Beta
×

Welcome to the Slashdot Beta site -- learn more here. Use the link in the footer or click here to return to the Classic version of Slashdot.

Thank you!

Before you choose to head back to the Classic look of the site, we'd appreciate it if you share your thoughts on the Beta; your feedback is what drives our ongoing development.

Beta is different and we value you taking the time to try it out. Please take a look at the changes we've made in Beta and  learn more about it. Thanks for reading, and for making the site better!

Muon Detector Could Thwart Nuclear Smugglers

Hemos posted more than 9 years ago | from the interesting-applicatons dept.

Security 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."

cancel ×

54 comments

Sorry! There are no comments related to the filter you selected.

Hope it performs better... (4, Interesting)

3waygeek (58990) | more than 9 years ago | (#11864244)

than what these guys used. [10news.com]

Re:Hope it performs better... (4, Insightful)

sgant (178166) | more than 9 years ago | (#11864293)

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).

Re:Hope it performs better... (3, Insightful)

Anonymous Coward | more than 9 years ago | (#11865188)

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.

Re:Hope it performs better... (1)

Wandering Wombat (531833) | more than 9 years ago | (#11870158)

That would be here" [slashdot.org] . Inspiring, isnt it?

Re:Hope it performs better... (0)

Anonymous Coward | more than 9 years ago | (#11885446)

"Interesting"? My ass.

Do you know what they use as a moderator in nuclear reactors? Water. It is an excellent moderator because it is very hydrogen-rich. Do you know what the fucking ocean is made of? Water.

Do I have to put two and two together for you to see why it might be tough finding a radioactive source in the fucking ocean????

Geeze, pick up a book sometime before you show your ignorance to the rest of us.

Re:Hope it performs better... (2, Funny)

bigpat (158134) | more than 9 years ago | (#11869918)

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!

Well, here at work.... (1)

purduephotog (218304) | more than 9 years ago | (#11871433)

... we've the story being forwarded of one of our coworkers stopped at the border coming into the US from Canada for the very thing you say isn't possible.

Seeing as how he is a rather highly placed and takes a rather cynical view of the government leads me to believe his story about being yanked out of the Customs line and asked to undergo a radiological exam (geiger counter?).

Apparently he had been surrounded by officers since he'd gotten onto the bridge- don't ask me how because the next few cars were waved thru without an inspection (unverified).

I guess radioactive Iodine is easier to find :)

Re:Hope it performs better... (2, Funny)

Doc Ruby (173196) | more than 9 years ago | (#11874038)

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

Re:Hope it performs better... (2, Interesting)

Nuffsaid (855987) | more than 9 years ago | (#11865577)

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!

Re:Hope it performs better... (4, Interesting)

DustMagnet (453493) | more than 9 years ago | (#11867371)

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.

Fly me to the muon...! (-1, Offtopic)

GuruBob (81090) | more than 9 years ago | (#11864273)

Forgive my momenatry lapse of whimsy.

Old tech (1)

madaxe42 (690151) | more than 9 years ago | (#11864283)

This has been around for years - and the BBC reported it (in spite of it being old news) about 2 weeks ago.

Safety (2, Insightful)

Urkki (668283) | more than 9 years ago | (#11864286)

  • 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...

Re:Safety (5, Insightful)

ecotax (303198) | more than 9 years ago | (#11864304)

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.

Re:Safety (1)

Urkki (668283) | more than 9 years ago | (#11865008)

Good point. Might have been a good idea if I had RTFA before hitting reply ;-)

Re:Safety (2, Insightful)

jfdawes (254678) | more than 9 years ago | (#11881424)

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.

Re:Safety (1, Informative)

Anonymous Coward | more than 9 years ago | (#11885712)

This system doesn't produce anything it merely detects changes in existing particles. Because the system relies on existing radiation rather than trying to make it's own there are no safety issues with regard to the radiation used.

Re:Safety (1)

Eviscero (675126) | more than 9 years ago | (#11886084)

Is the muon detecter a passive system? If so, it would detect radiation as it propogates from a target object and not have to 'illuminate' or 'stimulate' it to return a result.

Harmless? (1)

Sigafoose (864572) | more than 9 years ago | (#11864357)

Even though its old news, maybe we should still keep our eye on the rise of cancer cases coming from the border areas now.

Re:Harmless? (0)

Anonymous Coward | more than 9 years ago | (#11868981)

Yes, because now that we know that these muons are constantly bombarding us, we're at greater risk.

?

Re:Harmless? (0)

Anonymous Coward | more than 9 years ago | (#11885467)

Hee hee. Dude must live in the cartoon universe where you don't fall until you realize there is no earth under you.

tin foil foiled (4, Funny)

Patrik_AKA_RedX (624423) | more than 9 years ago | (#11864395)

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

Re:tin foil foiled (1)

cliffyqs (773401) | more than 9 years ago | (#11866564)

Not necessarily; it doesn't mention tin foil specifically, so maybe it still works.

Just n\use more layers, or develop a better tin foil.

Re:tin foil foiled (1)

mdielmann (514750) | more than 9 years ago | (#11869160)

I guess the only option is to scramble the signals at the source. Hmm, that might not be too original. It certainly explains a lot of the people who wear tin foil hats...

Re:tin foil foiled (1)

ikkonoishi (674762) | more than 9 years ago | (#11885708)

Thats why I switched to depleted uranium foil years ago.

A promising development... (1)

ecotax (303198) | more than 9 years ago | (#11864423)

... for the muon-detector-industry.

As for delivering delivering plutonium to the US, it seems using trucks isn't necessary at all, this [missilethreat.com] seems much more practical.

Re:A promising development... (1)

TopSpin (753) | more than 9 years ago | (#11864920)

this seems much more practical.

Indeed. At least until we deploy this [missilethreat.com] all over the Sea of Japan in 2005.

Re:A promising development... (1)

Half-Baked (771927) | more than 9 years ago | (#11871585)

Yes, But as John Stewart pointed out those missiles can only reach Blue states so the White house isn't concerned about them

Re:A promising development... (2, Insightful)

Doc Ruby (173196) | more than 9 years ago | (#11874063)

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.

Re:A promising development... (1)

ecotax (303198) | more than 9 years ago | (#11875092)

Point taken.

The point that I was trying to make, in a cynical way, is that if/when people really want to get something in, they will. Compare it to the 'war on drugs': it may have had an influence on the price of drugs, and the prisons may be a bit fuller, but that's about it. Everything is still available, if you're willing to pay the price. And the price won't be an issue in the case of plutonium.

Re:A promising development... (1)

Doc Ruby (173196) | more than 9 years ago | (#11877892)

I like this muon detector - better than X-rays etc, at least. And it seems like "dual use" tech for government investment. I just distrust the whole system, because I expect they'll deemphasize nonproliferation (at the source), which will increase the global nuclear weapons industry, with inevitable catastrophes, here or abroad.

Why muons go straight through (5, Informative)

PiMuNu (865592) | more than 9 years ago | (#11864485)

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 [wikipedia.org]

Re:Why muons go straight through (0)

Anonymous Coward | more than 9 years ago | (#11865466)

I was just wondering.

Why you used so many paragraphs.

It's harder to read.

When it's all spaced out.

Sorry for replying in the same style.

Re:Why muons go straight through (1)

clambake (37702) | more than 9 years ago | (#11866795)

*Except some special particles called neutrinos - but let's not go there.

Because nutrinos go through just about everything... even if you could build a detector smaller than, say, the earth, it'd be like trying to x-ray a paper bomb inside of a paper suitcase, wrapped in paper... on the other hand it'd be GREAT at finding people smuggling suitcases full of neutronium. Then again the 450,000,000 forklifts the guy uses to move his suitcase would also be an indicator.

Re:Why muons go straight through (2, Interesting)

gumbi west (610122) | more than 9 years ago | (#11871860)

Oops, muons [wikipedia.org] are leptons [wikipedia.org] just like electrons [wikipedia.org] . 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.

Re:Why muons go straight through (1)

PiMuNu (865592) | more than 9 years ago | (#11875112)

Not sure your quite right... From the PDG Handbook [dur.ac.uk] * High-energy electrons predominantly lose energy in matter by bremsstrahlung, and high-energy photons by e+e pair production. Section 24.7.1

Re:Why muons go straight through (1)

gumbi west (610122) | more than 9 years ago | (#11906780)

good catch. Electrons do primarily interact with the nuclei and not with other electrons. Same goes for muons

Re:Why muons go straight through (1)

PiMuNu (865592) | more than 9 years ago | (#11908129)

No... they pair produce in the field of the atomic electrons I think.

Re:Why muons go straight through (2, Insightful)

hubie (108345) | more than 9 years ago | (#11885596)

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 [aaas.org] today.

Re:Why muons go straight through (1)

PiMuNu (865592) | more than 9 years ago | (#11886546)

Fair point, I was sacrificing accuracy to simplicity. Simplicity is happy but now accuracy rears it's ugly head...

I do stand by my comment that muons of a certain energy penetrate much further through the atmosphere than pions or protons or electrons or gamma at that energy, for the reasons I outlined. Ditto for going through materials like lead. (Except certain special cases like visible light)

Re:Why muons go straight through (2, Insightful)

hubie (108345) | more than 9 years ago | (#11893824)

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 [web.cern.ch] 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.

Re:Why muons go straight through (1)

PiMuNu (865592) | more than 9 years ago | (#11908153)

Okay, I'm half swayed - but two things I don't understand:

1) Where does the energy for all these pions come from? That's 140 MeV per pion... and a pion is a quark anti-quark pair so at least half has to come from the cosmic proton.

2) Why do hadronic calorimeters stop hadronic showers but not muons? Why do hadrons shower whereas muons don't?

Both these points boil down to my previous argument, that protons will have hadronic (i.e. strong force) interactions that the muons won't have, which is the dominant energy loss mechanism. I confess though, I don't have a good reference.

Re:Why muons go straight through (1)

hubie (108345) | more than 9 years ago | (#11911142)

I am a cosmic ray physicist expatriate, so bear with me as I dust off some brain cells:

1) The energies of the protons hitting the top of the atmosphere are very very high. The muons themselves at the ground have energies of a few GeV, and they themselves have lost 2 GeV just getting down through the atmosphere. The primary particles (mostly protons) creating the detectable ground-level showers have energies from tens of GeV's on up (TeV's, PeV's, etc.) The fluxes of these particles drop off as a power law with energy.

Incidentially, the highest energy cosmic ray detected was over 10^20 eV [leeds.ac.uk] ! I believe the flux for particles at that energy are something like one event per square kilometer per century or something like that.

2) Muons are leptons, so they are not affected by the strong force, as you mention.

For charged particles another source of energy loss is through radiation as they accelerate (or decelerate). When a charged particle passes close to a nucleus it can have its trajectory altered resulting in radiation emission. This is bremsstrahlung [web.cern.ch] . If the radiated photons have enough energy (greater than 1.02 MeV), they can pair produce into electron/postitrons and thus an electromagnetic cascade is born. It turns out that the energy radiated has a 1/m^2 dependence, which makes it very important for electrons, but basically nothing else (the muon being 207 times the mass of the electron, I believe). This is why muons don't create showers, or conversely why basically only electrons and photons do.

Because charged muons don't strongly interact, and they don't create showers, their dominant energy loss mechanism is due to ionization and atomic excitation (because they have charge), which is well described by the Bethe-Bloch equation.

Hadronic showers, by the way, are a little bit tricky because the shower profile and composition fluctuates so much (electromagnetic showers are very well behaved and easy to identify). To design them you need to take care to put an electromagnetic calorimeter in front of them so you can tell the difference between electromagnetic and hadronic showers. The material that makes up the EM part has to be something that will ensure a good EM shower, but with low enough Z so that the hadrons will not start their shower there. Occasionally hadrons will knock off an electron in the EM part, which will cause a EM shower and make it look like a EM event, but this is just part of the background that you need to take statistically into account by making good computer models (along with other things like getting a handle on how what percentage of hadrons at a given energy will be entirely contained in the calorimeter and what will leak out the back). You can't construct and analyze a particle detector these days without a very good physical model of it.

Re:Why muons go straight through (1)

PiMuNu (865592) | more than 9 years ago | (#11911369)

Okay, so I think the answer is that hadrons do lose more energy going through the atmosphere because of strong force interactions - but some still manage to get through because they have much higher energy to start with. Is that a fair paraphrase?

So I guess I was right about penetrating the lead briefcase or whatever, but perhaps a little dodgy wrt the atmospheric comment...

You can't construct and analyze a particle detector these days without a very good physical model of it.

Don't I know it...

Re:Why muons go straight through (1)

gumbi west (610122) | more than 9 years ago | (#11906805)

well, you also said, "So both the electrons and protons get stopped very quickly, which means they deposit much more energy inside you = nasty radiation damage!"

An electron and a muon with a few GeV will deposit the same amount of energy in something so long as they exit also at relativistic velocities. So, not quite.

Re:Why muons go straight through (1)

PiMuNu (865592) | more than 9 years ago | (#11908136)

No, the electrons will have pair production and brehmstrahlung. Muons will only have ionisation. See other posts.

Nb: this is a technical subject and not my speciality, but an interesting one - I may be wrong, but I stand by my reference the PDG (linked previously). If you can produce a counter reference, I would be intersted to see it.

Re:Why muons go straight through (1)

gumbi west (610122) | more than 9 years ago | (#11915192)

Oh, this is something that I'm actively researching, so it is my area of speciality. But the theoretical physics isn't the core of what I do so it somewhat isn't. Anyway, read the link to Bethe-Bloch up above to see what I'm talking about. It's the third paragraph that I'm talking about.

All I think is . . . (0)

Anonymous Coward | more than 9 years ago | (#11864524)

. . . COOL STINKIN' BEANS.

It's amazing how many solutions there are to a given problem, like the problem of "seeing" through things.

Troy Hurtubise might help (1, Interesting)

Anonymous Coward | more than 9 years ago | (#11865166)

Troy, inventor of such far-out yet functional devices like the bear encounter suit and fire paste, has finally flipped out [baytoday.ca] , or maybe he's on to something.

This looks promising but... (4, Insightful)

radtea (464814) | more than 9 years ago | (#11865380)

...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

Re:This looks promising but... (1, Insightful)

Anonymous Coward | more than 9 years ago | (#11868212)

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 . . . . this is might be able to both speed up processing and improve accuracy dramatically.

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:This looks promising but... (1)

drinkypoo (153816) | more than 9 years ago | (#11871217)

Of course, terrorists could always fall back to the obvious plan B: smuggling the weapon in hidden in a bale of marijuana.

Or you could just hide it in a shipment of cocaine and let the CIA transport it for you...

Through lead?? (1, Funny)

Kiriwas (627289) | more than 9 years ago | (#11865463)

We can now see through lead? I feel my childhood collapsing around me... Science has just surpased Superman [wikipedia.org]

Cylons? (0)

Anonymous Coward | more than 9 years ago | (#11868330)

Radiological Alarm!
Check for New Comments
Slashdot Login

Need an Account?

Forgot your password?

Submission Text Formatting Tips

We support a small subset of HTML, namely these tags:

  • b
  • i
  • p
  • br
  • a
  • ol
  • ul
  • li
  • dl
  • dt
  • dd
  • em
  • strong
  • tt
  • blockquote
  • div
  • quote
  • ecode

"ecode" can be used for code snippets, for example:

<ecode>    while(1) { do_something(); } </ecode>