Open Discussion on Advanced Armor Concepts

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Open Discussion on Advanced Armor Concepts

• Moderated by A. René Raffray
• UCSD
• HAPL Meeting
• GA, La Jolla, CA
• August 8-9, 2006

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Background

• There are concerns with the W dry wall in
  particular regarding He retention and the
  possibility of exfoliation.
• We are considering engineered W to enhance the
  release of the implanted He but this needs to be
  conformed experimentally.
• This discussion session is meant at triggering
  ideas of other possible options in case the W
  armor does not work.

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Possible Advanced Armor Options Include

• Engineered materials (to help He release and
  thermal stress accommodation) (S. Sharafat)
• Moving solid (pebble beds?, solid belt?, others)
  (I. Sviatoslavsky)
• Momentary liquid walls (allowing the solid to
  melt and resolidify), perhaps using a lower MP
  material in a high-porosity W structure. (R.
  Raffray)
• Wetted walls (would it unacceptable based on
  impact of pre-shot chamber constituents on target
  injection and survival, and reformation of film)?
  (S. Abdel-Khalik/I. Sviatoslavsky)
• Carbon velvet from ESLI. (T. Knowles)
• Other innovative ideas. (L. Snead)

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Some of the Key Questions to be Addressed Include
Would the armor concept be able to accommodate
the ion and photon fluxes and provide an
acceptable lifetime? Would operation of the
armor concept impact the operation of other
components (e.g. a wetted wall would result in
vapor in the chamber affecting target injection
and survival)? Would the armor concept raise
other safety or operation issues that would
require specific remedial actions (e.g. in case
of C, tritium co-deposition)? What is the
stage of maturity of the concept and how
extensive is the required RD to develop it for
IFE chamber application (measure of development
risk)? Others...
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Momentary Liquid Walls (allowing solid to melt
and resolidify)

• Allowing W armor itself to melt is an option
  but concerns about stabiliuty of melt layer and
  integrity of high temperature solid W under melt
  layer
• Other possibility is to use a lower MP material
  in a high-porosity W structure
• - e.g. 90Be in 10 W structure
• - How to fabricate it?
• - Structure size to provide good melt layer
  retention through capillarity (microstructure
  size to be optimized for melt layer retention
  and integrity)

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Histories of Temperature and Phase Change
Thickness for a Be Armor as a Function of the
Chamber Sizes for the 350 MJ Target
1-mm Be on 3.5 mm FS at 580 C No chamber
gas Ion and photon energy deposition assumed
comparable to SiC Can maintain W at reasonable
temperature acceptable lifetime (1550C for
10.75 m chamber) Stability of 1-10 ?m
melt layer of Be Minimal evaporation, 0.1 nm
for 10.75 m chamber, fraction of a gram per
shot
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Answer to Some Key Questions for Momentary Liquid
Wall Concept
Would the armor concept be able to accommodate
the ion and photon fluxes and provide an
acceptable lifetime? (In principle, yes)
Would operation of the armor concept impact the
operation of other components (Probably
not) Would the armor concept raise other
safety or operation issues that would require
specific remedial actions (e.g. in case of C,
tritium co-deposition)? (No) What is the stage
of maturity of the concept and how extensive is
the required RD to develop it for IFE chamber
application (measure of development risk)?
(Fabrication and melt behavior need to be
determined).