Developing science

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Developing science technologies for Laser
Fusion EnergyJohn SethianPlasma Physics
Division, Naval Research Laboratory
8th International Conference on Tritium Science
and Technology September 16-21, 2007 Rochester,
New York
16th HAPL meeting Dec 4 5, 2006 Princeton
Plasma Physics Lab

• Universities
• UCSD
• Wisconsin
• Georgia Tech
• UCLA
• U Rochester, LLE
• UC Santa Barbara
• UC Berkeley
• UNC
• Penn State Electro-optics

• Government Labs
• NRL
• LLNL
• SNL
• LANL
• ORNL
• PPPL
• SRNL
• INEL

• Industry
• General Atomics
• L3/PSD
• Schafer Corp
• SAIC
• Commonwealth Tech
• Coherent
• Onyx
• DEI

• Voss Scientific
• Northrup
• Ultramet, Inc
• Plasma Processes, Inc
• PLEX Corporation
• FTF Corporation
• Research Scientific Inst
• Optiswitch Technology
• ESLI

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We have chosen to develop fusion energy based on
lasers, direct drive targets, and solid wall
chambers
Spherical pellet
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Why choose IFE, with lasers, direct drive
targets, and solid wall chambers
Why IFE? Separable components Why Laser
Fusion? Large physics data base from ICF
program Laser is MODULAR.. build one, you've
built them all Why Direct Drive? Simplest
target physics Simplest target
fabrication Why Solid Wall? Can be developed
subscale Comparatively easy to
change Disclaimer We are always open to
other ideas (e.g. liquid walls, Fast
Ignition). If someone develops them, we will be
happy to steal them
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2D simulations predict target gains gt 160.Need
gt 100 for a power plant
High-resolution 2D simulations with realistic
(NIF-spec) outer surface perturbations
Laser 2.4 MJ
Sector of Spherical Target
Similar predictions made byUniversity of
Rochester and LLNL
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NRL target physics models have been benchmarked
with experiments on Nike Laser
Mass variation (mg/cm3)
NRL FAST 2D Code
time (ns)
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We shamelessly leverage off other programs
ICF Program
Nike -- NRL
NIF -- LLNL
Omega-- Rochester
MFE Program
Tritium Systems (PPPL, SRNL, LANL)
Fusion Materials (ORNL)
Blankets / Neutronics (UCSD / Wisconsin)
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We take an "integrated system" approach Much
harder, but much more likely to yield something
that works!
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We encourage competition. It leads to innovation
and a better product. And leads to it faster
The HAPL Program is developing two types of
lasers, KrF and DPPSL
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Both HAPL Lasers have demonstrated high energy,
rep rate, long duration, operation.
Mercury DPPSL Laser (LLNL)
Electra KrF Laser (NRL)
300-700 J _at_ 248 nm 120 nsec pulse 1 - 5 Hz 25 k
shots continuous at 2.5 Hz Predict 7 efficiency
55 J _at_ 1051 nm 15 nsec pulse 10 Hz 100 k shots
continuous _at_ 10 Hz Recently demo 73 conversion
at 2?
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The Electra KrF Laser 700 Joules, 5 Hz
Recirculator
Pulsed Power
Cathode Hibachi (inside)
Laser Cell
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KrF Laser Achievements
Uniformity minimizes hydrodynamic
instabilities Single shot lt 0.2
non-uniformity ? Rep Rate lt 5.8 XDL
(provisional) Wavelength 248 nm (shortest
of any ICF laser) Maximizes absorption rocket
efficiency Minimizes risk from Laser Plasma
Instabilities (LPI) Laser Energy Oscillator
mode 300- 700 J/pulse up to 5 Hz Laser system
Average gt 300 J _at_ 5 Hz for 10 shots
Efficiency Predict gt 7 wall plug based on
Electra Research Durability 25,000 shots, 80 J
_at_ 2.5 Hz continuous 16,000 shots, 300 J _at_ 2.5
Hz (one pause) 7,000 shots, 300 J _at_ 5 Hz in 3
bursts Still need to demonstrate longevity
300 J _at_ 2.5 Hz 9,000 shots
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Summary of progress Final Optics? Developed
Grazing Incidence Metal Mirror meets laser damage
specs based on 1 M Shots? Designed final
optics train to meet neutronics requirements
3-D calculation of neutron flux

• Still need to
• Verify to gt 300 M shots
• Demo with larger areas
• Evaluate alternatives
• Dielectric, Fresnel lens

UCSD, PLEX LLC, Wisconsin, Penn State E-O
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Target fabrication ? Foam shells that
meet specs ? Produced gas tight overcoats
? Demonstrated smooth Au-Pd layer ?
Estimate Cost lt 0.16 each
100 mg/cc foam shell
22 shells/min, lt 1 variation
x-ray picture
"wet" shells
Schaffer
GA

• Still need to
• Thinner overcoat
• Smooth DT Ice layer by mass production

GA, UCSD
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Summary of progressTarget engagement ? We have
a concept to "engage" the target. ? Key
principles demonstrated in bench tests
Coincidence sensors
Target Glint source
Focusing mirrors
Vacuum window
Dichroic mirror
Amplifier / multiplexer/ fast steering mirrors
Target
Drive Laser Source
Alignment Laser
Cats eye retroreflector
Mirror steering test Need 20 um, achieved 150 um
_at_ 20
Target Injector
Grazing incidence mirror
Wedged dichroic mirror
General Atomics UCSD Penn State E-O A.E.
Robson NRL

• Still need to
• Meet all specs, all the time
• Integrated bench test

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Summary of progress -- Chamber First
Wall Bonding first wall to substrate Identified
thermo-mechanical fatigue limit Allows target
injection, laser propagation
Helium Retention
Thermo-mechanical
IEC (Wisconsin)
Laser Dragonfire (UCSD)
Ions RHEPP (SNL)
Armor/substrate interface stress
Van de Graff (UNC)

• Still need to
• helium retention
• carbon retention

Plasma Arc Lamp (ORNL)
UCLA, ORNL, NRL, Wisconsin, UNC, SNL, UCSD,
LLNL, PPPL, SRNL, Ultramet, PPI, etc
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"Magnetic Intervention" offers a way to keep the
ions off the wall

• Cusp Field (1 T 10 kG) imposed on chamber
• Ions radially push field until stopped by
  magnetic pressure
• Ions, at reduced energy and power, escape cusp
  and are absorbed in dumps
• Basic physics demonstrated in 1979 NRL
  experiment
• Allows SiC (higher temperature) wall and blanket

NRL, PPPL, UCSD, Wisconsin, Voss
R. E. Pechacek, et al., Phys. Rev. Lett. 45, 256
(1980).
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One Blanket concept we are evaluatingSelf
cooled Pb-17Li, SiCf/SiC with a Brayton Cycle
Efficiency gt 50
blankets
TBR gt 1.2
first wall
UCSD, Wisconsin, PPPL, NRL
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TRITIUM HANDLING We have a conceptual design for
as system to recover, process, refine and supply
Tritium
Charles Gentile, next talk!!!
PPPL, SRNL, LANL
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Preliminary studies show Laser Fusion may also
efficiently generate hydrogen
Hybrid Sulfur Cycle Input H2O heat
electricity Output H2 O2
799 ?C
H2O, SO2, O2
769 ?C
H2SO4 decomposer
HX
H2SO4
H2O
H2O, SO2
IFE Chamber
SO2 Depolarized Electrolyzer
O2
SO2/O2 separator
483 ?C
H2
Assumes 1) 48 Brayton electric conversion 2)
HHV (fuel value going into fuel cell)
SRNL
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The Fusion Test Facility(FTF)
Need to lower the cost of development The key
lower laser energy needed for significant gain
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Basis for higher performance?Shorter wavelength
KrF more resistant to Laser Plasma Instability
(LPI).?Allows higher implosion velocity of low
aspect ratio targets?Leads to higher gain
Maximum I?2 limited by Laser Plasma Instability
(LPI) Pressure scales approximately as
I7/9?-2/9 ? PMAX scales as ?-16/9 Factor of
(351/248)-16/9 1.85 advantage for KrFs deeper
UV over frequency-tripled Nd-glass
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2 D Simulations of new designspredict 27 MJ
(Gain 56) for 480 kJ Laser
Fusion Energy Plant Gain 160 _at_ 2.4 MJ (KrF)
22.4 ns
Shock Ignition Targets R Betti, (LLE) Show
potentially higher performance
NRL
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Initial Nike Experiments show no evidence for
Laser Plasma Instability _at_ 2-3x1015 W/cm2
12 overlapped 300 ps Nike backlighter beams
0.1 mm focal diameter

• So far no hard x-rays, no Raman scatter, no 3/2
  omega

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The Fusion Test Facility (FTF)
Laser energy ? 500 kJ Rep-Rate ? 5
Hz Fusion power ? 100-150 MW
28 kJ KrF laser Amp 1 of 22, (2 spares)
Reaction Chamber
Laser Beam Ducts
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Objectives of the FTF
Develop key components, demonstrate they work
together with the required precision and
durability Platform to evaluate and optimize
pellet physics Develop materials and full scale
chamber/blanket components for a fusion power
plant. Provide operational experience and
develop techniques for power plants.
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The VisionA plentiful, safe, clean energy source
A 100 ton (4200 Cu ft) COAL hopper runs a 1 GWe
Power Plant for 10 min
Same hopper filled with IFE targets runs a 1 GWe
Power Plant for 7 years