Wall and Plasma-Material Interaction Codes
PMI codes model erosion, deposition, fuel retention, and material evolution at surfaces where the plasma meets the wall.
The plasma-material boundary
Where the plasma touches material surfaces, ions and neutrals sputter atoms from the wall, deposit them elsewhere, and implant fuel into the near-surface layer. Plasma-material interaction (PMI) codes model this exchange, predicting how surfaces erode and grow, how much tritium is retained in the wall, and how impurities released from surfaces contaminate the plasma.
PMI spans many scales, from the atomic collisions of a single incident ion to the slow evolution of a surface over a campaign, so it is addressed by a family of coupled codes rather than one tool.
Sputtering and migration
Incident ions eject wall atoms via collision cascades, modeled by binary-collision or molecular-dynamics sputtering codes. The eroded atoms enter the plasma, are transported, and redeposit, so a migration model tracks the net erosion and deposition pattern across the whole first wall.
Fuel retention
Hydrogen isotopes implant into and diffuse through the wall, trapping at defects. For a deuterium-tritium device this governs the tritium inventory locked in the wall, a safety and fuel-accounting quantity. Diffusion-trapping codes predict retention and the release under heating.
Design relevance
For the deuterium-tritium Hyperion breeder, PMI modeling estimates first-wall lifetime, impurity influx, and tritium retention, quantities that bear on the tritium breeding ratio target of 1.8 and on component design. All are simulation studies preceding construction, with material behavior confirmable only in operation.
- Models erosion, deposition, and retention
- Spans atomic collisions to campaign-scale evolution
- Couples sputtering, migration, diffusion-trapping
- Sets first-wall lifetime and tritium inventory