Saturation of a Ce:Y_3Al_5O_12 scintillator response to ultra-short pulses of extreme ultraviolet soft X-ray and X-ray laser radiation

Abstract

Investigations of radioluminescence saturation in monocrystalline cerium doped yttrium aluminum garnet (Ce:YAG) exposed to intense extreme ultraviolet (XUV), soft X-ray and X-ray radiation delivered from three free-electron lasers are described in this article. The measurements were performed with wavelengths of 98, 25.6, 13.5 and 0.15 nm. We have found that saturation of the photon yield occurs at an excitation level of 2.0 x 1020 eV/cm3 resulting in an emission of 1.5 x 1018 visible photons per cubic centimeter. This number is much smaller than the concentration of Ce3+ in the scintillator that was equal to 2 x 1020 cm−3. Because the internal radiance efficiency η does not depend strongly on the irradiating photon energy, i.e., η ≈0.035 ± 0.015 in the range 10 to 100 000 eV, the results presented here could be used to predict saturation effects in scintillator slabs placed in imaging systems of bright XUV, X-ray and particle beams. The saturation of the Ce3+ emission is explained by mutual quenching of excitons created at high densities, preceding the stage of energy transfer to the Ce3+ ions.