Reduced focal spot motion in a CT X-ray tube

An x-ray tube assembly comprising:

• a tube casing assembly including a plurality of vertical mount posts, said tube casing assembly including a casing back plate, a first casing wall, and a second casing wall;
• a tube insert mounted within said tube casing assembly, said tube insert comprising an anode back plate mounted to said casing back plate, a first insert wall mounted to said anode back plate, and a second insert wall mounted to said anode back plate;
• a target element mounted to said anode back plate;
• an insulator plate mounted to said plurality of vertical mount posts such that said insulator plate can translate vertically on said vertical mount posts;
• a cathode assembly mounted to said insulator plate, said cathode assembly further mounted to said first insert wall and said second insert wall by way of a plurality of flex mounts positioned between said cathode assembly and said first insert wall and said second insert wall, said cathode assembly generating an eccentric moment in response to a cathode power load and;
• a semi-compressible element positioned between at least one of said vertical mount posts and said insulator plate, said semi-compressible element becoming incompressible at a cathode power threshold such that said semi-compressible element generates a correction moment countering said eccentric moment.

A method of countering the eccentric moment generated by a cathode assembly within an x-ray tube assembly comprising:

• mounting the cathode assembly to an insulator plate vertically translatable on a plurality of vertical mount posts;
• mounting a semi-compressible element between one of said vertical mount posts and said insulator plate, said semi-compressible element becoming incompressible at a cathode power threshold;
• raising the cathode assembly to said cathode power threshold;
• translating vertical expansion of the cathode assembly into a correction moment using said semi-compressible element and;
• using said correction moment to counteract the eccentric moment to minimize focal spot drift.