Patent ID: 8011988

Claim:
A method for assembling an indirectly-heated cathode assembly including: a tubular cathode holder which, assuming that a side from which thermal electrons are emitted is a front side, supports a cathode that emits thermal electrons, at the front side; a cathode conductor which supports said cathode holder; a filament which heats said cathode; and two filament conductors which support said filament, and which are juxtaposed with each other, the method comprising steps of: disposing a groove and a projection in an outer circumference of said cathode holder, said projection projecting from a rear end of said groove in a direction which perpendicularly intersects an axis of said cathode holder, disposing an opening fitting a portion of said groove in said cathode conductor, a peripheral portion of said opening being engaged with said projection, determining, in said groove, a width (W) between said projection and a front end face of said groove and a thickness (T) of said cathode conductor in the periphery of said opening so that a dimension (W−T) which is obtained by subtracting the thickness (T) from the width (W) is substantially equal to a predetermined gap length (G) which is between said filament and said cathode, and which extends in a direction along the axis of said cathode holder, fitting the portion of said groove into said opening of said cathode conductor to attach said cathode holder to said cathode conductor, rearward pushing said cathode holder to cause the front end face of said groove to butt against said cathode conductor, coupling and fixing said cathode conductor and at least one of said two filament conductors to each other via an electrically insulating material, forward moving said filament to butt against said cathode, fixing said filament to said two filament conductors, forward pulling said cathode holder to cause said projection to butt against said cathode conductor, and fixing said cathode holder to said cathode conductor.