Towards radiation pressure acceleration of protons using linearly polarized ultrashort petawatt laser pulses

TL;DR

This study demonstrates the transition from target normal sheath acceleration to radiation pressure acceleration in proton beams using linearly polarized ultrashort laser pulses, achieving 45 MeV protons and predicting 200 MeV at higher intensities.

Contribution

First experimental demonstration of radiation pressure acceleration with linearly polarized laser pulses and analysis of proton energy scaling with target thickness and laser intensity.

Findings

Achieved 45 MeV proton energy with 10-nm targets at 3.3x10^20 W/cm^2.

Observed transition from sheath to radiation pressure acceleration.

Predicted 200 MeV proton energy at 1.5x10^21 W/cm^2.

Abstract

Particle acceleration using ultraintense, ultrashort laser pulses is one of the most attractive topics in relativistic laser-plasma research. We report proton/ion acceleration in the intensity range of 5x1019 W/cm2 to 3.3x1020 W/cm2 by irradiating linearly polarized, 30-fs, 1-PW laser pulses on 10- to 100-nm-thick polymer targets. The proton energy scaling with respect to the intensity and target thickness was examined. The experiments demonstrated, for the first time with linearly polarized light, a transition from the target normal sheath acceleration to radiation pressure acceleration and showed a maximum proton energy of 45 MeV when a 10-nm-thick target was irradiated by a laser intensity of 3.3x1020 W/cm2. The experimental results were further supported by two- and three-dimensional particle-in-cell simulations. Based on the deduced proton energy scaling, proton beams having an energy of ~ 200 MeV should be feasible at a laser intensity of 1.5x1021 W/cm2.