Search results for "nuclear energy"
showing 10 items of 614 documents
Current Transport Mechanism for Heavy-Ion Degraded SiC MOSFETs
2019
IEEE Transactions on Nuclear Science, 66 (7)
Comparison Between Point Defect Generation by $\gamma$-rays in Bulk and Fibre Samples of High Purity Amorphous ${\hbox {SiO}}_{2}$
2008
We compare the E', H(I) and Si-ODC(II) contents in a low-OH high-purity a-SiO2 either in bulk or fibre forms. We found that the H(I) centre appears during irradiation and tend to increase with the dose if the fibre contains hydrogen excess. This behaviour is believed to be one the possible reason to explain the apparent radiation-sensitivity enhancement in the blue-UV spectrum when the fibre is hydrogenated and irradiated at high dose. However for the hydrogen-treated fibres, no experimental repeatability could be evidenced in the measurements of E' and Si-ODC(II) although an acceptable agreement was still found in normal samples. This suggests a possible complex reactional mechanisms in pr…
Luminescence Properties of ZnO Nanocrystals and Ceramics
2008
The luminescence excitation spectra, luminescence spectra and the nanosecond-scale decay kinetics were studied. The ZnO and ZnO:Al nanopowders were prepared by vaporization-condensation in a solar furnace using different raw powders: commercial, hydrothermal and those obtained by plasma synthesis. Exciton-phonon as well as exciton-exciton interaction processes in nanopowders, a bulk crystal and ZnO ceramics were studied and compared. The fast decay and low afterglow intensity of ZnO nanopowders and ceramics support these materials for scintillators.
Investigation of precipitate in an austenitic ODS steel containing a carbon-rich process control agent
2018
This work has been carried out within the framework of the German Helmholtz Association and has received funding from the topic “Materials Research for the Future Energy Supply”. The work of M. Parish and Rainer Ziegler is gratefully acknowledged. Thanks are also due to the team of the chemical laboratory at the KIT for performing the chemical analysis. The help of the beamline staff at ELETTRA (project 20140052 ) synchrotron radiation facility is acknowledged. We acknowledge support by Deutsche Forschungsgemeinschaft and Open Access Publishing Fund of Karlsruhe Institute of Technology.
In situ XRD analysis of the oxide layers formed by oxidation at 743 K on Zircaloy 4 and Zr–1NbO
2000
Abstract Two alloys, having different oxidation behaviour (Zy4 and Zr–1NbO), have been investigated during oxidation at high temperature (743 K) and low oxygen pressure (10 kPa) by in situ X-ray diffraction (XRD). Tetragonal phase content and ‘pseudo-stresses’ on the monoclinic phase have been measured as a function of the oxide layer thickness. The tetragonal phase contents are similar for both alloys and decreased with the oxide layer thickness. Pseudo-stresses were much more compressive on Zr–1NbO alloy, with limited changes at the corrosion kinetics transition. On cooling, the tetragonal fractions do not change, while ‘pseudo-stresses’ decreased in different ways for the two alloys. Wit…
Micro-Raman analysis of the fuel-cladding interface in a high burnup PWR fuel rod
2017
International audience; New insights on the fuel-cladding bonding layer in high burnup nuclear fuel were obtained using micro-Raman spectroscopy. A specimen was specifically prepared from a fuel rod which had been irradiated to an average burnup of 56 GWd.tU-1 in a pressurized water reactor (PWR). Both inner and outer corrosion scale regions were investigated. A 10-15 et956;m thick zirconia bonding layer between fuel and cladding materials which consisted of three distinct regions was observed. Close to the fuel, tetragonal, then monoclinic zirconia was identified as the main phases. Close to the bonding layer-cladding interface, peculiar Raman signals were observed. Similar signals were ob…
Heavy-Ion Microbeam Studies of Single-Event Leakage Current Mechanism in SiC VD-MOSFETs
2020
Heavy-ion microbeams are employed for probing the radiation-sensitive regions in commercial silicon carbide (SiC) vertical double-diffused power (VD)-MOSFETs with micrometer accuracy. By scanning the beam spot over the die, a spatial periodicity was observed in the leakage current degradation, reflecting the striped structure of the power MOSFET investigated. Two different mechanisms were observed for degradation. At low drain bias (gate and source grounded), only the gate-oxide (at the JFET or neck region) is contributing in the ion-induced leakage current. For exposures at drain–source bias voltages higher than a specific threshold, additional higher drain leakage current is observed in t…
Radiation effects on silica-based preforms and optical fibers-II: Coupling ab initio simulations and experiments
2008
International audience; Abstract—Experimental characterization through electron paramagnetic resonance (EPR) and confocal luminescence microscopy (CML) of a Ge-doped glass (preform and fiber) reveals the generation of several point defects by 10 keV X-ray radiation-induced attenuation: GeE', Ge(1), Ge(2), and Ge-ODC. The generation mechanisms of Ge-ODC and charged defects like GeE' centers are studied through ab initio simulation. Our calculations used a 108 atom supercell with a glass composition comparable to the Ge-doped core or to the pure-silica cladding of the canonical sample. The large size of our cell allows us to study the influence of the local environment surrounding the X-ODC d…
Impact of Terrestrial Neutrons on the Reliability of SiC VD-MOSFET Technologies
2021
Accelerated terrestrial neutron irradiations were performed on different commercial SiC power MOSFETs with planar, trench and double-trench architectures. The results were used to calculate the failure cross-sections and the failure in time (FIT) rates at sea level. Enhanced gate and drain leakage were observed in some devices which did not exhibit a destructive failure during the exposure. In particular, a different mechanism was observed for planar and trench gate MOSFETs, the first showing a partial gate rupture with a leakage path mostly between drain and gate, similar to what was previously observed with heavy-ions, while the second exhibiting a complete gate rupture. The observed fail…
Single-Event Burnout Mechanisms in SiC Power MOSFETs
2018
Heavy ion-induced single-event burnout (SEB) is investigated in high-voltage silicon carbide power MOSFETs. Experimental data for 1200-V SiC power MOSFETs show a significant decrease in SEB onset voltage for particle linear energy transfers greater than 10 MeV/cm 2 /mg, above which the SEB threshold voltage is nearly constant at half of the rated maximum operating voltage for these devices. TCAD simulations show a parasitic bipolar junction transistor turn-on mechanism, which drives the avalanching of carriers and leads to runaway drain current, resulting in SEB. peerReviewed