X-rays of a suitable wavelength range for protein crystallography (~0.8 - 2.3 Å) are generated by three commonly used devices: X-ray tubes, rotating anodes and synchrotrons.
In laboratory sources will produce X-rays using either an evacuated tube or a rotating anode. X-ray tubes consist of a filament that acts as a cathode. Electrons are emitted by the glowing cathode and accelerated by several tens of kVs across the vacuum towards the anode, which consists of a metal target made of a characteristic material, usually copper or chromium, for protein crystallography. As the electron beam impacts the anode, the high kinetic energy of the electrons is converted during deceleration into X-rays producing