The X-ray Tube Spectrum

The distribution of probability of emission by energies (spectrum of the X-ray tube) is ruled by the two effects originating x-ray emission:

• A continuum distribution, characterized by a minimum and a maximum energy which corresponds to the emission of breaking radiation (Bremstrahlung). When operated at voltage U₀ the electrons get a maximal energy E₀= e U₀ ,  but photons originated by breaking process can be emitted with energies from E₀ down to zero.
  
  
• The characteristic radiation emitted as a result of the ionization of the anode material.