Surface contamination initiated laser damage

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We are engaged in a comprehensive effort to understand and model the initiation and growth of laser damage initiated by surface contaminants. This includes, for example, the initial absorption by the contaminant, heating and plasma generation, pressure and thermal loading of the transparent substrate, and subsequent shockwave propagation, ``splashing`` of molten material and possible spallation, optical propagation and scattering, and treatment of material fracture. The integration use of large radiation hydrodynamics codes, optical propagation codes and material strength codes enables a comprehensive view of the damage process The following picture of surface contaminant initiated laser damage is emerging from our ... continued below

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12 p.

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Feit, M.D.; Rubenchick, A.M. & Faux, D.R. January 24, 1997.

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Description

We are engaged in a comprehensive effort to understand and model the initiation and growth of laser damage initiated by surface contaminants. This includes, for example, the initial absorption by the contaminant, heating and plasma generation, pressure and thermal loading of the transparent substrate, and subsequent shockwave propagation, ``splashing`` of molten material and possible spallation, optical propagation and scattering, and treatment of material fracture. The integration use of large radiation hydrodynamics codes, optical propagation codes and material strength codes enables a comprehensive view of the damage process The following picture of surface contaminant initiated laser damage is emerging from our simulations. On the entrance optical surface, small particles can ablate nearly completely. In this case, only relatively weak shockwaves are launched into the substrate, but some particulate material may be left on the surface to act as a diffraction mask and cause further absorption. Diffraction by wavelength scale scattering centers can lead to significant intensity modulation. Larger particles will not be completely vaporized. The shockwave generated in this case 1642is larger and can lead to spallation of contaminant material which then may be deposited in the substrate. A gaseous atmosphere can lead to radiation trapping with concomitant increases in temperature and pressure near the surface. In addition, supersonic ionization waves in air may be generated which greatly extend the plasma plume spatially and temporally. Contaminants on the exit optical surface behave differently. They tend to heat and pop off completely in which case significant damage may not occur. Since plasma formed at the interface of the optic and absorbing particle is confined, much stronger pressures are generated in this case. Imaging of contaminants resulting in ``writing`` a diffraction pattern on the exit surface due to contamination on the entrance surface has been observed experimentally and predicted theoretically. Such imprinted damage regions can seed damage from subsequent pulses.

Physical Description

12 p.

Notes

INIS; OSTI as DE97052096

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  • 2. annual solid state lasers for applications to inertial confinement fusion (ICF), Paris (France), 22-25 Oct 1996

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  • Other: DE97052096
  • Report No.: UCRL-JC--126326
  • Report No.: CONF-9610225--25
  • Grant Number: W-7405-ENG-48
  • Office of Scientific & Technical Information Report Number: 321864
  • Archival Resource Key: ark:/67531/metadc685740

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Office of Scientific & Technical Information Technical Reports

Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

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  • January 24, 1997

Added to The UNT Digital Library

  • July 25, 2015, 2:20 a.m.

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  • Feb. 23, 2016, 12:36 p.m.

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Feit, M.D.; Rubenchick, A.M. & Faux, D.R. Surface contamination initiated laser damage, article, January 24, 1997; California. (digital.library.unt.edu/ark:/67531/metadc685740/: accessed December 12, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.