Patent ID: 7664230
Filing Date: 2010-02-16
Classification: H01J

Abstract:
1. A transmission target X-ray tube comprising: a cathode arranged to provide a source of electrons; an anode held at a positive potential with respect to the cathode to accelerate electrons from the cathode such that they will impact on the anode thereby to produce X-rays, wherein the anode is a thin film anode; and a retardation electrode held at a negative potential with respect to the anode to produce an electric field between the anode and the retardation electrode which slows down electrons which have passed through the anode thereby reducing the amount of heat they generate in the tube, wherein the retardation electrode is located on the opposite side of the anode to the cathode, wherein the retardation electrode forms part of an electrical circuit and its potential is substantially constant and wherein the retardation electrode is electrically connected to the anode via a resistor, wherein current flowing through the resistor determines the potential of the retardation electrode with respect to the anode.