Peripheral Elements and Technology Associated with Pulsed Power Inertial Fusion： Part 21

 Koichi KASUYA2

Department of Energy Sciences, Interdisciplinary Graduate School ofScience and Engineering, Tokyo Institute of Technology,

4259 Nagatsuta, Midori-ku, Yokohama, Kanagawa, Japan 226-8502

1 Supported by the Ministry of Education, Science, Culture and Sports in Japan,

the Japan Society for the Promotion of Sciences, Tokyo Institute of Technology,

Sandia National Laboratories, Institute of Optoelectronics, MUT,

and Institute of Laser Engineering, Osaka University.

2 Collaborations with A.Kasamatsu, Y.Kinoshita, T.Kamiya (TITech),

T.Norimatsu, Y.Kozaki ,T.Yamanaka, S.Nakai (Osaka Univ.),

T.Renk, C.Olson (SNL), W.Mroz, A.Prokopiuk (MUT).

Presented at the 2nd RCM of the IAEA CRP on "Elements of Power Plant Design for Inertial Fusion Energy", RC-845-F1.30.08, 21 May 2001, Vienna, Austria

Abstract 

Various candidate materials were collected from many sources. They were irradiated with intense proton beams at Tokyo Institute of Technology (TITech), with intense nitrogen beams at Sandia National Laboratories (SNL), Albuquerque, and with short pulse UV laser at IOE-MUT, Warsaw. A series of preparatory numerical calculations of x-ray ablations was performed at TITech, which results were compared with the experimental ones. Our aims were to supply necessary data for the future design of inertial fusion reactor chambers. One of the key issues in this field was the ablation thickness of the various chamber wall materials with intense beams under typical inertial fusion reactions. We measured the ablation thickness of various samples, and we also observed the surface conditions of the samples before and after the irradiations with a microscope, an x-ray luminescence composition analyzer and 3D-surface profiler.  

Keywords: Inertial fusion, Reactor Chamber Database, Wall Materials, Surface Ablation with Ions, X-rays and UV Laser Light

TITech, DOES, Kasuya Lab.

CONTENTS:

1. Introduction

2. Sample Targets Collected for Beam Exposure

3. Ablation Experiments with Intense Pulsed Ion Beams

3.1. Ablation Experiments with Proton Beams

3.2. Ablation Experiments with Nitrogen Beams

4. Ablation Estimation with Intense X-ray

4.1. Calculation of Ablated Thickness

4.2. Ablation Experiments with X-ray

5.Ablation Experiments with UV Laser Light

6. Summary

Sample Targets Collected for Beam Exposure: 1-a/LiPb/ 16x19x1/ ILE/ Manufactured in Ar environment, Melting Temperature of 233C (Peak)/ 1-b/SiC/ 18x23x1 etc./ ILE/ 4-b/Carbon G650S/ 30diax5t(1)/ TITech/ Product of Nilaco Co. Ltd./6-a/SiC/ 100diax2/ Tokaikonetsu/ Product of Tokaikonetsu, Normal Pressure Baked, Both Surface Ground/6-b/SiC-Si/ 235x235x5/ Tokaikonetsu/ Product of Tokaikonetsu, RS420/ 6-c/Al2O3/ 135x125x5/ Tokaikonetsu/ SSA-M, Product of

Nihonkagakutohgyoh, Normal Pressure Baked/

MMAARRXX

GGEENNEERRAATTOORR

11..4455MMVV

3322..66kkJJ

((MMAAXX))

PPFFLL

33ΩΩ 114400nnss

TTLL

33ΩΩ 114400nnss

DDIIOODDEE

MMAAGG

CCOONNTTRROOLL

MMAAIINN

CCOONNTTRROOLL

22110000mmmm 33000000mmmm 33000000mmmm 775500mmmm

TTAARRGGEETT

CCHHAAMMBBEERR

Fig. Schematic Diagram of Target Ablation with Intense Proton Beam

TITech, 　 DOES, Kasuya Lab

TARGET CHAMBER

DIODE

TARGET

WINDOW ION BEAM

Fig. Configuration of Focused Proton Beams on Target

TITechDOESKasuya Lab.

15

17

19

21

23

25

27

29

31

6 7 8 9 10 11

E n e rg y D e n s i ty ( J /c m 2 )

Ablat

ed T

hick

ness

(μm

)

F ig . A b la t io n T h ic k n e s s v s . P ro to n D o s e (S iC , L iP b a n d C f ro m To p to B o tto m ) .

TITechDOESKasuya Lab.

Fig. Laser Microscope for Surface Ablation Analysis

(Keyence VK-8550 System)

2D Microscope Image of SiC, irradiated with N2 Dose of 3.9J/cm2.

3D Microscope Image of SiC, irradiated with N2 Dose of 3.9J/cm2.

X-ray Luminescence Spectrometer for Surface Composition Analysis (Philips PW2404 System)

0 1 2 3 40

20

40

60

80

100

Dose of Nitrogen Ion [J/cm2]

Si

[Ato

mic

Num

ber

%]

C [

Ato

mic

Num

ber

%]

Si

C

Fig. Change of SiC Surface Composition with Different Dose of Nitrogen Ion Irradiation, Measured with X-ray Luminescence Analysis.

TITechDOESKasuya Lab.

Fig. Ablated Thickness vs. Black Body Temperature of X-ray

Source. Calculation in Case of LiF. White Small Box is Experimental Result for Comparison.

1 2 0

2

4

6

8

Black body temperature kT[keV]

Ab

late

d t

hic

knes

s [

μ m

]

15[J/cm ]

45[J/cm ]

90[J/cm ]

2

2

2

TITechDOESKasuya Lab.

The plots of Planck’s law.

Photon energy hν[KeV]

X-r

ay in

ten

sity

I [

pJ･

s]

0 1 2 3 4 50

2

4

6

8

10

kT=100[eV]

kT=300[eV]

kT=500[eV]

X-ray absorption with sliced thin layers.

0,1I

0,2I

0,nI

1E 2E nE

x

Mass absorption coefficient of C

Photon energy hν[KeV]

M.A

.C. μ

[cm

2 /g]

1 2 3 4 5101

102

103

104

105

106

107

Mass absorption coefficient of LiF [1]

Photon energy hν[KeV]

M.A

.C. μ

[cm

2 /g]

1 2 3 4 5101

102

103

104

105

106

107

Calculation for heat capacity of Carbon’s thin layer

][2.19)(42

1

2 KJdTTCQxRT

T P

]/[10975.5 4 gJQsub 353 1079.81027.417.17)( TTTC p

][42002 KTT sub ][15.2981 KT

][000.1 mR ]/[10253.2 36 mg

][10000.1 8 mx

][4.3)(42

1

2 KJdTTCQxRT

T P

]/[10211.8 3 gJQeva

]/[474.2 gKJC p

][19542 KTT eva ][12001 KT

][000.1 mR ]/[10653.2 36 mg

][10000.1 8 mx

Calculation for heat capacity of LiF’s thin layer

Ablation Estimation for C

Distance from surface

0.5

Ab

sorb

ed e

ner

gy E

n [

KJ]

0 1.0

50

100

[μ ｍ ]

kT=200eV,F=45[J/cm2]

Ab

sorb

ed e

ner

gy E

n [K

J]

Ablation Estimation for LiF

Distance from surface [μ ｍ ]

50 10

25

50 kT=200eV,F=45[J/cm2]

Absorbed energy in one C layer with kT=200[eV],F=45[J/cm2]

X-r

ay in

ten

sity

I [

pJ･

s]

Photon energy hν[KeV]

0 1000 20000

0.5

1

1.5

100th Layer

400th Layer

700th Layer

Absorbed energy in one LiF layer with kT=200[eV],F=45[J/cm2]

0 1000 20000

0.5

1

1.5

Photon energy hν[KeV]

X-r

ay in

ten

sity

I [

pJ･

s] 100th Layer

400th Layer

700th Layer

Sublimated depth of C

0

0.5

1

1.5

Black-body temperature kT[keV]

Su

bli

mat

ed d

epth

X [ μ

m]

15[J/cm ]2

45[J/cm ]2

90[J/cm ]2

0.5 1

Evaporated depth of LiF

1 20

2

4

6

8E

vap

orat

ed d

epth

X [μ

m]

Black-body temperature kT[keV]

15[J/cm ]2

90[J/cm ]2

45[J/cm ]2

Apparatus for UV Laser-Target Interaction

Excimer laser LPX 305i (LPX 300 series) for laser target interaction (EL 1,2 J, wavelength 157 nm, 193 nm, 248 nm,

f = 50 Hz, 20 ns)

  

3D Analysis of Tungsten Surface with Profiler

2D Analysis of Tungsten Surface with Profiler

3D Analysis of Graphite Surface with Profiler

2D Analysis of Graphite Surface with Profiler

Summary

 Under the proton beam irradiation with the dose of about 10J/cm2 per shot, the ablated rates were up to 20 micron for carbon, and 26 micron for LiPb and SiC. The change of the rate was investigated with the change of the dose. Under the nitrogen beam irradiation with the dose of 4J/cm2, the ablated thickness of up to 6 micron was observed for SiC, while no remarkable ablation was observed for Al2O3. Surfa

ce conditions before and after the nitrogen beam irradiation was investigated with a microscope and x-ray fluorescence analysis. SiC surface turned into Si surface, while no discernible change was seen for Al2O3. Under the x-ray irradiation of LiF, SiC/Si and SiC, the ablati

on thickness of 3 , 0.5 and 0 micron was observed under the dose of 40, 7 and 7J/cm2. Under the UV laser irradiation of W and C, the surface change could be observed with a 3D surface profiler. More experiments and calculations with more advanced methods are scheduled in the near future.

Summary