Funding from the Laboratory Directed Research & Development program critical for developing the award-winning WarpX code, making exascale simulations of particle accelerators possible.
Since their invention in the 1930s, particle accelerators have become essential tools for scientific research. They have allowed us to explore the properties and interactions of atoms, leading to deeper insights into the building blocks of matter and transforming our understanding of the world.
The next generation of accelerators promises more powerful machines capable of delving even deeper into the nanoworld of atoms. These accelerators, called laser-plasma accelerators, or LPAs, shoot an intense laser pulse into a plasma that scatters negatively charged particles and creates powerful electric fields that can push electrons up to speeds a thousand times faster than traditional accelerators. They could pave the way for advances in fundamental scientific research, leading to new areas of research and applications in energy, medicine, and materials science.
However, realizing the full potential of LPAs will require thousands of these accelerating stages working together. To speed up the development of LPAs, powerful computer simulations are needed to model the properties of these laser pulses, their highly-complex interactions with plasmas, and the characteristics of the accelerated particle beams. This is very time-consuming, even with the most powerful supercomputers.
Recognizing an opportunity
Recognizing the importance of large-scale accelerator simulations to advancing LPA technologies, in 2002, Berkley Lab Senior Scientist Phillip Colella, and Jean-Luc Vay, then a physicist in the Heavy Ion Fusion program and now a senior scientist and the head of Lab’s Accelerator Modeling Program in the Accelerator Technology & Applied Physics Division, successfully applied for funding from the Laboratory Directed Research & Development (LDRD) program to support the development of a new way of running simulations that would reduce the time required.
Based on the “Adaptive Mesh Refinement” (AMR) technique, first developed in the 1980s and applied to the field of fluid dynamics, the two researchers modified the AMR to the type of “Particle-In-Cell” (PIC) simulations used for particle accelerators.
While this approach led to an order-of-magnitude increase in the speed of some computer simulations, they needed to be even faster.
A breakthrough idea
In 2007, Vay had a serendipitous idea. He applied Einstein’s Theory of Special Relativity, which relates speed to mass, time, and space, to speed up simulations for accelerators. Again, the LDRD program stepped in, funding the “Lorentz Compaction of Scales for Ultra-efficient Simulation of Advanced Accelerators (and other Systems)” project.
The results were impressive, achieving calculations tens of thousands of times faster than comparable conventional methods. But more work was still needed to speed up different parts of the accelerator calculations.
However, as the methods developed in the project began to be applied, another pathway emerged to speed up a different part of accelerator calculations using local Fast Fourier Transform (FFT)-based spectral solvers for Maxwell’s Equations.
LDRD support stepped in once more in 2011, funding a project titled “High-accuracy Scalable Solvers for Modeling of Future Ultrafast Photon Sources.” This strategy proved very fruitful, creating an impressive tool that significantly improved the accuracy and stability of the calculations.
Making it all come together: PAS and Exascale WarpX
With all the strategies introduced over the years, the improvements in speed for the particle accelerator simulations were adding up to be significant. In 2014, Vay and his team made one more proposal: to combine all the improvements. The project was titled “High-Performance Advanced Particle Accelerator Simulator,” or “PAS,” and was again supported by the LDRD.
The project was so successful that the DOE took notice, and one year into the PAS LDRD funding timeline, the DOE’s Office of Science and the National Nuclear Security Administration decided to fund the Exascale WarpX project, one of the 25 applications selected to participate in the DOE Exascale Computing Project (ECP).
Today WarpX is arguably one of the crown jewels in the Department of Energy’s ECP and its computing initiatives. In 2022, it won the Gordon Bell Prize. The award recognizes outstanding achievement in high-performance computing. The prize was awarded to the 16-member WarpX team, which includes Vay and colleagues Axel Huebl, Kevin Gott, Remi Lehe, Andrew Myers, and Weiqun Zhang at the Lab, and collaborators at other institutions.
Learn More
- How LDRD Supported the Development of Simulations for Next-Generation Accelerator Technology
- Berkeley Lab Laser Accelerator (BELLA) Center
- “Plasma Particle Accelerators Could Find New Physics,” Scientific American, July 1, 2021
- Basics2Breakthroughs: Accelerating Particles in Plasma (YouTube presentation by Marlene Turner)
