Evaluation of Neutron Irradiated and Pristine Materials Under L-mode DIII-D Discharges

A novel, angled holder containing pristine W, K-doped W, TiB₂, and neutron irradiated W was exposed to 16 L-mode discharges with 0.4 MW/m² peak perpendicular heat fluxes in DIII-D using the Divertor Materials Evaluation System (DiMES) to compare plasma-material interaction (PMI) response of materials and delineate how neutron damage impacts defect evolution and hydrogenic retention behavior in W. Post-exposure imaging found no significant macroscopic damage from the discharges. The pre-irradiated W sample was damaged with thermal neutrons from ORNL’s High Flux Isotope Reactor to 0.5 dpa at 850°C. During DIII-D plasma exposures, samples were heated to a peak temperature of ~500°C from ohmic discharges to build up plasma fluence without heating the samples past the irradiation temperature to prevent neutron-induced defect annealing. Surface morphology evolution and defect formation will be characterized along with total retained deuterium and deuterium desorption temperatures to directly compare PMI performance between advanced and pre-damaged materials. PMI and neutron degradation are often studied separately due to experimental complexities involved in handling and characterizing neutron irradiated materials, leaving an incomplete picture of how materials will behave in a true, multi-conditional, FPP-type environment. This work addresses these uncertainties through plasma exposures and characterization of both pristine and pre-irradiated plasma facing material candidates.