122 research outputs found
Ion-beam mixing induced by atomic and cluster bombardment in the electronic stopping-power regime
Single crystals of magnesium oxide containing nanoprecipitates of sodium were bombarded with swift ions (∼GeV-Pb, U) or cluster beams (∼20 MeV-C60) to study the phase change induced by electronic processes at high stopping power (≳10 keV/nm). The sodium precipitates and the defect creation were characterized by optical absorption and transmission electron microscopy. The ion or cluster bombardment leads to an evolution of the Na precipitate concentration but the size distribution remains unchanged. The decrease in Na metallic concentration is attributed to mixing effects at the interfaces between Na clusters and MgO. In addition, optical-absorption measurements show a broadening of the absorption band associated with electron plasma oscillations in Na clusters. This effect is due to a decrease of the electron mean free path, which could be induced by defect creation in the metal. All these results show an influence of high electronic stopping power in materials known to be very resistant to irradiation with weak ionizing projectiles. The dependence of these effects on electronic stopping power and on various solid-state parameters is discussed
SPORT: A new sub-nanosecond time-resolved instrument to study swift heavy ion-beam induced luminescence - Application to luminescence degradation of a fast plastic scintillator
We developed a new sub-nanosecond time-resolved instrument to study the
dynamics of UV-visible luminescence under high stopping power heavy ion
irradiation. We applied our instrument, called SPORT, on a fast plastic
scintillator (BC-400) irradiated with 27-MeV Ar ions having high mean
electronic stopping power of 2.6 MeV/\mu m. As a consequence of increasing
permanent radiation damages with increasing ion fluence, our investigations
reveal a degradation of scintillation intensity together with, thanks to the
time-resolved measurement, a decrease in the decay constant of the
scintillator. This combination indicates that luminescence degradation
processes by both dynamic and static quenching, the latter mechanism being
predominant. Under such high density excitation, the scintillation
deterioration of BC-400 is significantly enhanced compared to that observed in
previous investigations, mainly performed using light ions. The observed
non-linear behaviour implies that the dose at which luminescence starts
deteriorating is not independent on particles' stopping power, thus
illustrating that the radiation hardness of plastic scintillators can be
strongly weakened under high excitation density in heavy ion environments.Comment: 5 figures, accepted in Nucl. Instrum. Methods
Industrial applications of heavy ions beams at GANIL
International audienceAfter a year of research and development, BSI and GANIL started an industrial production of microporous membranes. The status of the technical and commercial problems is given. With the collaboration of industrial firms, other applications are studied, like : non reflecting surfaces, ion implantation, surface treatment, radiation damage..
Magnetic nanoconstrictions made from nickel electrodeposition in polymeric bi-conical tracks: Magneto-transport behavior
International audienceSingle nanoconstriction per magnetic wire is obtained by bi-conical track etching and electrodeposition. Magnetoresistance measurements at various angles result in irreversible jumps. Resulting jumps of magnetization have been attributed to the pinning and depinning of a constrained magnetic domain wall. a b s t r a c t In a cylindrical magnetic nanowire, a magnetic domain wall (DW) can move along the wire when an applied magnetic field or a spin-polarized current is applied. We show that in a magnetic device composed of two conical nanowires connected by a nanosized constriction, a DW can be trapped and detrapped. The magnetoreistance and the relaxation processes of the DW exhibit a specific behavior. Such a device has been fabricating by Ni electrodeposition in bi-conical tracks polymer membrane made of Swift Heavy Ions bombarded poly(VDF-co-TrFE) copolymer and poly(ethylene terephtalate) PET thin films. The latter method allows to monitor the conicity of the bi-conical wires and to give access to a panel of very well-defined structures.
Ion-beam mixing induced by atomic and cluster bombardment in the electronic stopping-power regime
Zirconium oxidation under high energy heavy ion irradiation
This paper concerns the study of zirconium oxidation under irradiation with
high energetic Xe ions. The irradiations were performed on the IRRSUD beam line
at GANIL (Caen). The oxygen partial pressure was fixed at 10 Pa and two
temperature conditions were used, either 480C reached by Joule effect
heating or 280C due to Xe energy deposition. Zirconia was fully
characterized by Rutherford Backscattering Spectrometry, Transmission Electron
Microscopy and Grazing Angle X-ray Diffraction. Apparent diffusion coefficients
of oxygen in ZrO2 were determined from these experiments by using a model which
takes into account a surface exchange between oxygen gas and the ZrO2 surface.
These results are compared with thermal oxidation data
Dielectric response of makrofol-KG polycarbonate irradiated with 145 MeV Ne6+ and 100 MeV Si8+ ions
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