What is characteristic radiation produced from at the tungsten target?

Characteristic radiation is specifically produced when high-speed electrons collide with the tungsten target in an X-ray tube. When an incoming high-speed electron strikes a tungsten atom, it can have enough energy to eject an inner-shell electron, typically from the K-shell. This vacancy leads to an excited state in the atom.

As a result, electrons from higher energy levels (or shells) will transition down to fill the vacancy left by the ejected inner-shell electron. When these electrons drop to a lower energy state, they release energy in the form of X-ray photons. These emitted photons have specific energies corresponding to the differences between the energy levels of the tungsten atom, which is why the radiation produced is referred to as "characteristic." It is characteristic of the material (tungsten) because it has a specific energy unique to those electron transitions.

This process underlines the importance of understanding the interactions of high-speed electrons with target materials in generating X-rays. The fact that the characteristic radiation is a direct result of an inner-shell electron being ejected is fundamental to the physics of X-ray production.