The Organisation for the Prohibition of Chemical Weapons, which is overseeing the destruction of Syria's chemical arsenal, won this year’s Nobel Peace Prize. Destroying chemical weapons in a hurry is a difficult and dangerous task, and the need for fast results has to be balanced against the ever-present risk of lethal accidents.
New technology might help. The Pentagon’s Defense Threat Reduction Agency is interested in a new desktop apparatus that could pave the way to neutralizing chemical and biological weapons while they are still in their containers.
X-rays can break down chemicals like sarin, but producing a powerful enough x-ray beam from a compact, portable source has previously been impossible. That’s changing thanks to a technique developed by Young Bae, formerly with Brookhaven National Laboratories and founder of Y K Bae Corp. Bae’s method uses “warm dense matter” or WDM, which exists under the sort of extreme temperature and pressure conditions found inside stars and gas giants like Jupiter. In this context, ‘warm’ starts at about 11,000 degrees Celsius.
In the warm dense matter state, atoms are crushed together so that the electron shells from adjacent atoms fuse together into a Metastable Inner-shell Molecular State (MIMS). When the pressure is relaxed, the atoms spring back, releasing energy in the form of x-rays.
Bae stumbled on the effect at the Brookhaven National Lab in the early 1990s, when particles accelerated to high speed produced anomalous radiation. The significance of these results was not apparent at the time, but Bae did not forget them.
“In 2008, some new theoretical work inspired me to look at the Brookhaven results again,” Bae tells Popular Science. “I concluded that the anomalous signals were produced by x-rays from the decay of Metastable Innershell Molecular State generated by the nanoparticle impacts."
The numbers also revealed that a remarkable proportion of the energy was being turned into x-rays. “One surprising aspect of the discovery was that the conversion efficiency of the nanoparticle kinetic energy to photon energy was as high as 38 percent,” Bae says. Many x-ray generators convert less than 1 percent of the input power into x-rays.
Since then Bae has refined the method of generating x-rays using a tabletop apparatus to create so-called nanostars. He shoots buckyballs – tiny spheres, each made of 60 carbon atoms in a shape like a geodesic sphere – into an aluminum target at more than 60 miles a second. The impacts cause the buckyballs to crumple momentarily into a state of warm dense matter, and a large proportion of the impact energy is released as a pulse of x-rays.
The Defense Threat Reduction Agency is interested in this because the wavelength of the x-rays can be tuned to break up specific molecules such as sarin into (relatively) harmless substances. This might take the form of a compact, single-use device with power supplied by an explosive charge. As well as being a tool for engineers to deal with stockpiles in an agreed destruction process, it might also work in less co-operative situations. The DTRA already has "agent defeat" weapons with warheads to destroy weapons of mass destruction with high-temperature incendiaries, but such weapons might end up scattering the toxic remnants over a wide area. An x-ray device might be able to do the same job without any risk of spreading contamination because it would not break open chemical warheads or containers.
The technology for producing powerful x-rays from a small source is likely to have commercial uses too. A tunable, warm dense matter-driven x-ray generator could enable lithography to make a new generation of computer chips on a smaller scale than ever; it could also have medical applications such as precise radiotherapy.
“It might also be used in nuclear fusion research,” Bae says. Those short-lived nanostars might help harness the power of the sun on Earth.
Research is still in its early stages. The DTRA’s current contract with Y K Bae only covers the design of a suitable accelerator. The existing apparatus will be scaled up with help from Los Alamos National Lab. If successful, this will then be developed over the next two years and will demonstrate x-ray production using several different materials to produce different x-ray wavelengths, and researchers will investigate ways of channelling the x-rays into a narrow beam.