X-ray-induced radiation damage in CsI, cadox, Y2O2S and Y2O3 thin films

The stability of CsI, CsI(TI), Gd2O2 S(Tb), Gd-2 O-2 S(Eu), Y2O2S(Eu) and Y 2O3(Eu) thin films under bombardment by 9-18 keV X-rays is described. Both external photocurrent and scintillation light yield were measured as functi ons of accumulated dose at radiation fluxes of 10(6)-10(7) photons s(-1) mm (-2) on Beamline 2.2 of the Daresbury Synchrotron Radiation Source (SRS). A ll of the samples studied showed changes of several percent (both reduction s and increases) in photocurrent and scintillation light yield of several p ercent for accumulated doses of up to 5 x 10(11) photons mm(-2). No signifi cant dependence of the film response on the angle of X-ray incidence was ob served for angles up to 45 degrees from the normal. It was found that the a ccumulated dose is not the only parameter determining the degradation of ph otoconverter performance: the flux rate has also to be taken into account. Scanning Electron Microscope studies of the irradiated samples did not reve al ally significant surface modification. (C) 2001 Elsevier Science B.V. Al l rights reserved.