Topic/Type: 1.3 High intensity Laser Plasma Interaction, Poster

### High energy proton beam generation with superintense laser pulses: solid target optimization with FFT base parallel PIC code

A. A. Gonoskov

Institute of Applied Physics RAS, Nizhny Novgorod, Russia

A process of high intensity (10$\small ^{21}$ ? 10$\small ^{22}$ W/cm$\small ^2$) femtosecond laser pulse interaction with solid-density plasma structures was investigated in the context of high energy protons beam generation. With use of our new parallel FFT based PIC code we observed and studied effects of longitudinal electric field formation which can accelerate protons and light ions. As long as most of important applications, such as hadrontherapy, require several hundreds MeV proton beams with small energy and angular spread we divided the process of proton acceleration into two stages. The first stage provides initial formation of a slightly accelerated proton bunch with small energy and space spread and the second one provides its further acceleration without substantial energy and angular spreading. For the first stage it was proposed a regime of relativistically induced slab transparency (RIST) which allows to generate a several tens MeV proton beam from the process of the laser pulse interaction with a couple of properly spaced apart thin slabs: a proton containing layer as a proton source and a metal foil as an acceleration layer. In the regime it is used only the leading part of the laser pulse without substantial action on the rest part which can be used for the further proton beam acceleration. For the second stage we used an effect of edge electric field which appears on the metal foil edge due to lateral electron transport and ejection in the process of inclined irradiation by the laser pulse with relativistic intensity. To concentrate laser pulse energy and generate maximum edge field we proposed cone-like thin foil structure with a microscale tube on the peak. Our simulations show that such structure can provide generation and stable acceleration of proton beam without substantial energy and angular spread up to few hundreds MeV energies. It should be noted that the laser and target parameters used in the simulations are presently easily achievable in many laboratories, so that this results should be useful for the experimental research on proton beam generation.