In a filament cathode, 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 {HEAD ~ 4.0 μm} on {TAIL ~ the surface} of a core metal wire 
In a filament cathode , 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 { HEAD ~ 4.0 μm } on { TAIL ~ the surface } of a core metal wire
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH