1. JET PFC Analysis, TFFT and the ILW
J P Coad
EURATOM/UKAEA Culham Division, Abingdon, UK
Introduction to TFFT and interaction with JET
Summary of programme of analysis of JET samples removed in 2004
Plans for JET samples removed in 2007
Update on progress on the JET ITER-like wall

2. JET FT AGHS Activation models T spreading Shutdown dose
Tritium in Tokamak
Tritium processes &
Waste management
Test Beds
Neutronic
& safety
Plasma Facing Components
Engineering
AGHS
Activation models
T spreading
Shutdown dose
rate calculation
Collection of
Operating experience
Dust conversion factor
of dust
Fatigue testing
W coatings
Glow
improvements
Active IR
thermography
JET
Flakes
Characterisation
JET Tiles
Improvement of
gas balance
JET WDS
system
T removal
From tiles
Micro gas
chromatography
Material
transport
Retention in
castellation
Microanalysis
of cross section
detritiation
Erosion
deposition
LIBS
Heating of tiles
In JET NB test bed
AES/XPS
T & Be JET tiles
Fibres &
neutrons

3. JET FT 2008 Benchmarking of CAD to MCNP interface Shutdown dose
Tritium in Tokamak
Tritium processes &
Waste management
Test Beds
Neutronic
& safety
Plasma Facing Components
Engineering
Benchmarking of CAD
to MCNP interface
Shutdown dose
rate prediction:
In situ optical
Dust
measurements
Advanced study for
detritiation
of non-plasma facing metals
Be Tiles detritiation
Material transport +
erosion
tungsten erosion in the JET divertor
Microanalysis of plasma deposited layers
tritium profile in carbon-based plasma-facing components
LIBS
Installation and commissioning of the plasmatron
collection of data
(VV & BeHF)
characterisation
of mirrors
Laser lock in
Inspection of
bolometer

4. Tasks on Fusion Technology 2006-2007 and 2008
Plasma Facing Components (10)
Test Beds
Tritium in Tokamak (2)
Tritium process and waste management (4)
Engineering (4)
Neutronics and Safety (2)
22 new tasks have been launched
during WP
15 tasks on going from previous years and 22 tasks launched during the year 2006 12
Presently FT has 37 running tasks
For the FT WP
16 new tasks have been approved
for a total budget of ~2.4 m€
More and more papers published and/or presented at conferences

5. Active IR Thermography in metal environment
Goal: get rid of reflected flux and measure real surface T
Heat pulse = perturbation of T0
2 l measurements and ratio  surface T°
(Material Emissivity constant!)
(CEA, Semerok, Gauthier)

6. LIBS to characterise divertor PFC

7. test of laser detritiation on JET tiles
Goal : test in BeHF + assessment of efficiency
(CEA, Semerok and UKAEA, Widdowson and Coad)

8. Cleaning JET tiles by Laser Ablation
total removal of film
some damage of the substrate
sharp boundary at edge of treated zone
300 microns
Laser treated zone
CFC substrate

9. Detritiation : inside gap generator
Goal : clean & detritiate castellations
D=60 mm
d= 0.8 mm
However, pattern not explained
Power: 130W, Pressure: 69mbar

10. Retention in castellations
Goal: characterise the retention in Be limiter castellations
(VR, Rubel)

11. Brief plasmatron facility description
Cold self-sustained volumetric plasma Volume: 18 litres Target diameter: ~25cm Ion energies: eV Magnetic field: 0.2T Pulse duration: steady state Flux density target: ~ ions/m2.s
Designed for PWI studies
Installation for operation in glove box
A gas mixture with a certain D/T ratio can be created in a volume by measuring the pressure and the mass flow of D/T coming from volumes containing D and T. Both loops have a separate control system.
Tominetti S. et al., Vuoto 26 (1997)

12. Plasma chamber UHV 1 UHV1 main pumping UHV 3 UHV3 differential pumping
I insulation C A
C cathode
A anode CW
CW cooling water T
T target TC
TC temperature control PM
PM permanent magnets
Gas, plasma, secondary ions and neutrals analyser
Gas inlet
Sedano L. et al., Phys. Stat. Sol. 188 (2001)

13. JET MkII-SRP Divertor used 2001-2004
Task Force E
JET
JET MkII-SRP Divertor used
Key: 1/11 means tile 1, sample 11
Septum Replacement Plate (SRP)
Campaign included:
4 weeks reversed field
trace tritium experiment
13C-methane puffing on last day
operation with JET wall temperature at 200°C

14. Inner Divertor Analysis
SIMS profiles sample 3/8 exposed
Inner part (to right of line):
similar to film deposited
Outer part: (to left of line)
High Be + other metals (e.g. Ni) except close to surface
Little 13C at surface
Tile 1
Tile 3
Tile 4
Task Force E
JET
Film deposited also has high Be/C ratio, although operations were at 200°C
He-fuelled campaign must be responsible for outer layer from
Film structure may be different allowing trapping of large amount of D

15. Tile 3: Deposition layer fills up the holes of the W layer
G3B
top
bottom
Tile 3: Deposition layer fills up the holes of the W layer

16. Micro-analysis cross section
Goal: Composition of layers of 100µm thick via micro beam analysis of polished cross sections. (% level of main constituents: C, D, O, Be and SS, spatial resolution of a few μm)
D2 mapping
(Tekes, Likonen and Emmoth, VR)

17. Tile 1-5, sputter cleaned

18. Tile 1-5 before and after sputter cleaning

19. Erosion/deposition at the outer divertor
Task Force E
JET
Tile 8
Tile 7
Tile 6
Shadowed region
Picture from previous divertor campaigns in JET as follows:
Erosion at outer divertor wall (tiles 7 and 8) [contrast to inner]
~200 μm deposition on sloping part of tile 6 [same as inner]
No significant deposition in shadowed corner [contrast to inner]
New data from MkII-SRP campaign from
13C puffing
IR measurements
Analysis of tiles
Deposition monitors, louvre clips from shadowed area

20. Deposition at outer divertor
Task Force E
JET
Deposition at outer divertor
4 weeks reversed field operation gave deposition at outer divertor (clear from the film effect in the infra-red camera)
During methane puffing local re-deposition observed
Deposition in outer shadow region [c.f. inner]:
Film on Deposition monitor slits ~20 μm [c.f. 90 μm]
Deposit inside monitor box 18 μm [c.f.35 μm], or atoms cm-2 [c.f atoms cm-2]
Film on tile (SIMS) 8 μm [c.f. 80 μm]
Film on tile (section) 40 μm [c.f. 120 μm]
Louvre clips off-gas 0.49 MBq/day [c.f MBq/day]
Tile 8
Tile 7
Tile 6
Shadowed region

21. G7B 8 7 6 5 4 3 2 1a 1 0a

22. W Erosion Outer divertor: SEM images Inhomogeneous erosion
Full erosion of W in some places
(IPP, Majer)

23. 13C-methane puffing experiment in 2004
Task Force E
JET
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 molecules 13C-methane puffed in outer divertor from 48 locations
Approximate line of W-stripe is shown as white dashes

24. Task Force E
JET
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

25. Amounts of 13C measured on divertor tiles by SIMS and IBA
Task Force E
JET
Tile 1
Tile 3
Tile 4
Tile 8
Tile 7
Tile6
Amounts of 13C measured on divertor tiles by SIMS and IBA
Note: Measurements on one poloidal line have been extrapolated, assuming toroidal symmetry
Tile Number 13C amount % % %
SRP ? % %* %
Total %
* based on average of two poloidal scans
SRP

26. Local deposition of 13C on G3B
Total number deposited 13C in this area is ~215 x1018 atoms
Tungsten stripe
13C injection
20mm
Cores cut for SIMS analysis
19-23(max) x1018 atoms/cm2
x1018 atoms/cm2
x1018 atoms/cm2
7-9.9 x1018 atoms/cm2
1-6.9 x1018 atoms/cm2

27. Modelling of the 13C puffing for the inner divertor
Task Force E
JET
Modelling of the 13C puffing for the inner divertor
Method
EDGE2D follows injected 13C atom trajectories with NIMBUS
EDGE2D ELM model of Kallenbach used (modified for smaller ELMs)
effects of sputtered carbon and re-erosion not included
impurity transport coefficients in private flux region chosen 10x SOL value
SOL flows in main chamber created by external force, classical drifts important in private flux region
3 paths dominate the 13C migration
most of carbon re-deposited on the outer target
a few % migrates via the main chamber SOL to the inner target (as also seen on a reciprocating probe at the top of the machine), and accounts also for the deposition on the inner baffle
a few % migrates via the private flux region by action of ExB drift to vicinity of inner strike point

28. J Strachan modelling for 13C experiment

29. Conclusions from 2004 samples
Task Force E
JET
Conclusions from 2004 samples
Deposition at the inner divertor is not sensitive to wall temperature
Significant erosion of W-markers has been observed at the outer divertor, of interest to the ITER-like Wall Project at JET.
Infra-red temperature measurements clearly show when thin films are forming at the outer divertor
Some deposition occurred in shadowed region at outer corner in , but the balance between erosion and deposition in this region requires further exploration
13C-methane was puffed at the outer divertor in 2004, and preliminary modelling shows reasonable agreement with deposition at inner divertor

30. 72μm
67cm3
26μm
7μm
44cm3
10μm
10μm
38μm
464cm3
33μm
19cm3
99cm3
41μm
105cm3
24cm3
60g on louvre
233cm3
17cm3
18μm
300μm
32μm

31. Tile analysis programme for tiles removed in the 2007 shutdown
Objectives:
Distribution of 13C injected in April 2007 at outer mid-plane
Erosion of W-coatings in critical areas for ILW
Erosion/deposition behaviour to compare with QMB data
Results of rotating collector experiment (inc. Be evaporation)
Mirror tests for ITER
C-redeposition at load-bearing tile

32. Cross-section of JET

33. JET-HD divertor 2005-

34. Quartz Micro-balance at the inner divertor

35. JET ITER-Like Wall Update on materials, timescales
Development of W coatings on CFC
Be coatings on inconel
Be markers

36. View inside JET

37. Beryllium Coatings on Cast Inconel (I)
Evaporated 8 mm Be coating on inner wall Inconel cladding
Estimated maximum load in JET: 0.5 MW/m2 in 20 s corresponding to 10 MJ/m2
Steps in the material qualification process:
Optimisation of the deposition process (Nucl. Fuel Plant, Romania).
Pre-characterisation of layers: purity, structure, uniformity.
High Heat Flux testing (Forschungszentrum Jülich).
Characterisation after testing.
HHF testing in JUDITH to determine the layer durability limits:
Screening test by stepwise increase of power density: 0.4 – 3 MW/m2.
Cyclic test: 50 consecutive loads of 1.0MW/m2 for 10 s.
Message: No damage to layers exposed to the energy load of 19.8 MJ/m2.
200
700
5 mm
Original surface
Tested: 1.8 MW/m2, 11 s
Test: 1.8 MW/m2, 11 s

38. Beryllium Coatings on Cast Inconel (II)
Energy density [MJ/m2]
extrapolation, ~11 s pulse
on 3.5 mm Inconel case
~ 11 s pulses,
thickness 3.3 ~ 3.6 mm
6.2 s pulse, thickness 4 mm
~ 11 s pulses, thickness > 4.0 mm
Surface Temperature versus Energy Density
Temperature [oC]
SUMMARY OF RESULTS:
High uniformity and purity of coatings (oxygen only in a thin surface layer).
Layers survive power loads of 2.55 MW/m2 in 6.2 s (18.1 MJ/m2)
Melting of beryllium observed above 3 MW/m2.
No damage by 50 thermal cycles of 1 MW/m2 for 10 s each (10 MJ/m2 pulses).
Conclusion: The layers meet operational requirements for JET-ILW.

39. Erosion of Beryllium Coatings on Cast Inconel: Exposure of Be to Deuterium Plasma in PISCES (UCSD)
GA & Romanian Be coatings show increased YBe’s at higher Eion compared to Poly Crystalline(PC)-Be.
PISCES
PC-Be data scaled (a) to Eckstein’s value
D.Nishijima, J.Hanna, R.Doerner

40. Development of Beryllium Marker Tiles (I)
AIM: The assessment of beryllium erosion from the main chamber wall (limiters)
30 mm
28 mm
Be coupon with marker coating.
For HHF test
coupons are with a hole for a thermocouple.
Beryllium Tile (3 cm)
Nickel interlayer (2-3 mm)
Be layer (7-9 mm)
Steps in the R & D process
Production of optimised layers by Thermionic Vacuum Arc method
High Heat Flux testing
Broad characterisation of layers before and after testing.
Main Result of HHF test:
Layers withstand without damage 4.5 MW m-2 for 10 s.

41. Beryllium Marker Tiles (II)
SIMS depth profiles
Fresh
Be test coupon
with marker layers
Topography of Be coating
After HHF
test

42. Remaining Work: Produce and Install Tiles in JET Inner Wall Structure with Location of Marker Tiles

43. Conclusions Analysis of tiles removed in 2004 shutdown almost complete
Analysis has started on a new poloidal selection of tiles removed in 2007
Preparations are in hand for the ILW installation in , including solid Be and W tiles, Be coatings on inconel, and marker tiles.