Report IPP Garching @ EU Task Force PWI Meeting, Arne Kallenbach, Ljubljana Nov 13-15 2006 1 Compiled by Arne Kallenbach Report from IPP Garching on work

Report IPP Garching @ EU Task Force PWI Meeting, Arne Kallenbach, Ljubljana Nov 13-15 2006 1

Compiled by Arne Kallenbach

Report from IPP Garching on work related to the EU PWI Task Force: Oct 2005- Oct 2006

Max-Planck-Institut für Plasmaphysik

With contributions from W. Bohmeyer, A. Chankin, D. Coster, R. Dux, T. Eich, A. Herrmann, C. Hopf, W. Jacob, A. Kallenbach, C. Linsmeier, M. Mayer, H.-W. Müller, R. Neu, R. Pugno,V. Rohde, J. Roth, K.Schmid,T. Schwarz-Selinger

*

* + Berlin +JET+ PISCES-B


• Chemical erosion (see also talk S. Brezinsek) • Tungsten tokamak (see also talk R. Neu)• Decay and migration of carbon in ASDEX Upgrade• ELM power deposition characteristics in outer midplane• ELM in-out divertor asymmetry• He retention in W-coated surfaces• Chemical erosion by N ions and simultaneous neutral impact (non-scavenging)• Be-W alloying• PISCES-B measurements on D retention and pulsed power with Be seeding• Edge modelling with B2.5 (AUG) and DIVIMP (ITER)• SOL transport and parallel flow

Topics investigated in IPP from Nov 2005 – Oct 2006


Tungsten erosion at LFS limiters on ASDEX UpgradeR. Dux

ICRH: strongest W erosion by sheath acceleration

NBI: Loss of ripple trapped fast ions identified as dominant W sputtering mechanism by Monte Carlo simulations of pitch angle dependence

for both ICRH and NI, W limiter source dominated by ELMsabout 70 % of time-averaged sputtered W during ELMs


Tungsten erosion at LFS limiters on ASDEX Upgrade:ICRH sheath potential from measured W yield


Tungsten erosion at LFS limiters on ASDEX Upgrade:pitch angle dependence form ripple loss of fast NBI ions


Tungsten erosion at LFS limiters on ASDEX UpgradeEffect of type-I ELMs

x 4

x 9

x 5

x 40


Structure and radial decay of ELM filaments in the ompA. Herrmann, A. Schmid

energy carried predominantly by ions

dedicated diagnostic setup


Decay of carbon concentration with increasing W PFC coatingFraction in ASDEX Upgrade A. Kallenbach

slow decay of the carbon concentration with increasing W surface fraction net divertor source becomes important with diminishing C PFC area

scatter due to boronisations,Exp.imerfections, calibrations,…

experiment migration modelling


Divertor becomes important net carbon source with W PFCsrecovery of C after boronisation allows to estimate net source

net outer divertorC source:1.5e19 ions/s

LFS limiter fluxes and C concentration closely coupled heat shield lags behind (1 ML C on heat shield 30 plasma C content)

C part of divertornot coated by boron


Erosion of tungsten in the outer divertor of JET• Tungsten erosion was determined with a marker stripe from 2001-2004• Large erosion at outer strike point, outer baffle and apron• Erosion at strike point >> 2.4 µm• Inhomogeneous erosion due to surface roughness

Erosion of Be, C, Ni and W at the inner vessel wall of JET• Erosion was determined with long term samples from 2001-2004• Whole inner vessel wall is erosion dominated, erosion of C is about 10 times larger than erosion of Be

Erosion of carbon and tungsten in the outer divertor of ASDEX Upgrade• Carbon and tungsten erosion were determined with marker stripes from 2004-5 • Largest erosion at strike points, both for carbon and tungsten• Erosion of carbon 10-20 times larger than erosion of tungsten• 2.8 g C eroded during the campaign

Erosion measurements with markers and long term samplesMatej Mayer

factor 3 larger than migration modeluncertainties, direct losses to inner div


Deposition in inner divertorMatej Mayer

2002 – 20034800 s

2004 – 20053050 s

2005 – 20062900 s

6A

6B

5

4

9C

• Decrease of C-deposition on divertor tiles by factor 7

from 2004/2005 to 2005/2006

• Decrease of C-deposition below roof baffle by factor 10

from 2004/2005 to 2005/2006

Outboard limiters are main carbon source

0 200 400 6000

2

4

6

s-coordinate [mm]

B + C C

9C456B6A

Dep

osi

tio

n o

f B

+C

[10

19 a

t./c

m2]

0 200 400 6000

2

4

6

s-coordinate [mm]

B + C C

9C456B6A

Dep

osi

tio

n o

f B

+C

[10

19 a

t./c

m2]

0 200 400 6000

2

4

6

s-coordinate [mm]

B + C C

9C456B6A

Dep

osi

tio

n o

f B

+C

[10

19 a

t./c

m2]


SOL plasma flow in upper-SN H-mode at outer midplaneHans-Werner Müller


Statements on plasma flowH.-W.Müller


Shot resolved gas balance in ASDEX UpgradeVolker Rohde


High He plasma concentrations encountered in AUG since the transition from a C to a W first wall

He plasma concentration linked to He glow duration and number of discharges since last boronization

Dedicated laboratory experiments show:

W retains ~10 times more He compared to C or boronization layers

He release due to plasma load similar for W and C

Thermal release starts at 400K for both C and W

High He plasma concentrations in AUG are due to higher retention of He in W compared to C – effect expected to vanish at higher wall temp.

Retained He in different C and W materials (NRA)

1016 1017 1018 10191013

1014

1015

1016

1017

1018

600eV 3He FG PVD-W

Pyro-Perp Pyro-Par Boronization

Ret

ain

ed 3

He

(cm

-2)

3He Fluence (cm-2)

200eV 3He FG PVD-W W-Solid

Implications of Tungsten on Helium Gas RecyclingKlaus Schmid


0 -50 -100 -150 -200-0.3

-0.2

-0.1

0.0

0.1

0.2

30%

depo

sitio

n /

eros

ion

rate

(nm

/s)

bias voltage (V)

CH4

N2 / H2

N2 / CH4

H2

30%

increase of erosion rate with bias for H2/N2 and changeover from deposition to erosion for CH4/N2

plasmas at higher ion energies can only be explained by surface effects

evidence for chemical sputtering

Because of the increased erosion due to chemical sputtering the present data base does not allow to recommend N2 admixture to divertor plasmas with carbon PFC’s.

Work performed under the EFDA Task TW3-TPP-SCAVOPFinal Report available upon request ([email protected])

But, the high chemical sputtering yield of carbon films in N2/H2 mixtures make them interesting for removal of redeposited layers.

Planned work: investigation of possible scavenging action of N in laboratory plasmas using cavity probes

NITROGEN PUFFING into the DIVERTOR: RESULTS from LABORATORY EXPERIMENTS with remote ECR in H2, CH4, N2 mixtures

© Thomas Schwarz-Selinger, October 2006

T. Schwarz-Selinger, W. Jacob


Mixed materials formation: Be-W alloying

W on Be • stable Be12W above 1000 K

Tm < 2000 K no W in surface zone

Be on W (ITER divertor!)< 800 K• Be metal layer deposition

Tm ~1560 K

> 1000 K• Be2W surface alloy only (~nm)

• no bulk diffusion, sublimation faster Tm ~2500 K

Future work• Reactivity of Be/W alloys with carbon• Formation of ternary surface layers• Reactivity of different surface layers

with atomic oxygen

Ch. Linsmeier, A. Wiltner, F. Kost

depth profile


Power pulsing experiments in PISCES-BR. Pugno, PISCES-B team under EFDA contract TW5-TPP-CARWBER

• A transitory positive voltage biasing system has been installed on PISCES-B to simulate the heat pulses associated with ELMs.

• A new infra-red diagnostic system has been installed to measure the target surface temperature during the heat pulses.

• From visible spectroscopy and mass loss measurements, the formation time of the Be2C protective coating on graphite samples exposed to beryllium-seeded deuterium plasmas, is reduced in presence of power transients.

• The deuterium retention is increased in presence of power transients for both pure deuterium (+30%) and Be-seeded plasmas (+60%).

• The infra-red measurements evidence a change in emitting area due to a surface morphology modification during plasma exposure (both for pure carbon and Be2C surfaces) in agreement with previous observations by SEM electron micrographs.


R. Pugno, PISCES-B team

• Saturation of the surface is observed in CFC target for fluences higher than 1e26 ion/m2 and target temperature of 1100 K.

• No change in deuterium retention in CFC is observed between pure deuterium plasmas and Be seeded plasmas in that conditions.

• Earlier onset of thermal desorption is observed for mixed material surface i.e. after exposure to Be seeded plasmas as already observed in PISCES-B

• The scaling law for the suppression time of chemical erosion in Be seeded plasmas obtained with FGG target seems to be valid also for CFC target.

Work done at PISCES-B in the frame of the EFDA contract TW5-TPP-CARWBER


• In addition to other activities, the members of the edge group took part in the Edge Modelling Campaign at JET

– Coster

• Edge transport Code-Code Verification/Validation/Benchmarking – Chankin

• EDGE2D runs: adding drifts to JET H-mode pulses

– Konz

• Simulation of disruption thermal quenches with B2 SOLPS – Wischmeier

• SOLPS5 modelling of ohmic plasmas with C13 injection at the top of the

machine

SOLPS work, development and benchmarking D. Coster, A.Chankin, C. Konz, M. Wischmeier


Detailed comparison between B2.5-EIRENE (SOLPS) edge modelling and experiment shows that the code overestimates plasma density and underestimated electron temperature in the divertor, especially near the strike point position.

The example shown above demonstrates a large discrepancy between simulated and experimental Ha radiation profiles, which is the consequence of the overestimate of the plasma density in the divertor.

Dicrepancy in code-experiment comparisons


code-code comparison• Phase I: pure D, no drifts• Phase II: pure D, drifts• Phase III: D+C, no drifts• Phase IV: D+C, drifts

– SOLPS-EDGE2D/NIMBUS • Phase I completed successfully (reported on at PSI

2004)• Phases II and III in progress

– SOLPS-UEDGE• Phase I underway• Phase II expected to start soon

• Additional code-experiment– JET: SOLPS-EDGE2D/NIMBUS– AUG/D3D: SOLPS-UEDGE

EDGE2D D+C

EDGE2D D

SOLPSD+C

SOLPS

EDGE2D

Edge code benchmarking / ITPA activity


• 2D background (ne, Te, Ti, …) written as MDSplus tree by SOLPS (IPP-Garching) [modelled by Chankin]

• provides input to ASCOT Due to open field lines, special care must be taken with the Monte Carlo collisions

• Planned: output of ASCOT to be saved to a MDSplus tree

• ITPA standard pedestal MDSplus tree created based on AUG shot 17151 (provides the equilibrium data)

• ASCOT:

• T. Kurki-Suonio, L. Aho-Mantila, J. Heikkinen, V. Hynönen, T. Kiviniemi, A. Salmi, S. Sipilä, V. Tulkki

Distribution of electrons reaching outer target

AssociationEuratom–Tekes

Using MDSplus for SOLPS to ASCOT


Divertor in-out power asymmetry during ELMs dependson ion grad-B drift direction T. Eich


In-out power asymmetry connected to charge flow asymmetrycharge sign suggests ions to carry excess power

AUG upper SN


TW4-TPP-TRIDEP

Beginning of the project 08/2004intermediate report 12/2004

(end 12/2005) prolongated 06 / 2006 *Main topics:1. Analysis of Cx Hy mixture produced by chemical erosion2. Study of the influence of the target temperature 3. Influence of impurities on chemical erosion IR absorption, QMS, cavities

4. Determination of the balance between deposition and erosion for areas not exposed directly to the plasma ( ITER pumping duct). Experiments and ERO-Modelling

density of atomic hydrogenimprovement of experimental data for modelling (spectroscopic data, cavities,...)

* delayed start of the experiments (reason: no permission to use hydrogen)-

Humboldt Universität zu Berlin W. Bohmeyer


Humboldt Uinversität zu Berlin

Ne=3*1017 m-3 Ne=2*1018 m-3Ne=1017 m-3

1.Clear shift from global to local decomposition with increasing el.-density2.Decomposition and excitation length is not in agreement with atomic data

2D-CH-emission at 430 nm

CH4 injection into a He-Plasma

7 cm

nozzle

Documents

Report IPP Garching @ EU Task Force PWI Meeting, Arne Kallenbach, Ljubljana Nov 13-15 2006 1 Compiled by Arne Kallenbach Report from IPP Garching on work