Fabrication Of Graded Germanium-Doped CH Shells

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One of the current capsule designs for achieving ignition on the National Ignition Facility (NIF) is a 2 mm diameter graded Ge-doped CH shell that has a 160 {micro}m thick wall. The Ge doping is not uniform, but rather is in radial steps. This graded Ge-doped design allows rougher surface finish than the original undoped CH design thus has a less stringent new surface standard. We selected quality mandrel mandrels by coating dozens of mandrel batches to {approx}70 {micro}m thickness to amplify sub-micrometer defects on the mandrels and successively removed inferior batches. The Ge-doping layers are made by introducing (CH{sub ... continued below

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Chen, K C; Huang, H; Nikroo, A; Letts, S A & Cook, R C July 7, 2005.

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One of the current capsule designs for achieving ignition on the National Ignition Facility (NIF) is a 2 mm diameter graded Ge-doped CH shell that has a 160 {micro}m thick wall. The Ge doping is not uniform, but rather is in radial steps. This graded Ge-doped design allows rougher surface finish than the original undoped CH design thus has a less stringent new surface standard. We selected quality mandrel mandrels by coating dozens of mandrel batches to {approx}70 {micro}m thickness to amplify sub-micrometer defects on the mandrels and successively removed inferior batches. The Ge-doping layers are made by introducing (CH{sub 3}){sub 4}Ge to the gas stream. The doping concentrations were determined by performing tryout runs and characterized by X-ray fluorescence analyses and quantitative radiograph calculations, with good agreement between the methods being demonstrated. The precise layer thickness and Ge concentrations were determined by a non-destructive quantitative contact radiograph. The as-coated shell has an inner 10 {micro}m undoped CH layer, followed by a 48 {micro}m thick 0.83 at.% Ge-doped CH, 10 {micro}m thick 0.38 at.% Ge-doped CH and then 90 {micro}m of undoped CH. The shell meets nearly all the NIF design thickness specifications and Ge concentrations. The atomic force microscope power spectrum of the shell meets the new NIF standard. The shells has a root-mean-square surface roughness of {approx}24 nm (modes 100-1000). A few surface flaws are isolated domes of 1 {micro}m tall and 20 {micro}m in diameter. Mandrel was successfully removed by pyrolysis at 305 C for 10-20 h. After pyrolysis, the diameter and wall shrink 0.4% and 5.7%, respectively. The shell's inner surface has root-mean-square roughness ranging from 1.1-6.5 nm by WYKO interferometer measurement.

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PDF-file: 26 pages; size: 0 Kbytes

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  • Journal Name: Fusion Science and Technology; Journal Volume: 49

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  • Report No.: UCRL-JRNL-213644
  • Grant Number: W-7405-ENG-48
  • Office of Scientific & Technical Information Report Number: 888620
  • Archival Resource Key: ark:/67531/metadc873256

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  • July 7, 2005

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  • Sept. 21, 2016, 2:29 a.m.

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  • Nov. 28, 2016, 2:37 p.m.

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Chen, K C; Huang, H; Nikroo, A; Letts, S A & Cook, R C. Fabrication Of Graded Germanium-Doped CH Shells, article, July 7, 2005; Livermore, California. (digital.library.unt.edu/ark:/67531/metadc873256/: accessed October 17, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.