Saturation of a low pump energy x-ray laser utilizing a transient inversion mechanism on the 3 p-3s transition at 32.63 nm in Ne-like Ti has been demonstrated. A close to saturation amplification was simultaneously achieved for the 3d-3p, Jϭ1→1 transition at 30.15 nm. Small signal effective transient gain coefficients of gϳ46 and ϳ35 cm Ϫ1 and gain-length products of 16.7 and 16.9 for these lines were obtained. Experiments demonstrate that it is possible to achieve saturated laser action in a transient regime with Ne-like Ti for a pump energy as low as ϳ5 J.

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Saturated operation of a laser at a wavelength shorter than 6 nm is demonstrated. The output of the Ni-like Dy laser at 5.86 and 6.37 nm, pumped by the VULCAN 1.05-m Nd-glass laser in a 75-ps double-pulse configuration at 2ϫ10 13 W cm Ϫ2 peak irradiance, is measured experimentally and studied theoretically using a rate equation and one-dimensional amplified spontaneous-emission model. The experimental results and modeling show that, upon saturation, the output intensities from the lower gain lasing transition at 6.37 nm decrease with increasing gain medium length. This is a different signature of gain saturation for Ni-like lasers and is desirable for applications, as it shows that one lasing transition will dominate with Ni-like lasers in saturation. ͓S1050-2947͑99͒50901-3͔PACS number͑s͒: 42.55.Vc, 42.55.Ah RAPID COMMUNICATIONS R48PRA 59 R. SMITH et al.

The time-integrated x-ray emission from a hot, dense iron plasma has been recorded. The iron plasma was created when a target with a 1000-Å-thick iron layer buried beneath 1000 Å of plastic was irradiated by a 300 fs pulse of 249 nm laser light at an intensity of approximately 1017 W cm−2. Two models have been used to construct a synthetic x-ray spectrum. The first employs detailed, spectroscopically accurate atomic data and the second uses a local thermodynamic equilibrium opacity model. The detailed model shows fairly good agreement with experiment whereas the opacity model only shows agreement in the gross features.

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