The project, carried out by the University of Hamburg in partnership with DESY under the LADIAG consortium, aimed to improve the performance of high‑intensity lasers for both laser‑plasma acceleration and nonlinear quantum electrodynamics experiments. Led by Prof. Florian Grüner (UHH) and A. Maier (DESY) and funded by the German Federal Ministry of Education and Research (grant 05K19GUD), the work ran from the second half of 2019 through 2023. Two doctoral theses and two habilitation projects were completed or are expected to finish by the end of 2023.

The scientific effort focused on two complementary approaches. First, the team performed extensive numerical convergence studies with the Particle‑In‑Cell (PIC) code FBPIC, investigating how the initial plasma temperature influences simulation stability. These studies provided the foundation for a major code upgrade: a new, experimentally realistic description of the driver laser pulse was implemented and released as open‑source software. Second, the project tackled the long‑standing problem of numerical Cherenkov radiation, which degrades PIC accuracy. By reformulating the PIC equations in a moving coordinate system, the researchers eliminated this artefact, achieving a dramatic increase in execution speed and markedly higher fidelity of the simulation results. The improved code enabled the first large‑scale tolerance and parameter studies for laser‑plasma accelerators, demonstrating that targeted feedback loops can stabilize and enhance accelerator performance. These findings also have direct implications for nonlinear QED experiments, where precise knowledge of the initial laser pulse is essential for data interpretation.

Parallel to the simulation work, the team advanced laser‑pulse diagnostics. A commercially available spatially resolved Fourier spectroscopy device, supplied by DESY, was employed to characterize the spatial and temporal structure of seed laser pulses. The diagnostics identified and corrected disturbances in the laser’s structure, improving the overall laser performance. The method proved effective in pinpointing the root causes of pulse distortions and is expected to become a standard tool for future high‑power laser facilities, including the European XFEL’s High Energy Density Science beamline and the planned LUXE experiment.

The collaboration combined expertise from both institutions: DESY provided the diagnostic hardware and experimental support, while the University of Hamburg contributed the theoretical and computational work. The consortium’s focus on new diagnostics for high‑intensity lasers ensured that the project’s outcomes would benefit a broad range of research fields. Despite the challenges posed by the COVID‑19 pandemic in early 2020, the project achieved all its key objectives, delivering both a significantly improved PIC code and a validated diagnostic technique that together enhance the reliability and reproducibility of laser‑driven experiments.