Radomir PanekEU PWI Task Force Meeting - CEA Cadarache1 PWI work in Association-IPP.CR Presented by...

Radomir Panek EU PWI Task Force Meeting - CEA Cadarache 1

PWI work in Association-IPP.CRPresented by R. Panek

Content:1. Collisions of hydrocarbon ions with carbon surfaces.2. Plasma spraying of tungsten. 3. Retention of tokamak atomic hydrogen in metalic membranes.

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Collisions of hydrocarbon ions with surfaces* dissociations and chemical reactions from mass spectra, product ion translational energy and angular distributions

C1 ions: CH3+, CH4

+, CH5+

C2 ions: C2H2+, C2H3

+, C2H4+, C2H5

+

Influence of internal energy of projectiles on the extent of fragmentation*

Collisions of doubly-charged vs. singly charged ions with surfaces*(effect of charge: C7H8

+, C7H7+)

(* collaboration with the University of Innsbruck)

ENERGY RANGE

10 eV - 55 eV

SURFACE

Carbon: HOPG (highly oriented pyrolytic graphite), TOKAMAK tiles

SURFACE TEMPERATURE

- non-heated (room temperature)

- heated to 1000 K

Collisions of Hydrocarbon Ions with Carbon Surfaces

Z. Herman, J. Žabka, J. Roithová, J. Hrušák, J. Jašík, I. Ipolyi, L. FeketeováJ. Heyrovský Institute of Physical Chemistry, Acad. Sci.

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Experiment Setup

PROCESSES OBSERVED

• neutralization of ions (survival probability)

• surface-induced dissociations (energy partitioning)

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

• quasi-elastic scattering of projectiles

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Percentage of Surviving Ions, Sa(%)

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0 5 10 15 20 25 30 35

46.3eV

E'tr [eV]

31.3eV

20oC

600oC

C2H

3

+ + HOPG -> C2H

3

+

16.6eV

P[E

' tr]

0 5 10 15 20 25 30 35

Calculated from product C2H

3

+

46.3eV

E'tr [eV]

21.3eV

20oC

600oC

C2H

5

+ + HOPG -> C2H

5

+

11.6eV

P[E

' tr]

Product Ion Translation Energy Distributions

C2H3+, C2H5

+, HOPG, N=60o

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Angular Distributions: Summary of C2Hn+

HEATEDNON HEATED

030

60

90

030

60

90

030

60

90

030

60

90

030

60

90

030

60

90

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Summary

1. Heating to about 1000 K practically removes the hydrocarbon layer covering at room temperature the carbon surfaces

2. Ion survival probability Sa(%) for incident angle of Фn= 600

- about < 1% (0.1-0.5%) for radical ion projectiles (CH4+, C2H2

+, C2H4+)

- about 5-15 % for closed-shell projectile ions (CH5+, C2H3

+, C2H5+)

3. Inelasticity of dissociative collisions (dissociation after interaction with the surface):

translational energy of surface-energized projectile ions

- 30-40 % for non-heated (hydrocarbon covered ) surfaces

- 45-60 % for heated (clean) surfaces

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Plasma Sprayed TungstenJ. Matejicek1, V. Weinzettl1, E. Dufkova1, V. Piffl1, V. Perina2

1 Institute of Plasma Physics, Prague, CZ2 Institute of Nuclear Physics, Prague, CZ

• Plasma spraying of tungsten Water- and hybrid-stabilized plasma torches Coating properties and optimization

• Testing in tokamak CASTOR Use of biasing to increase the power load

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• Spraying optimization:– powder size selection– reduced oxidation– reduced porosity, increased thermal conductivity

• Spraying techniques:- water-stabilized plasma- hybrid-stabilized plasma (water+argon)- in air

• Reducing the oxidation:– Auto-shrouding: admixture of WC

decarburization of WC -> W2C -> WC reacts with oxygen, forms carbon oxide limits oxygen access to tungsten

– Very little oxide in the coatings (~0.3-0.5% surface, 0.05% inside)

Spraying development

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Reducing the in-flight oxidation

pure W W+WC 5:1 pure W- lower plasma temperatures

- Ar stabilizes and elongates the arc- lower porosity- fewer unbonded interfaces- less oxide

Hybrid torch

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Testing at tokamak CASTOR

Biasing electrode with a changeable head

a=85 mm

SOL

MOVABLE HOLDER

BIASING HEAD

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• Surface morphology• Surface composition (EMPA,

RBS, ERDA)

• Plasma sprayed W• Plasma sprayed W+Cu (50:50 vol.)• Bulk W• Bulk Cu• Bulk graphite

Biasing head materials: Plasma sprayed W

Plasma sprayed W - detail

Testing at CASTOR (2)

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Retention of tokamak atomic hydrogen in metalic membranes

M. Hron, J. Stöckel, F. Žáček, M. Notkin, V. Livshiths

Collaboration: Bonch-Bruyevich University, St.Petersburg

• Metalic membranes (Nb, V) absorb suprathermal atoms of hydrogen isotops that pass through an adsorbed layer on the membrane surface

• Absorbed atoms can move freely inside the membrane but the adsorbed layer hampers their exit

Principle

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Hydrogen desorption from the membrane

Temporal evolution of the desorbed hydrogen pressure (membrane heated up to 1000oC during desorption)

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Highest sensitivity to atomic hydrogen (relative to the background) was observed with the exposure temperature 400 K

H2 + Hmembraneexposed to plasma

H2

membraneexposed to neutral gas

Dependence of the desorption on membrane temperature during exposure

Hhydrogen atoms originating from plasma

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Recent experiments have shown that in the tokamak conditions in CASTOR:

A/ membrane absorbs suprathermal hydrogen atoms

B/ number of absorbed atoms can be measured absolutely, so the neutral particle flux can be determined (calculation of particle balance?)

Conclusions