Black-body approximation to the continuous X-ray spectra

The shape of the continuous X-ray spectrum is approximated by the Planck's distribution law for black-body radiation. The energy distribution of continuum X-rays produced by a bombardment of 30 kV electron beam onto a gold target is reproduced by the black-body radiation at a temperature of 107 K. The continuous spectrum measured when the incident electron energy varies in the range 30, 20, 10, and 5 kV, and for different target elements such as gold, iron, and carbon, are again reproduced in their absolute intensity scale. Consequently, it is speculated that the Stefan-Boltzmann's law as well as the Wien's displacement law also hold for the continuum X-ray radiation.