Differential pumping in the linear plasma generator Magnum-PSI

摘要

The design and construction of the vacuum system of the linear plasma generator Magnum-PSI has been completed. In Magnum-PSI, the neutrals are separated from the plasma with the use of skimmers in a differentially pumped vacuum system. A strong axial magnetic field confines the ionized species to beam which is guided through the skimmers from the source to the target. The neutrals, which are mostly on the edge of the beam, are scraped off and pumped away. Direct Simulation Monte Carlo (DSMC) calculations and experiments using cold gas as a test case have been performed. A factor of 8 pressure reduction has been achieved while using skimmers with an opening of 10 cm diameter. The results agree well with the simulations and the good working of the differentially pumped vacuum system is confirmed. This will enable plasma-surface interaction (PSI) research in the ITER relevant regime.