New Neutron Scatter Camera to Detect Smuggled Nukes 125
Researchers at Sandia National Laboratories in California are developing a new neutron scatter camera that they claim will be able to detect radiation through much more shielding and at much greater distances than traditional tech. "The neutron scatter camera consists of elements containing proton-rich liquid scintillators in two planes. As neutrons travel through the scintillator, they bounce off protons like billiard balls. This is where "scatter" comes into play -- with interactions in each plane of detector elements, the instrument can determine the direction of the radioactive source from which the neutron came. [...] Computers record data from the neutron scatter camera, and using kinematics, determine the energy of the incoming neutron and its direction. Pulse shape discrimination is employed to distinguish between neutrons and gamma rays."
Not really the case, these are feigned interests (Score:4, Insightful)
I wish nobody cared (Score:2, Insightful)
Don't get me wrong being able to detect a nuke is a good thing. However, to me this seems to fit right in along with the whole security theater schtick that the government is pulling. Throw out some nifty vaporware. Have some conveniently thwarted plots and you have a carte blanche to do whatever you want with personal liberty.
Without getting into an argument over the actual probability (well over-blown if you ask me) of a terrorist attack occurring, being nuked is the least of my fears. Something that utilizes few resources, like say hijacking a plane, is much more likely to be the plan of attack. The government throws out all these crazy, high-concept plots just to proliferate fear.
I know I'm off-topic for this specific device, but I feel that the whole counterterorism deal is what's behind this. As another post pointed out, it's what is driving research funding, and that makes me just a little uncomfortable.
Re:I wish nobody cared (Score:5, Insightful)
Well, the whole point of having devices like this, is that, if you can directly detect somebody trying to smuggle in a nuke or even a backpack bomb, you don't need to spy on the whole country because you are afraid someone might.
Advances such as these should be trumpeted, as much as possible, to indicate that we don't need to have our civil liberties trampled in order to defend ourselves. That is, defending against terrorism is something for grad students to work on with big defense grants, not, a bunch of jackasses that want to play rent-a-cop at the CIA.
Some background (as it were...) (Score:4, Insightful)
What has been done here is fairly clever, although I'm doubtful as to the ultimate viability due to low cross-sections and high backgrounds and easy work-arounds by the bad guys.
Spontaneous fission produces fast neutrons, which are relatively hard to shield against. First they have to thermalize, then get captured. Things that are good at shielding gamma rays (heavy elements) are lousy at thermalizing neutrons (light elements), so it makes the bad guy's shielding problems harder to solve.
Ergo, if you can detect fast neutrons, and determine where they are coming from, you have a backup bomb detector that is harder to beat. The way Nick is proposing to do this is with a setup in which you have two planar liquid scintillator detectors and look for coincidences (suitably delayed by the neutron's quite significant travel time) between them. Fast neutrons deposit energy into the detectors via proton recoil, which creates a distinct kind of optical event from electron-positron showers produced by gamma rays. Furthermore, you tend to get forward scattering, so you can at least tell which hemisphere the neutron originated from, most of the time.
The data analysis is tricky, the neutron detection rates will be low, and if I was designing this I'd go for a thick secondary detector and count on thermalization and capture to create the secondary signal, rather than having a thin secondary detector looking for another recoil event. With a segmented detector or similar you'd be able to still do a reasonable job of the kinematics.
Discriminating against cosmic ray neutrons is going to be painful for this technology, however, and furthermore the comment that another poster made that "this tech shows we don't need to give up our civil liberties to be safe because it proves we can catch stuff at the boarder" is to my mind utterly wrong-headed. It assumes the border can be made perfectly impermeable, and that is simply not the case, as a million kilos of grass or whatever it is a year proves. As long as there is a chance that one bad guy can slip something through, Americans have two choices: be willing to die for your freedom, or give up your freedom (and be willing to die anyway, because a police state will not protect you.)
Final thought: we used to joke, back in the day, that we could sell our detector design to the U.S. navy as a means of detecting stationary nuclear submarines (it took a couple of days for useful neutrino statistics to build up when the prototype detector was about 10 m from a reactor core.) It looks like Nick might have found a way to do something very close to that after all...