Thermal field electron emission from Ir-La alloy and LaB/sub 6/

This paper presents results of further investigation of Ir-La metal alloy cathode under conditions of transition from thermionic emission to thermal field electron emission. The cathodes of a cone shape with taper angle about 60/spl deg/ were made by spark discharge machining of Ir-La and LaB/sub 6/ ingots. To suppress the emission the whole surface of the cathode was covered with layers of hafnium and carbon. Subsequent heating resulted in appearance of hafnium carbide layer about 6 /spl mu/m thick. Then the tip of the cone was ground so as to have the diameter of the open emitter surface to be about 100 /spl mu/m.