John Sethian & Stephen Obenschain Plasma Physics Division Naval Research Laboratory

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Fusion energy: How to realize it sooner and with

less risk.featuring as a case study:

The Laser Fusion Test Facility (FTF)

John Sethian & Stephen ObenschainPlasma Physics Division

Naval Research LaboratoryWashington, DC 20375

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How should nuclear fusion fit in to the"nuclear renaissance?"

R&D Synergy

An opportunity to develop fusion on a much faster than “traditional” timescale

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If nuclear fission is in it's Renaissance,

Then its time to get fusion out of the Dark Ages

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A prescription to realize a practical fusion energy source within the next few decades

1) Fusion energy is a worthy goal---Don’t get distracted

2) Encourage competition & innovation.

3) Pick approaches (fusion concepts) that: a) Value simplicity b) Lead to an attractive power plant

(technically, economically, environmentally…) c) Require less investment to develop

4) Develop science & technology as an integrated system

5) Staged program with well defined “go / no-go” points Elements developed and incorporated into progressively

more capable facilities

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World Marketed Energy Consumption, 1980-2030Quadrillion BTU

An energy source that features

• plentiful fuel, with no geopolitical boundaries

• minimal proliferation issues (if any)

• no greenhouse gasses

• tractable waste disposal

Would be of great economic, social, and political benefit!

1) Fusion energy is a worthy goal

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Fusion is important and valuable enough to stand on its own right

usually the first approach defines the technology ................for better or worse

fusion has lots of advantages, let's not nullify them with distractions

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2) "Competition improves the breed*"

* F.L. Porsche

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Electricityor Hydrogen Generator

Reaction chamber

Spherical pellet

Pelletfactory

Arrayof

Lasers

Final optics

3) We believe direct drive with lasers can lead to an attractive power plant

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Why we believe direct drive with lasers can lead to an attractive power plant

Target physics underpinnings developed under ICF program:(Omega, Z, Nike, and NIF)

Only two main issues: Hydro stability & laser-target couplingCan calculate with bench marked codes

New class of target designs show way to lower demo cost

Laser (most costly component) is modularLowers development costs

Simple spherical targets:“fuel” made by mass production

Power plant studies shown concept economically attractive

Separated components provides economical upgrades

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Universities1. UCSD2. Wisconsin3. Georgia Tech4. UCLA5. U Rochester, LLE6. UC Santa Barbara7. UC Berkeley8. UNC9. Penn State Electro-optics

Government Labs1. NRL2. LLNL3. SNL4. LANL5. ORNL6. PPPL7. SRNL8. INEL

Industry

1. General Atomics2. L3/PSD3. Schafer Corp4. SAIC5. Commonwealth Tech6. Coherent7. Onyx8. DEI9. Voss Scientific

10. Northrup11. Ultramet, Inc12. Plasma Processes, Inc13. PLEX Corporation14. FTF Corporation15. Research Scientific

Inst16. Optiswitch Technology17. ESLI

15th HAPL meetingAug 8 & 9, 2006

General Atomics/UCSD(San Diego)

4) We are developing the Science & Technology for a laser fusion power plant as an integrated system. In other words: as if we plan to build one

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NRL 2D computer simulations predict targetgains > 160. Need > 100 for a power plant

Laser = 2.5 MJ 21.83 nsec

22.40 nsec

GAIN = 160 Similar predictions made by:University of RochesterLawrence Livermore National Laboratory

"Picket" Pulse Shape

0 10 20time (nsec)

Power(TW)

1000

100

10

1

t1

t2

t3

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The HAPL program is developing two lasers: Diode Pumped Solid State Laser (DPPSL) Electron beam pumped Krypton Fluoride Laser (KrF)

Electra KrF Laser (NRL) Mercury DPPSL Laser (LLNL)

300-700 J @ 248 nm120 nsec pulse1 - 5 Hz25 k shots continuous at 2.5 HzPredict 7% efficiency

55 J @ 1051 nm*15 nsec pulse10 Hz100 k shots continuous @ 10 Hz* Recently demo 73% conversion at 2

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Target fabrication progress Made foam capsules that meet all specifications Produced gas tight overcoats Demonstrated smooth Au-Pd layer

DT Vapor

DT Ice (fuel)

Foam/DT (ablator)

CH

334m

256m

5 m

DT Vapor

DT Ice (fuel)

Foam/DT (ablator)

CH

334m

256m

5 m

Sector ofSpherical

Target

4 mm

foam shells

Au/Pd coated shells

General AtomicsSchafferLANL

Au/Pd layer

CH+ Au/Pd layer

Foam

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We have a concept to "engage" the target.Key principles demonstrated in bench tests

("engage" tracking the target and steering the laser mirrors)

Target

Coincidence sensors

TargetInjector

TargetGlint

sourceDichroic mirror

Cat’s eyeretroreflector

Wedged dichroicmirror

Grazingincidencemirror

Vacuum window

Focusingmirrors

ASE Source

Alignment Laser

Amplifier / multiplexer/ fast steering mirrors

Mirror steering test

General AtomicsUCSDPenn StateA.E. Robson

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Experimental / computational tools to develop a chamber wall to resist the "threats" from the target

Thermo-mechanical(ions & x-rays)

Armor/substrate interface stress

Helium Retention

Modeling

IEC (Wisconsin)

Laser: Dragonfire

(UCSD)

X-rays:XAPPER(LLNL)

Plasma Arc Lamp(ORNL)

Van de Graff (UNC)

Ions:RHEPP(SNL)

HEROS Code(UCLA)

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200ns

300ns

100ns

400ns

500ns

526ns

200ns

300ns

100ns

400ns

500ns

526ns

"Magnetic Intervention" offers a way to keep the ions off the wall

1. Ions “radially push” field outward, stopped stopped by magnetic pressure

2. Compressed field is resistively dissipated in first wall and blanket

3. Ions, at reduced energy and power, escape from cusp and absorbed in dump

Coils (4 MA each ~ 1T)--form cusp magnetic field

Expansion of plasma in cusp field:2-D shell model

A.E. Robson

ToroidalDump

5.5 m~ 13.0 m

inn

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1979 NRL experiment showed principal of MI. Recent simulations predict plasma & ion motion

NRLVoss Scientific (D. Rose)A.E. Robson*R. E. Pechacek, et al., Phys. Rev. Lett. 45, 256 (1980).

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10

5

0

r (cm)

0 1 2 3 4 5t (sec)

NRL data

2D EMHDSimulation

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3) We can lower the cost to “develop the concept” (aka ready to build full size power plants)

James Watt’sSteam Engine

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The key to lowering development cost: New class of target designs that produce substantial gain with lower laser energy

NRL calculationsgain = 60 @ 460 kJ

LLNL calculationsgain = 51 @ 480 kJ

468 km/ sec

449

406

353

344 100

0

60

120

Gain

0.2 0.4 0.6 0 .8

Laser energy (MJ)

0

0 25 50 75 100 125 1501

10

10 2

10 3

Thanks to J. Perkins, LLNL

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Basis for higher performance:Shorter wavelength KrF laser drive more resistant to hydro instability.Allows higher implosion velocity of low aspect ratio targets.

Laser plasma instability limits peak I2

P scales approximately as I7/9-2/9

PMAX scales as -16/9

Factor of (351/248)-16/9 = 1.85 advantage forKrF’s deeper UV over frequency-tripled Nd-glass

Higher Gain: Higher implosion velocity Lower aspect ratio

Better stability Shorter wavelength of KrF:

No Yes

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The Fusion Test Facility (FTF)

Laser energy: 500 kJRep-Rate 5 HzFusion power: 100-150 MW

28 kJ KrF laser Amp1 of 22, (2 spares)

Laser Beam Ducts

ReactionChamber

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Objectives of the FTF

Develop the key components, and demonstrate they work together with the required precision, repetition rate, 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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Stage I 2008-2013

Target physics validation Calibrated 3D simulations Hydro and LPI experimentsNike enhanced performance, or NexStar, OMEGA, NIF, Z

Develop full-size components• 25 kJ 5 Hz laser beam line• (first step is 1 kJ laser beam line) • Target fabrication /injection • Power plant & FTF design

Stage II2014-2022

operating ~2019

Fusion Test Facility (FTF or PulseStar)

• 0.5 MJ laser-driven implosions @ 5 Hz • Pellet gains 60 • 150 MW of fusion thermal power• Target physics• Develop chamber materials & components.

Stage III 2023-2031

Prototype Power Plants (PowerStars)• Power generation• Operating experience• Establish technical and economic viability

5) We have proposed a three stage program a) Well-defined “go / stop” points b) Progressively more capable facilities

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STAGE I is a single laser module of the FTFcoupled with a smaller target chamber

Laser energy on target: 25 kJRep Rate: 5 Hz (but may allow for higher rep-rate bursts)Chamber radius 1.5 m

~28 kJ KrF Laser(1 of 20 final ampsneeded for FTF)

Target Chamber

Target Injector

Target

Mirror

90 beamlets

• Develop and demonstrate full size beamline for FTF• Explore & demonstrate target physics underpinnings for the FTF

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A prescription to realize a practical fusion energy source within the next few decades

1) Fusion energy is a worthy goal---Don’t get distracted

2) Encourage competition & innovation.

3) Pick approaches (fusion concepts) that: a) Value simplicity b) Lead to an attractive power plant

(technically, economically, environmentally…) c) Requires less investment to develop

4) Develop science & technology as an integrated system

5) Staged program with well defined “go / no-go” points Elements developed and incorporated into progressively

more capable facilities

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The Vision…A 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

Working in 25 years or less