Cluster ion beam polishing for inertial confinement fusion target capsules

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Targets for Inertial Confinement Fusion (ICF) typically consist of a hollow, spherical capsule filled with a mixture of hydrogen isotopes. Typically, these capsules are irradiated by short, intense pulses of either laser light (``direct drive``) or laser-generated. x-rays (``indirect drive``), causing them to implode This compresses and heats the fuel, leading to thermonuclear fusion. This process is highly sensitive to hydrodynamic (e.g., Rayleigh-Taylor) instabilities, which can be initiated by imperfections in the target. Thus, target capsules must be spherical and smooth One of the lead capsule designs for the National Ignition Facility, a 1.8 MJ laser being built at Livermore, ... continued below

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17 p.

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McEachern, R. June 9, 1998.

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Description

Targets for Inertial Confinement Fusion (ICF) typically consist of a hollow, spherical capsule filled with a mixture of hydrogen isotopes. Typically, these capsules are irradiated by short, intense pulses of either laser light (``direct drive``) or laser-generated. x-rays (``indirect drive``), causing them to implode This compresses and heats the fuel, leading to thermonuclear fusion. This process is highly sensitive to hydrodynamic (e.g., Rayleigh-Taylor) instabilities, which can be initiated by imperfections in the target. Thus, target capsules must be spherical and smooth One of the lead capsule designs for the National Ignition Facility, a 1.8 MJ laser being built at Livermore, calls for a 2-mm- diam capsule with a 150-{micro}m-thick copper-doped beryllium wall. These capsules can be fabricated by sputter depositing the metal onto a spherical plastic mandrel. This results in surfaces with measured Rq`s of 50 to 150 nm, as measured with an atomic force microscope For optimal performance the roughness should be below 10 nm rms We have begun studying the use of ion cluster beam polishing as a means of improving the surface finish of as-deposited capsules In this approach, a batch of capsules would be agitated in a bounce pan inside a vacuum chamber during exposure to the cluster beam. This would ensure a uniform beam dose around the capsule. We have performed preliminary experiments on both Be flats and on a stationary Be capsule On the capsule, the measured Rq went from 64 nm before polishing to 15 nm after This result was obtained without any effort at process optimization. Similar smoothing was observed on the planar samples

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17 p.

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INIS; OSTI as DE98058695

Other: FDE: PDF; PL:

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  • 12. international conference on ion implantation technology, Kyoto (Japan), 22-28 Jun 1998

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  • Other: DE98058695
  • Report No.: UCRL-JC--130683
  • Report No.: CONF-980679--
  • Grant Number: W-7405-ENG-48
  • Office of Scientific & Technical Information Report Number: 305341
  • Archival Resource Key: ark:/67531/metadc683482

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  • June 9, 1998

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  • July 25, 2015, 2:20 a.m.

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  • April 10, 2017, 2:04 p.m.

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McEachern, R. Cluster ion beam polishing for inertial confinement fusion target capsules, article, June 9, 1998; California. (digital.library.unt.edu/ark:/67531/metadc683482/: accessed September 23, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.