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Association EURATOM - MEdC
Development of beryllium marker tiles for the ITER-like Wall
project, by using thermionic
vacuum arc (TVA) technique
Cristian P. LUNGU
National Institute for Laser, Plasma and Radiation Physics
(NILPRP)
Elementary Processes in Plasma and Applications GroupMagurele -
Bucharest
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NATIONAL INSTITUTE FOR LASERS, PLASMA AND RADIATION PHYSICS
Cooperation•National Institute of Materials Physics,•Institute
of OPTOELECTRONICS •“Ovidius” University Constanta, •“Politehnica”
University, Bucharest, •Bochum University, •Commenius University,
Bratislava•Japan Ultra-high Temperature Materials Research
Institute
Group: “Elementary Processes in Plasma and Applications”Group
members involoved in project : 3PhD Researchers, 2 Researchers, 1
Graduated in Physics, 4 Technical staff, 4 Students,
NILPRP
Team : 1. Dr. Lungu P. Cristian 2. Dr. Mustata Ion, 3. Dr. Musa
Geavit 4.Dipl. Phys. Lungu Ana Mihaela, 5. Dipl. Eng. Phys. Chiru
Petrica, 6. Dipl. Phys Alexandu Anghel, 7.Techn. DragusinVasile, 8.
Techn. Ilie Florian, 9. Techn. Zaroschi Valer, 10. Techn Alexe
Dobrin, 11. Student Marius Badulescu, 12 Student Ionut Barbu.
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~ 700m2 Be first wall : low Z + Oxygen getter
~ 100m2 W Baffle/Dome : low erosion, long lifetime
~ 50 m2 CFC Divertor Targetno melting, C good radiator
ITER FW & Divertor Materials
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• The high priority issues for ITER • plasma operation with a
beryllium first wall• the use of tungsten as a plasma facing
component• the effects of material mixtures
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Some technology issues….
• Tungsten coating of CFCs - size, stresses, bending, testing at
20MWm-2
• Beryllium coating of CFCs - Some relevant experience available
but main problem is availability of industries -good exercise for
ITER
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Strips coated with very thin layerof Re plus 2-5 m of C + B
JG99.302/3c
Shadowed region of title
Divertor tiles-installed July 1999
Distance accurate to ~10 m(to measure erosion/
deposition greater than this)
Re
C + B
Tile (CFC)
Initial DepositionSmallerosion
Largeerosion
• “Smart” tiles
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Disposition of “smart” tiles in the vessel for 2005
Fast RH intervention has been analysed:6-8 weeks including
Restart
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The group developed an original technology called Thermionic
Vacuum Arc (TVA), suitable for nanostructured, multifunctional film
preparation
NILPRP
The anode consists of a crucible, filled with the material to be
deposited.
This assembly is mounted inside a vacuum vessel.
THERMIONIC VACUUM ARC (TVA) PRINCIPLE
An intense thermoelectronicemission from an heated cathode (a
tungsten filament) is focused by a Whenelt cylinder on the
anode.
W crucibleAnode
Cathode
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Position φ=0o
Whenelt cylinder
CATHODE
CATHODE
Position φ = 90o
φEvaporating material
Crucible(ANODE)
+
−HV
Whenelt cylinder
ELECTRODES CONFIGURATION
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TVA parameters
• Interelectrode distance
• Angle ϕ• Cathode
heating current (If)
Cathode
Material to be evaporated
φ
W crucible(Anode)
Whenelt cylinder
+-
HV
If
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I-V characteristics2
0.3
0.2
0.1
0.5
0.4
0.6
0 1 2 3 U (kV)
I (A)
1
Cu anode1 – d = 2,5 mm2 – d = 4,6 mm
ϕ = 0
3 U (kV)
Ti anode1 – d = 2,5 mm2 – d = 3,7 mm3 – d = 4,7 mm
ϕ = 0
3
0.3
0.2
0.1
0.5
0.4
0.6
0 1 2
I (A)
1
2
1 2 3
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Deposition rates measured versus discharge power for different
cathode heating current.
300 600 900 1200 1500 18000.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
If=26AIf=24A
If=22A
If=20AD
epos
ition
rate
, nm
/s
Discharge power, W
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Photograph of the Re ingot during deposition
Re
Mo
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Nb substrate
Re film
2 mm
Thickness:6.5 μm
Re deposition: time; 60 min, Current; 1000 mA, Voltage; 2.2 kV.
Deposition distance: 3 cm
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Re bulk : mainly metal + ReO2
Re : mainly metal + ReO2
Re-Cr : 7.9% Re + 92.1% Cr (Re0.08Cr0.92); Re : ReO2 mainly +
ReO3;Cr : 39.4% met. + 60.6% Cr2O3
Re-Cr-Ni : 3.2% Re + 45.0% Cr + 51.8 Ni (Re0.03Cr0.45Ni0.52); Re
: metal mainly + ReO2;
Cr : 65.0% metal + 35.0% Cr2O3; Ni : 77.9% metal + 22.1% NiO
Re bulk Re Re-Cr Re-Cr-Ni (5 min etching)
BE at.% BE at.% BE at.% BE at.%
Re 40.4 40.3 2.7 40.3 10.9 40.4 1.2
ReO2 43.2 (42.7) 2.2 (42.6) 9.3 42.7 1.3 (42.6) 0.5
ReO3 45.4 (44.6) 0.7
Re 42.8 (42.7) (42.6) (42.6)
ReO2 45.6 44.5 0.5 44.5 2.2 (44.6) 45.4 0.2
ReO3 47.8 46.7 0.2
Cr 574.3 574.3 10.0 574.4 16.7
Cr2O3 576.6 576.7 15.4 576.6 9.0
CrO2 576.3
Ni 852.7 852.7 16.9
NiO 854.4 854.7 4.8
Ni NiO
858.6861.4
5.52.4
29.6───Ni 2p3/2
25.725.4──Cr 2p3/2
Re 4f5/2
192.222.45.4
Re 4f7/2
XPSLine
ChemicalBonding/formula
Bindingenergy
XPS ANALYSIS
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Experiment/Sample name
J1 J2 K1 K2 L1 L2 M1 M2 N1 N2
Composition ofraw alloy Cr/Ni (at%)
33/67 33/67 33/67 33/67 33/67 33/67 25/75 25/75 25/75 25/75
Power of TVA gun for Cr/Ni (W)
540 540 530 530 600 600 580 580 580 580
Deposition distance for Cr/Ni (mm)
220 240 220 240 220 240 270 280 270 280
Power of TVA gun for Re (W)
0 0 1200 1200 1400 1400 1650 1650 1600 1600
Deposition distance for Re (mm)
110 120 110 120 110 120 90 100 90 100
CRUCIBLE PUROX on Graphite
PUROX on Graphite
PUROX on Graphite
PUROX on Graphite
PUROX on Graphite
PUROX on Graphite
PUROX on Graphite
PUROX on Graphite
PUROX on Graphite
PUROX on Graphite
Composition Re at%
0 49.3 61.27 51.66 61.73 47.44 64.08 32.97
Composition Cr at%
90.52 41.46 33.88 43.70 31.22 42.66 28.6 58.64
Composition Ni at%
9.48 9.19 4.85 4.64 7.05 9.9 7.32 9.18
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10 μm
Re40Cr
Nb
Cross-sectional SEM Image of Re-Cr film
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10 μm
Re30Cr10Ni
Nb
Cross-sectional SEM Image of Re-Cr-Ni film
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Performed works in 2005Preliminary Re, Ni, W, etc and Be
coatings on small size (3 cm
x 3 cm x 0.5 cm) samples (Nb, stainless steel, glass, graphite)
were performed in order to test the possibility to prepares such
kind of films. Were tested some working parameters as:
Anode crucible material compatible with (Re, W, Cr, Ni, etc):
The use of Re and W rod and TiB2 composite boat for evaporation
Intensity of the heating current of the filament;
Re, W, Ni, Cr or combinations of Re30Cr10Ni were prepared at
NILPRP and Be coatings on graphite were prepared at the Nuclear
Fuel Plant facilities in Pitesti.
The prepared coatings were analyzed using Scanning Electron
Microscopy (SEM), Atomic Force Microscopy (AFM), Electron
Dispersive X-ray analysis (EDX), nanoindentation, optical cross
sectional observation
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4 mm
Nb alloy
Re film
yx
Thickness: xy/d
x and y as in figure, and d is the ball diameter
Re film deposited at 5 cm distance: thickness: about 6 μm
Callowear method for thickness estimation
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4 mm
Nb alloy
Re film
Interface
Sample deposited at 3 mm distance, thickness: about 8 μm
Good contact between Re and Nb alloy at the interface
Profile measured by Mytutoyo profilometer.
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Re
Nbsuperalloy
SAED HRTEM SEM
Selected area diffraction (SAED), high resolution transmission
microscopy (HRTEM) and scanning electron microscopy (SEM) images of
the nanostructured Rhenium film deposited on Nb superalloy by
TVA
Nbsuperalloy
(Optical micrograph
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10 mm
Graphite sample coated with W.
W DEPOSITION
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AFM image of W film.
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0 100 200 300 400 500 600 700
0.5
1.0
1.5
2.0
W film
Graphite substrateLo
ad [m
N]
Indentation depth [nm]
Sample HU[N/mm2] We/Wtot[%] HUpl[N/mm2] hmax[μm] Y[GPa]
Substrate 158 24,81 205 0,692 6,0
W film 30 0.23 5700 0.250 80,0
Comparison of loading/ unloading nanoindentation curves.
Table 1 Nanoindentation results
The material parameters obtained on the graphite substrate and
the tungsten films are listed below in Table 1, where: - HU-
universal hardness (resistance against elastic and plastic
deformation)- We/Wtot – ratio of the elastic indentation work to
the total indentation work- HUpl – plastic hardness (resistance
against plastic deformation – equivalent of the so called Vickers
hardness-hmax – maximum depth at given maximum load. - Y =
E/(1-ν2), where E is the Young‘s modulus and ν is the Poisson‘s
ratio.
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Sample HU[N/mm2]
We/Wtot[%]
HUpl[N/mm2]
Hmax[μm]
Y[GPa]
Substrate(graphite) 158 24,81 205 0,692 6,0
W coating 30 0.23 5700 0.250 80,0
HU- universal hardness (resistance against elastic and plastic
deformation)
We/Wtot – ratio of the elastic indentation work to the total
indentation work
HUpl –plastic hardness (resistance against plastic deformation –
equivalent of the so called Vickers hardness (hardness calculated
from the kvazistatic measurement of the diagonal of the remaining
indentation print)
Hmax – maximum depth at given maximum load
Y = E/(1-ν2), where E is the Young‘s modulus and ν is the
Poisson‘s ratio
L- applied load
h- indentation depth
W coating (nano-indentation results)
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O C W --0
10
20
30
40
50
60
70
80
90
100
(%)
Auger element analysis (ReW coating on CFC - 25.07.05)
Oxygen (%) Carbon (%) Wolfram (%)
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O O C C W W05
101520253035404550556065707580859095
100
(%)
XPS analysis
O O after etching C C after etching W W after etching
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By using and Environmental Scanning Electron Microscope XL 30
ESEM PHILIPS, Fe samples of 30 mm x 30 mm x 3 mm, were analyzed.
The results show a pure W film without impurities. The scanning
area was of about 4 μm2 and depth analysis of about 3 μm.
The ESEM image of W film deposited on Fe sheet.
ESEM and EDAX analysis
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Typically EDAX analysis performed by the ESEM XL 30 device.
C and O are at low values
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Coating of graphite samples of 30 mm x 30 mm x 8 mm were
performed using the facilities of the Nuclear Fuel factory in
Pitesti. On the respective area, the Be thickness was found to be
in the range of 7.8 ± 0.2 μm.
Be coatings
A coated and an uncoated graphite sample.
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Works to be performed in 2006:Developing TVA technique for the
deposition of an interlayer (Re,
Ni, Cr or W) on Be tiles and an outer layer of > 5 microns of
Be.
1. To produce a series of metal (Re, Ni, Cr and W) and beryllium
layers on Be samples
2. To measure by XPS and/or other methods, e.g. EPMA, IBA, EDAX
the concentration of C and O and other impurity species in the Be
films on the metal interlayer deposited on Be tiles
3. To assess the surface structure by SEM after production and
after several months of storage in air.
4. To measure the thickness of the coatings and the adhesion to
metal.
5. To prove that the coatings will be of adequate quality and
fullycompatible with a metal interlayer on “smart” tiles.
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Time schedule:•Assessment of durability of the layers and the
influence of storage in air for 6 months: 31.03.2006•Determination
of surface structure by SEM after production and after storage for
3 and 6 months in air: 31.12.2005 and 31.03.2006•Coatings of
refractory metal/Be on Be tiles (30 cm x 30 cm x 3 cm) will be
performed (5 items). Technical report on the optimization of
deposition parameters of heavy metal/Be coatingson 30cm x 30 cm x 3
cm tiles will be prepared: 31.03.2006.•Heat flux tests to establish
the failure mode limit: 31.03.2006•Coatings of Be on “smart” tiles
(5-10 pieces) (Euratom/MEdCassociation) and tests. •Final technical
report: 30.06.2006
TVA parametersI-V characteristics