MODEL-CALCULATIONS OF XUV GAIN FROM LASER-IRRADIATED ALUMINUM RIBBONS .2.

For pt.I see ibid., vol.14, p.1525 (1981). Recent experimental observations of gains in the near XUV ( lambda approximately 182 AA) encourage the application of the recombination scheme to shorter wavelengths. The authors discuss model calculations of gain at 38.7 AA, in laser-irradiated ribbons, based on the Al XIII Halpha transition. The calculations used a more accurate description of the atomic physics than the earlier study. The scaling of the optimum gain with the ribbon composition and initial width is examined. The modelling indicates that an experimental demonstration of significant gain at 38.7 AA is possible with current technology provided about 10% of the pump laser energy, can be coupled to the target. The simulations including the atomic physics used the self-similar description for spatially isothermal expansions to evaluate the development of the bulk properties of the target. The authors have examined the validity of this approximation using a two-dimensional fluid code assuming constant ionisation. They conclude that the targets are well 'burnt through' in the conditions required for an experimental demonstration of gain at 38.7 AA, and that the atomic calculations should be associated with ribbons having half the width originally assumed but the same specific energy at the end of the pumping pulse.