Update on IFE Target Fabrication Progress

1. 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

2. 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

3. The foam insulated target could significantly open the chamber design window! Basic target (18K): <0.68 W/cm2 (970Cor 2.8 mtorr Xe @ 4000K) Foam-insulated (100 m, 10%): <3.7 W/cm2 (970Cand 12.5 mtorr @ 4000K) Foam-insulated and 16K: <9.3 W/cm2 (970Cand 40 mtorr @ 4000K) Rene Raffray will talk more about target thermal…

4. ~ 1 m holes High-Z coat Insulating foam • Full-density CH “seal coat” • Permeable at room temperature • Seal at cryo to prevent DT loss • High-Z here increases fill time DT + foam Dense plastic (not to scale) DT solid “Basic” NRL Target DT gas 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

5. FOAM HEMI Glue joint Foam 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

6. 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

7. “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 shouldn’t be a problem if there are “many” approximately one micron sized holes (kHz laser?)

8. PAMS Bare foam Side-by-side PAMS and “bare” foam coated with Al Reflectivity of outer layer • Outer “reflective” layer on outer foam is still needed • total IR heat flux (970°C) = ~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

9. Example of reflectivity - PAMS and DVB Bare DVB with Al PAMS with Al (reflecting illuminator) micron-sized foam overcoated with metal is not reflective

10. Does the insulating foam collapse during injection? E = Young’s 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 g’s acceleration 10 ANSYS to evaluate survival • Ozkul* model (0.1 - 20 m cells, 40 - 270 mg/cc) • Use “Deshpande-Fleck Parameter+ (DFP) from ANSYS results • DFP< pl (foam will “spring back”) ~10X Log Deshpande-Fleck Parameter (DFP) @ 1000g Room temperature (conservative) 1 1 5 10 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 48:1253-1283

11. Force vs compression 450 400 350 300 250 Force (grams) 200 150 100 50 0 0 0.1 0.2 0.3 0.4 0.5 DVB foam compression (mm) 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 E=0.76 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

12. 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

13. 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 Design of mass production layering system is progressing Cryo-circulator bed HX Typical cryo-circulator

14. Design uses many borrowed ideas and commercial devices Heat Exchangers on Second Stage (OMEGA) Fluidized Bed Layering Device Bell Jar Design (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 24”ø Standard Evaporation Chamber Components Permeation Cell (D2TS, OMEGA, CPL) Transfer Arm (OMEGA) External Vacuum Manipulators (OMEGA) Cryogenic Compressor Cryocoolers (CPL, OMEGA)

15. 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

16. 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

17. 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 Remaining design is standard engineering, however, there are several developmental areas: Approach is to have a baseline design, yet keep things simple and modular, so that different concepts can be substituted

18. 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 ~ 1 m holes High-Z coat Insulating foam Summary and conclusions DT + foam DT solid DT gas