Divertor Target Materials
The divertor takes the concentrated exhaust load; tungsten-class materials are studied there for the highest power-handling margin.
Where the exhaust goes
The divertor is the region designed to receive the plasma's exhausted heat and particles at controlled locations, rather than letting them strike the main wall. Its targets see the highest concentrated heat flux in the machine, so they are studied with the highest-melting-point, best-conducting refractory metals, typically tungsten-class materials.
Tungsten versus carbide
Tungsten offers very high melting point plus good thermal conductivity, which is why it dominates divertor studies. Compared with the hafnium-carbide first wall, tungsten conducts heat better but is itself a high-Z impurity if eroded. The two regions can use different materials because they face different loads: broad radiated flux on the wall, concentrated particle flux on the divertor.
- Highest concentrated heat flux in the machine.
- Tungsten-class targets for melting point and conductivity.
- High-Z erosion penalty if material reaches the core.
- Negative triangularity chosen partly to ease this exhaust.
Coupled to plasma shape
Divertor loading depends strongly on how the plasma is shaped and how power is spread before it reaches the target. The breeder's -0.30 triangularity is chosen in part to help manage edge and exhaust behavior. Divertor material choice and plasma shape are designed together, not separately.
Recrystallization and embrittlement
Tungsten under high heat and neutron dose can recrystallize and shift its ductile-to-brittle transition, degrading the toughness that made it attractive. These evolving properties, not just fresh performance, set divertor target life, so the material is qualified against its irradiated, thermally-cycled state rather than its as-manufactured condition.
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.