VDU/LEI project in FUSION: background, goals, methods and expected results

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• VDU/LEI project in FUSION background, goals,
  methods and expected results
• (PhD student Birute Bobrovaite, Dr. Liudas
  Pranevicius)

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Project title Characterisation of W-Coatings
for Fusion Applications

• Project duration 30 months originated from 2006
  01 01
• The project is coordinated by
• the Materials Research and Testing Laboratory,
• Lithuanian Energy Institute, Kaunas.
• The project partner is
• the Physics Department of the
• Vytautas Magnus University, Kaunas.

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Outline of the presentation

• Goals of the work
• Work package
• Expected results.

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Main problem

• Mechanism of restructuring and surface
  relocations under high-flux irradiation at
  elevated temperatures.
• Material erosion by continuous or transient
  plasma ion and neutral impact, the subsequent
  transport of the released impurities through and
  by the plasma and their deposition and/or
  eventual re-erosion constitute the process of
  migration.
• Due to erosion mechanism and re- deposition
  materials will interact on plasma facing
  surfaces.
• ....is to understand physical phenomena of
  mechanical properties of W and to reduce the
  impurities in the main chamber

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• The goal of the research is
• the fabrication of W films to be used in
  plasma-facing components in fusion devices, and
  the understanding of the mechanism of physical
  phenomena initiating modifications of mechanical
  properties of W-based thin films on carbon based
  substrates under high-flux, low-energy H ions
  irradiation in the range of temperatures up to
  1000C.

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Descriptions of work

• Fabrication of W coatings by magnetron sputter
  deposition
• Structural and compositional investigation of W
  coatings
• Plasma/ion beam H exposure of W coatings
• Studies of W coatings properties after hydrogen
  ion irradiation
• Modelling of the surface restructuring and
  re-deposition effects in W film under high-flux,
  high-fluence, low-energy hydrogen ion
  irradiation

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Fabrication of W films

• Magnetron sputter deposition of W films on carbon
  based substrates.
• Thickness 3-10 ?m.
• The film surface area 17 ? 20 cm.
• Thickness homogeneity better than 20.

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Irradiation experiment

• Extraction of ions from thermionic arc plasma
  generated in hydrogen working gas.
• Pulsed plasma immersion hydrogen ion implantation
  using acceleration voltage up to 500 V.
• Hydrogen beam implantation using Kauffman ion
  source (2-5 mA?cm-2, 300 eV) using facilities of
  the Poitiers University (France).

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Characterization

• Microstructure and grain size of films by XRD
  analysis
• Surface morphology analysis using SEM and AFM
  analysis
• Film and interface compositional analysis using
  glow discharge optical emission spectrometry
  (GDOES) analysis
• Film resistivity measurements using four probe
  method
• Film thickness homogeneity analysis using large
  area laser interferometry views
• Studies of film nano-hardness and film erosion
  properties in collaboration with the Laboratory
  of Metallurgic Physics of the Poitiers University
  (France).

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Modelling

• It is planned to consider surface redeposition
  and reconstruction effects on composition and
  structure of W films initiated H irradiation.
• The modelling includes three processes
• surface diffusion (thermally activated process),
• ballistic surface atom relocation (ion
  irradiation activated process)
• and redeposition of sputtered atoms (W atoms,
  oxygen, etc.) arriving from plasma.

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Expected results

• To form dense nanocrystallline thin W films
  (optimization of film deposition parameters for
  thickness and homogenity of W films)
• To investigate structure and composition of W
  cotings
• To commit iradiation experiments
• To model surface redoposition and reconstruction
  effects on composition and structure of W films
  initiated initiated H irradiation.

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Work package list

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Thank You for your attention