Photoluminescent method detects explosives at a distance

EETimes ^ | October 18, 2004 | R. Colin Johnson

[EvilOverlord]

Cool stuff

[Michael.SF.]

Experience in photoluminescent spectroscopy has helped university researchers bring to light a method by which

Pun intended, I assume?

[St.Mark]

Why isn't this deployed in Iraq right now....?

[EvilOverlord]

Why isn't this deployed in Iraq right now....?

I agree. This should be expedited.

[Fatuncle]

My God, do you know how many lives and injuries can be saved with this simple little trick??!!??

We need them all over Iraq now.

[Ditter]

Look at this.

[Drammach]

Why isn't this deployed in Iraq right now....?

Why isn't this deployed in our airports right now?

This technology has been sitting around for a year without implementation?

All sensitive areas should have these scanners set up and running at major events..

It falls under the classification of "national security"...

[Drammach]

Congress should over-ride normal patent procedures, give these people limited commercial rights, and assert that national security allows government use immediately..

Then get these units on the next plane to Iraq, Afghan, and U.S. Airport terminals, as well as high security facilities throughout the nation.. ( Nuclear reactors, arms depots, railroad terminals, major business districts, border crossings, etc.. )

[Wonder Warthog]

"Why isn't this deployed in Iraq right now....?"

Because it takes a great deal of research, engineering, time, and money to reduce what is essentially a quick and dirty science experiment into a rugged, reliable, portable, instrument. Designing such things is what I do for a living, and it is complex and time consuming.

The article is full of "golly-gee", "gee-whiz", "look how neat and all the other scientists missed it", when in fact the technique is well-known and used for other things. The thing that made this possible is that the group who observed it had a new, more sensitive detector that previous groups who had looked at the effect did not have. Very probably that detector requires liquid nitrogen (or helium) cooling, and is nicely practical for use in a research lab. Getting it to work in the Iraqi desert at midsummer is a whole other animal.

[EvilOverlord]

Very probably that detector requires liquid nitrogen (or helium) cooling, and is nicely practical for use in a research lab

I agree with most of what you say, except for the part about the detector. The article states that the standard issue night vision goggles is enough to detect the effect.

The only question is how expensive/rugged is the green laser.

[rawhide]

"It turns out that all explosives use groups of nitrogen molecules bonded to two oxygen molecules, which makes them very reactive — they can't help but seep out into the air around anything concealing them. When our green laser hits these molecules they photoluminesce at the 705-nm wavelength. Anything else that radiates at that frequency also radiates at nearby frequencies. Only explosives emit in this very narrow band," said Hummel.
"As a consequence, Hummel's detector could theoretically sense a single molecule from an explosive's "aroma" without fear of false positives, by using two sensors — one for explosives and one to prevent false positives. The primary sensor has a filter so it only senses exactly 705-nm wavelengths, thus "arming" the alarm. But the alarm is only set off if a second, "fail-safe" sensor verifies that there is no equally strong radiation at wavelengths adjacent to 705 nm, thus preventing false positives, according to Hummel."

I do not agree this will be fail safe. One way I see to outwit this test would be to have in addition to the explosives material present, another item which would give off radiation at the 705-nm wavelength and also at the additional nearby frequencies. This would trip off the alarm on the second 'failsafe' sensor, thereby indicating this item giving off radiation is not confined to just explosives frequency, when in fact explosives along with this second item are both giving off radiation, thereby giving the tester the false assumption that no explosives are present.

[SC Swamp Fox]

I do not agree this will be fail safe. One way I see to outwit this test would be to have in addition to the explosives material present, another item which would give off radiation at the 705-nm wavelength and also at the additional nearby frequencies.

Bingo!

You just rendered the device useless.

[Wonder Warthog]

"I agree with most of what you say, except for the part about the detector. The article states that the standard issue night vision goggles is enough to detect the effect."

That "might" work under highly artificial conditions (like shining the laser over an open bottle of the explosive, and exciting the concentrated vapors) but I guarantee you that "standard issue night vision goggles" will NOT be sensitive enough to detect explosive vapors in the real world at the much lower concentrations under which they will be present in the field.

"The only question is how expensive/rugged is the green laser."

No, the real question is how expensive and rugged the detector is. Believe me, I "know" about this stuff. We were attempting to do infrared fluorescence (the proper term for "photoluminescence")when I was in grad school back in the late seventies. The detectors back then were just not sensitive enough.

[Rebel_Ace]

"Bingo!

You just rendered the device useless."

Well, not exactly. The device could still POSITIVELY identify explosives, as long as they were not "masked" in the manner you describe. It raises the bar, so that "improvised" explosive devices, or other primative or crude devices or raw explosive materials would likely be detected 100% of the time, whereas "professional" or military grade production items might contain "masking" material.

[Southack]

"The researchers have proven that the effect works with TNT, nitroglycerin and the plastic explosives trinitrofenil-Nmetilnitramina (Tetryl), hexahydro-trinitro-triazine (RDX), octahydro-tetranitrotetrazocine (HMX) and pentaerythrol tetranitrate (PETN)."

RDX is what the Soviets stole from us to use in their first nuclear weapons. Their other conventional explosives had a nasty habit of pre-detonating due to the exposure to radiation.

[lepton]

Well, they described how to defeat it...that's always useful. /sarcasm

[BobS]

"It turns out that all explosives use groups of nitrogen molecules bonded to two oxygen molecules..."

How about chlorates? Potassium perchlorate and chlorate are also explosive.

[chipengineer]

>Very probably that detector requires liquid nitrogen (or helium) cooling

Sensitive detection of 705nm may require some cooling, but not that much.

[raygun]

Iraq? Can you imagine the Palestinians horror at being on the wrong end of beeber stuned like that?

[jwalsh07]

Great, now thats what I'm talking about.