Target Fabrication and Injection in Japan

- From Topics in 3rd TFIT -

T. NorimatsuPresented at US/Japan workshop on

Laser IFE, March 21-22, 2005General Atomics， San Diego, CA

Outline

• New concept– Impact ignition by M. Murakami– Magnetic focusing of injected target by R. Tsuji

• Target Fabrication– Current status at ILE by T. Norimatsu– Laser Lathe by Y. Kawamura

• Injection and tracking– At Gifu University by H. Yoshida– At Hiroshima University by T. Endo

1

A New Twist for IFE- Impact Ignition -

Contents of talk・What is Impact Ignition!?・Gain model・Design window・2D hydrodynamic simulation

M. Murakami　　　Institute of Laser Engineering, Osaka University

2

Advantages of Impact Ignition

(1) Simple Physics

(2) High Efficiency

(3) High Gain

(5) Low Cost

(4) No need for PW Laser

3

Gain Model

2 Rs

2 Rc

Impact-produced DT igniter

Compressed main DT fuel

ρs

ρc

v imp = (12Ts / 5mp)1/ 2 =1.1×108(cm /sec)

ELs =8πHs3Ts5mpηsρs

2 = 15 kJ ⋅ ηs−1 ρs100g / cm3⎛ ⎝ ⎜ ⎞

⎠ ⎟ −2

ELc = 3.3 ×1012α cρc

2/ 3Mc /ηc

Ed = ELc +ELs

Φ = Hc /(Hc +H0 )

G =ΦMcε 0 / Ed

Implosion velocity

Laser energy for igniter

Laser energy for compression

Total driver energy

Burn fraction

Energy gain

RT exp’t with shorter wavelength perturbation

Growth of the perturbations in the CHBr target is strongly suppressed in comparison with that in the CH target. S. Fujioka

(ILE. Osaka)

300 µm

1 ns

1 ns

Temporal evolution of growth factor

CH

CHBr

18-µm thick CHBrλp = 25 µm, a0 = 0.3 µm

25-µm thick CHλp = 20 µm, a0 = 0.2 µm

1

2

3

45678

10

2

3

45

Gro

wth

fact

or (a

rb. u

nits

)

2.52.01.51.00.50.0Time (ns)

4

Gain curves for Impact Ignition Targets

10

100

1000

10 100 1000

Total Driver Energy (kJ)

Ener

gy G

ain

αc = 3, ηc = 0.1, ηi = 0.1

200ρc (g / cm

3) = 100

300

ρi (g / cm3) = 100

200

300

9

2D Hydrodynamic Simulation

Isocontour map at a time shortly before the impact

Isocontour map at peak comp-ression shortly after the impact

11

Summary

• A totally new ignition scheme, ImpactIgnition, has been proposed.

• Impact Ignition has very attractive features.• Major breakthrouh expected in future

experiments is to demonstrate highimplosion velocities at relatively lowisentropes.

Pb Coating on Target for Magnetic Motion Control

Ryusuke Tsuji

Ibaraki University

3 rd Japan-US workshop18-19 Oct 2004 Osaka

Outline

• Development of orthogonal slit type pinholemotivation, principle

• Pb coating on target for magnetic controlsuperconductivity sustaining timeflight distancemagnetic lense

Pb coating of target• Au reflective coating is analysed

( e.x. R. Petzoldt et.al, Nucl. Fusion 42(2002)1351)

↓

• Pb is used in LiPb blanket• Pb has superconductivity (Tc=7.2K)• Target injection system accompanies cryogenic (T=18-

19K) apparatus↓

• Pb coated target cooled to 4.2K is superconductor

Magnetic Control (Magnetic Lense)

• Lense

• Magnetic Lense is considerd as static feedback

Monochromatic light focuses automatically (no dynamic control)

Trajectory of target of same velocity focuses automatically

S

N

Principles of simple magnetic lense

ya

f c

• Mometum transfer P(y)• Fdt=k/(a-y0)d × b/V= mV(y/c)+mV(y/f)

b

a

P(y)

y

Pb coating of target (Cont.)

• Target ParametersConventional spherical direct driveRadius 2[mm]Pb coating thickness 0.05[μm]

( Skin depth of Pb is 0.04 [μm] by A. C. Rose-Innesand E. H. Rhoderick, “Introduction to Superconductity, 2 nd ed.” Pergamon 1978)

Initial temperature 4.2[K] Tc=7.2[K]

S.C. sustaining time

Allowable heat Qmax from s.c.(4.2K) to n.c.(7.2K)

• Qmax = mCΔT = 4πr2 Δrρ∫4.2 7.2 C(T)dT

( C(T)=βT3＋γT, β, γ, M. Horowitz et.al. PR88(1952)1182 )= 1.914×10-7 [J]

m: Mass of Pb layer C: Specific heat of PbΔT: Temperature increase (4.2K to 7.2K) r: Radius of target Δr: Thickness of Pb layerρ: Density of Pb

S.C. sustaining time (Cont.)

• t in 10 m long injection system (4.2K) with holeinjection point : endinjection speed 100 [m/s]injection hole with 2[cm] radius open

reactorinjection system

S.C. sustaining time (Cont.)

0.5×Qmax = (1-R) σ Ｔ4 πr2 ∫0 t F(t)dt

=0.1× 2.3226× 0.2513×∫0 t F(t)dt

Heat is transported from the holeF(t) =πa2 / (2π(L-Vt)2)T=800, V=100, L=10, a=radius of the hole

t = 0.09425 [sec] ( R = 0.9 case)D =9.425[m]

Enough sustaining time (distance) is obtained

Summary

• Orthogonal slit type pinhole is under development (to be presented in 4 th Japan-US Seminar)

• Pb coating on target is proposed. Target with Pb coating at 4.2 K becomes superconductor. It enables us to control motion of the target in the injector by the magnetic field

• Static magnetic lense system for target control is proposed. If the release point and the velocity of the target are fixed (even though the direction varies), then we can expect that the magnetic lensesystem can focus s.c. target at fixed point

ILE, Osaka

Fabrication of FI Target for FIREX and Fuel Loading for Future Reactor

T. Norimatsu

Institute of Laser Engineering, Osaka UniversityPresented at Japan/US workshop on IFE Target Fabrication, Injection and Tracking

ILE, Osaka

Outline

• Introduction– Program,

• Status of Target Fabrication in Japan– Collaborative work– Activities at ILE

• Fueling system for Reactor– Thermal cavitation technique – Pneumatic/coil gun hybrid system,– Estimation for operation power

ILE, Osaka

The FIREX-I project has been started under collaboration with National Institute for Fusion Science.

FY 02

FY 03

FY 04

FY05

FY 06

FY 07

FY 08

FY 09

FY 10

FY 11

FY 12

FY 13

FY 14

FIREX-I (Heating of DT plasma to 5keV)

FIREX-II (Demonstration of ignirion and burn)

10kJ/10ps Upgrade to 50kJ1 PW 1 kJ/1 ps

Construction of compression laser

Upgrade to 50kJ

Gekko XII 10 kJ/2ns/0.53um

Fuel capsule with cone

(CoLab)

(CoLab)

(ILE)

(ILE)

(ILE)

(NIFS)

(CoLab)

(NIFS)

Laser for heating

Laser for compression

Construction of heating laser

Implosion experiment of cryogenic target

D 2 D T D T D T

Licence work

Cryogenic plane target

Demo of cryogenic foam method

Characterization of solid layer

D EF

D EFCryostat for implosion Exp. 1

Cryostat for implosion Exp. 2

Low density foam

トリチウム回収装置上部冷凍機

下部冷凍機

トリチウム

供給装置

Diameter 2mm Solid DT 100um DT 60 mCi

ILE, Osaka

Fabrication of transparent foam shell for FIREX-I, low density foam shell for FIREX- II and LiPb cone for reactor are critical issues.

• FIREX-I(Heating to 5keV)– Fabrication of Transparent

foam shell to allow characterization

– Machining of fragile foam shell

• FIREX-II(Ignition and burn)– Low density foam

• Reactor(Gain >170)– Mass production of LiPb cone– Fuel loading

3 mm

5 mm

2 mm

0.8 mm

0.5 mm

For FIR EX -I

For FIR EX -II

3.46 mm

5 mm

8.5 mm

5 m

m

3.5 mm

15o

1.06 mm

24.5oFor R eactor

ILE, Osaka

We are going to demonstrate RF foam method with NIFS.

For FIREX-IThe first step of Cryogenic foam method is to evaluate the quality of ice

•Diameter：500µm•Fuel layer：～20µm•With glass tube•D2 or DT fuel

Liquid phase

Freezing -15 % in volume

Partially dry foam?

Porus ice?

How much DT sublimates through the feeder / vent hole?

?

ILE, Osaka

Specification of Cryogenic Target and Apparatus are;

Cryogenic Target

• Diameter：500µm• Fuel layer：～20µm• With glass tube• D2 or DT fuel

Apparatus

• 4K-GM Cry cooler• Minimum temperature：<10K• With four view ports• Prevent target vibration：<several µm

For FIREX-I

～20µm<1µm

500µm

Glass tube

ILE, Osaka

Apparatus to demonstrate foam method is almost fabricated. Cooling test will start soon at NIFS.

Target Chamber

4K GM Cry cooler• 1st Stage: 45 W @50K• 2nd Stage: 1.5 W @4.2K

Welded Bellows

Target

ILE, Osaka

Target Fabrication at ILE

• For central ignition– Fabrication of polyimide shell by emulsion process

• For fast ignition– Foam shell

• PMMA, TMPT foam• RF foam

– Parabroide Cone• Diamond lathe• Laser lathe (To be reported by Y. Kawamura, Fukuoka

Institute of technology)

ILE, Osaka

If the foam is PMMA, we can make required foam shell with gas barrier and reentrant cone.

OW2

1st orifice

2nd orifice

W1

XYZ stage(for 1st orifice)

3rd orifice

XY stage(for 3rd orifice) Gas barrier coating by

interfacial polycondensation

• Fuel shell– Emulsion method followed

by interfacial polycondensation method

– Hole boring on frozen foam shell

• Cone– Electro plating on

removable mandrel machined with diamond lathe

ILE, Osaka

Hole for cone could be bored into frozen foam with normal drill. Large scattering, however, disables optical characterization of cryogenic layer.

Ice

Freeze dry of foam shell

X-ray image SEM image of hole side

ILE, Osaka

We are now applying previous method 1)

for shell process

Frin

ge v

isib

ility

Foam thickness ( µm)

0.1

1

0 50 100 150 200

3%1.5%

0.9%

0.3%

Previous foamsOptical image of a 220 µm diameter foam ball in the air. TMPT 3%, AIBN 3%, Thermally initiated polymerization.

A B

255

0 White

Black

Fringe visibiliy = B/A

1) M. Takagi, T. Norimatsu, Y. Izawa and S. NakaiMat. Res. Soc. Symp. Proc. 372 199-202 (1995)

ILE, Osaka

We have started fabrication of Resorcinol -Formaldehyde (RF) foam 1) that is transparent due to its fine structure.

RF foam shells with the density ranging 150-250 mg/cc are successfully fabricated but further effort is necessary to improve the uniformity.

•In the case of RF foam, freezing method can not be used to hold the shell during drilling because phase separation takes place, which increases the scattering of light.

Excimer laser etching

1) Stephen M. Lambert , George E. Overturf Journal of Applied Polymer Science, Vol.65,2111-2122(1997)

ILE, Osaka

To make a hole on fragile RF foam shell with gas barrier 1), we used excimer laser etching followed by punching.

ArF laser

Cushion

Mask

Vacuum chuck

Punch out

0

5

10

15

20

25

30

0.01 0.100 1.000

Fluence [J/cm2]

Etch

Rat

e [u

m/1

00pu

lse]

PS

RF-foam [120mg/cc]

GDP

1) Shells were presented by GA.

ILE, Osaka

Spiky structure is attributed to shrinkage of RF foam by UV irradiation.

• When the density of foam is about 1, etched surface was flat. Irradiation of UV light induces shrinkage of RF foam.

ρ=1.02 g/cc, etched surface was flat. ρ=250 mg/cc, Shortly after beginning of etching.Cracks appeared on the etched surface.

ILE, Osaka

We found promising method to make a hole on RF foam.

300 µm

30 µm10 µm

Laser Machining in air Laser Machining in water

• Laser machining in air make deformation of nearby foam, resulting large opening. Machining in water can make sharp cut.

ILE, Osaka

Fabrication of parabolic cone as a focusing device.• In a future power plant, some focusing mechanism is necessary to heat the

compressed core up to the ignition temperature because of diffraction limit of the final optics.

• This paraboloid mirror design enables 80% of laser energy in 300 µm spot focused on the 40 µm diameter spot with one bounce.

100

0

100

0 100 200 300 400 500

40 µm

10 µm

Focusing point300 µm

(200 nm Au coating)

Estimated beam waist 300 µm

100µm10µm

40µm

Paraboloid mirror

Focusing spot

Target Injector

Compression beam

Ignition beam

Final optics

30 m

ILE, Osaka

To test the focusing effect, paraboloid cone was fabricated with diamond lathe.

0

1 0 0

2 0 0

3 0 0

4 0 0

5 0 0

6 0 0

7 0 0

0 50 100 150 200 250 300 350

Y = M0 + M1 * x + . . . M8 * x 8 + M 9 * x 9

7 7 5 .5 4M 0

-8 .2 1 1 4M 1

0 .0 2 2 1 4 8M 2

0 .9 9 8 8 9R

Distance (µm)

Dis

tanc

e (µ

m)

After edge detection, inner surface finish is calculated to be 2µm in RMS.

ILE, Osaka

Summary

• Mass production of the FI target strongly depends on the successof foam method. If we could well understand the foam method so that we can skip individual optical characterization, transparent foam is no longer necessary and mass production of shells, machining and fuel loading are in our scope.

• Remaining issue in FI target is;– Demonstration of foam method using transparent foam shell,

which will start soon with collaboration of ILE and NIFS.– Mass production of cone

ILE, Osaka

Summary (continued)

• Concept of fuel loading by thermal cavitation method is proposedfor batch process in future power plant.

– Remaining issue; Ice quality, Sublimation during cooling

• Preliminary estimation of driving power for fueling system was 1MW / 2 Hz unit, which seems acceptable.

Thank you for your attention

Possibility of the application of the five axis laser micromachining systemto the ICF target fabrication

Yoshiyuki Kawamura Fukuoka Institute of Technology

3rd Japan US Work shop on target fabrication, Oct.18.04

Experimental setup for five axis laser micromachining

TTL board

5 axis stage

4th harmonic of Q switched Nd-YAG laser (266nm, 10ns, 0.1mJ, 30Hz)

Five axis stage

Five axis stage

Laser beam

Ｘ axisＺ axis

ωaxis

Θ axis

Ｙ axis

Fabrication of a micro sphere using 3 axis (ω, x, z) laser micro machining

Diameter: ２６０μｍ

Alignment between these 3 axes is essential for precision machining

Micro windmill

Micro windmill of diameter 780μm that have ten blades.

Enlarged view of blades.

Windmill & Bearing

Micro globe (polyimide)

Micro globe with the diameter of 1 mm.

One cent coin and micro globe.

ILE have the plane to focus the ignition laser into the center of the target using a micro parabolic mirror

100 0 1000

100

200

300

400

500

40 µm

10 µm Focusing point

300 µm

(200 nm Au coating)

3 mm

5 mm

Li17Pb83

2 mm

40 µm

Estimated beam waist 300 µm

100µm10µm

40µm

Paraboloid mirror

Focusing spot

by Prof. Norimatu (ILE)

To make parabolic cone, aluminum mandrel was machined with laser lathe.

y = -0 .028x2 + 6 .9391x - 206 .18

0

50

100

150

200

250

0 50 100 150 200 250

X（μm）

Y（μ

m）

試料Eの実際加工ライン

二次近似曲線

To check the focusability, concave mirror was copied with epoxy resin.

LD

Milky liquid

CCD

フィルム

エポキシ系樹脂

放物面形状試料WorkEpoxy resin

Film

Parabolic micro cupper mold for the electroforming of the micro parabolic mirror

( surface roughness)

2 um

Boundary between the background shows that the surface roughness is less than 1um

Conclusions and future prospects

Fabrication of the advanced ICF target fabrication is one of the application of the five axis laser micromachining system. Micro cupper parabolic mold has been successfully fabricated using two axis laser micromachining.Machining error of the parabolic mold should be improved to be as small as 1μm.

Experimental setup of coil gun

Coil gun

×6

Length 14mmOD 90mmID 22mm30μH

Sleeve

Delay pulsar

Trigger

High voltagepower supply0-250 V

Oscilloscope

75×15φ(Al)

Stopper

Photodetector

LD

Nd:YAG laser(Minilite -Ⅱ)

CCDcamera Shunt Shunt Shunt

Trigger in

Coil gunLength 104 mmNumber of phases 3Number of barrel coils 6

BarrelLength 14 mmOuter diameter (OD) 88 mmInner diameter (ID) 20 mmNumber of turns 12Self inductance 30 μHCapacitance 1980 μFCharge voltage ≦ 300 V

SleeveLength 75 mmOuter diameter 15 mmThickness 1 mmMass 8.86 gMaterial Aluminum

Gifu Univ.

Maximum acceleration was 580G, which is sufficient to accelerate a target to 300m/s in 20m.

0

2

4

6

8

10

200 400 600 800 1000 1200

Time delay t C (ms)

Sle

eve

velo

city

vs

(m/s

)

↑tB

Vb = 250 Vt B = 200 μsmS = 8.86 gzinit = 12 mmTa = 300 KP = 106 Pa

Sim.

Expt.

μ

0.1

1

10

100

10 100 1000

Condenser bank voltage V b (V)

Sim. Expt.

580G

t B = 200 mst C = 600 μsms = 8.86 gzinit = 12 mmTa = 300 KP = 106 Pa

Gifu Univ.

(a)

(b)

100mm

TargetdetectorStopper

(a) The coil gun before target shot and (b) the irradiated target by Nd:YAG laser.

Correlational detection by matched filter

Opt. Wedge

He-Ne laserM

MFourier conv. lens f=5000

BEMatched filter

CCD camera

Inv. Fourier conv. Lens f=5001460 5032 502 502

3572

5.8mm

2mm

cone-target 1mm

Gifu Univ.

Accuracy of detection was 140 µm at 5 m apart.

Intensity (a.u.)

xout (mm)0

0.31

Inte

nsity

(a.u

.)

y out(

mm

)0

-4.0

-3.0

-2.0

-1.0

0.0

1.0

2.0

3.0

4.0

-4.0 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 4.0

σ= 0.14mm

Target position x (mm)

Detected position xout×10 (mm)

Gifu Univ.

The accuracy will be improved withuniform irradiation,f-number,linearity of film to make filter.

Measurement of tumbling of Sabot in Barrel

Tumbling is measured by trajectory of reflected LD beam on screen

Off-axis position, r=2.5mm Coaxial position, r=0mm

Tumbling angle is smallcomparing with 3.9deg defined by clearance in barrel

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0 0.5 1 1.5 2 2.5 3

Time (ms)

Tum

blin

g A

ngle

(°)

Coaxial position, r=0mm

Target container designφ6.213φ

2

14

9

φ6.213φ

2

14

φ7.2

6

φ6.213φ

2

14

φ6.213φ

2

14

9

φ6.7

6

Four configurations of target container are tested

φ6.213φ

2

14

φ6.213φ

2

14

φ7.2

6

φ6.213φ

2

14

9

(xav,yav) = (5.9,-5.5)σr = 27.3 mm

(xav,yav) = (9.8,-1.0)σr = 32.1 mm

(xav,yav) = (5.5,-5.9)σr = 31.8 mm

(xav,yav) = (9.0,-4.8)σr = 23.1 mm

φ6.213φ

2

14

9

φ6.7

6

����������� ������������������������������������������������������������������������������������������� !" #��$%%&

%

'���()(���*+&,

9

4 L. D. Landau, and E. M. Lifshitz, Fluid Mechanics, 2nd ed.,

Butterworth-Heinemann, Oxford, 1987, Sec. 105.

4

*γ�:������()���������7�9,

1��"����(�������)��:�������)���� &/�������(��

�6�:�����(�����)��τevac�6����������"����(�������������6��������

�������0��������������������(���pmax��6�����������"����(�����

���������������0�(0����3

<�����0����������"����(���������������������0�)���������������������0������0������3�4�:�������6��������"����(������������������)�����0�)���6����������������:��������)����������0����"����(���������3

<���������)��(0�����(0���������0�����(����0������������0�

7/�������(��

;���0�������'��(0� <���������'��(0�

����(�����������:���������

<��������"/��������;��(����

���������

������� �������

������������������

� �������������

���������

�������

��������������� �������

!"���#���������$

������������

# �������

#% #� #&

#'

#(

#)

��������(�����������0�������)��(0��:������60���������������B���)���

>;���0�������)��(0�

A7�*9":��,���A��(()����-��������=�7�)����-������������A��(()=�>�)�

���������

���������

� �����������

��

������� �������

?;���0�������)��(0�

��������(�����������0�������)��(0��:������60���������������B���)���

!

%!%�))�* $%���,����������$�)

)

3&�))

��C�$3$ ��

$3 �)

)

$3 �))

'������0=�/(����������0����0�)���*�������6��0��B�)����0�������,

$ #7�))�*�:���(����:��������6(00������,

#

First result on rifling, spin was insufficient for stabilizing the sabot.

())���

$%

�����(������������(����6���(�����0��������

�������"����(�������)���������������������"��������

���������(����(���������0����)�����3�

�

��������(�����������0�������)��(0��6����������

����������60����66�����������������B���)���3�

�

<��0�)��������(0������:���������������)�����k�������������������:�����������0��������������������

������������0�������6������:������(��%3!�*�0)����������,3