Speaker
Description
A reciprocating, actively water-cooled probe is currently under development to be deployed in the WEST tokamak for long pulse/high fluence plasma-material interaction (PMI) and materials transport studies. The WEST long-pulse probe (LPP) probe head will be composed of tungsten coated onto an additively manufactured advanced Cu alloy, GRCop-42, body. GRCop-42 was selected as the primary structural material for the LPP head due to its desirable thermal and mechanical properties under anticipated operation temperatures (RT - 250$^\circ$C) and its suitability for powder-bed laser melting additive manufacturing, allowing for the development of complex geometry components. Tungsten coatings were chosen both to prevent foreign elemental contamination in WEST tokamak and due to their applicability to next-generation tokamaks such as ITER and SPARC which will utilize primarily tungsten-based plasma facing components. W coatings will be applied by plasma-enhanced chemical vapor deposition utilizing a nickel interlayer to ease dramatic biaxial stresses in the W coating-GRcop interface, stemming from CTE mismatch between the materials.
To qualify these advanced materials and manufacturing processes for long-pulse operation in WEST, e-beam heat flux testing is planned utilizing the High heAt load tESt (HADES) facility at CEA-IRFM on LPP test articles that mimic actual probe flow channel geometry and operation. Test articles will include non-coated GRCop-42 articles and articles with varied thicknesses, 10 and 20 $\mu$m, of W coatings to: 1) Demonstrate delamination/spalling resilience of W-coatings to cyclic thermal stresses beyond what probe materials will endure (~1000 cycles, 10 second, 1.75 MW/m$^2$ pulses) and 2) Characterize coating and substrate material degradation under intense, low-cycle thermal stresses to predict material cycle limits and possible failure mechanisms under fusion-relevant thermal conditions. This work summarizes efforts made thus far to develop the WEST LPP design, e-beam heat flux testing of WEST probe test articles, and the WEST LPP science mission during operation.