Periodic spectral modulations of low-energy, low-charge-state carbon ions accelerated in an intense laser–solid interaction

Abstract

We report experimental observation of periodic modulations in the energy distribution of C1+ ions dominantly accelerated in the interaction of a 15 μm thick tape target with intense laser pulses of intensities ∼1018 W/cm2 in a defocused configuration. Moreover, the influence of laser intensity on the acceleration of low- and high-charge-state species of carbon ions is observed. Two-dimensional (2D) particle-in-cell simulations elucidate the dynamics of ionization-dependent acceleration of different species in different laser focusing conditions. By comparison, 1D simulations suggest that the modulations of C1+ ions are due to the longitudinal recirculation dynamics of hot electrons in the target, which modulates the sheath field for acceleration of C1+ ions.