Fission and antimatter created by Lab laser

Lawrence Livermore researchers recently reported to the centennial meeting of the American Physical Society in Atlanta, Georgia, that they had used the world's most intense and powerful laser, the Petawatt, to generate a hot, short-lived fireball of energy that produced antimatter and stimulated nuclear fission in a millimeter-thick target.
Physicist Tom Cowan teamed with colleagues from the Laser Programs Directorate, National Aeronautics and Space Administration's Marshall Space Flight Center, the University of Alabama, Harvard University, and the GSI laboratory in Germany to produce the surprising results.
Cowan described the research as opening the door to the world of "photonuclear physics," in which science that once was the province of huge particle accelerators can now be approached through "a new, high-energy regime of laser-matter interactions."
The research team believes that it may be possible in the future to create ultrabright and detailed stroboscopic images of nuclear and atomic structures-and possibly even of proteins-by using powerful x rays and gamma rays created by bouncing extremely short laser pulses off oncoming streams of electrons.
Contact: Thomas Cowan (925) 422-9678 (cowan3@llnl.gov).

Using radar for the right spin

A recently tested Laboratory radar technology aims to speed up rotor-blade balance adjustment and dramatically reduce maintenance costs for U.S. Marine and Navy V-22 Osprey helicopters.
The radar device, which uses microwave impulse radar technology, was successfully tested on mock V-22 Osprey rotor blades at Bell Helicopter's Ground Test Article Facility in Arlington, Texas, in early April.
"We were able to successfully demonstrate that this system meets the U.S. Navy's requirements," said electrical engineer Tom Rosenbury, group leader of the Laboratory's Microwave Impulse Radar Program. "Now we're ready to test the radar system on a real aircraft."
The technology is expected to save up to $45 million in maintenance costs over the life cycle of each $41-million V-22 helicopter.
Placed in the wing beneath a helicopter rotor, the device emits short-duration ultrawideband pulses upward toward the rotating blades. Pulses are reflected by a small section of the blade as it passes over the radar. The transit time of pulses to and from the moving blades is measured, allowing the vertical distance to be calculated with great accuracy. If the rotor blades are not tracking within a required tolerance band, rebalancing may be necessary to prevent damage to the rotor or excessive transmission vibration.
Contact: Tom Rosenbury (925) 423-7510 (rosenbury1@llnl.gov).

Small-scale fusion with big promise

A team of researchers at Lawrence Livermore has created tiny fusion explosions with a compact laser in experiments that could lead to new methods for detecting hidden flaws in materials.
Using a laser so compact that it could fit on a large table, the researchers, led by physicist Todd Ditmire, blasted deuterium (heavy hydrogen) gas generated in a vacuum chamber with flashes of high-intensity laser light. These experiments produce fusion reactions similar to but much smaller than the explosions of hydrogen bombs or in the sun.
According to Ditmire, the experiments offer no path toward the long-sought goal of creating an inexhaustible supply of fusion energy, nor are they related to the sensational and widely discredited cold fusion claims made a decade ago by Utah chemists.
Instead, the experiments are basic physics research into how short, intense pulses of light interact with small clusters of atoms and cause the clusters to collide against each other randomly. The clusters are transformed into highly compressed, superheated exploding balls of electrically charged gas that emit clouds of subatomic particles called neutrons.
The goal of the research, Ditmire says, is to devise ways of increasing the yield of the fusion neutrons so that the particles can be used as probes, much as x rays are, to investigate defects in materials ranging from metals to human tissue.
Contact: Todd Ditmire (925) 422-1349 (ditmire1@llnl.gov).

Squeezing a gas into a solid

In a recent issue of Science magazine, Livermore researchers report that they have transformed carbon dioxide into a polymeric solid with a structure like that of quartz by squeezing it at high temperatures and pressures.
Physical chemist Choong-Shik Yoo, leader of a high-pressure physics group at the Laboratory, and his colleagues synthesized the new extended-solid phase by heating carbon dioxide in a diamond anvil cell with a laser to temperatures above 1,800 kelvins and pressures above 40 gigapascals (400,000 times atmospheric pressure).
Spectrographic analysis indicates that each carbon atom is bonded to four oxygen atoms, yielding a three-dimensional network like that of the quartz polymorph of silicon dioxide. Once formed, the quartzlike carbon dioxide remains stable at room temperature and pressures above 1 gigapascal.
The researchers hope to isolate the new material soon at ambient pressures. Its thermal conductivity is expected to be "very high, just like diamond's," says Yoo, noting that it is also "a good candidate for a superhard material."
Contact: Choong-Shik Yoo (925) 422-5848 (yoo1@llnl.gov).
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