Time-Resolved Soft–X-Ray Spectra from Laser-Heated Cavities

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Abstract
The interior of gold spherical cavities ((250 ÷ 1000) μm) was irradiated with 300 ps pulses from the Asterix III iodine laser (λ = 1.3 μm). The spectrum, in the range of (10 ÷ 100) Å, of the radiation emanating from the interior of the laser-heated cavities has been measured for average laser intensities between (2 1012 ÷ 3 1013) W/cm2. Temporally resolved spectra were obtained using a free standing transmission grating coupled to a soft–X-ray streak camera. For the interpretation of the spectra an atomic-physics code based on the "average ion" approximation has been developed. The main features of the experimentally obtained spectra can be reproduced if one takes the density and temperature profiles corresponding to the radiation heat wave as input to the atomic-physics code. It is concluded that the thermal radiation plays an important role in determining the hydrodynamics and in particular the temperature in the interior of the cavity.