Plasmafacing

Plasmafacing refers to the surfaces of a fusion device or other plasma experiment that are in direct contact with the hot plasma. These surfaces are part of plasma-facing components (PFCs) such as the first wall, divertor targets, limiters, and antenna protection. They are designed to withstand extreme heat fluxes, particle bombardment, neutron irradiation, and rapid thermal cycling while minimizing contamination of the plasma and tritium retention.

Materials used for plasmafacing surfaces are chosen for high melting point, low sputtering yields, and compatibility with the reactor environment. Common options include tungsten, beryllium, and carbon-based composites. Tungsten is favored for high-temperature resilience and low erosion in many regions, but is a high-Z material that can radiate if eroded into the plasma. Beryllium has favorable low-Z properties for the main chamber in some designs, while carbon-based materials offer good thermal shock tolerance but pose challenges for fuel retention. Research also explores liquid metals and other advanced coatings to reduce erosion and enable self-healing surfaces.

Key challenges in plasmafacing include extreme and localized heat loads, transient events such as edge localized modes and disruptions, surface erosion and arcing, and neutron-induced damage. Impurity influx from PFCs can degrade plasma performance, and tritium retention in certain materials is a safety and efficiency concern. PFCs require active cooling, robust vacuum compatibility, and reliable diagnostics to monitor surface condition and heat transfer.

In current fusion programs, plasmafacing materials and surfaces are a central area of PMI (plasma-material interaction) research, informing design choices for devices like ITER and various tokamaks worldwide.