Patent ID: 8110974

Claim:
An electron beam generating apparatus comprising: an electron gun that has an electron emitting member from which an electron beam is emitted; a container that holds the electron emitting member; a frame material detachably attached to the container, the frame material having an electron passing hole through which the electron beam passes; a window material that is bonded to the frame material so as to airtightly stop the electron passing hole and through which the electron beam penetrates; a sealing member with which a gap between the frame material and the container is airtightly sealed; and a groove formed on a side of the container, the groove holding the sealing member, wherein the frame material has a threaded hole disposed away from the scaling member when viewed from the electron passing hole, wherein the container does not have a threaded hole corresponding to the threaded hole of the frame material so that when a screw is screwed into the threaded hole, the screw provides a force to pull the frame material and the container apart from each other that is applied to the frame material, wherein the container has a stepped part by which the frame material is positioned, and wherein a wall of the stepped part and a sidewall of the frame material are spaced apart from each other.