PSI 2008 Toledo May 2008 © Matej Mayer Carbon balance and deuterium inventory from a carbon...

PSI 2008 Toledo May 2008 © Matej Mayer

Carbon balance and deuterium inventory from a

carbon dominated to a full tungsten ASDEX

UpgradeM. Mayera, V. Rohdea, K. Sugiyamaa, J.L. Chena, X. Gonga,

C. Hopfa, J. Likonenb, S. Lindiga, R. Neua, G. Ramosc,

E. Vainonen-Ahlgrenb, A. Wiltnera, and ASDEX Upgrade Team

a Max-Planck-Institut für Plasmaphysik, EURATOM Association, Garching, Germanyb Association EURATOM-TEKES, VTT Processes, Espoo, Finland

c CICATA-Qro, Instituto Politécnico Nacional, Querétaro, México

• Evolution of B, C deposition in the divertor

• Evolution of D inventory in the divertor

• Comparison between plasma-sprayed and bulk W

Plasma-related aspects of all-W machine were covered by R. Dux, I-6


Motivation

Tritium inventory in ITER dominated by codeposition

with carbon (if carbon is present)

But large uncertainties: Carbon sources and

carbon transport poorly understood

Stepwise replacement of C by W in AUG offers

unique possibility to study C sources

A. Kirschner et al., JNM 363-365 (2007) 91

Be

W

C


Motivation (2)

Much lower T inventory in all-W machine

is predicted

All-W predictions based solely on

laboratory data

Confirmation in existing tokamaks

required

All-W is probably the only option for

a future DEMO reactor

Data from existing tokamaks required

J. Roth, this conference, R-1


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 6000

2

4

6

s-coordinate [mm]

B + C C

9C456B6A

Dep

osi

tio

n o

f B

+C

[10

19 a

t./c

m2]

AUG inner divertor: Deposition of B + C

2002 – 20034940 s

Inner divertor deposition in 3000 s

C 14.6 gB 2.8 g

6A

4


0 200 400 6000

2

4

6

s-coordinate [mm]

B + C C

9C456B6A

Dep

osi

tio

n o

f B

+C

[10

19 a

t./c

m2]


2004 – 20053150 s


C 13.8 gB 4.7 g

6A

4


0 200 400 6000

2

4

6

s-coordinate [mm]

B + C C

9C456B6A

Dep

osi

tio

n o

f B

+C

[10

19 a

t./c

m2]


2005 – 20062950 s


C 2.2 gB 2.3 g

6A

4


0 200 400 6000

1

2

3

4

5

6

7

s-coordinate [mm]

C, RBS C, NRA

9A456B6A

Dep

osi

tio

n o

f B

+C

[10

19 a

t./c

m2]


20072620 s

6A

4


C 1.0 gB 0 g (below detection limit)


1

10

2002/2003 2004/2005 2005/2006 2007

Inner divertor C

Remote areas C

Dep

osi

tio

n in

300

0 s

[g]

Campaign

AUG divertor: Evolution of B, C deposition

Reduction of C deposition by

factor ~15 from C-dominated

to all-W machine

Largest decrease after coating of

ICRH protection limiters with W

Decrease in C plasma concentration

by factor 2–3R. Pugno, EPS 2008

Available C source at walls > 1000 times

C plasma inventory even in all-W machine


1

10

2002/2003 2004/2005 2005/2006 2007

Inner divertor C, B

Remote areas C

Dep

osi

tio

n in

300

0 s

[g]

Campaign

AUG divertor: Evolution of B, C deposition

Reduction of C deposition by

factor ~15 from C-dominated

to all-W machine

Largest decrease after coating of

ICRH protection limiters with W

5-6 boronizations/campaign from 2002-2006

B-deposition almost constant

No boronization in 2007, extensive cleaning

B-deposition below detection limit of 0.1 g


Carbon transport in AUG

2005 – 2006

3 g20%

11 g80%

14 g3 g

100%2 g

2004 – 2005

• Small influx of residual carbon in main chamber• Identical outer divertor erosion in both campaigns, M. Mayer et al., PS T128 (2007) 106

Assumptions:

Spectroscopy: 1 g A. Kallenbach et al., JNM 363-365 (2007) 60


Carbon sources in all-W machine

100 µm

Residual C deposition in all-W machine:

1 g in 3000 s

• Electrical arc’s can remove W coating and

release C from tile

0.05 g C from inner baffle A. Herrmann, this conference, O-5

• Erosion in not fully coated tile gaps and

back sides of tiles

• Residual carbon layers from previous campaigns

(probably small due to extensive cleaning)

• C impurities in W coatings

• Photo-desorption of CO, CO2 from walls V. Philipps et al., J. Nucl. Mater. 200 (1993) 355

SE

BSE


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

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

4940 s

2620 s


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

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


1000 1100 1200 1300 1400 1500 1600 17000.0

0.1

0.2

0.3

0

100

200

300

400

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

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


0 5 10 15

0.01

0.1

1

SIMS NRA

Depth [µm]

Co

nce

ntr

atio

n o

f D

[at

%]

1100 12000.0

0.1

0.2

0.3

0.4

0.5 VPS-W, NRA < 3 µm VPS-W, TDS Bulk W, NRA < 7 µm Bulk W, TDS

s-coordinate [mm]

Am

ou

nt

of

D [

1019

at.

/cm

2 ]

VPS-W versus polycrystalline W in outer divertor

• VPS-W and bulk W trap about the same total amount of D

• Bulk W shows deep diffusion (~ mm) at low D concentrations (< 100 ppm)

K. Sugiyama et al., Hydrogen Workshop Salamanca

Bulk W

Langmuir probes

VPS-W

20 mm

Background level


10-1 100 101 102 103 104 10510-4

10-3

10-2

10-1

100

101

poly-WVPS-W

AUG, all-W (poly)

AUG, all-W (VPS)

Deu

teri

um

inve

nto

ry [

g]

Discharge time [s]

AUG, C-dominated

Extrapolation to higher fluences / longer discharge times

• Good agreement between laboratory measurements and AUG data

• Slower increase of D-inventory in W than in C for longer discharge times

W even more beneficial for long pulse machines

VPS-W: A.V. Golubeva et al., AIP Conf. Proc. 837 (2006) 12poly-W: O. Ogorodnikova et al., J. Appl.Phys. 103 (2008) 034902

D-inventory in AUG divertor


Conclusions

• Decrease of divertor C deposition by factor ~15 from C-dominated to all-W machine, normalized to 3000 s

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

• Boronizations result in high D-inventory due to co-deposition with B Decrease of D-inventory only visible in unboronized machine

• D-inventory in C-dominated machine determined by co-deposition in inner divertor + remote areas

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

PSI 2008 Toledo May 2008 © Matej Mayer Carbon balance and deuterium inventory from a carbon...

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