An x-ray tube has a backscatter electron trap to prevent extra focal radiation caused by backscattered electrons from the focal spot from passing through the beam exit window to an exterior of the x-ray tube. The backscatter electron trap has a surface that faces the x-ray beam in the x-ray tube. No portion of that surface is visible both from an arbitrary point in the x-ray beam outside of the x-ray tube and from an arbitrary point at the focal spot.