As an x-ray tube expands and contracts during heating and cooling, its hermetic seal can be damaged. A more robust hermetic seal, particularly as the x-ray tube is heated and cooled, is desirable. The x-ray tube described herein can include a proximal-housing 13 and a distal-housing 14, which can be connected to each other by an interface-ring 15 for improved hermetic seal. Added x-ray tube weight, of material used for blocking x-rays, can make it difficult to transport the x-ray tube. Reducing this weight is desirable. A maximum outer diameter Dp of the proximal-housing 13 can be greater than a maximum outer diameter Dd of the distal-housing 14, for improved blocking of x-rays. This diameter difference can allow improved x-ray shielding with less material.