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Lawrence Livermore National Laboratory
Seeking Supernovas or Black Holes in the Bay Area?
Try the National Ignition Facility
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National Ignition Facility (NIF) may seem like an odd name for a national treasure.
Centered on a Laser Building the size of Yankee Stadium at the Lawrence Livermore
National Laboratory in California, its primary purpose is to conduct nuclear research and testing using the world’s most powerful laser – 60 times more powerful than the second most powerful laser system. It is now more than 80 percent complete and should be fully operational in mid-2009.
The NIF is in many ways the culmination of the 30-year partnership between SCHOTT and the Lawrence Livermore National Laboratory. Those ties were summed up by NIF
physical chemist Jack Campbell: “The lab approaches SCHOTT and says we’re going to build this laser. We need this glass, which you don’t have and we’ll help you invent. That glass is made in a process that doesn’t exist yet and we’ll help you develop that. And then when it’s done, it needs to be measured and inspected and if you need any special tools for that we’ll either buy them or make them ourselves and give them to you. And then we contract with SCHOTT and begin.”
That process has gone on for three decades, on a progressively larger scale. As Campbell recalls, “Up until the recent laser, the amount of glass we brought was not that much – a few hundred pounds and we’d buy a few hundred pieces. And when we first started out, we’d buy pieces of glass about the size of saucer – for a coffee cup.”
Those early pieces included the PH4 BK7 glass for the Labs’ Swiva project in the 1970s. In the 1980s, LG750 platinum free phosphate laser glass was developed for the Novette and Nova Laser projects. In the 1990s came the change in form, from conventional spherical lenses – the coffee cups – to the LG770 Phosphate Laser glass for the NIF Beamlet Project. Now the glass was produced in rectangular slabs 745 mm by 425 mm and 45 mm thick.
For the Laser Building complex, the glass requirements had moved a long way from saucer stage. “The slabs got larger to the point where we were buying pieces the size of a coffee table,” Campbell recalls. And this time, the NIF needed not hundreds, but thousands of pounds of glass for nearly 10,000 slabs. If laid end to end, the laser glass alone would run for five miles.
It would have been possible to build such an immense laser facility using standard industrial techniques, but it would take far longer than planned. For example, the specialized glass once had to be produced in a batch process, yielding, at most, three slabs of glass a week in what Campbell calls the “bake the cake process.” But NIF was taking laser glass demand to a new level, requiring a minimum of thousands of meter long, 0.5 meter wide and 4 centimeter thick slabs. At the baking the cake rate, production of the glass in the quantities needed would take about 20 years.
NIF scientists, together with SCHOTT Advanced Optics, developed a whole new way to make laser glass by a Continuous Laser Glass Melting process, which not only speeds up production twenty-fold and cuts costs by 80 percent but also produces even higher quality glass.
“SCHOTT did the machine and design engineering and came up with all the chemicals we’d have to buy,” Campbell explains. “Livermore bought the equipment they needed and they built a plant with all this Livermore-furnished equipment. This had never been done before at this scale. We didn’t know if it would work – you have to have a lot of patience with your partner and yourself, and there are some pretty bleak times. It took about four or five years to develop the process and build the plant until it was ready to go. The first couple of runs were really disasters but we persisted. When you have partners who work with each other and trust each other, you can get through it.”
Working with a knowledgeable partner not only makes tangled technical ways straight, but can save money as well. One major element SCHOTT would need was platinum – a ton of platinum. With platinum at $1,000 an ounce, that single item would have cost $25 million.
“SCHOTT noted that if we have to lease the metal, it’ll cost a fortune,” Campbell recalls, “so you ought to see if you can borrow it from the government. After all, the United States has a large stockpile. It was a very wise idea, and saved the taxpayers a lot of money. We approached the government and they lent us one metric ton of platinum from the strategic metal stockpile. We’ve returned it and paid for the minor amounts we lost in the production process.”
In the pilot test of the system, at the SCHOTT plant in Duryea, PA., 200 glass slabs – 5 percent of the total needed – were produced and technical specifications were met.
Beyond the NIF facility, the process is producing laser glass for the French Laser
Megajoule system. It is also being adapted to the production of other kinds of specialized optical glass with industrial and even consumer applications, including precision optical instruments and cameras.
For his part in the development of higher quality optics and the means to produce them
economically Campbell was recognized with an honor from the American Ceramic
Society.
Five other critical technical breakthroughs have been required for the NIF. Four have already been achieved, including large-aperture optical switches, stable high-gain preamplifiers, servo-controlled large aperture deformable mirrors and large, rapid-growth frequency-conversion crystals. The developments are not only advancing the state of the art, but also speeding the work at hand. NIF produced the world’s largest rapid-growth crystal, weighing 701 pounds, in a mere two months. Formerly, it would have taken two years.
And waiting the wings for SCHOTT and Lawrence Livermore National Laboratory is the
next great technical challenge.
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Contact
Advanced Optics
SCHOTT AG
Hattenbergstrasse 10 55122 Mainz Germany
 | +49 (0)6131/66-1812 |
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