j.p. coad 1 h workshop, salamanca 3 june 2008 local deposition of 13c tracer at the jet mkii-srp...
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J.P. Coad 1 H Workshop, Salamanca 3 June 2008
Local deposition of 13C tracer at the JET MkII-SRP outer divertor
J Paul Coad
Hydrogen Workshop, Salamanca, 2-3 June 2008
J.P. Coad 2 H Workshop, Salamanca 3 June 2008
Local deposition of 13C tracer at the JET MkII-SRP outer divertor
J. P. Coada, , L. K. Aho-Mantilab, M. I. Airilab, D. E. Holec, J. Likonend, A. Widdowsona and JET- EFDA Contributors[1]
•JET-EFDA Culham Science Centre OX14 3DB, Abingdon, UKaUKAEA/EURATOM Fusion Association, Culham Science Centre, Abingdon, OX14 3DB, U.K.
bAssociation EURATOM-Tekes, Helsinki University of Technology TKK, PO Box 4100, 02015, TKK, Espoo, Finland
d Dept. of Engineering and Design, University of Sussex, Brighton, BN1 9QH, East Sussex, UK eAssociation EURATOM-Tekes, VTT, PO Box 1000, 02044 VTT, Espoo, Finland
[1] See the Appendix of M.L. Watkins et al., Fusion Energy 2006 (Proc. 21st Int. Conf. Chengdu) IAEA, (2006)
Introduction13C puffing experiment in 2004Local deposition near the puffing portGeneral considerations of shadowing in the JET divertor• Mk I divertor 1994-5• Mk II divertors 1995 - present timeConclusions
J.P. Coad 3 H Workshop, Salamanca 3 June 2008
13C-methane puffing experiment in 2004
•31 similar pulses on last day of operation•ELMy H-mode discharges:- BT 1.2T, IP 1.2 MA, ~7.5 MW additional heating•Total of 4.3 1023
molecules 13C-methane puffed in outer divertor from 48 locations
Approximate line of W-stripe is shown as white dashes
J.P. Coad 4 H Workshop, Salamanca 3 June 2008
Field line plot showing strike points and SOL region for the 13C-puffing experiment
•Occasional sweeps of strike-point position for Langmuir probe data•Collector probe on reciprocating probe in SOL at top of machine
J.P. Coad 5 H Workshop, Salamanca 3 June 2008
JG
03
.67
6-1
c
Tile 1
Tile 3
Tile 4
Tile 8
Tile 7
Tile6
Amounts of 13C measured on divertor tiles by SIMS and IBA
Note: Measurements have been extrapolated, assuming toroidal symmetry
Tile 13C amount(%)
1 2.2% 3 0.7% 4 3.2% SRP 1.8% 6 2.5% 7 15.4% 8 0.9% Total 27.0%
SRP
Shadowing edge
J.P. Coad 6 H Workshop, Salamanca 3 June 2008
SIMS
IBA
poloidal distance around the divertor (mm)
0 500 1000 1500 2000
13C
dep
osit
ed /
cm
2 / 13
C i
njec
ted
10-8
10-7
10-6
10-5
10-4
10-3final fit
J Strachan et al
Modelling of SIMS and IBA data
J.P. Coad 7 H Workshop, Salamanca 3 June 2008
G7B
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0a1a
J.P. Coad 8 H Workshop, Salamanca 3 June 2008
19-23(max) x1018 atoms/cm2
13-18.9 x1018 atoms/cm2
10-12.9 x1018 atoms/cm2
7-9.9 x1018 atoms/cm2
1-6.9 x1018 atoms/cm2
Total number deposited 13C in this area is ~215 x1018 atoms
Tungsten stripe13C injection
20mm
Cores cut for SIMS analysis
Deposition in shadow on tile 14OW G7B
J.P. Coad 9 H Workshop, Salamanca 3 June 200820mm
11063
11041 11047
0
200
400
600
800
1000
1200
1400
1600
1800
0 200 400 600 800 1000
11063
11041
11047
13CBe
O
12C
J.P. Coad 10 H Workshop, Salamanca 3 June 2008
13C deposition on 2ON G7A
J.P. Coad 11 H Workshop, Salamanca 3 June 2008
D and 13C concentrations
0
50
100
150
200
250
300
350
30 50 70 90 110 130 150 170
14OWG7B-D (x1e17) 2ONG7A-D (x1e17)
14OWG7B-13C (cts) 2ON G7A-13C (cts)
Distance on tile (poloidally), mm
Count rate
Ion Beam Analysis (Nuclear Reaction Analysis) data across tile depend on where line is relative to
injection point
J.P. Coad 12 H Workshop, Salamanca 3 June 2008
12C and 13C concentrations
0
50
100
150
200
250
300
350
30 50 70 90 110 130 150 170
2ON G7A-13C (cts) 2ON G7A-12C (x1e17)Distance on tile (poloidally), mm
Count rate
IBA data show film in
shadowed region is almost pure 13C (plus a
lot of H)
J.P. Coad 13 H Workshop, Salamanca 3 June 2008
Deposition at the JET Mk I divertor
JET MkI divertor operated 1994-5, first with C, then Be tiles
Pairs of tiles were mounted on water-
cooled poloidal bars, 196 bars toroidally.
There was a gap between each bar.
Tiles were in a “roof-top” arrangement
J.P. Coad 14 H Workshop, Salamanca 3 June 2008
Cross-section of tiles of the JET Mk I divertor, and deposition at the outer strike zone
• Exposed part of each tile in strike zone eroded• local re-deposition in the shadowed area
J.P. Coad 15 H Workshop, Salamanca 3 June 2008
Subsequent JET divertors have used large format tiles mounted to solid carriers, in
turn mounted on a water-cooled support structure
Pumping is only through the corners of the divertor, heavy deposition in these regions
No significant deposition in areas shadowed toroidally on
tiles
J.P. Coad 16 H Workshop, Salamanca 3 June 2008
Tritium remaining in the JET vessel after DTE1 in 1997
Rest of T assumed to be in flakes at bottom of vessel
Collected from the louvres and divertor floor
R-D Penzhorn, N Bekris, FZK, Karlsruhe
J.P. Coad 17 H Workshop, Salamanca 3 June 2008
G7B
12345678
0a1a
J.P. Coad 18 H Workshop, Salamanca 3 June 2008
Tile 3, exposed 1998-2001
Region of tile shadowed by adjacent tile
J.P. Coad 19 H Workshop, Salamanca 3 June 2008
JET septum 1998-2001
Almost complete separation of inner and outer divertor,
somewhat analogous to ITER
J.P. Coad 20 H Workshop, Salamanca 3 June 2008
100
Campaign averaged strikepoint position
0.8 mm
2.5 mm
15 mm
Source
Fit to sticking monitors:99% with sticking 0.9<1% with very low sticking
Hydrocarbon migration in JET
Migration to ITER pump ducts may not be large
Long term analysis in collaboration with TF FT
Recent analysis of septum shows low deposition !
Mayer, Rubel, Coad
J.P. Coad 21 H Workshop, Salamanca 3 June 2008
Conclusions
• Thick deposits of 13C-H found in shadowed zone where puffed methane enters divertor
• Overall 13C balance only marginally improved
• Pattern of deposition in JET may be influenced by particle flow
• Septum/PFR data in JET are encouraging for ITER dome, BUT this may be totally misleading