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Muon Detector Could Thwart Nuclear Smugglers

Posted by Hemos on from the interesting-applicatons dept.

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."

17 of 54 comments (clear)

  1. Hope it performs better... by 3waygeek · · Score: 4, Interesting

    than what these guys used.

    1. Re:Hope it performs better... by sgant · · Score: 4, Insightful

      Of COURSE they're going to have this on the news and general media...they will certainly play up "hey, we have detection equipment so sensitive that it picked up on someone getting radiation treatment".

      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).

      --

      "Leo Fender was in a 'state of grace' when he designed the Stratocaster." -- Paul Reed Smith
    2. Re:Hope it performs better... by Anonymous Coward · · Score: 3, Insightful

      Remember when they couldn't find that lost nuclear weapon right off our shoreline for, like, damn near years? Inpenetrable detection net my ass. There could be a lot of material moving in and out and we might never know it.

      The same people who buy that silly SDI crap believe this too.

    3. Re:Hope it performs better... by Nuffsaid · · Score: 2, Interesting
      Lesson learned. Next time you try to smuggle radioactive material through a border, send someone who verifiably has had recent radioactive treatements.

      Customs officer: It's OK, we checked with your doctor. You can bring in that... uh... strange glowing giant lead cat toy!

      --
      Nuffsaid
      ________

      Don't know about his cat, but Schroedinger is definitely dead.
    4. Re:Hope it performs better... by DustMagnet · · Score: 4, Interesting

      False alarms are a huge problem with any detection system. I had a coworker stopped while entering the U.S. because they detected explosive residue. He'd been working with explosives for months. The residue level was so high they couldn't get the machine clean again. It kept detecting explosives without any sample. It cost a lot of people a lot of time to verify that he was safe.

      --
      'SBEMAIL!' is better than a goat!!
    5. Re:Hope it performs better... by bigpat · · Score: 2, Funny

      Police: Sir are you carrying a nuclear weapon or materials?

      Evildoer: No, sir. I just left my doctor's office and had received a radiation treat

      Police: (Calls doctor) Sir your story checks out sorry for the trouble.

      Evildoer: Thank you, sir. I understand completely...

      Police: Hey wait! Why does it say "Evildoer" next to your line in the script?!? I think I'd better have another look here. I knew that false leg with the timer counting down looked a little suspicious!

    6. Re:Hope it performs better... by Doc+Ruby · · Score: 2, Funny

      I don't think organized, committed nuclear terrorists will be as gullible as we Americans who foot the bill.

      --

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      make install -not war

  2. Safety by Urkki · · Score: 2, Insightful
    • with none of the radiation hazards of x-ray or gamma-ray detectors now used at border crossings.

    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...
    1. Re:Safety by ecotax · · Score: 5, Insightful

      Regardless of how harmful these muons are when passing through your body, there is certainly no *added* harm in this detection method, because the muons used are the ones from space that has passed through you anyhow.

      --
      "Money is a sign of poverty." - Iain Banks
    2. Re:Safety by jfdawes · · Score: 2, Insightful
      Sensationalism ... we just can't avoid it. From the article:


      With refinement, inspectors could declare most vehicles harmless in a border setting with as little as 20 seconds of muon exposure.


      Sure sounds like they are capable of producing masses of 3Gev particles to me.
  3. tin foil foiled by Patrik_AKA_RedX · · Score: 4, Funny

    We should have seen it coming: tin foil hats are useless now...

  4. Why muons go straight through by PiMuNu · · Score: 5, Informative

    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

    1. Re:Why muons go straight through by gumbi+west · · Score: 2, Interesting
      Oops, muons are leptons just like electrons . They have electric charge and interact with electrons via the electromagnetic force. As such, at relativistic velocities (which they are at, otherwise their half life would prevent them from descending so far into the atmosphere) they act as "minimum ionizing particles" and deposit about 2 MeV per cm^2/gram. multiply the density of an object and its track length and you will get about the amount of energy a meuon will give up while traversing it. For lead (density of about 12 g/cc), at 3 GeV, a muon will go about 4 feet in lead (it's an approximation, so being off by almost exactly the proverbial sqrt(2) from what is in the article almost proves I'm right).

      Anyway, the reason muons are so penetrating is that they have so much energy to start with, so they can afford to give it up slowly.

      BTW, as a coarse approximation, at sea level, cosmic background is about 1/3 x-rays and electrons, perhaps 1/6 neutrons and the balance is muons. That is by dose, not flux.

    2. Re:Why muons go straight through by hubie · · Score: 2, Insightful
      It also explains why the atmospheric muons are there in the first place - all the other particles get stopped in the atmosphere.
      Atmospheric muons are not what is left over because all the other particles have been stopped, they are actually secondary particles created by the primary particle interactions in the atmosphere. There are basically no primary muons. Muons survive to the ground because they are created further down in the atmosphere, and as another person pointed out, they are at least minimum-ionizing in energy.

      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 today.

    3. Re:Why muons go straight through by hubie · · Score: 2, Insightful
      At the relativistic energies we're talking about here (a few GeV), the dominant energy loss mechanism is through ionization and atomic excitation (for muons and protons, these energies are too low for radiative effects to be important, but as you pointed out earlier they dominate for electrons), which are described by the Bethe-Bloch equation. Basically in this energy range the energy loss is determined only by the particle velocity, so a muon and a proton moving at the same velocity will have the same range.

      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.

  5. This looks promising but... by radtea · · Score: 4, Insightful

    ...3% false positives is still orders of magnitude too high for a deployable system. There are a range of interesting things they might do to improve the accuracy.

    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

    --
    Blasphemy is a human right. Blasphemophobia kills.
  6. Re:A promising development... by Doc+Ruby · · Score: 2, Insightful

    You can't trust what MissileThreat.com says about missile threats. Every page declars they're promoting SDI. They're interested in contracts, not truth.

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    make install -not war