A practical method of evaluating work functions

In this report we present the experimental data and the step-by-step technique to evaluate the work functions of thermionic cathodes. The thermionic cathodes utilized here were small, almost button size, and were provided by the Spectra-Mat corporation [1]. The experiments were performed by one of us, Erik Jongewaard, at Stanford Linear Accelerator Laboratory (SLAC). We would like to emphasize that among other parameters, the cathode electron current emission work function is of paramount importance for selecting the cathode for many applications and specifically for the injector of linear induction accelerators similar to DARHT II and most recently for the new radiographic accelerators under consideration.