New pint sized particle accelerator leads the way to clean nuclear energy

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The EMMA ring in relation to the main ERLP (ALICE) accelerator.

(PhysOrg.com) -- Researchers at Daresbury science park in Britain have offered a glimpse into what might be the future of nuclear energy production by showcasing a scaled down particle accelerator; one, that when combined with others just like it, could produce nuclear energy based on thorium, rather than uranium. Dubbed the Electron Machine with Many Applications (EMMA), the accelerator, a much smaller version of the kind used in physics research, such as the Large Hadron Collider, could be used to provide an accelerated beam necessary for the type of nuclear reaction used in a theoretical thorium plant.

Thorium, named for the Norse god of thunder, is a silver-white metal found in abundance all over the planet, and is only very slightly radioactive and as such is a member of the elements known as actinides which, like uranium, occasionally spin off particles which make it useful for energy production. But unlike uranium, thorium is relatively clean because it decays much faster leaving far less reactive byproducts behind; and because it requires a constant bombardment of particles to keep it reacting, is incapable of producing a meltdown; something on the minds of people in the aftermath the Fukushima disaster.

That?s where EMMA enters the picture. To produce the constant stream of particles needed to keep a thorium reaction going, an accelerator is needed, but it wouldn?t have to be the huge billion dollar kind, more like the kind you could fit in your garage, or in this case in a lab on the boggy Cheshire flatland, just east of Liverpool, where reporters from the U.K. newspaper Mail, were recently given a tour. They report that EMMA is ?an object of scientific beauty...?

Scientists have known since the 1950?s that thorium could be used to produce electricity, just as uranium is today; what kept them from doing so was the desire to use technology that could be used in conjunction with atomic weapons, which pushed thorium research aside due to its impracticality for such applications. Today however, things have obviously changed, several countries besides Britain are taking a very hard look at thorium and the ways it could be put to good use and at small particle accelerators too; the team in Britain is also currently at work designing the Particle Accelerator for Medical Applications (Pamela) to be used to help treat hard to reach cancer in patients.

2010 PhysOrg.com

Turning the heat on organizing energy

(PhysOrg.com) -- Conventional wisdom suggests that when exposing a crystal to heat, the thermal energy within the crystal would spread uniformly across the lattice.

However, physicists have found that unlike the surface of water disturbed by a rock where energy spreads out in ripples, energy in a crystal can spontaneously localize in distinct nonlinear modes. Not only that, but now Lawrence Livermore scientists report that this energy found in intrinsic localized modes (ILMs) as they are called, also can organize into complex and changing dynamical patterns when heated to between 614 and 636 kelvin (water boils at 373 kelvin).

The scientific community expected that ILMs formed randomly throughout a crystal. But the new research by LLNL's Michael Manley and collaborators from Oak Ridge National Laboratory and Cornell University found that ILMs organize into complex and changing patterns.

Using scattering neutrons to probe a sodium iodide crystal, Manley and colleagues found that between 614 and 636 kelvin, the ILMs began switching as a unit from one pattern to another and then would return to their original organization as the crystal was subjected to further heating.

"Although dynamical patterns like this have been known for more than 100 years, this is the first observation in an atomic lattice and the first in thermal equilibrium," Manley said. "It was a big surprise that energy organized in equilibrium. It goes outside of how we treat equilibrium."

ILMs may play an important role in advanced photonic switching devices; energy transport and storage processes in biopolymers; "unzipping" of DNA; and folding of proteins.

"This new understanding is of practical importance since it occurs in ordinary crystals at temperatures where materials are used," Manley said. "It may be of special importance in applications where the flow of thermal energy is critical, such as with thermoelectric materials."

The research appears in the June 14 issue of the new journal, Scientific Reports (Nature's open access journal). The paper can be accessed for free on the Web.

Provided by Lawrence Livermore National Laboratory (news : web)

Startling thermal energy behavior revealed by neutron scattering

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Data from ARCS show that, with a small increase in temperature, a new feature in the scattering from NaI appears, indicating that localized energy modes (ILMs) are present. The wide coverage of the instrument allowed the interaction of these new modes with other atomic vibrations to be studied, revealing the novel dynamical nature of the patterns within the unchanged crystal structure.

(PhysOrg.com) -- A discovery by researchers working at the Spallation Neutron Source upends long held assumptions about the microscopic behavior of materials in an equilibrium condition. The findings could influence further research in advanced materials, communication and optical systems, and thermoelectric materials that use differences in temperature to produce electricity.

The researchers at the Oak Ridge National Laboratory neutron science facility found that the thermal energy in a crystal at thermal equilibrium (i.e., a state in which the thermal energy is uniformly distributed across the crystal structure) organizes itself into dynamical patterns that are not associated with corresponding changes in the structure of the crystal.

This is the first observation of dynamical patterns of ILMs in a material in thermal equilibrium and the first in an atomic lattice. The new results "extend the notion of complex energy self-organization to equilibrium processes and down to the scale of atoms," noted principal investigator Mike Manley of Lawrence Livermore National Laboratory.

Beyond the contribution to theory, the insights are of great practical importance because they appeared under conditions ordinary in the world of material applications, he said. "It's a fundamental new understanding of properties occurring at the temperatures at which we use materials."

Scientific Reports, a new online publication from Nature Publishing Group, published the findings in its June 14 issue (available with open access at http://www.nature. … ep00004.html). The experiments were conducted on ARCS, the Wide Angular-Range Chopper Spectrometer at the SNS. Research team members are from Lawrence Livermore and Oak Ridge national labs and Cornell University.

The thermal energy in an ordinary crystal exists mainly in the form of tiny atomic vibrations that ripple in waves through the material. It might seem that in a crystal at equilibrium, these waves would emanate symmetrically and uniformly in all directions, much as ripples spread from a stone thrown into a calm pool. But physicists have realized for decades that some thermal energy in a material can actually collect in discrete packets, called intrinsic localized modes (ILMs) that break the symmetry of the crystal.

Scientists have assumed that ILMs formed randomly throughout a crystal in equilibrium. However, as the researchers analyzed their ARCS data, they realized that the ILMs were emerging according to a regular pattern, said Manley. At temperatures between 614 and 636 K, the ILMs in the crystal began switching as a unit back and forth between one pattern and another. Then as the temperature of the sample rose beyond 636 K, they returned to their original pattern. "This pattern isn't something we would have tried to look for specifically, because we didn't expect it. But as we were piecing together the data, we saw the whole pattern and we saw that the ILMs weren't random, Manley said."

Another surprise was that the crystal structure didn't change along with the dynamics as the ILMs organized: the ILMs organized themselves in complex, shifting dynamical patterns even as the crystal lattice remained unchanged. Localized packets of energy in the crystal had decoupled from the rest of the lattice and were vibrating differently from it.

"If you look at the crystal structure, you see nothing happening. It's unchanged. But if you could stick your head inside the crystal, at the atomic scale, you would see every third atom moving in a way that's different from the two atoms next to them," said Manley. "We assume atoms that are identical all vibrate the same way. But this experiment showed some of the atoms vibrating differently although they're not structurally different," he said. Such behavior of self-organizing energy is common in nature, he said, but only in nonequilibrium situations in which some force is driving energy across a system?for example, cloud formation and whirlpools driven by convective energy flow.

The research team went into the experiment expecting to find ILMs in NaI, Manley said. They thought ILMs would appear smoothly with increasing temperature. But instead, the ILMs seemed to fade out at a certain temperature and then reappear at another temperature. The capabilities of SNS and ARCS made it possible to collect the fine detail needed to resolve what the scientists were seeing, he noted. "We looked at it with a new tool that could really see in detail and get a much more complete view in reciprocal space, in four dimensions?the three spatial directions plus frequency?and we saw this pattern. We wouldn't have been able to see the pattern if SNS and ARCS hadn't been available. We never could have collected that much data at all those temperatures otherwise. SNS gave us the capability to see the whole thing."

Manley said he wants to pursue the research in other materials and under a broader range of conditions. Other ordered states of energy may occur outside the fairly narrow range of temperatures the ARCs experiment explored, and new patterns may emerge. Practical applications often arise from the type of complexity the experiment revealed. "This will change our perspective; it will lead to applications; it will inform theory," he said.

Provided by Oak Ridge National Laboratory (news : web)

Packing the ions: Discovery boosts supercapacitor energy storage

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Computational modeling of carbon supercapacitors with the effects of surface curvature included. Credit: Jingsong Huang, ORNL

Flat is in the eye of the beholder. When you're talking about nanomaterials, however, that eye is pretty much useless unless it's looking through an electron microscope or at a computer visualization. Yet the pits and ridges on a seemingly flat surface -- so small they are invisible without such tools -- can give the material astonishing abilities. The trick for researchers interested in taking advantage of these abilities lies in understanding and, eventually, predicting how the microscopic topography of a surface can translate into transformative technologies.

Drexel University's Yury Gogotsi and colleagues recently needed an atom's-eye view of a promising supercapacitor material to sort out experimental results that were exciting but appeared illogical. That view was provided by a research team led by Oak Ridge National Laboratory (ORNL) computational chemists Bobby Sumpter and Jingsong Huang and computational physicist Vincent Meunier.

Gogotsi's team discovered you can increase the energy stored in a carbon supercapacitor dramatically by shrinking pores in the material to a seemingly impossible size?seemingly impossible because the pores were smaller than the solvent-covered electric charge-carriers that were supposed to fit within them. The team published its findings in the journal Science.

The mystery was not simply academic. Capacitors are an important technology that provides energy by holding an electrical charge. They have several advantages over traditional batteries?charging and discharging nearly instantaneously and recharging over and over again, almost indefinitely, without wearing out?but they also have drawbacks?most importantly, they hold far less energy.

An electric double-layer capacitor, or supercapacitor, represents an advance on the technology that allows for far greater energy density. While in traditional capacitors two metallic plates are separated by a nonconducting material known as a dielectric, in a supercapacitor an electrolyte is able to form an electric double layer with electrode materials that have very high surface areas.

As such, supercapacitors are able to achieve the same effect within a single material, as properties of the material divide it into separate layers with a very thin, nonconducting boundary. Because they can both forgo a bulky dielectric layer and make use of the carbon's nanoscale pores, supercapacitors are able to store far more energy than their traditional counterparts in a given volume. This technology could help increase the value of energy sources that are clean, but sporadic, meting out stored energy during downtimes such as night for a solar cell or calm days for a wind turbine.

So Gogotsi's discovery was potentially ground breaking. The energy was stored in the form of ions within an electrolyte, with the ions surrounded by shells of solvent molecules and packed on the surfaces of nanoporous carbons. The researchers were able to control the size of pores in the carbon material, making them 0.7 to 2.7 nanometers. What they found was that the energy stored in the material shot up dramatically as the pores became smaller than a nanometer, even though the ions in their solvation shells could not fit into spaces that small.

"It was a mystery," Sumpter said. "Many people questioned the result at the time. Yet the experimental data was showing an incredible increase in capacitance."

Fortunately, it was a mystery that the ORNL team could unravel.

"We thought this was a perfect case for computational modeling because we could certainly simulate nanometer-sized pores," Sumpter said. "We had electronic-structure capabilities that could treat it well, so it was a very good problem for us to explore."

Using ORNL's Jaguar and Eugene supercomputers, Sumpter and his team were able to take a nanoscale look at the interaction between ion and carbon surface. A computational technique known as density functional theory allowed them to show that the phenomenon observed by Gogotsi was far from impossible. In fact, they found that the ion fairly easily pops out of its solvation shell and fits into the nanoscale pore.

"It goes in such a way that it desolvates in the bulk to get inside because there's electrostatic potential and van der Waals forces that pull it in," Sumpter explained. "There are a whole lot of different forces involved, but in fact it's very easy for it to get in."

The ORNL team and colleagues at Clemson University, Drexel University, and Georgia Tech detailed their findings in a series of publications, including Angewandte Chemie, Chemistry-A European Journal, ACS Nano, Journal of Chemical Physics C, Physical Chemistry Chemical Physics, Journal of Materials Research, and Nano Letters.

"In addition," Sumpter noted, "the microscopic bumps and divots on a carbon plate make a dramatic difference in the amount of energy that can be stored on or in it.

"When you get to the nanoscale, the surface area is huge, and the curvature, both concave and convex, can be very large. This makes a large difference in the capacitance. We derived a model that explained all the experimental data. You can back out the pieces of the model from the electronic structure calculations, and from that model you can predict capacitance for different types of curved shapes and pore sizes."

For example, he said, the calculations showed that the charge-carrying ions are stored not only by slipping into pores but also attaching to mounds in the material.

"It's a positive curvature instead of a negative curvature," Sumpter said, "and they can store and release energy even faster. So you can store ions inside a hole or you can store ions outside."

Using these and other insights gained through supercomputer simulation, the ORNL team partnered with colleagues at Rice University to develop a working supercapacitor that uses atom-thick sheets of carbon materials.

"It uses graphene on a substrate and a polymer-gel electrolyte," Sumpter explained, "so that you produce a device that is fully transparent and flexible. You can wrap it around your finger, but it's still an energy storage device. So we've gone all the way from modeling electrons to making a functional device that you can hold in your hand."