Continuum X-rays produced by a few MeV proton bombardment

Production cross sections of continuum X-rays for quasi-free electron bremsstrahlung (QFEB), radiative ionization (RI), secondary electron bremsstrahlung (SEB), radiative elastic scattering (RES), and nuclear bremsstrahlung (NB) have been estimated for carbon and aluminum targets bombarded with 1, 3, and 6 MeV protons. Contributions of these processes to the sensitivity of PIXE are discussed. It is shown that, in the case of PIXE using 1-3 MeV protons, RES strongly influences the detection limit for those elements for which the K X-ray energy is larger than the energy T_m, which is the maximum energy transferred from the projectile to a free and rest electron.