IFT\P2008-084 Fabrication of HAPL Sized R/F foam Shells (IFE Target Fabrication Update) Presented by Reny Paguio 1 D. Goodin 1 , J. Hund, D. Jason, A. Nikroo 1 , K. Saito 1 , K. Quan 2 1 General Atomics, Inertial Fusion Technology, San Diego, CA 2 UC San Diego, San Diego, CA HAPL Meeting, Madison WI, October 22-23, 2008
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IFT\P2008-084 Fabrication of HAPL Sized R/F foam Shells (IFE Target Fabrication Update) Presented by Reny Paguio 1 D. Goodin 1, J. Hund, D. Jason, A. Nikroo.
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IFT\P2008-084
Fabrication of HAPL Sized R/F foam Shells
(IFE Target Fabrication Update)
Presented by Reny Paguio1
D. Goodin1, J. Hund, D. Jason, A. Nikroo1, K. Saito1, K. Quan2
1General Atomics, Inertial Fusion Technology, San Diego, CA
2UC San Diego, San Diego, CA
HAPL Meeting, Madison WI, October 22-23, 2008
IFT\P2008-084
Specifications for the HAPL Shell
•Shells need to be uniform− Wall Uniformity (Non Concentricity=NC)− NC Spec. 1-3% (Offset ~10.8m)
•Sphericity-Out of Round (OOR)− OOR Spec is >1% of the shells radius (~23 m)
Foam layer: 0.18 mm thickness Divinyl Benzene (DVB) or Resorcinol-Formaldehyde (RF)
DT Vapor
Foam + DT
Thin (300-1200 Å)High Z coating
~ 2.3 mm rad
10 m CH Overcoat
DTHAPL Target
Coating roughness of 50 nm (RMS)
IFT\P2008-084
Since the last HAPL Meeting we have:
• Improved the Wall uniformity & sphericity of the R/F Shells – NC of 35% to 10%– Out of Round (OOR) spec improved from 75% to 100%
• Improved the surface of the foam shell– Improved the shell’s surface by 50% • (60 nm to 30 nm RMS)
• Improved the solvent exchange process using Soxhlet Extractor– Faster (More efficient)
IFT\P2008-084
• Used in ICF experiments on OMEGA– 2 Step polycondensation reaction*– Foam Is C, H, O– Small Pore size (<0.10 m) -Transparent • Use GDP directly as overcoat• Has been shown to hold gas for HAPL size shells (15 m)
• New Direction from target designers has allowed the possibility to have O in the foam matrix– In the Past: Foam could only be C & H
– Has opened the door to use materials such as R/F
R/F was looked as a possible foam, because overcoated DVB shells were not gas retentive
* Pekala, R.W.; et al. J. Mat. Sci., 1989, 24, 3221-3227.
IFT\P2008-084
R/F foam shells are fabricated using a triple orifice droplet generator
* Paguio R.R et al., Fusion Sci & Technol, 2006,49,4
0%
25%
50%
75%
100%
0 5 10 15 20 25 30 35
% NC
PercentileDVB Shells
R/F shells
NC SpecIFT=20 dynes/cm
IFT=1 dynes/cm
IFT\P2008-084
Modifying the O2 solution changed the viscosity of the oil and the Interfacial Tension (IFT) of the emulsion system
• Surfactant reduces the IFT– Needed to prevent agglomeration of the shells
• Poly Butadiene (PBD) was investigated as a possible SBS replacement– More affect on viscosity than IFT– No dramatic improvement on NC
• Combination of the two leads to a higher IFT & viscosity
0 4 8 12 16
STD(NoSurfactant)
STD
PBD
SBS
SBS/PBD
IFT (dynes/cm)0 10 20 30 40
STD(NoSurfactant)
STD
PBD
SBS
SBS/PBD
Viscosity (Cps.)
IFT\P2008-084
SBS addition has been shown to improve the wall uniformity of HAPL sized R/F foam shells
•Improved from <5% (No Additive) to ~20% with Additive•Wall uniformity not as good as DVB (75%)•Optimizing the SBS:PBD Ratio•Optimize the density matching of the O1 and R/F sol•Investigation of other possible polymer additives
0%
25%
50%
75%
100%
0 5 10 15 20 25 30 35% NC
PercentileDVB Shells
R/F shells
RF-SBS
RF-SBS-PBD
NC SPEC
IFT=1dynes/cm
IFT=4dynes/cmIFT=1
dynes/cm
IFT=8dynes/cm20
IFT\P2008-084
The SBS/PBD additive blend to the O2 has also improved the OOR of the shells
• Yield of shells that meet the OOR spec went from 75% to 100%
• IFT increased from 4 to 8 dynes/cm when going to the SBS/PBD blend
0%
25%
50%
75%
100%
0 10 20 30OOR (m)
Percentage SBS
SBS/PBD
IFT=4dynes/cm
IFT=8 dynes/cm
( m)
IFT\P2008-084
Acid addition to the Post-Cure removes large isolated defects from the foam’s surface
• Added 0.33M of Acetic Acid to the post cure (PC) process. – Foam structure unchanged
• Surface roughness of the bare foam improved from 60 nm to 30 nm RMS – Wyko Interferometer 50X-400m scan
• Need to optimize the acid concentration to improve the bare foam surface
No Acid Added to PC Acid Added to PC
IFT\P2008-084
Soxhlet Extractor reduced the time needed for solvent exchanging from 2-3 weeks to 3 days
Using the Soxhlet Extractor is a faster more efficient way to solvent exchange
larger shells
Soxhlet Extractor
Traditionally: Once a day exchanged
into IPA
After 2-3 weeks of solvent exchange
Oil still in IPA.
After 3 days in Soxhlet
No oil in IPA.
This has also been extended into OMEGA & NIF R/F foam shell
fabrication
oil
oil
Soxhlet Extractor
Allows a continuous exchange of IPA for the
shells
IFT\P2008-084
Soxhlet Extraction limits surface defects when shells are dried
Dry shell with
Soxhlet
No big dents
Dry shell no Soxhlet
Big dents
•Soxhlet extractor removes nearly all of the oil: No big dents•No Soxhlet : Left over oil which can lead to big dents
IFT\P2008-084
Successfully made improvements on the HAPL sized R/F shells & the fabrication process
•Improved the wall uniformity using polymer additives• Avg. NC went from 35% to 10%
•Improved the OOR • 100% of the shells meet half the HAPL Spec
•Improved the bare surface of the foam with acid addition to PC process• Reduced the surface roughness by 50%
•Made the solvent exchange process more efficient using a Soxhlet Extractor• Shortened Solvent exchange time from 2-3 week to 3 days
IFT\P2008-084
Investigated other organic solvent replacements for the tetrachloroethylene (TCE)
• Looked at two additives– Bromobenzene (IFT went to 9 dynes/cm)– Tri Chlorobenzene (IFT went to 12 dynes/cm)
• Yield of intact shells decreased (~20%)– Emulsion unstable– New to investigate other surfactants
• NC was similar to the SBS/PBD addition with TCE
• Bare foam roughness went up to 120 nm RMS– Due to shell break up during curing process– This is with the acid addition in the PC