a1 Institut für Theoretische Physik I, Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany
a2 Department of Physics, National University of Defense Technology, Changsha, China
We study proton acceleration from a foil target with a transversely varying density using multi-dimensional Particle-in-Cell (PIC) simulations. In order to reduce electron heating and deformation of the target, circularly polarized Gaussian laser pulses at intensities on the order of 1022 Wcm−2 are used. It is shown that when the target density distribution fits that of the laser intensity profile, protons accelerated from the center part of the target have quasi-monoenergetic spectra and are well collimated. In our two-dimensional PIC simulations, the final peak energy can be up to 1.4 GeV with the full-width of half maximum divergence cone of less than 4°. We observe highly efficient energy conversion from the laser to the protons in the simulations.
(Received May 24 2009)
(Accepted July 29 2009)
c1 Address correspondence and reprint requests to: Alexander Pukhov, Institut für Theoretische Physik I, Heinrich-Heine-Universität Düsseldorf, 40225 Düsseldorf, Germany. E-mail: email@example.com