What is the radiation source for x-ray waves?

X-rays are produced by the electric field of an atom. This is usually discussed in terms of characteristic X-radiation and bremsstrahlung. Most X-rays in hospital X-ray kit are the latter (the exception is mammography) . Electrons are fired from an electron gun at a tungsten target. When the electrons pass close to a tungsten atom they interact with electric field. This deflects the incoming electrons, slowing them down, reducing their energy. The excess energy is given of as X-rays.