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The Laboratory
in the News

Machine detects explosives, chemicals, and bioagents
New research by a team of Livermore scientists has expanded the capability of the Single-Particle Aerosol Mass Spectrometry (SPAMS) system to detect explosives as well as chemical and biological agents. The three-in-one machine has been conceptually proven to detect minuscule particles of explosives, weighing one trillionth of a gram, on clothing or baggage. This latest advance is described in the March 1, 2007, edition of Analytical Chemistry.
The research expands the capabilities of SPAMS to include several types of explosives that have been used worldwide in improvised explosive devices and other terrorist attacks. “SPAMS is a potential option for airport and baggage screening,” says George Farquar, a postdoctoral fellow and physical chemist at the Glenn T. Seaborg Institute in the Chemistry, Materials, and Life Sciences Directorate. “The ability of the SPAMS technology to determine the identity of a single particle could be a valuable asset when the substance is dangerous in small quantities or has no legal reason for being present in an environment.”
Future plans for SPAMS include field testing at a large public facility in the U.S. later this year, upgrading the technology for removing particles from luggage and clothing, and adding the capability to detect narcotics. Research funds have been provided by the Defense Advanced Research Projects Agency, the U.S. Department of Homeland Security, and the Glenn T. Seaborg Institute.
Contact: George Farquar (925) 424-4275 (gfarquar@llnl.gov).

To catch an exploding dwarf star
A University of Chicago team’s groundbreaking simulation of a white dwarf star exploding—the first complete three-dimensional (3D) simulation of a type 1a supernova—was made possible with computing support from Livermore’s Advanced Simulation and Computing (ASC) Program. The success of the simulation has broad implications for the role of type 1a supernovae as distance markers for cosmology, according to Stephen Libby, a Livermore physicist who has served as a liaison with the Chicago team. Libby says, “Simulating a full 3D detonation is a remarkable achievement.”
By better understanding how a type 1a supernova explodes, astrophysicists hope to gain insight into the mystery of dark energy, an unknown force pushing apart the cosmos that accounts for two-thirds of the aggregate energy in the universe. Scientists use Type 1a supernovae as “standardized candles” to determine the distance and acceleration of distant galaxies and thus want to measure their output accurately. In addition, understanding the physics of thermonuclear burn, such as that in supernovae, is of great interest to the National Nuclear Security Administration (NNSA), which is responsible for ensuring the safety, security, and reliability of the nation’s nuclear stockpile in the absence of underground nuclear testing.
The 3D simulation was conducted by a team at the University of Chicago’s Center for Astrophysical Thermonuclear Flashes with the assistance of Laboratory computer scientists from NNSA’s ASC Program. Dona Crawford, associate director for Livermore’s Computation Directorate, says, “Laboratory computer scientists worked assiduously behind the scenes to ensure that the code ran smoothly over the long hours required for this complex simulation.” University of Chicago scientists discussed the breakthrough simulation at the Paths to Exploding Stars Conference in Santa Barbara, California, March 22, 2007.
Contact: Dona Crawford (925) 422-1985 (crawford13@llnl.gov) or Stephen B. Libby (925) 422-9785 (libby1@llnl.gov).

A step closer to imaging biological molecules
Livermore researchers have confirmed a key factor in imaging biological molecules at atomic resolution. Using ultrashort photon pulses from an x-ray free-electron laser, the researchers probed new regimes of laser–solid interactions. They found that there are no induced structural changes to irradiated samples at a nearly atomic scale (0.3 nanometer) over the time of the laser pulse. A nanometer is 100,000 times smaller than a human hair. The Livermore team, led by Stefan Hau-Riege of the Physics and Advanced Technologies Directorate, found that the structural change of materials is limited by the inertia of the atoms.
The experiment demonstrated that with intense ultrafast pulses, structural damage does not occur during the pulse, giving credence to the concept of diffraction imaging of single macromolecules. These new results are a prerequisite for imaging biological molecules at atomic resolution. The Livermore team identified the limits for imaging biological materials at the Department of Energy’s Linac Coherent Light Source, which is scheduled to begin operation in 2009.
The work was performed on the x-ray free-electron laser FLASH at Deutsches Elektronen-Synchrotron in Hamburg, Germany. Other Livermore researchers include Henry Chapman, Saša Bajt, Richard London, Eberhard Spiller, Sherry Baker, and Richard Bionta. The research appeared in the April 4, 2007, issue of Physical Review Letters.
Contact: Stefan Hau-Riege (925) 422-5892 (hauriege1@llnl.gov).

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UCRL-52000-07-6 | June 12, 2007