Measuring current emission and work functions of large thermionic cathodes

We have constructed a small facility called the Cathode Test Stand (CTS) to investigate engineering and physics issues regarding large thermionic dispenser-cathodes. In particular, we have looked at the issues of temperature uniformity on the cathode surface and cathode quality as measured by its work function. We have done thermal imaging of both 8" and 6.5" cathodes. Here we report on measurements of the cathode work function, both the average value and how it varies across the face of the cathode.