10:40-11:20
Optical diagnostics of collective and non-linear effects in insulators during intense irradiation
Prof. Oleg A. Plaksin (SSC RF - A. I. Leypunsky Institute of Physics and Power Engineering, Obninsk, Russia Obninsk State University for Nuclear Power Engineering, Obninsk, Russia)
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We used the optical diagnostics during irradiation to study (a) the effects of electric fields and ultrasonic vibrations on the radiation-induced luminescence of insulators (Al2O3, SiO2, BN) under proton irradiation (dose rate < 104 Gy/s), (b) the non-linear optical phenomena in silica-core fiber waveguides induced by pulsed-fission-reactor irradiation (<105 Gy/s) and (c) the formation of metal-nanocluster composites during heavy-ion implantation (<108 Gy/s) of insulators (Al2O3, SiO2). We review and discuss the following results:
(a) Correlations between radiation-induced optical, electrical and mechanical properties of insulators under proton irradiation were found. It has been shown that radiation-induced optical phenomena are caused by the electrical charge evolution on microscopic or nanoscopic scales and the interaction between radiation-induced charge carriers on traps, but not only by electronic excitation of optical centers.
(b) Transient optical loss and radiation-induced photon emission (time dependences and spectra) of silica-core fibers were measured. The optical properties depended on light intensity in the fibers, even at low light intensities. The dose rates caused by absorption of the light (10-2 Gy/s) were much lower than the dose rate of ionizing radiation. No non-linear effects were observed outside radiation fields.
Spectra of optical absorption and ion-induced photon emission were measured during implantation of noble metal ions into insulators. The optical diagnostics helped us in finding the ranges of dynamic equilibrium between phases under irradiation and allows us to draw the non-equilibrium phase diagrams. Measurements of the optical absorption were necessary to monitor metal nanoparticles (metal phase) formed. Ion-induced photon emission helps in monitoring the solid solutions of implanted ions. An important feature of the dynamic balance of phases under irradiation was found: dynamically stable structures. After irradiation to fluences corresponding to formation dynamically stable structures, surface structures and bimodal (size, depth) distributions of metal nanoparticles in the bulk were observed. The properties and mechanisms of formation of these structures deserve much attention in the radiation materials science, in particular in the problem of radiation-resistant materials.