Diagnostics for studies of absorption and energy transfer process features in low-density porous targets irradiated with powerful laser pulses

A diagnostic methodology for studies of powerful laser pulse interaction with a porous material of low average density in conditions of interest for advanced inertial confinement fusion targets is discussed. These diagnostics were used in experiments with a powerful 1 mu m Nd:laser beam incident upon ''agar-agar'' targets (C14H18O7)(n) Of different average density from I x 10(-3) to 5 x 10(-3) g/cm(3) and thickness from 100 to 1000 mu m with and without thin aluminium layers (0.5-6 mu m) on the front and rear surfaces. Intensity at the focal spot area 100 mu m in diameter ranged from 10(13) to 10(14) W/cm(2). It is shown that it is possible to estimate the longitudinal and transverse dimensions of the laser-plasma interaction region and to obtain the plasma dynamics data by recording: the visible and IR radiation at the rear side of illuminated targets with streak camera; x-ray images with filtered pin holes; and multiframe shlieren- and shadowgraphy snapshots (0.3 ns laser pulses at 0.53 mu m wavelength have been used). (C) 1997 American Institute of Physics.