Ultra-intense laser-accelerated ion beams for high-gain inertial fusion: the effect of the ion mass on the beam properties

This paper presents the results of detailed numerical studies of the properties of ion beams generated by a laser from targets with various atomic numbers under conditions relevant for ion fast ignition (IFI) of inertial fusion. The interaction of a 200 kJ 1 ps infrared (1.05 mu m) laser with Li, C, Al, Ti, Cu and CH2 flat targets with the same areal mass density was numerically simulated using an advanced 2D3V particle-in-cell code. For each target, a set of ion beam characteristics important for IFI was determined. A detailed quantitative comparison of the IFI-relevant parameters of Li, C, Al, Ti and Cu ion beams and the proton beam (from the CH2 target) was made. The laser-accelerated Cu ion beam was found to achieve significantly higher values of beam intensity, fluence and 'useful' energy (for IFI), having a smaller angular divergence and a narrower energy spectrum than the beam of light ions or protons. Thus, it is shown for the first time that laser-accelerated heavy ion beams can achieve IFI-relevant parameters higher than light ion or proton beams and can potentially meet IFI requirements.