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By Michael Lucibella
Photo courtesy of Lawrence Livermore National Laboratory
Brighter days ahead — outside researchers will get more time at one of the largest laser facilities in the world.
Recent changes at the nation’s top large laser facility are making it easier for scientists to do basic research there. Though still primarily focused on fusion and nuclear weapons research, the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory is becoming more of a user facility.
“There’s been a real sea change at NIF for the better in terms of the fundamental science program,” said Don Lamb, chair of the NIF users group. “It’s a transformation of what NIF can do for the scientific community.”
Completed in 2009, NIF’s primary missions are to simulate nuclear weapon detonations as part of the Department of Energy’s (DOE) “Stockpile Stewardship” program and to develop laser fusion to generate electricity. NIF concentrates 192 powerful lasers onto a 0.5 cm diameter pellet of hydrogen, compressing it and igniting nuclear fusion reactions. The energy program’s ultimate goal is to get more energy output from the process than input.
“Ignition is only part of what NIF was built for and what it is actually doing,” said Jon Eggert, a researcher at Livermore. “There’s actually a fairly large contingent of people that want to do fundamental science on NIF.”
While its dual primary missions take up about 90 percent of the facility’s laser blasts, or “shots,” the thin slot for other fundamental science is enlarging. New scheduling policies will give independent researchers more time and shots on the machine.
“The real issue has been that for many years there were virtually no shots allocated to the fundamental science program,” Lamb said. “This went along with an incredible single-minded focus pursuing ignition through a single path.”
Before the facility was completed, the DOE put out a call for proposals to do fundamental science at the facility. A number of researchers responded, and the NIF offices assigned nine teams their own shots at the laser facility.
Parceling out a set number of shots, however, rather than blocks of time as at other user facilities, brought about backups and delays at the lab. Experiments that weren’t ready by their scheduled shot day would keep tying up the machine until they were ready, delaying other experiments. This slipping schedule made it difficult for scientists and graduate students to plan their trips to Livermore in advance.
In addition, there weren’t many fundamental science shots to start with. In 2009 there were two shots allotted to fundamental science. The next year there was one. The numbers slowly started to increase. There were four fundamental science shots in both 2011 and 2012 and seven in 2013. This year is slated to have eight shots. Researchers originally hoped for more, but budget cuts from the US government’s funding sequestration cut the total number of shots for all experiments.
“We just haven’t had enough shots to [accommodate] all of those teams,” said Chris Keane, the director of the NIF user office at Livermore. “We are looking at issuing a new call soon.”
For the new lineup of experiments, the NIF leadership is revamping the scheduling system. Research teams will be able to apply for a set number of days at the NIF and can shoot the lasers as much or as little as they need to during that time.
“Because it’s shot days, if you’re not ready, they won’t wait for you,” Lamb said. “That’s going to help not only the NIF be efficient.... It’s also going to help, I think, the academic experimental groups.”
The lab is also working to increase the total number of shots for all types of science. In 2013 there were a total of 209 laser shots. Because of sequestration, the number for 2014 is down to about 150, but lab administrators are hoping to have between 250 and 300 shots in 2015, and about 300 in 2016. Right now administrators are scheduling experiments for the spring of 2015.
The changes came about in part from a recent study mandated by the Senate Appropriations Committee to find ways to increase the number of shots and overall science output at the machine.
In addition, recent leadership changes at Livermore put people in positions to build up the fundamental science at the NIF. The lab’s new director, William Goldstein, has been widely credited for advocating for fundamental science at NIF since its inception. Similarly, Jeff Atherton was named head of NIF in May of 2013 and is also seen as a strong proponent of basic research.
“Jeff is very transparent and open about issues we have to overcome,” Lamb said. “He’s doing everything he can to increase the science being done at the NIF.”
There are other laser facilities across the country that can do similar experiments at lower energy. The Jupiter Laser Facility at Livermore and the Omega Laser at the University of Rochester are essentially older, smaller versions of the NIF that do laser compression science.
“[NIF] is just a totally new regime,” Keane said. “It’s the energy, but it’s also the precision and the reproducibility.” Experiments at NIF have probed the phases of hydrogen at high densities, how stars form in the Eagle Nebula, and how hydrodynamic instabilities affect supernovas. There have also been about 60 “ride-along” shots that take data during a dedicated fusion energy or stockpile stewardship shot (mostly nuclear cross-section experiments).
Jon Eggert uses the lasers at the NIF to explore the properties of matter at the center of gas giant planets. Astronomers have discovered hundreds of confirmed exoplanets, but no one knows what molecular and material structures are at the core of the largest planets.
“If we want to answer those sorts of questions, we actually have to know what’s happening on the inside of those planets,” Eggert said. “To do that we need to have experiments.”
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