The color of haze
Urban pollutants work together to form the brownish particles seen over major cities the world over. Image reproduced by permission of PNNL and the Royal Society of Chemistry in PCCP 17:23312. Flying into the major airports in Mexico City, Beijing, or Los Angeles on a sunny day, you can see a lingering brown haze over the cityscape. This haze is more than an eyesore. It contains thousands of chemicals that act as a warming blanket, absorbing the sun's rays and trapping heat over the city. To deal with this haze, scientists need to understand the formation and behavior of the chemicals that form the particles. At DOE's Pacific Northwest National Laboratory, a team of scientists examined the particles that form in the atmosphere through reactions involving the pollutant toluene.
They decided to make, measure, and model the particles that belong to a broader group called brown carbon. John Shilling and Jiumeng Liu created particles by mixing the toluene with nitrogen oxides and other chemicals inside PNNL's environmental chamber. They flashed the resulting gas with light, mimicking the natural formation and aging process. www.web.ornl.gov/info/news/pulse/no451/story1.shtml Antimatter Catches a Wave at SLAC
Antimatter will surf on plasma waves in the particle colliders of the future. A study led by researchers from the DOE's SLAC National Accelerator Laboratory and the University of California, Los Angeles has demonstrated a new, efficient way to accelerate positrons, the antimatter opposites of electrons. The method may help boost the energy and shrink the size of future linear particle colliders – powerful accelerators that could be used to unravel the properties of nature’s fundamental building blocks.
The scientists had previously shown that boosting the energy of charged particles by having them “surf” a wave of ionized gas, or plasma, works well for electrons. While this method by itself could lead to smaller accelerators, electrons are only half the equation for future colliders. Now the researchers have hit another milestone by applying the technique to positrons at SLAC’s Facility for Advanced Accelerator Experimental Tests (FACET), a DOE Office of Science User Facility.
www.web.ornl.gov/info/news/pulse/no451/story2.shtml 'Molecular accordion’ drives thermoelectric behavior in promising material
Redistribution of electronic clouds causes a lattice instability and freezes the flow of heat in highly efficient tin selenide. The crystal lattice adopts a distorted state in which the chemical bonds are stretched into an accordion-like configuration, and makes an excellent thermoelectric because heat propagation is thwarted. Engines, laptops and power plants generate waste heat. Thermoelectric materials, which convert temperature gradients to electricity and vice versa, can recover some of that heat and improve energy efficiency. A team of scientists at DOE’s Oak Ridge National Laboratory explored the fundamental physics of the world’s best thermoelectric material—tin selenide—using neutron scattering and computer simulations. Their new understanding of the origin of atomic dynamics in this material, published in Nature Physics, may aid research in energy sustainability and enable the design of materials that efficiently convert heat into electricity.
“We performed the first comprehensive measurements of atomic vibrations in this important new thermoelectric material,” said senior author Olivier Delaire in ORNL’s Materials Science and Technology Division. “We discovered the origin of its very low thermal conductivity, which leads to its high efficiency.” It turns out unusual atomic vibrations help prevent “heat leaks,” maximizing the conversion into electricity.
www.web.ornl.gov/info/news/pulse/no451/story3.shtml
Profile
As a young man, A.J. Stewart "Stew" Smith won the Canadian National Lacrosse Championship as a member of a powerful Vancouver, British Columbia, club team. That early success and love of teamwork foreshadowed an illustrious career in which Smith has played leading roles as an educator, particle physicist and administrator coordinating vast, vital research efforts. Now, after nearly 50 years on the faculty and staff of Princeton University, Smith is stepping down next February from his current post as the University's first vice president for the Princeton Plasma Physics Laboratory (PPPL).
"This is a natural transition," said Smith, who turned 77 in June. "My wife is very pleased."
A search for Smith's successor, led by Pablo Debenedetti, Princeton University dean for research, is underway. www.web.ornl.gov/info/news/pulse/no451/profile.shtml
Feature
Scientists celebrate the arrival of the first neutrino beam at the MicroBooNE detector.MicroBooNE begins recording neutrinos
October is a fitting month for ghost sightings. Halloween came early for scientists of the MicroBooNE collaboration, who recorded their first neutrinos, often called ghost particles, on Oct. 15.
"It's nine years since we proposed, designed, built, assembled and commissioned this experiment," said Bonnie Fleming, MicroBooNE co-spokesperson and a professor of physics at Yale University. "That kind of investment makes seeing first neutrinos incredible."
MicroBooNE is located at DOE’s Fermi National Accelerator Laboratory. Last month, the lab's accelerator complex began delivering neutrinos to the new experiment. MicroBooNE scientists immediately began to analyze the data recorded by their particle detector to find evidence of its first neutrino interactions.
RSS