The 6th International Conference on Matter and Radiation at Extremes (ICMRE2023)

244 / 2023-04-19 14:43:27

Steady regime of radiation pressure acceleration with foil thickness adjustable within micrometers under 10-100 PW laser

Fundamental Physics at Extreme Light > Particle Acceleration-I

Experiments failed to observe quasi-monoenergetic GeV-scale protons predicted by the radiation pressure acceleration (RPA) theory, because the matched thickness is too small, e.g., several nm to 100 nm with the laser intensity available in laboratory. Such thin foil is hard to bear insufficient laser contrast and foil surface roughness, and we here find that there is an upper-limit thickness, which is lower than or around the matching thickness with 10¹⁹-10²² Wcm^-2 laser intensities used in the experiments, which causes inefficient and unsteady acceleration. As the laser intensity is enhanced by one to two orders of magnitude with the coming 10-100 PW laser facilities, the upper-limit thickness significantly exceeds the matching thickness and therefore the acceleration becomes efficient. In the new regime, the experiment could adopt the thickness in a larger range of micrometers, resulting in both efficient and steady acceleration. Particle-in-cell simulation shows that multi-GeV quasi-monoenergetic proton beams can be steadily generated. This work predicts that near future RPA experiments with 10-100 PW laser facilities will enter a new regime with the adjustable and large-range target thickness for steady acceleration.

Experiments failed to observe quasi-monoenergetic GeV-scale protons predicted by the radiation pressure acceleration (RPA) theory, because the matched thickness is too small, e.g., several nm to 100 nm with the laser intensity available in laboratory. Such thin foil is hard to bear insufficient laser contrast and foil surface roughness, and we here find that there is an upper-limit thickness, which is lower than or around the matching thickness with 10¹⁹-10²² Wcm^-2 laser intensities used in the experiments, which causes inefficient and unsteady acceleration. As the laser intensity is enhanced by one to two orders of magnitude with the coming 10-100 PW laser facilities, the upper-limit thickness significantly exceeds the matching thickness and therefore the acceleration becomes efficient. In the new regime, the experiment could adopt the thickness in a larger range of micrometers, resulting in both efficient and steady acceleration. Particle-in-cell simulation shows that multi-GeV quasi-monoenergetic proton beams can be steadily generated. This work predicts that near future RPA experiments with 10-100 PW laser facilities will enter a new regime with the adjustable and large-range target thickness for steady acceleration.