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Transcript of 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.
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.
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
Radomir Panek EU PWI Task Force Meeting - CEA Cadarache 4
Percentage of Surviving Ions, Sa(%)
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
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
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
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
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
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
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
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)
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
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)
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
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