Proton and ion acceleration by an ultra-shortpulse sub Peta-watt laser in deformed double-layer thin foils

Proton and ion acceleration by sub Peta-watt laser radiation in overdense p lasmas, especially for convex thin foils, is studied by 2D3V-PIC (Particle in Cell) numerical simulations. It is found that the target and pulse shape design is important for the acceleration of the charged particles. When a superintense laser pulse interacts with a thin slab of ablative overdense p lasma formed by the pre-pulse of the laser, its pondermotive pressure blows all the electrons away from a finite diameter spot on the slab. Consequent ly, the absorption efficiency of the laser is larger than 50%, but ion acce leration efficiency is small in the case of the material composed of atoms of large mass number, for example, Al. When the surface of the target is co ated with a rigid solid or clusters, ions are accelerated efficiently and g ain energies as high as 100 MeV, If hydrogen is coated on the back of the t hin Al foil, due to the Coulomb explosion of ions, protons are accelerated more efficiently than the hydrogen foil. (C) 2000 Elsevier Science B.V. All rights reserved.