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Using Radio Waves to Detect Explosives

Posted by samzenpus on from the tuned-to-boom dept.

deadmantyping writes "A Japanese research group published a paper describing a method to detect explosives in luggage using radio waves. The method relies upon nitrogen nuclear quadrapole resonance (NQR) and is able to distinguish between different white powders, whereas currently used x-ray technology is not."

7 of 99 comments (clear)

  1. Re:Interesting idea, but one caveat I perceve... by Dr.+Eggman · · Score: 5, Insightful

    What if a crazy man just straps some bombs on, walks up to the security checkpoint and sets himself off? There's no security check to protect the first security check. Better add one.

    ...and recurse.

    --
    Demented But Determined.
  2. That's nice by overshoot · · Score: 4, Insightful
    I wonder how it is at distinguishing between common metallic solids and thermite?

    A little oxidized iron, a little aluminum powder, a tiny amount of binder, press, and you have the makings of some attractive plaques or statuary. A bit of magnesium wire and a battery and you have everything you need to start a large mass of aluminum burning. Spectacularly.

    Good thing none of the Bad Guys have the brains of a flatworm. Or at least, that's what our whole air travel security strategy assumes.

    --
    Lacking <sarcasm> tags, /. substitutes moderation as "Troll."
  3. nuclear resonance is MRI without the "imaging" by kris_lang · · Score: 5, Informative

    so this is called nuclear magnetic resonance spectroscopy.

    Doing it with a gradient field and a special pulse sequence lets you get the
    vibrational amplitudes of your protons based on their position within the gradient field.
    That's what gets you MRI images. Before MRI images, nuclear spectroscopy was used to
    resonate the "nucleus" of atoms/molecules/conglomerations of molecules at varying radio-frequencies to see if there was any resulting resonance and output RF (radiofrequency) signal.

    Protons resonate at 2.4 GHz approximately (which is the frequency used in microwaves to resonate the H's in the {H}_2{0} molecules in your food and heat it.

    1. Re:nuclear resonance is MRI without the "imaging" by Anonymous Coward · · Score: 5, Informative

      ... but this is NQR which is examing the 4th order (as I can recall, maybe is was 2nd-order, I don't remember anymore:-p) of the nucleus. It's very similar underlying principles as MRI and NMR (and thus implementatin scheme is similar) but the physical interaction mechanism is the quadrapole momeent rather than the dipole moment of the nucleus.

      The problem with NQR and SQUID is that the measurement is extremely sensitive and it is difficult to filter out false positives. SQUIDs are very sensitive to magnetic perturbations and noise. Heck in the lab it can pick up the noise caused by the underground train. So the design has to be extremely precise and the filters need to be carefully designed. Also NQR technique only can detect certain substances that contain the molecular signature of interest (in this case N14 (i think?)). You need to induce a very large magnetic field (relative to the nucleus) to induce NQR. The SQUID can pick up the magnetic distrubance, but you still need to induce the field. DARPA showed some demos of remote systems that could acheive this. The problem was the false positives were pretty high, because it turns out shoe soles haave N14 which can trigger a false positive.

      Nevertheless, it's a great acheivement and I hope they can iron out the kinks in this technology.

      So don't put those shoes in your baggage! :-)

  4. Re:So, no more taking shoes off? by QuantumG · · Score: 5, Interesting

    Please take off your: jacket, shoes, backpack (and take the laptop out of the backpack and put it in a seperate tray), hat, belt, mobile phone, keys, wallet (if it contains more than 3 rfid based entry keycards). Yes, I travelled international recently. It's not even consistent.. some places they'll make you take off your belt, other places, no, that's fine.

    Time before last I took a suit coat with me. Big solid metal coat hanger with nice sharp edges. They just let me carry it onto the plane. Had I tried to take a similar piece of metal on (say, a boxcutter) they would have denied me. Hmmm, wonder if there's a little big of class disparity there.

    The illusion of safety.

    --
    How we know is more important than what we know.
  5. Not all explosives contain nitrogen by dsci · · Score: 4, Insightful

    And not all nitrogen containing explosives are white powders. :)

    --
    Computational Chemistry products and services.
  6. Re:White powders? by Anonymous Coward · · Score: 5, Funny

    "What if I add some gun powder to my Coke?"

    Then I hope you're snorting it, not smoking it.