Design and Analysis of an Actively Cooled Window for a High-Power Helicon Plasma Source

The material's plasma exposure experiment (MPEX) is a steady-state, linear plasma facility proposed to provide plasma conditions that simulate the first wall and divertor of the next-step fusion devices. MPEX will use an actively cooled, high-power helicon antenna as a plasma source. The antenna is located outside of the vacuum region, and during operation, a significant percentage of the antenna power is deposited on the plasma facing surface of the antenna window. The window thus must be actively cooled so that thermal stresses do not become excessive. The design presented includes two cylindrical windows with an annular water passage in-between in order to allow active cooling. A ceramic-to-metal seal is proposed in order to produce a water-to-vacuum seal that will not outgas and produce impurities. Experimental results from an uncooled window on a short-pulse prototype experiment are modeled using finite-element (FE) results in order to correlate with the heat flux profile. The design of the actively cooled window assembly is presented with computational fluid dynamics and FE analyses to confirm that the hardware can function with a 200-kW antenna within performance limits.