Management of unconverted light for the National Ignition Facility target chamber Metadata

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Title

  • Main Title Management of unconverted light for the National Ignition Facility target chamber

Creator

  • Author: Anderson, A. T.
    Creator Type: Personal
  • Author: Bletzer, K.
    Creator Type: Personal
  • Author: Burnham, A. K.
    Creator Type: Personal
  • Author: Dixit, S
    Creator Type: Personal
  • Author: Genin, F. Y.
    Creator Type: Personal
  • Author: Hibbard, W.
    Creator Type: Personal
  • Author: Norton, J.
    Creator Type: Personal
  • Author: Scott, J. M.
    Creator Type: Personal
  • Author: Whitman, P. K.
    Creator Type: Personal

Contributor

  • Sponsor: United States. Department of Energy. Office of the Assistant Secretary for Defense Programs.
    Contributor Type: Organization
    Contributor Info: USDOE Office of Defense Programs (DP) (United States)

Publisher

  • Name: Lawrence Livermore National Laboratory
    Place of Publication: California
    Additional Info: Lawrence Livermore National Lab., CA (United States)

Date

  • Creation: 1998-07-08

Language

  • English

Description

  • Content Description: The NIF target chamber beam dumps must survive high x-ray, laser, ion, and shrapnel exposures without excessive generation of vapors or particulate that will contaminate the final optics debris shields, thereby making the debris shields susceptible to subsequent laser damage. The beam dumps also must be compatible with attaining and maintaining the required target chamber vacuum and must not activate significantly under high neutron fluxes. Finally, they must be developed, fabricated, and maintained for a reasonable cost. The primary challenge for the beam dump is to survive up to 20 J/cm{sup 2} of lpm light and 1 - 2 J/cm{sup 2} of nominally 200 - 350 eV blackbody temperature x rays. Additional threats include target shrapnel, and other contamination issues. Designs which have been evaluated include louvered hot-pressed boron carbide (B{sub 4}C) or stainless steel (SS) panels, in some cases covered with transparent Teflon film, and various combinations of inexpensive low thermal expansion glasses backed by inexpensive absorbing glass. Louvered designs can recondense a significant amount of ablated material that would otherwise escape into the target chamber. Transparent Teflon was evaluated as an alternative way to capture ablated material. The thin Teflon sheet would need to be replaced after each shot since it exhibits both laser damage and considerable x- ray ablation with each shot. Uncontaminated B{sub 4}C, SS, and low thermal expansion glasses have reasonably small x-ray and laser ablation rates, although the glasses begin to fail catastrophically after 100 high fluence shots. Commercially available absorbing glasses require a pre-shield of either Teflon or low thermal expansion glass to prevent serious degradation by the x-ray fluence. Advantages of the hot-pressed B{sub 4}C and SS over glass are their performance against microshrapnel, their relative indifference to contamination, and their ability to be refurbished by aggressive cleaning using CO{sub 2} pellets, glass beads, high pressure water or ultrasonic tanks. In addition the expected replacement rate to avoid catastrophic failure makes the glass option more costly. SS is less expensive, more easily formed into a louver design with high capture efficiency, and otherwise equivalent to B{sub 4}C. Hence, it would be preferred as long as debris shield damage is not substantially greater for SS as compared to damage from an equivalent mass of contamination of B{sub 4}C. If debris shield damage is problematic, the escape of SS could be mitigated by use of a transparent Teflon film. The Teflon film would require increased target chamber pumping and cleaning capability to accommodate the x-ray decomposition products.
  • Physical Description: 2.1 Megabytes pages

Subject

  • Keyword: Beam Dumps
  • STI Subject Categories: 70 Plasma Physics And Fusion Technology
  • Keyword: Thermal Expansion
  • Keyword: Boron Carbides
  • Keyword: Target Chambers
  • Keyword: Stainless Steels
  • Keyword: Radiation Effects
  • Keyword: Us National Ignition Facility
  • Keyword: Solid State Lasers
  • Keyword: Targets
  • Keyword: Ultrasonic Waves
  • Keyword: Inertial Confinement

Source

  • Conference: Third Annual International Conference on Solid State Lasers for Application (SSLA) to Inertial Confinement Fusion, Monterey, CA (US), 06/07/1998--06/12/1998

Collection

  • Name: Office of Scientific & Technical Information Technical Reports
    Code: OSTI

Institution

  • Name: UNT Libraries Government Documents Department
    Code: UNTGD

Resource Type

  • Article

Format

  • Text

Identifier

  • Report No.: UCRL-JC-129706
  • Report No.: 39DP02000
  • Grant Number: W-7405-ENG-48
  • Office of Scientific & Technical Information Report Number: 2770
  • Archival Resource Key: ark:/67531/metadc668810