Patent ID: 8340250
Filing Date: 2012-12-25
Classification: A61B,H01J

Abstract:
1. An X-ray tube comprising: at least one thermionic cathode having a plurality of coil windings that are configured to generate an electron beam, the plurality of coil windings having gaps between successive coil windings; a target assembly configured to generate X-rays when impinged with the electron beam emitted from the thermionic cathode; a high voltage supply unit for establishing an output voltage across the thermionic cathode and the target assembly for applying an accelerating electric field between the thermionic cathode and the target assembly; and a mesh grid having a plurality of grid members that correspond to the plurality of coil windings of the at least one thermionic cathode, the mesh grid disposed between the thermionic cathode and the target assembly, the mesh grid configured to operate at a voltage so as to decrease the accelerating electric field applied between the thermionic cathode and the target assembly, wherein the grid members of the mesh grid are aligned with the gaps between the successive coil windings; wherein the voltage of the entire mesh grid is negative biased with respect to the voltage at the thermionic cathode such that all grid members of the plurality of grid members simultaneously have a voltage applied thereto that is less than the voltage at the thermionic cathode during emission of the electron beam from the thermionic cathode to the target assembly.