title: Brunel-dominated proton acceleration with a few-cycle laser pulse.
abstract: Experimental measurements of backward accelerated protons are presented. The beam is produced when an ultrashort (5 fs) laser pulse, delivered by a kHz laser system, with a high temporal contrast (10(8)), interacts with a thick solid target. Under these conditions, proton cutoff energy dependence with laser parameters, such as pulse energy, polarization (from p to s), and pulse duration (from 5 to 500 fs), is studied. Theoretical model and two-dimensional particle-in-cell simulations, in good agreement with a large set of experimental results, indicate that proton acceleration is directly driven by Brunel electrons, in contrast to conventional target normal sheath acceleration that relies on electron thermal pressure.
authors.affiliation: Laboratoire d'Optique Appliquée, ENSTA-PARISTECH, CNRS, Ecole Polytechnique, UMR 7639, Palaiseau, France.
authors.forename: M
authors.initials: M
authors.lastname: Veltcheva
authors.forename: A
authors.initials: A
authors.lastname: Borot
authors.forename: C
authors.initials: C
authors.lastname: Thaury
authors.forename: A
authors.initials: A
authors.lastname: Malvache
authors.forename: E
authors.initials: E
authors.lastname: Lefebvre
authors.forename: A
authors.initials: A
authors.lastname: Flacco
authors.forename: R
authors.initials: R
authors.lastname: Lopez-Martens
authors.forename: V
authors.initials: V
authors.lastname: Malka