P1–37: Calibrated cathode temperature measurements using an IR pyrometer

Accurate cathode temperature measurements in a vacuum have been an engineering problem since the advent of the vacuum electron device (VED) over 100 years ago. Cathode temperatures are commonly characterized in a bell jar using various IR pyrometer instruments, but the resulting data is typically qualitative as opposed to the quantitative data that is needed for long term quality control of cathode fabrication processes. Temperature measurements using an IR pyrometer are susceptible to errors, which can be corrected by knowing the cathode surface IR band emissivity and bell jar glass IR band transmissivity. This paper discusses a laboratory technique for determining the emissivity for a cathode surface, and using this information to correct IR pyrometer measurements of the cathode surface temperatures.