Scientific Achievement
An international team of researchers has combined two numerical modeling techniques to simulate laser-plasma accelerators (LPAs). This work significantly improves the feasibility of modeling high-energy LPAs by enabling accurate simulations with modest computational resources. The approach is particularly relevant for designing staged LPA systems and, potentially, a future plasma-based linear collider.
The team included researchers from the Accelerator Technology & Applied Physics (ATAP) Division at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), the Laboratoire de Physique des Gaz et des Plasmas, CNRS, Université Paris Saclay, Orsay, France, and the Laboratoire Leprince-Ringuet, CNRS, Palaiseau, France.
Significance and Impact
The properties and rapid development of LPAs (e.g., the recent production of 10 GeV beams in a 30-cm-long plasma demonstrated at ATAP’s BELLA Center) make them interesting candidates as drivers for future applications in high-energy physics. The 2023 Particle Physics Project Prioritization Panel (P5) Report emphasizes the need for research and development of next-generation colliders capable of probing physics at the 10 TeV pCM scale.
Progress in the performance of LPAs has been driven by modeling, which has helped deepen the understanding of the complex, non-linear physics involved in laser-plasma interactions. However, numerical modeling of LPAs is a computationally challenging task due to the large-scale imbalance involved in the modeling, which spans from the micrometer scale of the laser fields to the meter scale over the total acceleration length.
Evolution of the normalized laser strength and electron bunch parameters for different values of the boost velocity.
Modeling becomes more accessible when using reduced physics models that lower the computational complexity of the problem. Examples of such models include the time-averaged ponderomotive approximation (TPA), which analytically filters out fast laser oscillations and reduces resolution requirements; and the Lorentz-boosted frame (LBF) technique, developed at Berkeley Lab, which utilizes relativistic frame transformations to minimize the disparity between relevant spatial and temporal scales.
This study demonstrates that the TPA and LBF techniques can be combined. Results obtained using both methods are in excellent agreement with those from conventional modeling techniques (i.e., not relying on reduced physics models). This new technique could significantly reduce the computational cost of simulating LPAs, providing several orders of magnitude in computational speedups without sacrificing accuracy. It could become essential for the modeling of a future, multi-TeV, LPA-based lepton collider.
Research Details
Comparison of the electron density ne/n0 and |a| on the z−y plane at ct≈19.35 cm. The red and yellow dots are a scatter plot of the electron bunch macroparticles. Top half panel: γb = 1 (laboratory frame); bottom half panel: γb = 39. The simulations in the laboratory and boosted frame show a remarkable agreement.
Both the TPA and LBF methods are well-established computational techniques widely used to model LPAs, with their accuracy, reliability, and limitations documented over the past several years.
To effectively combine the LBF and TPA approaches, a Lorentz-invariant formulation of the TPA scheme is necessary. This study explains how to implement the TPA in a Lorentz-invariant form, examines the limitations of the combined approach, including the maximum Lorentz boost velocity that can be utilized, and provides an expression for the potential computational gains.
The combined TPA-LBF approach is validated using the particles-in-cell codes SMILEI and INF&RNO, developed at CNRS, École Polytechnique, Commissariat à l’énergie atomique et aux énergies alternatives, and the University of Paris-Saclay, as well as at Berkeley Lab. The results show excellent agreement in beam dynamics, field evolution, and laser behavior, even at high Lorentz boosts.
Contact: Carlo Benedetti and Davide Terzani
Researchers: Carlo Benedetti and Davide Terzani (Berkeley Lab); Francesco Massimo and Brigitte Cros (Laboratoire de Physique des Gaz et des Plasmas); and Arnaud Beck (Laboratoire Leprince-Ringuet)
Funding: This work was supported by the Director, Office of Science, Office of High Energy Physics, of the U.S. Department of Energy and used the computational facilities at the National Energy Research Scientific Computing Center. This work was granted access to the GENCI’s Tres Grand Centre de Calcul high-performance computing resources.
Publication: F. Massimo, C. Benedetti, D. Terzani, A. Beck, and B. Cros. “Modeling laser-wakefield accelerators using the time-averaged ponderomotive approximation in a Lorentz boosted frame,” Plasma Phys. Control. Fusion 67 065032 (2025), https://doi.org/10.1088/1361-6587/addc97
For more information on ATAP News articles, contact caw@lbl.gov.
