Overview of Inertial Fusion Energy Technology Activities at UC San Diego Mark S. Tillack Briefing to the Advanced Energy Technology Group June 2001

IFE Technology Program Relationships National Collaborations ARIES Team IFE Technology: Target Engineering (GA) Chamber Materials (SNLA Team) Chamber Physics (ANL/INEEL) Final Optics (UCLA/LANL/LLNL/GA) International Collaborations Local Organization JSOE: MAE and ECE Departments Center for Energy Research Plasma Experimental Programs Plasma Theory and Computation Virtual Laboratory for Technology Advanced Energy Technology: 1. Fusion Design Studies 2. IFE Technology 3. Thermal Sciences Collaborations DOE Office of Fusion Energy Sciences Science Division Technology Division (VLT, Baker) Design Studies: ARIES (Dove, Najmabadi) IFE Technology (Nardella, Meier) DOE Defense Programs High Avg. Power Laser Program (Schneider) Naval Research Laboratory (Sethian) Lawrence Livermore National Lab (Payne) CA State Programs California Energy Commission UC Energy Institute National Laboratory collaborative programs Industry Programs SBIR contracts (PPI) GA contracts (Goodin) Funding and Oversight

History of the IFE Technology Program Sept. 1996Initial contact with LLNL June Funded studies of chamber simulation experiments July 1999OFES 3-year grant initiated Lab space obtained (3703 EBU-I), laser ordered December 1999Delivery of 2J Nd:YAG laser April 2000Initial experiments performed; Collaboration with GA on optics fab. & characterization started June 2000ARIES IFE study kick-off July 2000First new researcher hired into the IFE technology program April 2001DP grants awarded, chamber physics & materials programs initiated June-July 2001Arrival of 5 new staff GA collaboration initiated on target engineering

IFE Technology Program Organization, June 2001

Prometheus-L Reactor Building Layout

Driver Interface R&D: Final Optics (Tillack, Zaghloul, Mau) Problem Statement The final beam steering optic in a laser-IFE power plant is subjected to a variety of threats, including neutrons,  -rays, x-rays, high-energy ions, chamber contaminants and the laser itself. Robust optics that can survive for extended periods of time (10 8 shots) without degrading 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/cm 2 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, causing explosive 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/cm 2 peak Damage to aluminum at grazing angles Fe MgSi 1000x Al GIMM with in-situ reflectometry

Driver Interface R&D: Beam Propagation (Najmabadi, Harilal, Gaeris, Pulsifer, Tillack) Problem Statement The chamber environment following a target explosion contains a hot, turbulent gas which will interact with subsequent laser pulses. Gas breakdown occurs in the vicinity of the target where the beam is focussed. A better understanding of the degree of gas ionization and the effects on beam propagation are needed. The effect of aerosol and particulate 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 a multi-purpose vacuum chamber under construction 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 Statement The 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 a sufficiently quiescent and clean low-pressure state to allow another shot to be initiated within 100– 200 ms. A modeling capability is needed to predict the behaviour of an IFE power plant chamber, 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

Chamber Physics: Engineering Responses (Raffray, Zaghloul, others TBD) Problem Statement Many 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 of the chamber dynamics and to understand the constraints imposed on the rep-rate of an IFE power plant. 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 key issue for wetted wall IFE chambers

Chamber Physics: Experiments (Harilal, Harilal, Gaeris, Blair, Tillack, Najmabadi) Problem Statement The 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 a sufficiently quiescent and clean low-pressure state to allow a second shot to be initiated within 100– 200 ms. A capability is needed to predict the behavior of IFE power plant chambers, to ensure that 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

IFE Engineering: Target Engineering (Tillack, Raffray, Pulsifer, Abu-Nada) Problem Statement Cryogenic 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 in determining the survival of the delicate targets. An integrated thermal, fluid, mechanical and optical model is needed to guide R&D programs and to predict the behavior of IFE targets in power plant 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 Parameters Initial target configuration Properties database Imposed accelerations Thermal environment Chamber gas, aerosol and particulate species Chamber hydrodynamic environment Computed Parameters Target temperature distribution Target trajectory Target internal stress distribution Internal mass transport

IFE Engineering: Wall Engineering (Raffray, Zaghloul, Wang, Tillack) Problem Statement The 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 the feasibility 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 Science Laboratories Inc.

IFE Engineering: Wall Engineering RHEPP/MAP ion beam facility, SNLA ESLI carbon fiber flocked surface Structured surfaces may offer superior thermal response and improved erosion behavior under exposure to pulsed energy sources

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 a diversified program of 12 researchers in less than 5 years. We are now poised to make our most rapid progress ever, developing models and experimental capabilities and helping to demonstrate the feasibility of inertial fusion energy. Numerous opportunities exist for expanding into new areas of study.