Laser-Ion Lens and Accelerator
Tianhong Wang, Vladimir Khudik, Gennady Shvets
Abstract
Generation of highly collimated monoenergetic relativistic ion beams is one of the most challenging and promising areas in ultraintense laser-matter interactions because of the numerous scientific and technological applications that require such beams. We address this challenge by introducing the concept of laser-ion lensing and acceleration. Using a simple analogy with a gradient-index lens, we demonstrate that simultaneous focusing and acceleration of ions is accomplished by illuminating a shaped solid-density target by an intense laser pulse at ∼10^{22} W/cm^{2} intensity, and using the radiation pressure of the laser to deform or focus the target into a cubic micron spot. We show that the laser-ion lensing and acceleration process can be approximated using a simple deformable mirror model and then validate it using three-dimensional particle-in-cell simulations of a two-species plasma target composed of electrons and ions. Extensive scans of the laser and target parameters identify the stable propagation regime where the Rayleigh-Taylor-like instability is suppressed. Stable focusing is found at different laser powers (from a few to multiple petawatts). Focused ion beams with the focused density of order 10^{23} cm^{-3}, energies in access of 750 MeV, and energy density up to 2×10^{13} J/cm^{3} at the focal point are predicted for future multipetawatt laser systems.