Update on IFE Target Fabrication Progress

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Update on IFE Target Fabrication Progress
N. Alexander. L. Brown, R. Gallix, D. Geller, C.
Gibson, J. Hoffer, A. Nikroo, R. Petzoldt, R.
Raffray, D. Schroen, J. Sheliak, W. Steckle, M.
Takagi, E.Valmianski, B. Vermillion
presented by Dan GoodinHAPL Project
Review Madison, Wisconsin September 24, 2003
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Topics

• Foam Insulated Target Fabrication and Assembly
• Foam Insulated Target Reflectivity
• Insulating Foam Survival During Acceleration
• Mass-Production Layering System Design
• Summary and Conclusions

NRL Basic High Gain Target
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The foam insulated target could significantly
open the chamber design window!

• Basic target (18K) lt0.68 W/cm2 (970?C or 2.8
  mtorr Xe _at_ 4000K)
• Foam-insulated (100 ?m, 10) lt3.7 W/cm2 (970?C
  and 12.5 mtorr _at_ 4000K)
• Foam-insulated and 16K lt9.3 W/cm2 (970?C and 40
  mtorr _at_ 4000K)

Rene Raffray will talk more about target thermal
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Foam insulated target fabrication and assembly
Additional advantage reduces issue of DT
inventory (filling time)

• Moving high-Z to outside allows multiple 1 ?m
  holes
• - holes let DT enter and cover full area of seal
  coat, reducing fill time
• at cryo, holes are necessary to dry the foam
  after filling

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There are potential insulating-foam fabrication
methods
1) Hemi-shells (demonstrated, but not for IFE)
2) Injection molding with NRL target (conceivable
.)

• Advantages
• Reproducible (same diameter wall)
• Standard industry practices

Injection molding, W. Steckle LANL
3) Chemical process (likely best for IFE ..)
Foam layer over shell by emulsification, M. Takagi
Foam with Pb
By shake and toss (8 to 170 ?m walls)
CH
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Microencapsulation turns emulsification into
mass-production
Excess precursor results in 289 ?m thick foam
Want
but
4 mm
150 ?m
289 ?m
2) Add Bubbles
Two approaches
Bubble injection
10 DVB polymerization initiator(V70) in DEP
1) Alternate with beads
One issue may be shrinkage rate of each layer
after drying?
0.05 PAA (or PVA) Stripping Flow
pulse
bead
Conclusion microencapsulation to make
insulating foam seems feasible, next we should
try it
Insulated foam target
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Draining (drying) the outer foam

• Outer foam needs drying after the fill
• Calculated DT flow thru one 1 ?m hole
• liquid 4.6 minutes
• gas 77.8 minutes
• Ron Petzoldt
• Prior experimental data also indicate a single 1
  ?m hole will drain very fast (Jim Hoffer)

Conclusion filling drying the outer foam
shouldnt be a problem if there are many
approximately one micron sized holes (kHz laser?)
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Reflectivity of outer layer

• Outer reflective layer on outer foam is still
  needed
• total IR heat flux (970C) 14 W/cm2 (too high)
• reflectivity in the mid-90 desirable
• Micron-sized foam cells simply overcoated with
  metal is black
• smoothing coat needed - what parameters?

• Test series to demonstrate reflectivity and find
  parameters
• CH coating thickness (surface finish)
• high-Z coating thickness

Result design window curves for insulating
foam and high-Z parameters to survive injection
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Example of reflectivity - PAMS and DVB
Bare DVB with Al
PAMS with Al (reflecting illuminator)
micron-sized foam overcoated with metal is not
reflective
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Does the insulating foam collapse during
injection?
E Youngs modulus ?f density C1
0.38 Exponent 2.29
NRL basic target - 4 mm OD - 3 mg mass
Insulating foam - 150 ?m thick - variable
density
?pl plastic stress ?ys yield stress of
solid C2 0.15 Exponent 1.85
Support film
1000 gs acceleration
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• ANSYS to evaluate survival
• Ozkul model (0.1 - 20 ?m cells, 40 - 270 mg/cc)
• Use Deshpande-Fleck Parameter (DFP) from ANSYS
  results
• DFPlt ?pl (foam will spring back)

10X
Log Deshpande-Fleck Parameter (DFP) _at_ 1000g
Room temperature (conservative)
1
1
5
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Foam Density Ratio ()
M.H.Ozkul, J.E.Mark, and J.H.Aubert. The
Mechanical Behavior of Microcellular Foams, Mat.
Res .Soc. Symp. Proc. Vol.207.1991 V.S.Deshpande,
N.A.Fleck. 2000.J.Mech.Phys.Solids 481253-1283
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Target remains centered in foam

• Must spring back from any significant
  de-centering quickly
• Simple experiments

100 mg/cm3 DVB Height 4.5 mm Area 63 mm2
E0.76 MPa
1-D estimates for compression of foam by
accelerated target
Data at RT, E at cryo typically 2 to 10 times
higher (i.e., conservative)
these data indicate the insulating foam will
withstand acceleration and will remain centered
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Mass-production layering system design
Layering beds
N. Alexander, HAPL Mtg., 4/2003

• Since last meeting
• selected full-size for capsule, drafted SDD and
  specs for cryo-circulator
• prepared cryostat and operating concepts
• Goal demonstrate thermal environment in a
  cryogenic fluidized bed
• IR replaces ?-decay heat
• start with 40 ?m wall CH shell (transparent
  easier to fill)
• can also use transparent foams

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Design of mass production layering system is
progressing

• Demonstration will use 4 mm targets
• strong desire to demo full-size components
• precludes once-through and RT circulator
  designs
• Will use cryogenic compressor
• requires minor modification of existing design
• have agreement with Barber-Nichols on basic
  operating parameters (e.g. T, pressures, heat
  load)
• Overall status
• conceptual drawings are completed
• System Design Description out for internal review

Cryo-circulator
bed
HX
Typical cryo-circulator
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Design uses many borrowed ideas and commercial
devices
Heat Exchangers on Second Stage (OMEGA)
Fluidized Bed Layering Device
Bell Jar Design (OMEGA, CPL)
24ø
Standard Evaporation Chamber Components
Permeation Cell (D2TS, OMEGA, CPL)

• One unique feature is that internal environment
  is vacuum
• OMEGA CPL use low pressure helium
• This device is not intended for DT use
• Greatly simplifies design

Transfer Arm (OMEGA)
External Vacuum Manipulators (OMEGA)
Cryogenic Compressor
Cryocoolers (CPL, OMEGA)
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Operating Steps (1 of 2)
Bell Jar
permeation cell
filled/cooled targets
basket
inserter
2) Bell jar is lowered and vacuum pumped 3)
Inserter raised and permeation cell breech lock
engaged
4) Capsules permeation filled and cooled to
cryogenic temperature 5) Breech lock disengaged
and inserter lowered
1) Basket w/700 empty capsules placed on inserter
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Operating Steps (2 of 2)
filled/cooled targets
Top View
cryogenic fluidized bed gas supply lines
filled/cooled targets
Note view rotated 90 from other views
transfer arm
6) Basket (w/ filled capsules) grasped by
transfer arm 7) Transfer arm rotated 90 degrees
8) Basket placed on fluidized bed lower half 9)
Fluidized bed lower half raised and sealed with
upper half
10) Capsules layered and characterized
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Remaining design is standard engineering,
however, there are several developmental areas

• Capsule Static Cling
• mesh basket ensures that capsules arrive at
  layering device
• several ideas to eliminate cling in layering
  device
• ionizer (baseline), radiation source, alternating
  current
• Layering Method
• fluidized bed (baseline)
• bounce pan
• Characterization
• take image of moving capsule (baseline)
• capture single capsule and characterize when
  stationary

Approach is to have a baseline design, yet keep
things simple and modular, so that different
concepts can be substituted
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Summary and conclusions

• We think the insulated-foam target can be
  reasonably fabricated for IFE
• The insulated-foam target reduces issues
  associated with filling time
• The insulating foam can be drained of DT
• Insulating foam will survive the acceleration
  during injection and remain centered
• Demonstration system for mass-production layering
  is being designed

DT foam
DT solid
DT gas