G. Guimbretière

Determination of in-depth damaged profile by Raman line scan in a pre-cut He2+ irradiated UO2

Raman measurements were carried out to probe the spectroscopic signatures of the ion beam irradiation-induced damage and their in-depth profiles on a Uranium dioxide sample previously cut and polished prior to performing a 25 MeV He2+ cyclotron beam irradiation. Raman spectra clearly show the creation of three defects bands (U1 ≈ 530, U2 ≈ 575, and U3 ≈ 635 cm−1) resulting from the ion irradiation and also some changes in the T2g peak of UO2. Their in-depth distribution inside the sample exhibits a clear increase of the damage from the surface up to the position of the implanted He.

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

The in situ Raman probing of a UO2 ceramic in [Ar/H2, 95/5] gas atmosphere followed by exposure to He2+ ionic irradiation coming from a cyclotron accelerator was implemented. It was observed that the growth of Raman defect bands exhibits a unique kinetic nicely modelized by a simple direct impact model, and with an annealing rate constant of 5.6 × 10−4 ± 4 × 10−5 s−1 for an ionic flow of 50 nA and an ions-beam induced sample heating of 170 ± 10 °C. Also, it was observed that the Ar plasma induced by the ions-beam is a sensitive probe of the presence of the ions-beam.

In-Situ Raman Observation of the First Step of Uranium Dioxide Weathering Exposed to Water Radiolysis

ABSTRACT The effect of irradiation is a key point in the knowledge of the behavior of some compounds such as uranium-based ones. Regarding this topic, the authors developed an original in-situ Raman spectroscopy device coupled to a cyclotron ion beam. This original instrument allows observing the kinetics of uranium dioxide weathering by α radiolysis of water. The authors then observed that an altered layer made of Studtite and Schoepite phases grows linearly during the irradiation and extends for several hours after irradiation. Kinetics of production of some molecular species during radiolysis were also reported.

Correlation between second-order optical response and structure in thermally poled sodium niobium-germanate glass

We have carried out Raman and second harmonic generation (SHG) measurements to probe thermal poling-induced phenomena in glass 20Na2O-80[0.35Nb2O5-0.65GeO2]. A SHG response of 0.6 pm/V was measured after poling in a ∼3 μm thick layer under the anode and found to deviate from the widely used electric field-induced SHG model. This effect was associated with complex structural rearrangements in the subanode layer involving destruction of nonbridging oxygen atoms, formation of molecular oxygen, and enhancement of cross-linking in the glass network.

Structural Relaxation Dynamics and Annealing Effects of Sodium Silicate Glass

Here we report high-precision measurements of structural relaxation dynamics in the glass transition range at the intermediate and short length scale for a strong sodium silicate glass during long annealing times. We evidence for the first time the heterogeneous dynamics at the intermediate range order by probing the acoustic longitudinal frequency in the GHz region by Brillouin light scattering spectroscopy. Or, from in-situ Raman measurements, we show that relaxation is indeed homogeneous at the interatomic length scale. Our results show that the dynamics at the intermediate range order contains two distinct relaxation time scales, a fast and a slow component, differing by about a 10-fold factor below Tg and approaching to one another past the glass transition. The slow relaxation time agrees with the shear relaxation time, proving that Si-O bond breaking constitutes the primary control of structural relaxation at the intermediate range order.

In situ Raman spectroscopy for growth monitoring of vertically aligned multiwall carbon nanotubes in plasma reactor

Portable and highly sensitive Raman setup was associated with a plasma-enhanced chemical vapor deposition reactor enabling in situ growth monitoring of multi-wall carbon nanotubes despite the combination of huge working distance, high growth speed and process temperature and reactive plasma condition. Near Edge X-ray absorption fine structure spectroscopy was used for ex situ sample analysis as a complementary method to in situ Raman spectroscopy. The results confirmed the fact that the “alternating” method developed here can accurately be used for in situ Raman monitoring under reactive plasma condition. The original analytic tool can be of great importance to monitor the characteristics of these nanostructured materials and readily define the ultimate conditions for targeted results.