Yasukazu Izawa Institute of Laser Engineering, Osaka University

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Yasukazu IzawaInstitute of Laser Engineering, Osaka University

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

Development of HALNA DPSSL for IFE

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Tadashi Kanabe*, Masanobu Yamanaka**, Ryo Yasuhara, Junji Kawanaka, Noriaki Miyanaga, Takayoshi Norimatsu,

and Masahiro Nakatsuka Institute of Laser Engineering, Osaka University

*Fukui University** Graduate School, University of Advanced Photonics

Osamu Matsumoto, Toshiyuki Kawashima, Takashi Sekine, Takashi Kurita, Tadashi Ikegawa, Masahiro Miyamoto,

Takeshi Kanzaki and Hirofumi KanHamamatsu Photonics K.K.

Hiroyuki FurukawaInstitute for Laser Technology

ILE OSAKA

Contributors

Institute for Laser TechnologyILE OSAKA

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ILE OSAKA

ţIgnition & burnRepetition testFIREX-IFIREX-II2005201020152020202520302035100J1kJţPower Generation: 2MWeţPractical Power Demonstration

Advanced LaserReactor Technology Development (Blanket, Liquid Metal, Final Optics, Tritium, Material, Safety)

Output:100Å`200MWeDEMODesign2003Experimental Reactor (LFER)EngineeringDesign

Laser: 200kJ/1Hz, Thermal output:10 MWthTarget Fabrication and Injection Reactor Chamber & Liquid Wall Technology10kJDriver DevelopmentConceptualDesign

By IFE Forum (2003)

Roadmap for Laser Fusion Energy Development

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Laser for implosion: 100kJ

Reactor chamber Laser for heating 100kJ

Target injector

Turbine generator4MWe

FIREX LFER (10MJ, 1Hz) DEMO1MJ Solid wall Liquid wall 200MJ, 3Hz

Laser Fusion Experimental Reactor (LFER)

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Two approaches for IFE driver development

◇ 　 HALNA (High Average-power Laser for Nuclear-fusion Application) 　　 conceptual architecture consists of water-cooling, Nd:glass medium 　　 and zig-zag slab geometry and multi-pass amplifier.

◇ 　 Current goals of the HALNA are 100 J pulse energy, 10 Hz operation 　　 and beam quality less than 5 times of diffraction limit (TDL) with 10% overall efficiency.

◇ 　 New approach is to use cooled Yb: YAG ceramic slab. (20 x 20 x 5 cm for 1kJ, T = 150 ~ 225 K) (To be presented by J. Kawanaka)

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HALNA: High Average-power Laser for Nuclear-fusion Application

Output10 kJ (351 nm)OscillatorMirror1D ExpanderPolarizerFaraday Rotator PolarizerGain MediaSpatial F ilter1601002010010050014555Mirror6040150ω3KDP (for Main Amplifier Path)Isolator {Mirror130Mirror(for Main Amplifier Path)Pockels C ell & Mirror {250Phase-coupling Mirror2055(for Pre-Amplifier Path)Inputμ10 J /beamlet& λ/2 Plate Åõ(45 )Åõ(45 )(for Pre-Amplifier Path)Faraday RotatorMirrorÅEDiode-pumped solid-state laserÅEWater-cooled Nd:glass gain mediumÅEZig-zag slab geometryÅEMultipass amplifier architectureÅEPhase-coupled beam combining

10 kJ output energy at 351 nm10 Hz repetition rate10 % overall efficiency

LDLD (40 x 5 cm2) x 2Pumped region12 cm52.3 cmLDLD2 cm2 cm52.3 cm12 cmLDLD(40 x 1 cm2) Pumped regionHALNA 10(10 J x 10 Hz)HALNA 100(100 J x 10 Hz)HALNA 1K(1 kJ x 10 Hz)

(40 x 50 cm2) x 2Pumped regionLDLD2 cm56 cmLD52.3 cmLD0.2 MW diode-pumping2 MW diode-pumping20 MW diode-pumping

HALNA conceptual design includes diode-pumping, HALNA conceptual design includes diode-pumping, water-cooled glass and zig-zag slab optical geometry.water-cooled glass and zig-zag slab optical geometry.

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FY2002 FY2003 FY2004 FY2005 FY2006

HALNA 10 (10 J x 10 Hz)

HALNA 50 (50 J x 10 Hz)

HALNA 100 (100 J x 10 Hz)

Pump intensity : 2.5 kW/cm2

Zig-zag slab geometry : SSG 10Beam fluence : 5 J/cm2

Pump efficiency : 50%Stored energy density : 0.5 J/cm3

Extraction efficiency : 50%Opt.-opt. Efficiency : 20%1/5 fracture limit operation Dual amplifier head

Full aperture : 12 cm2

Fluence : 8 J/cm2

Larger apertureEdge-cladding for parasiticFluence: 5 J/cm2

1/3 fracture limit

Part of research is supported by NEDO(New Energy and industrial technology Development Organization) under METI (the Ministry of Economy, Trade and Industry),Japan.

20 J x 10 Hz DPSSLfor NEDO project

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Research and development plan for HALNA 100

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ILE OSAKA10J/10Hz system HALNA 10 has been developed.

1053 nm10 J, 10 Hz, 10 ns< 5x TDLWaterOscillatorPre-AmpSpatial filter - 1Spatial filter - 2Laser OutputLD modulesNd:glassFaraday rotatorExpanderApertureSlab amplifier headLD module for pumpingSlab amplifier : 8x10x240 mm 4 pass, Diamond geometryFaraday rotator for thermal effect compensation

Pre-AmpOscillator

Zig-zag slabAmplifierSpatial filter

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Left bank(Module 1)

Right bank(Module 2)

Output peak power 120 kW

Emission wavelength 803 ±1nm,

Bandwidth < 4 nm (FWHM)

Material AlGaAs

Peak pump intensity 2.5 kW/cm2

Wall plug efficiency > 50 %

Diode current 100 A

Repetition rate 10 Hz

Pulse width 0.2 - 0.4 ms

Duty 0.2 - 0.4%

PHOTON IS OUR BUSINESS

Pump module performance

Total 2,400 bars have been integrated into two pump diode modules. Those have been activated in October, 2003

10

0

40

80

120

160

0

15

30

45

60

0 20 40 60 80 100 120 140

Peak power and efficiency

Module 1 (Left bank)

Module 2 (Right bank)

Module 1 (Left bank)

Module 2 (Right bank)

Current [A]

HALNA driver requirements

52.1 % at 100A

52.8 % at 100A

145.4 kW at 120A

145.7 kW at 120A

Repetition rate : 10 HzPulse Width : 200 μsCooling water temp. : 25 deg.

55 %

E-O

con

versio

n e

fficien

cy [%

]

Pe

ak

po

we

r [k

W]

0

0.2

0.4

0.6

0.8

1

1.2

790 795 800 805 810 815 820

Spectral profile

Module 1 (Left bank)Module 2 (Right bank)

Wavelength [nm]

LD Current : 100 ARepetition rate : 10 HzPulse Width : 200 μsCooling water temp. : 25 deg.

FWHM : 3.39nm

Peak wavelength : 804.13 nm

Inte

nsi

ty

[a.u

.]

Total 290 kW output peak power was successfully achieved from total 2,400 diode bars at 804 nm.

Left bank (1,200 bars)Lasing !

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Emission cross section 3.6 x 10-20

Fluorescence lifetime 350 µs

Thermal conductivity 1.02 W/mK

Thermal expansion coefficient 8.5E-6 K-1

dn/dt 1.8E-6 K-1

Absorption coefficient 2.31 W/cm

Physical propertiesHAP-4(Nd:1.1wt.%), HOYA Co.

Amplifier housing

34 cm (length) x 1 cm (width) with slab aspect ratio 2:1

Sol-gel coated at incident faces

Geometry for preventing parasitic without edge cladding

□

□

□

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Nd doped phosphate glass laser material is suitable Nd doped phosphate glass laser material is suitable for high energy DPSSL applications.for high energy DPSSL applications.

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Results of thermal effect analysis

Thermal analysis by LASCAD and THESLAC codes optimized slab dimension.

Physical properties.

Insulator

Height of glass

Teflon 10mm : É…=0.25W/mHighly insulatedmaterial10mmÅFÉ…=0.025W/m

without heat flux

(mm)

Maximumtemperature

diffrence ( K )

thermal lens focallength ( m )

Effciency ofpump light ( % )

Depolarizationloss (%)

Maximumtemperature

difference ( K )

thermal lensfocal length ( m )

Thermal lensfocal length ( m )

21 3 140 88 5.4 -100

22 4 90 97 6.2

23 6 90 100 7.7

24 100

25 8 28 100 6.7 7 35

(1) (2) (2)

LASCAD gives temperature, stress and deformation of laser glass .THESLAC code calculates wavefront distortion and birefringence.

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Nd:HAP4

Thermal conductivity:É… 1.02E+00 W/(mK)

Coefficien of thermal expansion 8.50E-06 1/K

Elastic modulus 68800 N/mm^2

Poisson's ratio 0.236

Refractive Index 1.533

Temperaturdependence of refractivindex dn/dT 1.80E-06 1/K

Absorption coefficient, 0.231 W/mm:

Heat efficiency factor 0.3Slab pumping geometry

LD module

Insulator

Height of glass

5°

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Thermal modeling revealed optimum slab height for minimizing thermal lensing effects

1.Temperature distribution

4.Thermal birefringence3.Wavefront distortion

Tem

pe ra ture ( K )

Lo ss ( % )

Slab height ( mm ) Slab thickness ( m

m )

λ( μm )

-5

0

5

10

15

20

25

-2 0 2 4 6 8 10 12

2. Thermal deformation

Sla

b he

ight

( m

m )

Slab width ( mm )

Slab height ( mm )Slab th

ickness ( mm )

Slab height ( mm )Slab th

ickness ( mm )

Thermal analysis results by THESLAC code ■　 Optimum range of slab height

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Slab height must be carefully decided, taking into account of pump efficiency and thermal lensing effects.

Thermal lensfocal length

Maximum temperature difference

Thermal lensfocal length

Maximum temperature difference

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0

5

10

15

0.0 0.1 0.2 0.3

Input [J]

Output [J] Pumping length Beam width

268mm 10mm

268mm Å@8mm

Output energy greater than 10 J is predicted .

Input energy vs. output energyBeam width vs. output energy　 Input energy : 0.1 J

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Output energy was analyzed based on Frantz- Nodvik and Eggleston- Frantz equations.

　 Pumping length : 26.8 cm　 Pumping energy : 48 J

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The HALNA10 has successfully yielded 84-W average power at 10 Hz in December, 2004

10.6 J operation at 1 Hz 84 Waverage operation at 10 Hz

Filling factor : 49%

2TDL

Near-field Far-field7.6mm

17

mm

Near-field

Filling factor : 63%

26 ns (FWHM)

Far-field

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2TDL

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Component Parameter Goal Result

Pump diode

Output peak power 120 kW 145 kW

Pump intensity 2.5 kW/cm2 2.59 kW/cm2

Emission wavelength803 ±1nm,

<4 nm(FWHM)

804.1nm,

3.4 nm(FWHM)

E – O efficiency 55% 52%

Slab amplifier

Small Signal Gain 10 8.5

Pumping efficiency 45% 45%

Total system

Repetition rate 10 Hz 1 Hz 10 Hz

Output energy 10 J 10.6 J 8.4 J

Extraction efficiency 45% 43.9% 34.9%

O – O efficiency 20% 19.9% 15.8%

E – O efficiency 10% 10.3% 8.2%

Filling factor 50% 49% 63%

Beam quality < 5TDL80%

(<5TDL)70%

(<5TDL)

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The HALNA 10 has virtually accomplished their The HALNA 10 has virtually accomplished their goals, demonstrating the feasibility of IFE drivergoals, demonstrating the feasibility of IFE driver

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Yb: doped fiber oscillator

Nd: YLF regenerative amplifier (8mm, 0.5J/10ns)

Nd: glass slab amplifier (5 x 1 x 30 cm, 4 pass)

2 slabs: 25J/10ns, G0 = 3

1 slab: 20J/10ns, G0 = 6.3

Wavefront control: deformable mirror/phase conjugate mirror

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HALNA 50/20 has been designed and is under construction.

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HALNA 50/20 with thermally-edge-controlled slab (TECS) amplifier

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200-kW diode module(2000 bars)

200-kW diode module(2000 bars)

Cooling water

Laser slab

Edge claddingEdge heater

Laser beam

Diamond geometrydue to zigzag path

Delivery optics

38 cm

Laser material: Nd:phosphate glassSlab size: 5 x 1 x 30 cmPump energy: 80 JSmall signal gain: 3/pass

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Overlapping pump irradiation from each diode stack is effective in obtaining 10% uniformity on the slab face

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0-200 -150 -100 -50 50 100 150 200Position in mm

0

25

-50

-25

Po

sitio

n in

mm

VerticalHorizontal

Pump area : 300 mm x 50 mm Pump intensity : 1.3 ~ 2.5 kW/cm2

Pump duration : 150 ~ 300 µs Stored energy density : 0.19 ~ 0.32 J/cm3

Small signal gain : 3.0 ~ 6.3 /pass

Pump distribution on slab face (simulated by 3-D ray tracing)

Diode facet

Laser slab

Pump light

Lens cassette

Effective pump area

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◇ HALNA driver for IFE has been developed.

◇ The HALNA 10 has achieved 8.4 J at 10 Hz with beam quality of 2 xDL　 in December, 2004.

◇ A larger slab amplifier with 5-cm2 aperture has been designed, and it 　 is under construction.　◇ In 2005, the dual slab system will demonstrate the 20 J x 10 Hz 　 operation with a wavefront correction for the NEDO project.

◇ In 2006, a half of HALNA 100 will be constructed with 10-cm2 aperture, 　 the 50 J x 10 Hz operation will be the objective of the moment.

Summary

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ILE at Osaka collaborates on HALNA project with Hamamatsu Photonics and ILT

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