RESISTANCE OF LEAD TUNGSTATE AND CERIUM FLUORIDE TO LOW RATE GAMMA IRRADIATION OR FAST NEUTRONS EXPOSURE
We present here the results of recent low dose rate gamma irradiation of lead tungstate and cerium fluoride long crystals, and, for lead tungstate only, fast neutron exposure. For the low rate tests, recovery processes are taking place during irradiation and, compared to the usual high rate tests, only a very low damage is noticed, if any. No saturation effect is observed in these previously irradiated samples. For the neutron tests, a very small variation with fluence is not excluded, after a fast saturation at low fluence. The samples tested here are very resistant.
Measurements of lead tungstate crystals behaviour under irradiation for the CMS electromagnetic calorimeter at the LHC
Lead tungstate crystals will be used as calorimetric medium in high energy physics at CERN, in a particularly hostile radiation environment. Methods of testing their behaviour under irradiation are discussed here and are illustrated by some R&D results.
Photoreflectance characterization of vanadium-doped GaAs layers grown by metalorganic vapor phase epitaxy
Abstract We characterized the vanadium-doped (GaAs:V) layers grown on GaAs substrate by metalorganic vapor phase epitaxy. The conductivity of the samples is checked by the Hall effect measurements, and it is n type with electrons concentration ranging from 2×10 13 to 2×10 17  cm −3 . We used the photoreflectance technique (PR) to study the effect of vanadium doping on the optical properties of GaAs. Our experimental results show that the built-in electric field F and the broadening parameter Γ 0 increase with V-doping concentration. Furthermore, the temperature dependence of the built-in electric field and the broadening parameter of GaAs:V samples have been investigated by PR. It has been observed that these parameters increase with increasing temperature. The decrease of the built-in electric field with decreasing temperature is due to the photovoltage effect.We characterized the vanadium-doped GaAs (GaAs:V) layers grown on GaAs substrate by metalorganic vapor phase epitaxy.