Lab breaks own crystal-growing record
Lawrence Livermore researchers have produced the world's largest fast-growth crystal. Weighing 318 kilograms, the crystal bests the previous record of 295 kilograms, also achieved at Livermore using a variant of the rapid-growth crystal-growing technique developed at the Laboratory.
The pyramid-shaped KDP (potassium dihydrogen phosphate) crystal measures approximately 66 by 53 by 58 centimeters. It was grown in a record 52 days using the special Livermore technique, which delivered twice the yield originally projected.
The enormous crystal will be sliced into thin plates for use in the National Ignition Facility (NIF) currently under construction at the Laboratory. The crystal plates will be used to convert the laser's infrared light beams into ultraviolet light just before the beams strike laser targets. NIF will require as many as 600 crystal plates.
According to Ruth Hawley-Fedder, leader of the Livermore crystal-growing team, the latest rapid-growth technique "offers the possibility of producing even larger and higher quality crystals in the future. Our newest record-holder could have grown even larger, but we simply ran out of room in our growth tank."
Alan Burnham, deputy systems manager for NIF's final optics, notes, "Ruth and her team brought large-scale rapid-growth technology to the reliability needed to realize savings of millions of dollars for both construction and later operation of NIF."
Contact: Ruth Hawley-Fedder, (925) 422-6328 (hawleyfedder1@llnl.gov).
Lab technology images Neptune, Titan clearly
A research team led by Livermore's Claire Max recently used Hawaii's Keck II telescope to capture the clearest Earth-based images ever taken of Titan (Saturn's largest moon) and Neptune. Max's team, made up of scientists from Lawrence Livermore, the University of California at Berkeley and Los Angeles, and the Keck Observatory, revealed their successes at the annual meeting of the American Astronomical Society in Atlanta, Georgia, in mid-January.
The unprecedentedly clear images of the distant celestial bodies were captured in infrared light. They are among the first taken after Livermore researchers helped install adaptive optics technology, developed at Livermore, on Keck II, one of the twin telescopes that are the world's largest. Adaptive optics uses rapid mirror adjustments to remove Earth's atmospheric turbulence from what the telescope sees.
The images, which surpass even those possible using the Hubble Space Telescope, reveal giant Neptunian storms driven by prevailing winds of 1,800 kilometers per hour. Scientists are using information provided by the telescope to study the planet's storms and their evolution, a first step toward understanding Neptune's weather and climate.
The adaptive optics images of Titan reveal features that could be frozen land masses separated by cold hydrocarbon seas and lakes. They tell astronomers about the complex surface composition of the frigid Saturnine moon. Sunlight shining on Titan's nitrogen-rich atmosphere produces a deep orange haze that obscures Titan's surface. Keck's infrared detectors penetrate this haze to reveal surface details.
"Combining the power of Keck with adaptive optics is taking us to new worlds," says Max. "That's an extremely exciting prospect as we enter the next millennium."
Contact: Claire Max (925) 422-5442 (max1@llnl.gov).
Researchers' theory tracks absorbed CO2
In the January 2000 issue of Science, Laboratory climate scientists Kenneth Caldeira and Philip Duffy posit their solution to an old scientific mystery. Early computer models showed that large amounts of carbon dioxide (CO2) from human activity are readily absorbed by the icy waters of the Antarctic (or Southern) Ocean south of Australia. These models are consistent with the general rule that colder water absorbs CO2 more easily than warm water. Yet, sampling reveals that the Antarctic Ocean does not contain massive CO2 reserves.
Caldeira and Duffy's study suggests not that the models are wrong but that the cold, CO2-containing water moves deeper and deeper as it runs north from the point of absorption at 60°ree; south latitude to the tropics (40°ree; south latitude), explaining why the carbon is found so deep in the subtropical ocean. Furthermore, the warmer layers of water in the subtropical ocean push down on the colder, denser water layers, keeping them and the carbon they contain deep in the subtropical waters.
A problem arises as humans generate more CO2. As the ocean absorbs more and more carbon dioxide, it becomes more acidic and therefore perhaps less efficient at carbon absorption. Not only is acid corrosive to calcium carbonate, an essential ingredient of shells and coral reefs, but acidity warms water, inhibiting its ability to absorb CO2.
"The fear is that if you warm things up too much, more precipitation will make the surface of the Southern Ocean less dense," says Caldeira. "You may start shutting off the entrance of carbon dioxide into the ocean, and things would warm up a lot faster."
Contact: Kenneth Caldeira (925) 423-4191 (caldeira2@llnl.gov).
Back to April 2000