A Target Fabrication and Injection Facility for Laser-IFE M. S. Tillack, A. R. Raffray, UC San Diego D. T. Goodin, N. B. Alexander, R. W. Petzoldt, General Atomics D. Schroen and J. E. Streit,Schafer Corporation J. D. SethianNaval Research Laboratory 20th IEEE/NPSS Symposium on Fusion Engineering October 2003 San Diego, CA

Laser-IFE with direct drive targets and dry chambers is under development in the High Average Power Laser Program Modular, separable parts allows for lower development costs and economical upgrades Spherical target Electricity Generator Dry wall (passive) chamber Target factory Modular Laser Array Final optics

The Path to Develop Laser Fusion Energy Phase II Validate science & technology Phase III Engineering Test Facility operating  2020  Full size laser: 2.4 MJ, 60 laser lines  Optimize targets for high yield  Develop materials and components.   MW net electricity  Resolve basic issues by 2028 Phase I: Basic fusion science & technology Ignition Physics Validation MJ target implosions Calibrated 3D simulations Target Design & Physics 2D/3D simulations 1-30 kJ laser-target expts Full Scale Components Power plant laser beamline Target fab/injection facility Power plant design Scalable Technologies Krypton fluoride laser Diode pumped solid state laser Target fabrication & injection Final optics Chambers materials/design

Phase-I R&D includes a room-temperature capsule injector and various separate-effects R&D tasks to demonstrate target fabrication and survival Elements of the injector facility: Plastic capsules injected with sabots Target tracking and verification Target transport through a surrogate cylindrical chamber Related R&D: Target fabrication steps DT properties Chamber interactions Beam steering D1 Detector Station Photodiode Triggers Linescan Camera

The TFIF – Target Fabrication and Injection Facility – will validate the science and technology of full-scale components of an IFE power plant in an integrated system Elements of the facility: 1. Mass production (batch mode) of cryogenic targets that meet the specifications of high gain 2. Target handling & transfer 3. Cryogenic target injection into the chamber 4. In-chamber target tracking 5. Chamber environment (backround gas, wall temperature, etc.) 6. Steering of a pulsed laser onto the target in flight Key Features: Full cryogenic capabilities Interfaces and integration Repeatable and reliable

Expected Direct Drive Target Specifications Capsule MaterialCH (DVB) foam Capsule Diameter~4 mm Capsule Wall Thickness290  m Foam shell density mg/cc Out of Round<1% of radius Non-Concentricity<1% of wall thickness Shell Surface Finish~20 nm RMS Ice Surface Finish<1  m RMS Temperature at shot~ K Positioning in chamber ± 5 mm Alignment with beams<20  m Reference target design and specifications NRL High Gain Target Design Laser driven foam shell is CH-only Divinyl benzene is being developed. Outer foam insulation is also possible. DT Vapor 0.3 mg/cc DT Fuel CH Foam + DT 1  m CH +500 Å Pd/Au 1.95 mm 1.50 mm 1.69 mm CH foam  = 20 mg/cc

1. Manufacturing and characterization steps will be demonstrated with processes scalable to mass production StepMethodsComments/Remaining Issue Capsule ProductionMicroencapsulationSuitable for mass-production Issue = non-concentricity Metal OvercoatSputter CoatingStandard industrial process Optimization needed Filling with DTPermeationOptimize for min. DT inventory Layering  -layering, IR enhanceMass-production demo in TFIF Cryo HandlingCryostatsCritical part of TFIF InjectionGas-gun, EMAnalyses of survival now - demo in TFIF Injector Layering Demo Lab-scale microencapsulation

2. Cryogenic target handling will be addressed in the TFIF Issues Static “cling” Self charging Cryo-layer degradation Physical damage Component wear in vacuum

3. The target injector will develop and demonstrate cryogenic target survival during accurate, high speed injection Target speed up to 400 m/s (to reduce heating time in chamber) Repetition rate6 Hz Free flight distanceup to 16 m Placement accuracy±5 mm Trajectory prediction at DCC±14 micron Acceleration~10,000 m/s 2 (limited for target survival) Wall temperatureup to 1800 K Chamber gas temperatureup to 5000 K Current target protection sabot design Sabot (fully engaged) Sabot (disengaged)

A gas gun or EM accelerator may be used The gas gun is a more developed and simpler technology An EM accelerator eliminates propellant gas and is more compatible with cryogenic targets

End of Gun Barrel 4. In-chamber tracking will be added to deal with non-uniform gas density, turbulence, and “wind” Ex-chamberIn-chamber Detector D2 Detector DCC Detector D1 OPTIONS: Add more detectors Add interferometeric position change detectors Being developed by POC under an SBIR. Detector DCC Detector D2 Detector D1 Interferometrically Generated light sheets Photodetecter Quartz Tube Reflections of light sheets from target picked up by photodetector. Use 3 orthogonal sets of light sheet sources and detectors, each in a different color.

5. Target survival in the chamber is a critical issue to be addressed in TFIF TFIF will help demonstrate acceptable symmetry in simulated chambers In-chamber diagnosis (e.g., shadowgraphy) is very limited; complementary R&D is essential Radiation heating from hot chamber walls Friction and condensation from chamber gas Residual plasma recombination Baseline target/chamber conditions: T o =18 K, T max =19.79 K 15 ms transit time (400 m/s) 1000 K wall gas at 10 mTorr, 4000 K, Z eff =0

6. Laser driver integration requires precise metrology and timing, as well as rapid control signal transfer Goals: ±5 mm location, 20  m target/laser m (~1  radian mirror aiming precision  0.4  m mirror displacement) Continuous corrections based on tracking info In-chamber tracking Final correction at 11  s, or ~4 mm from implosion location xyzt tracking electronics target tracking injector timing laser driver trigger steering control target chamber VxVyVzVxVyVz Target tracking/ beam steering interface xyzt pointing laser PSD xyzt m confocal tracking

Summary An integrated Target Fabrication and Injection Facility is an essential element of the plan to develop IFE based on lasers and direct drive targets The facility will integrate all of the systems and interfaces relevant to IFE power plant fuelling: –Mass production of cryogenic targets –Target handling & transfer –Target injection –Target tracking –Target survival –Integration with the final optic Independent R&D is well underway, and is expected to provide the necessary data to proceed with TFIF in a time frame consistent with the transition to Phase II