Glass vendors for the Lawrence Livermore National Laboratory (LLNL; Livermore, CA) National Ignition Facility (NIF) have achieved a major milestone and addressed one of the key technological questions that plagued the NIF when scheduling and cost overruns were reported last September. On April 1, LLNL announced that Schott Glass (Duryea, PA) had successfully demonstrated a continuous-melt process to enable production of economical, high-optical quality, neodymium-doped phosphate laser glass for the NIF.
Hoya Corp. (Fremont, CA), the second of two NIF laser glass vendors, is scheduled to begin a similar process next month. More than 3500 laser glass slabs will be needed for the NIF, and a similar quantity will be needed for the Laser Megajoule to be constructed later in this decade by the French Commissariat a L'Energie Atomique (CEA; Grenoble, France). Each slab measures about 80 x 45 x 4 cm and weighs about 100 lb. Schott had produced 250 of the slabs by the beginning of April using the continuous-melt process, which is 20 times faster than the previous one-slab-at-a-time batch melting technology.
"This is a truly significant achievement," said NIF project manager Ed Moses. "Obtaining quality glass was one of the top technological and manufacturing issues our project faced. This achievement demonstrates that NIF's remaining technical challenges are rapidly being solved." Late last summer, NIF management came under US Department of Energy scrutiny because of a reported $300-million cost overrun and a schedule delay of at least one year. Technological concerns raised by unofficial sources included target fabrication, diagnostics, and glass development and delivery. Both NIF glass vendors had demonstrated last year that continuous glass melt was possible, but at the time they were unable to achieve all of the project specifications.