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Update on Target Fabrication Tasks

Update on Target Fabrication Tasks. Presented by Dan Goodin at ARIES Meeting San Diego, California July 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

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Update on Target Fabrication Tasks

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  1. Update on Target Fabrication Tasks Presented by Dan GoodinatARIES MeetingSan Diego, CaliforniaJuly 1-2, 2002

  2. 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

  3. 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 • Chemical engineering approach to Target Fabrication Facility (TFF) • Costing is done for an “nth-of-a-kind” plant • Results guide process development NRL radiation preheat target 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)

  4. 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 7200 ft2 experimental space is being refurbished for use in IFE research Tracking detector housing Opto 22 input/output hardware

  5. 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)

  6. Wake shield target heating protection calculations have been carried out 1. Convective heat load is calculated as a function of target-shield separation 2. Drag is calculated as a function of target-shield separation 3. The relative motion of the target and shield is optimized 4. Average heat flux on the target is then calculated P = 50 mTorr T= 1000 K V= 400 m/s Shield radius = 5 mm By E. Valmianski

  7. Membrane target protection scheme was conceived Support frame Target support membrane Must verify ~1000 Å film does not adversely affect target performance and gas film of appropriate variable thickness can be applied Heat barrier membrane coated with frozen gas By R. Petzoldt and M. Shmatov

  8. 4 3.6 Unprotected target 3.2 2.8 2.4 Target with thin shield 2 1.6 1.2 0.8 0.4 Target with cone 0 0 1 2 3 4 5 6 Distance along target (mm) A cone used with fast ignition reduces max heat flux more than a flat shield Radius of the shield - 4mm Radius of the target - 2 mm Temperature -1773 K Density STD - 50 mtorr Speed - 400 m/s 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.

  9. 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 HIF2002 Moscow May 26-31, 2002

  10. Indirect drive target fab - main points • 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 …. A significant R&D program will be necessary to demonstrate and scaleup these processes

  11. The distributed radiator target of Tabak and Callahan is the reference HIF design • Two sided illumination by heavy ion beams • Energy deposited along hohlraum materials • Radiation distribution tailored by material density • Unique materials required LLNL Close-Coupled Heavy Ion Driven Target Debbie Callahan Invited Talk At HIF2002 … Costs per target of about $0.30 are needed for economical electricity production (Woodworth and Meier UCRL-ID-117396, 1995)

  12. The heavy-ion driven target has a number of unique and challenging materials 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/cc I: Al 0.055 g/ccJ: AuGd “sandwich” 0.1/1.0/0.5K: DT 0.0003 g/cc L: DT 0.25 g/cc M: Be0.995Br0.005 1.845 g/ccN: (CD2)0.97Au0.03 0.032 g/cc Nuclear Fusion 39, 1547 The distributed radiator target of Callahan and Tabak is the reference HIF design … Simplification and material substitutions are needed to reduce complexity of the target

  13. Pathways to simplify the target are being defined Material substitutions are defined in conjunction with target designers to reduce target cost PartMaterialAlternate Materials A AuGd [high-Z only] Various - Au, Pb/Ta, Pb/Ta/Cs, Hf/Hg/Xe/Kr B AuGd [high-Z only] Various - Au, Pb/Ta, Pb/Ta/Cs, Hf/Hg/Xe/Kr C Fe Au-doped CH foam D (CH)0.97 Au0.03 -- E AuGd [high-Z only] Various - Au, Pb/Ta, Pb/Ta/Cs, Hf/Hg/Xe/Kr F Al Silica aerogel G AuGd [high-Z only] Various - Au, Pb/Ta, Pb/Ta/Cs, Hf/Hg/Xe/Kr H CD2 He gas I Al CH or doped CH J AuGd sandwich (high-Z only) Various - Au, Pb/Ta, Pb/Ta/Cs, Hf/Hg/Xe/Kr K DT -- L DT -- M Be0.995Br0.005 Polystyrene (CH) N (CD2)0.97Au0.03 -- Physics of Plasmas, May 2000, pp. 2083-2091 Recent Material Choices (Loss compared to Au/Gd D. Callahan) Au or Pb ~10-15% gain loss Pb/Hf ~2% gain loss Pb/Hf/Xe ~0% gain loss

  14. Process steps for target fabrication are challenging 1) Fabricating the spherical capsule 2) Fabricating the hohlraum case 3) Fabricating the radiators 4) Filling the capsule with fuel 5) Cooling the capsule to cryo 6) Layering the DT into shell 7) Assembling the cryo components 8) Accelerating for injection 9) Tracking the target’s position 10) 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 .... Process development programs for target fabrication and target injection are underway

  15. There are many decisions to be made when selecting a target supply pathway Step Methods Comments/Issues Capsule Fabrication Microencapsulation Simple, suitable for hi-volume Issues: sphericity, non-concentricity GDP 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 inventory Liquid filling Developmental, capsule damage Layering Fluidized bed Demo’d in principle, req’s fast assembly In-hohlraum Extreme precision/uniformity Hohlraum Comp. Fab Casting For Flibe sleeve, remote handling LCVD For hi-Z matl’s, developmental, cost Metal foams Pore sizes, density Wire arrays Uniformity, structural integrity Doping of CH foams For radiator matl’s, mass-prod methods, handling, precision Target 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

  16. Fluidized beds for mass-production of capsules is being investigated 7.3 m PAA coating PAMS mandrel Coating Mandrel ~ 3 micron thick GDP coating on PAMS ~ 7 micron thick PAA coating on PAMS Polyamic acid  polyimide coating PAMS Mandrels in Fluidized Bed Aerosol microspray of polyamic acid solution; 4-8 micron droplet size Experimental system …. These coating methods are all two-step processes

  17. Direct capsule fabrication by microencapsulation 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) Approaching IFE Requirements! Laboratory scale rotary contactor NIF Spec (green) ~16 cm Microencapsulation may be most cost-effective pathway...

  18. Preliminary “Target Fabrication Facility” (TFF) layout Full-scale rotary contactor: 50x50 cm, 50% liquid, 8% shells by volume, 8h target supply ~1.4m Ethanol/Water Exchange & Vacuum Drying 80’ 100’ PS shell generation QA/QC Lab Hohlraum Production Area Hohlraums DT Filling (Permeation Cells) Preliminary cost estimates indicate ~$0.11 per capsule for capsule fabrication, filling, and layering (not including hohlraum materials and assembly) Hohlraum Cryo-Assembly Layering (Fluidized Bed) Injector To Chamber

  19. 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 JET PIERCE NEEDLE Hohlraum cryo-assembly “Advanced” methods of filling have also been evaluated 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 Methodology by A. Schwendt, A. Nobile (LANL), Fusion Science and Technology (to be published) Pressure cell with trays

  20. Layering in-hohlraum or not? • In-hohlraum layering Three routes for indirect drive target processing are possible: Cold Assemble Hohlraum Layer DT Ice Cool to Cryo Temps Evacuate DT Layer DT Ice DT Diffusion Fill Capsule Hohlraum Cryogenic Assembly • Fluidized bed layering of capsules “Cold Assembly” Manufacture Materials Inject “Warm Assembly” Assemble Hohlraum Layer DT Ice DT Diffusion Fill Evacuate DT Cool to Cryo Temps • Warm Assembled Hohlraum …Tritium inventory will likely require cryogenic assembly

  21. INJECT IR FLUIDIZED BED WITH GOLD PLATED (IR REFLECTING) INNER WALL COLD HELIUM Two potential HIF layering methods identified ~1 m In-hohlraum “tube” layering Cryogenic fluidized bed layering ASSEMBLED HOHLRAUMS ARE STAGED IN VERTICAL TUBES WITH PRECISE TEMPERATURE CONTROL Before After Neopentyl alcohol as surrogate for hydrogen - proof of principle demo …Fluidized bed layering is can be used for either direct or indirect drive targets

  22. Manufacture of the hohlraum components and assembly Begin with casting a Flibe sleeve to provide a structural support New die set & assemble precast foams (E,D,C) B Kapton film to hold capsule Add 15 m high-Z layer by CVD or “exploding wire” (B) Continue stacking (G,F,N,J,I) Add high-Z (A) by LCVD 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) Completed assembly with films to seal in gas (“H”) …Remote processing will be required for assembly

  23. Flowsheet for HIF targets Preliminary hohlraum plant layout over next few months….

  24. 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

  25. 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

  26. Next Step: build modular components to demonstrate scaleup - microencapsulation • 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) ~16 cm First shells! Lab-scale rotary contactor ~1.4m Full-scale rotary contactor: 50x50 cm, 50% liquid, 8% shells by volume, 8h target supply Motion during curing is critical

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