Bvalues describe: boronisation
Fusion, privateBig science (accelerators, light sources, public fusion)
Why it wins
Sacrificial gettering films (boronization by diborane, lithium evaporation) buy oxygen pumping and low recycling that a tungsten wall no longer provides for free.
Why not the alternative
Permanent getters cannot survive plasma contact: the consumable film is the design.
Watch out
An operations discipline, not a component: chemistry per campaign.
Properties
The values below are candidate: compiled from the sources named, not yet individually validated.
Provisional provenance: ITER and JET ITER-like wall programme; EUROfusion and international fusion materials programmes.
Wet cleaning
| Recipe | not applicable: the wall is conditioned in situ by glow discharge or evaporation, not washed |
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| Forbidden | the whole point is that you cannot open the machine to clean it |
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| Limit | campaign length, and the tritium inventory the film retains |
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Vacuum and outgassing
| Outgassing, unbaked (10 h) | pumps hydrogen and oxygen |
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| Vapour pressure | lithium evaporates readily, which is the mechanism |
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Temperature
| Bake, assembled | in-vessel, machine dependent |
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| Metallurgical limit | the film is consumed and reapplied each campaign |
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Thermal
| Melting / softening | 2076 (B) °C |
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Mechanical
| Strength | film |
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| Elongation | nil |
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| Density | 2.34 g/cm3 |
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Engineering
| Joining | deposited on the whole inner wall |
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| Process notes | a consumable surface, renewed between campaigns |
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| Availability and cost | tokamak practice |
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Grades
| Diborane diluted in He, glow discharge | the ITER-class boronization consumable |
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| Li evaporation | low recycling campaigns, spherical tokamak and stellarator practice |
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| B powder injection (impurity powder dropper) | real-time boronization without glow discharge: DIII-D, ASDEX-U, EAST practice |
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Sources · 1
- IAEA FEC 2025 synopsis, W wall and boronization
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