X-ray emission from laser-irradiated plane solid targets

Abstract

Plane solid targets (D₂, C, and Cu) were irradiated with Nd laser pulses of 5‐ns duration with energies of up to 50 J giving peak intensities up to 10¹⁵ W/cm² in the focal spot. The x‐ray emission of the plasma has been studied by using scintillators together with photomultipliers, x‐ray photodiodes, and an x‐ray pinhole camera. Detailed results are presented on the emitted x‐ray spectra up to 20 keV, on their angular dependence, on the conversion of laser energy into x‐ray energy, and on the spatial and temporal behavior of the electron density and temperature. The results are discussed with respect to the hydrodynamics, the absorption of laser light, and the energy transport occurring in the plasma. Two important features are heating at densities larger than critical yielding thermal pressures up to about 1 Mbar, and the development of a large cold plasma by strong lateral heat conduction. The hot electrons observed via the high‐energy tail of the x‐ray spectrum, were important for transporting the absorbed laser energy.