High Energy Xe Research Articles

Radiation Damaging of 3C-SiC Lattice: Computer Simulation of Brownian Motion of Non-Point Defects

The formation of porosity in thin layers of coating under its processing using the flux of high energyXe++is happen under the physical processes of nucleation of gaseous defects. The process is described by kinetic equations of Kolmogorov-Feller and Einstein-Smolukhovskii. The initial stage of the phase transition is considered as the superposition of two random processes: clustering of defects and their brownian motion. In the paper, we showthat a damaging phenomenon in layers can be predicted by means of computer experiments. The kinetic distribution function (DF) of defects depends on sizes and depth their penetration into materials under irradiation. Computer simulation of DF allows analysing the porosity and elastic stresses in bilayer caused byXe++blistering. The structures of defects are accumulated inSiClayer due to phase transition as well as a result the action perturbation of elastic forces in thin layers.

TEM study of damage recovery in SiC by swift Xe ion irradiation

The microstructure of 4H–SiC samples subsequently irradiated with low energy He (10keV), Ti (220keV) and high energy (167MeV) Xe ions has been studied using cross-sectional transmission electron microscopy. It was found that xenon ions with fluences above 1013cm−2 restore crystallinity in a heavily damaged partially amorphous zone. No, or negligible damage recovery is observed in fully amorphized layers of silicon carbide.

1.2 MeV/amu Xe ion induced damage recovery in SiC

The microstructural changes of 4H-SiC samples dual irradiated with either low energy He (10keV) or Ti (220keV) and high energy (167MeV) Xe ions has been studied using cross-sectional transmission electron microscopy. It was found that xenon ions with fluences above 1013cm−2 restore crystallinity in a heavily damaged partially amorphous zone. No significant damage recovery was observed in fully amorphized layers of silicon carbide apart from a 5% reduction in the amorphous layer thickness.

Electrophysical and Optical Properties of 4H-SiC Irradiated with Xe Ions

A comparative research of the cathodoluminescence and electrical characteristics of the samples 4H-SiC irradiated with high energy Xe ions (167 MeV) in wide range fluencies 4x109 –1x1011 cm-2 at temperatures 250C and 5000C are presented. After irradiation these samples were thermal annealed at 5000C for 30 min. Far-action effect at a depth of more than one order of magnitude of stopping distance was observed under Xe ions irradiation in 4H-SiC. An increase of the ion Xe fluencies increased the concentration of radiation-induced defects that resulted in rise of the compensation effect of conductivity in samples. Irradiation of 4H-SiC by Xe ions at 5000C was accompanied with "dynamic annealing" some low-temperature radiation-induced defects, which led to a partial recovery of the electrical characteristics of devices. The thermal annealing of irradiated samples led to additional partial annealing of radiation defects, which increases the radiation resource of devices based on 4H-SiC.

Nanoindentation investigation of heavy ion irradiated Ti3(Si,Al)C2

Abstract Because of good damage tolerance, thermal stability and interesting mechanical properties, Ti3SiC2, belonging to Mn+1AXn phases, has been considered as a potential candidate material for applications in the future Gas Fast nuclear Reactors (GFR) such as components of fuel cladding working between 500 °C and 800 °C. However, the outstanding mechanical properties of Ti3SiC2 related to a layered microstructure could be impacted by irradiation. In this work, high energy Kr and Xe ion irradiated Ti3Si0.95Al0.05C2 and Ti3Si0.90Al0.10C2 samples, provided by IMR Shenyang, Chinese Academy of Science, were characterized by nanoindentation technique. After irradiation at room temperature, an increase in hardness with irradiation dose was highlighted. Nevertheless, some damage tolerance remained because of preservation of the typical MAX layered structure. Irradiations at 300 °C and 500 °C lead to less significant increase suggesting irradiation defect annealing. A complete recovery of the properties at 800 °C seems to be obtained.

Impedance and barrier capacitance of silicon diodes implanted with high-energy Xe ions

Abstract Characteristics of Si p + n diodes with non-uniformly distributed compensating defects, which were introduced by implantation with Xe 23+ ions, have been studied. The layer with the maximum concentration of the compensating defects was located in the vicinity of the metallurgical p – n junction. It is found that the presence of the defect layer results in non-monotonic dependences of the imaginary part of impedance (− Z ″) and differential conductance ( G = −d I /d U ) of the implanted diodes on reverse bias voltage U . An equivalent circuit of the irradiated diode is proposed, which allows us to approximate the measured frequency dependences of capacitance and conductance of the irradiated diodes and to determine values of diode barrier capacitance C pn at different reverse bias voltages.

XRD investigation of ion irradiated Ti 3Si 0.90Al 0.10C 2

Ti 3SiC 2 is one of the most promising materials belonging to M n +1AX n phases, which exhibit good damage tolerance, thermal stability and mechanical properties. Recently, in the frame of research on future gas cooled fast nuclear reactors, Ti 3SiC 2 has been considered as an innovative candidate material, which could be incorporated in some core components such as fuel cladding. At the present time, however, very few data are available concerning the behaviour of this material after irradiation. In this work, Ti 3Si 0.90Al 0.10C 2 samples were irradiated with high energy Kr and Xe ions and characterized by X-ray diffraction. Patterns were analysed in terms of change in peak intensity, peak position and width. Rietveld refinements were also performed. Increase in micro-strains and lattice parameter with irradiation dose was highlighted. The formation of β-Ti 3SiC 2, which has never been observed by experimental XRD on non irradiated material, was proposed for the highly irradiated samples. A partial recovery of the microstructure with temperature was found.

Color center formation in silica glass induced by high energy Fe and Xe ions

Silica glass samples were implanted with 1.157 GeV 56Fe and 1.755 GeV 136Xe ions to fluences range from 1 × 10 11 to 3.8 × 10 12 ions/cm 2. Virgin and irradiated samples were investigated by ultraviolet (UV) absorption from 3 to 6.4 eV and photoluminescence (PL) spectroscopy. The UV absorption investigation reveals the presence of various color centers (E′ center, non-bridging oxygen hole center (NBOHC) and ODC(II)) appearing in the irradiated samples. It is found that the concentration of all color centers increase with the increase of fluence and tend to saturation at high fluence. Furthermore the concentration of E′ center and that of NBOHC is approximately equal and both scale better with the energy deposition through processes of electronic stopping, indicating that E′ center and NBOHC are mainly produced simultaneously from the scission of strained Si–O–Si bond by electronic excitation effects in heavy ion irradiated silica glass. The PL measurement shows three emissions peaked at about 4.28 eV (α band), 3.2 eV (β band) and 2.67 eV (γ band) when excited at 5 eV. The intensities of α and γ bands increase with the increase of fluence and tend to saturation at high fluence. The intensity of β band is at its maximum in virgin silica glass and it is reduced on increasing the ions fluence. It is further confirmed that nuclear energy loss processes determine the production of α and γ bands and electronic energy loss processes determine the bleaching of β band in heavy ion irradiated silica glass.

High energy heavy ion induced structural disorder in Li 2TiO 3

Li 2TiO 3 ceramics have been irradiated with xenon (Xe) ions in the energy range of 18–160 MeV at ambient temperature. The effect of ion irradiation on the order in the atomic arrangement of Li 2TiO 3 crystal was examined by X-ray diffraction (XRD) and Raman spectroscopy. The results show that the atomic arrangement in Li 2TiO 3 is strongly disordered by the high energy Xe ion irradiation. The destruction of long-range order due to the irradiation was confirmed from the reductions in XRD intensities of the (0 0 2) supercell reflection. The destruction of short-range order was confirmed from the reductions in the Raman intensities and disappearances of Raman bands with fluence. The disordering is more efficient with the increase in the electronic stopping power than with fluence or accumulated electronic energy deposition. These disorders due to the irradiation are discussed in relation to irradiation parameters such as electronic stopping power, accumulated electronic energy deposition and fluence.

Radiation resistance of quartz glass for VUV discharge lamps

Electrically-fused quartz glass, flame-fused quartz glass and plasma-fused quartz glass as well as synthetic fused silica samples were irradiated stepwise with a high energy Xe barrier discharge excimer lamp at 172 nm. VUV spectra were measured before and after every irradiation step. The results show that the VUV transmittance and the resistance against high energy radiation strongly depend on the quartz glass type, as well as on the thermal pretreatment of the quartz glass samples. In electrically-fused and plasma-fused quartz glass the VUV transmission decreases by the formation of oxygen deficiency and E′ centres with absorption bands at 163 nm and 215 nm. Best irradiation resistance is found in synthetic fused silica and in thermally treated flame-fused quartz glass.Photoluminescence spectra measured under excitation with a KrF excimer laser before and after irradiation indicate fundamental differences in the SiO2 network structure of the different quartz glass types. Whereas a poor radiation resistance correlates with a blue photoluminescence band at 390 nm, the photoluminescence of flame-fused quartz glass changes from blue to green by a thermal treatment which is correlated with a significant improvement of radiation resistance. A simplified model is presented referring to hydride and oxygen deficiency centres as precursors to colour centre formation in different types of quartz glass.

Morphology and Stability of Flux Grown Blue Emitting BAM Phosphors for Plasma Display Panels Applications

The (BAM) phosphor is being used as a blue component in plasma display panels (PDPs) due to its color purity as well as its high luminescence efficiency. When compared to two other components (green and red), the degradation in brightness of the BAM phosphor is high. To understand the role of morphology in the degradation mechanism, a number of BAM samples with various flux materials, viz., alkali halides along with halides of ammonium and/or aluminum were prepared. In addition to green shift (peak maximum shifts toward green), the degradation in intensity of these phosphor materials was studied by heating samples in moisture and by exposing them to a high energy Xe flash lamp or Kr excimer lamp. By employing a specific type of alumina as a starting chemical and a suitable flux material in the preparation of the BAM phosphor by solid-state reaction, the green shift could be eliminated and the degradation minimized.

Track formation on LiF single crystal surface induced by high-energy Xe ions

Energetic-ion-induced surface and island tracks (i.e. tracks in island gold film) on the surface of LiF single crystal were studied by electron microscopy. Irradiations were carried out by 4.17 MeV/nucleon Xe ions at incidence angles of 1°, 2°, 3°, 6°, 20°, 50° and 75° relative to the crystal surface. The size and shape of the observed surface and island tracks were compared. At the three most grazing irradiations we applied upper and lateral collectors in order to compare the total amount of removed islands with the collected ones. Collectors were studied by both electron microscopy and atomic force microscopy. We discuss our observations in the framework of some of the existing sputtering mechanisms.

Heteronuclear rare-gas dimer bonding: Understanding the nature of the Rydberg states that dissociate to the highest energy level of the Xe*(5d) manifold

(1+1 ′ ) resonance enhanced multiphoton ionization (REMPI) spectra of jet-cooled KrXe and ArXe in the vicinity of the high energy Xe*5d[3/2]10←Xe(1S0) atomic line at 83889.99 cm−1 were obtained by exciting the neutral dimers with tunable coherent vacuum ultraviolet (VUV) radiation generated by four-wave sum mixing in mercury vapor, and then detecting the resultant ions in a time-of-flight (TOF) mass spectrometer. Precise excited state constants were derived from analyses of the resultant vibrational fine structure, while equilibrium bond lengths were estimated from Franck–Condon factor intensity simulations. Excited state symmetries were deduced from separate ultraviolet (UV) (2+1) REMPI spectra recorded with linearly and circularly polarized light. The results of this work confirm a recent model proposed by Lipson and Field, where the RgXe*(5d) states are predicted to be strongly destabilized relative to RgXe*(6p) due to strong 5d-6p Xe* l-mixing induced by the ground state Rg atom partner making up the dimer. Orbital mixing is also responsible for the observation of appreciably strong RgXe*(5d) spectra in both one- and two-photon excitation.

Scaling of the Hall resistivity in epitaxialHgBa2CaCu2O6+δthin films with columnar defects

We have studied the Hall scaling relation ${\ensuremath{\rho}}_{\mathrm{xy}}=A{\ensuremath{\rho}}_{\mathrm{xx}}^{\ensuremath{\beta}}$ for the mixed-state Hall effects of ${\mathrm{HgBa}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{6+\mathrm{\ensuremath{\delta}}}$ thin films before and after irradiation by high-energy Xe ions. \ensuremath{\beta} increases from $1.0\ifmmode\pm\else\textpm\fi{}0.1$ to $2.0\ifmmode\pm\else\textpm\fi{}0.1$ as a perpendicular magnetic field increases from 0 to 8 T, and increases from $1.0\ifmmode\pm\else\textpm\fi{}0.1$ to $1.5\ifmmode\pm\else\textpm\fi{}0.05$ as the angle between the columnar tracks and a 4 T field decreases from 75\ifmmode^\circ\else\textdegree\fi{} to 0\ifmmode^\circ\else\textdegree\fi{}. The observation of $\ensuremath{\beta}=1$ is consistent with a recent theory based on d-wave superconductivity, in which the Hall angle was predicted to show a universal behavior that was independent of the mean free path of charge carriers in the low-field region.

Basic Properties of a Zirconia-Based Fuel Material for Light Water Reactors

The properties of zirconia cubic solid solutions doped with yttria, erbia, and ceria or thoria are investigated with emphasis on the potential use of this material as an inert matrix for Pu incineration in a light water reactor. The material is selected on the basis of its neutronic and chemical properties; Zr and Y are not neutron absorbers. Among the rare-earth elements, Er was identified as a suitable burnable poison and was found to be the best among the rare-earth elements. The high-density cubic solid solution is stable for a rather large range of compositions and from room temperature up to ~3000 K. The selected zirconia-based material has rather low heat conductivity (~2 W·m-1·K-1) compared to UO2, and the annular pellet design was consequently suggested to overcome this low-energy transfer characteristic. Samples irradiated with low- and high-energy Xe ions up to a fluence of 1.8 × 1016 Xe·cm-2 were investigated by transmission electron microscopy. Low-energy (60-keV) Xe ions did not produce amorphization. From the observed bubble formation, swelling values during irradiation at room temperature and at high temperature (925 K) were estimated to be 0.19 and 0.72% by volume, respectively. Furthermore, no amorphization was obtained by Xe irradiation under extreme conditions such as high-energy (1.5-MeV) Xe ion irradiation and low temperature (20 K). This confirms the robustness of this material and argues in favor of the selection of a zirconia-based material as an advanced nuclear fuel for Pu incineration.

Tetragonal WSi2 formation by 0.5–5 MeV Xe-ion-beam irradiation at 250 °C and 450 °C

We studied two-step tungsten-silicidation processes, which consist of low-energy W implantation followed by high-energy Xe irradiation. The formation of silicides was studied by Rutherford backscattering spectroscopy, x-ray diffraction and transmission electron microscopy. The formed silicide layer is richer in Si than that formed by thermal annealing. The transformation from the hexagonal to tetragonal (usually formed by thermal annealing above 600 °C) WSi2 phase occurred and a tetragonal WSi2 layer was successfully formed by 1-MeV Xe+ and 5-MeV Xe++ ion irradiation at under irradiation temperatures of 410 and 450 °C. The transformation did not occur by 0.5-MeV Xe+ ions at the same substrate temperature. The tetragonal phase was also observed after irradiation by 1-MeV Xe+ at 250 °C. The phase transformation rate normalized to the nuclear energy deposition density En increases with the electronic energy deposition density Ee. This fact indicates that the phase transformation is enhanced by the inelastic electronic scattering of high-energy ion irradiation. The irradiation temperature dependence of the phase transformation was also studied. The mechanism of the silicidation by elastic nuclear scattering and that of the phase transformation by inelastic electronic scattering of high-energy heavy-ion-beam irradiation are qualitatively discussed.

Behaviour of Zirconia Based Fuel Material Under Xe Irradiation

AbstractThe behaviour of ZrO2-10%YO1.5-5%ErO1.5-( 10%ThO2) (At %) cubic solid solutions under low and high energy Xe ion irradiation up to a fluence of 1.8·1016 Xe.cm−2 was investigated by TEM. Low energy (60 keV) Xe ions did not yield amorphization. From the observed bubble formation, swelling values of less than one volume per cent were estimated to be 0.19–0.72% during irradiation at room temperature or at high temperature (925 K). Furthermore, no amorphization was obtained by Xe irradiation under extreme conditions such as high energy (1.5 MeV) Xe ion and low temperature (20 K). This confirms the robustness of this material and argues in favour of the selection of zirconia based material as an advanced nuclear fuel for plutonium disposition.

Gas-phase fast-atom bombardment mass spectrometry

Gas-phase fast-atom bombardment (FAB) mass spectra of fullerene C 60, polycyclic aromatic hydrocarbons, n-hydrocarbons, heterocyclic compounds, and others, by using high energy He, Ar, Xe, or isobutane beams, have been compared with the electron impact ionization (EI) and/or charge exchange ionization (CEI) mass spectra. The positive ion gas-phase FAB mass spectra measured show a fragmentation pattern characterized by a high intensity of lower-mass fragment ions and considerable fragmentation, the extent of which exceeded that in the He CEI mass spectra, and an intense peak corresponding to molecular ions M ·+. From the results obtained it was suggested that the internal energy distribution of M ·+ ions formed under gas-phase FAB conditions ranges widely from the non-fragmenting lower energy to considerable fragmenting higher energy. The Massey criterion for the He (8 keV) beam indicated that a single collision between a fast atom A fast and an analyte molecule M gas brings about the formation of singly and/or doubly charged molecularions as the most likely energy deposition process. The formation of multiply charged molecular and fragment ions. M ·+ and m 2+ ( z = 1–4), and the extent of fragmentation seemed to be dependent on the structure of the analyte molecules, as well as the bombarding particles used. The mechanisms of formation of positive and negative molecular ions M +, M -, and [M-H] -, under gas-phase FAB conditions, has been discussed on the basis of the positive and negative ion mass spectra obtained.

Electronic state distribution of Xe+* formed by excitation transfer from He(2 3S) to Xe+(2P3/2) at thermal energy

The formation process of Xe+* in the He afterglow reaction of Xe has been studied by observing Xe ii lines in the ultraviolet and visible regions. Sixty one Xe+* states in the 13.86–19.49 eV range were excited by the He(2 3S)+Xe+(5p5 2P03/2) excitation-transfer reaction. It was found that Xe+* was not formed by the He(2 3S)+Xe(6s 3P02) Penning type reaction and the He++Xe(6s 3P02) charge-transfer reaction. There were some unclassified Xe ii lines, which occupied 14% of the total production of Xe+*. Most of them were attributed to Xe+ transitions from unknown high energy Xe+* states in the 18–19.5 eV range. The electronic state distribution of individual Xe+* levels has been determined by taking account of radiative cascade for low lying electronic levels. The He(2 3S)+Xe+(2P03/2) reaction expressed no resonant character. The electronic state of Xe+* was distributed more widely than those of Ar+* and Kr+* in the He(2 3S)+Ar+(3p5 2P03/2), He(2 3S)+Kr+(4p5 2P01/2), and He(2 3S)+Kr+(4p5 2P03/2) reactions. The excitation mechanism of rare gas cations due to collisions between a rare gas metastable atom and a rare gas ion is discussed. The lack of the excitation processes of Kr+* and Xe+* by the He++Kr(3P02) and He++Xe(3P02) reactions was attributed to the absence of near-resonant Kr+(5p) and Xe+(6p) states whose excitation satisfies the selection rule of Δl=±1.

Penetration of high energy ions in semiconductors through tracks: simulation with transport equations

The effect of channeling of high energy ions through latent tracks in solids is described theoretically by means of transport equations. It is shown that deep tails in implanted impurity and radiation damage depth distributions by high energy ion implantation can be explained by this effect. The experimental data obtained for silicon and diamond implanted with high energy Ni, Kr, and Xe ions are compared with theoretical predictions.