Neon-induced suppression of deuterium retention in tungsten: Effects of temperature and Ne concentration

Neon (Ne) seeding is a key strategy for radiative cooling in the divertor to mitigate extreme thermal loads and protect plasma-facing materials in future fusion devices. This study investigates the effects of Ne seeding on tungsten (W) surface morphology and deuterium (D) retention under plasma irradiation conditions relevant to fusion reactors. Experiments were conducted using W samples exposed to pure D, sequential D-Ne (Ne pre-irradiation followed by D exposure), and mixed D-Ne plasmas with different Ne concentrations, at temperatures of 500 K and 1200 K with ion fluxes of 1.0×10 22 m -2 s -1 and 1.2×10 24 m -2 s -1 , respectively, in the linear plasma facilities PSI-2 and Pilot-PSI. At low temperature (500 K), sequential D-Ne irradiation significantly increases surface roughness and completely suppresses D-induced blister formation. In contrast, mixed D-Ne irradiation under identical conditions leads to micron-sized blisters with fractured caps. At high temperatures (∼1200 K), mixed D-Ne irradiation entirely prevents blister formation, whether the Ne concentration is 5% or 20%. In addition, under the exposure conditions employed in this study, Ne seeding consistently resulted in a reduction in D retention. At 500 K, D retention decreased by up to 50%, whereas at 1200 K, it was reduced by approximately 30% for 5% Ne concentration and dropped below the detection limit for 20% Ne concentration. The suppression of deuterium retention in tungsten due to neon seeding is attributed to sputtering-induced surface erosion and the Ne-vacancy complexes that pin the trapped D atoms, thereby inhibiting blister formation. These findings underscore the potential of Ne as an effective radiative cooling impurity in fusion devices and provide valuable insights into optimizing the performance of plasma-facing materials.