SEWG Fuel Retention July 2008 © Matej Mayer Fuel retention in ASDEX Upgrade tungsten coatings M. Mayer, M. Balden, K. Krieger, S. Lindig, O. Ogorodnikova,

SEWG Fuel Retention July 2008 © Matej Mayer

Fuel retention in ASDEX Upgrade tungsten coatingsM. Mayer, M. Balden, K. Krieger, S. Lindig,

O. Ogorodnikova, V. Rohde,

K. Sugiyama, and ASDEX Upgrade Team

Max-Planck-Institut für Plasmaphysik, EURATOM Association, Garching, Germany

• Retention in ASDEX Upgrade from post-mortem studies

• First results on modelling of ASDEX Upgrade retention

• Surface modifications (“blistering”)


Retention in ASDEX Upgrade

from post-mortem studies


W coverage in AUG 2002 – 2007

Step by step replacement of C tiles

by W coated tiles

• 3 – 4 µm W-PVD on most tiles

• 200 µm plasma-sprayed W at outer strike point


0 200 400 600 800 1000 1200 1400 16000.0

0.5

1.0

1.5

2.0

2.5

3.0

NRA < 3.3 µm TDS

3B3A21109D9C9B9A456A

s-coordinate [mm]

Am

ount

of D

[10

19 a

t./cm

2 ]6B

Deuterium inventory

C-dominated campaign 2002/2003

D on divertor tiles 0.9 – 1.3 gD below roof baffle 0.4 gin 3000 s

Full W campaign 2007

D on divertor tiles 0.15 – 0.23 gD below roof baffle 0.03 gin 3000 s

6A

4 9B

1A

3A 4940 s

2620 s


0 100 200 300 400 5000.0

0.1

0.2

0.3

0

100

200

300

400

D, NRA D, TDS C, NRA

s-coordinate [mm]

Am

ou

nt

[1019

at.

/cm

2 ]

456B

Str

ike

po

int

[s]

6A

Deuterium inventory in inner divertor of all-W machine

Correlation between distributionsof C and D

D inventory in inner divertor

still dominated by C-codeposition

6A

4


1000 1100 1200 1300 1400 1500 1600 17000.0

0.1

0.2

0.3

0

100

200

300

400

0

2

4

6

8

D, NRA < 3 µm D, TDS C, NRA

s-coordinate [mm]

Am

ou

nt

[1019

at.

/cm

2 ]

3-4 µm PVD

3B3A21

Str

ike

po

int

[s]

10

200 µm VPS

Ion

flu

ence

[10

25 io

ns/

m2 ]

Deuterium inventory in outer divertor of all-W machine

D inventory in outer divertor

dominated by trapping in W

Deep diffusion (> 3 µm) observed for VPS layers at outer strike point

3B

1


AUG divertor: Evolution of D inventory

Carbon dominated machine

• Total D-inventory dominated by inner divertor

and remote areas

All-W machine

• Boronizations result in high D-inventory,

co-deposition with B (2005/2006 campaign)

• D-inventory dominated by trapping

in VPS-layers at outer strike point

• Decrease of total D-inventory by factor 5 – 10

from C-dominated to all-W

0.1

1

2002/2003 2004/2005 2005/2006 2007

Inner divertor Outer divertor Remote areas Total

D-I

nve

nto

ry in

300

0 s

[g]

Campaign


First results on modelling of

ASDEX Upgrade retention


1021 1022 1023 1024 1025 1026

1019

1020

1021

1022

1023

~F0.53

Experimental dataPoly W lab; AUGVPS-W lab; AUGFitPoly W lab + AUGVPS-W lab + AUG

Deu

teri

um

ret

ain

ed [

D/m

2]

Incident fluence [D/m2]

~F0.72

Retention as function of fluence

VPS-W

• Laboratory and AUG data (VPS-W from tile 1) available

Polycrystalline W

• Laboratory and AUG data (Langmuir probes) available

4 µm PVD-W

• No data (with known fluence/retention) available

Assume same properties as polycrystalline W

4 µm thickness taken into account I4µm = 0.67 x ITotal


1

3B

2

3A

Incident fluence

Outer divertor

• Ion fluence measured with Langmuir probes on tile 1

Extrapolation to tiles 2, 3A

Fluence on 3B from erosion in 2004/2005

Inner divertor

Assume identical number of ions as outer divertor 4.2 m2, 1022 ions/m2 s

Roof baffle

Assume 3.3 m2, 1021 ions/m2 s

Main chamber

Assume 8 m2, 1021 ions/m2 s and 32 m2, 1019 ions/m2 s

Codeposition with C

• 1.9x1019 C-atoms/s, D/C = 0.41.1 1.2 1.3 1.4 1.5 1.6 1.7

0

1

2

3

4

5

6

7

8

Langmuir-probe data Fit and extrapolation

3B3A2

Ion

flu

ence

[10

25 io

ns/

m2]

s-coordinate [m]

1


1

3B

2

3A

Modelling: Outer divertor

Good agreement between modeland experimental data, keepingthe uncertainties in mind

1.1 1.2 1.3 1.4 1.5 1.6 1.70

1

2

34 µm PVD

Model TDS NRA < 3.3 µm

3B3A2

D-i

nve

nto

ry [

102

2 D

/m2]

s-coordinate [m]

1

200 µm VPS


100 1000 10000

1021

1022

1x1023

Model Total Inner divertor Roof baffle Outer divertor Codeposition with C Main chamber

Experimental Inner + roof + outer + main chamber (model) Inner divertor Roof baffle Outer divertorD

-in

ven

tory

[A

tom

s]

Discharge time [s]

Modelling: Full ASDEX Upgrade

• Good agreement for outer divertor

• Model gives too high inventory for inner divertor More realistic fluence data necessary


Modelling: Work in progress

• Ion fluences for inner divertor K. Krieger, July 2008

• Temperature history of outer divertor for 2007 campaign A. Herrmann, July 2008

• Inventory in 4 µm PVD-W as function of fluence O. Ogorodnikova, October 2008


Surface modifications (“blistering”)


= 1026 D/m2, Tirr = 550 K

= 1026 D/m2, Tirr = 583 K

Lab studies, 38 eV D-ions: “Blisters” AUG, Langmuir-probes: “Blisters”

V. Kh. Alimov



“Blisters” are not hollow!

V. Kh. Alimov



Often (always?) widened cracks (grain boundaries?) below “blisters”

V. Kh. Alimov


Tirr = 515 K

Tirr = 567 K

Lab studies, 38 eV D-ions: “Sponge” AUG, Langmuir-probes: “Sponge”

“Sponge”-like structures are observed

V. Kh. Alimov


Summary

Retention in ASDEX Upgrade:

• Decrease of trapped D in divertor by factor 5 – 10 from C-dominated to all-W machine

• D-inventory in all-W machine determined by deep diffusion into W at outer strike point

Modelling of ASDEX Upgrade data:

• First modelling using experimental laboratory/AUG data and measured AUG fluxes

• Good agreement for outer divertor, further work needed for inner divertor

Surface modifications:

•“Blister”-like structures observed in laboratory studies and AUG polycrystalline W

• No blister cap, not hollow (but often/always cavity/crack observed)

These are no classical blisters! Naming?

Documents

SEWG Fuel Retention July 2008 © Matej Mayer Fuel retention in ASDEX Upgrade tungsten coatings M. Mayer, M. Balden, K. Krieger, S. Lindig, O. Ogorodnikova,