Ultraintense Laser-Driven Nonthermal Acceleration of Charged Particles in the Near-QED Regime

Here, we have studied the nonthermal acceleration of energetic electrons/protons under the near-QED regime by extending the laser intensity beyond 1023 W/cm2 based on a two-dimensional particle-in-cell simulation. The radiation-reaction (RR) effect plays a critical role and brings a quantum stochastic effect to the charged-particle acceleration process. Background electrons in plasma are accelerated in an intense laser field to several GeVs with strong oscillations and thus radiate γ-ray photons. The emitting γ-photons have a broad energy spectrum with maximal energy up to 3 GeV and result in radiation-reaction trapping of the electrons, forming a relativistic plasma bunch in the plasma channel. The accumulation of electrons and protons produces a charge-separation field for the acceleration/deceleration of charged particles. The accelerated electrons have a nonthermal spectrum with a power-law index of 1.5 with a laser intensity 1023 W/cm2 lower than that in the non-QED regime. As the laser intensity further increases over 1024 W/cm2, the power-law index further drops to 1.2. Moreover, the energy spectrum of accelerated protons has a nonthermal distribution with a power-law index of 0.7, which is much lower than that of electrons in the near-QED regime.