Efficient acceleration of monoenergetic proton beam by sharp front laser pulse

Stable acceleration of relativistic ions by the radiation pressure of a superintense, circularly polarized laser pulse with sharp front is investigated by analytical modeling and particle-in-cell simulation. For foils with given density and thickness, the suitable steepness of the laser front is found to suppress instabilities and efficiently drive a stable monoenergetic ion beam. With a laser pulse of peak amplitude a(0)=200, a proton beam of energy about 10 GeV can be generated. The dynamics of the laser-compressed electron layer and the ions in the hole-boring stage are investigated. In the case studied, the ions initially in the middle of the target are found to be accelerated to the back surface of the target ahead of the other ions. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3544970]