An x-ray tube includes a cathode positioned within a vacuum chamber and configured to emit electrons. The x-ray tube includes an anode positioned within the vacuum chamber to receive electrons emitted from the cathode and configured to generate a beam of x-rays from the electrons, a window positioned to pass the beam of x-rays therethrough, and an electron collector structure attached to the x-ray tube having an aperture formed therethrough to allow passage of x-rays therethrough. The aperture is shaped to prevent diffracted x-rays from combining with the beam of x-rays passing through the window.