Considerations in Developing Ion Dump Design

1. Considerations in Developing Ion Dump Design A. René Raffray UCSD HAPL MI Chamber Core Meeting UCSD, La Jolla, CA January 30-31, 2007 HAPL Chamber Core meeting, UCSD

2. Separate Ion Dump Chamber for MI Case • Dry wall main chamber to satisfy target and laser requirements. • Separate phase-change dry wall or wetted wall chamber to accommodate ions and provide long life. • Minimal impact on main chamber environment HAPL Chamber Core meeting, UCSD

3. Candidate Armor Concepts for Separate Ion Dump Chamber Include: • Single phase solid armor (W) High Temp. C? - A key concern is lifetime (effect on He retention and cyclic thermal stresses) • Solid armor with phase change (W, Be, Cu) - A key concern is stability of melt layer and quality of resolidified material • Wetted walls (Pb, Pb-17Li, flibe) - A key concern is prevention of contamination of main chamber environment HAPL Chamber Core meeting, UCSD

4. Scoping Analysis of an Example Ion Dump Ring Chamber Armor Structure Coolant Rmajor Rmin • Some flexibility in setting chamber major and minor radii so as not to interfere with laser beams • e.g., with Rmajor/Rminor =8/2.7 or 9/2.4 m, and assuming 35% of wetted wall area sees ion flux with a peaking factor of 1: - Ion dump area = 300 m2 - From 0 to 0.5 s, q” = 4.51x1010 W/m2 - From 0.5 to 1.5 s, q’’= 6.53x1010 W/m2 • Dry Wall Armor (including possibility of phase change) - W and Be - Cu or Be, possibly within high porosity W microstructure (~80-90%) for integrity and melt layer retention • Wetted Wall - Pb-17Li, flibe and Pb HAPL Chamber Core meeting, UCSD

5. Temperature and Phase Change Thickness Histories for W, Be, Cu, Pb, Pb-17Li and Flibe for Example Case • 350 MJ target (ion energy = 87.8 MJ) • Ion dump area = 300 m2 • From 0 to 0.5 s, q’’ = 4.51x1010 W/m2 (7.7% of ion energy) • From 0.5 to 1.5 s, q’’= 6.53x1010 W/m2 (22.3% of ion energy) HAPL Chamber Core meeting, UCSD

6. Maximum Temperature and Phase Change Thicknesses for W, Be, Cu, Pb, Pb-17Li and Flibe as a Function of Ion Dump Area • 350 MJ target (ion energy = 87.8 MJ) • Evaporation loss per shot relatively modest for W but could be a concern for Cu or Be (1 nm/shot ~ 0.43 mm/day) • Stability of melt layer is a concern (~10m for Cu or Be; ~ 1 m for W) • For wetted wall in particular, the evaporated material (~10 m for Pb-17Li, Pb or flibe) must recondense within a shot and not contaminate main chamber HAPL Chamber Core meeting, UCSD

7. Wetted-Wall Concept Could Consist of a Porous Mesh Through Which Liquid (Pb-17Li or flibe) Oozes to Form a Protective Film Liquid film Porous mesh Liquid flow Pump Liquid recycling • Need to make sure that protective film is reformed prior to each shot - radial flow through porous mesh - circumferential flow of recondensed liquid - no concern about any droplets falling in chamber HAPL Chamber Core meeting, UCSD

8. Film Condensation in Ion Dump Chamber for Pb-17Li and Flibe • Scoping calculations previously done for Pb as example. • Now extended to Pb-17Li and Flibe as they are used as breeder/coolant in the blanket. • Ion energy from 350 MJ target = 87.8 MJ - 7.7% of ion energy to dump over 0-0.5 s - 22.3% of ion energy over 0.5-1.5 s • Evaporated thickness and vapor temperature rise from ion energy deposition in ion dump chamber. • Assume ion deposition area = 300 m2 - e.g. 35% of chamber with Rmajor = 9 m and Rminor = 2.4 m jevap Pg Tg Tf jcond jnet = net condensation flux (kg/m2-s) M = molecular weight (kg/kmol) R = Universal gas constant (J/kmol-K) G = correction factor for vapor velocity towards film sc, se = condensation and evaporation coefficients Pg, Tg = vapor pressure (Pa) and temperature (K) Pf, Tf = saturation pressure (Pa) and temperature (K) of film HAPL Chamber Core meeting, UCSD

9. Scoping Analysis of Pb-17Li Condensation in Example Ring Chamber • Characteristic condensation time very fast, < 0.024 s • It takes < 0.24 s for vapor density to reach saturation for final vapor temperature > 773 K (assuming linear temporal decrease of vapor temperature from initial to final value). HAPL Chamber Core meeting, UCSD

10. Scoping Analysis of Flibe Condensation in Example Ring Chamber • Characteristic condensation time very fast, < 0.02 s • It takes < 0.202 s is for vapor density to reach saturation for final vapor temperature > 773 K (assuming linear temporal decrease of vapor temperature from initial to final value). HAPL Chamber Core meeting, UCSD

11. Size of Ion Dump To Avoid W Melting • Assuming ~30% of ion energy is deposited in dump, ~450-500 m2 is required • If 6% of ion energy escaped at one pole, ~90-100 m2 would be required (e.g. a circular plate of diameter ~10-11 m, very large) • Design of top ion dump challenging also because of need to avoid contaminating chamber (working against gravity in case of melt layer loss for solid armor or of drop formation for wetted wall concept) HAPL Chamber Core meeting, UCSD

12. Ions Surface replenish Rotating Drum Concept • Octagonal shown as example (could be hexagonal or…) • ~3-5 mm thick W drum cooled by radiation to blanket • armor drum rotation around stationary blanket (at the end of exposed armor lifetime) • armor surface replenished at the back (e.g. by plasma spray) • For 800 K blanket, W back wall temperature of ~2000K required for effective steady heat transfer Blanket/shield HAPL Chamber Core meeting, UCSD

13. Extra Slides on Main Chamber HAPL Chamber Core meeting, UCSD

14. 10%W/90%Cu W Structure Coolant Momentary Liquid Walls in Main Chamber (allowing solid to melt and resolidify) • Allowing W armor itself to melt is an option but concerns about stability of melt layer and integrity of high temperature solid W under melt layer • Other possibility is to use a lower MP material in a W structure - e.g. >90%Cu in <10% W structure - How to fabricate it? - Structure size to provide good melt layer retention through capillarity (microstructure size to be optimized for melt layer retention and integrity) HAPL Chamber Core meeting, UCSD

15. Histories of Temperature and Phase Change Thickness for a Cu Armor as a Function of the Chamber Sizes for the 350 MJ Target • 1-mm Cu on 3.5 mm FS at 580 °C • No chamber gas • Can the W mesh be maintained at a reasonable temperature acceptable lifetime? (~1250°C for 10.75 m chamber) • Stability of ~3-10 m melt layer of Cu • Minimal evaporation, ~0.0001 nm on average per shot for 10.75 m chamber, ~ 1 g per shot HAPL Chamber Core meeting, UCSD