Image Number 2 for United States Patent #4673842.
A cathode cup structure for a high voltage x-ray tube having a base formed of a weldable material and an exposed upper surface of a non-weldable material bonded to the base. The upper surface may be machined from a block of graphite to form an appropriate cathode cup structure configuration and then bonded to a base formed of TZM using a platinum brazing compound. The graphite upper surface may be coated with pyroltic carbon to reduce dust or alternatively, may be formed of a composition of silicon carbide graphite to minimize dusting problems. The graphite composition of the upper section of the cathode cup minimizes the risk of welding of an electron emissive filament passing through the cup structure.