The invention proposes an insulator within an X-ray tube having a vacuum side and an ambient side and a feedthrough substantially coinciding with an axis of symmetry at the vacuum side and an axis of symmetry at the ambient side. The axis of symmetry at the vacuum side and the axis of symmetry at the ambient side have an angle of at least 5°, preferably 90°, with respect to each other. An X-ray source comprising such an insulator is presented as well and the present invention also extends to a medical imaging apparatus for generating X-ray images of a patient thereby using an X-ray source with such an insulator. In an embodiment, an X-ray source is provided wherein the insulator is plugged to an electrical connector at the ambient surface.