EUPWI Task Force

1
EU-PWI Task Force EFDA Plasma Edge Technology
Programme

• Alberto Loarte, Joachim Roth, Emmanuelle Tsitrone

2
Outline

• Background to EFDA Plasma Edge Technology
  Programme and Integration with EU-PWI Task Force
• 2. Description of Existing Tasks Status
• Details to be found in http//efdasql.ipp.mpg.de/
  efdatpp
• 3. Tasks Launched in 2006 Programme
• 4. Discussions of Priorities for 2007 Programme
  (new EFDA)

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Background

• Need of fundamental Understanding of PWI
  Processes
• Well defined Laboratory Experiments
• Specific Modelling and Extrapolation to ITER
• Contributions from Associations without
  voluntary Physics Programme
• Financial Volume (2005) 1.3 M(20 sub.) 5.1.a,
  475 k(40 sub.) 5.1b
• (Financial Volume (2006) 3.4 M(20 sub.) 5.1.a,
  285 k(40 sub.) 5.1b)
• EU Task Force aims to better integrate
  Technology and Physics Aspects of the EFDA
  Plasma Edge Technology Programme

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Integration with EU-PWI TF Topics (I)
Tasks in 2002/2003/2004/2005 1. Erosion
behaviour ? Chemical Erosion of C by D/Be,
TW2-TPP-ERDEP (v) (EU-US) ? Sputtering of W and
Be, TW3-TPP-ERTUBE (v) ? SEWG ? Chemical Erosion
of C, TW4-TPP-ERCAR (v) ? SEWG ? C/W/Be
mixed-material formation, TW5-TPP-CARWBER
(EU-US) 2. Material transport and
re-deposition ? Flake Formation from Deposits,
TW2-TVM-CFC2 (v) ? Scavenger Technique,
TW3-TPP-SCAVOP (v) ? SEWG ? CxHy Formation and
Re-deposition in ITER Geometries TW4-TPP-TRIDEP
(v) ? Erosion/deposition metal wall C
divertor TW5-TPP-TILCAR (v) ? Midplane and
Divertor W macro-brush studies in ASDEX-Upgrade
(v) UT4-TUNAUG UT5-MBWAUG (v) Already
reported at previous meetings
(v) Reported this year
5
Integration with EU-PWI TF Topics (II)
3. Fuel recycling, retention and removal (2
SEWGs) ? Optimisation of He-O Glow for C-H
removal, TW5-TPP-HEGLO (v) ? T removal by
non-O2 oxidative methods, TW4-TPP-TRIREMA-B
(v) ? Characterisation of Oxidised PFCs,
TW5-TPP-TILCAR (v) 4. Off-normal heat loads
(SEWG) ? Modelling of Disruptions and ELMs,
TW3-TPP-DISELM (v) ? Validation of ELM Damage
Modelling, TW3-MATDAM (v) (EU-RF) ?
ELM-Disruption exposed Target Characterisation,
TW4-TARCAR (v) (EU-RF) ? W and CFC damage and
plasma evolution in ITER, TW5-TPP-ITERTRAN (v)
? Modelling of Be damage under
Disruptions/ELMs, TW5-TPP-BEDAM (EU-RF)
6
Integration with EU-PWI TF Topics (III)
5. Edge modelling, erosion and deposition
modelling ? Improvements to ERO Code and ITER
Modelling, TW3-TPP-ERMOD (v) ? MD Modelling of
Erosion Processes, TW4-TPP-CARWMOD (v) ? W
Erosion and Edge Plasma Contamination in ITER,
TW5-TPP-TUNMOD (v) 6. Edge and SOL physics ?
Improvements to B2-Eirene for ITER Modelling,
TW3-TPP-NEUTMOD (v) ? Modelling of n-n and n-g
effects in ITER divertor, TW5-TPP-ITERNEUT
(v) 7. Task force relevant diagnostics ?
Speckle Interferometry for Erosion, TW0-T438/01
(v) ? Laser Ablation Techniques for Film
Deposition, TW3-TPP-ERDIAG (v)
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Description of Tasks and Status (I)
ERTUBE Exposure of W macro-brush elements to
plasmas fuel retention in TEXTOR and FTU
W Mo macrobrush limiters have been exposed to
TEXTOR plasmas in the far SOL (deposition
studies) and at separatrix for power load studies
D deposition inside brush correlated with C
deposition with typical decay lengths of 2 mm
W macrobrush is effective in preventing melt
layer loss caused by jthermX B forces
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Description of Tasks and Status (II)
ERTUBE Exposure of W macro-brush elements to
plasmas fuel retention in TEXTOR and FTU
W macrobrush probes have been exposed to C-free
plasmas in FTU limiter
Surface contamination by C during macrobrush
manufacturing most likely cause of larger than
expected retention
D retention determined by outgassing and
typically 10-4 of the incident flux (low but
10 times larger than expected)
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Description of Tasks and Status (III)
TW4-UT4-TUNAUG TW5-UT5-MBWAUG Exposure of W
macro-brush element in the SOL and divertor in AUG
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Description of Tasks and Status (IV)
ERCAR Characterisation of thermal response of
Carbon PFCs exposed to plasmas and of CFC under
repetitive laser loads

• AUG samples have been characterised
• Samples from erosion dominated areas maintain
  unexposed properties
• Samples from deposition dominated areas covered
  by low conductivity layers

Exposure of NB31 to 1000 under threshold laser
loads does not cause deterioration of thermal
properties nor observable surface damage
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Description of Tasks and Status (V)
TILCAR Characterisation of erosion/redeposition
in divertor tokamaks

• Analysis of long term erosion/deposition in AUG
  carried out
• In 2004 13CH4 (1.4 1022) was puffed at outer
  midplane in 5 SN Type l ELMy H-modes in H

Marker coating on 3 divertor and 4 limiter tiles
produced for AUG 2006 campaign (C- 2 mm, W-3 mm
on Re interlayer)

• Size of 13C deposition depends on substrate
  (12 on C, 6 on W)
• 12 of injected 13C ? Divertor
• 11 of injected 13C ? Inner wall

Measurements provide basis for understanding of
erosion/deposition balance in divertor tokamaks
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Description of Tasks and Status (VI)
UT4-TUNAUG/UT5-TUNAUG Development and testing
of W coatings for AUG
W coated (200 mm) tiles installed at ICRH
protection limiter in 2004/2005
New W coatings with high and low porosity
developed (180-210 mm) and screen-tested in
GLADIS facility to 23.5 MWm-2

• Thermal cycling and tests in ASDEX Upgrade
  still outstanding
• Delay caused by wrong interlayer (Cr vs.Re)
  used in first coating series (Plansee)

Coatings delaminated (wrong C surface treatment)
W melted under power load but only minor
restrictions to plasma operations
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Description of Tasks and Status (VII)
TRIDEP CxHy formation and deposition in remote
areas (PSI-2)

• Deposition experiments in Ar show larger rates
  than state-of-the-art ERO modelling
• CH emission shows unexpected local patterns at
  higher ltnegt (influenced by Vbias)
• Experiments to quantify H erosion of C-H
  re-deposits carried out

CH emission ne 2.0 1017 m-3
CH emission ne 2.5 1018 m-3
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Description of Tasks and Status (VIII)
HEGLO Removal of hydrocarbons by He/O2 plasmas
in TEXTOR and ASDEX Upgrade TILCAR
Characterisation of TEXTOR He/O2 exposed
components

• HeO GDC applied to TEXTOR ? C removal rate of
  2.0 1019 C/s weakly dependent on He
  concentration (30-100) ? Recovery weekend D2
  GDC Boronisation
• ICRH HeO discharges ? Most C released after
  ICRH pulse, with 110 duty cycle similar rates to
  HeO GDC ? antenna pressure pumping limits
  removal ? Recovery overnight D2 GDC

Integral TEXTOR carbon redeposition rate 2.71020
C/s
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Description of Tasks and Status (IX)
HEGLO Removal of hydrocarbons by He/O2 plasmas
in TEXTOR and ASDEX Upgrade TILCAR
Characterisation of TEXTOR He/O2 exposed
components

• Laboratory prepared aC-D layers and in-situ
  boronised layers (aB-D-C layers) were exposed to
  HeO GDC (removal rate gt 1014 C cm-2s-1 0.1
  mm/h) for aC-D layers
• D removal rates from aB-D-C layers are a factor
  of 10 lower than from aC-D layers

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Description of Tasks and Status (X)
HEGLO Removal of hydrocarbons by He/O2 plasmas
in TEXTOR and ASDEX Upgrade TILCAR
Characterisation of TEXTOR He/O2 exposed
components

• HeO GDC on aC-H layers AUG layers D
  removal from real films 10 times lower than for
  lab films 1013 C cm-2s-1 0.01 mm/h. No
  removal of deposits in 3 mm gaps
• Oxidation of W reversible by exposure to H
• Tests in AUG consistent with lab tests but
  arcing problems due to B layers on W (C removal
  rate of 6.0 1018 C/s)

HeO GDC laboratory tests with real AUG tiles
HeO GDC in AUG showing arc traces
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Description of Tasks and Status (XI)
TRIREMA O3 oxidation of hydrocarbon deposits in
ITER-relevant conditions

• Oxidation in ozone achieves rates within the
  ITER requirements (1 mmh-1) and operating
  temperature (T lt 250 oC) for fusion application
  graphites
• Rates of 0.5 mmh-1 achieved for TEXTOR flakes
• Main problem is that oxidation rates of flakes
  and substrate are similar

1 mmh -1
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Description of Tasks and Status (XII)
TRIREMB Removal of fuel with alternative
methods and comparison to O2

• Oxidation by O2/ Nitric Oxide (NO) of Hard Films
  TEXTOR flakes (H/Dgtgt1) shows that NO
  oxidation is slower than O2 and does not produce
  H2 (260 oC _at_ 2 torr)
• Isotope interchange on flakes from ASDEX Upgrade
  activated by H2O2 does not occur

Activation of samples with H2O2 H/D interchange
Candidate reaction NO H ? NOH H ? NO H2
Some production of CO with NO but no enhanced
production of H2
H2O2 treated AUG flakes in H2 1 bar atmosphere
show release of H2, DH and D2 at similar
temperatures than in TDS
TDS
T(K)
HD
D2
H2
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Description of Tasks and Status (XIII)
MATDAM Validation of ELM Damage Modelling

• Experiments carried out in TRINITI plasma guns
• CFC and W targets exposed to 100 pulses at 0.5,
  1.0, 1.5 MJ/m2 Dt 500 ms (two higher levels
  beyond melting of W and sublimation of C)
• Analysis of target damage on-going (completed
  for 0.5 1.0 MJ/m2) ? TARCAR

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Description of Tasks and Status (XIV)
MATDAM Validation of ELM Damage Modelling

• CFC ? Damage is driven by preferential erosion
  of material above PAN fibres (fibre-matrix
  detachment) ? overheating an brittle destruction
  of material
• W macrobrush damage threshold ?melting of
  castellations edges layer displacement

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Description of Tasks and Status (XV)
TARCAR Characterisation of ELM-disruption
damage modelling

• Analysis of CFC W targets exposed to 100 small
  ELM ITER-like pulses in TRINITI plasma guns
• CFC ? enhanced erosion of PAN fibres fibre
  detachment already at 0.6 MJm-2
• W macrobrush shows edge melting and significant
  surface cracking at 0.8 MJm-2)

Before exposure
Before exposure
Cracking of W surface
Plasma stream
1.0 MJ/m2
Crack formation at edges of bundles
0.9 MJ/m2
Edge W melting displacement
PAN fibre erosion
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Description of Tasks and Status (XVI)
ITERTRAN Improved concepts for reduction of W
and CFC damage plasma evolution in ITER after
ELMs

• Optimisation of macrobrush geometry shows that
  minimum damage by melting and displacement is
  obtained with b 0.5 a (gap shadowing ??
  effective area)
• Modification of CFC structure to avoid PAN
  fibres parallel to surface decreases erosion
  damage (increases threshold energy for damage) by
  5 for 45o

EELMmax 0.5 MJm-2, Dt 0.1 ms
a 3o
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Description of Tasks and Status (XVII)
ITERTRAN Improved concepts for reduction of W
and CFC damage plasma evolution in ITER after
ELMs

• Transient evolution of plasma discharge after
  ELMs in ITER refined modelling ELMs by an
  increase of anomalous transport of factor 10
• Even for EELMmax lt 1 MJm-2 Dt 300 ms
  significant carbon production and expansion along
  the field with npedC 5 1020 m-3 after 2 ms ?
  Prad modelling in progress

nC after Dt 1.5 ms
nC after Dt 500 ms
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Description of Tasks and Status (XVIII)
TUNMOD W erosion and edge plasma contamination
in ITER

• W concentrations remain under 2 10-5 for any
  coverage level by W in ITER and high density
  operation (weakly influenced by seeding,
  Danomalous parallel flows)
• W concentrations during the limiter phase can
  reach very large values gt 1 unless Te,limiter
  lt 50 eV without impurity seeding (W
  self-sputtering runaway)

Low ne,sep
High ne,sep
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Description of Tasks and Status (XIX)
ITERNEUT Modelling of n-n and n-g effects in
ITER divertor

• Nonlinear effects (n-n n-g) and improved D2
  kinetics introduced in B2-EIRENE
• Opacity increases plasma density but total
  divertor source remains constant (larger
  recombination) ? different divertor dynamics but
  same divertor pressure
• Main impact on the ITER divertor caused by n-n
  and D2 D collisions (larger PDT for same peak
  divertor power load)

nD 5 1020 m-3
R-target recycling VR-volume recombination I
ionization (total) Iph photo-induced ionization

• Sionexcited gt Sionconventional

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New Tasks in 2006
(I)

• Material erosion and transport
• Erosion/Deposition in divertor tokamaks,
  TW6-TPP-CARTIL
• Material erosion and transport in ITER-like
  conditions, TW6-TPP-ERDEP
• Hydrocarbon sticking properties,
  TW6-TPP-CNDMSTICK
• 2. Fuel retention and removal
• ? Fuel removal from macro-brush structures,
  TW6-TPP-GAPOX
• Fuel retention in mixed-materials, TW6-TPP-RETMIX
• Fuel retention in ITER metallic PFCs,
  TW6-TPP-RETMET
• 3. Transient heat loads and control
• ? Experiments on W CFC under-threshold damage,
  TW6-TPP-REPELM
• ? Modelling of PFC damage and plasma evolution in
  ITER, TW6-TPP-DAMTRAN
• Analysis of Be-coated/Be-clad PFCs exposed to
  plasma guns, TW6-TPP-ANABE
• Coating by Be of W/CFC PFCs, TW6-TPP-BECOAT

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New Tasks in 2006
(II)

• 4. PWI and ITER modelling
• Modelling of mixed-materials formation,
  TW6-TPP-BETUNCMOD
• Modelling of erosion/redeposition balance in
  ITER, TW6-TPP-ERITERA-B
• 3-D modelling of SOL transport in ITER,
  TW6-TPP-SOLITER
• Modelling of ITER far SOL plasma (for ICRF
  coupling), TW6-TPHI-ICFCOUPL
• 5. Dust production and removal
• ? Evaluation of dust generation mechanisms in
  tokamaks, TW6-TPP-DUSTGEN
• 6. Task force relevant diagnostics
• ? Tests of dust measurement techniques in
  tokamaks, TW6-TPP-DUSTMEAS

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Money matters History and Facts
Budget allocated for TPP area of EFDA Technology
programme roughly constant since 2003 Real
allocated budget increases with time (by a factor
of 3-4 in 2006 !!!)
Increase of requested/allocated budget reflects
interest of EFDA management on PWI issues the
good work of EU-PWI Task Force!!
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Some ideas for 2007

• Mixed Materials Studies ? development of
  techniques for T removal from mixed materials
• In-situ spatially resolved diagnostic for
  erosion/redeposition measurements
• Diagnostics for in-situ T retention measurement
• Techniques for dust removal in tokamaks
• More ideas ?
• EFDA-PISCES-B collaboration

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EFDA-PISCES-B collaboration

• EFDA-PISCES-B collaboration research topics in
  2007
• Studies of CD4 seeding in Be containing plasmas
  impacting on a C and W target in steady state
  and under pulsed loads
• Studies of Be layers on W targets under steady
  and pulsed loads
• Studies of He/Ne/Ar interaction with C and W
  targets with Be-seeded plasmas
• Studies of redeposition in the witness plate (D
  content, changes in reflectivity of mirrors ?,
  etc.) during these experiments
• EFDA will provide long term ( 1 year) scientist
  to participate in experiments (mission expenses
  covered by Euratom mobility)
• Young dynamic and enthusiastic experimental
  physicist (post-doc)
• Knowledge of surface analysis and/or
  spectroscopic techniques
• To become Be worker (non-smoker no beard)
• CV to be sent to A. Loarte by 31-12-2006 ?
  Selection by 30-1-2007
• Start date in PISCES-B by spring 2007 (one month
  test period possible)

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Conclusions

• EFDA TPP Technology Programme is well integrated
  with EU-PWI
• Research Programme and producing ITER-relevant
  results
• As recognised by EFDA and ITER management
• Two major EFDA Collaborations with US (PISCES-B)
  and RF (TRINITI) on-going
• New large collaboration approved with RF
  (Kurchatov TRINITI) on Be damage under ITER
  transient loads ? EU staff to collaborate
  in-situ in the experiments (Euratom Mobility)
  EU industry to provide targets ( Be coated
  targets by MEdC) destructive analysis of
  targets to be done in EU labs
• Many Associations involved CEA, CIEMAT,
  ENEA-Frascati, ENEA- CNR Milano, FOM, FZJ, FZK,
  IPP, IPP.CR, IST, MEdC, MHST, ÖAW, TEKES and VR