An x-ray source is described. During operation of the x-ray source, an electron source emits a beam of electrons. This beam of electrons is focused to a spot on a target by a magnetic focusing lens. In particular, the magnetic focusing lens includes an immersion lens in which a peak in a magnitude of an associated magnetic field occurs proximate to a plane of the target. Moreover, in response to receiving the beam of focused electrons, the target provides a transmission source of x-rays.