Patent ID: 11923166
Assignee: MEIDENSHA CORPORATION
Field: Electrical machinery, apparatus, energy (Electrical engineering)
Classification: CPC H | IPC H

Claim 4:
5. A field emission device comprising:
a vacuum vessel in which both ends of a cylindrical insulating body are sealed so as to form a vacuum chamber on an inner peripheral side of the insulating body;
an emitter positioned on one side of a direction toward the both ends in the vacuum chamber, and supported via a bellows which is expandable in the direction toward the both ends, so as to be movable in the direction toward the both ends; and
a target positioned on an other side of the direction toward the both ends in the vacuum chamber, and provided so as to face the other side of the direction toward the both ends in the emitter,
wherein the emitter is provided with an electron generation part on a side facing the target, and a guard electrode is provided on an outer peripheral side of the electron generation part of the emitter,
wherein the guard electrode having a cylindrical shape and provided on the outer peripheral side of the electron generation part of the emitter comprises a distal end section positioned in an emission direction of an electron beam from the electron generation part, wherein the distal end section includes:
a distal end inner-peripheral-side part having an inner-peripheral-side curved surface portion convex to the emission direction,
a distal end outer-peripheral-side part having an outer-peripheral-side curved surface portion convex to the emission direction, and
a distal end middle part positioned between the distal end inner-peripheral-side part and the distal end outer-peripheral-side part, and having a flat surface portion between the inner-peripheral-side curved surface portion and the outer-peripheral-side curved surface portion, the flat surface portion extending in a direction therebetween;

wherein a grid electrode is provided between the emitter and the target in the vacuum chamber, and
wherein the flat surface portion of the guard electrode extends in a direction crossing an axis of the guard electrode at an inclined angle, such that a point on the flat surface portion moves toward the other side of the direction toward the both ends as it approaches a distal end outer-peripheral-side part side from a distal end inner-peripheral-side part side.