In a filament cathode, {HEAD ~ an alkaline earth oxide} having an average grain size of 0.1 μm to 2.0 μm is coated in {TAIL ~ a thickness} of 0.5 μm to 4.0 μm on the surface of a core metal wire 
is coated in
In a filament cathode , { HEAD ~ an alkaline earth oxide } having an average grain size of 0.1 μm to 2.0 μm is coated in { TAIL ~ a thickness } of 0.5 μm to 4.0 μm on the surface of a core metal wire
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH