PURPOSE: To suppress electron emission from a skirt besides the band-shaped electron emission part certainly by installing a heat shield cylinder in the space between the internal circumferential wall of the skirt and a cathode support.
CONSTITUTION: A heat shield cylinder 24 obtained by previously winding a sheet of high melting point metal such as molybdene at a constant pitch, for ex. quadruply, is installed in the space between a cathode support 12 and a skirt 15 located on its outside. In assembling, this heat shield cylinder 24 is inserted from below into the space between the two and held from below by three bobbin-form retainers 25 made of molybdene, and meantime the tip 25a is fitted in a small through hole formed in the skirt, and fixation is made by welding at the welding part 26. The heat shield cylinder 24 prevents the heat from the heater part or cathode support from being radiated directly to the skirt via the space. The band-shaped electron emission part is heated high by a heater, when the skirt is shielded by the cylinder and does not become so hot, and electron emission from the outside circumferential surface is suppressed certainly.
SAKAMOTO KEIJI
OKAZAKI YUKIO
JAPAN ATOMIC ENERGY RES INST