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Title: Understanding the Critical Parameters of the PAMS Mandrel Fabrication Process

Abstract

As a part of an effort to continually better the roundness and roughness of ablator capsules, we looked at improving the same for the poly(alphamethylstyrene) or PAMS mandrels used to make the plastic capsules. The importance of this work is based on the fact that the surface properties of the mandrels set the lower limit for the ultimate attributes of the ablator capsule. These mandrels are made using an elegant double-emulsion process that uses the isotropic forces brought about by hydrostatic pressure and interfacial tension to seek sphericity. This paper describes the reasoning that led to investigating the so-called curing process where a solid PAMS shell is generated from a solution phase for achieving this goal. Using modeling to account for the mass transfer of the fluorobenzene solvent phase, we demonstrate that it is the control of the conditions through the percolation point of the system that leads to better mandrels. These concepts were implemented into the fabrication process to demonstrate significant improvements of the roundness of the mandrels.

Authors:
 [1];  [1];  [1];  [1]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1343051
Report Number(s):
LLNL-JRNL-677215
Journal ID: ISSN 1536-1055; TRN: US1701802
Grant/Contract Number:
AC52-07NA27344
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Fusion Science and Technology
Additional Journal Information:
Journal Volume: 70; Journal Issue: 2; Journal ID: ISSN 1536-1055
Publisher:
American Nuclear Society
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 42 ENGINEERING

Citation Formats

Bhandarkar, Suhas, Paguio, Reny, Elsner, Fred, and Hoover, Denise. Understanding the Critical Parameters of the PAMS Mandrel Fabrication Process. United States: N. p., 2016. Web. doi:10.13182/FST15-245.
Bhandarkar, Suhas, Paguio, Reny, Elsner, Fred, & Hoover, Denise. Understanding the Critical Parameters of the PAMS Mandrel Fabrication Process. United States. doi:10.13182/FST15-245.
Bhandarkar, Suhas, Paguio, Reny, Elsner, Fred, and Hoover, Denise. 2016. "Understanding the Critical Parameters of the PAMS Mandrel Fabrication Process". United States. doi:10.13182/FST15-245. https://www.osti.gov/servlets/purl/1343051.
@article{osti_1343051,
title = {Understanding the Critical Parameters of the PAMS Mandrel Fabrication Process},
author = {Bhandarkar, Suhas and Paguio, Reny and Elsner, Fred and Hoover, Denise},
abstractNote = {As a part of an effort to continually better the roundness and roughness of ablator capsules, we looked at improving the same for the poly(alphamethylstyrene) or PAMS mandrels used to make the plastic capsules. The importance of this work is based on the fact that the surface properties of the mandrels set the lower limit for the ultimate attributes of the ablator capsule. These mandrels are made using an elegant double-emulsion process that uses the isotropic forces brought about by hydrostatic pressure and interfacial tension to seek sphericity. This paper describes the reasoning that led to investigating the so-called curing process where a solid PAMS shell is generated from a solution phase for achieving this goal. Using modeling to account for the mass transfer of the fluorobenzene solvent phase, we demonstrate that it is the control of the conditions through the percolation point of the system that leads to better mandrels. These concepts were implemented into the fabrication process to demonstrate significant improvements of the roundness of the mandrels.},
doi = {10.13182/FST15-245},
journal = {Fusion Science and Technology},
number = 2,
volume = 70,
place = {United States},
year = 2016,
month = 7
}

Journal Article:
Free Publicly Available Full Text
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  • OAK-B135 Imperfections in PAMS mandrels critically govern the quality of final ICF targets. Imperfections in the mandrels can have a wide range of origins. Here, they present observations of 3 types of imperfections, and data to support the proposal that hydrodynamic factors during the curing of the mandrel are potential causes of these imperfections.
  • Imperfections in PAMS mandrels critically govern the quality of final ICF targets. Imperfections in the mandrels can have a wide range of origins. Here, they present observations of 3 types of imperfections, and data to support the proposal that hydrodynamic factors during the curing of the mandrel are potential causes of these imperfections.
  • A new technique for producing hollow shell laser fusion fuel capsules has-been developed that starts with a depolymerizable mandrel. In this technique we use poly({alpha}-methylstyrene) (PAMS) beads or shells as mandrels which are overcoated with plasma polymer. The PAMS mandrel is thermally depolymerized to gas phase monomer. which diffuses through the permeable and thermally more stable plasma polymer coating, leaving a hollow shell. Using this technique we made shells from 200 {mu}m to 4 mm diameter with 15 to 100 {mu}m wall thickness having sphericity better than 0.5 {mu}m and surface finish better than 10 nm RMS. 13 refs., 5more » figs., 1 tab.« less
  • A technique was developed for fabricating spherical shell targets for implosion physics experiments with diameters up to several millimeters and with unique structural features such as thin metal layers or texture on the inside surface. We start with a spherical bead or thin shell of poly(alpha-methylstyrene) (PAMS) of the desired size, which can be textured by laser photoablation or overcoated with a thin layer of diagnostic material. The mandrel is next overcoated with plasma polymer (CH) 2{endash}50 {mu}m thick. Upon heating, the PAMS depolymerizes to a gaseous monomer which diffuses through the thermally stable plasma polymer coating leaving a hollowmore » shell. Shells produced by this technique are uniform in wall thickness, and highly spherical. If the PAMS mandrel is textured, the mandrel topology is transferred to the inner wall of the plasma polymer shell. Likewise, thermally stable coatings on the mandrel are transferred to the inner shell wall. {copyright} {ital 1996 American Vacuum Society}« less