3.1.2.2 Use of filters for excitation

The excitation spectrum can be modified if some absorbing foils are inserted between the x-ray tube and the sample. The photoelectric absorption of the filter material will strongly attenuate low energies and the energies above its absorption jump, thus acting as a band pass filter. By choosing the filters, different intervals of energy can be strongly attenuated in the x-ray tube emission spectrum and the spectral background significantly reduced for some groups of elements in the measured XRF spectrum.

As most of the energies that do not contribute to excitation are removed, the signal to noise ratio in the spectrum is improved, but at the sacrifice of losing the intensity of the excitation beam.