Physics for national security

“I have one of the coolest jobs in the world,” says physicist Rachel Smullen. “I do some of the most interesting and impactful things. Some days, the work that I do goes to the president’s desk.” 

The president of the United States, that is.

That’s because Smullen works at Los Alamos National Laboratory—one of three laboratories in the country responsible for the design and maintenance of America’s nuclear weapons. Because nuclear reactions happen so quickly, at such small scales, a combination of physicists, engineers, and some of the fastest supercomputers in the world are necessary to understand how these weapons work, age, and behave in a range of conditions.

Smullen is 1 of about 300 Los Alamos scientists—modern-day Oppenheimers, if you will—working in the branch of the Laboratory that “develops and applies cutting-edge theory, computational models, large-scale weapon simulation codes, and the design and execution of innovative and pioneering experiments,” says Charlie Nakhleh, associate Laboratory director for Weapons Physics. The staff also works on nuclear counterterrorism, nuclear nonproliferation, nuclear forensics, and emergency response. “This is big science,” Nakhleh says.

Physicist Beth Lindquist says that although her career is difficult to explain to the general public—particularly given security considerations—it’s extremely compelling. “In the weapons physics community by its very nature, we are doing cutting-edge work that very few places in the world are able and allowed to do,” she says. “You’re leading the charge in the field. That’s a unique aspect to working here.”

A complex process

Work in weapons physics often begins with a request from the military, who is the custodian and potential user of America’s nuclear weapons. “When we design a weapon, we begin by looking at the requirements and considering what might meet the military’s requests,” Smullen explains. “We ask ourselves, ‘How can we approach the design and engineering to fit these requirements?’”

These types of questions result in a theory, or an explanation of how a system works, or could work, based on observations, experiments, or existing scientific principles. “Physics theory is my strength,” says Baolian Cheng, a computational physicist who has worked at Los Alamos for more than 30 years. “I am always working in abstract space. I start with theory and then ask myself, ‘How can we observe it? What is the evidence? How can you prove it?’”  

Next, physicists build a computer model that translates the theory into a mathematical framework. Then they write computer codes that implement the model to create simulations—representations of the outcome of the process or behavior. “All throughout the process, we run simulations,” Smullen says. “Every time we make a design change, we run a new simulation. We are always asking whether the design can be certified as safe, secure, and effective.”

“My job involves using computer models to create simulations of current weapons designs and concepts for the future,” says physicist Jessica Thrussell. “We model experiments to check that our codes are simulating reality as best as they can, and we make improvements to how we run the codes.”

Thrussell says she finds this process extremely gratifying. “I get to see results from my work and what I’m doing is relevant—it has real-world impact and national importance.”

Weapons designers move from theory to model to simulation, drawing on experimental data along the way.  Los Alamos physicists also conduct experiments to test their theories, validate their models, and gather data. “I think one of the highlights is when you work on an experiment, and there are many different people contributing to it, and you get to make a measurement at the end that is useful,” physicist Candace Joggerst says.

 A desire to learn and collaborate

A uniting characteristic of the physicists at Los Alamos National Laboratory is curiosity. These scientists are driven by the desire to gain knowledge, answer questions, and push the boundaries of the unknown. “I have a passion for answering questions,” says Ryan Jadrich, a physicist who works in post-detonation nuclear forensics. “Basically, I work on how to reverse-engineer nuclear detonations to determine what happened. I see my work as solving puzzles using inverse design methods of systematically going backward. I will keep digging deeper to get answers,” he says.

Smullen says she appreciates the fact that there is always something new to learn at Los Alamos. “The type of people drawn to studying physics are the type of people who are always wondering why. Our brains never shut off.” She describes her work as ideal for someone passionate and creative. “I feel excited that every year people come to me with new ideas and projects,” she says. “The work constantly evolves. There is no rut to get stuck in. It’s all fresh snow.”

Smullen and her colleagues say they welcome challenges. “The complexity of the problems are multidimensional and multivariable phenomena are complicated,” Cheng says. After three decades at the Lab, she is still full of energy and enthusiasm. “My work is never boring. My work is my hobby,” she says.

For Thrussell, part of the appeal of Los Alamos is not getting pigeonholed into one area. “Most of us have several different projects and work on many different types of problems throughout our career and appreciate continued learning.”

Lindquist, who works in nuclear threat assessment and global security, calls her work fast-paced and dynamic. “There’s a collaborative environment in weapons physics and global security and that really appeals to me,” she says.

Scientists often cite Los Alamos’ collaborative culture as one of the key benefits of their work. Eli Feinberg started at the Lab as a staff member doing software development and is now earning a doctorate in applied physics at the University of Michigan while working at the Lab. “What really has me continuing to work with the Lab is the people there,” he says. “I think about my coworkers and how much I’ve learned from them and the high regard I have for them.” He adds, “If I won the lottery, I would still want to do this work. I think it’s really fulfilling.”

The high caliber of the staff is another benefit that the Lab’s physicists often mention. “The people who are successful here are the ones that aren’t intimidated that they’re not the expert in the room, but they’re excited that they get to sit in the room with so many experts,” Joggerst says. “We like to argue—turn over different aspects of things, chew on them and consider them from different perspectives. You need a variety of technical backgrounds in an organization because no one can be an expert in everything, but we are each an expert in something.”

Cheng agrees. “I work with so many amazing people,” she says. “It is a collaborative culture, and I have always felt respected and have had great mentors and colleagues.”

A drive for deterrence

Another commonality at the Lab is a commitment to nuclear deterrence and national security. “People recognize the need for unbiased technical expertise behind our nation’s nuclear deterrent,” Feinberg says, noting that when talking to people outside of the Lab he likes to emphasize the fact that his work helps provide a way to conduct crucial research without nuclear testing. “That is one of the things that makes me passionate about my work.”

Thrussell seconds that sentiment. “My colleagues and I all want to have a strong deterrent to ensure nuclear weapons are never used. That’s the motivation behind our work.”

Smullen says the national security mission is both motivating and challenging. “In today’s changing geopolitical situation, our jobs are transitioning as the Department of Defense asks for new things. We have to adapt to new technologies and develop flexibility in a world where our adversaries’ capabilities are expanding. The U.S. stockpile needs to adapt to that.”

This focus on the Lab’s national security mission always takes center stage when Smullen talks to graduate students and prospective employees. “We need people who are dedicated to the mission; we need global security; we need smart, ethical people working on these problems.”

Nakhleh says prospective Lab employees need to understand the significance and stakes of their work. “Nuclear deterrence is a cornerstone of global stability,” says Nakhleh. “Today’s and tomorrow’s nuclear deterrence is an integral part of the mission, employing advanced science and technology to safeguard the future of the country and the world.”

A struggle with stereotypes

Despite the significance of these Los Alamos physicists’ work, there are some things many of them struggle with—explaining what they do to casual acquaintances and combating unflattering stereotypes.

“We can’t really describe our work for security reasons,” Joggerst says. “When someone on an airplane asks me what I do, I say ‘I’m technically a designer, but most of what I do is modeling.’ I don’t explain what I design or that I mean computer modeling, not fashion,” she adds with a laugh.

Smullen notes, “When I say I’m a physicist, some people’s eyes glaze over. My mother said she never expected me to pursue a career related to national security. She once asked me what I do in my free time to be creative. I explained that my work is extremely creative.”

Then there are the stereotypes. Long ago, many movies and television shows depicted physicists as nerdy men wearing pocket protectors and carrying slide rules. Today, that stereotype is a bit more modern, but it persists.

Thrussell says people often ask her if she has seen The Big Bang Theory, a television comedy about a group of geeky physicists with a socially awkward main character named Sheldon. “I’m often asked if I work with a bunch of Sheldons or if I am a Sheldon. I reply, ‘What do you think? You’re talking to me,’” she says.  “While that physicist stereotype exists for a reason, and there are some people at Los Alamos who fit the stereotype, I think the public would be surprised by the diversity of the personalities of the people who work here.”

Lindquist says the diversity of the staff plays an important role in achieving the Lab’s national security mission. “In terms of the work we do and the mission, it’s really great to have a bunch of people from different backgrounds because people bring different perspectives.” She also debunks any resemblance to The Big Bang Theory stereotypes. “I don’t find myself or my colleagues to be anything like the physicists portrayed in the show.”

Feinberg, on the other hand, says he doesn’t mind public perceptions of physicists as geeky. “I try to be my own person and do what’s important and interesting to me. You’ll always find people who connect with that. At Los Alamos, it’s easy to find a core of people who are interested in science and accept you for the nerd that you might be.” ★

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