The ratio of the EUV radiation energy flux under the Planck distribution to the blackbody radiation , which is considered as a limiting EUV conversion efficiency of an optically thick and stationary plasma.
Schematic picture of radiation emission from a laser-produced plasma. Every surface element of a spherical chamber vertically receive the EUV light from a tiny plasma volume at the center.
Planck opacity coefficients for Eq. (19) under the units (keV) and ; the data points are taken from Table 3 in Ref. 25 and the solid lines are fitted to those data, the formulas of which are given in the main text.
Normalized conversion efficiency as a function of the initial thickness of a tin foil. Comparison between the experiment and the model shows that the EUV optical thickness is significantly larger than the overall Planck optical thickness by a factor of about 10.
Example of the model calculation. The energy fluxes , , , are normalized by their sum . Fixed parameters are , . Comparison with the experimental results under the same parameters can be seen in Fig. 6.
Comparison of the conversion efficiency between the model and the experiments in use of spherical targets. The detail on the model curve is given in Fig. 5.
Summary of dependence of on , , and for planar tin targets. The symbols and the curves stand for the experiments and the model, respectively. E-MON was used for the measurements with , while TGS-CCD with and .
Comparison of the conversion efficiency between the model (the curves) and the experiments (the symbols) in use of planar xenon targets. Fixed parameters are and
Numerical scalings on the maximum conversion efficiency , and corresponding quantities for the laser intensity , the average ionization state , and the temperature , when and are fulfilled. Fixed parameters are (Sn), , , and .
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