Papers by Keyword: Radiation Effects

Abstract: In this work, total dose effects on 4H-SiC bipolar junction transistors (BJT) are investigated. Three 4H-SiC NPN BJT chips are irradiated with 3MeV protons with a dose of 1×10¹¹, 1×10¹² and 1×10¹³ cm^-2, respectively. From the measured reciprocal current gain it is observed that 4H-SiC NPN BJT exposed to protons suffer both displacement damage and ionization, whereas, a traditional Si BJT suffers mainly from displacement damage. Furthermore, bulk damage introduction rates for SiC BJT were extracted to be 3.3×10^-15 cm², which is an order of magnitude lower compared to reported Si values. Finally, from detailed analysis of the base current at low injection levels, it is possible to distinguish when surface recombination leakage is dominant over bulk recombination.

Abstract: This paper shows a comparison between two different MOSFET structures: a conventional layout (CM) and Diamond (DM - enclosed layout transistor), as tolerance to the Single Event effect - SEE. Both CMOS 0.35μm technology devices types have the same geometric factor (W/L) and during irradiation were monitored continuously to detect and acquire the SEEs applying a new approach with a PXI test system. For this work was used heavy ion beams produced at the São Paulo 8 UD Pelletron accelerator.

Abstract: Steel 30CrMnSiNi2A slices were irradiated by a continuous wave fiber laser beam with the intensity of 14.5W/cm². Alloy samples with various temperature processes were obtained by changing the laser irradiation time, irradiation times and atmosphere environment. X-ray diffraction, scanning electron microscope, energy dispersive spectrometer and nanoindentation system were employed to characterize their microstructure morphology and mechanical properties. Three layers were observed in the samples fracture, namely oxide film, hard brittle layer and alloy substrate. The hard brittle layer had a higher hardness and a lower toughness compared with the base metal. Referring to the temperature history, we deemed that the surface oxidation and the solid phase transformation were the main factors which changed laser coupling efficiency. The results also illuminated the correlation between the microstructure morphology and the response to laser irradiation of the samples.

Abstract: Hardware-software subsystem designed for MOSFETs characteristic measurement and SPICE model parameter extraction taking into account radiation effects is presented. Parts of the system are described. The macromodel approach is used to account for radiation effects in MOSFET modeling. Particularities of the account for radiation effects in MOSFETs within the measurement and model parameter extraction procedures are emphasized. Application of the subsystem is illustrated on the example of radiation hardened 0.25 μm SOI MOSFET test structures.

Abstract: Electron beam radiation effects of PET have been investigated. Microstructural changes in poly(ethylene terephthalate) subjected to electron beam irradiation at doses of 50kGy, 100kGy, 200kGy, 400kGy were investigated by Attenuated total reflectance infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD) , Atomic force microscopy (AFM) and scanning electron microscopy (SEM). Irradiated samples showed a increase of crystallinity with a minimum at 200kGy, which is attributed to secondary crystal and then an decrease at further doses due to some degradation effect. The chemical structure and surface topography has only a slight change with irradiation.

Abstract: The thermodynamic and kinetic properties of Fe-Cu alloys are studied by ab initio calculations, in the framework of a multiscale modeling of precipitation kinetics. The configuration energies at various compositions, the solute migration and binding energies, as well as the vacancy formation and binding energies are computed. The effects of the local copper distribution on the migration barriers are considered. We show that a simple diffusion model with effective interactions on a rigid lattice, which includes a description of the saddle-point configurations, captures the main features of the energetic landscapes explored by the vacancy during its diffusion in dilute and concentrated configurations.

Abstract: The effects of neutron-irradiation near 80°C on the deformation behavior of hexagonal close packed (hcp) materials, zirconium and zircalloy-4, were investigated by transmission electron microscopy (TEM). Particular emphasis is placed on the deformation microstructure responsible for the changes in mechanical behavior. Neutron irradiation at low temperature up to 1 dpa induced a high number density of defect clusters, which resulted in irradiation-induced hardening. Dislocation channel deformation is observed for doses greater than 0.1 dpa, and is coincident with prompt plastic instability at yield. TEM analysis suggests that the loss of work hardening capacity in irradiated zirconium and zircaloy-4 at higher doses is mainly due to dislocation channels that are formed under a high local resolved shear stress, leading to the observed localized deformation.

Abstract: Electrical charges may be transported in ceramics by not only electrons but also by electron-holes, ions, and protons. Especially in nuclear fusion environments, electrical conductivity by proton migration (protonic conduction) will play an important role, as supply of hydrogen isotopes is sufficient and working temperature for ceramics will be in general high. In the present paper, radiation effects on the electrical conductivity of perovskite-type oxides will be reviewed, emphasizing radiation effects on transport behaviors of hydrogen and on reducing behaviors of oxide ceramics. Some perovskite-type oxides are known to have large protonic conductivity and an electrical charge state of some atomic elements composing them can be studied easily by spectroscopic techniques.

Abstract: Ceramic matrix composites (CMC’s), particularly silicon carbide (SiC) fiber-reinforced SiC-matrix (SiC/SiC) composites, have been studied for advanced nuclear energy applications for more than a decade. The perceived potentials for advanced SiC/SiC composites include the ability to operate at temperature regimes much higher than heat-resistant alloys, the inherent low inducedactivation nuclear properties, and the tolerance against neutron irradiation at high temperatures. This paper reviews the recent research and development of the advanced radiation-resistant SiC/SiC composites for nuclear applications. Additionally, remaining general and specific technical issues for SiC/SiC composites for nuclear applications are discussed.

Abstract: As one of the most important breakthrough in the field of SiC/SiC composite materials, the new process called Nano-powder Infiltration and Transient Eutectoid (NITE) Process has been developed. The outstanding total properties of the NITE SiC/SiC composites are presented. Then, the current efforts to make attractive GFR based on the NITE SiC/SiC composites and the technology R & D to make reactor components with the NITE SiC/SiC composites are provided together with our efforts on innovative reactor designs.