The Final Design of the Plasma–Material Interaction Chamber for the Material Plasma Exposure eXperiment

The Material Plasma Exposure eXperiment (MPEX) is a steady-state linear plasma device designed to expose neutron-irradiated materials to fusion divertor prototypic plasma conditions to perform plasma-material interaction (PMI) studies. The MPEX device will be capable of ion fluxes of 1025 m−2s−1, power fluxes up to 40 MW/m2, ion fluences up to 1031 m−2, and operation at steady state for up to 106 s with magnetic fields up to 2.5 T. PMIs occur when the plasma directly impinges upon a surface. In the case of MPEX, this occurs primarily at the MPEX target. Observation of interaction using a variety of instruments is required. A PMI chamber was designed to enable these observations using currently envisioned diagnostics and to accommodate future instruments. The design includes 59 plasma-facing ports, 10 of which explicitly point at the target, and an additional 10 ports that can be used to assess the vacuum space in the chamber. The entire vacuum chamber is water-cooled and will experience sustained heat from plasma radiated power, microwaves, and neutral gas thermal loads. Because of the method of fabrication, this chamber has undergone significant manufacturability testing. The chamber includes provisions for chamber, plasma, and target diagnostics such as a residual gas analyzer, Thomson scattering lasers, and both visible and IR cameras. The design effort included operational testing of the autocoupler to ensure vacuum integrity and included machining and welding studies to verify that the tolerances required by the diagnostics could be held. Provisions have also been included to eventually accommodate a water-cooled target dump, an irradiated sample recovery module, and any other hardware needed to support future target designs and diagnostics.