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

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.

~ 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

• 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

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

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

Disposition of “smart” tiles in the vessel for 2005

Fast RH intervention has been analysed:6-8 weeks including Restart

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

Position φ=0o

Whenelt cylinder

CATHODE

CATHODE

Position φ = 90o

φEvaporating material

Crucible(ANODE)

+

−HV

Whenelt cylinder

ELECTRODES CONFIGURATION

TVA parameters

• Interelectrode distance

• Angle ϕ• Cathode

heating current (If)

Cathode

Material to be evaporated

φ

W crucible(Anode)

Whenelt cylinder

+-

HV

If

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

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

Photograph of the Re ingot during deposition

Re

Mo

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

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

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

10 μm

Re40Cr

Nb

Cross-sectional SEM Image of Re-Cr film

10 μm

Re30Cr10Ni

Nb

Cross-sectional SEM Image of Re-Cr-Ni film

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

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

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.

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

10 mm

Graphite sample coated with W.

W DEPOSITION

AFM image of W film.

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.

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)

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 (%)

O O C C W W05

101520253035404550556065707580859095

100

(%)

XPS analysis

O O after etching C C after etching W W after etching

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

Typically EDAX analysis performed by the ESEM XL 30 device.

C and O are at low values

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.

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.

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