Results of Pulse-Scaling Experiments on Rapid-Growth DKDP Triplers Using the Optical Sciences Laser at 351 nm
Results are reported from recently performed bulk-damage, pulse-scaling experiments on DKDP tripler samples taken from NIF-size, rapid-growth boule BD7. The tests were performed on LLNL's Optical Sciences Laser. A matrix of samples was exposed to single shots at 351 mn (3 {omega}) with average fluences from 4 to 8 J/cm{sup 2} for pulse durations of 1, 3 and 10 ns. The damage sites were scatter-mapped after testing to determine the damage evolution as a function of local beam fluence. The average bulk damage microcavity (pinpoint) density varied nearly linearly with fluence with peak values of approximately 16,000 pp/mm{sup 3} at 1 ns, 10,000 pp/mm{sup 3} at 3 ns and 400 pp/mm{sup 3} at 10 ns for fluences in the 8-10 J/cm{sup 2} range. The average size of a pinpoint was 10(+14,-9) {micro}m at 1 ns, 37 {+-} 20 {micro}m at 3 ns and {approx} 110 {micro}m at 10 ns, although all pulse durations produced pinpoints with a wide distribution of sizes. Analysis of the pinpoint density data yielded pulse-scaling behavior of t{sup 0.35}. Significant planar cracking around the pinpoint as was observed for the 10 ns case but not for the 1 and 3 ns pulses. Crack formation around pinpoints has also been observed frequently for Zeus ADT tests at {approx}8 ns. The high pinpoint densities also lead to significant eruption of near-surface bulk damage. Measurements of the damage site area for surface and bulk gave ratios (A{sub surf}/A{sub bulk}) of 2:1 at 1 ns, 7:1 at 3 ns and 110:1 at 10 ns. Maximum aperture averaged transmission losses on the order 15 percent have been measured by photometry for the worst damage at 1 and 3 ns for beam fluences in the 8-10 J/cm{sup 2} range. Analysis of this data yielded a pulse-scaling behavior of t{sup 0.25} for the obscured area. It was also determined that the crystals used in this test would survive unconditioned exposure to 4 J/cm{sup 2} shots on the NIF laser and still meet the obscuration requirement of 0.1%.
- Research Organization:
- Lawrence Livermore National Laboratory (LLNL), Livermore, CA
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 15013175
- Report Number(s):
- UCRL-JC-139623
- Country of Publication:
- United States
- Language:
- English
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