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![Page 1: Radomir PanekEU PWI Task Force Meeting - CEA Cadarache1 PWI work in Association-IPP.CR Presented by R. Panek Content: 1. Collisions of hydrocarbon ions.](https://reader038.fdocuments.in/reader038/viewer/2022110116/5514e5bb550346a80c8b4857/html5/thumbnails/1.jpg)
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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Radomir Panek EU PWI Task Force Meeting - CEA Cadarache 2
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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Radomir Panek EU PWI Task Force Meeting - CEA Cadarache 3
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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Radomir Panek EU PWI Task Force Meeting - CEA Cadarache 4
Percentage of Surviving Ions, Sa(%)
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Radomir Panek EU PWI Task Force Meeting - CEA Cadarache 5
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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Radomir Panek EU PWI Task Force Meeting - CEA Cadarache 6
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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Radomir Panek EU PWI Task Force Meeting - CEA Cadarache 7
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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Radomir Panek EU PWI Task Force Meeting - CEA Cadarache 8
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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Radomir Panek EU PWI Task Force Meeting - CEA Cadarache 9
• 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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Radomir Panek EU PWI Task Force Meeting - CEA Cadarache 10
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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Radomir Panek EU PWI Task Force Meeting - CEA Cadarache 11
Testing at tokamak CASTOR
Biasing electrode with a changeable head
a=85 mm
SOL
MOVABLE HOLDER
BIASING HEAD
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Radomir Panek EU PWI Task Force Meeting - CEA Cadarache 12
• 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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Radomir Panek EU PWI Task Force Meeting - CEA Cadarache 13
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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Radomir Panek EU PWI Task Force Meeting - CEA Cadarache 14
Hydrogen desorption from the membrane
Temporal evolution of the desorbed hydrogen pressure (membrane heated up to 1000oC during desorption)
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Radomir Panek EU PWI Task Force Meeting - CEA Cadarache 15
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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Radomir Panek EU PWI Task Force Meeting - CEA Cadarache 16
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