High Energy Gain in Three-Dimensional Simulations of Light Sail Acceleration

The dynamics of radiation pressure acceleration in the relativistic light sail regime are analysed by means of large scale, three-dimensional (3D) particle-in-cell simulations. Differently to other mechanisms, the 3D dynamics leads to faster and higher energy gain than in 1D or 2D geometry. This effect is caused by the local decrease of the target density due to transverse expansion leading to a "lighter sail". However, the rarefaction of the target leads to an earlier transition to transparency limiting the energy gain. A transverse instability leads to a structured and inhomogeneous ion distribution.