First Wall & Plasma-Facing Components

The first wall and plasma-facing surfaces take the plasma's heat and particle flux; in the low-neutron burner they see less neutron damage than a D–T machine.

The first wall is the innermost surface facing the plasma. It receives radiated power, charged-particle flux at the edges, and the neutron flux from the 5.44% neutron fraction. Its job is to survive those loads without releasing impurities into the plasma or eroding faster than the maintenance interval allows. Plasma-facing components (PFCs) include the first wall, limiters or edge armor, and the surfaces near the heating launchers.

Compared with a D–T machine the burner's first wall has an easier neutron environment — 5.44% versus roughly 80% neutronic — which reduces neutron-induced damage and activation. But it still faces heat and particle flux, and the exhaust ends carry the concentrated end-loss stream before it reaches the expander. Material choice balances heat handling, low sputtering, and low activation.

What PFCs must handle

• Radiated power from the plasma across the wall
• Charged-particle flux at the plasma edge
• Neutron flux from the 5.44% fraction
• Low sputtering to keep impurities out of the plasma
• Erosion within the maintenance and replacement interval

Advantage and limit

The low neutron fraction is a genuine advantage: less neutron damage means longer component life and less activated waste than D–T. It is not immunity — activation and damage still occur and must be planned for. First-wall condition is monitored in operation, and PFC replacement is part of the maintenance program that feeds the availability gate.

All figures are design-and-simulation values for a machine not yet built.