Explain characteristic peak in xray production at the anode. I know what it is, but dont know why it happens.

Question

From what I understand, the energy of xrays increase at a certain value specific to the anode material. I can not find any information on characteristic peak, all my searches lead me to kilovolt peak.

Answer 1

The part of the x-ray spectrum you're talking about is called a discreet part (lines spectrum) and it depends only on material of the anode (while kilovolt peak in continuous spectrum depends on the kinetic energy of the electrons that hit the anode - this energy depends only on the voltage across the x-ray tube and not the material).
Electrons that hit the anode collide with the atoms of the metal that is used for the anode (usually tungsten). The electrons have different kinetic energies. Those which have enough energy may knock out the electrons that are bound inside the atoms in the inner energy shells (K, L and so on) that are closed to the nucleus. Immediately after this occurs, the electrons from higher energy shells would fill the vacancy in the shell - as a result, the photon is emitted. This so called x-ray photon has the energy that equals the energy difference of those two energy levels, involved in the event. This energy difference is different for different atoms. In the spectrum, there are several pronounced intensity peaks at certain wavelength. These peaks occur at various specific wavelengths for each target material. The lines are called K-alpha, K-beta etc. and L-alpha, L-beta... depending on which shell did the electron knocked the other electron from. For instance, K-alpha for tungsten has the wavelength 0,071 nanometres, while the same line for the copper appears at 0,15 nanometres.