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JET PFC Analysis, TFFT and the ILW

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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.

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