Lawrence Livermore National Laboratory



Summer Scholar Explores the Flexibility of Fibers


Researchers Recognized for Accomplishments in Early and Mid-Career

Four NIF & Photon Science-related researchers have been selected for LLNL’s third annual Early and Mid-Career Recognition (EMCR) Program. They are among 15 Laboratory scientists and engineers named to the program this year.

“Rewarding exceptional early and mid-career employees is key to retaining and developing a world-class workforce,” said Laboratory Director Bill Goldstein. “This program recognizes technical staff who have demonstrated significant accomplishments early in their careers, and show great potential for future leadership.”

The EMCR Program recognizes scientific and technical accomplishments, leadership and future promise demonstrated by LLNL scientists and engineers early in their careers—from five to 20 years since they received their most recent degree. Winners receive a cash award and institutional funding, approximately equivalent to 20 percent support for one year, to pursue research activities in their area of interest.

Among the Fiscal Year 2017 winners are:

Hui Chen

Hui Chen is an internationally recognized physicist who has made important contributions to several areas of plasma physics, most notably in the new field of relativistic positron generation via intense laser-matter interactions.Hui ChenHui ChenShe became a 2016 fellow of the American Physical Society from the Division of Plasma Physics for her work in this field.

This work in fundamental physics has captured the imagination of the physics community. Her first Physical Review Letters paper in 2009, which discussed the largest production of positrons by laser-plasma interactions to that date, was cited by more than 200 websites, including Popular Mechanics, Discovery News, Physics Focus, CERN Courier, Nature Photonics and Science News.

Chen is the experimental and intellectual lead of these studies, which now include national and international collaborators in both theory and experiment. Chen designed, built, and calibrated the electron/positron/proton spectrometers needed for this research and developed the data analysis methods.

“I am extremely honored by this recognition,” Chen said. “Ever since I came to the Lab 18 years ago as a postdoc, I have been fortunate to have excellent mentors and mangers, kind and knowledgeable colleagues and hardworking students—and I am grateful to them all.”

Because she was trained and nurtured in high energy density physics (HED) at the Lab, she plans to give back “by contributing to our new HED Center, training young scientists, and working on some new ideas.”

Tilo Döppner

Tilo Döppner is an experimental physicist who has significantly contributed to the exploration of HED plasmas and matter at extreme conditions, with relevance to fundamental science, inertial confinement fusion (ICF) and national security applications.

Tilo DöppnerTilo Döppner

He has been a leading member in many diverse teams of scientists performing complicated experiments at HED facilities, such as NIF, the Omega Laser Facility at the University of Rochester, the Titan and Janus lasers at LLNL’s Jupiter Laser Facility, the Linac Coherent Light Source at the SLAC National Accelerator Laboratory, and the Free Electron Laser in Hamburg, Germany. He is a world leader in the use of x-ray scattering to diagnose HED plasmas, as well as an expert in the areas of implosion diagnostics, radiography, and the physics of ICF.

Döppner made significant contributions to indirect-drive experiments on NIF when he published the first spatially-resolved measurement of electron preheat in indirect-drive implosions. He also was responsible for some of the highest-performing ICF implosions to date. In 2013 and 2014, he made fundamental contributions to the experiments that achieved fuel gain exceeding unity. He also was the lead author on the high-impact paper on the use of uranium hohlraums, which was essential to the success of these experiments.

“I’ve been at LLNL for almost 10 years now, and this is the first individual award that I have received,” Döppner said. “I am grateful to all the people who mentored and supported me. Without their help I could not have accomplished the work that is recognized by this award selection.”

He plans to continue working on developing x-ray Thomson scattering measurements from plasmas at extreme densities, generated by capsule implosion experiments at NIF.

Nathan Meezan

Joining the Lab in 2002, Nathan Meezan quickly established himself as one of LLNL’s experts in hohlraum physics and design for laser-driven targets, and was chosen to be the lead designer for the important first implosion campaign on NIF. Meezan showed his technical and leadership skills during the campaign, which studied hohlraum energetics and drive symmetry. Nathan MeezanNathan MeezanDespite being relatively junior, he played a significant role in bringing together the interdisciplinary team needed for the experiments—target physicists, target fabrication specialists, diagnostic specialists, and laser experts. He was among the winners of the 2012 APS John Dawson Prize for Excellence in Plasma Physics for this work on NIF.

Meezan led the high-density carbon (HDC, or diamond) ablator campaign on NIF. This campaign leverages his expertise in hohlraums by using a new low-fill, near-vacuum hohlraum. He championed this design, which has opened new possibilities for hohlraum performance on NIF. The ICF program is actively pursuing multiple hohlraum designs like the one put forward by Meezan.

“I am extremely honored to receive this award,” Meezan said. “I know many of the recipients of the EMCR, and I am humbled by their abilities and achievements. I am proud to be counted among them. I am also grateful for the excellent support and mentoring I have benefitted from during my LLNL career.”

Vladimir Smalyuk

Vladimir SmalyukVladimir Smalyuk

Vladimir Smalyuk is a world-recognized expert in hydrodynamics, as demonstrated by his 46 first-author publications in the field. He has been involved in understanding the impact of hydrodynamic instabilities on ICF, both direct and indirect drive, HED physics for stockpile stewardship, and the role hydrodynamics plays in astrophysical phenomena.

He is the experimental leader of capsule physics in the ICF Program and has led the experimental development of adiabat-shaped implosions to develop a way to minimize hydrodynamic instabilities in low-adiabat ICF implosions. He also has led the effort to reduce the impact of fill tubes on ICF implosions.

“I am very excited and feel honored,” Smalyuk said. He plans to spend a portion of his time working with younger scientists on Discovery Science campaigns on NIF and “writing papers that I did not have time to work on before.”

Summer Scholar Explores the Flexibility of Fibers

The biggest surprise so far for NIF & Photon Science Summer Scholar Montrey Freeman has been the flexibility of physics. The thinner he pulls the doped glass in the NIF Optical Fiber lab, the more it challenges his preconceived notions about the substance.

“I had no idea glass would bend like plastic—it just keeps going and going,” said Freeman, who has been exploring the properties of optical fibers in the fiber lab. Working with his mentor, NIF Fiber Laser Group Leader Mike Messerly, Freeman is analyzing how to strengthen the fibers.

Summer Scholar Montrey FreemanMontrey Freeman at work in LLNL’s Fiber Draw Tower. Photos: Jason Laurea

Freeman traveled 3,000 miles across the country for the opportunity. As a materials science engineering graduate student at Virginia’s Norfolk State University, he found working on the physics of optical fibers a challenge at first. He earned his undergraduate degree in math from Allen University, an historic institution founded by former slaves in his native South Carolina, and he currently studies materials science engineering. At Norfolk State, his most recent project involved nanotechnology and nano-electrodes in rats’ brains. So in a way he’s gone from working with brain fiber to laser fiber.

“This was a whole other area than I’m used to,” Freeman said, “but that’s what I hoped for when I applied here. Because no matter what, I knew I would be doing top-of-the-line science for this internship; I wouldn’t just be doing busy work.”

And in fact, his project—testing the tensile strength of NIF optical fibers—is expected to produce data that will feed into the fabrication process and potentially help fine-tune the fiber lab’s acid-cleaning and cleanroom-assembly procedures, according to Messerly. “The goal is to make our laser fibers stronger, with Montrey’s help,” Messerly said.

To find ways to make fibers more consistent, Freeman is working primarily on LLNL’s unique fiber draw tower, the only one of its kind in the national laboratory system. It enables the drawing of custom fiber optics of select purity and varying diameters. Freeman is expanding his experience by working in both the tower and the cleanroom, where he also has worked at Norfolk State, a historically black college which has a partnership with the Lab in its optical fibers program.

For his internship experience, Freeman also had the advantage of comparing his current internship project with work he’s done in other summers, including a previous internship with Livermore Lab in computer science and one with Sandia National Laboratories in New Mexico. He’s taken advantage of his opportunities this summer by renewing his explorations of the nearby Bay Area.

Summer Scholar Montrey Freeman Studies an Ultrathin FiberFreeman examines the properties of an ultrathin fiber.

Among the highlights, he said, have been the NIF & Photon Science Summer Scholar program’s regular Wednesday symposiums. Open to all summer interns, the symposiums offer lectures from scientific leaders on a range of cutting-edge subjects that Freeman said are especially interesting because they cover in-depth physics that are new to him. “And then I might end up going and doing it later (in the Lab) so it will really click,” he said.

Freeman dreams of living in Europe and Australia some day. His favorite pastime is taking in a satisfying action-adventure film on the big screen. His long-term goal is to work in the national laboratory system, because he finds contributing to the art of research rewarding.

“There are so many variables in the work in a lab—that’s what I like,” he said. “We can only focus on finding the perfect recipe to figure out how to get the best results, and that’s a fun challenge in itself.”