Grazing incidence liquid metal mirrors (GILMM) for radiation hardened final optics for laser inertial fusion energy power plants

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A thin film of liquid metal is suggested as a grazing incident liquid metal mirror (GILMM) for robust final optics of a laser inertial fusion energy (IFE) power plant. The amount of laser light the mirror can withstand, called the damage limit, of a sodium film 85{sup o} from normal is calculated to be 57 J/cm{sup 2} normal to the beam for a 20 ns pulse and 1.3 J/cm{sup 2} for a 10 ps pulse of 0.35 {micro}m light (2 m{sup 2} and 90 m{sup 2} of mirror area per 100 kJ of laser energy at 20 ns and 10 ... continued below

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Moir, R W June 30, 1999.

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A thin film of liquid metal is suggested as a grazing incident liquid metal mirror (GILMM) for robust final optics of a laser inertial fusion energy (IFE) power plant. The amount of laser light the mirror can withstand, called the damage limit, of a sodium film 85{sup o} from normal is calculated to be 57 J/cm{sup 2} normal to the beam for a 20 ns pulse and 1.3 J/cm{sup 2} for a 10 ps pulse of 0.35 {micro}m light (2 m{sup 2} and 90 m{sup 2} of mirror area per 100 kJ of laser energy at 20 ns and 10 ps, respectively). Feasibility relies on keep the liquid surface flat to the required accuracy by a combination of polished substrate, adaptive (deformable) optics, surface tension and low Reynolds number, laminar flow in the film. The film's substrate must be polished to {+-} 0.015 pm. Then surface tension keeps the surface smooth over short distances (<10 mm) and low Reynolds number laminar flow keeps the surface smooth by keeping the film thickness constant to less than + 0.01 w over long distance >10 mm. Adaptive optics techniques keep. the substrate flat to within {+-} 0.06 pm over 100 mm distance and {+-}0.6 {micro}m over 1000 mm distances. The mirror can stand the x-ray pulse when located 30 m away from the microexplosions of nominal yield of 400 MJ (50 MJ of X rays) when Li is used but for higher atomic number liquids like Na there may be too high a temperature rise forcing use of other x-ray attenuation methods such as attenuation by xenon gas. The cumulative damage from neutrons causing warpage of the liquid film's substrate can be compensated by adaptive optics techniques giving the mirrors long life, perhaps 30 years. The GILMM should be applicable to both direct and indirect drive and pulse lengths appropriate to slow compression ({approx}20 ns) or fast ignition ({approx}10 ps). For direct drive laser beams near the poles (70{sup o}, where 90{sup o} is vertical), stable thin films become more challenging. Proof of concept experiments are needed to verify the predicted damage limit and required smoothness.

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1.2 Megabytes pages

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  • 5th International Symposium on Fusion Nuclear Technology (ISFNT-5), Rome (IT), 09/19/1999--09/24/1999

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  • Report No.: UCRL-JC-133027
  • Report No.: AT5015032
  • Grant Number: W-7405-ENG-48
  • DOI: 10.2172/9876 | External Link
  • Office of Scientific & Technical Information Report Number: 13889
  • Archival Resource Key: ark:/67531/metadc618744

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  • June 30, 1999

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  • June 16, 2015, 7:43 a.m.

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  • May 6, 2016, 3:19 p.m.

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Moir, R W. Grazing incidence liquid metal mirrors (GILMM) for radiation hardened final optics for laser inertial fusion energy power plants, article, June 30, 1999; California. (digital.library.unt.edu/ark:/67531/metadc618744/: accessed September 20, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.