Optical probes for cathode characterization

Optical multichannel detection is used to obtain spatially resolved Raman spectra from dispenser cathode surfaces in vacuum and at elevated temperatures. A simple test chamber allows collection of cathode Raman spectra at 10^-9torr and at temperatures as high as 860°C. Spatial resolutions on the order of 10 micrometers are demonstrated. While we are unable to provide a definite assignment of the primary chemical species responsible for the cathode spectra measured at elevated temperatures in vacuum, we suspect it to be a tungsten oxide.