviation from a straight line would mean that a muon had run into one or more atomic nuclei on its way through. By tracking enough muons and applying enough computing power, the two researchers think that they would be able to spot large concentrations of heavy nuclei—in other words, nuclear explosives. So far, they have the computing power, but not the boxes. Simulations, though, suggest that the idea would work. A sphere of uranium weighing 20kg (about what is needed to make a bomb) shows up clearly. And even if the material were broken down into smaller batches alarm bells would go off in the detection software—although in this case it would not be able to locate the uranium precisely. The next step is to build a real detector and then, if that works, to convince the authorities to support widespread deployment.
It is good to know that someone is working on this, and that they have something that ought to work, for a good price.