Update on IFE Target Fabrication Progress presented by Dan Goodin HAPL Project Review Madison, Wisconsin September 24, 2003 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

Topics 1.Foam Insulated Target Fabrication and Assembly 2.Foam Insulated Target Reflectivity 3.Insulating Foam Survival During Acceleration 4.Mass-Production Layering System Design 5.Summary and Conclusions NRL Basic High Gain Target

The foam insulated target could significantly open the chamber design window! Basic target (18K): <0.68 W/cm 2 (970  C or 2.8 mtorr 4000K) Foam-insulated (100  m, 10%): <3.7 W/cm 2 (970  C and K) Foam-insulated and 16K: <9.3 W/cm 2 (970  C and K) Rene Raffray will talk more about target thermal…

Additional advantage = reduces issue of DT inventory (filling time) Foam insulated target fabrication and assembly DT gas DT solid DT + foam Dense plastic (not to scale) “Basic” NRL Target ~ 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 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

Foam Glue joint 1)Hemi-shells (demonstrated, but not for IFE…) There are potential insulating- foam fabrication methods Injection molding, W. Steckle LANL Foam layer over shell by emulsification, M. Takagi CH Advantages Reproducible (same diameter & wall) Standard industry practices Foam with Pb 3) Chemical process (likely best for IFE …..) 2) Injection molding with NRL target (conceivable ….) FOAM HEMI By “shake and toss” (8 to 170  m walls)…

pulse Microencapsulation turns emulsification into mass-production 4 mm 150  m Want but Excess precursor results in 289  m thick foam Bubble injection Two approaches 1) Alternate with “beads” 2) Add Bubbles 10 % DVB + polymerization initiator(V70) in DEP One issue may be shrinkage rate of each layer after drying? “bead” Insulated foam target 0.05% PAA (or PVA) Stripping Flow 289  m Conclusion = microencapsulation to make insulating foam seems feasible, next we should try it

“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?)

Reflectivity of outer layer Outer “reflective” layer on outer foam is still needed –total IR heat flux (970°C) = ~14 W/cm 2 (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 Side-by-side PAMS and “bare” foam coated with Al PAMS Bare foam Result = “design window” curves for insulating foam and high-Z parameters to survive injection

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

Does the insulating foam collapse during injection? ANSYS to evaluate survival –Ozkul* model (  m cells, mg/cc) –Use “Deshpande-Fleck Parameter + (DFP) from ANSYS results –DFP<  pl (foam will “spring back”) NRL “basic” target - 4 mm OD - ~3 mg mass Insulating foam  m thick - variable density 1000 g’s acceleration Foam Density Ratio (%) Log Deshpande-Fleck Parameter 1000g E = Young’s modulus  f = density C1 = 0.38 Exponent = 2.29 *M.H.Ozkul, J.E.Mark, and J.H.Aubert. The Mechanical Behavior of Microcellular Foams, Mat. Res.Soc. Symp. Proc. Vol V.S.Deshpande, N.A.Fleck J.Mech.Phys.Solids 48:  pl = plastic stress  ys = yield stress of solid C2 = 0.15 Exponent = 1.85 Room temperature (conservative) ~10X Support film

Target remains centered in foam Must “spring back” from any significant de-centering “quickly” Simple experiments Data at RT, E at cryo typically 2 to 10 times higher (i.e., conservative) E=0.76 MPa 100 mg/cm 3 DVB Height = 4.5 mm Area = 63 mm 2 1-D estimates for compression of foam by accelerated target: …these data indicate the insulating foam will withstand acceleration and will remain centered Force vs compression DVB foam compression (mm) Force (grams)

Layering beds PlantExperiment Targets per bed65, Diameter bed320 mm34 mm Bed height, settled44 mm Bed expansion22 Operating temperature Kto ~15K Pressure of levitating fluid 380 torr Mass flow140 g/s1.8 g/s Velocity of fluid133 cm/s150 cm/s  T across bed (1 Q DT ; native  layering) 0.054K0.067K Temperature change at inner surface of DT ice <0.003K N. Alexander, HAPL Mtg., 4/2003 Mass-production layering system design 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

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

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

Operating Steps (1 of 2) 1) Basket w/700 empty capsules placed on 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 basket inserter permeation cell Bell Jar filled/cooled targets

Operating Steps (2 of 2) 6) Basket (w/ filled capsules) grasped by transfer arm 7) Transfer arm rotated 90 degrees Top View Note: view rotated 90˚ from other views 8) Basket placed on fluidized bed lower half 9) Fluidized bed lower half raised and sealed with upper half 10) Capsules layered and characterized filled/cooled targets transfer arm filled/cooled targets cryogenic fluidized bed gas supply lines

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

Summary and conclusions 1.We think the insulated-foam target can be reasonably fabricated for IFE 2.The insulated-foam target reduces issues associated with filling time 3.The insulating foam can be “drained” of DT 4.Insulating foam will survive the acceleration during injection and remain centered 5.Demonstration system for mass-production layering is being designed DT gas DT solid DT + foam ~ 1  m holes High-Z coat Insulating foam