{HEAD ~ A directly heated oxide cathode} 1, wherein said core metal wire comprises {TAIL ~ a tungsten core wire} or a rhenium tungsten core wire 
{ HEAD ~ A directly heated oxide cathode } 1 , wherein said core metal wire comprises { TAIL ~ a tungsten core wire } or a rhenium tungsten core wire
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH