Two-dimensional laser collision-induced fluorescence mapping of electron density and temperature near plasma cathode apertures

Summary form only given. Laser collision-induced fluorescence (LCIF) diagnostics are used to generate two-dimensional images of electron density and temperature inside a RF helium plasma cathode setup, near the electron extraction aperture. During electron current extraction, a region of dense plasma is seen at the aperture, and this aperture plasma is often surrounded by a layer of high-temperature electrons. Density and temperature profiles are imaged at variable gas pressure, applied bias, and aperture size. The properties of the aperture plasma are compared with those in the bulk plasma, using LCIF and probe diagnostics. Because this aperture plasma acts as an interface between the internal bulk plasma and the downstream extraction anode, an understanding of these behaviors may prove useful when optimizing plasma cathodes for more efficient current extraction.