Los Alamos researchers foil nuclear smugglers with 200-terawatt laser
Most readers of ExtremeTech probably remember the unfounded panic following a few ill-informed reports over the ease of smuggling nuclear material over US borders. These reports made the crucial mistake of smuggling depleted uranium through a series of major American ports, and while the nuclear security on display in these areas was and is lacking, it was still an unfair test. Depleted uranium can’t be detected by radiation sniffers for the very same reason that the substance is useless to a would-be bomb maker: it’s not radioactive enough. Still, those reports brought awareness to a growing problem in an increasingly import-driven economy: with tens of thousands of shipping containers moving through US ports every day, how exactly can we expect to keep such porous borders safe from smugglers?
Happily, it’s a lot easier to detect a lump of plutonium than it is a stolen Mercedes or a compartment full of Russian brides. Conventional detectors range from hand-held rad-finders to drive-through detectors to X-ray scanners not unlike those used on people at airports. Each has its own set of problems, from being too bulky and slow for mass use, to being too focused and small-scale for mass use, to being too blunt and low-resolution for… you get the idea. Economies of scale work in reverse for the hard-working folks at port and border security. Now, Los Alamos National Laboratories has a simple proof of concept for a new addition to their arsenal, one that could help to fill some glaring holes in our nuclear border security.
The breakthrough involves detection of not just the presence but the quantity of a nuclear material. They don’t disclose the identity of the sample they “interrogated” in this study, but given its stated implications for the War on Terror, it will certainly be either a sample of weapons-capable uranium or plutonium isotopes. The result was achieved using the Trident laser to blast an ultra-thin sample of “deuterated” plastic, which means that it’s had its hydrogen atoms replaced with deuterium, a heavy hydrogen isotope. When subjected to a pulse of energy “50 times greater than the entire production of worldwide electrical power,” this sample releases a beam of deuterium nuclei traveling at around a tenth the speed of light. To clarify that last superlative, the output is 50 times greater than the worldwide production of power per half-picosecond, which was the duration of the Trident laser blast.
The deuterium beam only travels about half a centimeter before hitting a second emission sample (the actual sample being tested), and the heavy particles carry enough force to incite the release a storm of high-powered neutrons. These neutrons have an exceptional ability to travel through heavy materials — like, say, the metal exterior of a shipping container or even the shielding necessary to hide radioactive material from more mundane radiation detectors. Once through, the neutrons still carry enough power to start a low-level fission reaction. This causes the release of even more neutrons, which are referred to as “delayed.” Over the course of whole seconds (pah!) the sample will emit detectable neutrons in a pattern that shows both the identity and quantity of the sample.
Neutron detectors have been in use for border security for a while now, but they’ve been big and unwieldy. They have also relied on helium-3 for their work, and helium is becoming increasingly expensive and difficult to come by. The researchers fantasize about truck-mounted or even personally-sized versions of their detector, with all the attendant increases in security this would bring.
There are problems, though. As can be seen in the official video above, the “containers” interrogated in this experiment are very small, while real-life shipping containers range from 8 to 53 feet in length. There are almost 20 million such containers in worldwide circulation today. The Los Alamos scientists don’t shy from the idea of miniaturizing their new tech however, so they presumably have a hypothetical path in mind. Small isn’t necessarily better, though, as it’s hard to imagine this tech could assay the whole interior of a container, rather than a thin ribbon of space within it. Want to beat border security? Duct-tape your sample to the ceiling.
In any case, the patent is pending. US border security has taken a lot of flak over the years, and they will undoubtedly jump at any new technology that might shore up their many and well publicized security deficiencies.
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