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. Sethian Naval Research Laboratory
20th IEEE/NPSS Symposium on Fusion Engineering14-17 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
Targetfactory
Modular LaserArray
Final optics
The Path to Develop Laser Fusion Energy
Phase IIValidatescience &technology2006 - 2014
Phase IIIEngineeringTest Facilityoperating 2020
Full size laser: 2.4 MJ, 60 laser lines Optimize targets for high yield Develop materials and components. 300-700 MW net electricity Resolve basic issues by 2028
Phase I:Basic fusionscience &technology1999- 2005
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
LinescanCamera
Targetfab labs
Cryogenic targetsupply systems
Differentialvacuum pumping
Sabotdeflector
Surrogatetargetchamber
In-chambertracking
Low powerhit on fly laser
Positiondetectors
Gun barrelLoadingchamber
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 Material CH (DVB) foam
Capsule Diameter ~4 mm
Capsule Wall Thickness 290 m
Foam shell density 100-120 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~15-18.5 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 Vapor0.3 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
Step Methods Comments/Remaining Issue
Capsule Production Microencapsulation Suitable for mass-productionIssue = non-concentricity
Metal Overcoat Sputter Coating Standard industrial processOptimization needed
Filling with DT Permeation Optimize for min. DT inventory
Layering -layering, IR enhance Mass-production demo in TFIF
Cryo Handling Cryostats Critical part of TFIF
Injection Gas-gun, EM Analyses of survival now - demo in TFIF
InjectorLayering DemoLab-scale microencapsulation
2. Cryogenic target handling will be addressed in the TFIF
HELIUM/DTSEPARATION
DTPRESSURIZATIONSYSTEM
TO INJECTOR
REVOLVER
DIFFUSER
IR ORµWAVEINJECTION
COOLER
He
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 rate 6 HzFree flight distance up to 16 mPlacement accuracy ±5 mmTrajectory prediction at DCC ±14 micron
Acceleration ~10,000 m/s2 (limited for target survival)Wall temperature up to 1800 KChamber gas temperature up 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-chamber In-chamber
DetectorD2
DetectorDCC
DetectorD1
OPTIONS:
• Add more detectors
• Add interferometeric position change
detectors• Being developed by
POC under an SBIR.
DetectorDCC
DetectorD2
DetectorD1
InterferometricallyGenerated light sheets
PhotodetecterQuartz 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:To=18 K, Tmax=19.79 K
15 ms transit time (400 m/s)
1000 K wall
gas at 10 mTorr, 4000 K, Zeff=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 accuracy @20-30 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
trackingelectronics
target tracking
injector
timing
laser driver
trigger
steering control
targetchamber
VxVyVz
Target tracking/beam steeringinterface
xyzt
pointing laser
PSDxyzt
20-30 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
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