Development of HALNA DPSSL for IFE

Yasukazu IzawaInstitute of Laser Engineering, Osaka University

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

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Contributors

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

Institute for Laser Technology

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ILE OSAKA

Roadmap for Laser Fusion Energy Development

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�£Ignition & burn

Repetition test

FIREX-I FIREX-II

2005 2010 2015 2020 2025 2030 2035

100J 1kJ

�£Power Generation: 2MWe

�£Practical Power Demonstration

Advanced Laser

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

Output:100� 2̀00MWe

DEMODesign

2003

Experimental Reactor (LFER)Engineering Design

Laser: 200kJ/1Hz, Thermal output:10 MWth

Target Fabrication and Injection

Reactor Chamber & Liquid Wall Technology

10kJ

Driver Development

Conceptual Design

By IFE Forum (2003)

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ILE OSAKA

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)

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)

Oscillator

Mirror

1D Expander

Polarizer

Faraday Rotator Polarizer

Gain Media

Spatial F ilter

160

100

20100

100

500

145

55

Mirror60

40

150

ω3 KDP ( for Main Amplifier Path)Isolator {

Mirror

130 Mirror( for Main Amplifier Path) Pockels Cell & Mirror

{

250

Phase-coupling Mirror

20

55

(for Pre-Amplifier Path)Inputµ10 J/beamlet

& λ/2 Plate �›(45 )

�›(45 )

(for Pre-Amplifier Path)

Faraday Rotator

Mirror

�EDiode-pumped solid-state laser �EWater-cooled Nd:glass gain medium �EZig-zag slab geometry �EMultipass amplifier architecture �EPhase-coupled beam combining

10 kJ output energy at 351 nm 10 Hz repetition rate 10 % overall efficiency

LD

LD

(40 x 5 cm2) x 2Pumped reg ion

12 cm

52.3 cmLD

LD

2 cm

2 cm

52.3 cm

12 cm

LD

LD

(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 reg ion

LD

LD

2 cm

56 cm

LD

52.3 cm

LD

0.2 MW diode-pumping

2 MW diode-pumping

20 MW diode-pumping

HALNA conceptual design includes diodeHALNA conceptual design includes diode--pumping, pumping, waterwater--cooled glass andcooled glass and zigzig--zag zag slab optical geometry.slab optical geometry.

Research and development plan for HALNA 100

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

20 J x 10 Hz DPSSLfor NEDO project

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

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10J/10Hz system HALNA 10 has been developed.

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1053 nm10 J, 10 Hz, 10 ns< 5x TDL

Water

Oscillator Pre-Amp

Spatial filter - 1

Spatial filter - 2

Laser Output

LD modules

Nd:glass

Faraday rotatorExpander

Aperture

Slab amplifier headLD module for pumping

Slab amplifier : 8x10x240 mm 4 pass, Diamond geometry Faraday rotator for thermal effect compensation

Pre-AmpOscillator

Zig-zag slabAmplifier

Spatial filter

PHOTON IS OUR BUSINESS

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

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Left bank(Module 1)

Right bank(Module 2)

±

Pump module performance

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

Left bank (1,200 bars)Lasing !

100

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

conversion efficiency [%]

Pea

k po

wer

[kW

]

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

nsity

[a.u

.]

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

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Emission cross section 3.6 x 10-20

Fluorescence lifetime 350 µsThermal conductivity 1.02 W/mKThermal 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

□

□

□

Thermal analysis by LASCAD and THESLAC codes optimized slab dimension.

Physical properties.

Nd:HAP4Thermal conductivity:ă 1.02E+00 W/(mK)Coefficien of thermal expansion 8.50E-06 1/KElastic modulus 68800 N/mm^2Poisson's ratio 0.236Refractive Index 1.533Temperaturdependence of refractivindex dn/dT 1.80E-06 1/KAbsorption coefficient, 0.231 W/mm:Heat efficiency factor 0.3

LD module

Insulator

Height of glass

5°

Slab pumping geometry

Results of thermal effect analysisInsulator

Height of glassTeflon 10mm : ă=0.25W/m

Highly insulatedmaterial10mm�F

ă=0.025W/mwithout 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 -10022 4 90 97 6.223 6 90 100 7.724 10025 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. 12

Thermal modeling revealed optimum slab height for minimizing thermal lensing effects

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1.Temperature distribution

4.Thermal birefringence3.Wavefront distortion

Tempera tu re ( K

)

L os s ( % )

Slab height ( mm ) Slab thickness ( mm )

λ ( µ m )

-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 thickness ( mm )

Slab height ( mm )Slab thickness ( m

m )

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

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

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

0

5

10

15

0.0 0.1 0.2 0.3

Input [J]

Out

put [

J]

Pumping length Beam width 268mm 10mm 268mm �@8mm

14Output energy greater than 10 J is predicted .

Input energy vs. output energyBeam width vs. output energy

Input energy : 0.1 J

0

2

4

6

8

10

12

14

0 2 4 6 8 10

Beam width [mm]O

utpu

t [J]

Pumping length : 26.8 cmPumping energy : 48 J

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

0123456789

10

0 10 20 30 40 50 60

Pumping energy (J)

Out

put (

J)

15

0

2

4

6

8

10

12

0 20 40 60 80 100Input (mJ)

Out

put (

J)

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

Filling factor : 49%

2TDL

Near-field Far-field7.6mm

17mm

Near-field

Filling factor : 63%

0 20 40 60 80Time (ns)

Inte

nsity

(a.u

.)

26 ns (FWHM)

Far-field

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2TDL

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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Component Parameter Goal ResultOutput peak power 120 kW

2.5 kW/cm2

803 ±1nm, <4 nm(FWHM)

55%10

45%

Repetition rate 10 Hz 1 Hz 10 Hz10 J45%20%10%

Filling factor 50% 49% 63%

Pump intensity 2.59 kW/cm2

Pump diode

145 kW

< 5TDL

Slab amplifier

8.545%

10.6 J43.9%19.9%10.3%

80% (<5TDL)

Output energy 8.4 J

O – O efficiency 15.8%E – O efficiency 8.2%

Beam quality 70% (<5TDL)

Total system

Emission wavelength804.1nm,

3.4 nm(FWHM)E – O efficiency 52%

Small Signal Gain

Pumping efficiency

Extraction efficiency 34.9%

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

Yb: doped fiber oscillator

Nd: YLF regenerative amplifier (8mmφ, 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 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

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

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50

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

0

25

-50

-25

Pos

ition

in m

m

VerticalHorizontal

ILD ILD

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

Pump duration : 150 ~ 300 µsStored 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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Summary

� HALNA driver for IFE has been developed.

� The HALNA 10 has achieved 8.4 J at 10 Hz with beam quality of 2 xDLin 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.

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

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