Generation of laser-driven light ions suitable for fast ignition of fusion targets

The conditions for generating light ions (Li3+, Be4+, C6+ and Al13+) that have suitable energy deposition for the fast ignition of fusion targets via the interaction of an intense ultrashort pulse laser with thin targets (converters) are investigated theoretically. The laser and converter parameters are estimated assuming monoenergetic ions and a one-dimensional parallel plane geometry. Laser energy densities of 3-20 J μm-2 focused onto a spot with radius 30-100 μm are required to attain the necessary kinetic energies of 10-50 MeV/nucleon, depending on the type of ion. Self-consistent two-dimensional relativistic particle-in-cell simulations show that light ions can be accelerated to the required conditions with a conversion efficiency of laser energy into ions of up to 25%. Using the output ion energy distribution function, a one-dimensional energy deposition model calculates the conversion efficiency of ion beam energy into the core of the DT fuel. We conclude that fast ignition driven by all light ions under consideration can potentially be used as an alternative to electrons and protons.