An x-ray tube assembly is provided comprising a tube casing assembly
including a plurality of vertical mount posts. An insulator plate is
mounted to the plurality of vertical mount posts such that the insulator
plate can translate vertically on the posts. A cathode assembly is
mounted to the insulator plate and generates both an eccentric moment and
a vertical expansion in response to a cathode power load. A
semi-compressible element is positioned between at least one of the
vertical mount posts and the insulator plate. The semi-compressible
element becomes incompressible at a cathode power threshold such that the
vertical expansion is translated into a correction moment countering the
eccentric moment.