FIG 4 is a cross sectional view of {HEAD ~ an electron gun unit} of {TAIL ~ the third embodiment} 
FIG 4 is a cross sectional view of { HEAD ~ an electron gun unit } of { TAIL ~ the third embodiment }
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL