Muon Detector Could Thwart Nuclear Smugglers 54
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."
Safety (Score:3, Insightful)
Yeah, right. It will harmlessly pass through a bag of water like a human body, because water is such a lousy material at stopping radiation. That's why it's not used in nuclear reactors or cosmic ray detectors...
Re:Hope it performs better... (Score:5, Insightful)
It's a propaganda tactic, play up that they can detect almost anything to make the bad guys think twice in trying to slip something in undetected. Since plutonium etc is hard to get as it is, perhaps the bad guys wouldn't want to risk losing it so easily (the risk here is losing the plutonium, not "getting caught" as human life means nothing to them as they've shown over and over).
Re:Safety (Score:5, Insightful)
Re:Hope it performs better... (Score:3, Insightful)
The same people who buy that silly SDI crap believe this too.
This looks promising but... (Score:5, Insightful)
The natural move from my point of view is to look at mu-N interactions, where a muon blows apart a nucleus in the target material, producing a shower of excited nuclear fragments and neutrons. Heavy materials such as plutonium will have a much different cascade signature than relatively light things like iron, so it may be possible to develop a quite specific finger-printing mechanism that would be hard to work around. With a muon detector on top to act as a trigger, and some combination of gamma and neutron detectors nearby, this is might be able to both speed up processing and improve accuracy dramatically.
Of course, terrorists could always fall back to the obvious plan B: smuggling the weapon in hidden in a bale of marijuana.
--Tom
Re:This looks promising but... (Score:1, Insightful)
Since the inelastic scattering rate is so low, this will end up taking much longer. For 10 kg of plutonium, expect to wait on the order of an hour to see a single inelastic (shower) event, and a single event is not going to be enough to strongly differentiate the type of material.
But, besides that, you would need a collider scale detector system to reconstruct that shower (you need to know where it occurred and various energies), which would be a few orders of magnitude more expensive than the simple muon detectors for the original setup.
Not a bad idea, but just infeasible.
Re:A promising development... (Score:3, Insightful)
Re:Safety (Score:3, Insightful)
Sure sounds like they are capable of producing masses of 3Gev particles to me.
Re:Why muons go straight through (Score:3, Insightful)
At ground level muons are about the only thing you can use for this purpose because the other particles you mentioned (protons, neutrons, and electrons) do not have appreciable penetrating energy because they are all interaction products. Neutrinos, as you alluded to, interact so weakly that they are both too tough to detect, and for the same reason they wouldn't make very good probe particles. Ground-level muons are routinely used to calibrate cosmic ray detectors, except for the neutrino detectors which are located deep underground to get away from atmospheric muons.
By the way, muons have been used as probes before. The most fameous example was searching for hidden chambers in the Great Pyramid of Chefren. Apparently they're still doing it [aaas.org] today.
Re:Why muons go straight through (Score:3, Insightful)
Muons are the most dominant charged particle in terms of flux on the ground not because they they can travel longer through the atmosphere, but because when a high-energy primary proton comes barrelling through the atmosphere it knocks off lots of pions in the downward direction that then decay into high energy muons. For every one proton that initiates such a particle shower, you get many many muons.