Deposition in the MKII - Gas Box DivertorDeposition in Septum

M. Rubel, P. Coad, J. Likonen

OUTLINE

• General deposition pattern on MKII-GB tiles

• Septum

• Summary

JET Divertors

Results for MK-IIA presented on PSI-15

1

43 5

67

8

GB

inner outer

MKII - GB

Operation time ~ 18 months in both cases

Mark II-A divertor

Beryllium and Deuterium: Comparison MKII-A and GB

(shadowed areas on tiles 3 and 4 are not included)

0

5

10

15

20

25

30

D a

nd

Be

(e

18

/cm

2)

Be e18

D e18MKII-GB

0.00

5.00

10.00

15.00

20.00

25.00

30.00

1

DIVERTOR TILE (POLOIDAL DIRECTION)

D a

nd

Be

(e

18

/cm

2)

D (e18)

Be (e18)

1

10987

65

4

2 3

MKII-A

1

3 4 6

7 8

DBe

DBe

Major differences:

D/Be ratio < 1 on MKII-A

D/Be ratio > 1 on MKII-GBPossible reason:Cleaning after DTE-1 to reduce T level.

Significant co-deposition (and fuel inventory) in the shadowed corner of the outer divertor (tile 6).Possible reason:Shadowing due to geometrical factor(as in MKI divertor)

SEPTUM

a

ba: three support platesb: septum (divider) plate

Deposition on the GB tiles

C-end

D-end

Central plate

Thickdeposit

Shadow after the IPPdeposition monitor

Deposition on the divider plates

INNEROUTER

Deposition on the septum tiles:Central support plate

AD

0

2

4

6

8

10

0 50 100 150 200POLOIDAL POSITION [mm]

D a

nd

Be

[10e

18/c

m2]

Be e18

D e18

BC

0

5

10

15

20

25

0 50 100 150 200POLOIDAL POSITION [mm]

D a

nd

Be

[10e

18/c

m2]

Be e18

D e18

Deposition on the septum tiles:Central support plate

Deposition on the divider plates: Inner divertor

0

0.5

1

1.5

2

0 20 40 60 80 100 120"Toroidal" position [mm]

D a

nd

Be

[10e

18/c

m2]

Be e18

D e18

“Bas

e”

Top

Base

Cen

tral plate

En

d rib

Dusty

0

0.5

1

1.5

2

0 20 40 60 80 100 120"Toroidal" position [mm]

D a

bd

Be

[10e

18/c

m2]

Be e18

D e18

“Bas

e”

Base

Top

Central plate

End rib

Deposition on the divider plates: Outer divertor

Deposition on the septum tiles Summary

Deposition on the plates is mainly seen in the near-plasma region from the inner divertor side (up to 25 mm from the edge).

Thick deposits (> 50 m ?) only on a side of one plate (C-end).

Little deposition deep inside the Gas Box (thin deposit, d < 10 m).

Little deposition on the divider plate (thin deposit, d < 10 m) .

Small content of beryllium in the Gas Box.

No C-13 (above the background level) found on the plates.

Gas Box plates can not be considered as the major trap for transported and re-deposited material.

The results also indicate that the direct across-divertor transport is negligible (if any).