2 dimensional analysis of a NOVETTE laser generated stress-impulse experiment
The NOVETTE Laser was used to irradiate aluminum disks at fluences of 100 to 20,000 J/cm/sup 2/. Besides the intrinsic interest in the coupling coefficient for .53 micron light in highly 1D (lns) interactions, the shots were used to qualify diagnostics to be used in other tests. The coupling coefficient data has been analyzed with respect to 1D calculations by Bookless. The results indicate that the experiments generate twice the impulse calculated by a 1D model at least at 12,000 J/cm/sup 2/. 2D calculations predict an impulse of 16. 3 ktaps vs a measured 12.5 ktaps at 12,000 J/cm/sup 2/. 1D calculations predict 6.3 ktap. 46% of the 2D impulse is from plume reradiation to target surface outside the spot at times much later than the initial interaction time of 1 ns. The 2D calculation predicted a peak stress of 90 kbars at a depth of 1.5 mm into the target. Observations using a Manganin gage were 68 kbars. The ratio of calculated to observed stress is about the same as the ratio of calculated to observed impulse. The difference in stresses may be due to a lack of material strength in the EOS for LASNEX. Alternatively, an error in the estimate of the gauge depth by as little as .2 mm can also explain the stress discrepancy as could an absorption of 75% of the incident light from that calculated. At this time, however, there is a 50% apparent uncertainty in the calculation of impulse at 10 terawatts/cm/sup 2/ on aluminum when 2D effects are accounted for. 7 figs.
- Research Organization:
- Lawrence Livermore National Lab., CA (USA)
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 6159373
- Report Number(s):
- UCRL-21167; ON: DE89009909
- Country of Publication:
- United States
- Language:
- English
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