Plasma interactions in laser irradiated semi-cylindrical cavities studied with soft x-ray interferometry using a capillary discharge laser

摘要

Soft x-ray interferometry was used to measure the evolution of dense converging plasmas created by laser irradiation of 500 μm diameter semi-cylindrical carbon targets. Optical laser pulses with an intensity of ～1 × 10~(12) W cm~(-2) and 120 ps duration were used to heat the surface of the cavities. The dense plasma formed expands from the walls converging slightly off the semi-cylinder's axis, giving rise to a bright localized high density plasma region. A sequence of electron density maps were measured using a 46.9 nm wavelength tabletop capillary discharge soft x-ray laser probe and a amplitude division interferometer based on diffraction gratings. The measured density profiles are compared with simulations conducted using the multi-dimensional hydrodynamic code HYDRA. The benchmarked model was then used to simulate particle trajectories which reveal that the increase in electron density near the axis is mainly the result of the convergence of plasma that originated at the bottom of the groove during laser irradiation.