Fast Ignition-High Energy Density Science and Fusion

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Fast Ignition-High Energy Density Science and
Fusion

• E. M Campbell
• General Atomics
• Oct 28, 2003
• FESAC IFE Study
• Albuquerque, New Mexico

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Presentation Summary

• Short pulse (? lt 10 psec), high peak power
  lasers (P gt 1015 Watts have enabled the new field
  of ultra-high energy density physics (UHEDP)
• There is an increasing national and international
  interest in UHEDP
• Fast Ignition is an innovative and promising
  Fusion concept that exploits the physics and
  technology of UHEDP
• Fast Ignition has many attractive features
• Science frontier-relativistic plasmas,etc
• Compatible with all implosion concepts and
  drivers- ( perhaps even 0.532?m, 1.05?m (?)
  lasers)
• 100 ev radiation drive required for compression!
• Flexibility in reactor concepts
• Reduced target fabrication requirements
• International collaborations
• High gain at sub-megajoule energies
• A credible pathway exists over the next 5-7
  years, utilizing NNSA and international
  facilities, particularly Japan, to
  explore/develop FI concept thru theconcept
  extension phase at a reasonable cost

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Presentation Outline

• Motivation and Background (Charge4)
• Challenges (Charge 2)
• Current Status (Charge 1)
• Path Forward (Charge 3)

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Motivation/Background
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Fast Ignition is one of the applications of the
emerging field of Ultra-fast, Ultra-intense
Lasers (UUL)
Interest in HEDP and applications of UULs is
growing and extends outside of the Fusion
Community- over 25 lasers (P gt10 TW)operational
worldwide! (SAUUL Report)
6
Ignition and gain curves for multiple target
concepts show the advantages of Fast Ignition
FI at NIF
Intensity 1014 - 1015 w/cm2
Advanced Indirect Drive on NIF
Intensity 1020 w/cm2
Indirect Drive

Fast ignition potentially gives more gain and
lower threshold energy then Hot Spot ICF but
the science and technology are far less developed
7
Fast Ignition has numerous attractive features in
addition to high gain at lower total drive energy

• Compression can be done with all Drivers (longer
  ? lasers (?))
• Brightness requirements for compression drivers
  are reduced
• target fabrication tolerances are relaxed (needs
  to be quantified)
• Direct and Indirect target schemes for
  compression
• Innovative target concepts
• one-sided indirect driver ( I.e. (no beam
  bending for HIF)
• indirect drive illumination for direct drive
• asymmetric compression drive configurations

Innovative reactor concepts
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NNSA is interested too! The photons, electrons
and ions from UUL can be used to heat and
diagnose HEDP plasmas
-Trad 1 KeV (?)
Multi-kilojoule PWs are now planned for Omega,Z,
and NIF
9
NNSA has identified need for adding PW to
existing facilities

• Radiography
• High energy (h? gt30 keV) xray backlighting
• Proton Radiography (under development)
• Ultra-high energy densityphysics
• -P gt1Gbar
• TR 1 KeV
• Isochroic heating
• Ions, high energy photons (under development)

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Ultra-high intensity laser pulses can efficiently
generate intense, energetic beams of protons
Laser-Ion diode Characteristics

• Transverse emittance lt 0.006 p mm-mrad
• Longitudinal emittance lt keV-ns (velocity
  correlated)
• Energy spread 100
• Bunch charge 1011 1013 protons/ions
• Source diameter 50 mm (fwhm)
• Charge state purity gt80 He-like
• Particle current gt100 kA (at source)
• Laser-ion efficiency gtgt 1 (4-20 observed)

P K Patel et al
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PW ION-Plasma coupling experiments have
begun100TW,100fs expt. at JanUSP shows proton
focusing and enhanced isochoric heating of a 10
micron Al foil
50 mm
200mm
gt400mm
Streak images of visible Planckian emission
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Al has been heated to 23 ev by a focused laser
produced proton beam
T 23 ev (7 x 105 j/g) (0.2 joules from 10 joule
laser)

• Proton conversion efficiencies have been shown to
  scale with laser energy to at least the 500J
  level.
• Focused proton beams from PW-class lasers could
  produce ultrafast localised heating of matter to
  100's eV or keV temperatures.
• Material can be precompressed

P K Patel et al
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Proton Radiography Development has begun
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High efficiency conversion of laser energy to
heavy ions is achieved by removing hydrogen
contaminants from target
50 mm W 1 mm CaF2 (900O C)
20 J, 350 fs 1.054 mm
4 conversion of laser energy to F7 ion beam
observed !!
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Laser-Ion acceleration should be explored in
conjunction with Heavy-ion Inertial Fusion
program and Fast Ignitor
gt TW / cm2 ion beams for HIF beam-target physics
prior to an Integrated Research Experiment
accelerator
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Challenges
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??Short pulse laser aimed and timed to imploded
fuel
Fast Ignition requires several key elements
??Efficient conversion Elaser? beam of MeV
electrons aimed at fuel
??Implosion to high density fuel
??Propagation of burn throughout fuel (need
rRgt1.8 g cm-2)
??Efficient transport of hot electron energy to
dense fuel
??Efficient deposition of electron energy in
region of rR0.5 g cm-2 (a range), heating it to
5-10 keV
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A short pulse (10-20 psec) laser is required PW
lasers have been made possible by advances in
laser ST over the past 1-2 decades

• Chirped Pulse Amplification (CPA) -TW/cm2
• Large Aperture gratings 1000 cm2
• 1st generation Au (Edam.25-.4 j/cm2)
• 2nd generation dielectric
• Multi-pass amplifier architecture
• Compact, efficient energy extraction
• Phase front control (DFM)-beam focusability

CPA
MPAA
DFM
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Efficient, Damage resistant dielectric gratings
are required for FI
FI ?
Ignition Aperture (cm2) Eig / 3
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Beam diameter and collimation of transport from
laserto ignition hot spot determine ignition
laser energy

• Ignitor laser energy
• scales with transport
• efficiency
• Eig(kJ) ?-1 (140 (100/?)1.88)

Electrons
Laser
Fuel
fs

• Ideal collimated
• Divergent - efficiency loss

fb
The ignition energy is known - the required laser
energy is not well known at present- depends on
transport efficiency
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The main physics challenge for FI is to deposit
sufficient energy into a ?R0.3 plasma

• The laser energy is absorbed at ne1021 cm-3 by
  relativistic electrons (Te1 MeV)-MAmps of
  current (gtgtIalfven)!
• ?R of 0.3 g/cm² plasma is at ne1025-1026 cm-3
• charge and current neutralization takes place
  thru warm, collisional electrons-

Transport and heating experiments must be done in
warm (0.1 to 1 keV),dense plasmas and distance
between deposition and ignition regions must be
minimized!
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Ignitor electron transport must be studied in
plasmas where where conductivity is in Spitzer
regime, and high enough that the hot e-
transport is not dominated by resistive effects
FI imploded fuel
r 100 g cm-3
Electrical Conductivity s-1
r 10
r 1
Current (foil) experiments
Te keV
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Cone-focused scheme has been developed to
facilitate ignitor beam deposition
?? Low aspect ratio capsule Get hi r fuel with
relatively low drive symmetry no significant
stability issues.
???Cone provides pointing puts deposition of
laser v. close to hi r fuel
??Elaser ??hots at surface, 50 conversion
(expt)
??Laser spot size pulse length tuned to give
hot es with optimum range
Closed andopen tipped
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Current Status
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??Short pulse laser aimed and timed to imploded
fuel
Present research is addressing critical elements
of Fast Ignition concept
??Efficient conversion Elaser? beam of MeV
electrons aimed at fuel
??Implosion to high density fuel
??Propagation of burn throughout fuel (need
rRgt1.8 g cm-2)
??Efficient transport of hot electron energy to
dense fuel
??Efficient deposition of electron energy in
region of rR0.5 g cm-2 (a range), heating it to
5-10 keV
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The OFES Concept Exploration (CE)
activity(LLNL,UC-Davis, GA, PPPL) in Fast
Ignition has been successful

• Experiments have clarified issues with electron
  transport
• Cold, highly collisional return current electrons
  dominate transport of collisionless MeV hot
  electrons
• Layered targets (initially cold) are not
  appropriate to mock up transport problem
• Fuel Assembly with cone targets
• Indirect drive
• Direct drive
• Collaborations established with US and
  international facilities (Omega, Z, Trident,
  JanUSP, RAL,GEKKO ,LULI)
• Low emmittence, high brightness ion sources
  identified
• Possible applications include FI, HIF,
  accelerators, Isochroic heating

Supplemented by internal funds at LLNL and GA
OFES CE has maintained US presence in FI
research
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Ka image data show cone angle and minimum beam
radius for electrons in Al
180 mm
RAL 100J,0.8 ps

Ka image radius ( half max ) micron
LULI 20J,0.5 ps
Cone angle 40o Min radius 37 mm
Cu
Al 20 mm
Al thickness micron
Resistivity effects dominate in these cold
plasmas
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Cone-focussed, directly driven OMEGA implosions,
diagnosed by radiography are used to benchmark FI
implosion concepts
Simulated backlit radiograph (6.7 keV)
24 µm
860 µm
Radiographs
Vacuum
CH
Omit 5 beams from solid angle subtended by cone.
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FI laser driven Indirect Drive implosion
Elaser14 kJ
T180 ev
Rad Temp (ev)
Scales to 27 MJ yield on NIF with 50-80 kJ of
ignition laser
t (nsec)
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Experiment and simulation are in qualitative
agreement
ILE Osaka
Simulation
Experiment
X-ray backlight _at_ hn 6.7 keV
r 20 g/c.c.
r 27 g/c.c.
NIF implosion would scale to ?? 400 g/cm3
375 mm
The exp. also shows blow-off plasma from Au tip
due to Au M line emission from the laser heated
regions of the hohlraum.
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A z-pinch driven fast-ignitor concept is being
developed
PW laser access to compressed fuel inside capsule
support stalk
D. Hanson, R. Vesey, et al.,,
Short secondary for optimum symmetry
2-mm-diam hemi- spherical capsule on support stalk
wire array

Au-coated glide plane
Liquid D2

electron or ion conversion target

• NIF designs are also being explored (Hatchett)

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Fast ignition imploded fuel designs are being
developed with experiments on Z
D. Hanson, R. Vesey, et al., 6th Fast Ignitor
Workshop, 2002
Z923 backlit image
Backlighter LOS
7.5 mm
mounting pedestal
Synthetic image
8th order fit
2D LASNEX
original capsule profile
2D time-dependent viewfactor

• Preliminary image analysis agrees qualitatively
  with 2D simulations
•  2D simulations give polar-averaged peak r 60
  g/cc, r r 0.3 g/cm2
• Simulations for ZR with cryo-DT capsule give r
  160 g/cc, rr 0.65 g/cm2

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Integral FI experiments have been performed on
the GEKO XII laser and PW Facility
GEKKO laser 12 green laser beams E 10 kJ, t
1-2 nsec. Uniform irradiation(phase plates) for
high density compression. I 1014 watts/cm2
PW laser 1 beam (400 J) At 1 micron. PW peak
power is utilized for fast heating. I1019
watts/cm2
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Parameters for Integral Fast Ignition Experiments
PW for heating 1 beam / 300 J 1.053 mm / 0.5ps
GXII for implosion 9 beams / 2.5 kJ/0.53
mm 1.2ns Flat Top w/ RPP
IL 1019 W/cm2
Au cone 30 o open angle (the picture
60deg) Thickness of the cone tip 5mm Distance of
the cone top 50mm from the center
CD shell 500mmf/6-7mmt
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Peta watt laser heating experimental results of
cone guide target
Implosion time
800keV
Required timing is 50ps
c
Neutron Yield
IF/OV1 T.Yamanaka
Heating Laser Power (PW)
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Experiments and Modeling are well matched at
300J,0.5 psec
Experiments are matched if 40 of PW laser energy
goes into relativistic electrons that then couple
to the imploded core (? 100 g/cc) !

Two temp.
Neutron Yield
Th 500keV
Th 2MeV
Heating Laser Power (PW)
KEY physics issue how relevant are 0.5 psec
laser experiments to 10-20 psec requirement for
FI?
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GEKO XII-PW success has motivated FIREXI

• FIREXI (University of Osaka)
• 10 kJ,10TW, 0.532 ?m implosion laser (GEKO XII)
  will be utilized
• GEKO XII demonstrated 600 g/cc and ?R 0.5 g/cm2
  in CD in 1984
• 10 kJ, 10 psec 1.05?m ignitor system (4 beams)
  will be added by 2005

IF GEKO XII experiments scale then FIREXI will
achieve Q 0.2 with a total laser energy of
20kJ!!!
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Path Forward
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A credible pathway to take FI to concept
demonstration exists

• Proof of Principle (Performance Extension)
  Significant core heating at relevant conditions
• FIREX1 (Japan)
• US (OFES) participation
• -NNSA facilities with multi-kJ PW (OFES
  participation)
• Concept Demonstration (Ignition/gain)
• US Facilities (?, Z, NIF) with 30-100 kJ PW
• Japan participation (Japan may propose FIREXII if
  FIREXI successful)

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A credible US pathway for FI progression from
Concept Exploration to Proof of Principle Exists

• Proof of Principle (Demo significant core heating
  of relevant imploded fuel assembly)
• -FIREX1
• Multi-KJ PW laser added to Omega, ZR, NIF,

• NNSA funds facility (incl PW)
• OFES funds specific science (Interface with
  Japanese)
• -Japan funds FIREX1

FIREX1,Omega, ZR, NIF
Multi-KJ Petawatt ST -Gratings -Facility Issues
Concept Exploration -Implosions -Laser-plasma
interactions -Transport
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GEKO XII-PW success has motivated FIREXI-FI with
Direct Drive

• FIREXI (University of Osaka)
• Existing 10 kJ,10TW, 0.532 ?m (GEKO XII)
  implosion laser)will be utilized
• GEKO XII demonstrated 600 g/cc and ?R 0.5 g/cm2
  in CD in 1984
• 10 kJ, 10 psec 1.05?m ignitor system (4 beams)
  will be added by 2005

IF GEKO XII experiments scale then FIREXI will
achieve Q 0.2 with a total laser energy of
20kJ!!!
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PoP FI (Direct Drive)Experiments should be
possible with Omega EP
? Implosion 1 kJ (?PW)
? Implosion
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The NIF deployment strategy would allow
proof-of-principle experiments in FY07.
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Early NIF proof of principle experiments can
demonstrate indirect drive FI implosion.
Energyblob 2 kJ
( 3/4 ign. Scale)
Imploded fuel is cold (200 ev) so no
self-emissions - radiography is required.
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PoP on NIF A single short-pulse beamlet (2.5 kJ
in 10 psec) may provide quantitative information
on ignitor electron deposition in FI relevant
plasmas
Yn2e9 neuts
Yn5e8 neuts
Collimated
Divergent (40 fwhm)
K-? from a trace constituent, e.g. Zr K-? at
15.7 keV with crystal imager, is proportional to
the energy deposition of hot es.
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The Z-Beamlet laser is being modified to provide
gt 1 kJ in 5 psec to test the Fast Ignitor
indirect drive target concept with a pulsed
power implosion driver
Z-Beamlet Laser
Z Machine
Fast Ignitor target
Predicted neutron yield
X-ray images of imploding capsule
Fast Ignitor
2 mm
time
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PoP experiments (FIREXI, ?, ZR, NIF) should
determine the size of the ignitor laser

• Eig (kJ) 140 (100/?)1.88 ?-1
• ? 200-400 g/cc than Eig (kJ)(9-35) /?
• ? 200-400 g/cc is required for main fuel in
  conventional ICF
• Goal of Omega in 2005 (Cryo target system in
  place!)
• Goal of NIF in 2011
• PW development goal is 3-5 kJ /aperture with 20
  psec pulses
• If e beam is collimated, ? 0.3 leads to ignitor
  laser of 30 to 100 kJ

PoP will determine ? at relevant parameters for
FI!
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Proposed Roadmap for IFE by Fast Ignition
FY03
FY12
FY06
FY09
FY15
Concept exploration
Concept Demo (Ignition) Ecomp50-1000 kJ Eheat
30-100 kJ
PoP/PExt Ecomp10 kJ Eheat10 kJ
ETF
US
Firex I Q0.2
Japan
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Significant progress on FI should occur over the
next several years if

• NNSA (strong Congressional Interest) adds 2-5 kJ
  (10 psec) PW to ?, ZR, NIF
• Large dielectric gratings are developed
• FIREXI is constructed in Japan
• OFES funds PoP effort (2-4M/year)
• US-Japan cooperation
• Fuel assembly at Omega and NNSA facilities
• Heating/transport at GEKO-PW
• Modeling
• PoP experiments at FIREXI and NNSA Facilities