Cathode structures for X-ray tubes

摘要

An apparatus and method comprising a cathode structure which can be a cylindrical filament coiled in a helix or which can be constructed of a ribbon or other suitable shape. The cathode structure can be heated by passage of an electrical current, or by other means such as bombardment with energetic electrons. Selected portions of the surface of the cathode structure have an altered property with respect to the non-selected portions of the surface. In one embodiment, the altered property is a curvature. In another embodiment, the altered property is a work function. By altering the property of the selected portions of the surface, the electron beam intensity is increased, and the width is decreased.

主权项

1. An apparatus comprising:
a cylindrical cathode filament to function as a cathode of an X-ray tube, the cathode filament comprising a top surface and an oppositely positioned bottom surface, the top surface configured to emit electrons and comprising a non-selected portion and a selected portion, wherein a work function of the selected portion of the top surface of the filament is lower than a work function of the non-selected portion of the top surface, wherein the selected portion comprises a first material, and the non-selected portion comprises a second material, and wherein one of: (1) the first material comprises thoriated ditungsten carbide (W2C/ThO2) and the second material comprises thoriated tungsten (W/ThO2), (2) the first material comprises ceriated ditungsten carbide (W2C/CeO2 or W2C/Ce2O3) and the second material comprises ceriated tungsten (W/CeO2 or W2/Ce2O3), or (3) the first material comprises lanthanaized ditungsten carbide (W2C/LaO or W2C/La2O3) and the second material comprises lanthanized tungsten (W/LaO or W/La2O3).