Overview of FIREX Program

Yasukazu IzawaInstitute of Laser Engineering, Osaka University

5th US-Japan Workshop on Laser IFE March 21-22, 2005General Atomics

ILE OSAKA

Outline

1) FIREX was assigned as one of the next fusion program.

2) Construction of 10kJ/PW new heating laser LFEX

3) Toward FIREX�cryogenic foam shell target�code development: FI3�cone-shell target implosion: GEKKO XII and OMEGA�basic experiments on hot electron transport�suppression of Rayleigh-Taylor instability

4) Summary

ILE OSAKA

Neu

tron

Yie

ld

Heating Laser Power (PW)

15%

Heating efficiency: 30%

108

106

1040.1 1

Ignition equivalent laser intensity

Cone shell target

PW laser 1.053µm

GEKKO XII 9 beams 0.53µm 1.2 kJ / 1ns

Au coneplastic shell

Fast ignition experiments by the PW laser demonstratedthe heating efficiency of 20%.

Enforced heating was realized at a heating power equivalent to the ignition condition.

2.25 2.35 2.45 2.55 2.65

Neu

tron

Sig

nal (

a.u.

)

Energy [MeV]

0

1.0

0.5

b

FWHM: 90±5keV keVResolution:50 keV

0.86 ±0.1 keV

500J500fs

Neutron time-of-flight

(CD shell)

ILE OSAKA

FIREX : Fast Ignition Realization Experiment

1995 - 1999�GEKKO MII CPA (25J, 0.4ps, 60TW)�PWM laser (70J, 0.7ps, 100TW)

Elementary physics related to fast ignitor (laser hole boring, super-penetration, MeV electrons, Self-guiding, Cone-guiding)

1999 - 2002�PW laser (700J, 0.7ps, 1PW) + GEKKO XII

Heating of imploded plasma up to 1keV by cone-guiding

2003 - 2008 : FIREX-I (Phase 1)�New heating laser (10kJ, 10ps, 1PW) + GEKKO XII

Heating of cryogenic target to 5 ~ 10keV

2009 - 2014 : FIREX-II (Phase 2)�New compression laser (50kJ, 350nm) + Heating laser (50kJ, 10ps)

Ignition and burn, gain ~ 10

ILE OSAKA

Laser fusion (FIREX) has been assigned to be one of the next fusion programs in Japan.

Report of WG on Fusion Research, Council of Science and Technology,MEXT, Japan (January 8, 2003)

Four fusion programs have been selected.# Tokamak: ITER, JT 60-U (JAERI)# Reactor Technology: IFMIF# Laser: FIREX (Fast Ignition Realization Experiment) (Osaka)# Helical: LHD (NIFS)

New project

Fast ignition program

# Fast ignition program FIREX is expected to open a completely new fusion energy based on the advanced laser technology.

# It is necessary to start FIREX-Phase I program. The start of the FIREXPhase II will be decided based on the assessment of Phase I.

ILE OSAKA

Time table of FIREX

Japan FY 2000 01 02 03 04 05 06 07 08 09 10 11 12 13 14

Ignition and Burn (FIREX-II)

Ignition Temperature (FIREX-I)

Heating laser Heating LaserConstruction

1PW1kJ/1ps 10kJ/10ps 50 kJ Upgrade

ImplosionLaserConstruction

Implosion laser

1-keV Heating

GEKKO-XII 10 kJ/2ns/0.53µm50kJ/3ns 0.35µm

KD2: Demonstration of ignition temperature,and FIREX-II will start.

KD1: Demonstration of heating,and FIREX-I has started.

�@

�@

Existing GEKKO-XII

Laser bay

Gear room

Pre amp.

Main amp.

CompressorFocusing system

FIREX-I: Achievement of ignition temperature

Program of Fast Ignition Realization Experiment FIREX Phase I: FIREX-I Heating to Ignition temperature Phase II: FIREX-II Demo of ignition&burn

Target room I

ILE OSAKA

LFEX (10kJ, 1PW) for FIREX-I is under construction.

Output energy 12kJ/4beams (chirped pulse)10kJ/4beams (compressed)

Wavelength 1063nmPulse shape 10-20ps (FWHM)

Rise time 1-2psFocusability 20µm in diameter (50% efficiency)Prepulse < 10-8

10kJ PW laser

ILE OSAKA

2.5 kJ /1-10 ps

3.2 kJ / 2 ns

Front end(existing)

OPCPA

Booster amplifier CompressorRod amplifier

Focusing optics

Rod amplifier

Timing adjuster

Fast phase adjuster Adaptive mirror

(in beam phase correction)

Adaptive mirror(beam-to-beam phase locking)

Basic configuration of 10 kJ/PW laser, LFEX�4 pass booster amplifier with angular multiplexing�adaptive optics for precise phase control�arrayed dielectric grating in large scale�4 beam combining to a single focal spot

ILE OSAKA2x2x8 disk amplifiers (NIF Glasses)Beam size: 40 x 40 cm in each beam

Beam path of 4-pass amplifier by angular-longitudinal multiplexing

Spatial filter

Amplifier head

End mirror

Fore focal plane

Back focal plane1st pass

2nd pass

Input

Deformable mirror

Pick-up mirror

2-mrad angular multiplexing

(0.5-mrad longitudinal multiplexing)

3 kJ/2.3 ns∆λ = 3 nm

Beam transferin each four pass amplifier

ILE OSAKA

GEKKO XII

10kJ, PW laser LFEX

OS 75S

OS 125S

DA 400S

SF 400S

DFM 125

DFM 75RA 50

Main amplifier chain for LFEX has been completed.

ILE OSAKA

Pulse compressor and focusing optics of LFEX

Mirror8

ExperimentalChamber

Off-axis Parabola

AdaptiveOptics

Grating Station1

Grating Station2

Mirror1

Mirror2

Mirror3

Mirror4Mirror7

Mirror5Mirror6

Laser Beamfrom Front End

ILE OSAKA

∆y∆z

x

y

zθzθy

θx

1st grating

2nd grating

Ti: sapphire CPA beam

Monolithic grating

200 fs

2nd order auto correlation trace

Far-field pattern

Arrayed grating

200 fs

optimized

Test of arrayed grating started.

(Arrayed)

Preliminary experiment

ILE OSAKA

Roof mirror

Off-axis parabola mirror

GEKKO XII target chamber

Beam monitor

F/~4.5

Beam combining/focusing geometry depends on the possible performance of a large-aperture parabola mirror.

80% 60%

20 µm

d = -160 µm -110 µm -55 µm 0 µm

Single-beam phase aberration λ/5 Beam-to-beam phase jump λ/5

Layout of beam combining / focusing optics

�Phase control less than λ/5 is required for high focusability.

ILE OSAKA

Focal spot is sensitive to phase distortion.

δλ31

=∆0=∆λ

δλ =∆ δλ32

=∆

Phase Shifts at Four Segments

Inte

nsity

(arb

. Uni

t) Encircled Energy

Strehl ratio

78% in 20µm spot

S = 0.56

µm

µm

Encircled Energy

Strehl ratioS = 0.29

74% in 20µm spot

Inte

nsity

(arb

. Uni

t)

δλ31

=∆

0=∆λ

δλ =∆

δλ32

=∆

Even though the level of phase shift are same,the focal spot shape depends on the orientation

When δ=π and λrms=0.1λ

ILE OSAKA

Foam cryogenic cone-shell target is under development.

Target fabrication

Foam shellwith gas barrier Ultra-low-density (<10 mg /cm3) plastic foams

were fabricated.

ρ =10 mg/cc ρ =5 mg/cc

ILE OSAKA

C

C*

C

*

O

C C

H3C

O

CC

CO O

n

HC

HC

HO OHHO

OH

HC*

CH n

CHCH2

HCCH2

CH3H3C n

Ultra-low density (< 10 mg/cc) foam is expected by poly (4-methyl-1-pentene)(PMP).

Acrylic resin

RF polymer PMP

RF foam

PMP foam

PMP foams prepared froma) 1-butanolb) 2-butanolc) 2-methyl-1-propanold) 2-methyl-2propanol

ILE OSAKA

Cryogenic test apparatus has been developed at NIFS.

Collective PIC code

ILE OSAKA

FI3 (Fast Ignition Integrated Interconnecting) Code was newly developed.

• The cone-guided implosion dynamics is calculated by PINOCO. and the mass density, temperatures, and other profiles calculated by PINOCO are exported to both collective PIC and RFP-hydro code for their initial and boundary conditions.

•The relativistic laser plasma interaction inside the cone target is simulated by collective PIC code FISCOF1, which exports the time-dependent energy distribution of fast electron to REP-hydro code.

• The fast electrons calculated by the FISCOF1 are exported to the RFP-hydro code. Therefore, the core heating process is simulated using both physical profiles of imploded core plasma and fast electron as the boundary conditions.

•Those numerical codes are executed on the different computers via DCCP, TCP/IP network communication tools.

The first numerical fast ignition simulation was performed to demonstrate the FI3 and to investigate the GXII experiment.

Radiation-hydro. Code (PINOCO)

(cone-shell implosion)

Collective PIC codeFISCOF1

(laser plasma interaction)

Relativistic Fokker-Planck-hydro code

(hot electron transport)

Data flow in FI3 system. (Black arrows are already executable data flows, and gray arrows are next plan to be considered.)

Code development

ILE OSAKA

In the spherical implosion, the shell target reach the maximum compression at 2.285ns. In non-spherical implosion case, the shell continued to be compressed since a hot spot is not formed and an average ρR reached a higher value (0.15 g/cm2).

mass density

Time dependence of angular average ρR in gold cone-guided implosion (GXII scale CH target).

electron temperature

Imploded core plasma ρR is higher for cone target than for spherical target in PINOCO-2D simulations.

ILE OSAKA

Compressed-core profile by PINOCO Implosion simulation of a cone-shell target

(2D ALE code “PINOCO” by Nagatomo)

RFP-Hydro simulationsREB was injected at inner surface of a gold cone.

ILE OSAKA

Hot spot appears to flow out toward the cone tip.

Target: CH shell 900µmφ, 25µmtwith 70 deg cone

(General Atomics)

MIXS(Multi-Image X-ray Streak camera) for X-ray emission image: Japan

X-ray framing camerafor x-ray backlighting image (V, Fe) : US

Laser: 15kJ/1ns/35 beams0.35 µm

(OMEGA laser,LLE, Rochester)

∆t=10 ps

∆t=40 ps

Non-spherical implosion of cone-shell target byJapan-US collaboration at Rocherster's OMEGA laser

ILE OSAKA

0 2 4 6 8 100.01

0.1

1

10

100f (

E) [a

.u.]

100nc 2nc

Energy [MeV]

Fast electron energy distribution at a top of cone.This result is used for Fokke- Planck simulation

ILE OSAKA

IL,max = 1x1020 [W/cm2]

0 1000 2000 3000 4000 50001025

1026

1027

1028

Cor

e he

atin

g ra

te [W

/cm

3 ]

Time [fs]

ner = 2nc ner = 100nc

Core Heating Rate

0 1000 2000 3000 4000 50000.30

0.35

0.40

0.45

0.50

0.55

Cor

e Te

mpe

ratu

re [k

eV]

Time [fs]

<Te> <Ti>

ner = 2nc

ner = 100nc

Core Temperature

n = 100nc n = 2nc

Resultant core temp., <Ti> 0.43keV 0.50keV

Coupling efficiency in the case of n = 2ncfrom fast electrons to core is 25%, and from laser to core is 5.4%.

Integrated simulation results oncore heating rate and temperature

Hot electron generation and transport

ILE OSAKA

Heated blackbody emission was observed by HISAC.

Laser focused at 1019 W/cm 2

Plane target (Al)

Rear of the target is heated up by hot electrons.Black body emission was observed with time and spatial resolution.

Number of filaments decreases with increase of laser intensity and also with decrease of target thickness.

HISAC: Framing camera with ∆t = 30 psec and ∆x = 30 micron.

Y. Tohyama, R. Kodama et al., submitted to PRL (2004)

ILE OSAKA

Number of filament decreases quickly with increasing laser intensity.

Number of filament and peak brightness in rear emission were measured by 200 µm Altarget changing the laser power up to near PW. The filament could merge due to magnetic field generated by inhomogeneous conductivity,which depends on the temperature and/or heating power.

Hot electrons can be transported not breaking into filaments at the laser power of ~PW and be maintained in a flux to heat the core.

ILE OSAKA

Hot electrons were guided by carbon fiber.

Rayleigh-Taylor Instability

ILE OSAKA

γ = kg1 + kL

− βk Ý m ρa

k: wavenumber of perturbation g: gravity L: density scale length

β was estimated by measuring all parameters.

RT growth rate by Takabe formulam: mass ablation rate ρa: mass density β: numerical coefficient

10 100

2

1

0

Wavelength (µm)

Gro

wth

rate

(1/n

s)

�@�¡�@�@�@expÕt�@�@�@�@�@β = 1.7�@�@�@�@�@

β = 5

0 10 100

3

2

1

0

Gro

wth

rate

(1/n

s)

�¡ �Ÿ�@ expÕt�@�@�@�@β = 1.7�@�@�@�@β = 6

0

0.53 µm laser 0.35 µm laser

Wavelength (µm)

exp’tβ = 1.7β = 6

exp’tβ = 1.7β = 5

β = 1.7 for shorter wavelength of perturbation.β ~ 5 for longer wavelength.

ILE OSAKA

Two suppression schemes for RT growth were proposed.

3

4

5

6789

10

Gro

wth

Fac

tor

1. 61. 20. 8Ti me ( ns)

: Single-color (λ= 1/3 µm) irradiation: Two-colors (λ= 1/3 and 1/2 µm) irradiation

Rayleigh-Taylor Rayleigh-Taylor growth rate is reduced bygrowth rate is reduced by two-color laser irradiation. two-color laser irradiation.

Reduction of Rayleigh-Taylor Instability Growth with Multi-Color Laser Irradiation

Streaked image

1 ns 100 µm

one-color

Two-color (1/3+1/2-µm )

0.8 1.2 1.6 Time (ns)

25

20

15

10

5

0

Gro

wth

fact

or

2.52.01.51.00.50.0Time (ns)

CH

CHBr

�Double ablation by high-Z doping: ablations by electron and radiationincrease of ablation velocity

�Two-color irradiation: enhancement of nonlocal heat transport of electron increase of density scale length

ILE OSAKA

Gain prediction of FIREX’s and high gain targetby Fokker-Planck REB transport

ILE OSAKA

Laser fusion research is progressing towardignition and burn.

Ion temperature�iK�j

‰Á”M‚Ì�uŠÔ

�@

Nova

1022

1021

1020

1019

1018

106 107 108 109(

FIREX-I

FIREX-II

NIFGEKKO XII High densitycompression '88-89

GEKKO XII LHART '85-86

GEKKO IV '80-81

GEKKO MII '80

Fast ignition '02

Ignition

Fusi

on p

aram

eter

�is

ec/c

m3

�j

High gain

10 100 10000.1

1

10

100

Total Driver Energy [kJ]

ρ = 300 g/ cc and α = 2

FIREX-II

Experimental reactor LFER

Solid wall reactor

FIREX-Iρ = 300 g/cc, α = 2

Liquid wall reactor

Targ

et g

ain

IREB (1020W/cm2) FIREX-II 1.4 IFER 1.4 Solid 2.6 Liquid 2.6

Reactor technology: see Y. Kozaki et al., IAEA-CN-94/IF/P7-5

ILE OSAKA

Summary

1�Enforced heating of imploded plasmas has been demonstrated by using cone-shell targets.

2�We have started the FIREX project towards ignition and burn of laser fusion.

�FI3 (Fast Ignition Integrated Interconnecting) code was developed for target design.

�Cone-target implosion and hot electron transport have been studiedby the experiment and simulation.

�New stabilization schemes for R-T instability were proposed andsignificant suppression of instability were demonstrated.

� A new heating laser LFEX,10kJ/10ps PW laser,is under construction. Technical issues should be solved such as segmented grating andphase coupling.

�Foam cryogenic cone-shell target is under development.

3�FIREX-I experiment will start in 2007. Gain of up to 0.1 will be expected.