Report on SEWG ITER like Material Mix V. Philipps on behalf of SEWG working group* • Decided during EU -TF meeting Cadarache, 2005 • Work programme defined in a first SEWG meeting (June 2006 , IPP Garching ) * presently: P. Coad, M. Rubel, J. Likonen, K. Nordlund, A. Kreter, A. Litnovsky, A. Kirschner, D. Borodin, S. Droste, C.Linsmeier, K. Krieger, M. Mayer, U. von Toussaint, K. Schmid, J. Roth, C. Lungu, R. Doerner, M. Baldwin, E. Fortuna, I. Uydenthoven EU Plasm a-W allInteractionsTask Force V.Philipps, EU TF Meeting, Slovenia, 13-15 Nov 2006
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Report on SEWG ITER like Material Mix V. Philipps on behalf of SEWG working group*
• Decided during EU -TF meeting Cadarache, 2005
• Work programme defined in a first SEWG meeting (June 2006 , IPP Garching )
* presently: P. Coad, M. Rubel, J. Likonen, K. Nordlund, A. Kreter, A. Litnovsky, A. Kirschner, D. Borodin, S. Droste, C.Linsmeier, K. Krieger, M. Mayer, U. von Toussaint, K. Schmid, J. Roth, C. Lungu, R. Doerner, M. Baldwin, E. Fortuna, I. Uydenthoven
EU Plasma-Wall Interactions Task Force
V.Philipps, EU TF Meeting, Slovenia, 13-15 Nov 2006
…The aim of the SEWG is to improve our knowledge and initiate new experiments and modelling for mixed materials formed on deposition dominated areas or in the narrow surface layer on erosion areas for the ITER like material mixfor the ITER like material mix.
The focus of the work is to clarify in more detail important physical properties of mixed layers which are of relevant for PWI processes in fusion devices:
• Chemical composition• Thermo-mechanical properties • Hydrogen retention properties• Erosion behaviour, including alloy formation and thermal
decomposition
The work of the SEWG is not to analyse the underlying processes of material erosion and its migration…. This is the main focus of other working groups…..
EU Plasma-Wall Interactions Task Force
V.Philipps, EU TF Meeting, Slovenia, 13-15 Nov 2006
Motivation
Systems• Be on W & C • W on C • C on W• W & C on Be
Tertiary systems (mixed Be, C, W ,O)
Oxygen important additional impurity
EU Plasma-Wall Interactions Task Force
V.Philipps, EU TF Meeting, Slovenia, 13-15 Nov 2006
The most important topics
EU Plasma-Wall Interactions Task Force
V.Philipps, EU TF Meeting, Slovenia, 13-15 Nov 2006
Be on C (with O)
•Ion beam implantation , C films on Be (IPP Garching)
•JET Be –C experiences : Be limiters, Be-C mixed layer deposition in inner divertor (UKAEA, Tekes, VR, FZJ, SEK )
•Pisces Be seeded plasma interaction with C (Pisces, IPP)
•Modelling (IPP, FZJ)
EU Plasma-Wall Interactions Task Force
V.Philipps, EU TF Meeting, Slovenia, 13-15 Nov 2006
Be on C (with O)
1. Ion beam data C+ , CO+ → Be
P. Goldstrass, C. Linsmeier : formation of mixed layers and compounds on beryllium due
to C+ and CO+ bombardment, J. Nuc. Mat. 290
P. Goldstrass, W. Eckstein, Ch. Linsmeier: Erosion of beryllium and deposition of carbon and oxygen due to bombardment with C+ and CO+ ions, J. Nuc. Mat. 266
2. Thermal annealing: a-C:H on Be
J. Roth , W.R. Wampler, W. Jacob: release of deuterium from carbon-deuterium films on beryllium during carbide formation and oxidation, J. Nuc. Mat. 250
Annealing of a-C:H on Be J. Roth , W.R. Wampler, W. Jacob, J. Nuc. Mat. 250
at ~ 490C, Be - C mixing starts
a-C:H deposited on Be
At 560C, Be2C fully formed, D is thermally released
EU Plasma-Wall Interactions Task Force
V.Philipps, EU TF Meeting, Slovenia, 13-15 Nov 2006
heatingC
D
C
D
C
Be
Be
Be
no significant carbon dissolution in bulkstable surface carbide at elevated temp.
C on Be (with O)
Oxidation is determined by diffusion of Be through BeO, (confirmed by 16,18O isotope experiments )
EU Plasma-Wall Interactions Task Force
V.Philipps, EU TF Meeting, Slovenia, 13-15 Nov 2006
O on Be
Oxide layer before
Oxide layer after
No significant
reaction at 375 C
oxidation starts not before 400C
Be
BeO
O2
BeO
Oxidation of Be in O2 ( 660mbar )
EU Plasma-Wall Interactions Task Force
V.Philipps, EU TF Meeting, Slovenia, 13-15 Nov 2006
Be – O interaction
Small temperature window exists at which C layers are oxidised while the Be substrate is not
300 C < T < 375 C
With C and O simultaneously impacting on Be, BeO is more stable and favorised than Be2C
( C. Linsmeier)
Atomic oxygen:
interaction with binary metal-C systems
and ternary metal—C—O systems
Be—W system:
reaction kinetics of alloy formation
reactivities with C, O
Hydrogen inventory:
clean and oxide/carbide covered beryllium
tungsten systems (W, Be—W)
Be—W ternary (C, O) systems
Structural investigations:
STM studies of carbon films on metals (Ni, Be, W)
modifications due to deuterium ions
PISCES collaboration:
EFDA task TW5-TPP-CARWBER
Current and planned IPP Garching lab activities on fundamental surface processes:
Ch. Linsmeier et al.
Codeposition of Be with C and O on collector probe after first JET_ Be evaporation (1989)
LCFS
SOL collector probe
30 40 70 (mm)
More BeO
More Be2C
P. Coad et al , Journ. Nucl. Mat. 176 & 177 (1990) 145
EU Plasma-Wall Interactions Task Force
V.Philipps, EU TF Meeting, Slovenia, 13-15 Nov 2006
Be–C- O: previous JET experiences
Be2C formed close to LCFS and BeO deeper in SOL
Parameter: impinging flux composition, temperature (?)
0
EU Plasma-Wall Interactions Task Force
V.Philipps, ITPA Toronto 2006
Material transport ways in JET
1: C rich layers built up in shots with smaller Elms, only some C is transported further
2. In large ELM shots, C (not Be) is released and transported towards the PFR (tile4) (thermal decomposition)
A stable Be-C-O layer remains on tile 3
C-layer built up on the divertor floor
The layer is decomposed by plasma impact on tile 4, more effective in large Elmy shots than in L mode
See also R. Pitts, TFE report
CBe
Present view : post mortem analysis, QMB & spectroscopy
1
2
45
To investigate more:
Chemical composition and stability of Be-C-O mixed layer on PFC sides (formed after many thermal treatments on tile 1,3 )
Mechanism of ELM induced transport: erosion, ablation, decomposition
New measurements done in SCK CEN Belgium on JET inner divertor deposited layers
EU Plasma-Wall Interactions Task Force
V.Philipps, ITPA Toronto 2006
XPS on Be coated C tiles
First results obtained at SCK•CEN
Sven Van den Berghe, Inge Uytdenhouwen, Paul Coad
Escalab 250 surface station can handle Be and T
contaminated samples
monochromator Al K(spot 0.1 – 1 mm)
electron detectorimage detector
X-ray guntwin Al, Mg anode, ~1.2-1.4 keV
analyser (max. res. 0.018 eV)
transfer armUV lamp
camera
electron gunspatial res. ~100 nm
analysis chamberP~10-11 Bar
preparation chamber
x,y,z stage
ion gun, Ar
Be-metalBe-carbide
Be-O
Sputter XPS of JET inner deposit
Only about 1 nm sputtered
XPS results on JET tile 3
Be 1s
XPS shows large contribution of BeO with some Be2C and Be
Further XPS analysis is planned across the whole layer (cross sections, UKAEA, SEK, FZJ)
Remark: in JET the Be/O flux ratio is about 1 or below , thus Be can find enough oxygen to form BeO through the whole layer?
EU Plasma-Wall Interactions Task Force
V.Philipps, ITPA Toronto 2006
Used Be JET limiter & divertor tiles (1989-1992) are analysed again (M. Rubel, VR Sweden)
EU Plasma-Wall Interactions Task Force
V.Philipps, EU TF Meeting, Slovenia, 13-15 Nov 2006
Be – C system: Pisces experiments
Be
C
D
Be
Issues
Be-C layer formation(Be2C)
Diffusion of C in Be2C,
Thermal stability
Influence of oxygen
Be re-erosion by D impact Thermal decomposition
Enhanced Be re-erosion (?)
Important EU-US co-operation to study the dynamics of the Be-C system (simulate ITER conditions at lower C- target )
To analyse: reduction of chemical erosion due to
Be surface coverage
change of chemistry
EU activities
Experiments and surface analysis, IPP (K. Schmid, R. Pugno)
Modelling (FZJ, Kirschenr, Borodin)
EU Plasma-Wall Interactions Task Force
V.Philipps, EU TF Meeting, Slovenia, 13-15 Nov 2006
Be – C system: Pisces
Pisces data show a very promising strong reduction of carbon chemical erosion
R. Doerner PSI 17
10-3
10-2
10-1
100
0 100 200 300 400 500 600
w/o H.P. (20060322)exponential fit for w/o H.P.w/ H.P. (20060323)exponential fit for w/ H.P.
Time [s]
BeII/ne ~ 0.13 %
Be/C ~ 17 sec
Be/C ~ 83 sec
R. Pugno P 17
• Strong decrease of CD light • Pulsing to Tsurf ~ 1200-1400ºC
(so far) decreases chemical erosion mitigation time
• Be2C decomposes at ~ 2100ºC
D. Nishijima et al., PSI 17
Pisces empirical chemical erosion suppression time scaling law
tCDscale [s] = 1.0e-7 cBe+
-1.9±0.1 Ei0.9±0.3 Γi
-0.6±0.3 exp(4.8(±0.5)x103/Ts)
cBe+ Be concentration
Ei I incident ion energy,
i Plasma flux
Ts Temperature
EU Plasma-Wall Interactions Task Force
V.Philipps, EU TF Meeting, Slovenia, 13-15 Nov 2006
Be – C system: Pisces
• Further benchmarking of scaling
• Influence of higher temperature excursions
• Influence of oxygen
• Modelling (Ero- Tridyn & others): extrapolation to ITER
Ongoing cooperation with IPP and FZJ
Future Pisces tasks
• At RT, Be-rich mixed Be/C/O and C layers retain deuterium at similar levels
• Only at higher temperature (> 400-500K) Be-rich layers have significant less retention
• Codeposited Be/C layers in PISCES-B are Be rich
• Influence of oxygen to investigate more
The other critical question is the level of fuel retention in mixed co-deposited Be –C (O) layers
EU Plasma-Wall Interactions Task Force
V.Philipps, EU TF Meeting, Slovenia, 13-15 Nov 2006
Be – C system: Pisces
Ongoing work on Pisces witness probe and target post mortem analysis (Pisces, IPP)
Lab ion beam Be implantation experiments for fundamental processes (Pisces, IPP)
EU Plasma-Wall Interactions Task Force
V.Philipps, EU TF Meeting, Slovenia, 13-15 Nov 2006
Be – W system
Be – W interaction is of similar critical importance for ITER
Activities
• W deposition on Be → annealing in vacuum (IPP)
• Be deposition on W → annealing (IPP)
• Be seeded Pisces plasmas on W (Pisces, IPP, FZJ )
W
A major question for the JET ITER like wall project
EU Plasma-Wall Interactions Task Force
V.Philipps, EU TF Meeting, Slovenia, 13-15 Nov 2006
Be – W system
Various parameters determine the possible formation of Be-W alloys:
• Be/D flux ratio to the target (and other impurities, C,O)
• Target temperature (competition of Be-W formation with sublimation, dynamics of alloying process )
• Re-sputtering of Be from Be-W mix (Be2W) and freshly deposited Be
Further experiments and modelling ongoing
Lab work (IPP)
Cooperation with Pisces (IPP)
Modelling (IPP, FZJ , Tekes, Uni. Marseille)
EU Plasma-Wall Interactions Task Force
V.Philipps, EU TF Meeting, Slovenia, 13-15 Nov 2006
W – C system
W – C interaction also important for JET wall project
C WC W
W carbide forms at interface by diffusion of C in W (temperature activated)
C diffusion in W-C much slower , reduces further carbide formation
W-C has reduced melting point and is more brittle
Guideline for JET wall project: Tmax < 1600C
More information and modelling needed
Further experiments in IPP, FZJ , Slovenia
Modelling: IPP, FZJ, Tekes
EU Plasma-Wall Interactions Task Force
V.Philipps, EU TF Meeting, Slovenia, 13-15 Nov 2006
W – C system
Investigated binary carbon-metal systems:
W, Be, Fe, Ni, Ti, (Si)
• carbide monolayer at interface
• carbide formation (one or more phases) at elevated temp.
• carbon dissolution in metal bulk
C. Linsmeier at al
Existence of WC, W2C, W2B has been identified on TEXTOR W VPS layers after large temperature excursions
EU Plasma-Wall Interactions Task Force
V.Philipps, EU TF Meeting, Slovenia, 13-15 Nov 2006
W – C system
New contribution from IPPLM, Association Warsaw (M. Psoda, E.Fortuna )
VPS layers on TEXTOR graphite tiles after temperature excursions: formation of a new the W-Re sigma phase
Transverse cracks along the Re/ W-Re boundary;
Carbon present between sigma W-Re and VPS tungsten coating.
Before After exposure
Fortuna et al., PhysicaScripta, submitted
Modelling activities
Surface models:
• Sputter and flux balanced models (IPP, FZJ)
• Tridyn surface models in combination with ERO (FZJ, IPP)
• MD and QM modelling of chemistry, reflection and erosion (Tekes, Uni.- Marseille )
EU Plasma-Wall Interactions Task Force
V.Philipps, EU TF Meeting, Slovenia, 13-15 Nov 2006
Modelling
ERO modelling (A. Kirschner, D. Borodin. S. Droste )
PISCES: chemical erosion &beryllium co-deposition carbide formation
- TEXTOR: 13CH4 injection (graphite and W limiter) local transport of
deposited carbon, W-C mixing effects with TriDyn
- JET: net-erosion of W stripe in outer divertor
ITER modelling
- Target lifetime and tritium retention under influence of Be co-deposition
- Be limiter erosion during ramp phase
EU Plasma-Wall Interactions Task Force
V.Philipps, EU TF Meeting, Slovenia, 13-15 Nov 2006
Modelling
A.Allouche et al CNRS and Université de Provence, MarseilleElectronic structure of beryllium metal surfaceGraphite surface reactivity (co-op with P. Krstic)Hydrogen retention and recombination on beryllium surfacesBeryllium - rare gases interaction (EFDA task)Beryllium on tungsten, mixed Be/W materials (R. Doerner)Carbon on/in beryllium, first steps of Be2C formation ( Linsmeier)
EU Plasma-Wall Interactions Task Force
V.Philipps, EU TF Meeting, Slovenia, 13-15 Nov 2006
Modelling
MD Modelling: Nordlund, University of Helsinki
•WC mixed materials in ITER
• Main findings:
–chemical sputtering of WC even for very low H bombarding energies
–preferentially sputtering of C is bombardment of W by C and H: dynamic balance of WC formation and erosion
• Good agreement with experiments by Plank&Eckstein
Future: developing an interatomic potential for the quaternary Be-W-C-H system
EU Plasma-Wall Interactions Task Force
V.Philipps, EU TF Meeting, Slovenia, 13-15 Nov 2006
Modelling
EU Plasma-Wall Interactions Task Force
V.Philipps, EU TF Meeting, Slovenia, 13-15 Nov 2006
Summary and outlock
Be-C and Be-W interaction is a main task and further work important
Pisces, JET Be-C data, Lab work
Modelling (IPP, FZJ, Tekes, Un. Marseille )
(JET ILW project)
W-C system: Dynamics of W- C carbide formation
Lab data, TEXTOR and AUG data
Oxygen important residual impurity
Ternary systems
Modelling: understanding of fundamental processes and extrapolations to ITER conditions
CONCENTRATION RATIO: BERYLLIUM - TO - CARBON
1
2
3
45 6
78 9 10
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
DIVERTOR TILE (POLOIDAL DIRECTION)
Be
/ C
Inner Outer
Be/C ratio JET MKIIA divertor tiles
JET: codeposition of Be, C &O leads to (stable) Be-C-O layers on plasma viewing sides of inner tiles, while the excess of C is released and transported to shadowed areas
EU Plasma-Wall Interactions Task Force
V.Philipps, EU TF Meeting, Slovenia, 13-15 Nov 2006
Be–C- O: previous JET experiences
Topics Fusion device Lab- experiment Modelling
Be-W interaction
Pisces*Be/W target interaction (spectroscopy, post mortem analysis)
IPP, MEC :Preparation of Be/W systemsCharacterisation of Be/W properties &alloy
FZJ: ERO-Tridyn for Pisces Be/W experiments IPP: mixing modellingTekes: MD modelling of erosion/deposition
Be-C interaction
JET/Tekes/VR Analysis of Be/C redeposited layers: composition, chemical state, hydrogen retentionPisces * : Be/C arget interaction (spectroscopy, post mortem analysis
IPP, MEC :Preparation of Be/C systemsCharacterisation of Be/C properties (thermal stability, H retention ,…(EFDA technology task RETMIX)
FZJ: ERO-Tridyn for Pisces Be/C experiments IPP: mixing modelling Tekes: MD modelling of erosion/deposition
W/C interaction AUG: post mortem analysis of W/C layers, in situ spectroscopyFZJ: dedicated W/C mixed material experiments in limiter locks
Slovenia Preparation of W/C mixed systems & characterisation
FZJ: ERO-Tridyn for Pisces Be/C experiments IPP: Tridyn and other mixing modellingTekes: MD modelling of erosion/deposition
Dynamics of layer formation (erosion/deposition) under multispecies impact
FZJ: dedicated multispecies mixed material experiments in limiter locks and in situ spectroscopy
IPP: Dual beam experiment FZJ: ERO-TridynIPP: Tridyn and other mixing modelling Tekes: MD modelling of erosion/deposition
EU Plasma-Wall Interactions Task Force
V.Philipps, EU TF Meeting, Slovenia, 13-15 Nov 2006