A new method, the capillary method, is described here for fabricating ThC cathodes. Each cathode consists of W–Re tubing containing a W‐dendrite matrix filled with dense ThC–W eutectic. Hundreds of these cathodes have been used as sources for electron guns which require zero field emission capability of several A/cm2for thousands of hours. The effective work function of this cathode can be expressed as &fgr;=2.93+2.15×10−4T between 1750 and 2350 K.