Characteristics radiation.
When the high moving electron bombarding the target eject electrons from the inner orbits of the nucleus. The ejection of inner she’ll of the the orbit leaving an ionised atom with unfilled inner shell. That time the electrons from the outer orbit fill the vacant of inner shell orbit. This types of transection is called characteristic radiation.
The binding energy of an electron in the K shell of tungsten is 70 keV and the cathode electron have more energy of 70 keV to eject the K shell electron from the inner shell.