eu plasma-wall interaction tf – meeting 27.10.-29-10-2008 - frascati sewg erosion & transport...

EU Plasma-Wall Interaction TF – Meeting27.10.-29-10-2008 - Frascati

SEWG Erosion & TransportS. Brezinsek

Institut für Energieforschung –PlasmaphysikAssoziation EURATOM-FZJ

Report of the Special Expert Working Groupon Chemical Erosion and (carbon) Transport

S. Brezinsek

TF-E

Institut für Energieforschung- Plasmaphysik, Forschungszentrum Jülich, EURATOM Association, Trilateral Euregio Cluster, D-52425 Jülich, Germany

with major contributions from SEWG members from the following associations …

CU, CNR

… group meeting in JET in July 2008 (joint with SEWG Fuel Retention and Fuel Removal)




Clarification of Chemical Erosion under ITER Divertor Relevant Conditions

PWI-08-TA-05/CEA/BS/01Determination of chemical erosion yield in Tore Supra, including gaps and redeposited layers.PWI-08-TA-05/CEA/PS/01Upgrade of spectroscopy diagnostic for chemical erosion characterizationPWI-08-TA-05/CEA/BS/02Molecular dynamic simulations of graphite surfacesPWI-08-TA-05/CIEMAT/BS/01Erosion of doped graphites and re-deposited layersPWI-08-TA-05/CU/BS/01Modelling the interaction of plasma with wall material (Be or W) with impurities (Be, B, O) and/or seeding gases (Ne, N2, Ar )PWI-08-TA-05/CY/BS/01PWI-08-TA-05/CY/PS/01Molecular dynamics (CPMD) simulations of carbon erosionPWI-08-TA-05/FOM/BS/01High ion flux exposure in pilot-PSI and PSI-II under ITER divertor plasma condition. Impact of seeding gases on erosion PWI-08-TA-05/FZJ/BS/02PWI-08-TA-05/FZJ/PS/02Impact of ELMs on chemical erosion in the JET divertor High ion flux exposure of graphite/ CFC in TEXTOR, pilot-PSI andPSI-II under ITER-relevant conditionsPWI-08-TA-05/FZJ/BS/03PWI-08-TA-05/FZJ/PS/03ERO modelling of erosion and material transport in tokamaks and linear devicesPWI-08-TA-05/IPP/BS/01PWI-08-TA-05/IPP/PS/01Joint MD/DFT simulation of carbon erosionPWI-08-TA-05/OAW/BS/01MD simulations of carbon erosionPWI-08-TA-05/UKAEA/BS/01Narrow-band spectroscopic 2D imaging of carbon erosion during ELMs in MAST

TASK AGREEMENT: WP08-PWI-05




Erosion, Transport and Deposition of First Wall Impurities

PWI-08-TA-06/CEA/BS/01Carbon balance in TS : evaluation of sources and sinks, including gapsPWI-08-TA-06/CEA/PS/01Modelling of C erosion /rede-position and fuel retention in TSPWI-08-TA-06/CEA/BS/02Monitoring of carbon deposited layers (IR, ellipsometry, thermal properties)PWI-08-TA-06/CIEMAT/BS/01Injection of hydrocarbons by molecular beam techniquesPWI-08-TA-06/CNR/BS/0113CH4 tracer injection in TEXTOR. Post-mortem tile analysis,spectroscopic analysis, local erosion/ deposition.PWI-08-TA-06/FOM/BS/01Modelling of erosion and re-deposition of graphite exposed to ITER relevant fluxes in Pilot-PSI with EROPWI-08-TA-06/FZJ/BS/0113CH4 tracer injection in JET and AUG. Post-mortem tile analysisPWI-08-TA-06/FZJ/BS/02Development of material tracers TMB and SiH4.PWI-08-TA-06/FZJ/BS/03Characterisation erosion / re-deposition of graphite PFCs at TEXTOR and marker probes at JETPWI-08-TA-06/FZJ/BS/04Development and testing of spectroscopic tools for the observation of carbon and beryllium and of QMBs for erosion/deposition measurements in TEXTOR and JETPWI-08-TA-06/FZJ/BS/05Modelling of erosion / re-deposition of graphite PFCs at TEXTOR and marker probes at JET. ERO code modelling of gap deposition. Coupling of the ERO code to molecular dynamics simulation codes and study of the formation of mixed-materials in ITER. Local erosion/ deposition (ERO) and plasma transport (EDGE2D, DIVIMP) modelling.PWI-08-TA-06/FZJ/PS/05ERO modelling of redeposition in gaps (TEXTOR,JET)13CH4 tracer injection in JET and AUG / Characterisation of graphite PFCs at TEXTOR and marker probes at JET





PWI-08-TA-06/IPP/BS/02Reflection properties of hydrocarbon radicals for ITER-like divertor conditions /Deposition of hydrocarbons in ITER-like conditions and their interaction with hydrogenic speciesPWI-08-TA-06/IPP/PS/0113CH4 tracer experiments,erosion-redeposition studies, reflection propertiesPWI-08-TA-06/IPP.CR/BS/01Reactive interaction of mol.ions with surfaces. Reflection properties of hydrocarbon radical for ITER-like divertor conditionsPWI-08-TA-06/IPPLM/BS/01Characterization of erosion/re-deposition of graphite PFCs at TEXTOR: SEM, EPMA, XRD, AES, XPS etcPWI-08-TA-06/MHEST/PS/01Characterisation of erosion / re-deposition of graphite PFCs at TEXTOR (collab FZJ) Improvement of the NRA ion beamPWI-08-TA-06/MHEST/BS/01Characterisation of erosion / re-deposition of graphite PFCs at TEXTOR and marker probes at JETPWI-08-TA-06/ÖAW/BS/01Reactive interaction of molecular ions (fragmentation, sticking) with Surfaces /Reflection properties of hydrocarbon radicals for ITER-like divertor conditionsPWI-08-TA-06/ÖAW/BS/02Determination of sticking coefficients for impact of small (deuterated) hydrocarbon and other molecular ions on ITER relevantsurfaces by using a sensitive Quartz Crystal Microbalance techniquePWI-08-TA-06/TEKES/BS/01Analysis of the long-term erosion/deposition marker samplesPWI-08-TA-06/TEKES/PS/01Analysis of the long-term erosion/deposition marker samples, work on hot cellsPWI-08-TA-06/TEKES/BS/02PWI-08-TA-06/TEKES/PS/02Local erosion/ deposition (ERO) and plasma transport (EDGE2D, DIVIMP) modellingPWI-08-TA-06/VR/BS/01Extension of spectroscopic and QMB diagnostics for the JET ILW project Characterisation of graphite PFCs at TEXTORPWI-08-TA-06/VR/PS/01Tracer experiments. Development of tracer techniques: C-13, TMB, SH4





Motivation - ITER

Beryllium

Tungsten

ITER

Lifetime issues Erosion, transport, and deposition of divertor/first wall material (Be/C) Qualification of W as PFM Mixed material systems (Be, C, W) Control of transient heat loads Safety issues Retention of tritium via co-deposition Methods to release the trapped tritium Dust formation

Research goal: minimisation of risksand optimisation of ITER availability!

All topics are related to each other!

Graphite




Material Migration in Tokamaks with low-Z PFCs

Present view: Erosion and deposition is a question of flux balance Main chamber is the dominant erosion source of C (Be) caused by ion and neutral bombardment Material is transport to the inner divertor due to flows Multiple step process (C) and transport to remote areas Outer divertor: erosion or deposition zone

This SEWG deals primarily with: Measurement and modelling of chemical erosion C and Be migration/transport in fusion devices (measurement and modelling) Deposition and sticking of (hydro)carbons Balance of erosion and deposition in fusion devices Erosion and deposition diagnostics




Motivation - Tasks

Where are the species eroded from? How much is eroded? Spatial distribution of the erosion yield …

What is the impact of seeding impurities on the erosion process?Synergetic effects with Nitrogen, Argon …

What does the plasma do with the eroded hydrocarbons ? Hydrocarbon catabolism and C transport….

What does the plasma do with the eroded Be? Be transport….

Where are the eroded species deposited?Inner divertor, gaps, remote areas ….

Amount of deposited particles? Which hydrocarbon films are produced?Hard layers, soft layers, mixed layers ….

Which species is re-eroded and how?Chemical sputtering: Methane-, ethane-family … ELM-induced erosion: material clusters ….

We have to understand:

Erosion

Migration

Deposition

Re-erosion




ITER Predictions / SEWG

Predictions for

ITER

Data base, A&M data, Material data:

HYDKIN, MD,ADAS, TRIM …

Code and data base validation: benchmark experiments

TEXTOR, AUG, TJ-II, Tore Supra …

Plasma backgroundB2-Eirene

or EDGE2D

Tokamak experiments JET, AUG

ERO modellingLaboratory experimentsMAJESTIX …

Linear experimentspilot-MAGNUM, PSI-II

PISCES




Outline

Measurement and modelling of chemical erosion C and Be migration/transport in fusion devices (measurement and modelling) Deposition and sticking of (hydro)carbons Balance of erosion and deposition in fusion devices Erosion and deposition diagnostics




Measurement and Modelling of Chemical Erosion

Examples: Spectroscopic measurement of chemical erosion und ITER-like

detached divertor conditions – FZJ, TF-E Impact of ELMs on chemical erosion in the JET and MAST divertor

– FZJ, UKAEA, TF-E High ion flux exposure of different CFC materials in pilot-MAGNUM

and PSI-II under ITER-divertor plasma conditions – FOM, IPP, FZJ Understanding of hydrocarbon break-up in He/H plasmas with

molecular beams – CIEMAT




Density ramp discharges with transiently detached outer divertor leg:

Decrease of intrinisic CD and CII photon flux emission in

recombining plasmas: low Te<2 eV and high ne~2*1020m-3

L-mode: Reduction of chemical sputtering at low Te (energetic threshold)

JET: Chemical Erosion in Cold Divertor Plasmas

Density feedback-controlled discharge with detached outer divertor:

Extrinsic carbon source (CD4) observable!

Effective D/XB valuesabout 35% higher in detached

than in attached plasmas!

S. Brezinsek et al. accepted JNM




ELM-induced Enhanced Erosion in JET

Carbon deposition on QMB reflects erosion of divertor target, mainly from ISP position

Arrhenius-type equation:

ELM energy WELM [kJ]

Physical sputtering(Y=1.5%)

)/exp( ELMa WW

Processed exp. data

C d

epo

siti

on

per

EL

M [

ato

ms/

cm2 ]

0 100 200 300 400 50010

13

1014

1016

1015

~10x less

1

3

4

inn

er Q

MB

5

Thermal decomposition of carbon layers under ELM impact

A. Kreter et al.accepted for PFR




t=0 +33 s +66 s +99 s

+132 s +297 s +627 s +1320 s

Motivation: characterisation of material transport due to transients Photron camera + optics from the slow filtered camera fitler imaging + speed low spatial resolution 1 cm, 256x256 pixels high time resolution: 30-60 kHz insufficient time resolution to capture dynamics, but getting closer…

LOWER DIVERTOR VIEW

CI filter at 910 nm, 5 nm FWHM, 30 kHz, 20 s shutter shot 20627

Impurity Production during ELMs in MAST

S. Lisgo presented at IAEA 2008

Time resolved measurements of divertor CI, CII and CIII emission during an ELM




Erosion yields at high ion fluxes in pilot-PSI

Exposures have been performed in the flux range 1023-1024 /m2s Calibration of the chemical erosion has been verifies by absolute measurements with CH4 injection (D/XB ~ 500) Comparison with ERO calculation showed impact of small plasma “diameter” (~mean free path) at Te<2eV Flux determination is currently being re-examined (~ factor 2) Impact of surface temperature distribution not yet included

J. Westerhout et al.

ITER domain




Preliminary Flux Dependence Analysis

Pilot-PSI

Te and Eion normalised




Injection of hydrocarbons in TJ-II by molecuar beams

SOL SOL

SOL

Methane and ethene break-up in hydrogen and helium plasmas

P. Tabares et al.PSI 2008

The set-up for He beam diagnostic was used to inject methane and ethene in He and H ECRH plasmasThe emission profiles of H and CH (A-X) were recordedRatios of H/CH emission are evaluated by relative calibration3H per CH are emitted from methane break-up (He plasmas)Penetration of H from methane much larger than from H2 in He plasmasSame penetration for CH from methane/ethene Common precursor




Carbon Migration/Transport in Fusion Devices

Milestones 13CH4 tracer injection in JET. Post-mortem tile analysis,

spectroscopic analysis, local erosion/ deposition (ERO ) and plasma transport (EDGE2D) modelling

- TF-E, UKAEA, VR, TEKES, FZJ 13CH4 tracer injection in AUG. Post-mortem tile analysis,

spectroscopic analysis, local erosion/ deposition (ERO) and plasma transport (DIVIMP) modelling – IPP, TEKES

13CH4 tracer and hydrocarbon injection modelling (ERO) in TEXTOR – FZJ




JET: 13C deposition in the Centre of the MKII-GB divertor




JET: 13C Deposition in the MKII-SRP Divertor

M. Rubel et al.




Measured deposition (AUG divertor)

Shape of deposition (ERO)

Local Erosion/deposition Modelling of 13CH4 Injection in AUG with the ERO code

M. Airilia et al.presented at PSI 2008

Extensive modelling of the 2003 AUG divertor puffing experiment was carried out

Shape of deposition reasonably well reproduced Locally deposited amount significantly smaller than in experiment (shadowing) The deviation of deposition tail from B direction due to E x B drift can be reproduced by applying a uniform E-field Results suggest that the injection might have a local perturbation in plasma Exact gemoetry with shadowing effects not yet applied




Plasma Transport (EDGE2D, DIVIMP) Modelling (AUG)

L. Aho-Mantila et al.

L-mode plasma for the 2007 AUG methane injection experiment was modelled with SOLPSA realistic plasma background for the local injection was obtainedA DIVIMP model for the global carbon transport was set up using an OSM background plasma

Outer divertor target plate

13C deposition pattern




Next: Check for influence of local injection on local plasma parameters (cooling and increase of ne) ⇒ coupling of ERO with fluid model from M. Tokar´

Modelling of CH4 Injection at TEXTOR

Example: hydrocarbon injection through gas inlet – higher hydrocarbons

C2D4 injection: radial penetration of

C2 and CII light: EXP vs. ERO

Injected species

D/XBCD A-X band

D/XBC2 d-a band

EXP ERO EXP ERO

CD4 36 65 930 -

C2D4 31 80 48 45

C2D6 27 76 65 62

Effective D/XB values: EXP vs. ERO

Good agreement ofobserved and modelled profiles

Modelled and observed D/XB agree well for C2, but differ for CD by a factor of ~2

R. Ding et al. submitted to ppcf




Deposition and Sticking of Hydrocarbons

Examples Deposition and re-erosion of hydrocarbons in castellated structures

– FZJ, VR, SFA,TF-E, VR, UKAEA Reactive interaction of molecular ions (fragmentation, sticking) with

surfaces – ÖAW, CR-IPP Erosion and deposition in remote areas and the impact of N2 – IPP,

CIEMAT




Carbon Deposition in Be Limiter Tile Gaps in JET

M. Rubel et al.




Ion Survival Probability

ION SURVIVAL PROBABILITY Sa(%)HYDROCARBON IONS ON CARBON

INCIDENT ENERGY 3 – 45 eV

Z. Hermant et al.

•neutralization of ions (survival pobability)

•surface-induced dissociations (energy partitioning)

•chemical reactions at surfaces (H-atom, CHn-transfer)

Experimental setup




Reactive Interaction of Molecular Ions with SurfacesReactive Interaction of Molecular Ions with Surfaces

0 20 40 60 80 1000,0

0,1

0,2

0,3

0,4

0,5

Stic

king

coe

ff. o

f D

Collision Energy (eV)

CD2

+ on

CFC PSW

CD2+ on plasma sprayed tungsten (PSW) and CFC (AUG tiles)very stable beam with D flux of ~1011 cm-2 s-1

long time exposure (BESTOF)very low incident energy (~ 0 eV), narrow energy distribution (~100 meV FWHM)sticking coefficient of D from CD2+: CFC: S ~ 0.1 - 0.4; PSW: S ~ 0.05 - 0.1

W. Schustereder et al. Nucl. Instr. Meth. B




C+, H+

to thepumps

pumping duct

JET MKII divertor

experimental setup in PSI-2

adjustableneutra lizerp late

plasm a

hot liner( )sta in less stee l

Si-wafer

N , H ,2 2 CH 4

opticald iagnostic

pumping duct

T=200°C

PSI-2 Experimental Setup: Pumping Duct Measurements

W. Bohmeyer et al.PSI 2008




PSI-2: Impact of Nitrogen on Erosion & Deposition Pattern in Remote Areas

220 240 260 280 300 320 340 360tim e (m in)

54

55

56

57

58th

ickn

ess

(nm

)

2 sccm C H4

2 sccm N2

-0 .044 nm /m in

-0.044 nm /m in

2 sccm N2

no injection

Tcoll =330 K

+0.031nm /m in-0.043 nm /m in

Film thickness in the pump duct vs. time:In pure H2 plasma and co-injection of CH4 and / or N2

Collector temperature 330 K.

Pressure 1 Pa


No synergetic effect of enhanced erosion with H2 and N2

=> volume process not a surface process




8000 12000 16000 20000 24000 28000 32000tim e / s

60

61

62

63

64

65

66

67

68

69

70

71

72

73

74

film

thic

knes

s / n

m

P lasm aO N

Plasm aO FF

310 K 330 K 350 K

2 sccm CH4

1.4 sccm Ne

collector tem perature :

No impact of Ne on the erosion and deposition process!

PSI-II: Impact of Nitrogen on Erosion & Deposition Pattern in Remote Areas





Balance of Erosion and Deposition in Fusion Devices

Examples In-situ layer disintegration in the inner divertor of JET – TF-E, FZJ,

UKAEA, FOM Carbon balance in Tore Supra: Carbon sources and sinks - CEA Characterisation and modelling of erosion and re-deposition of

graphite PFCs at TEXTOR – FZJ, VR, SFA, IPPLM




Dynamics in Material Migration in the Inner Divertor of JET

Strongest deposition observed in the inner divertor pump duct area Post-mortem analysis, spectroscopy and deposition monitors (QMB) used

The (step-wise) local migration is mainly determined by Strike-point configuration (line-of-sight transport) History effect (soft layer appearance and destruction) Power to the target (ELM strength)

Cleaning discharges in H-mode with strike-point sweeping over the horizontal target led to the strongest deposition in the pump duct area

4

3

4

3

VT HT

<

Deposition on the QMB in the inner divertor pump duct entrance

S. Brezinsek et al.EPS 2008




JET: Inner vs. Outer Divertor Deposition and Erosion

Direct comparison between inner and outer divertor deposition with QMBs

5

8

7

4 6

3

1

HTVT

QMBQMB

SOL SOL

PFR

Fuelled ELMy H-mode Similar conditions

Outer divertor close to erosion/deposition balance Different surface conditions in inner and outer divertor leg Investigation is ongoing (impact of other configurations, gas injections

72372 72376 7237772371

HT VT

outer divertor QMBinner divertor QMB




TS: Measurement of Chemical Erosion on the TPL

CCD

Filters wheel(Dα, C2, C+, CD)

Splitter cube

Optical view

erosion area

erosion area optical fibres validate filtered images

CCD and spectrometer system both calibrated in situ with labsphere

D434.0 nm

CD 430.7 nm

38799C+ 426.7 nm

wavelength

CCD

Filters wheel(Dα, C2, C+, CD)

Splitter cube

4 fibers linked to a Czerny-Turner spectrometre

E. Delchambre et al.PSI 2008




Erosion Yield Measurements in TS

CD band observed on TPL since Chemical erosion experiment (Dec 06) (sensitivity 10x lower in this region ! integration time = 3 s) Ychem = CD(431 nm)/Dg

[S/XB]Hg = 1000 [S/XB]CD = 65

Erosion experiment:

Ychem ~ 2 % = 30% of Ytot (CII426nm/Dγ)

[S/XB]Hg = 1000 [S/XB]CII (426nm) = 20

Erosion experiment :

Ytot ~ (CII/Da) * ([S/XB]CII/[S/XB]Ha) ~ 6 %

However, other line combinations Da and CII at 658 nm suggest lower yield

E. Delchambre et al.PSI 2008




0 1 2 3 4 5 6 7 8 9 10

0.1

1

10 SIMS SEM

La

ye

r th

ick

ne

ss

[m

]

Distance from surface [mm]

0 1 2 3 4 5 6 7 8 9 10

0.1

1

10 SIMS SEM

La

ye

r th

ick

ne

ss

[m

]Distance from surface [mm]

Deposition profile tile 20 toroidal gap (1.5 mm)

Deposition profile tile 20poloidal gap (1.8 mm)

= 0.54 mm

Composition from EPMA, RBS: B : C : O ~ 2 : 1 : 1 Mass density ~1.3 g/cm3

= 0.75 mm

Larger thickness in toroidal than in poloidal gaps (factor of >~2)Decay length comparable to previous experiments despite larger gap

A. Kreter, P.Wienhold et al.

TEXTOR: Long-term Deposition in Gaps of the Toroidal Limiter




Profile shape is similar to the experimental one

Absolute values are not recovered Deposition at the bottom (not shown

here) can be partially recovered (nbottom/nedge~ 20% for RN

D = 0.9)

RNC = 0.5

3DGAP code has been developed and simulations started: reflection at inside walls of gap chemical erosion of layers deposited inside gaps elastic collisions with neutral gas inside gaps various particle sources Coupling of 3DGAP code with PIC modelling and ERO (plasma penetration, electrical field, usage of ERO infrastructure, …) in preparation

Modelling of Deposition in Gaps

First comparison with TEXTOR experiments (castellated test limiter)

A. Kirschner et al.




Summary

Progress in both Task Agreements clearly visibleTasks cover a wide range of physics and chemistry

from basic research to tokamak discharges

Main points: benchmark of modelling codes with experiments => code verification

machine comparison => general trends basic understanding of sticking coefficients => input for codes

experiments under ITER-like conditions




Outlook 2009

New Task Agreement ”Erosion, transport and deposition of first wall impurities”focuses on the material migration part of the SEWG

Objectives for 2009/2010 Global transport investigations using 13CH4, SiH4 tracer and Be-evaporation in divertor tokamaks and associated plasma transport modelling Global transport investigations tokamaks and associated plasma transport modelling Local transport investigations with associated plasma transport modelling Deposition and re-erosion in gaps Measurements and modelling of first wall material erosion under high particle fluxes

eu plasma-wall interaction tf – meeting 27.10.-29-10-2008 - frascati sewg erosion & transport...

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