Depth-profiling and thermal desorption of hydrogen isotopes for plasma facing carbon tiles in JT-60U

(Long term hydrogen retention)

T. Tanabe, Kyushu University

☆Depth profiles in redeposited layers and eroded area　　　　　　　 Depth profiles of T in divertor tiles of JET and JT-60U 　 　　 Depth profiles and TDS of hydrogen isotopes (H, D and T) Importance of Isotopic exchange and tile temperature

☆Deep penetration into the bulk

Penetration thorough open pores of CFC and graphite Thermal diffusion Absorption at and/or permeation to the backside of tiles.

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

GasGraphite(Solid)Liquid

Determined by

○ : IR

● : NMR

▲ :EELS

A:C-H film ever produced

Hydrogen solubility

(very small)

T. Tanabe et al., Journal of Nuclear Materials 313–316 (2003) 478–490

RT

Hydrogen solubility

Hydrocarbons are unstable above 800K

Kee

pin

g n

earl

y th

e sa

me

leve

l

Above ~800K

Isotope exchange becomes easier

H2 and H0

Hydrogen retention and depth profile under H+ and H2 exposure

All grains are under the same static pressure

Below ~700K

No diffusion into bulk or particles

0

100

200

300P

SL

in

ten

sity [P

SL

/m

m2 ]

10

100

1000

104

105

106

0 5 10 15 20 25 30 35 40

Cyl_3Cyl_4Cyl4_BN4Cyl_7Cyl_8Cyl_9

Trit

ium

p

er d

isk

[k

Bq

]

Depth [mm]

BN4

BN7

Tritium activity is mostly on the plasma facing surface

JET tile : Cross section of cored hole in divertor base tile :BN4

Surface

Probably due to temperature difference

Backs side of BN7

Stripes corresponding the woven structure of 2-D CFC

PSL intensity [PSL/mm2]

020406080100

120

Absroption of low energy (gaseous) tritium

Cf. No stripes were observed on the front surfaceT. Tanabe et al., Journal of Nuclear Materials 313–316 (2003) 478–490

0

10

20

30

40

50

010203040

50PSL intensity [PSL/mm2]

　 50

　 40

　 30

　 20

　 10

　 0

PS

L in

tens

ity

[PS

L/m

m2 ]

inside

Outside

Tritium depth profile : observed by cross-sectional view of dome top tile in JT-60U divertor

SIMSH retention within <2.1m

～ 4.3 x 1016(/cm2)H/C at surface ~3.5 %

0

1

2

0 0.5 1 1.5 2 2.5Depth (m)

D/C

(%)

NRA_DM2_D/C(%)

0

1

2

3

4

5

0 0.5 1 1.5 2 2.5Depth (m)

H/C

(%)

Estimated H/C(%)

0

1

2

3

4

5

0 0.5 1 1.5 2 2.5Depth (m)

(H+D

)/C

(%)

Estimated (H+D)/C(%)

0

0

（ H+D)/12C

H/12C

D/12C

Thin deposits on outer dome wing

NRA:D retention within 2.1m

～ 8.0 x 1016(/cm2) D/C ~ 2%(max)

Y. Oya, Y. Hirohata, et al., J. Nucl. Mater. 313-316 (2003) 209

NRA + SIMS 　 　(H+D)/C

(<2.1m)　～ 1.2 x 1017(/cm2)

(H+D)/C (<0.5m) 　

(H+D)/C ～ 2.5%-

11-

depth1.7mT. Hayashi et al. J. Nucl. Mater

400 600 800 1000 1200 温度 (K)

0

0.5

1

1.5

2

2.5H

2

HD

D2

400 600 800 1000 1200 温度 (K)

(1019

mol

ecul

es・m

-2・s

-1)

気体

放出

率

Inner BafflePlate Divertor

Inner Dome OuterDivertor

Outer BafflePlate

DM3,5,6,7,9

Inboard Outboard

Thermo-Couple

Inner BafflePlate Divertor

Inner Dome OuterDivertor

Outer BafflePlate

DM3,5,6,7,9

InboardInboard OutboardOutboard

Thermo-Couple

H2

HDD

2

400 600 800 1000 1200 温度 (K)

Redeposits on ID3

1000K

Eroded area OD1

1400K

0

2

4

6

8

10

12

14

BP11 BP1 ID1 ID2 ID3 DM3 DM5 DM6 DM7 DM9 OD1 OD3 BP3Removal

ID3BulkOD1Bulk

H2

HDD2

C1 group

C2,3 group

放

出気

体量

(1022

ato

ms/

m2 )

試料名

0

0.2

0.4

0.6

0.8

1

1.2

D/H

Redeposits on DM9

800K

Temperature/K

TDS measurementsD

es

orp

tio

n　

rate

/ 1

019

　m

ole

cu

les･

m-

2 ･s

-1

To

tal

rete

nti

on

/ 1

022　

ato

ms

･m

-2

Sample positionBulk retention

Temperature reduces D/H

D/H << 5.1 (ratio of discharges numbers of DD/HH)

→ Replacement of D by H

0

2

4

6

8

10

0 2 4 6 8 10

BPIDDMODBulk

D蓄

積量

(10

22 a

tom

s・m

-2)

H蓄積量 (1022 atoms・m-2)D

ret

entio

n

D/H ～ 1.6DM 800K

D/H ～ 0.47ID 1000K

H retention

Redeposited layers on ID… Deposited at higher temp(1000K). Low D/H DM…Deposited at lower temp.(800K) High D/H (Less exchange)

1.40 × 1021 atoms·m-2·m-1

0

5

10

15

0 20 40 60 80

HDH+D

Thickness (m)H a

nd D

ret

etni

on(1

022at

oms ・

m-2

)

1.40 × 1021 atoms·m-2·m-1

0

5

10

15

0 20 40 60 80

HDH+D

Thickness (m)H a

nd D

ret

etni

on(1

022at

oms ・

m-2

)

0

5

10

15

0 20 40 60 80

HDH+D

Thickness (m)H a

nd D

ret

etni

on(1

022at

oms ・

m-2

)

Homogeneous distribution with (H+D)/C = 0.031Indicating Isotope exchange even in deep region owing to high temp.

On the Inner Divertor 1000K

Kee

pin

g n

earl

y th

e sa

me

leve

l

Above ~800K

Isotope exchange becomes easier

Bulk retention given by H2 and H0

H2 and H0

Below ~700K

No diffusion into bulk or particles

Redeposited process with hydrogen incorporation

Substrate

Starting DD discharge

Temperature

Temperature

Low High

Low

Formation of redeposited layers

Higher heat load

Lower heat load

Addition of HH discharges

After DDdischyarge

HD mixing in the layers

HD mixing near boundary only

Hydrogen retention at eroded area

Starting DD discharges

Temperature High

Eroded area with high heat load (OD)

Addition of HH discharges

Termination of DD discharges

Substrate

No depositionHigh energy implantation

Hydrogen retention and depth profile

under exposure of energetic H+ and H2 neutrals

All grains are under the same static pressure

773K

973K

623K 623~673K

Base temp.573K

Innerdivertor

Outerdivertor

Baffle platesDome

　 Surface temperature increase DD discharges >> HH discharges Because NBI power of HH discharges ~ ½ of that of DD discharge

Depth profiles of JT-60U divertor tilesDepth profiles of JT-60U divertor tilesTile temperature monitored by TCs installed in the tiles

Maximum Surface temperatures estimated by a finite element modeling

K.Masaki, et.al., J.Nucl.Mater., 313-316 (2003) 514

Inner divertor tile, ~1000 K

Dome unit tile~800 K

Outer divertor tile ~1400 K