An x-ray generator may include a plurality of electron field emitters; a target material; a plurality of energisable solenoid coils; and an electronic power and timing circuit. The generator may provide electrical current to at least one individual solenoid coil to create a magnetic field to cause the path of electrons emitted from the emitter closest to the energised solenoid coil to be defocused and/or deflected before the electrons reach the target material. The target material may comprise a low atomic number material and a high atomic number material, the high atomic number material being arranged in a regular pattern, such that, in use, the electrons may be aimed at either the high or the low atomic number material.