4. Continuous background noise

The sensitivity of the PIXE technique can be limited by a continuous background appearing on the X-ray spectra. This mainly comes from the following three components (figure 10 ):

• braking radiation (Bremsstrahlung) from secondary electrons ejected from the target during irradiation. This electromagnetic radiation appears whenever a particle undergoes acceleration. This background component is limited to the low-energy part of the spectrum. The upper energy limit, E _max , corresponds to the maximum energy that an incident proton can transmit to a free electron during a direct collision :...