The principle of X-ray source producing X-rays

In X-ray sources, X-rays are mainly generated by electron bombardment of target materials, and there are two specific principles:

1) When a high-speed electron collides with a target atom, it changes its original trajectory and slows down, while emitting X-rays with an energy equal to the energy difference before and after the high-speed electron collision.

Due to the different relative positions of each high-speed electron interacting with the target atom, the radiation losses corresponding to each interaction are also different, resulting in different energies of X-ray photons emitted. A large number of X-ray photons form a frequency continuous X-ray emission spectrum, much like a mixture of monochromatic light of various colors to form white light. So, the X-rays generated by this principle are called white X-rays (also known as continuous spectra).

2) High speed electrons collide the inner orbital electrons of the target atom, causing them to leave the atom and become free electrons. This creates a temporary electron vacancy in the inner orbital, which is immediately filled by the outer electrons. When orbital electrons transition from the outer layer to the inner layer, they emit X-rays, and their energy is equal to the difference between the energy levels of these two orbitals.

Due to the fixed energy levels of each orbital electron of the target atom, the generated X-ray energy is also fixed and only depends on the characteristics of the target atom itself; So, the X-rays generated through this principle are also known as identification X-rays (also known as identification spectra).

Any target material will produce both white X-rays and labeled X-rays simultaneously. In X-ray detection applications, the sample itself has various materials, so tungsten targets that produce more white X-rays are generally chosen. In X-ray fluorescence analysis applications used to analyze the composition of substances, molybdenum targets that are more prone to producing labeled X-rays are often chosen.