17 / 2026-03-03 14:47:19

Proton acceleration in nanometer-thick polymer foils irradiated by ultrahigh-contrast petawatt laser pulses

multi-petawatt laser,laser driven proton acceleration

极端条件下的基础物理 > 辐射与高能粒子产生

We report on the experimental investigation on proton acceleration performed with the 4-PW laser facility at Center for Relativistic Laser Science (CoReLS). Terawatt or petawatt lasers can introduce longitudinal electric fields stronger than TV/m inside plasmas and accelerate protons. We explored the physics of efficient proton acceleration in a nanometer-thick polymer foil irradiated by an ultrahigh-contrast petawatt laser pulse [1]. The longitudinal proton dynamics were experimentally investigated, indicating the acceleration of protons to over 90 MeV by a novel scheme associated with the sheet crossing mechanism [2]. Experimental evidence, such as a ringlike distribution of the most energetic protons and a reduced proton cutoff energy from diamondlike carbon foils, revealed that the highest-energy protons originated from the target forepart. These protons can be accelerated in two cascading stages of radiation pressure during the laser driving and Coulomb repulsion after the end of the laser pulse. The sheet crossing process is essential for linking these two stages and ensuring efficient proton acceleration. We further demonstrated that, using a conduction-restricted nanometer polymer foil with a finite lateral size, the Coulomb repulsion stage could be enhanced since the conduction of cold electrons was restricted and a strong Coulomb field was established by carbon ions. As a result, the generation of protons with a cutoff energy exceeding 110 MeV was achieved with the conduction-restricted nanometer foil [3]. Our achievement paves the road to enhance proton energy further, well meeting the requirements for diverse applications, through a controllable acceleration process using well-designed nano- or micro-structured targets.