Laser–plasma acceleration of quasi-monoenergetic carbon ion beams with the “peeler” scheme

We introduce a scheme aiming at the generation of quasi-monochromatic carbon ion bunches from laser–solid interaction. The proposed scheme is an extension of the “peeler” acceleration originally proposed for proton acceleration, which involves irradiating the narrow (sub-micrometer) side of a tape target. This results in the generation of a surface plasma wave and the subsequent acceleration of a proton bunch with high peak energy, quasi-monochromaticity, low energy bandwidth, and low divergence by the electrostatic field induced at the target rear. Up to now, the higher-Z (e.g., carbon) ion bunches obtained with the peeler scheme have been found to exhibit an exponentially decaying thermal-like energy spectrum. To achieve a low energy bandwidth, we place a mass-limited carbon structure at the rear of the target. Using 3D particle-in-cell simulations, we show that a quasi-monochromatic carbon bunch can indeed be obtained. With a multi-PW laser pulse, 108 carbon ions with peak energy ∼110 MeV/u and with a divergence of 20° in the vertical plane and ∼1° in the horizontal plane can be generated. The quasi-monochromaticity, together with the low duration of the beam and in combination with the versatility of high-power laser facilities, should make this scheme attractive for practical applications such as heavy ion cancer therapy and higher-resolution diagnostics of extreme plasma states.