NIF conducts public tours for more than 5,000 visitors every year, ranging from members of Congress and high-ranking military officers to middle-school students. When tour guides escort visitors through the world’s largest laser system, they can count on hearing at least a few “Wow!”s from the group—especially when they reach the 10-meter-diameter Target Chamber that served as a stand-in for the engine room of the Starship Enterprise.
Unfortunately, not all visitors have that opportunity; when NIF is engaged in shot operations, tours are limited to the NIF lobby. Now a team of Lawrence Livermore graphic designers has developed a new computer-based augmented reality tool (ART) that lets visitors navigate their way to—and into—the Target Chamber without ever leaving the lobby.
The tool, introduced this past summer, runs on a tablet that viewers manipulate to display views of the Target Chamber on a 20-foot wall of video monitors, offering viewing options to all tours regardless of whether the facility is conducting shots.
ART combines cutting-edge augmented reality and virtual reality (VR) graphic arts in the service of science. The program was created by graphic artists in the NIF & Photon Science Directorate Document Services group, working with the LLNL Technical Information Department Visualization Team.
“People can get the ‘wow’ factor from the moment they walk in and see this,” said John Jett, a NIF Document Services graphic artist and a leader in the creation of the augmented reality tool. “The quality of the presentation of the ART and the novelty of the technology itself really brings home that sense of wonder around the engineering marvels of this facility.”
To carry out its vital stockpile stewardship, national security, and Discovery Science missions, NIF operates virtually around the clock. Constant shot operations mean tours must be restricted to the lobby nearly half the time. The new augmented reality tool gives visitors the ability to see how parts of NIF work simply by pointing the 10-inch-wide tablet at a five-foot-tall scale model of the Target Chamber. Various parts of the model trigger different views on the tablet that are displayed on the video wall.
Walking Through Walls
Physicist Brent Blue, the NIF National Security Applications Program manager, prefers offering visitors both the physical tour and the augmented reality option when possible, to illustrate his explanations of the science behind the work done at NIF.
“With the ART, you can literally walk through layers of the Target Chamber you can’t even see when you’re standing physically next to it,” Blue said. He especially likes how the tool can show the laser beams hitting the target and can make the chamber appear transparent.
Blue believes visitors at all levels, not just non-scientists, can benefit from the augmented reality experience. “People get a better understanding of how complicated the facility really is,” he said, “and how we are working to solve the hard problems that we’re solving every day.”
The Document Services group had been working for several years on making the NIF tour route more interactive. In 2016, Group Leader Pam Spears led the installation of the wall of video monitors to give the NIF lobby a polished professional look and to add multimedia options for communicating the complex subject matter.
“We wanted to make everything in the visitor experience meet the high standards of the National Ignition Facility,” Spears said.
Jett and Brian Chavez, Document Services graphic design associate, worked to find a way to turn the complex physics of NIF into an understandable visual-art medium for the tour route. They teamed with Adam Connell, Jacob “Jake” Long, and Ryan Goldsberry on the Visualization Team of the Lab’s Technical Information Department. The artists previously had worked in the video-game, film, and television industries.
The artistic team embarked on a combination of augmented-reality and virtual-reality digital displays, harnessing the power of video-game engines. They developed artwork for the tablet based on the NIF scale model, photographs, and the engineering-style CAD (computer-aided design) models developed by NIF design engineer Paul Bloom.
“We wanted to retain the accuracy and integrity of the models foremost,” Long explained.
On the tablet they also used full virtual-reality mode in depicting the detailed hohlraums for the NIF targets, employing more realistic engineering models provided by Bloom (see “Crash-proof Virtual Flying Through NIF”). “We didn’t want to dumb those down in any way,” Long said. The digital program even lets viewers simulate firing lasers on virtual targets.
For Connell, a major challenge was accomplishing the contrasts in scale: creating art that translates from the size of a tablet to the size of the monitor wall, and rendering artwork with enough detail to capture the actual experience of encountering the massive Target Chamber.
The team plans to expand the AR tool, Jett said, by building out other areas of the facility such as the Master Oscillator Room, where the laser beams originate, and the laser bays. This would let visitors follow the path of the laser as it traverses the facility and dive into the complex components along that path.
“You’re Superman with x-ray vision,” Chavez said, “and you can see lasers at work. Imagine the possibilities.”
The last U.S. underground nuclear test took place 25 years ago this month; ground was broken for NIF five years later. In the years since, the National Nuclear Security Administration’s Stockpile Stewardship Program, with NIF as a key component, has ensured that the nation’s nuclear deterrent remains safe, secure, and effective.
A blend of beautiful blue and green hues jump off the computer screen of LLNL physicist Todd Hoover. The visualization is a simulation of an underground nuclear test that took place on Sept. 18, 1992.
Hoover was a test coordinator on the experiment, code-named Hunters Trophy. As nuclear tests go, this was a relatively small explosion, less than 20 kilotons, conducted deep inside a sealed horizontal tunnel drilled into a mesa at the Nevada Test Site (now called the Nevada National Security Site). After a direct flight home from the airstrip at the test site, it was business as usual for Hoover. He was already preparing for the follow-on test.
Little did Hoover know that Hunters Trophy would be LLNL’s last nuclear test. Livermore’s sister lab, Los Alamos National Laboratory, would conduct its last test five days later, and on Oct. 2, 1992, President George H.W. Bush would declare a unilateral test moratorium. The 47-year era of U.S. nuclear testing—1,054 tests in all—would come to an end.
“I was shocked,” Hoover said. “With the end of the Cold War, I thought we would eventually reduce the maximum yield of tests, and I was actually working with our sponsors to prepare for that. Some other colleagues here at Livermore did see it coming, but I didn’t. We weren’t sure a design community would be needed any more.”
Stockpile Stewardship is Born
The weapons program at LLNL was faced with an identity crisis. Not only had testing ended, but the days of designing new weapons was suddenly in the rear-view mirror. The future of the Lab was uncertain, as was the approach that should be taken to maintain the U.S. stockpile without testing. Enter Vic Reis, the architect of the Stockpile Stewardship Program (SSP), which ensures the safety, security and effectiveness of the nuclear deterrent to this day.
“I was told that we needed to look at other ways of ensuring the safety, security and effectiveness of the stockpile,” said Reis, who had been appointed assistant secretary of Defense Programs in the Department of Energy. “Bob Bell, who was special assistant to President Clinton and director of Defense Policy and Arms Control, asked me to get started, and to come back when we knew how we were going to do it. To be honest, we didn’t know whether it would work at the time.”
To get started, Reis took the weapons program leadership from the national security laboratories and conducted a two-day strategic planning sprint. In the end, they had formulated a rough outline of how they would approach a science-based method for maintaining the stockpile. After that session, Reis gave the idea a 50 percent chance of success.
“In some ways, the biggest challenges were psychological, to get people to believe it could be done,” he said. “The business model at the labs was developing new weapons frequently, competition between the labs and then testing to provide evidence of which approach was superior. We suddenly faced a situation where none of that was happening.”
With the new SSP formally established by the 1994 National Defense Authorization Act, LLNL faced a new set of challenges that would define its future. Researchers would use science alone to assess the aging stockpile and certify that weapons with refurbished components would still function as expected. Success would rely on the creation of a computational testbed to replace nuclear tests, and the development of the experimental capabilities required to underpin those simulations with real-world data.
Over the course of the next decade, Livermore would install new generations of massively parallel supercomputers and build NIF, the world’s largest and highest-energy laser system, to enable researchers to replicate the high energy density conditions that only occur within nuclear weapons and in the cores of stars and massive planets.
The first major success of the SSP came in 1999, when Livermore researchers completed the first-ever refurbishment and certification of a nuclear warhead in the post-testing era. This work ensured that the W87 warhead could remain part of the enduring stockpile beyond 2025, and the certification without testing was a milestone for the new Stockpile Stewardship Program.
The First Generation of ‘Stewardship Physicists’
Across the Lab from Hoover sits Juliana Hsu. Like Hoover, Hsu has made her career at LLNL as a weapons physicist. Unlike Hoover, who participated in four tests during his career, Hsu was hired just as testing came to an end. Her significant scientific contributions have helped ensure the safety, security and effectiveness of the U.S. nuclear stockpile.
But unlike the generations that preceded her, she has never designed a new weapon for the stockpile, nor has she been involved in a nuclear test. Her career as a weapons physicist is defined by the transition to stockpile stewardship.
“When I came in, stockpile stewardship was just ramping up,“ said Hsu. “The mood was apprehensive, and there were lots of questions and debates about how it would work. As we advanced the computation capability, we also began to realize that we needed more of the fundamental data and experimental capabilities to verify that the calculations were correct. It became clear that we would need a deeper understanding of weapons physics to do our job without testing.”
Hsu was hired into LLNL as a code physicist. Her early focus was on developing the first functioning three-dimensional code for the stockpile. As her career progressed, she helped lead a number of efforts to extend the life of aging weapon systems. She made a tremendous impact through this work, being named a Distinguished Member of the Technical Staff and climbing the ladder to now serve as deputy director of the Weapon Physics and Design Program.
“We are responsible for keeping the deterrent viable into the future.”
Despite these career accomplishments, the modest Hsu is quick to deflect credit for her role in the success of stockpile stewardship. But it was because of researchers like her that the United States has been able to maintain its nuclear deterrent for a quarter century without testing.
“I came for the challenging scientific work,” Hsu said. “But as I understood more about the mission, it came became more and more important to me. That was the part that was meaningful. We are responsible for keeping the deterrent viable into the future.”
Weapons Physicists of the Future
While Hoover was in Nevada for Livermore’s last nuclear test, new hire Madison Martin was just beginning her 22-year academic journey as a four-year-old in preschool. Hired last month, she is one of 14 design physicists hired in the past year.
Facing a completely different threat landscape than Hoover did, and stepping into a well-established science-based SSP built on the work of researchers like Hsu, the future of U.S. security will one day fall on the shoulders of the next generation of weapon scientists like Martin.
“What attracted me to Livermore was that it offered a way for me to contribute to science that was important to the nation,” Martin said. “It’s very meaningful to me to be part of that, and it’s great to have experienced mentors to learn from.”
Martin brands herself as a computational designer, running massive codes to better understand high energy density physics. She will be designing and analyzing experiments on NIF to provide better data to underpin annual assessments of the aging stockpile.
While Martin is getting her feet wet with NIF experiments, across the Lab, Hoover examines the blue-green visualization of Hunters Trophy on his computer screen. Asked why he’s looking at that test today, he is quick to point out that he hasn’t been looking at the same simulation for the past 25 years. Nor is he reminiscing about a bygone era. Hoover has returned to LLNL from retirement with a renewed sense of mission. He is focused on getting a better understanding of the old underground test data to help the next generation of physicists.
“Hunters Trophy was special to me, not just because it was our last test, but because of the science,” Hoover said. “The results were unexpected and very exciting. We’ve effectively replaced testing with a computational testbed, and it’s only as good as the data we have. The results of this study will help the next generation of weapon physicists make modern assessments of the stockpile.
“I’ve had plenty of successes in my career, but when I was about to retire, I was told that I would fail at it,” Hoover said with a sly grin. “And here I am. The science still fascinates me, and the mission is just as real as it was in the Cold War. It’s still very important to me.”
“Extending the Life of an Aging Weapon,” Science & Technology Review, March 2012
“Stockpile Stewardship at 20 Years,” Science & Technology Review, July 2015
LLNL researchers are working to adapt the specialized optics used in orbiting x-ray telescopes to provide high-resolution images of man-made x-ray sources here on Earth, such as those produced at NIF and the Z Pulsed Power Facility, or Z Machine, at Sandia National Laboratories.
As a start, LLNL’s long-time expertise in x-ray optics is being tapped in a multi-institutional effort to develop a new x-ray diagnostic for the Z Machine—like NIF, a key element of the National Nuclear Security Administration’s Stockpile Stewardship Program. The Z Machine concentrates electrical energy and turns it into short pulses of enormous power, which are then used to generate x rays and gamma rays—a technique known as Z pinch. The facility is used for research in inertial confinement fusion and high energy density science.
The new x-ray diagnostic is a high-resolution Wolter optic, which acts as a lens and is capable of providing spatial resolution and sensitivity far superior to existing instruments. It consists of high-precision curved surfaces coated with carefully-designed multilayers to provide a specific, narrow-band x-ray image. Data produced by the Wolter optic are expected to improve the Z Machine’s x-ray source for testing radiation effects on non-nuclear components under extreme conditions.
While the optic is new to the Z Machine, Wolter optics are widely used in space-based telescopes such as the Chandra X-ray Observatory and NuSTAR (Nuclear Spectroscopic Telescope Array) because of their ability to reflect, rather than absorb, high-energy x-ray light from space and focus it onto a detector.
Laboratory researchers designed and calibrated the replicated optic and developed the reflective multilayer coatings on its mirrors. The NASA Marshall Space Flight Center fabricated the high-quality mandrel used to produce the optic, and the Harvard-Smithsonian Center for Astrophysics (CfA) is coating and replicating the multilayer optics.
LLNL astrophysicist Julia Vogel said the Laboratory, as overall project manager, provides the link between NASA Marshall, CfA, and Sandia “to ensure the optic fulfills the requirements needed for successful operation in the Z experiment. NASA and the CfA are the experts in fabricating these mirrors,” she said. “These optics are very, very small compared to the ones for astrophysics, which tend to be much larger. So specialized methods to get the mirrors extremely smooth and deposit the complex coatings are necessary to get as much light reflected as possible. The Z Wolter is actually one of the smallest replicated optics they have fabricated to date.”
Next in the Queue: NIF
Vogel said the first optic should be ready for testing at LLNL and Sandia within the next few weeks; the first shots using the new diagnostic are scheduled for December. In parallel, the LLNL team is working on enhancing the Wolter optic for use in NIF.
“Wolter optics are interesting tools for both Z and NIF,” she said, “but the NIF requirements are very strict; so starting with the optic for Sandia was a natural choice.”
While the Z experiment needed a resolution of about 100 microns over a rather large field of view to image the Z pinch, NIF operators are asking for closer to five-micron resolution. And while Sandia initially wants to image x rays with a wavelength of 17.4 keV (kiloelectronvolts), “NIF experiments are pushing towards higher energies between 20 and 30 keV for starters,” Vogel said.
Compared to other x-ray diagnostics, the Wolter optic “gives better resolution and higher throughput (of photons),” she said, “which is especially valuable for NIF because when we look at the higher energies we tend to have fewer photons. The Wolter can improve over pinholes (current pinhole cameras) because you get more throughput and still have good resolution.”
Along with Vogel, members of the LLNL Wolter optic team are Mike Pivovaroff, Christopher Walton, Bernie Kozioziemski, Perry Bell, Jay Ayers, and Louisa Pickworth.
“Turning an X-Ray Eye on Universes, Large and Small,” Science & Technology Review, November 2015
The cover story in the July/August 2017 issue of Science & Technology Review, “Advanced Laser Promises Exciting Applications,” takes an in-depth look at the development of the Livermore-designed High-Repetition-Rate Advanced Petawatt Laser System (HAPLS), the applications it will enable, and the future of high-energy laser systems building on the project’s success.
HAPLS is designed to deliver petawatt (quadrillion-watt) laser pulses with energy of at least 30 joules and durations less than 30 femtoseconds, at a repetition rate of 10 times a second (10 Hz). The laser system is now being integrated into the European Union’s Extreme Light Infrastructure (ELI) Beamlines facility in the Czech Republic.
Although ELI Beamlines will house at least two other large lasers, HAPLS is expected to be the “workhorse” laser and will be known as the L3 laser system. The facility will include seven experimental chambers located in the basement, including a large chamber dedicated to academic research of laser plasma. Scientists will be able to direct the output from any laser to whichever experimental chamber is needed.
ELI Beamlines was built for the international scientific user community to study laser–matter interactions, with the goal of making the facility the “CERN of laser research.” HAPLS and the other lasers will enable cutting-edge research in atomic physics, time-resolved proton and x-ray radiography, nuclear physics, high-energy-density physics, plasma physics, chemistry, biochemistry, and medicine.
In biochemistry, for example, scientists anticipate using streams of extremely bright and short x rays for imaging cells and proteins at unprecedented spatial and temporal resolution to study the time history of biochemical reactions and the formation and dissolution of chemical bonds. The facility also could be used to explore the science of possible future oncology treatments for deep-seated tumors by studying how high-quality beams of protons or ions interact with tissue.
The first experiments at ELI Beamlines are scheduled for late 2018.