[(a)–(c)] Typical emission spectra for the three wavelength ranges studied.
Simulated spatiotemporal evolution of . Inset: calculations from the Colombant and Tonon (Ref. 31) fractionial ion densities model for the laser intensity used .
Simulated spatiotemporal evolution of . Inset: image from the ICCD camera at .
Spatial profile of from MEDUSA and profile generate by Singh and Narayan code using MEDUSA inputs for the same time index.
Spatial profiles from the adiabatic model for various time increments. The full extent of the profile is not plotted for later time histories for clarity. Inset: ICCD image of the plasma at .
Fully simulated profile over the complete space-time profile of EUV emission from the plasma plume, combining the plasma generation phase (MEDUSA code) with the free expansion phase (Singh and Narayan).
profile calculated using the spatiotemporal constant value from the analytical model by Phipps and Dreyfus for Al VIII/VII (24.8/26.1 nm) line ratio.
profile calculated using the simulated profile for Al VIII/VII (24.8/26.1 nm) line ratio.
Peak ionization temperatures for each space-time resolved ion-to-atom intensity ratio calculation versus the energy difference between the upper levels of the two ions used. There were no ion stages below Al V and thus the first group of intensity ratios were Al VI/V (see Table II) for which there were 12 different pairs. The minimum energy difference between the upper levels in this case was −3.96 eV and thus including the ionization energy of the lower stage (Al V, 153.87 eV) gave the observed energy axis starting at . The highest stage observed was Al X. The maximum energy difference in the upper levels for the Al X/IX ratios was −19.89 eV and thus (including the ionization energy of Al IX (330.23 eV)) this gave 310.3 eV as the maximum extent of the energy axis above. The gray dashed line is the best linear fit, while the dashed colored lines represent the variation due to maximum/minimum fitting error. Inset: displays the space-time coordinate of the calculated peak for each ion pair. The majority of peaks were located just before the peak of the laser pulse (at ), approximately from the target surface. Transitions to the ground state have been labeled.
Ratio of integrated area between two equally charged ions (Al VII (24.0/23.9) nm). The peak temperatures for all intensity ratios utilizing successively charged ion pairs were observed to be located in the first “quadrant” of the space-time profile, here labeled “ peaks.” In contrast the largest deviations from the expected ratio were observed to be located in the geometric center of the space-time profile, labeled “primary region of significant self absorption.”
Peak , corrected and uncorrected for self absorption. The original trend fitted to Fig. 9 is also shown, as is the new fits to the corrected data. These two linear fits to the new data are shown separately for cases were the upper line in Table III is adjusted (and this is then applied to intensity ratios in Table II) and separately were the lower line in Table III is adjusted and this adjustment is then applied to the intensity ratios in Table II. These two linear fits thus represent the upper and lower range of corrections to various lines in our data.
MEDUSA code inputs.
The line ratios used for the calculations. The difference in the transition energies of the upper level of each ion, with and without the ionization energy, and the calculated peak ionization temperature for each ion pair is also displayed. A total of 55 pairs of ion intensity ratios were calculated. (Emission lines which transit to ground level are underlined.)
Table of values used for self absorption correction analysis. First column: line ratio used for equally charged, nontransiting to ground state ions. Second column: expected integrated intensity ratio via upper level degeneracy ratio. Third column: measured integrated intensity ratio, at the averaged space-time coordinate of and . Fourth column: ratio of measured line widths. Fifth column: factor change in peak intensity of the upper line after correction. Sixth column: factor change in peak intensity of the lower line after correction.
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