Intense ion beams accelerated by Petawatt-class lasers

The LLNL Petawatt Laser has achieved focussed intensities up to 6 x 10(20)W /cm(2), which has opened a new, higher energy regime of relativistic laser- plasma interactions in which the quiver energy of target electrons exceeds several MeV. Recent experiments revealed an intense, collimated beam of hig h-energy protons emitted normal to the rear surface of thin, solid targets. Up to 10(13) particles were emitted in a pulse less than 10 ps resulting i n a current in the MA regime. With an overall energy content of 30 J, up to 7% of the incident laser energy is converted into protons. The beam shows a broad particle energy spectrum with a sharp cut off above 55 MeV. Based o n our current understanding of the accelerating process, it may be possible to shape and focus the ion beam by using special target geometries. With their short pulse duration, high particle energy and large luminosity these beams are promising candidates in numerous applications, such as shor t-pulse injectors for large accelerators or as the ignitor for fast ignitio n ICF. Using intense proton beams the fast ignitor concept may become more attractive in heavy-ion fusion due to the possibility to work with indirect ly driven targets. Finally, the acceleration is not restricted to protons a nd using tailored target surfaces may allow acceleration of more massive io ns to similar energy per nucleon. (C) 2001 Elsevier Science B.V. All rights reserved.