In situ Raman monitoring of He2+ irradiation induced damage in a UO2 ceramic

Abstract

International audienc

Raman scattering from phonons and electronic excitations in UO2with different oxygen isotopes

“…However, more bands were experimentally observed in Raman spectrum of UO 2 . Graves first observed a broad band around 576 cm −1 for Kr + implanted UO 2 samples, which was confirmed by other groups . It is a disorder/defect induced band and generally assigned to the normally forbidden first‐order longitudinal optical phonon (1LO), which can become Raman active through a loss of symmetry because of a breakdown in the selection rules.…”

Advanced techniques for characterization of ion beam modified materials

“…As a result of the interaction of the laser light with molecular vibrations, phonons or other excitations, the energy of the laser photons can be shifted up or down, which then contains information about the vibrational modes in the sample. Raman spectroscopy has been increasingly applied for the structural characterization of ion-beam modified materials, such as in carbides [36][37][38] and oxides [39][40][41][42]. More recently, micro-Raman spectroscopy has been used to characterize the damage created over the entire ion range [36,41,42] to provide new information on quantification of the damage and structure modification as a function of depth, and on enlightenment of possible synergistic effects due to both nuclear and electronic energy deposition to the materials [31].…”

“…Such conventional use of Raman spectroscopy does not allow probing depths exceeding several micrometers and especially does not provide quantitative analysis at a fixed damage level. Recent developments have shown that micro-Raman can be employed to quantify the damage in the wake of energetic ions from the surface of a crystal to the depth at which the ions come to rest (tens of micrometers) by analyzing thin cross sections of irradiated bulk samples [36,38,41,42]. Such cross-sectional approach provides several salient outcomes, such as distinctive effects of nuclear and electronic mechanisms resulting from the ion slowing down processes and information regarding the final structure of ion-irradiated materials along the ion path.…”

“…One of the recent developments includes an in situ Raman setup coupled with a cyclotron accelerator developed at CEMHTI laboratory (Orléans, France) that allows direct monitoring of the irradiation-induced changes in solid samples and at solid/fluid interfaces in real time [41,42]. Uranium dioxide (UO 2 ) is currently the standard fuel used in light water reactors, and its response to ion Detailed scattering geometry and data analysis can be found in Ref.…”

“…irradiation is of great interest for the nuclear industry. Utilizing this unique capability, in situ Raman measurements were carried out to probe ion beam irradiation-induced damage and their in-depth profiles on a UO 2 sample under 25 and 45 MeV He 2+ cyclotron beam irradiation (under reducing Ar/H 2 atmosphere) to a fluence of 1.6 Â 10 16 cm À2 [41,42]. The depth profile of 25 MeV implanted He was estimated using the stopping and range of ions in matter (SRIM) code (http://www.srim.org/), as shown in Fig.…”