X-ray generator is composed of X-ray tube, high voltage generator, tube pressure and tube flow stabilization circuit and protection circuit. Here we focus on X-ray tubes. The essence of the X-ray tube is a vacuum diode, the cathode is a tungsten wire, the anode is a metal sheet. When a current is applied to both ends of the cathode, the tungsten wire heats up, producing heat-radiating electrons. These electrons are accelerated under a high voltage electric field, bombarding the anode (aka the target) and producing X-rays (this process generates a lot of heat, and in order to protect the target, it is necessary to ensure that the circulating water system is working properly).

Common anode targets are: Cr, Fe, Co, Ni, Cu, Mo, Ag, W, the most commonly used is Cu target. The X-ray wavelength and operating voltage of commonly used targets are shown in the table below: