Ultrafast, ultrashort, ultrahigh-peak-flux, and ultrahigh-dose-rate particle sources driven by high-intensity lasers

4U-PI: Ultrafast, Ultrashort, Ultrahigh-peak-flux, and Ultrahigh-dose-rate Particle sources driven by high-Intensity lasers, will advance Europe’s leadership in laser–plasma acceleration and its translation to biomedical and industrial impact. 4U-PI will develop and exploit ultrashort, ultrahigh-dose-rate ion and neutron bunches as novel radiation tools for users, setting new benchmarks in temporal precision and particle flux.By building on the plasma accelerator roadmap by Albert et al. (NJP 2021), 4U-PI will pioneer high-repetition-rate ion sources, hybrid acceleration schemes, compact beam transport, and advanced diagnostics, pushing the field toward user-ready platforms. In addition, it implements the biomedical roadmap by Hideghety et al. (EPJP 2025) by enabling breakthrough studies in ultrafast radiation biology, FLASH and microbeam therapy, and isotope production, supported by standardized dosimetry and radiobiology protocols.The consortium unites 12 partners from 6 countries led by Europe’s flagship infrastructures (ELI ERIC (Beamlines, ALPS), ELI-NP, and FAIR)—and large national infrastructures (GSI, CLF-UKRI, HZDR, ATOMKI) as the backbone for high-impact user experiments. Clinical, industrial and cross sectoral partners (PTC, MIRROTRON, Focused Energy, EIT Manufacturing) ensure translation into medicine, industry, and technology. Multi-modal imaging with laser-driven sources will extend the impact to industry and security applications, while AI/ML-enabled diagnostics will ensure reproducibility and open path to autonomous operation.Supported by 9 stakeholders 4U-PI is extending impact to clinics, industry, and innovation.Through this dual alignment with technological&biomedical roadmaps, 4U-PI will validate key exploitable results ranging from ultrafast beamlines to imaging and AI solutions. The outcomes will accelerate clinical translation, foster industrial competitiveness, and reinforce Europe’s strategic autonomy in ultrafast science&innovation.