This specification describes an anode for an X-ray tube with multiple channels, where each channel defines an electron aperture through which electrons from a source pass to strike a target and a collimating aperture through which X-rays produced at the target pass out of the anode as a collimated beam. At least a portion of the walls of each channel are lined with an electron absorbing material for absorbing any electrons straying from a predefined trajectory. The electron absorbing material has a low atomic number, high melting point and is stable in vacuum. Graphite may be used as the electron absorbing material.