Tungsten Coatings on an Actively-cooled, Additively-manufactured, Reciprocating Probe in the Long-pulse WEST Device

WEST (Tungsten, W, Environment in Steady-state Tokamak) is an actively-cooled tokamak operating with dual goals of sustaining long-pulses and qualifying ITER-like plasma-facing components. A reciprocating probe system is being designed for WEST to support these goals, including embedded temperature sensors and removable sample slots for ex-situ surface analysis of plasma-material interactions. This presentation focuses on the coating methods used to armor the probe. The compact nature and extreme exposure conditions needed for the probe result in novel build solutions coupled with careful design analysis. Overall, this probe is 2.6 m long and ~0.05 m in diameter and can translate linearly into the vacuum chamber up to ~0.5 m. The probe end closest to the confined plasma encompasses 0.35 m of the overall length and houses the samples. In this region, the limited space, integral cooling, and linear actuator needs have pushed the design to additive manufacturing, allowing for precision cooling-channels and compactness. This probe-end is manufactured with a copper-alloy (GRCop-42) coated in a thin W coating. The coating method and thickness is being optimized for its thermomechanical properties, i.e., balance between thin coatings for resilience to delamination and thicker coatings for extended lifetime. We are following a multi-step validation process to ensure the coating integrity on GRCop that includes off-line high-heat flux exposures on test articles and microstructural analysis of the coating.