Lawrence Livermore National Laboratory

October 13, 2022

An artist’s rendering of 192 high-energy laser beams converging onto a tiny target at NIFInside the National Ignition Facility, 192 high-energy laser beams converge onto a tiny target. Livermore’s Virtual Beam Line (VBL) code models the beam lines so users can fine-tune their experimental parameters before executing a shot. (Credit: Jacob Long)

The following is an excerpt from an article by Holly Auten in the June 2022 issue of Science & Technology Review:

In the 25 years since breaking ground on the National Ignition Facility (NIF)—a cornerstone of the National Nuclear Security Administration’s Stockpile Stewardship Program—Lawrence Livermore National Laboratory has steadily pushed the boundaries of laser physics, nonlinear optics, and photonics in service of inertial confinement fusion experiments and advanced photon sources development.

Beyond the 192 beam lines of the primary laser facility with its world-record energy and fusion yields, the NIF & Photon Science Principal Directorate’s capabilities have expanded to include chirped-pulse amplification, kilojoule petawatt-class short-pulse systems to generate hard x-ray radiographic probes, high-average power lasers for directed energy applications, and other scientific pursuits. (See S&TR, July/August 2017, Advanced Laser Promises Exciting Applications; September 2018, Two World-Class Lasers Combine to Power Applications; and, June 2019, National Ignition Facility Celebrates 10 Years of Operation.)

One crucial capability that helps enable these activities is the Virtual Beam Line (VBL) laser simulation code, which launched in 2000. It can model all the major laser physics and technology involved in the design optimization, commissioning, and operations of tabletop to NIF-scale lasers.

VBL provides scientists with high-fidelity models and high-resolution calculations of laser performance predictions for the entire NIF laser system, the Advanced Radiographic Capability, the Optical Science Laser, and parts of the High-Repetition-Rate Advanced Petawatt Laser System for ELI Beamlines in the Czech Republic.

After more than two decades of experimentally verified physics and computing enhancements, this unique code underwent a modernization effort a few years ago to increase the scalability and expand the physics supporting a wider array of applications and customers.

With funding from the Laboratory’s Institutional Scientific Capability Portfolio (ISCP), VBL migrated from Java to C++ with a flurry of user interface and optimization features, as well as laser physics and high-resolution enhancements primed for parallel execution on Livermore’s supercomputers.

“VBL is key to laser scientists’ ability to design architectures and experiments and to deliver results. It plays a critical role in ensuring machine safety and preventing damage during experiments. Our team is looking forward to deploying the new functionality into production,” software engineering manager Kathleen McCandless said.

The VBL++ project is another success that developed from the longstanding partnership between NIF and Livermore’s Computing Directorate, which encompasses numerous projects and technologies from diagnostic measurements and advanced control systems to data analysis, information technology infrastructure, and scientific simulation code development.

As the code’s user base grows beyond NIF, the team is working to support other experimental laser systems and plans to support the designs for the Matter in Extreme Conditions laser facility at the SLAC National Accelerator Laboratory.

According to McCandless, this expansion into new physics capabilities also serves as an attractive opportunity for recruiting talented scientists.

“Our code has endured because no other product can handle everything that it can,” she said. “Future laser systems will be very different from what we have today, and VBL++ will help Livermore meet those challenges.”

To read the full story, go to Science & Technology Review.

More Information:

“Laser Improvements Contributed to Record Fusion Experiment,” NIF & Photon Science News, December 15, 2021

“LLNL’s Virtual Beam Line ++ Now Available to Users,” NIF & Photon Science News, April 3, 2019

“Tom Epperly: A Software Architect Starts Early,” NIF & Photon Science News, January 23, 2019

—Holly Auten

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