AIP Digital Archive
Electrical Engineering, Measurement and Control Technology
Using optical spectroscopy we study the spatial and temporal distributions of the Hα, Cs i(4555 A(ring)), Cs ii(4604 A(ring)), and Mo i(3903 A(ring)) emission lines in a Penning surface-plasma source (SPS). A diagnostic slit exposes the entire SPS discharge gap either parallel or perpendicular to the magnetic field. The spatial and temporal distributions of the emitting species are recorded using a 1-m monochromator. In addition, the visible light and the Hα and Cs ii(4604 A(ring)) spatial distributions are recorded with a video camera. The cesium atomic and ionic light, and the molybdenum atomic light, is strongly concentrated near the cathodes; the visible light and the Hα light is almost uniform in both directions. Electron-impact ionization of atoms sputtered from the cathodes and the return of the ions to the cathodes by residual plasma fields is probably the mechanism which concentrates cesium near the cathodes. The Cs0 mean free path is estimated to be 16 and 0.43 mm for 2 and 400 A discharges, respectively.
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