2024 – Examination of surface stability of dispersion-strengthened tungsten divertor plasma exposure in DIII-D

Examination of surface stability of dispersion-strengthened tungsten divertor plasma exposure in DIII-D

2024 Research Campaign, Thrust: FPP Candidate Wall Materials

Purpose of Experiment

This experiment will compare the surface stability of Dispersion-Strengthened Tungsten (DSW) materials in a heated tokamak divertor environment, with standard and helium implanted DSW samples previously tested on DIII-D at ambient temperature. (MP 2024-2502). Tungsten will be dispersion-strengthened with TiC, TaC, and ZrC nanoparticles and consolidated via spark-plasma sintering. Surface stability will be evaluated via crack propagation and recrystallization, and in-situ sputtering measurements.

Experimental Approach

This work has two primary objectives: (1) Evaluate the surface stability of DSW materials and compare with the results of identical discharge parameters (MP 2024-25-02) under high temperature using heated DiMES. (2) Further characterize preferential erosion of DSW in-situ using WiSE. The first DiMES probe will be used to accomplish Objective (1). A heated 7-button holder will be used with a combination of flush and angled buttons. The subsequent single angled holders will be used towards Objective (2). The main variable for the first DiMES head is temperature, while the subsequent discharges will be used for in-situ erosion analysis. Following the exposure of the 7-button heated holder, two separate large angled disks will be exposed to two discharges each. Each discharge in this experiment will be an identical discharge to the initial. Prior to and post exposure, all samples will be polished to a mirror f inish and analyzed via energy dispersive spectroscopy (EDS) for composition. Fiducial markers will be made on one of each DSW sample prior to exposure in DIII-D using a focused ion beam (FIB) to define a region of interest on the sample surface that can be referenced after exposures. The areal density of carbide dispersoids will be counted prior to the samples being sent to DIII-D and confirmed with EDS.