Application of optical techniques for in situ surface analysis of carbon based

materials

T. Tanabe, Kyushu University Necessity of development of

(1) in-situ tritium detection technique

To determined where and how much tritium is retained at particular locations in tokamak

(2) in-situ removing technique

Different techniques will be required depending on tritium retaining materials and its concentration

9th ITPA meeting on SOL/divertor physics, Garching, May 7-10, 2007

Optical techniques can be in-situ surface analysis systems with assistance of optical fibers, mirrors and lens

• UV to Visible

Optical absorption/emission spectroscopy • Infrared to far-infrared

IR, FT-IR, Raman

• Laser light

Optical emission/absorption

Energy loss (Laser Raman)

Neutral particle emission (Thermal Desorption Spectrosocpy)

Ion emission (TOF-MASS)

Electron energy loss or electron emission spectroscopy can be used but require sophisticated energy analyzing systems in vacuum

• UV to Visible

Optical absorption/emission spectroscopy • Infrared to far-infrared

IR, FT-IR, Raman

In this work,

Application of

for carbon materials retaining hydrogen.

Lots of works have been done for thin films (a:C-H film) but not much for bulk carbon materials, because graphite is a conductor and opaque.

Need to analyze reflecting light,

which gives limited information of near surface region.

In-situ high resolution observation & diffraction

B c

5 nm

Initial

300s

1300s

1900s

000002

B c

HOPGFiber

Inte

nsi

ty [

a.u

.]

11001800 1600 1400 1200

Raman Shift (cm-1)

HOPG

B c

Laser Raman Spectra of Hydrogen ion irradiated HOPG

Electron diffraction

h

hs

s

D+ ion irradiation

Original Graphite layers

2D modificationDefect production in the layers

3D modificationDefect formation between the layers

AmorphousHomogenous in 3D

K. Niwase et al., J. Nucl. Mater. 191-194 (1992) 335-339

K. Niwase et al., J. Nucl. Mater. 191-194 (1992) 335-339

He+ irradiation D+ ion irradiation

Amorphous Amorphous

Substrate

Eroded area

Re-deposited layer

Raman Shift (cm-1)1800 1500 1200 800

Inte

nsi

ty [

a.u

.]

D peak(1355cm-1)G peak(1580cm-1)

Substrate

Eroded area

Re-deposited layer

Raman Shift (cm-1)1800 1500 1200 800

Inte

nsi

ty [

a.u

.]

D peak(1355cm-1)G peak(1580cm-1)

TiC/Inconel

TiC/Mo

Lower X-point divertor

Vacuum vessel

Inner strike region

Private flux region

Outer strike region

TiC/Inconel

TiC/Mo

Lower X-point divertor

Vacuum vessel

TiC/Inconel

TiC/Mo

Lower X-point divertor

Vacuum vessel

TiC/Inconel

TiC/Mo

Lower X-point divertor

Vacuum vessel

Inner strike region

Private flux region

Outer strike region

Inner strike region

Private flux region

Outer strike region

A schematic view of a poloidal-section

inboardinboard

Re-deposited layer

inboard Eroded area

JT-60: Open divertor tiles

0 0.5 1 1.5 2 2.5

deposited area

eroded area

0

50

100

150

FWH

M15

80 (G

-pea

k w

idth

) [cm

-1]

I1355

/I1580

0

2

4

6

8

10

0

20

40

60

80

Am

oun

t of

ret

enti

on h

ydro

gen

[1022

atom

s/m

2 ]

Th

ickness of re-d

eposited

layer(um)

60

80

100

120

140

600

700

800

900

1000

1100

0 50 100 150 200 250 300

deposited areaeroded area

FW

HM

1580

[cm

-1]

Su

rface temperatu

re(K)

Poloidal distance [mm]

0

2

4

6

8

10

0

20

40

60

80

Am

oun

t of

ret

enti

on h

ydro

gen

[1022

atom

s/m

2 ]

Th

ickness of re-d

eposited

layer(um)

0

2

4

6

8

10

0

20

40

60

80

Am

oun

t of

ret

enti

on h

ydro

gen

[1022

atom

s/m

2 ]

Th

ickness of re-d

eposited

layer(um)

60

80

100

120

140

600

700

800

900

1000

1100

0 50 100 150 200 250 300

deposited areaeroded area

FW

HM

1580

[cm

-1]

Su

rface temperatu

re(K)

Poloidal distance [mm]

Line analysis

8.8 4.4 2.9 2.2 1.8439.0Crystalline size [ nm ]

0

50

100

150

0 0.5 1 1.5 2 2.5

G-p

eak

Wid

th [

cm-1

]

D-peak/G-peak

deposited areaeroded area

○ 　 Redeposited 　 area

○ 　 Eroded area

TEXTOR　 ALT-ｌｌ　tile

100011001200130014001500160017001800

Inte

nsi

ty [

a.u

.]

Raman Shift [cm-1]

UnirradiatedUnirradiated

G peakG peak D peakD peak

700K700K

1200K(Eroded area)

1200K(Eroded area)

Irradiation with very high flux and high temperature at NAGDIS-II

Cooperation with Drs. Ohno and Takamura

10mm

1200K Irradiation

7.7×107.7×102626 /m /m-2-2

700K Irradiation

3.4×103.4×102626 /m /m-2-2

Mostly eroded

Eroded

Deposited

0

50

100

150

0 0.5 1 1.5 2

Amorphous

FW

HM

1580

cm-1

I1355/I1580

9.09.0 4.54.5 3.03.0 2.02.0450450Crystalline size [ nm ] Crystalline size [ nm ]

700 K700 K(100eV)(100eV)

600 ～700K(25keV)

Ion implantation25keV

UnirradiatedUnirradiated

1200KDeposited area

Eroded area1200K

B. Disher, et al. Appl. Phys.Lett. 42(1983)636 G. Compagnini, Phys. Rev. B51(1995)11168

Wider band gap

Higher sp3 C

Optical absorption and band gap of a:C-H film

Absorption coeff. of three a:C-H film with different refractive index. Absorption edge of diamond is shown for comparison

IR regionCH stretch band

FT-IR spectra in the CH stretch band region of the VGCF after successive irradiations of 6.0, 3.0 and 1.0 keV H+ ions to saturation. (a) 373 K, (b) 623 K, (c) 823 K, (d) 923 K. The separated-band assignment, band frequency are indicated at the resolved bands.

Estimated relative CHx density in the hydrogen-ion implanted VGCF with or without the post-irradiation heat-treatment, as a function of the heat-treatment temperature

Ion irradiated carbon fiber (VGCF)

FT-IR spectra in the CH stretch band region

FT-IR Spectra of hydrogen implanted HOPG in reflection geometry

-0.15

-0.1

-0.05

0

0.05

80012001600200024002800320036004000

Rel

ativ

e A

bsor

banc

e / A

rb.U

nit

Wavenumber / cm-1

1015 ion/cm2

1017 ion/cm2

1018 ion/cm2

※ Reference: HOPG

Gap widening

C-H Stretching

Polarized light

Reflected light

Standing wave

Sample

Conclusions Following techniques are probed to be useful for

in situ surface analysis of carbon materials

• Laser induced optical emission Need to understand ablation physics

• Laser Raman Spectroscopy determines micro-structure but hard to get H/C.

• Optical absorption Spectroscopy Band gap width could be related to H/C.

• FT-IR could give H/C but sill need to increase S/N.

0

2 104

4 104

Inte

nsit

y (

arb.

uni

ts )

C2

C

Nd:YAG532nm

C+

C2+

C

&C2+

C2+

&C2

C2

CC

C+

IL = 3.0x1011 W/cm2C2+

C+C+

C+

0

2 103

4 103

300 400 500 600 700 800 900Inte

nsit

y (

arb.

uni

ts )

Wavelength (nm)

C2 Nd:YAG 532nm

C2 C2 C2

IL = 3.0x1010 W/cm2

Laser induced visible light emission

SAR266

Emission from C2, C, C+ & C2

+

WAR266

Emission from C2

Y. Sakawa et al. J. Nucl. Mater. in press

0

1

2

3

0 400 800

C+Cn

+

IL = 2.3x1010 (W/cm2)

t2 (s2)

TO

FMS

Inte

nsit

y(a

rb. u

nits

)

0

0.1

0.2

0.3

0.4

TO

FMS

Inte

nsit

y(a

rb. u

nits

)

C+ IL = 3.0x1011 (W/cm2)

Laser induced Time Of Flight Mass Spectrometry (TOFMS)

SAR266Emission of C+ , C2+ ions

WAR266Carbon clusters (Cn

+)

Y. Sakawa et al. J. Nucl. Mater in press