Interior of Alcator C-Mod showing the molybdenum tiles used as first wall material

Interior of Tokamak à configuration variable showing the graphite tiles used as first wall material

In nuclear fusion power research, the plasma-facing material (or materials) (PFM) is any material used to construct the plasma-facing components (PFC), those components exposed to the plasma within which nuclear fusion occurs, and particularly the material used for the lining or first wall of the reactor vessel.

The core fusion plasma must not actually touch the first wall. ITER and many other current and projected fusion experiments, particularly those of the tokamak and stellarator designs, use intense magnetic fields in an attempt to achieve this, although plasma instability problems remain.

Even with stable plasma confinement, however, the first wall material would be exposed to a neutron flux higher than in any current nuclear power reactor, which leads to two key problems in selecting the material:

• It must withstand this neutron flux for a sufficient period of time to be economically viable.

  【辐照对钨中氘、氦渗透扩散行为及热解吸行为的影响研究】
  

• It must not become sufficiently radioactive so as to produce unacceptable amounts of nuclear waste when lining replacement or plant decommissioning eventually occurs.

The lining material must also:

• Allow the passage of a large heat flux.

• Be compatible with intense and fluctuating magnetic fields.

• Minimize contamination of the plasma.

• Be produced and replaced at a reasonable cost.

Some critical plasma-facing components, such as and in particular the divertor, are typically protected by a different material than that used for the major area of the first wall.^[1]

Materials currently in use or under consideration include:

• Boron carbide.^[2][3]

• Graphite.

• Carbon fibre composite (CFC).^[3]

• Beryllium.

• Tungsten.

• Molybdenum.

Multi-layer tiles of several of these materials are also being considered and used, for example:

• A thin molybdenum layer on graphite tiles.

• A thin tungsten layer on graphite tiles.

• A tungsten layer on top of a molybdenum layer on graphite tiles.

• A boron carbide layer on top of CFC tiles.^[3]

Graphite was used for the first wall material of the Joint European Torus (JET) at its startup (1983), in Tokamak à configuration variable (1992) and in National Spherical Torus Experiment (NSTX, first plasma 1999).^[4]

Beryllium was used to reline JET in 2009 in anticipation of its proposed use in ITER.^[5]

Tungsten is used for the divertor in JET, and will be used for the divertor in ITER.^[5] It is also used for the first wall in ASDEX Upgrade.^[6] Graphite tiles plasma sprayed with tungsten were used for the ASDEX Upgrade divertor.^[7]

Molybdenum is used for the first wall material in Alcator C-Mod (1991).

Development of satisfactory plasma-facing materials is one of the key problems still to be solved by current programs.

The International Fusion Materials Irradiation Facility (IFMIF) will particularly address this. Materials developed using IFMIF will be used in DEMO, the proposed successor to ITER.

French Nobel laureate in physics, Pierre-Gilles de Gennes said of nuclear fusion, "We say that we will put the sun into a box. The idea is pretty. The problem is, we don't know how to make the box."^[8]

• International Fusion Materials Irradiation Facility#Background information.

• http://www.ipp.mpg.de/ippcms/eng/for/projekte/pfmc/index.htmlMax Planck Institute project page on PFM

• http://www.ipp.mpg.de/ippcms/eng/for/veranstaltungen/konferenzen/archiv/2011/03pfmc-13/index.html 13th International Workshop on Plasma-Facing Materials and Components for Fusion Applications / 1st International Conference on Fusion Energy Materials Science

• http://www.sciencedirect.com/science/article/pii/S0920379611004273 retrieved 10 September 2012 Abstract: The paper gives a short overview on tungsten (W) coatings deposited by various methods on carbon materials (carbon fibre composite – CFC and fine grain graphite – FGG). Vacuum Plasma Spray (VPS), Chemical Vapor Deposition (CVD) and Physical Vapor Deposition (PVD)... A particular attention is paid to the Combined Magnetron Sputtering and Ion Implantation (CMSII) technique, which was developed during the last 4 years from laboratory to industrial scale and it is successfully applied for W coating (10–15 μm and 20–25 μm) of more than 2500 tiles for the ITER-like Wall project at JET and ASDEX Upgrade.... Experimentally, W/Mo coatings with a thickness up to 50 μm were produced and successfully tested in the GLADIS ion beam facility up to 23 MW/m2. Keywords: Tungsten coating; Carbon fibre composite (CFC); ITER-like wall; Magnetron sputtering; Ion implantation