Interruption-ring in an X-ray tube

An x-ray tube comprising:

• a cathode and an anode electrically insulated from one another, the cathode configured to emit electrons towards the anode, and the anode configured to emit x-rays out of the x-ray tube in response to impinging electrons from the cathode;
• an enclosure attached to the cathode and the anode, the enclosure electrically-insulating the cathode from the anode;
• a coating-ring on an inner-face of the enclosure, the coating-ring adjoining the cathode, the coating-ring encircling a longitudinal-axis of the enclosure, the longitudinal-axis extending between the cathode and the anode;
• an interruption-ring located at the inner-face of the enclosure, the interruption-ring encircling the longitudinal-axis, the interruption-ring being distinct from the coating-ring;
• an electric-current-path through the coating-ring and the interruption-ring in series;
• RI>RC, where RI is electrical resistance per unit length through the interruption-ring and RC is electrical resistance per unit length through the coating-ring, both measured parallel to the longitudinal-axis;
• ρC<ρE, where ρC is a bulk electrical resistivity of the coating-ring and ρE is a bulk electrical resistivity of the enclosure;
• the interruption-ring is on an inner-face of an electrically insulative disc, and the disc encircles at least part of the cathode or at least part of the anode;
• and
• the interruption-ring encircles the longitudinal-axis at a different radius from the longitudinal-axis than the coating-ring.