Collisionless shock acceleration of narrow energy spread ion beams from mixed species plasmas using 1 $\mu$m lasers

TL;DR

This paper demonstrates the generation of narrow energy spread ion beams via collisionless shock acceleration using a 1 μm laser interacting with a controlled plasma profile, achieving energies up to 18 MeV per atomic mass unit.

Contribution

It introduces a method to produce narrow energy spread ion beams from mixed species plasmas using shock acceleration with a 1 μm laser and plasma profile control.

Findings

Produced ion beams with 10-20% energy spread and 10-18 MeV/a.m.u. energies.

Particle-in-cell simulations confirm experimental results and suggest further optimization.

Plasma profile control influences the beam charge-energy trade-off.

Abstract

Collisionless shock acceleration of protons and C$^{6+}$ ions has been achieved by the interaction of a 10$^{20}$ W/cm$^2$, 1 $\mu$m laser with a near-critical density plasma. Ablation of the initially solid density target by a secondary laser allowed for systematic control of the plasma profile. This enabled the production of beams with peaked spectra with energies of 10-18 MeV/a.m.u. and energy spreads of 10-20$\%$ with up to 3x10$^9$ particles within these narrow spectral features. The narrow energy spread and similar velocity of ion species with different charge-to-mass ratio are consistent with acceleration by the moving potential of a shock wave. Particle-in-cell simulations show shock accelerated beams of protons and C$^{6+}$ ions with energy distributions consistent with the experiments. Simulations further indicate the plasma profile determines the trade-off between the beam charge and energy and that with additional target optimization narrow energy spread beams exceeding 100 MeV/a.m.u. can be produced using the same laser conditions.