ILE Osaka

Concept of KOYO-F and Formation of Aerosols and

Micro Particles

T. NorimatsuPresented at TITAN workshop on

MFE/IFE Common ResearchUCSD, Feb. 10-11, 2009

ILE Osaka

Common task on TITAN

• To construct system integration model on tritium and thermo fluid system

• Identify key issues • & design priorities• Identify baseline design(s) • - FFHR, ARIES• - KOYO• Assess concept attractiveness• & feasibility• Perform analysis of key issues

Goal

Now….

ILE Osaka

Outline

• Introduction of KOYO-F and the critical issues

• Researches on chamber clearance– Code development (by H. Furukawa, ILT)

• Experimental check 1 (by T. Norimatsu)• Experimental simulation with laser ablation

(to be presented by K. A. Tanaka)

– Experimental simulation on hydrodynamic instabilities on ablation by alpha particles(by Y. Shimada, ILT)

ILE Osaka

Conceptual laser fusion reactor KOYO-F based on fast ignition

Electrical output power 1200 MW

• Target gain 167• Fusion yield

200MJ/shot• Laser 1.2 MJ x

16Hz,12% • 4 modular reactors with

32 compression beamsand 1 ignition beam

• System efficiency 40%

ILE Osaka

Reactor with cascade flow of liquid LiPb

• Coolant Li17Pb83

• Chamber/Blanket wall Ferrite / SiC/SiC

• Fusion yield 200 MJ x 4 Hz

• Thermal output 916 MW• Chamber size (inner/outer/high)

3m / 5m/14m• pulse load 0.3 MJ/m2

• peak load 2 x 1012 W/m2

• Average thermal load 1.2 MW/m2

• Neutron load 5.6 MW/m2

• Solid angle of beam ports < 5%• TBR 1.3

ILE Osaka

KOYO-F with 32 beams for compression and one heating

beam• Vertically off-set

irradiation

• Cascade surface flow with mixing channel

• SiC panels coated with wetable metal

• Tilted first panel to make no stagnation point of ablated vapor

• Compact rotary shutters with 3 synchronized disks

Chamber

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The surface flow is mixed with inner cold flow step by step to reduce the surface

temperature

Chamber

If the surface flow is a laminar flow, vapor pressure is too high to reach designated pressure of 5-10 Pa.

ILE Osaka

Thermal flow of KOYO-F

SGTurbin

500℃

300℃300℃

50MW

210MW

70MW

70MW

240MW

80MW

80MW

500℃

F2+F3 (80cm)12.84 ton/s

Average flow 7.8 cm/s

F１ (20cm)8.56 ton/s

Average flow 24.3 cm/s

Flow rate 21.4 ton /s

904MW

Watercycle

Chamber

LiPb cycle

Chamber

t=0.5 oC/shot 　　　　 t=1.3 oC/shot

Thermal shock in closed blanket p=0.1MPa

ILE Osaka

Critical issues in chamber 1(from J-US WS on reactor 2007)

• Probability for direct exposure of the same place <1/103 – 1/104

– If we assume maintenance period of 2 years and acceptable erosion of 3-mm-thick, the probability for direct exposure of the same place with particles must be less than 1/104.

– Improve flow control, material selection, chamber radius

• Protection of beam ports– Our first plan was to keep the surface temperature less than

surrounding area to enhance the condensation. But this would not work because of the small temperature dependence of condensation.

– Porous metal saturated with liquid LiPb– Magnetic field

Dry surfaceLiquid LiPb

Dr Kunugi demonstrated a stable flow >3 mm using water

Dr. Kajimura showed protection of the beam port by a 1T magnetic field.

ILE Osaka

Critical issues in chamber 2 (from J-US WS on reactor 2007)

• Chamber clearance– Formation of aerosols– Large ( ~10 m) particles due to RT instabilities and related

secondary particles

• Tritium diffusion through the heat cycle– To be solved during TITAN

ILE Osaka

Outline

• Introduction of KOYO-F and the critical issues

• Researches on chamber clearance– Code development (by H. Furukawa, ILT)

• Experimental check 1 (by T. Norimatsu, ILE)• Experimental simulation with laser ablation

(to be presented by K. A. Tanaka, Osaka U.)

– Experimental simulation on hydrodynamic instabilities on ablation by alpha particles(by Y. Shimada, ILT)

ILE Osaka

We estimated the ablation process using ACORE. Stopping power in ionized vapor

was calculated.

Atomic Process Code

Ionization Degree, Population, Energy Level

Stopping Power Code EOS Code Emissivity and Opacity Code

Stopping power Ionization DegreePressure, Specifiic heat

Emissivity, Opacity

ACORE (Ablation COde for REactor)

0

4

8

12

Number Density

(cm-3)1014

1018

1022

Temperature (eV)

10

1

0.1

0.01

Z*

Ionization rate of Pb

Ziegler’s model

dE

dxni Inl

l

n Pnl

Z0e2

Inl

2

Gv

vnl

Present model

G V 3/2

V 2 2

31 ln 2.7 V

V 0.206

4 2 20

02 2

4 4e e

e e e

e Z n n edE hK

dx m v n v m

0

100

200

300

400

500

0

10

20

30

40

50

0 2 4 6 8 10

= s , T=300 K

Ziegler

Present

Z*W

( M

eVcm

2 / g

)

Z* (E

)

Energy (MeV)

alpha

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ACONPL (Ablation and CONdensation of a PLume)

p 11

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Treatment of Phase Transition in ACONPL

p 12

○Equation of Motion of Ablation Surface ( The boundary of liquid and neutral gas or plasma )

Tv Tl xv t Lv : Latent Heat of Vaporization

Tv : Temperature of Ablation Surface

○Equation of Energy in Liquid

Ul x,t l Cl x,T x,t T0

T t dTl x,t

Ul

crtl Cl x,T T0

Tvap dT Lv

Tvap : Vaporization TemperatureIf Ul >Ul

crt, Peeling will occur.

xv x xmax

Qp : Heat quantity due to 　　 charged particles

Qx : Heat quantity due to 　　 absorption of X-ray

t

x v t kBTv /m i exp m i Lv / kBTv

l

l

T x, t x

xxv

Lvt

xv t

U l x, t t

T x, t Q p x, t QX x, t Qrad x, t

ILE Osaka

Treatment of Hydro Dynamics in ACONPL

○ 1 Fluid and 2 Temperature Model, Lagrange Scheme

Pnv : numerical viscosity

1

3 exp 1

B

q 2

TsT

3/2

Tc q

Vaporization Temperature ( Condensation Temperature )

q : Latent heat of Vaporization（ Kelvin)

d x,t dt

x,t v x,t x,t dvx,t

dt Pe x,t Pi x,t Pnv x,t

x, t cve Te x, t t

qe x, t Te Ti Pthe x,t v x, t

QP x, t QX x, t Qrad x, t

x, t cvi T i x, t t

qi x, t Te T i Pthi x, t Pnv x, t v x, t

x, t cvi 2

3q Ti x, t

3 dd t

4-th term of right hand side is temperature increment due to phase transition from gas to liquid (clusterization).

ILE Osaka

p 16

Tc q

1

3 exp 1

B

q 2

TsT

3/2

q : Latent Heat of Vaporization（ Kelvin)

◯Two-Phase Mixture Effects

Temperature of Clusters

Condensation Rate

Rate of Nucleation

Cluster Growth

Super Cooling Parameter Reference 　　B. S. Luk’yanchuk, S. I. Anisimov et. al.,

SPIE 3618 (1999) 434-452.

y x, t x, t g x, t

x, t T i x, t T x, t / T i x,t

0 2

0

, , 11 , exp

, ,nuc

d x t x t Ty x t

d t T x t x t

2 / 3 1/ 30

0

, ,1 , 1 expg

d g x t x t qg T y x t g

d t T

, 2 , , ,1 21 , 1 , ,

3 , 3

dT x t T x t d x t d y x ty x t y x t q T x t

d t x t d t d t

Condensation of a Plume

◯ Condensation Temperature

ILE Osaka

To check the code, 10m thick Pb membrane was heated and aerosols

were captured on a witness plate.

ILE Osaka

There is geometrical effect on the diameter of particles.

0

100

200

300

400

500

0 5 10 15 20 25 30 35

Diameters of particles on witness plate and rod

on Plateon Rod

Distance (mm)

Geometrical effect

The minimum diameter givesaerosol diameter.Model for large particles

ILE Osaka

Diameter of particles agreed with simulation result.

Particles on continuous membrane

The continuous membrane was formed with leading, super-cooled plume.

ILE Osaka

Density, Temperature and velocity profile of ablated material.

102

103

104

105

106

107

108

109

0.0 0.5 1.0 1.5 2.0

alfaalfa (debri)deuteriumtritiumprotonherium3

Inte

nsi

ty (

W/c

m2

)

Time (s)

ILE Osaka

Density, Temperature and velocity profile of ablated material.

102

103

104

105

106

107

108

109

0.0 0.5 1.0 1.5 2.0

alfaalfa (debri)deuteriumtritiumprotonherium3

Inte

nsi

ty (

W/c

m2

)

Time (s)1016

1017

1018

1019

1020

1021

1022

1023

0

1 104

2 104

3 104

4 104

-1 0 1 2 3 4 5

Time = 2000 ns

Number Density

Te

v (m/s)

x (cm)

ILE Osaka

Number density at the next target injection is estimated to be 107/cm3.

107

108

109

1010

1011

1012

1013

1014

1015

0

500

1000

1500

2000

-1 0 1 2 3 4 5

Time = 2000 ns

nc

Te

x (cm)

If interaction with opposite plume, clusters in this region will disappear after collisions with the opposite wall.

Clusters in this region expand to chamber volume before next target injection.

The resulting nc at the next target injection is;

50 m

8 X 106 /cm3

ILE Osaka

Influence of aerosols on target injection can be ignored.

Chamber center Wall

Nc=107 cm3

3m

Total mass of aerosols in the column

1.06 x 10-4 g

Target mass

Aerosol mass = 2 x 10-4

(0.4 m in the thickness of deposition layer)

We can ignore the influence on target trajectory.

ILE Osaka

Future work

• Influence of ions as “seeds” for clusters

• In this simulation, clusters move with fluid.– PIC code

• Interaction with opposite plume– Stagnation at the center– Condensation on the opposite wall

ILE Osaka

Outline

• Introduction of KOYO-F and the critical issues

• Researches on chamber clearance– Code development (by H. Furukawa, ILT)

• Experimental check 1 (by T. Norimatsu)• Experimental simulation with laser ablation

(to be presented by K. A. Tanaka)

– Experimental simulation on hydrodynamic instabilities on ablation by alpha particles(by Y. Shimada, ILT)

ILE Osaka

To understand the ablation phenomena by alpha particles, we used laser backlighting.

• To know the influence of internal hot zone due to Bragg’s peak, we used back-light heating of Pb membrane.

• Electric discharge was used to check simulation code for aerosol formation.

Energy density Pulse width Heating process PurposeKOYO-F 0.35 MJ/m2 0.05s Volumetric

Laser 0.15 MJ/m2 0.015 s Surface RT instabilityDischarge 1.5 MJ/m2 100 s Volumetric Check simulation

Particle loads Energy deposition

Volumetric heatingBragg’s peak

ILE Osaka

Experimental setup. Laser-scattering measurement was used to observe flying

situation of metal

Punch out laser

50 mmProbe laser

2×10-4 torr

Nd:YAG laser

Intensity: 0.5 – 1 GW/cm2 Spot size : 700 - 800 mφ Pulse duration : 15 ns

Cylindricallens

CCD camera

Scatteredlights

Target(glass plate with coated tin or lead)

27

Linefocus

9 s 12 s15 s

Laser

Glass plate

Dot targetDiameter： 500 m(smaller than laser spot size)

ILE Osaka

Spouted gas and small particles, and large particles were detected at 10-mm

away from glass plate

10 mm

2s 4s 6s 8s 10s 12s

500m

6s

800m

9s 12s

Averaged density2×1018 (cm-3)

28

15s

Diameter~10 μm

Gases

Gases small particles

Large particles

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RT instability and break up would make larger( 3m), slow (100-500m/s) particles.

Dot target

Laser

High speedgases

RT Instability

Gas,

clusters

Smallparticles

Largeparticles

High density

columns

Glass plate

Depend on thickness of targetetc.

λ

few joules energy It may cause secondary ablation of panel 29

bigparticles

3km/s

0.5km/s

ILE Osaka

Stagnation at the center needs more analysis

Laser back lighting Electric discharge

cos cosn

Volumetric heatingPlaner heating

Tilted first panel concept may reduce the stagnation to 1/5 of cylinder case.

Recently we started simulation on collisions of plumes.Preliminary result indicates condensation and formation of droplets are not critical because the kinetic energy of leading plume is much higher than latent heat of condensation.

80% 20%

(At end of after glow)

ILE Osaka

Summary

• Aerosols and particles– In KOYO-F, the diameter of aerosols 100 – 200 nm – No influence on target trajectory and performance

if we ignore the interaction with opposite plume.

• Hydrodynamic process must be considered to discuss formation of particles.

• Remaining issue: • Secondary particles• More detailed estimation of stagnation at the chamber

center31

ILE Osaka

Cooled Yb:YAG ceramic laser will be used for both compression and ignition

beams.

Lasers

60kJ x 8 beams

FiberOscillator

Pre-Amplifier(~ kJ, NIR) Main-Amplifier

(~ MJ, NIR)

3rd Harmonics

2nd Harmonics PulseCompressor

compression Laser(1.1MJ, blue, ns)

Heating Laser(0.1MJ, NIR, ps)

OPCPA

PulseStretcher

Mode-lockOscillator

Compression laser 1.1 MJ, 12%Heating laser 0.1 MJ, 5%

ILE Osaka

Target for KOYO-F

Fuel shell

DT(gas) (<0.01mg/cc) 1,500 ｍDT(Solid) (250mg/cc+10mg/cc Foam) 300 ｍGas barrier (CHO, 1.07g/cc) 2 ｍCH foam insulator (250mg/cc) 150 ｍOuter diameter 1,952 ｍMas of fuel 2.57mg

Total Mas of shell 4.45mg

Basic specification Compression laser 1.1 MJ

Heating laser 70kJ Gain 165 Fusion yield 200MJ

Cone Material Li17Pb83 Length 11mm Diameter 5.4 mm Mas 520 mg

3.9 mm

15o9 mm

11 mm

5.4 mm3 mm4.0 mm

Plastic coating

Prabolic mirror

Foam insulator Solid DT+Foam

Tritium burn ratio 23%