Negative Triangularity — the Materials Payoff
The -0.30 triangularity shape is chosen partly to ease heat and particle loads on plasma-facing materials, coupling plasma shape to component life.
Shape as a materials decision
The breeder runs a negative-triangularity plasma with triangularity -0.30. This is usually discussed as a physics choice, but it is also a materials decision: the shape influences how power and particles reach the first wall and divertor, and therefore how hard the materials there have to work. Easier edge loading means longer component life.
Why it can help the wall
Negative triangularity can suppress some edge instabilities that otherwise dump energy onto plasma-facing surfaces in bursts, and it can change how exhaust power is spread. For brittle refractories such as the hafnium-carbide first wall, avoiding sharp transient loads matters as much as the steady flux, because thermal shock drives cracking. A gentler edge is a longer-lived wall.
- Edge stability affects transient loads on the first wall.
- Exhaust spreading affects divertor target loading.
- Brittle refractories are sensitive to thermal-shock transients.
- Shape and material life are designed together.
A coupled optimization
Choosing -0.30 triangularity balances plasma performance against materials loading and control difficulty. The poloidal-field system must work harder to hold the shape, and that cost is accepted partly for the materials benefit. Plasma shape, first-wall material, and divertor design are one optimization, not three independent choices.
The control cost is accepted
Holding a -0.30 shape demands more from the poloidal-field system and control margin than a conventional positive-triangularity plasma, because the equilibrium is less naturally stable. The breeder accepts that control cost deliberately, in part for the gentler edge loading it gives the first wall and divertor, treating shape as a materials-life investment.
This page documents a design and simulation study, not a built machine. Construction begins Q2 2027; first-of-a-kind first tritium is targeted near 2030. Figures are computed, reproducible targets, not measurements.