High flux irradiations of Li coatings on polycrystalline W and ATJ graphite with D, He, and He-seeded D plasmas at Magnum PSI

Abstract Lithium wall conditioning on PFCs (Plasma Facing Components) on a variety of substrate platforms (e.g. graphite, Mo, etc.) has resulted in improved plasma performance on multiple magnetic fusion devices. On graphite, this improvement occurs through the control of retention and recycling of hydrogen at the plasma-material interface by the chemical bonding of Li, O, and D at the surface. Moderate fluence (1 × 10²¹ m^-2) studies of Li on W, performed in PRIHSM (Particle Radiation in Soft and Hard Matter), demonstrated that H retention is similar to Li on ATJ graphite but He ions, when mixed in a D beam, can inhibit the retention. To expand these studies closer to reactor relevant regimes like inside ITER, irradiations were carried out in Magnum-PSI at DIFFER up to fluences of ∼10²⁵ m^-2 with D, He, and He-seeded D plasmas (He 5-10%). Results show that D is still retained at higher fluxes and fluences.