NATIONAL IGNITION FACILITY AND GLASS VENDORS ACHIEVE CONTINUOUS MELT MILESTONE

Editor Note: Photos of the new continuous meltingtechnology are available on the Internet at http://www.llnl.gov/PAO/Newsstand/articles/3-31-00-laserglass.html

LIVERMORE, CA - A major laser glass milestone has been achievedfor Lawrence Livermore National Laboratory's National IgnitionFacility - thanks to extensive research and development spearheadedby the Lab and two leading high technology glass vendors.

Schott Glass Technologies, based in Duryea, Pennsylvania, hassuccessfully demonstrated a process to ensure continuous productionof economical, high-optical quality, neodymium-doped, phosphate laserglass needed for the National Ignition Facility. Schott is one of twoNIF laser glass vendors working on the process. The second vendor,Hoya Corporation, based in Fremont, California, is scheduled to beginsimilar glass melting operations early next month.

To date, Schott has produced more than 250 of the roughlymeter-sized glass slabs needed for NIF's demanding opticalspecifications. In addition, the glass has been produced at a rate 20times faster than could be achieved using the existing one-slab-at-a-time batch melting technology.

"This is truly a significant achievement," said Ed Moses, projectmanager of the National Ignition Facility. "Obtaining quality glasswas one of the top technological and manufacturing issues our projectfaced. This achievement demonstrates that NIF's remaining technicalchallenges are rapidly being solved."

More than 3500 laser glass slabs will be needed for the NationalIgnition Facility. Each slab is about 80 centimeters long, 45centimeters wide, four centimeters thick and weighs approximately 100pounds. If placed end to end, the 3500 slabs would extend nearly twomiles and in total, would weigh more than 150 tons.

The costs for the development of the continuous melting processhas been shared equally between LLNL and the French Commissariat aL'Energie Atomique (CEA). The CEA plans to purchase a similarquantity of slabs for their Laser Megajoule that will beginconstruction later this decade.

While initial attempts by Schott and Hoya in 1999 demonstratedthat continuous melts could occur, certain glass specifications werenot achieved at that time. In particular, the glass product containedtrace quantities of hydroxyl group contamination that originated fromsmall amounts of moisture in the surrounding air and in the initialglass raw materials. Attempts to remove the moisture-derivedcontamination in the glass degraded the other glass properties. Butover the past six months, LLNL, Schott and Hoya have carried outcooperative research specifically aimed at moisture contamination.Schott's currently melting campaign is the first successfuldemonstration of this research and improved technology. Both vendorswill begin production campaigns using this technology in early2001.

The National Ignition Facility, currently under construction atLawrence Livermore National Lab, is one of the cornerstones of theDepartment of Energy's Stockpile Stewardship Program. NIF will usethe world's largest laser to heat fusion fuel to thermo-nuclearignition. The experiments will help scientists sustain confidence inthe nuclear weapons stockpile without actual testing. NIF will alsoproduce additional benefits in basic science and fusion energy.

Founded in 1952, Lawrence Livermore National Laboratory is anational security laboratory, with a mission to ensure nationalsecurity and apply science and technology to the important issues ofour time. Lawrence Livermore National Laboratory is managed by theUniversity of California for the U.S. Department of Energy.