[alancalverd]

Just bashing the electron into a target is technically simple up to about 15 MeV but not very efficient: you produce a broad spectrum of x-rays, most of which you don't want, and a lot of heat, none of which is useful.

At higher energies you use various forms of magnetic wiggler or undulator. Remember a photon is emitted when an electron accelerates, so if you keep the speed constant but bend the track, you will generate photons tangential to the bend. A good wiggler or undulator will give you a very intense beam of near-monochromatic x-rays.