High efficiency of laser energy conversion with Cavity Pressure Acceleration

Cavity Pressure Acceleration (CPA) is a technique for accelerating dense plasma streams by utilizing laser-generated plasmapressure within a spatially confined region. This approach has been proposed as an alternative to the classical ablativeacceleration of plasma. Initially, the primary goal of this approach was to create a dense plasma stream (a theoretical macroparticle delivering energy/momentum) suitable for experiments related to Impact Fast Ignition. In recent experimentalsessions, we used targets equipped with cavities lined with deuterated polyethylene (CD2) foils and powder. These targets wereirradiated with a 1ω PALS sub-kilojoule, low-contrast laser beam (λ1PALS =1315 nm), focused to an intensity of 1−2×1016 W/cm2 within a 250−350 ps pulse. The scheme has proven to be highly efficient in converting laser energy into high-energy interactionproducts, such as high-density plasma streams and protons. We observed neutron yields among the highest achieved to datein Deuterium-Deuterium laser-induced experiments, even when compared to facilities with lasers operating at significantlyhigher energies and intensities. 1D hydrodynamic code used to simulate plasma parameters in the targets confirmed the highpotential of the method, regardless of the driving laser wavelength.