Advancing Fusion Energy Technology: Virtual Laboratory Insights

1. Briefing for 11/17/99 Dr. Michael Holland Office of Management and Budget November 19, 1999 Washington, DC by Dr. Charles C. Baker Director, Virtual Laboratory for Technology University of California, San Diego Prof. Farrokh Najmabadi Head, National Fusion Power Plant Studies Program (ARIES) University of California, San Diego Dr. Steven Jardin Princeton Plasma Physics Laboratory VLT Virtual Laboratory for Technology

2. 11/17/99 Main Topics • The role of enabling technology in the Fusion Energy Sciences Program. Science requires technology. • Contributions of advanced design and analysis activities. Continuing guidance to fusion science program. • Contributions to advances in engineering and material sciences. Benefits to other fields of science. VLT Virtual Laboratory for Technology

3. 11/17/99 Plasma science and technology is a partnership.. Three Themes 1. Technology enables plasma science research and is critical to the advancement of MFE confinement and IFE driver concepts. 2. Technology and materials innovation are necessary to develop our vision of an attractive fusion energy source. 3. Technology research makes substantial contributions to fundamental engineering and materials sciences. Advanced design and analysis activities guide fusion research. VLT Virtual Laboratory for Technology

4. The Technology Program is a multi-institutional national resource. 11/17/99 MIT LANL ORNL ANL GIT INEEL SRL ILL. LLNL RPI PNL VLT UCB SNL PPPL UCSD UCLA UCSB Raytheon Laboratories Universities Industries TSI Lockheed Martin Maryland Boeing WIS. Bechtel General Atomics SAIC VLT Virtual Laboratory for Technology

5. 11/17/99 A Virtual Laboratory for Technology Mission: VLT Provide leadership and coordination for community participation in the Technology Program including recommendations on priorities and Resources. Virtual Laboratory for Technology For Fusion Energy Science Visit the VLT Web site at: http://vlt.ucsd.edu • Mechanism for organizing and integrating widely distributed performing institutions. • Includes MFE technologies and IFE chamber and target technologies. • Enhanced use of peer review to ensure high quality of research activities. • VLT Director serves as a principal representative and spokesperson for Technology in the larger fusion community. VLT Virtual Laboratory for Technology

6. 11/17/99 Advanced Design and Analysis activities incorporate state-of-the-art scientific models and help guide fusion research. • National Fusion Power Plant Studies Program. Recent studies completed: –ARIES-RS reversed-shear tokamak; –ARIES-ST spherical torus. Current focus is on advanced tokamaks. • Assessment of near-term applications of fusion neutrons. • Assessment of IFE critical issues. • Concept exploration studies. • Studies of markets, customers, and the role of fusion in a sustainable global energy strategy. VLT Virtual Laboratory for Technology

7. 11/17/99 Advanced Design Program Performs Integrated Analysis • Detailed and in-depth analysis is necessary to make scientific progress and impact the R&D program: Interaction and trade-off among plasma parameters (MHD b limit, heating & current-drive, divertor, transport); Interfaces between fusion plasma and other components (e.g., restriction on plasma elongation by location of stabilizer, and triangularity by inboard divertor slot) Invoke physics and engineering constraints which are not in present-day experiments (e.g., simultaneous high power and high particle flux to divertor) • In many areas models and tools necessary to analyze fusion systems are developed. VLT Virtual Laboratory for Technology

8. 11/17/99 Advanced Design Program Identifies Key R&D Issues and Provides a Vision for the Program What is important ARIES Program What is possible Progress in Plasma Physics: Physics Limits Macroscopic stability Wave-particle interaction Microturbulence & transport Plasma-material interaction • • • • Theory Program Stimulus for new ideas What has been achieved Experiments What to demonstrate ARIES studies have influenced research priorities in each of these areas and have been guided by new experimental trends and theoretical concepts. VLT Virtual Laboratory for Technology

9. Advanced Design Program Has Had A Major Impact on Tokamak Research Major Physics Results 11/17/99 Impact on the Program • Introduced the trade-off between plasma b and bootstrap current. • Showed that high-field magnets can be utilized to compensate for low b. Initiation of Advanced Tokamak Research. • Showed that true benefit of 2nd Stability regime was to reduce the current-drive power not increased b.  KSTAR construction and TPX experiment design were influenced significantly. • Demonstrated that (1) in pulsed-tokamaks the plasma b is limited by ohmic profile constraint, (2) physics of pulsed and steady-state tokamaks are essentially the same; (3) steady-state out- performs pulsed operation because of technological constraints.  Major theoretical and experimental activities on advanced tokamaks. ARIES-RS is the present goals of advanced tokamak research (DIII-D, C- Mod, FIRE). Recognition at Snowmass that any burning plasma experiments must have advanced tokamak capability. • Developed reversed-shear equilibria appropriate to power plants. It included a self-consistent divertor/plasma edge conditions with acceptable impact on ideal MHD, current drive, and power balance. VLT Virtual Laboratory for Technology

10. 11/17/99 Tokamak Research Has Been Influenced by the Advanced Design Program Current focus of tokamak research “Conventional” high-b b tokamaks (Pulsed operation) 2nd Stability high-b b tokamaks (Too much bootstrap)  Plasma b) b) Advanced tokamak (balance d bootstrap) bA/S ( b PU: Pulsed Operation SS: 2nd Stability FS: 1st Stability, steady-state RS: Reversed-shear b bp/A (  Bootstrap current fraction) VLT Virtual Laboratory for Technology

11. Advanced Design Program Has Had A Major Impact on Alternative Concept Research 11/17/99 Major Scientific Results Impact on the Program • Spherical Torus: Developed the first self- consistent stability and current-drive calculations of high-b, high bootstrap current ST equilibria. Showed that high plasma elongation (k = 3) is necessary. Showed resistive ST center-posts can be designed to operate in power-plant conditions  NSTX is influenced by ARES-ST The next step in ST program, DTST, uses ARIES-ST as the target. • Stellarator: Developed a new stellarator magnetic configuration to address the issue of large size. Initiated a large interest in compact stellarator research in US. • Reversed-Field Pinch: Identified the need to operate with a highly radiative core, poloidal divertors, and an efficient current drive system so that a compact RFP can be realized. Experiments on ZT-40 with a highly radiative core and helicity-injection current- drive. ZT-P device was built to study poloidal divertors for RFPS; Design and experimental program on ZT-H were modified to address these issues. VLT Virtual Laboratory for Technology

12. 11/17/99 The ARIES-ST Study Has Identified Key Directions for Spherical Tokamak Research Substantial progress is made towards optimization of ST equilibria with >95% bootstrap fraction:  b b = 54%, k k = 3 • A feasible center-post design has been developed. • Several methods for start-up have been identified. • Current-drive options are limited. • 1000-MWe ST power plants are comparable in size and cost to advanced tokamak power plants. • VLT Virtual Laboratory for Technology

13. Advanced Design Program Has Had A Major Impact on Fusion Technology Research 11/17/99 Major Fusion Engineering Results Impact on the Program • Introduced SiC composites as a high- performance fusion material. Large world-wide research activity on SiC composites material. • Explored gas injection and impurity radiation to reduce heat load in the divertors. Experiments in linear plasma machine and later in large tokamaks. • Innovative superconducting magnet designs using plates and a structural cap (later used in ITER). Current goals of magnet R&D program. Spurred interest in RF current drive experiments (e.g., fast-wave current drive in DIII-D in mid 90s). • Demonstrated benefits of RF systems (especially fast waves) for current drive and the respective launchers (e.g., folded wave-guides). Application in next-generation experiments. • Introduction of advanced manufacturing techniques which reduce the unit costs of components drastically. Direct impact on research on fusion materials and chamber technologies • Emphasis on safety & environmental aspects of fusion. VLT Virtual Laboratory for Technology

14. 11/17/99 Impact of Latest Developments in Other Scientific Disciplines Are Continuously Considered. Examples include: • SiC Composites (Aerospace) • High-temperature superconductor • Advanced manufacturing techniques (Aerospace) • Advanced engineered material for high heat-flux components VLT Virtual Laboratory for Technology

15. 11/17/99 Engineered Microstructure of Porous Media Enables High Heat Flux Removal Enhanced heat transfer surface area Increased turbulence and boundary layer modification near heat transfer surface Reduced radiation opacity • • • Ultramet Foam ESLI High Porosity Fibrous material VLT Virtual Laboratory for Technology

16. 11/17/99 National Advanced Design Program Allows Fusion Scientists to Investigate Fusion Systems Together • The team comprises key members from major fusion centers (universities, national laboratories, and industry). A typical team member spends 25% of his time on this activity. About 2/3 of resources is allocated to universities this year. Seven students were supported last year. • Decisions are made by consensus in order to obtain the best technical solution without institutional bias. • Team is flexible and expert groups and advocates are brought in as needed to ensure the flow of the latest information from R&D program. As such, high- leverage issues are readily transferred back to the R&D program. • Workshops and “Town Meetings” are held for direct discussion and dissemination of the results • Because we draw from expertise of the national program, we are unique in the world in the ability to provide a fully integrated analysis of power plant options including plasma physics, fusion technology, economics and safety. VLT Virtual Laboratory for Technology

17. 11/17/99 IFE Chambers Requirements and Options • About 100 MJ of X-rays and debris Ions are released by the target over about 10 ns. For a practical chamber size, the energy load on an “un-protected” chamber wall is about 2GW/m2 Options: • Gas Protection: Low-density high-Z gas in the chamber absorbs X-rays and debris and radiate in 0.1 to 100 ms. • Wetted Walls: Thin liquid layer absorbs the incident energy. The evaporated material recondenses on the chamber wall. • Thick Liquid Wall: Energy yield is absorbed by regenerating liquid walls. • For each option, the chamber environment should return to its “normal” condition in about 100 to 200 ms. VLT Virtual Laboratory for Technology

18. 11/17/99 Integrated Analysis of IFE Chambers Requires State-of-the-Art Analysis in Several Areas • Material response to intense target yield: Response of the solid and liquid material (chamber wall and final optics) and gases to intense target emissions (plasma, X-rays, neutrons). • Chamber clearing: Understanding the limits on chamber clearing rates set by radiation cooling from optically thick and/or thin plasma-gas regimes, followed by molecular recombination, and then condensation on surfaces or droplets. • Beam Transport: Investigation of beam transport (lasers/heavy ions) through final optics and chamber in plasma-gas environment. • Target Injection and Heating: Understanding the effects of target heating on cryogenic fuel layers due to thermal radiation, conduction, and convection in the chamber. Investigation of the impact of chamber environment on target trajectory. VLT Virtual Laboratory for Technology

19. 11/17/99 National Advanced Design Program Is a High- Leverage Research Effort • High Quality of Science: Detailed and in-depth analysis is necessary to make scientific progress. • High-Leverage Research: Integrated design & analysis beyond current experiments identifies key R&D Issues. • Community input and consensus: An environment is created for fusion scientists to investigate fusion systems together. Team members bring in the latest information from R&D program. State-of-art analysis, innovation, and high-leverage issues are readily transferred back to the R&D program. • Interaction with other disciplines: Impact of latest development in other scientific fields on fusion systems are evaluated. • Impact on Education: Approximately 2/3 of the research is performed by universities (UCSD, U. Wisc., RPI, MIT). Seven students were supported by this activity last year. • A high-leverage niche on the international fusion program. It is recognized internationally as a credible driving force towards an attractive end product and influences world-wide fusion research. VLT Virtual Laboratory for Technology

20. 11/17/99 The unique environment of a fusion plasma requires advances in the engineering sciences. • Materials science • Fluid dynamics and magnetohydrodynamics • Plasma-material interactions • Surface science and atomic physics • Heat and mass transfer, thermomechanics • Chemistry • Aerosol science • Magnet science and superconductivity • Beams, accelerators & coherent radiation generation • Nuclear science VLT Virtual Laboratory for Technology

21. 11/17/99 Technology Research Contributes to Engineering and Materials Science Molecular dynamics simulations provide fundamental under- standing of damage mechanisms and allow extrapolations from fission data Liquid metal magnetohydrodynamics and turbulence in open (free surface) and closed channel flows push the frontiers of fluid sciences Surface physics, combined with molecular processes in a magnetized plasma boundary region, lead to highly complex phenomena with relevance to plasma processing and other near-term applications VLT Virtual Laboratory for Technology

22. 11/17/99 Plasma Technologies are required for fusion science. Achieve and Sustain Advanced Plasma Performance: Fusion power density: pf ~ <b b2 > B4 b/c)a2B2 Burn condition: nTt t ~ (b • Profile Control Technologies: • Heating/current drive/fueling: • Increase b and b limits • Reduce c, generate ITB • Magnet Technology: • High performance, low cost: • Improved strand, insulation, structural materials, thermal isolation, quench protection, joints • PFCs/PMI: • Plasma boundary control for edge transport barriers • High heat flux/low erosion PFC’s to cope with higher power densities • Disruption Mitigation/Control: • Pellet/gas/liquid injection: • Enable operation near ultimate b potential VLT Virtual Laboratory for Technology

23. 11/17/99 The Levitated Dipole Experiment (LDX) A Science-Technology Partnership 1.3 MA, 0.8 m diameter, 5T Floating Coil Experiment for High- Temperature Plasma Experiments and Fusion Science Research The development of the LDX superconductor is a good example of mutually beneficial efforts between fusion and high energy physics technology development. VLT Virtual Laboratory for Technology

24. 11/17/99 Plasma Materials Interaction Science Is Key to Plasma Performance. The DiMES probe in the DIII-D tokamak provides essential data on plasma material interactions. Key Scientific Issues: • Plasma erosion mechanisms • Hydrogen retention • Impurity generation and transport VLT Virtual Laboratory for Technology

25. 11/17/99 Plasma Disruptions are a key issue involving plasma, material and engineering science. • Main mass loss mechanisms: – Vaporization – Ablation - macroscopic particles (droplets) • Processes that decrease net mass loss of walls: Vapor Shield – Vapor cloud absorbs incoming energy flux W0 – Conversion to back radiation (secondary radiation) – Decrease heat load on surface to <10% W0 Droplet Shield – Due to ablation (splashing), the surface emits droplets; therefore, cloud of vapor and macroscopic particles exist nearby the exposed surface. – Droplets (macroscopic particles) absorb radiation power and decrease heat load onto surface. – Droplets vaporization path length depends on vapor dynamics in oblique magnetic field. VLT Virtual Laboratory for Technology

26. 11/17/99 ALPS - Advanced Limiter-divertor Plasma-facing Systems • Develop systems that can lead to enhanced power density, component lifetime, and power conversion efficiency, and may provide for plasma edge control and particle pumping. • Present effort is on plasma edge modeling, laboratory PMI studies of candidate liquids, and thermalhydraulics, including MHD effects. • Future effort is aimed at tests in plasma devices, e.g. DIII-D (DiMES) and, CDX-U, leading to a concept exploration test a large existing device. VLT Virtual Laboratory for Technology

27. 11/17/99 Liquid surfaces for limiters and divertors offer potentially significant advantages. A Science-Technology Partnership CLIPPER Project Facility: CDX-U Tokamak with UCSD local liquid lithium limiter L3 and PPPL toroidal liquid lithium belt limiter. center stack liquid lithium local rail limiter R = 0.34 m a = 0.22 m A = R/a > 1.5 k k < 2 Bt< 0.5 Tesla Ip< 150 kA Prf= 300 kW Plasma flat top 30 ms Extensive plasma diagnostics liquid lithium belt limiter VLT Virtual Laboratory for Technology

28. 11/17/99 APEX Exploring new concepts that substantially improve the vision for an attractive fusion energy system. • Inherent Low Activation • Reduce Waste • High Power Density • High Thermal Efficiency Related Applications Scientific Issues •Turbulent drag reduction •Crystal growth •Oceanography •Atmospheric processes •Liquid dispersion including droplet formation •Solidification •MHD propulsion •Casting •Liquid wall - plasma interaction •Free surface turbulence •Magnetohydrodynamic effects in liquid metal flows •Magnetohydrodynamic effects in low-conductivity fluid flows •Influence of a magnetic field on heat transfer •Influence of a magnetic field on heat transfer VLT Virtual Laboratory for Technology

29. 11/17/99 Utilizing a conducting liquid flowing in a strong magnetic field requires understanding of MHD phenomena and development of accurate MHD modeling techniques ? ? ? ? ? ? ? ? ? ? Liquid surface temperature and vaporization is a critical, tightly-coupled problem between plasma edge and liquid free surface conditions including: radiation spectrum and surface deformation, velocity, and turbulence characteristics Plasma stability and transport may be seriously affected – and potentially improved – through various mechanisms: control field penetration, H/He, pumping, passive stabilization, etc. Controlling the free surface flow configuration in complex geometries, including penetrations needed for plasma maintenance, is a challenging problem on the cutting edge of CFD VLT Virtual Laboratory for Technology

30. 11/17/99 SUMMARY • Scientific understanding and improved magnetic confinement and inertial driver concepts need improved technology. • Advanced design and analysis activities contribute to resolution of key scientific issues and provide continuing guidance to fusion science research. • Enabling Technology R&D also leads to improved understanding by advancing engineering and materials science and near-term benefits. • Essentially all aspects of Enabling Technology R&D are highly leveraged with well-established international collaborations. VLT Virtual Laboratory for Technology