Overview of Inertial Fusion EnergyTechnology Activities at UC San Diego
Mark S. Tillack
Briefing to the Advanced Energy Technology GroupJune 2001
IFE Technology Program Relationships
National CollaborationsARIES TeamIFE Technology:
Target Engineering (GA) Chamber Materials (SNLA Team) Chamber Physics (ANL/INEEL) Final Optics (UCLA/LANL/LLNL/GA)
International Collaborations
Local OrganizationJSOE: MAE and ECE Departments
Center for Energy ResearchPlasma Experimental ProgramsPlasma Theory and ComputationVirtual Laboratory for TechnologyAdvanced Energy Technology:
1. Fusion Design Studies2. IFE Technology3. Thermal Sciences
Collaborations
DOE Office of Fusion Energy SciencesScience DivisionTechnology Division (VLT, Baker)
Design Studies: ARIES (Dove, Najmabadi)IFE Technology (Nardella, Meier)
DOE Defense ProgramsHigh Avg. Power Laser Program (Schneider)
Naval Research Laboratory (Sethian)Lawrence Livermore National Lab (Payne)
CA State ProgramsCalifornia Energy CommissionUC Energy InstituteNational Laboratory collaborative programs
Industry ProgramsSBIR contracts (PPI)GA contracts (Goodin)
Funding and Oversight
History of the IFE Technology Program
Sept. 1996 Initial contact with LLNL
June 1997-99 Funded studies of chamber simulation experiments
July 1999 OFES 3-year grant initiatedLab space obtained (3703 EBU-I), laser ordered
December 1999 Delivery of 2J Nd:YAG laser
April 2000 Initial experiments performed;Collaboration with GA on optics fab. & characterization started
June 2000 ARIES IFE study kick-off
July 2000 First new researcher hired into the IFE technology program
April 2001 DP grants awarded, chamber physics & materials programs initiated
June-July 2001 Arrival of 5 new staffGA collaboration initiated on target engineering
IFE Technology Program Organization, June 2001
Driver interface
Chamber physics
IFEengineering
IFE power plantstudies
Collaboration w/ General Atomics
J. Pulsifer(thermal analysis)
E. Abu-Nada(integratedmodeling)
F. Najmabadi
Final OpticsBeamPropagation
Experiments
M. Tillack
M. Tillack F. Najmabadi
R. Raffray
Z. Dragojlovic(integrated modeling)
Collaboration w/ ANL, INEEL
A. Gaeris
S. S. Harilal
B. Harilal
M. Zaghloul(materialsresponse)
R. Miller
E. Abu-Nada
System ModelChamber Eng.
R. Raffray
T. K. Mau(modeling)
M. Zaghloul(testing)
Integration
M. Tillack
M. Zaghloul
X. Wang
Final optics
T. K. Mau
J. Pulsifer
M. Tillack
S. S. Harilal(spectroscopy)
J. Pulsifer(vac. eng.)
A. Gaeris(smoothing)
F. Najmabadi
Numericalmodeling
Engineeringresponses
F. Najmabadi
Targetengineering
R. Raffray
Chamber wallengineering
Collaboration w/ Sandia Albuquerque
T. K. Mau(radiation)
M. Tillack
D. Blair
M. Tillack R. Raffray
M. Zaghloul
X. Wang
M. Tillack
Collaboration w/ UCLA, LANL,
LLNL, GA
Prometheus-L Reactor Building Layout
Driver Interface R&D: Final Optics(Tillack, Zaghloul, Mau)
Problem StatementThe final beam steering optic in a laser-IFE power plant is subjected to a variety of
threats, including neutrons, γ-rays, x-rays, high-energy ions, chamber contaminants and thelaser itself. Robust optics that can survive for extended periods of time (108 shots) withoutdegrading the laser beam quality are needed.
Objectives • Measure laser-induced damage threshold and demonstrate stable long-term operation
of a grazing incidence metal mirror at laser fluence of ~5 J/cm2 normal to the beam. • Determine limits on damage due to contamination and other target threats.
Key Program Elements• Fabrication and characterization of mirrors (including subcontract with GA)• Testing in the UCSD Laser Plasma and Laser-Material Interactions Laboratory• Modeling of the effects of damage on beam characteristics• Neutron irradiation testing in collaboration with LANL and LLNL• Target injection system integration in collaboration with General Atomics
Status and Opportunities • Initial LIDT data have been obtained • Models of Fresnel and Kirchhoff scattering have been developed • New research opportunities exist in several terrestrial, airborne and space applications
• Damage occurs at a higher fluence as compared with normal incidence
• Silicide occlusions in Al 6061 preferentially absorb light, causingexplosive ejection and melting
• Fe impurities appear unaffected
• Exposure of Al 1100 to 1000 shots at 85˚ exhibited no damage
Several shots in Al 6061 at 80˚, 1 J/cm2 peak
Damage to aluminum at grazing angles
Fe
Fe MgSi
1000x
Al GIMM with in-situ reflectometry
Driver Interface R&D: Beam Propagation (Najmabadi, Harilal, Gaeris, Pulsifer, Tillack)
Problem StatementThe chamber environment following a target explosion contains a hot, turbulent gas
which will interact with subsequent laser pulses. Gas breakdown occurs in the vicinity ofthe target where the beam is focussed. A better understanding of the degree of gasionization and the effects on beam propagation are needed. The effect of aerosol andparticulate in the chamber must be understood in order to establish clearing criteria.
Objectives• Determine the laser breakdown threshold in pure and impure chamber environments at
low pressure.• Determine the effect of chamber environmental conditions on beam propagation.
Key Program Elements• Construction of a multi-purpose vacuum chamber• Breakdown emission detection and spectroscopy• Laser beam smoothing and accurate profiling (goal of 2-5%)
Status and Opportunities• Chamber and vacuum system parts have been ordered• Interaction of laser with chamber media is related to laser interactions with ablation
plumes and atmospheric beam transport (LIDAR, free-space optical communications, ...)
Beam propagation experiments will be performed in amulti-purpose vacuum chamber under construction
1E+09
1E+10
1E+11
1E+12
1E+13
Bre
akdo
wn
Thr
esho
ld, W
/cm
2
1 10 100 1000 10000
Pressure (Torr)
Rosen 1987 (1/3 um, 15 ns)
Murray 1977 (1/4 um, 20 ns)
Turcu 1997 (1/4 um, 18 ns, Kr)
Alcock 1972 (1/3 um, 8 ns)
Buscher PRL 1965 (1/3 um, 20 ns)
Gower 1981 (1/4 um, 10 ns)Sombrero
Initial measurements:• Visible light emission from the focal spot
• Variation in laser energy profile (CCD) & temporal pulse shape (photodiodes) • Wavefront variation (Shack-Hartmann)Planned: • Emission spectroscopy
• Changes in spatial profile with 2% accuracy
Chamber Physics: Numerical Modeling (Dragojlovic, Najmabadi, Raffray)
Problem StatementThe chamber condition following a target explosion in a realistic chamber geometry is not well
understood. The key uncertainty is whether or not the chamber environment will return to asufficiently quiescent and clean low-pressure state to allow another shot to be initiated within100–200 ms. A modeling capability is needed to predict the behaviour of an IFE power plantchamber, to ensure that all relevant phenomena are taken into account and to help plan experiments.
Objectives• Develop an integrated, state-of-the-art computational model of the dynamic response of IFE
chambers following target explosions and make it available to the community• Benchmark the code• Use the code to plan experiments and study IFE chambers
Key Program Elements• Construction of the initial, extensible numerical framework with core fluid dynamics model• Inclusion of wall interactions and radiation transport modules in collaboration with ANL• Inclusion of aerosol & particulate production and transport models in collaboration with INEEL• Implementation of adaptive mesh routines, if necessary
Status• Code methodology is currently under development• Initial code writing to begin in summer 2001
Multi-physics model of chamber dynamics
ChamberTarget Wall
Momentum Conservation
Impulse
Energy ConservationPhasechange
Conduction
ImpulsePressure (T)
Pressure(density)
Mass Conservation(multi-phase, multi-species)
Evaporation,sputtering ...
CondensationEvacuation
Energy deposition
Heattransfer Thermal stress
Driver Beams
Energy Input
Momentum Input
Mass Input
Fluidhydrodynamics
Erosion/redeposition
Viscous dissipation
Transport & deposition
Radiation transport
Phase change
Mechanicalresponse
Convection
Eqns. of state
Thermalresponse
Chamber Physics: Engineering Responses (Raffray, Zaghloul, others TBD)
Problem StatementMany physical phenomena with different time scales occur in the chamber following a target
explosion. The aim of research on engineering responses is to improve our predictive capabilities ofthe chamber dynamics and to understand the constraints imposed on the rep-rate of an IFE powerplant.
Objectives• Explore chamber dynamic phenomena to understand most critical issues for select IFE chambers• Develop and benchmark physics modules for the integrated modeling effort
Key Program Elements• Develop improved “wall-interaction” models• Develop aerosol and particulate production and transport models• Develop a detailed radiation transport package• Quantify R&D needs and define experiments• Benchmark models using experimental data
Status and Opportunities• Literature survey and scoping of individual response models has begun• Implementation will be coupled with numerical model development activity
• Close ties with experimental programs should be maintained
Aerosol and droplet production is a keyissue for wetted wall IFE chambers
liquid
vapor
X-ray, gamma & neutron preheating phase:
Ion heating phase: background 2-phase
Possible mechanisms for droplet production:surface vapor explosionbulk boilingisochoric heatingconvective flow & shocksin-flight recondensation
Transport phase: radiation
convection
Chamber Physics: Experiments (Harilal, Harilal, Gaeris, Blair, Tillack, Najmabadi)
Problem StatementThe chamber condition following a target explosion in a realistic chamber geometry is not well
understood. A key uncertainty is whether or not the chamber environment will return to asufficiently quiescent and clean low-pressure state to allow a second shot to be initiated within100–200 ms. A capability is needed to predict the behavior of IFE power plant chambers, to ensurethat all relevant phenomena are taken into account and to help benchmark numerical models.
Objectives • Demonstrate validity of scaling and simulation experiments • Develop chamber experimental capabilities • Benchmark chamber dynamics models • Provide new data relevant to IFE chamber responses
Key Program Elements• Study potential energy sources and simulation capabilities• Build or obtain access to needed energy sources• Define and, when needed, develop diagnostics• Perform simulation experiments
Status and Opportunities• Initial characterization of simulation experiment opportunities have been performed• Synergism between IFE and laser ablation
Chamber Physics: Experiments
HYADES simulation of laser irradiation of Au
Direct surface illumination
x-ray source w/close-in targets
Shaped chambers
Micro-enclosureBeamline effects
IFE Engineering: Target Engineering (Tillack, Raffray, Pulsifer, Abu-Nada)
Problem StatementCryogenic targets require strict control over symmetry in order to assure that fusion will take
place. Thermal and mechanical responses of direct and indirect drive targets during fabrication(layering), injection and transport through the chamber environment are important factors indetermining the survival of the delicate targets. An integrated thermal, fluid, mechanical andoptical model is needed to guide R&D programs and to predict the behavior of IFE targets in powerplant chambers.
Objectives• Develop an integrated, state-of-the-art computational model of the response of IFE targets
during fabrication, injection and transport through the chamber• Use the code to plan experiments and study IFE targets
Key Program Elements• Construction of the initial, extensible numerical framework• Inclusion of various interaction modules in collaboration with General Atomics
Status and Opportunities• Code methodology is currently under development• Initial code writing to begin in Summer/Fall 2001
Integrated Engineering Model of IFE Targets
Input ParametersInitial target configurationProperties databaseImposed accelerationsThermal environmentChamber gas, aerosol and particulate speciesChamber hydrodynamic environment
Computed ParametersTarget temperature distributionTarget trajectoryTarget internal stress distributionInternal mass transport
Layering Injection Chamber TransportFree Flight
Thermal radiation
Hydrodynamicinteractions
Convective heat transfer
Acceleration in sabot
Gravity
Mass transferTransient stresses
IFE Engineering: Wall Engineering (Raffray, Zaghloul, Wang, Tillack)
Problem StatementThe walls of an IFE chamber are subjected to intense energy sources from repeated target
explosions. Survival and reliability of materials in this environment are important for thefeasibility of dry wall chamber concepts.
Objectives• Develop innovative design solutions for robust, damage-resistant wall materials• Evaluate response of materials to simulated IFE target explosions
• Assist SNLA, ESLI and others field experiments and perform pre- and post-test analysis
Key Program Elements• Modeling of energy deposition and thermal response of engineering surfaces• Experimentation at the SNLA Z x-ray source and RHEPP/MAP ion beam facility• Diagnostic development
Status and Opportunities • This program is carried out in collaboration with Sandia National Laboratories, and
includes participation of the University of Wisconsin, UC Berkeley, and Energy ScienceLaboratories Inc.
IFE Engineering: Wall Engineering
RHEPP/MAP ion beam facility, SNLA
ESLI carbon fiber flocked surface
Structured surfaces may offer superiorthermal response and improved erosionbehavior under exposure to pulsed energysources
Related Studies: Laser Micromaching** work partially supported by Hewlett Packard
• Laser absorption in surface
• Thermal response of surface
• Liquid hydrodynamics
• Evaporation
• Unsteady gas dynamics
(including chamber environment)
• Condensation
• Laser-cluster interaction
Governing physics is very similar to IFE
Closing Remarks
• The UCSD IFE Technology Program has grown from a simple idea to adiversified program of 12 researchers in less than 5 years.
• We are now poised to make our most rapid progress ever, developingmodels and experimental capabilities and helping to demonstrate thefeasibility of inertial fusion energy.
• Numerous opportunities exist for expanding into new areas of study.