An x-ray tube 10 can have (a) an enclosure electrically-insulating a cathode 11 from an anode 12; (b) a coating-ring 18 on an inner-face of the enclosure, the coating-ring 18 encircling a longitudinal-axis 16 of the enclosure; and (c) an interruption-ring 19 located at the inner-face of the enclosure at a different location than the coating-ring 18. The interruption-ring 19 can encircle the longitudinal-axis 16 at a different location along the longitudinal-axis 16 with respect to the coating-ring 18. The interruption-ring 19 can encircle the longitudinal-axis 16 at a different radius from the longitudinal-axis 16 than the coating-ring 18. The coating-ring 18 and the interruption-ring 19 can reduce uneven electrical charge build-up on the inner-face of the enclosure, and can protect the triple-point.