C. Adams, N. Alexander, R. Andrews, G. Besenbruch, D. Bittner, L. Brown,

1
Progress Toward Demonstrating IFE Target
Fabrication and Injection

• C. Adams, N. Alexander, R. Andrews, G.
  Besenbruch, D. Bittner, L. Brown,
• D. Callahan-Miller, T. Drake, F. Elsner, C.
  Gibson, M. Gouge, A. Greenwood,
• J. Hoffer, J. Kaae, M. Hollins, T.K. Mau, W.
  Meier, F. Najmabadi, A. Nikroo,
• J. Pulsifer, G. Rochau, J. Sater, D. Schroen, A.
  Schwendt, J. Sethian, C. Shearer,
• W. Steckle, R. Stemke, E. Stephens, R. Stephens,
  M. Tabak, M. Tillack
• and the ARIES Team
• General Atomics, Naval Research Laboratory,
  Schafer Laboratories,
• Los Alamos National Laboratory, University of
  California, San Diego,
• Sandia National Laboratories, Lawrence Livermore
  National Laboratory,
• Oak Ridge National Laboratory

Presented by Dan Goodin atHAPL Project
ReviewPleasanton, CaliforniaNovember 13-14,
2001 (IFSA2001 Plenary Session Presentation,
Paper 1111)
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Some recent IFE target fabrication/injection
papers and publications

• Progress Toward Demonstrating IFE Target
  Fabrication and Injection, D. Goodin, et al.
  IFSA-2001 (Plenary Session Talk)
• Reducing the Costs of Targets for Inertial
  Fusion Energy, G. Besenbruch et al. IFSA-2001
• Target Injection and Fabrication Possibilities
  for Fast Ignitor IFE, R. Stephens, et al.
  IFSA-2001 (Invited Talk)
• Thermal Control Techniques for Improved DT
  Layering of Indirect Drive IFE Targets, J.
  Pulsifer et al. IFSA-2001
• Concepts for Fabrication of Inertial Fusion
  Energy Targets, Nobile, et al. Fusion
  Technology, Vol. 39, March 2001, 684.
• Developing Target Injection and Tracking for
  Inertial Fusion Energy Power Plants, Nuclear
  Fusion, V41, No. 5, May 2001, 527.
• Developing the Basis for Target Injection and
  Tracking in Inertial Fusion Energy Power Plants,
  Goodin et al. Accepted for publication in Fusion
  Engineering and Design.
• Design of an Inertial Fusion Energy Target
  Tracking and Position Prediction System,
  Petzoldt et al. Fusion Technology, Vol. 39, March
  2001, 678.

Target Fabrication

Target Injection
.... Contributions and collaborations with people
at GA, LANL, NRL, UCSD, LLNL, Schafer, SNL, and
ORNL
3
Target fabrication, injection, and tracking
issues are being addressed in an integrated
fashion

• GA and LANL are part of a team addressing the
  issues of IFE target supply
• LANL lead for fabrication GA lead for
  injection
• Close coordination with target designers and IFE
  community
• Must supply about 500,000 targets per day for a
  1000 MW(e) power plant
• Precision, cryogenic targets

Exploiting our experience with ICF targets -
similar materials and processes
Target Supply Includes
Manufacture of Capsules
Filling with DT
Layering Process
Assembling Cryohandling
Injection and Tracking
.... A significant development program will be
required to demonstrate target fabrication and
injection for IFE
4
Critical issues have been identified and agreed
upon
Target fabrication critical issues 1) Ability to
fabricate target capsules hohlraums 2) Ability
to fabricate them economically 3) Ability to
fabricate, assemble, fill and layer at required
rates
NRL Radiation Preheat Target
Power plant studies have concluded that 0.25
targets are needed - reduced from 2500 each for
current targets
Target injection critical issues 4) Withstand
acceleration during injection 5) Survive thermal
environment 6) Accuracy and repeatability,
tracking
LLNL Close-Coupled HI Target
A detailed experimental plan for target injection
has been prepared - and is being carried
out (Nuclear Fusion, 41. May 2001)
Baseline targets
.... We are addressing issues for both laser and
heavy-ion driven IFE targets
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Overview of target designs and potential processes
Target Design
Foam shell microencapsulation Interfacial
polycondensation Sputter-coating
Rad. Preheat
Foam shell microencapsulation Interfacial
polycondensation or injection molding
Cryogenic fluidized bed or In-sabot
Gas-gun or Electromagnetic
Permeation
Empty Outer Foam
Microencapsulation or Coatings in a fluidized bed
Thick Capsule
Cryogenic fluidized bed or In-hohlraum
Permeation or liquid injection
Microencapsulation Foam Casting/Doping
Dist. Radiator
.... There are many other potential paths, but
will focus on these today
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Microencapsulation studies for IFE are underway

• DVB foam shells are being encapsulated at Schafer
  for the radiation preheat target
• Density range of 10-250 mg/cc
• Pores sizes down to 1.6 ?m at 10 mg/cc
• Interfacial polymerization to make seal coat
• Direct microencapsulation of polymers
• Chemical process modeling and cost estimating

DVB beads 10 mg/cc DVB (D. Schroen)
Flowsheet prepared by LANL
. Scaleup of existing bench-scale processes will
be evaluated using chemical plant design software
(Aspen Plus)
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A successful high-Z layer for the radiation
preheat target is being developed
ESH (hazardous, WDR)
Filling with DT
Seemingly simple component has multi-disciplinary
functions and requirements
Target Design (Z, smooth, uniform)
Fabrication (coating, cost)
High-Z Layer (Au?)
Layering (IR, Joule heating)
Injection (stable, reflective)

• Gold was proposed first
• Effective in design, easy to coat, high
  reflectivity
• Issue with gold is permeation rate during filling
• Permeation through bulk gold is very slow
• Experience ? thin gold is actually hard to seal

. Some representative gold-coated flats and
spheres have been fabricated and tested
8
Gold layers were tested for required properties

• Prepared 300-1200 Å gold coatings by
  sputter-coating (very smooth, good
  mass-production technique)
• Measured thickness and uniformity by XRF
• Gas permeation slowed by only a factor of 8
• Goal to minimize tritium inventory in Target Fab.
  Facility

XRF for thickness and uniformity
Sputter-coating gold with bounce pan
Au thickness, Å
Shell rotated to examine thickness uniformity
Angle, deg
. Evaluate alternates in addition to the baseline
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Alternative high-Z materials may speed filling

• Palladium is a well-known diffuser in tritium
  applications
• Target designers are finding Pd reduces the
  imprint
• Permeation for hydrogen is very high
• Reflectivity is lower but may be acceptable (80
  vs 95)
• Concern for pure Pd is phase change (expansion)
  upon exposure to H2 (often alloyed with Ag to
  reduce effect)
• Made some Pd flats and spheres for testing
• Exposed flats on glass to H2 - instant wrinkling
• Exposed Pd-coated polymer sphere - no visible
  change

Fill Time _at_ 300K Pd 4.4 hrs Ta 50 days Nb 6.6
yrs 0.047 atm ?P Calc. for bulk
600 Å Pd on PAMS shell - before and after
390 Å Pd on Si, reaction to H2 exposure
Before
During
After
. Full test is to fill target, cool, and measure
reflectivity at cryogenic temperatures!
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Industrial technologies are being brought to
target fabrication

• Fluidized beds are well established in industry -
  GA has reduced costs of coated nuclear fuel
  particles
• Mass-production scaling of bounce-pan method
  used for high-quality ICF shells on PAMS mandrels
• Several runs for GDP coating have shown good
  results - very promising method
• Thickness variations (10) and surface roughness
  comparable to ICF

Coating
Mandrel
Fluidized Bed GDP Coating Setup
PAMS Mandrels in Fluidized Bed
3 micron thick GDP coating on PAMS
.... Fluidized bed technology has a number of
potential applications to IFE target fabrication
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An alternative mass-production coating method is
solution spray-drying in a fluidized bed

• Spray coating technology widely used in
  pharmaceutical industry
• Polyimide coatings using a fluidized bed have
  been made
• Wall thickness of a few microns FTIR shows fully
  imidized
• Currently working on vapor/liquid smoothing

2 mm PI
Fluidized bed coating zone with screen
Additional gas flow
Nebulizer creates microspray
Nebulizer gas flow
.Industrial technologies such as fluidized beds
are needed to reduce the costs of target
fabrication
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Reduced requirements may allow less-precise
processes

• Recent results High-yield capsules tolerate
  rougher surfaces than low-yield targets
• Ablator 10-20X NIF Standard (10 to 20 nm)
• Inner ice roughness 5-10X NIF (1 ?m)

CH ablator
Partial skin on foam hemishell exterior
LLNL targets

• Status
• Teflon mold made
• 100 mg/cc foam shell
• Easy mold removal
• Defects at injection port and at equator
• Ongoing work

4 mm diameter hemishell 100 mg/cc, 400 ?m wall
Foam cross section
Partial skin

• Advantages
• Simple process
• Reproducible process (each shell has same
  diameter and wall thickness)

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Progress in special materials for LLNL target

• Distributed radiator target has a number of new
  materials - low density metal-doped CH and metal
  foams
• Developing low-density foam fabrication methods
• Working with designers to simplify materials
• Moral equivalent of the more difficult materials

A AuGd lt1 denseB AuGd 100 denseC
Fe 0.2 denseD (CD2)AuE AuGd lt1 denseF
Al lt3 denseG AuGd lt2 denseH CD2I
Al 2 denseJ AuGd 4 denseK, L DTM BeBr
or PolystyreneN (CD2)Au
Cross section of hohlraum
Metal-doped PS Foams
Undoped 30 mg/cc
Nano-powder incorporation
Undoped 30 mg/cc PS foam
2 W-doped 30 mg/cc PS foam
2 Au-doped30 mg/cc
.... Progress in simplifying the target
components!
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Target filling and layering methods must be
scaled to high throughputs
Fluidized Bed Concept for Capsule Layering
The first full target supply system is at OMEGA
? 4 filled/layered targets/day
INJECT IR
Tube Layering Concept for Hohlraums
FLUIDIZED BED WITH GOLD PLATED (IR REFLECTING)
INNER WALL
ASSEMBLED HOHLRAUMS ARE STAGED IN VERTICAL TUBES
WITH PRECISE TEMPERATURE CONTROL
Pressure cell with trays
COLD HELIUM
36 I.D. X 40 Tall, 8 trays, 290,000 targets
.... Development programs to demonstrate low-cost
processes for filling and layering
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Modeling to evaluate DT inventory in TFF

• Highly desirable to minimize T inventory in the
  TFF (lt1 kg)
• Model to evaluate effects of target design and
  filling process parameters
• Provide guidance on areas of RD

• Results Status
• Need to minimize dead-space, maximize
  temperature, maximize target strength
• Filling of indirect drive targets in hohlraums
  results in 30X higher inventories
• Current best estimates of minimum inventories
• HIF Target - cryogenic assembly 0.18 kg tritium
• DD Target - 10 mg/cc foam shell 1.24 kg tritium
• DD Target - 100 mg/cc foam shell 0.56 kg tritium

Work is in progress, but we have demonstrated
Fill at 400K 2 hour layering time
.... Details of model in Fusion Technology, 39 ,
684 (2001)
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Demonstration of mass layering with a room
temperature surrogate instead of hydrogen

• Basic concept use a more convenient surrogate
  to demonstrate fluidized bed layering and
  evaluate operating parameters
• Allows use of room temperature characterization
  equipment
• Prepared samples by microencapsulation and by
  injection

IR LAMP
Filled thru hole and sealed
Before ?
After ?
Fluidized bed in water bath
Oxalic acid
Neopentyl alcohol
.... Proof-of-principle demonstration done, next
step is to design a cryogenic fluidized bed system
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In-hohlraum layering is being evaluated

• Thermal Control Techniques for Improved DT
  Layering of Indirect Drive IFE Targets - John
  Pulsifer et al.
• FB layering works for ID, but requires rapid
  assembly few seconds before shot
• In-hohlraum layering sequence fill with DT,
  cool, assemble, then layer in tubes
• Advantages ? reduces DT inventory, allows slow
  assembly, buffer of ready targets

Design Data Cu rods 4.68 m long 234
hohlraums/rod ?T top/bottom 0.1K 0.3 g/s He at
200 psi/rod ?P 10 psi
Provide a uniform T boundary and a varying radial
conductance - to result in desired T profile
With gaps in B layer
Results calculated T at hohlraum surface
gives 200 ?K variation at DT surface (CH ablator)
Stack of hohlraums in cooled tubes
.... But how does this translate to the TFF?
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Design calculations show equipment size for
in-hohlraum layering is reasonable
Design Data 3 hr layering 0.5 h backlog 18 rods
per bundle 18 bundles total 75,600
hohlraums Total He cooling flow 97 g/s
54 s between movements
3 s between movements
.... In-hohlraum layering can also apply to DD
targets
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Layering in a sabot can be similar to layering in
a hohlraum

• A sabot is used to protect the direct drive
  target during injection
• Concept chain cools ends of sabot and waist
  made hotter by tailored thermal conductance ?
  isotherms at capsule
• For 5 cm links, 5 Hz shot rate and 15 min
  layering time need 225 m of chain
• Chain may be serpentined into smaller volume (10m
  x 4.5m x 1m)

RF plate set and sabot located at every link of
chain

• RF E-field direction cycled at each station to
  maintain layer uniformity
• As links approach injector, RF power reduced and
  temperature adjusted to 18.2K

20
With SNL and others, target systems for Z-pinch
driven IFE are being developed
Removable lid
Be capsule Liquid H2 buffers
Assembled RTL/target in transit
Plant Design Data Rep-rate 0.1 Hz Yield 3 to
20 GJ Power 1100 MW(e)
See ZP-3, A Power Plant Utilizing Z-Pinch Fusion
Technology, Rochau et al. IFSA2001
Flibe-protected ZFE chamber concept
Target Assembly Station
.... Design concepts have been prepared
indicating time frames for cryogenic target
assembly and handling are feasible
21
Target survival during injection - modeling
analyses

• With UCSD and the ARIES team, an integrated model
  of target heating during injection is being
  developed

Indirect drive target is well insulated by
hohlraum materials
Direct drive target needs high surface
reflectivity to increase the usable reactor wall
temperature
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Target survival during injection - material
properties
Uncertainty in response of DT ice to rapid heat
flux exposure ? experiment being designed Based
on techniques previously developed at
LANL Cryogenic torus effectively turns the target
inside-out exposing the DT ice inner surface
for viewing
DT/Foam Layer
Foam cast in torus
Exposed DT
Uncertainty in actual reflectivity of thin high-Z
coatings ? experiment Allowable reactor wall
temperature depends on target heating/survival Fab
ricated Au samples and measured reflectivity as
f(thickness, wavelength) Calculated allowable
chamber operating conditions
Side view, cross-section of cryogenic torus
(windows not shown)
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Target survival during injection - demonstration

• Strategy and approach
• Acquire proof-of-principle data on target
  injection as soon as possible
• Provide a facility to aid in developing
  practical, survivable targets
• Develop and demonstrate injection and tracking
  technologies suitable for an IFE power plant
• Prototype concepts and designs for application in
  an IRE

.... System is in final design stage, procurement
in CY02
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Summary and conclusions
Capsule Fabrication

• Materials fabrication technologies are now being
  defined
• Exploratory RD programs are underway - including
  experiments
• Chemical process modeling and cost estimating is
  beginning
• Industrial technologies for mass-production are
  being applied

Filling and Layering

• Filling models are available to guide the RD
  programs
• Alternative approaches are being evaluated
• Initial design calculations are underway

Injection

• A coordinated program of modeling, materials
  measurements, and equipment for demonstrations is
  underway
• Methods for fueling of Z-pinch driven IFE devices
  are being developed

.... A significant development program for IFE
target fabrication, filling, layering, and
injection will be required