A simple method of producing a focused x-ray beam

One challenge in X-ray optics is how to focus hard X-rays. The possibility of achieving a wide-range of spot sizes would be an advantage for many applications, such as semiconductor lithography, nuclear fusion diagnostics or focused X-ray beams for cancer therapy. Focused X-rays could deliver precise high doses to tumours while sparing the surrounding tissue. Currently, a promising approach is using a Laue lens. However, they are limited by the diffraction capability of crystals and the complex mm-size arrangement of the optical elements. In addition, they are restricted to sub-MeV photon beams, because for higher energies the Bragg condition is not satisfied. We present an efficient and cost-effective method to extend this range up to tens of MeV using an electron-photon converter in the stream of focused high energy electrons. The emerging X-rays follow the trajectories of the electrons and the focus can be simply adjusted by modifying the focus of the electron beam. A bending magnet can be used to remove electrons, if necessary, however a mixed radiation could be an additional option. Our solution can also be adapted to a multiple beam arrangement as an effective alternative to Gamma Knife without the need for handling radioactive sources.