Using Radio Waves to Detect Explosives

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."

Comments

Re:Interesting idea, but one caveat I perceve...

[Dr. Eggman]

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.

nuclear resonance is MRI without the "imaging"

[kris_lang]

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.

Re:nuclear resonance is MRI without the "imaging"

[Anonymous Coward]

... 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! :-)

Re:So, no more taking shoes off?

[QuantumG]

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.

Re:White powders?

[Anonymous Coward]

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

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