• X.H. Yang, C.L. Tian, Y. Yin, T.P. Yu
  National University of Defense Technology, Changsha, Hunan
• Y.Q. Gu
  Laser Fusion Research Center, China Academy of Engineering Physics, Mianyang
• S. Kawata, Y.Y. Ma
  Center for Optical Research and Education, Utsunomiya University, Utsunomiya
• F.Q. Shao
  National University of Defense Technology, Graduate School, Changsha
• H. Xu
  National University of Defense Technology, Parallel and Distributed Processing, Changsha
• M.Y. Yu
  Ruhr-Universität Bochum, Bochum

We have proposed a scheme for the generation of collimated proton beams from the interaction of an ultra-intense laser pulse with a rear hole target, which is studied by a 2.5D particle-in-cell (PIC) code PLASIM. When an ultraintense short laser pulse irradiates on such a target, the hot electrons will expand fast into the hole from the inner surfaces of the hole, and strong longitudinal sheath electric field and transverse electric field are produced. However, the plasma in the corners expand slower and be compressed strongly, and then a strong plasma jet is sprayed out from the corner with very high speed, which is just like what happened in armor piercing bullet due to the cumulative energy effect. The two jets extend into the hole and focus along the axis of the hole. At last, a high quality collimated proton beam can be obtained near the end of the hole along the propagation axis. It's found that the beam can propagate over a much longer distance without divergence. The effect of the hole diameter on the collimated proton beam is also investigated. Such target may serve as an important source for collimated proton beam in practical applications.