Summary of Research in the Advanced Energy Technology Group at UC San Diego

1. Summary of Research in the Advanced Energy Technology Group at UC San Diego Farrokh Najmabadi and Mark Tillack March 2004 http://aries.ucsd.edu

2. Our Research Staff and Students

3. Summary of Research Activities • ARIES Fusion Concept Studies • High Average Power Laser Program • final optics • chamber clearing • dry-wall armor thermomechanics • cryogenic target survival • Inertial Fusion Energy Chamber Physics • magnetic diversion of ablation plumes • phase change physics • Laser-Matter Interactions • laser ablation plume dynamics and cluster formation • laser plasma EUV light source • Thermal Sciences

4. 1. ARIES Fusion Concept Studies

5. The ARIES Team has examined several magnetic and inertial fusion power plant concepts during the past 15 years • TITAN reversed-field pinch (1988) • ARIES-I first-stability tokamak (1990) • ARIES-III D-3He-fueled tokamak (1991) • ARIES-II and -IV second-stability tokamaks (1992) • Pulsar pulsed-plasma tokamak (1993) • SPPS stellarator (1994) • Starlite study (1995) (goals & technical requirements for power plants & Demo) • ARIES-RS reversed-shear tokamak (1996) • ARIES-ST spherical tokamak (1999) • ARIES-AT advanced tokamak (2001) • ARIES-IFE IFE chamber studies (2003) • ARIES-CS compact stellarator (ongoing)

6. R &D Needs, Development Plan R&D Program Concept studies incorporate customer require-ments and the existing database to assess concepts, innovate, and guide the base program Customer Input Present Data Base Mission and Goals Concept Studies Design Options Evaluation Based on Customer Attributes Attractiveness Characterization of Critical Issues Feasibility Redesign Assessment

7. ARIES integrated IFE chamber analysis and assessment research was a 3-year exploration study, recently completed Objectives: • Analyze & assess integrated and self-consistent IFE chamber concepts • Understand trade-offs and identify design windowsfor promising concepts.The research was not aimed at developing a point design. Approach: • Six classes of realistic target were identified. Advanced target designs from NRL (laser-driven direct drive) and LLNL (Heavy-ion-driven indirect-drive) were used as references. • To make progress, the activity was divided based on 3 chamber classes: • Dry wall chambers; • Solid wall chambers protected with a “sacrificial zone” (such as liquid films); • Thick liquid walls. • These classes of chambers were researched in series with the entire team focusing on each.

8. History of the UCSD IFE program vacuum system excimer laser Staff ramp-up new lab OFES proposal lab YAG 1997 1998 1999 2000 2001 2002 2003 2004 LLNL-funded studies of chamber simulation experiments OFES grant on chamber physics, modified to address final optics OFES grant on chamber physics (terminated) dry walls liquid walls ARIES-IFE DP HAPL programs GA target engineering

9. 2. High Average Power Laser Program

10. Our IFE research is focused on the key issues for IFE chambers and chamber interfaces • Final optics that survive the environment • Understanding of residual chamber medium and propagation of targets and beams through it • Chamber dynamic response, chamber clearing • Beam & target interactions • Chamber walls that survive or are renewable • Cryogenic targets that survive injection Prometheus-L Reactor Building

11. We are developing damage-resistant final optics based on grazing-incidence metal mirrors Objectives: • Measure laser-induced damage threshold and demonstrate long-term operation of a grazing incidence metalmirror at laser fluence of ~5 J/cm2 normal to the beam. • Determine limits due to contamination & other target threats. • Determine effects of damage on beam quality.

12. The SPARTAN chamber dynamics and clearing code was developed for studies of the post-blast chamber environment • 2-D Transient Compressible Navier-Stokes Equations. • Second order Godunov method, for capturing strong shocks. • Diffusive terms (conductivity, viscosity) depend on local state variables. • Adaptive Mesh Refinement for uniform accuracy throughout the fluid domain. • Arbitrary boundary resolved with Embedded Boundary method.

13. Cyclic thermomechanical behavior of dry-wall chamber armor is under investigation Temperature is calculated from measurement of radiated energy at two wavelengths: A fast (nanosecond) optical thermometer was developed to assist the project with time-resolved surface response measurements

14. Local Vapor Bubble ro tv,o DT Vapor Core Rigid DT Solid Plastic Shell + Survival of cryogenic direct-drive targets in hot, turbulent chambers is a challenging problem Thermal, mechanical and phase change studies were performed on cryogenic DT targets subjected to chamber heating t = 0.015 s Tinit = 18 K Pre-existing vapor bubbles could close if initial bubble is below a critical size and the heat flux above a critical value

15. 3. Inertial Fusion Energy Chamber Physics

16. Magnetic diversion of expanding laser plasma is being studied as a possible means to mitigate target debris

17. Phase change physics is important for under-standing the generation of impulse and behavior of aerosols in liquid-protected IFE chambers • Homogeneous nucleation and growth from the vapor phase • Supersaturated vapor • Ion-seeded vapor • Impurity-seeded vapor • Phase decomposition from the liquid phase • Thermally driven phase explosion • Pressure driven fracture • Hydrodynamic droplet formation (flow conditioning) Spinodal decomposition of Si (Craciun)

18. 4. Laser-Matter Interactions

19. 0.01 Torr 0.1 Torr 1 Torr 10 Torr 100 Torr Laser ablation plume dynamics is extremely complex, involving laser interactions, phase change, gasdynamics, atomic and plasma physics

20. Ionization was shown to play a dominant role in nanocluster formation in laser ablation plumes Polyimide laser ink-jet printer head (courtesy of HP) 5x109 W/cm2

21. We recently began a program of research on next-generation semiconductor lithography based on laser-plasma EUV emission Achieving higher efficiency and lower contamination are key issues for EUV light sources

22. 5. Thermal Sciences

23. Studies of heat transfer enhancement techniques are equally important in high heat flux applications (like fusion) and energy efficiency • Heat transfer in porous and granular media • Energy recovery ventilator • High heat flux devices Coaxial heat exchanger

24. UCSD Laser Plasma and Laser-Matter Interactions Laboratory