Update on Target Fabrication Tasks Presented by Dan Goodin at ARIES Meeting San Diego, California...
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Transcript of Update on Target Fabrication Tasks Presented by Dan Goodin at ARIES Meeting San Diego, California...
Update on Target Fabrication Tasks
Presented by Dan Goodin
atARIES Meeting
San Diego, CaliforniaJuly 1-2, 2002
Topics
• Direct drive target costing study
• Target injection and survival- Injector system status- Protection schemes for direct drive
• Indirect drive target fabrication- Feasibility- Materials selections- Status on costing study
Microencapsulation scaleup studies
NRL radiation preheat target
• Chemical engineering approach to Target Fabrication Facility (TFF)
• Costing is done for an “nth-of-a-kind” plant
• Results guide process development
Preliminary estimates for direct drive target production costs are encouraging
Major Parameters
• 500,000 targets per day
• 2-3 weeks on “assembly line”
• Installed capital of $97M
• Annual operating cost of $19M
• Cost per injected target estimated at 16.6 cents
TFF layout for radiation preheat target production
Full Presentation - HAPL April 4/5, 2002, General Atomics (http://aries.ucsd.edu/HAPL/MEETINGS/0204-HAPL/program.html)
7200 ft2 experimental space is being refurbished for use in IFE
research
Target injector fabrication is underway; Bldg. 22 is being refurbished
-85% of this years equipment is ordered-Preliminary tracking system optical testing took place at UCSD-First detector housing is complete, setting up for tests with translation stages-Software design spec and test plan are complete-Control system computers and Opto-22 programming and wiring has begun
Opto 22 input/output hardware
Tracking detector housing
An unprotected radiation preheat target will not survive with high chamber gas pressure
The chart above was optimistic - Assumes 98% reflectivity (300 A gold is about 96% reflective, palladium is less)- Uses average convection heat flux (peak flux up to 3 times higher)- Does not include condensation- Gas may be much hotter than chamber wall (with significant plasma heating)
Wake shield target heating protection calculations have been carried out1. Convective heat load is calculated as a function of target-shield separation2. Drag is calculated as a function of target-shield separation3. The relative motion of the target and shield is optimized4. Average heat flux on the target is then calculated
By E. Valmianski
P = 50 mTorrT= 1000 KV= 400 m/sShield radius = 5 mm
Membrane target protection scheme was conceived
Support frameTarget support membrane
By R. Petzoldt and M. ShmatovHeat barrier membrane coated with frozen gas
Must verify ~1000 Å film does not adversely affect target performance and gas film of appropriate variable thickness can be applied
0 1 2 3 4 5 60
0.40.81.21.62
2.42.83.23.64
Distance along target (mm)
Target with cone
Unprotected target
Target with thin shield
Radius of the shield - 4mmRadius of the target - 2 mmTemperature -1773 KDensity STD - 50 mtorrSpeed - 400 m/s
A cone used with fast ignition reduces max heat flux more than a flat shield
The cone provides a 3-fold decrease in the max heat flux as compared with the unprotected target. Improvement over flat shield is due to gas reflection off lateral surfaces.
Topics
• Direct drive target costing study
• Target injection and survival- Injector system status- Protection schemes for direct drive
• Indirect drive target fabrication- Feasibility- Materials selections- Status on costing study
Microencapsulation scaleup studies
HIF2002MoscowMay 26-31, 2002
Indirect drive target fab - main points
…. A significant R&D program will be necessary to demonstrate and scaleup these processes
• Target fabrication is one of the key feasibility issues for inertial fusion energy
• Target supply requirements are challenging- ~500,000/day precision, cryogenic targets with unique materials
- Low cost is required for economical power production
• Near-term goal of program is to provide a “credible pathway” for HIF target supply
• We have identified potential manufacturing processes that can be developed to supply the distributed radiator HIF target
The distributed radiator target of Tabak and Callahan is the reference HIF design
… Costs per target of about $0.30 are needed for economical electricity production (Woodworth and Meier UCRL-ID-117396, 1995)
LLNL Close-Coupled Heavy Ion
Driven Target
Two sided illumination by heavy ion beams Energy deposited along hohlraum materials Radiation distribution tailored by material density Unique materials required
Debbie Callahan Invited TalkAt HIF2002
The distributed radiator target of Callahan and Tabak is the reference HIF design
A: AuGd 0.1 g/ccB: AuGd 13.5 g/ccC: Fe 0.016 g/ccD: (CH)0.97Au0.03 0.011 g/ccE: AuGd 0.11 g/ccF: Al 0.07 g/ccG: AuGd 0.26 g/ccH: CD2 0.001 g/ccI: Al 0.055 g/ccJ: AuGd “sandwich” 0.1/1.0/0.5K: DT 0.0003 g/ccL: DT 0.25 g/ccM: Be0.995Br0.0051.845 g/ccN: (CD2)0.97Au0.03 0.032 g/cc
The heavy-ion driven target has a number of unique and challenging materials
Nuclear Fusion 39, 1547
… Simplification and material substitutions are needed to reduce complexity of the target
Part Material Alternate MaterialsA AuGd [high-Z only] Various - Au, Pb/Ta, Pb/Ta/Cs, Hf/Hg/Xe/KrB AuGd [high-Z only] Various - Au, Pb/Ta, Pb/Ta/Cs, Hf/Hg/Xe/KrC Fe Au-doped CH foamD (CH)0.97 Au0.03 --E AuGd [high-Z only] Various - Au, Pb/Ta, Pb/Ta/Cs, Hf/Hg/Xe/KrF Al Silica aerogelG AuGd [high-Z only] Various - Au, Pb/Ta, Pb/Ta/Cs, Hf/Hg/Xe/KrH CD2 He gasI Al CH or doped CHJ AuGd sandwich (high-Z only) Various - Au, Pb/Ta, Pb/Ta/Cs, Hf/Hg/Xe/KrK DT -- L DT --M Be0.995Br0.005 Polystyrene (CH) N (CD2)0.97Au0.03 --
Physics of Plasmas, May 2000, pp. 2083-2091
Material substitutions are defined in conjunction with target designers to
reduce target cost
Pathways to simplify the target are being defined
Recent Material Choices(Loss compared to Au/GdD. Callahan)
Au or Pb ~10-15% gain loss
Pb/Hf ~2% gain loss
Pb/Hf/Xe ~0% gain loss
Process steps for target fabrication are challenging
.... Process development programs for target fabrication and target injection are underway
1) Fabricating the spherical capsule2) Fabricating the hohlraum case3) Fabricating the radiators4) Filling the capsule with fuel5) Cooling the capsule to cryo6) Layering the DT into shell7) Assembling the cryo components8) Accelerating for injection9) Tracking the target’s position10) Providing steering/timing info
Some Possible Indirect Drive Specifications
Capsule Material CH
Capsule Diameter ~4.6 mm
Capsule Wall Thickness 250 m
Out of Round <0.1% of radius
Non-Concentricity <1% of wall thickness
Shell Surface Finish 10-200 nm RMS
Ice Surface Finish 1-10 m RMS
Temperature at shot ~18.5K
Positioning in chamber less than ± 1-5 mm
Alignment with beams <200 m
Every step except the first one is done with radioactive materials (tritium and recycled materials), so remote handling is required
There are many decisions to be made when selecting a target supply pathway
Step Methods Comments/IssuesCapsule Fabrication Microencapsulation Simple, suitable for hi-volume
Issues: sphericity, non-concentricityGDP coating onto mandrels Could solve NC problem; demo’d in
small coaters; Issues: multi-step adds cost
Solution spray drying Produce stronger, higher density PI; Issues: surface smoothness, cost
Filling Permeation Demonstrated; Issues: T inventoryLiquid filling Developmental, capsule damage
Layering Fluidized bed Demo’d in principle, req’s fast assemblyIn-hohlraum Extreme precision/uniformity
Hohlraum Comp. Fab Casting For Flibe sleeve, remote handlingLCVD For hi-Z matl’s, developmental, costMetal foams Pore sizes, densityWire arrays Uniformity, structural integrityDoping of CH foams For radiator matl’s, mass-prod
methods, handling, precisionTarget Injection/Tracking Gas-gun, electromagnetic Building demo system
.... Many of the steps above have issues associated with remote handling, dose rate, CTE mismatches on assembly
Fluidized beds for mass-production of capsules is being investigated
…. These coating methods are all two-step processes
Coating
Mandrel
PAMS Mandrels
in Fluidized
Bed
~ 3 micron thick GDP coating on PAMS
Aerosol microspray of polyamic acid solution; 4-8
micron droplet size
~ 7 micron thick PAA coating on PAMS
PAMS mandrel
PAA coating
7.3
m
Experimental system
Polyamic acid polyimide
coating
Direct capsule fabrication by microencapsulation
Microencapsulation may be most cost-effective pathway...
aq DropletgenerationAir dry Non aqueouspolymer solutionAqueous phaseSolid shellAqAqAq Loss oforganic solventAq
Laboratory scale rotary contactor
Schematic of microencapsulation Power spectrum of 4.6mm CH capsule, 45 m wall, OOR <1% of
radius, NC <3% of wall, rate 36/minute (M. Takagi)
NIF Spec (green)~16 cm
Approaching IFE Requirements!
Preliminary “Target Fabrication Facility” (TFF) layout
100’
PS shell generation
Ethanol/Water Exchange & Vacuum Drying
DT Filling (Permeation Cells)
Layering (Fluidized Bed)To
Chamber
QA/QC Lab
80’
Injector
Hohlraums
Hohlraum Production
Area
Full-scale rotary contactor: 50x50 cm,
50% liquid, 8% shells by volume, 8h target supply
~1.4m
Preliminary cost estimates indicate ~$0.11 per capsule for capsule
fabrication, filling, and layering (not including hohlraum materials and
assembly)
Hohlraum Cryo-
Assembly
Filling of the capsules with DT can be done by permeation through the capsule wall
• Issue = Minimum T inventory “at-risk”• Targets typically contain ~3-4 mg of tritium• 1.5 to 2 kg of tritium/day injected into reactor
NEEDLE
JET PIERCE
“Advanced” methods of filling have also been evaluated
HIF Target
Buckle Pressure 449 atm
Fill Time 2.8 hours
Tritium Inventory withbeta-layering 0.57 kg
Tritium Inventory with beta-layering + IR 0.27 kg
Methodology by A. Schwendt, A. Nobile (LANL), Fusion Science and Technology (to be published)
Six shots per second
Void fraction - 5%
Fill Temperature - 27C
Cool time - 0.5 h
Evacuation time - 1 h
-Layering time - 8 h
IR-Layering time - 2 h
Fill overpressure - 75% of buckle
Pressure cell with trays
Hohlraum cryo-assembly
Layering in-hohlraum or not?
“Cold Assembly”
DTDiffusion
Fill Capsule
Coolto Cryo Temps
EvacuateDT Layer
DT Ice
ColdAssembleHohlraum
Hohlraum CryogenicAssembly
LayerDT Ice
InjectManufacture
Materials
1. In-hohlraum layering
“Warm Assembly”
DTDiffusion
Fill
AssembleHohlraum
Coolto Cryo Temps
EvacuateDT
2. Fluidized bed layering of capsules
3. Warm Assembled Hohlraum
LayerDT Ice
Three routes for indirect drive target processing are possible:
…Tritium inventory will likely require cryogenic assembly
Neopentyl alcohol as surrogate for hydrogen - proof of principle demo
COLD HELIUM
FLUIDIZED BED WITH
GOLD PLATED (IR
REFLECTING) INNER WALL
INJECT IR
Two potential HIF layering methods identified
ASSEMBLED HOHLRAUMS ARE STAGED IN VERTICAL TUBES WITH PRECISE TEMPERATURE CONTROL
~1 mIn-hohlraum “tube” layering
Cryogenic fluidized bed layering
…Fluidized bed layering is can be used for either direct or indirect drive targets
Before
After
Manufacture of the hohlraum components and assembly
…Remote processing will be required for assembly
Begin with casting a Flibe sleeve to provide a structural support
Add 15 m high-Z layer by CVD or “exploding wire” (B)
B
Add high-Z (A) by LCVD
New die set & assemble precast foams (E,D,C)
Continue stacking (G,F,N,J,I)
Kapton film to hold capsule
Completed assembly with films to seal in gas (“H”)
2% W-doped 30 mg/cc CH foam
Laser-assisted Chemical Vapor Deposition is
being evaluated at LANL(J. Maxwell, IAEA-TM
June 17-19, 2002)
Main points and summary
• Target fabrication is one of the key feasibility issues for inertial fusion energy
• Target supply requirements are challenging- ~500,000/day precision, cryogenic targets with unique materials
- Low cost is required for economical power production
• Near-term goal of program is to provide a “credible pathway” for HIF target supply
• We have identified potential manufacturing processes that can be developed to supply the distributed radiator HIF target
Topics
• Direct drive target costing study
• Target injection and survival- Injector system status- Protection schemes for direct drive
• Indirect drive target fabrication- Feasibility- Materials selections- Status on costing study
Microencapsulation scaleup studies
Next Step: build modular components to demonstrate scaleup - microencapsulation
Lab-scale rotary contactor
~16 cm
Equipment dedicated to IFE development and scaleup (GA-funded; put in Bldg 22)
Provide shells for fluidized bed studies Determine viability and effects of scaleup
of rotary contactor (evaluate alternates)
Full-scale rotary contactor: 50x50 cm,
50% liquid, 8% shells by volume, 8h target supply
~1.4m
First shells!
Motion during curing is critical