Jožef Stefan Institute 5 th Meeting of EFDA TF PWI, Ljubljana, 13-15 November 2006 1 Activities relevant to PWI in fusion devices of Slovenian Fusion Association.

5th Meeting of EFDA TF PWI, Ljubljana, 13-15 November 2006 1

Jožef Stefan Institute

Activities relevant to PWI in fusion devices of Slovenian Fusion Association (SFA)

(Association EURATOM - MHST)

Compiled by Iztok Čadež

Jožef Stefan Institute, Ljubljana, SloveniaAssociation EURATOM-MHEST (SFA)



1. Physics projects in the field of PWI

2. Overview of results on individual projects

3. Status of collaborations



P2. Interaction of vibrationally excited hydrogen with fusion relevant materials (VEVOF)

P3. Heterogeneous catalytic recombination of neutral hydrogen atoms on fusion relevant materials

P5. Application of ion beam analytical methods to the studies of plasma wall interaction in tokamaks (IBAF)

P6. Deuterium retention and release from materials – complementary method to tritium methods

1. Physics projects in the field of PWI1. Physics projects in the field of PWI



2. Overview of results of individual projects2. Overview of results of individual projects



P2: Interaction of vibrationally excited hydrogen (H2, D2) with fusion relevant materials (VEVOF)Iztok Čadež1, Primož Pelicon1, Sabina Markelj1, Zdravko Rupnik1, Milan Čerček2, Tomaž Gyergyek2, and Vida Žigman3

1 Microanalytical Centre, Department for Low and Medium Energy Physics (F2), JSI2 Plasma Physics Laboratory, Department for Reactor Physics (F8), JSI, Ljubljana3University of Nova Gorica, Nova Gorica

Processes of interest:

1. - Vibrational distributionVibrational distribution of hydrogen molecules from thermal desorptionthermal desorption and recombinative desorptionrecombinative desorption. - Ratio of atomic to molecular speciesRatio of atomic to molecular species

2. Interaction of vibrationally excited molecules with plasma-facing materials: - Change of vibrational distribution caused by interaction with surfaces, - Transfer of vibrational energy to the wall and its effects on erosion yields, and- Wall sticking probability for excited molecules.

Our main goal is to acquire as much as possible experimental information on reactions and properties of vibrationally excited hydrogen H2, D2, HD … that is relevant to edge plasma and PWI!



B

New set-up for vibrational spectroscopy New set-up for vibrational spectroscopy of vibrationally excited hydrogen of vibrationally excited hydrogen molecules using guiding magnetic field molecules using guiding magnetic field for incident electron beam and ion for incident electron beam and ion extraction was constructed and tested extraction was constructed and tested during previous two years and it started during previous two years and it started to be used last year. to be used last year.

Diagnostic technique is based on the detection of H- ions produced by dissociative electron attachment (DEA) at and below about 4 eV incident electron energyy: H2(X 1g

+,v) + e → H2-(X 2u

+) → H- + H

We are the only using this experimentaltechnique that was originally developed at UPMC, Paris.



Present status of our final goal of experimental set-upPresent status of our final goal of experimental set-up

- Vibrational spectroscopy – developed and available developed and available ( … )( … )

- Atom/molecule ratio (+ion branch) – to be developed and testedto be developed and tested

- Test atmosphere – partially dissociated neutral hydrogen gas or low temperature hydrogen plasma – partially available available but still to workbut still to work

- In situ and in real time H and D depth profiling by Li ERDA – developed developed and available and available ( … )( … )

- Sampling – to be developed and testedto be developed and tested



Source of VEHM

Recombination of hydrogen atoms on Recombination of hydrogen atoms on surfaces of different fusion relevant surfaces of different fusion relevant materials (W, C,Ta)materials (W, C,Ta)

Hydrogen molecules dissociate on tungsten Hydrogen molecules dissociate on tungsten filamentfilament

Vibrational spectroscopy of molecules Vibrational spectroscopy of molecules produced by recombination produced by recombination

-0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.50.0

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3.0v=0123456789

0123456789

v=0123456789

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Nor

mal

ized

sig

nal

Electron energy [eV]

hladen Id=3p8A KonvHlad Konv Id=3.8A

0 2 4 6 8 10 12 14 16 18

02468

1012141618

hladen Id=3p8A KonvHlad Konv Id=3.8A

Tv = 3600 K Tr = 700 K

H2/W



Almost negligable D- production

Cu H2

0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 4,50,0

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H2;J=0;v=0123456789

060928awD.opjElectron energy [eV]

No

rma

lize

d s

ign

al

B

Id=3A (1350oC)

Id=3,4A (1450oC) Konv Id=3A konv Id=3p4A

D2

-1,0 -0,5 0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 4,5 5,00

2

4

6

8

100123456781012

D- y

ield

[s-1]

Electron energy

sum Id=3.4A sum Id=3.8A sum Id=4.2A conv

0 1 2 3 4 50,0

0,5

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4,00123456789

060515awD.opj

No

rma

lize

d S

ign

al

Electron Energy [eV]

Id=3A (1350 oC)

Id=3,4A (1450 oC)

Id=3,8A (1550 oC) Konv Id=3A Konv Id=3.4A konv_Id=3.8A

H2

D2

-0,5 0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 4,50

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01

2

3

4

5

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7810

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0123456781013

D - y

ield

[s-1

]

Electron energy [ev]

Id=2,8A (1300oC)

Id=3.4A (1450oC)

Id=4.2A (1650oC) conv Id=2,8A conv Id=3,4A conv Id=4,2A

Ta

Measurements are performed also on W, Teflon, and C (in progress)

We plan to use similar source of vibrationally excited molecule for spectroscopy experiment by

injection into plasma.



Search for mechanisms for production Search for mechanisms for production of vibrationally excited hydrogen of vibrationally excited hydrogen molecules: molecules:

Recombination of Recombination of hydrogen atoms on hydrogen atoms on surfaces after surfaces after permeation through permeation through membranes (Pd, Ta)membranes (Pd, Ta)

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0 2 4 6 8 10 12 14 16 18 200.1

1

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012345678 012345678

012345678 012345678

H-

yiel

d [ s

-1 ]

000/10 003 006 007 008/7.5 009 014

051109a.opj

spec.# t [oC] p [Torr]0 20 6,2(-8)3 168-176 3,0-3,2(-6)6 241-246 5,6-5,7(-6)7 246-248 6,0(-6)8 249-257 6,0-6,1(-6)9 257-259 6,0-5,3(-6)14 96-86 7,2-5,3(-7)

H

- yi

eld

[ s-1

]

Electron energy [ eV ]

000/10 003 006 007 008/7.5 009 014

051109a.opj

0 5 10 15 20

0

10

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Ion

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Electron energy (uc) [ eV ]

001/5 003 005 006/5 007 008 009 010 011 012 ref--050919_25 013/10

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0 5 10 15 200

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012345678012345678

051103a.opj

Ion

yiel

d in

10

s

Electron energy (uc) [ eV ]

032 033/osnovni tlak

Study with Pd:

An attempt with Ta:

Fragmentation of Fragmentation of hydrocarbons?hydrocarbons?



Search for mechanisms for production Search for mechanisms for production of vibrationally excited hydrogen of vibrationally excited hydrogen molecules: molecules:

Vibrationally excited Vibrationally excited molecules from molecules from hydrogen atoms source:hydrogen atoms source:

-1 0 1 2 3 4 5

0.0

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No

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nd

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bst

ract

ed

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Electron energy [eV]

C sum I1=28A sum I1=29A sum I1=30A konv I1=28A konv I1=29A konv Id=30A

0.0 0.5 1.0 1.5 2.0 2.5 3.01E-7

1E-6

1E-5

1E-4

1E-3

0.01

0.1

1

10

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Re

lativ

e p

op

ula

tion

Excitation energy [eV]

Zased I1=25A zased I1=26A Zased I1=27A Zased I1=28A Zased I1=29A Zased I1=30A Zased I1=38A I2=26A T=1400K T=1550K T=1800K T=2700K

10 15 20 25 30 35 400

20

40

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160spec.# I1/A I2/A

10 24 16.511 25 16.512 26 16.513 27 16.514 28 16.515 28 16.516 29 16.517 30 16.518 30 16.519 30 17.520 31 17.521 31 17.522 31 18.523 32 18.524 32 19.525 33 19.526 33 20.527 33 21.528 34 21.529 34 22.530 34 22.531 35 22.532 35 23.533 35 23.534 36 23.535 36 24.536 37 24.537 37 24.538 37 2639 37 2640 38 26060907b.opj

Me

an

ba

ckg

rou

nd

sig

na

l [ c

ou

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Spec. No.

Mean I

1 [ A ]

I2 [ A ]

Experiment performed in collaboration with IPP, Garching (Th. Schwarz-Selinger)



Test atmospheres Test atmospheres for exposure of samples to for exposure of samples to vibrationally excited hydrogen moleculesvibrationally excited hydrogen molecules

• hot-filament dissociation of hydrogen produces partially dissociated neutral test atmosphere;

• vibrationally excited molecules are produced by atom recombination on the wall;

• diagnostics: DTVE coupled to the test chamber;

Partially dissociated neutral gas

Low-temperature plasma



In-situ hIn-situ hydrogen depth profiling in samples exposed to controlled atmosphereydrogen depth profiling in samples exposed to controlled atmosphere

12 14 16 18 20 220

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l m n

o

p

r1 s1

t1

u v

Inte

gra

l sig

na

l

Individual spectra

H(surface) D(surface)



0 2000 4000 6000 8000 100000,00E+000

1,00E+015

2,00E+015

3,00E+015

4,00E+015

Co

nce

ntr

atio

n o

f D [a

t/cm

^2]

Time [s]

Concent. D fit

S=2.1x10-7 ± 0.6x10-7,k = 3.6x10-20 cm2/s ± 2.4x10-20 cm2/s.

)2tanh()( 1CtkSk

St



P2 - Work plan for immediate futureP2 - Work plan for immediate future

- HH22(v) and D(v) and D22(v) production by recombination in the cell(v) production by recombination in the cell

- Vibrational relaxation by wall collisions (sampling)Vibrational relaxation by wall collisions (sampling)

- Development of the H2v source for spectroscopy experiment in Development of the H2v source for spectroscopy experiment in collaboration with FZJ (S. Brezinsek)collaboration with FZJ (S. Brezinsek)

- Modeling of the gas cellModeling of the gas cell

- Upgrading of experiment – addition of the + ion side forUpgrading of experiment – addition of the + ion side for

atom to molecule ratio determinationatom to molecule ratio determination



P3: Heterogeneous catalytic recombination of neutral hydrogen atoms on fusion relevant materials

Miran Mozetič, Alenka Vesel and Aleksander Drenik Department of Surface Engineering and Optoelectronics (F4),

Jožef Stefan Institute, Ljubljana, Slovenia

Motivation

Predicting the density of neutral atoms in confined spaces (such as plasma reactors, fusion edge plasma, tokamak pump ducts)

Measuring the neutral atom density by means of catalytic probes



1. Detailed overview of the existing experimental data on hydrogen recombination on different materials

So far there is no satisfactory understanding of recombination Experimentally obtained values are often contradicting Not all fusion relevant materials have been measured yet

material

W 0.05 – 0.7

quartz 6x10-5 – 6x10-2

pyrex 10-5 – 10-2

Work performed since last TF PWI meetingWork performed since last TF PWI meeting



2. Measurements of recombination coefficient by Smith’s side arm

diffusion method Opening to main part of plasma reactor

Catalytic walls

Catalytic endplate

0

L0

L

n0

0 depth

dens

ity

max

min

Recombination coefficient strongly depends on material form (different polymorphous or amorphous forms of carbon)Example: Carbon – values of strongly differ for graphite, sputtered carbon deposits and hydrogenated amorphous carbon

Drenik A., Vesel A., Mozetic M., Measuring probability coefficient for heterogeneous recombination of hydrogen atoms on surface of fusion relevant materials. V: 33rd EPS Conference on Plasma Physics, Roma, Italy, June 19-23, 2006.



3. Measurement of neutral hydrogen atom density in Textor

First catalytic probe for TEXTOR was constructed and preliminary tested in TEXTOR

Non-magnetic materials: Catalyst: gold (previously nickel) Thermocouple: W – Re

(previously optical fiber) Detailed measurements are planed

-10 0 10 20 30 40 50

0.0

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1.0

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Pro

be

sig

na

l [a

.u.]

t[s]

Probe temperature (voltage from TC) during a plasma pulse in Textor



P3 – Future plans

Systematic measurements in TEXTOR and needed adaptations of existing probe

Construction of a fibre – optic catalytic probe compatible with the scheduled redesign of the limiter lock system in TEXTOR

Construction of a new plasma system with chambers more suitable for Smith’s side arm diffusion method.



New proposal of this group:

P8: cleaning of carbon deposits

Idea: use neutral oxygen atoms at room temperatureO atoms do not etch carbon fibres at RTO atoms do etch hydrogenated carbon at RTO atoms cause fromation of an extremely thin oxide film on Be and W

If the thin oxide film cannot be tolerated, use N atoms instead of O atoms:HC + N → HCN (pumped away)

Subtasks:Development remote source of O or NThe O (N) density over 1022 m-3The O (N) density 10m away from the source over 0.5x1022m-3 Systematic study on reaction probability between the deposit and O (N) atoms

Discussions with potential partner groups are in progress



P5: Application of ion beam analytical methods to the studies of plasma wall interaction in tokamaks (IBAF)

P. Pelicon, D. Hanžel, M. Kavčič, I. Čadež, Z. Rupnik, J. Simčič, S. Markelj, M. Budnar, Z. Grabnar

Microanalytical Centre, Department for Low and Medium Energy Physics (F2),Jožef Stefan Institute, Ljubljana



• Detectors for -PIXE -RBS -STIM -Secondary Electrons• motorized 5-axis vacuum goniometer (VG Omniax)• 2 optical microscopes• Chopper for dose normalization

Ion microbeamIon microbeam

OM triplet lensInstalled in June 2000proton beam size:•High current mode (PIXE, RBS, SE, PBW)100 pA: 0.9 x 1 µm•Low current mode (STIM), 104 ions/sec: 0.5 x 0.8 µm



Region of interest in

ITER:Divertor

vertical target close to the strike zone

CFCs

W


ITER:Divertor



ITER:Divertor


CFCs

W

Model castellated structure has been exposed in the erosion-dominated conditions of tokamak fusion reaktor TEXTOR at Forschungszentrum Jülich1

Measured C section

1A. Litnovsky et al, J. Nucl. Mater. 337-339, 917 (2005).





Areal distribution of molybdenum (islands)measuredby Li-beam excited X-ray emission (LIXE)

and simultaneously measuredhydrogen lateral distribution by Li-beam ERDA over an area of 1240 x 450 µm2.

Surface lateral distribution of hydrogen at the plasma-exposed surface

is anti-correlated with the distribution of molybdenum deposit.

Hydrogen retention is higher in the surface of uncoated graphite.

Lateral mapping of hydrogen at plasma-exposed surface of castellated limiter

1240 µm

Hydrogen

450

µm

Mo Lα



RBS/ERDA measurement setup:

Beam: 4230 keV 7Li2+, Sample tilted 75°RBS detector at 160°, ERDA detector at 30°ERDA detector equipped with 11 µm Al foilDose controlled by mesh charge integrator (Tungsten mesh, wire diameter 38 micrometers density of 3.2 lines/mm, open area of 77.4 %)

ERDA of hydrogen with 7Li ions, P. Pelicon et al., NIM B 227, 591 (2005)

1) ERDA study of H and Dpermeation through Pd (and Ta) membrane

2) Determination of elastic cross section for 7Li-D scattering:- Measurement with standard a-C:D target- Relative measurement of elastic signal vs. protons from reaction 7Li(d,p)8Li.

ERDA beam line is underreconstruction in order to incorporate UHV experimentalchamber



P6. Deuterium retention and release from metal surfaces – a complementary method to nuclear tritium methods

V. Nemanič, B. Zajec, M. Žumer

Department of Surface Engineering and Optoelectronics (F4), Jožef Stefan Institute, Ljubljana, Slovenia



• during an exposure of D2 at 1 mbar, room temperature, the absorption kinetics

is slow, but detectable. The UHV system was well outgassed, no water was

detected prior D2 admission.

• during the desorption, only HD, D2 and H2 were released, no HDO.

V. Nemanič, B. Zajec, The influence of deuterium exposures on subsequent

outgassing rate of an UHV system , Vacuum 81, 556 (2006)

Systematic measurements of the ultimate detection limit of the UHV

system regarding deuterium retention versus hydrogen background

were examined



• several deep bulk sites exist where hydrogen is much more tightly bound than at

regular interstitial sites, • they have a little impact on regular permeation• their number could often be estimated only by modeling by arbitrarily set energy

levels and their distributions• difficult to make direct observation by present experimental techniques• unfortunately, a complex mathematical treatment can not be compared easily to

the experimental data

Long term repetitive thermal extraction in high vacuum to

determine the concentration of deeply trapped H atoms.



Experiment

kinetics of hydrogen redistribution confirmed by observing

outgassing rate in several 10-15 minute extractions in vacuum

at 780 °C over three months with no exposure to the air

- outgassing rate of untreated sample AISI 304

- stored in residual gas (0.001 mbar H2 in 24 h at R.T.)

- stored for 3-10 days at 1 mbar D2 at R.T.

- charged at 489 °C, 10 minutes at 1 bar D2

- outgassing rate repeated after some days



Experimental detailsAISI304 sample, plate 20 50 0.6 mm

p = 0.001 mbar C = 5.74 1016 H/cm3

p = 0.001 mbar N = 8.2 1014 H2/cm2

RF coil to all metal UHV systemsample in a quartz tube

TC



P6: ConclusionsP6: ConclusionsKinetics of hydrogen evolution from stainless steel is governed

• by diffusion from the ordinary sites (fast process) and recombination at the

surface (relatively fast process), described by diffusivity D, that is usually

measured at high p and T

•by release of H from deep states (slow process), observed in long term

experiments at high T.

• deep states could be populated by impact of energetic ions in fusion reactor (H+,

D+ , T+)

• impact on decomissioning?



Activate collaborations in previous year:

P2: FZ, Jülich ( hydrogen recombination on W and graphite, spectroscopy of H2(v) and D2(v)), IPP, Garching ( diagnostics and use of atomic hydrogen source); FOM, Rijnhuizen (some preliminary discussions on spectroscopy experiment).

P3: FZ, Jülich (H recombination on provided samples, plasma cleaning of TEXTOR wall), CIEMAT (in preparation).

P5: FZ, Jülich (lateral μ-mapping of H and D on PFC, study of Mo deposition on limiter, micro analysis of co-deposited flakes, calibration of deuterium ERDA measurements).

P6: Application for EFDA technology project; ENEA, Frascati (hydrogen and deuterium retention); IFP-CNR, Milano.

3. Status of collaborations 3. Status of collaborations

Jožef Stefan Institute 5 th Meeting of EFDA TF PWI, Ljubljana, 13-15 November 2006 1 Activities relevant to PWI in fusion devices of Slovenian Fusion Association.

Documents

th meeting of efda tf

ta hydrogen molecules

field of pwi slide

recombination h

tested slide

w slide

fusion relevant materials

detection of h