1. DOE DP This work was performed under the auspices of the U. S. Department of Energy by the Los Alamos National Laboratory under contract No. W-7405-Eng-36. ESA-TSE Engineering Sciences and Applications Division Tritium Science & Engineering Update on Solid DT Studies Drew A. Geller, James K. Hoffer, & John D. Sheliak presented at the High Average Power Laser Workshop sponsored by The Department of Energy Defense Programs hosted by the Georgia Institute of Technology Atlanta, Georgia, February 5-6, 2004 LA-UR-04-0635

2. HAPL @ GA Tech Feb ‘04 Overall Objective…………. Response of target materials to injection stresses FY 04 Deliverables………..1. Complete final drawings for elastic modulus/yield strength experiments. 2. Measure the roughness spectrum of DT beta- layered inside a 200 micron thick layer of foam material. 3. Fabricate apparatus for elastic modulus/yield strength experiments. 4. Deposit a layer of DT inside a foam-lined heater winding and study thermal response. Relevance of Deliverables [X] Energy………………Needed for injection into hot chamber [X] NIF……………………Research on materials in NIF targets Target Injection: Target Materials Response - LANL

3. HAPL @ GA Tech Feb ‘04 Progress report: deliverable No. 3, ‘03 Experiments on the Direct Heating of a Solid DT Layer

4. HAPL @ GA Tech Feb ‘04 epoxy layer coil A new beta-layering cell was designed and fabricated.

5. HAPL @ GA Tech Feb ‘04 The thermal modeling (ANSYS) continues. We use FEA to estimate the heat flux into the DT layer as a function of current into the manganin coil. –The flux into DT varies in time. –Some heat is lost to the copper support ring. –Some heat is lost to heat capacity of the epoxy insulating layer and of the coil itself. We can use FEA to determine the time at which solid begins to melt. –For low enough currents (< 30 mA) the DT layer will never melt.

6. HAPL @ GA Tech Feb ‘04 Early experiments at low heat fluxes 360 micron layer at 19 K, ~0.04 W/cm 2 Ice on windows is visible because of large depth-of-field of camera lens. Ice appears black near coil due to rounding at ends of cylinder. As the solid is heated, material is desorbed and re-condenses on the windows. t=0 s t=18 s

7. HAPL @ GA Tech Feb ‘04 Early experiments at higher heat fluxes 360 micron layer, 19 K ~0.26 W/cm 2 duration 1 s (x6.25 in movie) Note: We can observe the melting front propagate through the layer! (Appears after ~0.5 s) Some bubbles are seen to form near the coil.

8. HAPL @ GA Tech Feb ‘04 A longer time view 360 micron layer, 19 K ~0.26 W/cm 2 duration 4.4 s (x4.2) Note: Inner surface remains intact after outer surface becomes liquid. Liquid may flow out ends of coil.

9. HAPL @ GA Tech Feb ‘04 New optics yield a clearer image.

10. HAPL @ GA Tech Feb ‘04 Later experiments at higher fluxes 460 micron layer, 19 K ~0.5 W/cm 2 duration 0.2 s (x50) ~10 micron diameter bubbles appear after 20 ms (top of image) Layer brightens after 8 ms.

11. HAPL @ GA Tech Feb ‘04 Later experiments at higher fluxes 460 micron layer, 18 K (layered for 1.8 hrs) ~0.9 W/cm 2 duration 0.1 s (x50) After 12 ms, bubbles appear.

12. HAPL @ GA Tech Feb ‘04 Later experiments at higher fluxes 460 micron layer, 18 K (layered for 1.8 hrs) ~0.9 W/cm 2 duration 0.1 s (x50) After 16 ms, bubbles appear. Bubbles in the solid vs. bubbles formed at the boundary? Are the bubbles DT vapor? Layer explodes after 92 ms.

13. HAPL @ GA Tech Feb ‘04 The bubbles may be due to 3 He. 1.8 hrs19.6 hrs 460 micron layers at 18 K subjected to ~ 0.9 W/cm 2 for 24 ms after two different layering times:

14. HAPL @ GA Tech Feb ‘04 Shortcomings of the cell For slow heat fluxes, liquid DT is not confined at the cylindrical coil’s ends. For layers thinner than ~ 430 microns, we can not see the edge of the coil through the solid. Rounded edges of layer cause distortion of the image inside the layer. DT adsorbed on the windows is visible as a non-uniform haze in the images.

15. HAPL @ GA Tech Feb ‘04 A possible improvement to the experiment Insertion of windows at the ends of the coil will provide a clearer view through the layer and will confine the material at the ends. Thickness of windows must be carefully chosen to leave only small gaps at ends of the cell.

16. HAPL @ GA Tech Feb ‘04 Conclusions We have begun experiments on direct heating of the DT fuel layer. We rely on ANSYS FEA to determine the actual heat flux from the coil into the layer. Bubbles, probably of 3 He, appear at very early times in the solid. Insertion of windows at the ends of the coil may prevent formation of late-time vapor bubbles in the liquid. Early formation of 3 He bubbles at 1 W/cm 2 may indicate that higher fluxes are not acceptable.

17. HAPL @ GA Tech Feb ‘04 Still to do: Go to higher fluxes. Analyze roughness of inner surface. Insert windows at ends of coil. Analyze temperature transient data. Improve FEA model for better agreement with experiment.

18. HAPL @ GA Tech Feb ‘04 Calculated flux into DT vs. time ANSYS model for 160 mA into coil Spike indicates melting transition.

19. HAPL @ GA Tech Feb ‘04 Later experiments at higher fluxes and lower temperatures. 460 micron layer, 15.5 K (layered for ~3 hrs) ~0.9 W/cm 2 duration 0.1 s (x50) After 48 ms, bubbles appear.

20. HAPL @ GA Tech Feb ‘04 Later experiments at higher fluxes 460 micron layer, 19 K ~0.5 W/cm 2

21. HAPL @ GA Tech Feb ‘04 Fabrication of the D-T Strength Cell special thanks to Roberto Jordan, Murphy’s Meadow Design Services. Progress report: deliverable No. 3, ‘04

22. HAPL @ GA Tech Feb ‘04 Several parts have yet to be manufactured. “Cold-lab” test and calibration cryostat. -Commercial refrigerator with compressor is available, and -plans for vacuum cans and thermal shields exist, but -parts still need to be machined. Primary containment vessel. -Machining is mostly completed. Layering posts. -Not started. Bellows seal. -Not started.

23. HAPL @ GA Tech Feb ‘04 Vertical adjustment for bottom layering post is completed. Micrometer Stainless base Dowel pin

24. HAPL @ GA Tech Feb ‘04 Early experiments at low heat fluxes 360 micron layer @ 19 K ~0.04 W/cm 2, duration 18 s Note: Ice on windows is visible because of large depth-of- field of camera lens. Ice appears black near coil due to rounding at ends of cylinder. As the solid is heated, material is desorbed and re- condenses on the windows.

25. HAPL @ GA Tech Feb ‘04 Later experiments at higher fluxes 460 micron layer, 18 K (layered for 1.8 hrs) ~0.9 W/cm 2 duration 0.37 s (x62) After 12 ms, bubbles appear.