Double-relativistic-electron-shell laser proton acceleration
  A new laser-proton acceleration structure combined by two relativistic electron shells, a suprathermal electron shell and a thermal electron cloud is proposed for $a\gtrapprox80\sigma_0$, where a is the normalized laser field and $\sigma_0$ is the normalized plasma surface density. In the new region, a uniform energy distribution of several GeV and a monoenergetic hundreds-of-MeV proton beam have been obtained for $a=39.5$. The first relativistic electron shell maintains opaque for incident laser pulse in the whole process. A monoenergetic electron beam has been generated with energy hundreds of MeV and charge of hundreds of pC. It is proposed a stirring solution for relativistic laser-particle acceleration. 
Yongsheng Huang, Naiyan Wang, Xiuzhang Tang, Yijin Shi, Zhang Shan
physics.plasm-ph physics.acc-ph