Stable monoenergetic ion acceleration by a two color laser tweezer
  In the past decades, the phenomenal progress in the development of
ultraintense lasers has opened up many exciting new frontiers in laser matter
physics, including laser plasma ion acceleration. Currently a major challenge
in this frontier is to find simple methods to stably produce monoenergetic ion
beams with sufficient charge for real applications. Here, we propose a novel
scheme using a two color laser tweezer to fulfill this goal. In this scheme,
two circularly polarized lasers with different wavelengths collide right on a
thin nano-foil target containing mixed ion species. The radiation pressure of
this laser pair acts like a tweezer to pinch and fully drag the electrons out,
forming a stable uniform accelerating field for the ions. Scaling laws and
three-dimensional particle-in-cell simulations confirm that high energy
(10-1000 MeV) high charge ($\sim 10^{10}$) proton beams with narrow energy
spread ($\sim4\%-20\%$) can be obtained by commercially available lasers. Such
a scheme may open up a new route for compact high quality ion sources for
various applications.
