Inviter：李玉同 研究员（Tel：82648014）

Host：中国科学院光物理重点实验室

Abstract：

Laser-driven plasma accelerators offer compact sources of intense, ultrashort ion beams for applications ranging from radiobiology to neutron generation and high-energy-density physics. Meeting application requirements for particle energy, yield and reproducibility depends on establishing plasma conditions that enable efficient energy transfer from the laser to accelerated ions. Identifying and controlling the laser–target parameters that govern this transfer remains a central experimental challenge, particularly for petawatt and multi-petawatt facilities.

At HZDR's DRACO-PW facility, sustained efforts to understand and optimise the interaction have culminated in two major milestones: reproducible proton beams enabling the first in vivo tumour irradiation with laser-accelerated protons, and record proton energies of 150 MeV. These advances rely on laser-pulse characterisation at the interaction area under full operating conditions. Correlating these measurements with acceleration performance reveals how preceding laser light shapes the target plasma and guides targeted adjustments of laser and target parameters [1].

Comparative experiments at DRACO-PW and J-KAREN-P demonstrate how adapting target thickness to laser conditions enhances particle acceleration near the onset of relativistically induced transparency [2]. With only 22 J of laser energy on target, proton beams with reduced divergence and a spectrally distinct high-energy component well beyond 100 MeV could be produced. Combined hydrodynamic and three-dimensional particle-in-cell simulations reveal how target pre-expansion enables a cascade of acceleration mechanisms. Measurements of transmitted laser light provide an accessible indicator of the favourable interaction regime [3].

Together, these results provide practical strategies for improving proton acceleration across petawatt and multi-petawatt facilities. Linking diagnostics, physical understanding and experimental control establishes a foundation for online feedback and reproducible particle beams tailored to application requirements.

[1] T. Ziegler et al., Sci Rep 11, 7338 (2021).
[2] N.P. Dover and T. Ziegler et al., Light Sci. Appl. 12, 71 (2023).
[3] T. Ziegler et al., Nat. Phys. (2024).

About the speaker：

Dr Tim Ziegler is a postdoctoral researcher at Helmholtz-Zentrum Dresden-Rossendorf (HZDR), specialising in ultra-high-intensity laser–plasma interactions and plasma-based particle acceleration. His work combines advanced laser diagnostics, physical understanding and experimental control to improve ion-beam performance and reproducibility. He has participated and coordinated international experimental campaigns at high-power laser facilities worldwide. He earned his doctorate summa cum laude at TU Dresden in 2024 and has been recognised with several awards, including the John Dawson Thesis Prize and the Helmholtz Doctoral Prize. He currently leads HZDR's experimental contribution to Germany's Fusion2040 programme, developing platforms and diagnostics for high-energy-density physics and fusion research with academic and industrial partners.