Ion acceleration from near-critical density aerogel and foam targets

Interaction of an intense laser pulse with near-critical density plasma makes a channel both in electron and then in ion density. The propagation of a laser pulse through such a channel is connected with the acceleration of electrons in the wake of a laser pulse and generation of strong moving electric and magnetic fields in the propagation channel. Upon exiting the plasma the magnetic field generates a quasi-static electric field that accelerates and collimates ions from a thin filament formed in the propagation channel. Two-dimensional Particle-in-Cell simulations show that a 100 TW laser pulse tightly focused on a near-critical density target is able to accelerate protons up to an energy of 250 MeV [1]. We present the experimental results on ion acceleration from silica aerogel targets with density of 40-100 mg/cm$^{3}$ and CHO foam targets with density of 3-45 mg/cm$^{3}$ using 100 TW, 30 fs laser pulses focused to intensities of 10$^{22}$ W/cm$^{2}$ at normal incidence. Detailed 2D-PIC computer modeling of these interactions will also be presented and compared to the experimental data. [1] S.S. Bulanov et al. PoP \textbf{17}, 043105 (2010). *Morehouse College