Measurement of non-linearity in the cathodoluminescence yield for non-doped scintillators

Abstract

We propose a method for studying nonlinearity in the cathodoluminescence (CL) characteristics of wide-bandgap materials based on the measurements of the CL energy dependence on the total energy of a pulsed electron beam Eb using its bremsstrahlung. It is shown that the x-ray radiant energy produced by a high-power (∼10MW/cm2) electron beam with particle energies of 50–300 keV is proportional to Eb in the case of weak variations in the electron energy distribution of the beam. This direct proportionality between Eb and the x-ray radiant energy is experimentally confirmed in the current experiment by measuring the dependence of the molecular nitrogen emission radiant energy at 337 nm excited by a direct electron impact (the 0-0 vibrational transition of the second positive system of the emission bands of N2 molecule) on the total electron beam energy Eb. Using this result, the dependencies of the CL radiant energy on Eb are studied for undoped Bi4Ge3O12, PbWO4, CeF3, and BaF2 crystals with bright intrinsic luminescence. An interpretation of these dependencies is given using a simple theoretical model and photoluminescence nonlinearity data published in the literature. We estimate the average concentration of the electronic excitations (EE) provided by the electron beam (1018–1019 e.–h.p./cm3) and obtain the approximate dependencies of the CL yield on the EE density for the studied materials. For the CeF3 crystal, different CL yield dependencies on the EE density are found for the bands at 300 and 350 nm.