Plasma-facing material

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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 the first wall or divertor region of the reactor vessel.

Plasma-facing materials for fusion reactor designs must support the overall steps for energy generation, these include:

1. Generating heat through fusion,
2. Capturing heat in the first wall,
3. Transferring heat at a faster rate than capturing heat.
4. Generating electricity.

In addition PFMs have to operate over the lifetime of a fusion reactor vessel by handling the harsh environmental conditions, such as:

1. Ion bombardment causing physical and chemical sputtering and therefore erosion.
2. Ion implantation causing displacement damage and chemical composition changes
3. High-heat fluxes (e.g. 10 MW/m${\displaystyle ^{2}}$) due to ELMS and other transients.
4. Limited tritium codeposition and sequestration.
5. Stable thermomechanical properties under operation.
6. Limited number of negative nuclear transmutation effects

Currently, fusion reactor research focuses on improving efficiency and reliability in heat generation and capture and on raising the rate of transfer. Generating electricity from heat is beyond the scope of current research, due to existing efficient heat-transfer cycles, such as heating water to operate steam turbines that drive electrical generators.

Current reactor designs are fueled by deuterium-tritium (D-T) fusion reactions, which produce high-energy neutrons that can damage the first wall,^[1] however, high-energy neutrons (14.1 MeV) are needed for blanket and Tritium breeder operation. Tritium is not a naturally abundant isotope due to its short half-life, therefore for a fusion D-T reactor it will need to be bred by the nuclear reaction of lithium (Li), boron (B), or beryllium (Be) isotopes with high-energy neutrons that collide within the first wall.^[2]