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)

Flowsheet for HIF targets

Preliminary hohlraum plant

layout over next few

months….

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