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 a thickness of 0.5 μm to 4.0 μm on {TAIL ~ the surface} of a core metal wire 
is coated on
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 a thickness of 0.5 μm to 4.0 μm on { TAIL ~ 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 OTH OTH OTH OTH OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH