The void-swelling behaviour of solution-treated FV548 stainless steel irradiated with 22 MeV C2+ and 46.5 MeV Ni6+ ions and the influence of heat-treatment

A study has been made of the void-swelling behaviour of 1150°C solution-treated FV548 steel irradiated with 22 MeV C²⁺ and 46.5 MeV Ni⁶⁺ ions in the Harwell Variable Energy Cyclotron (VEC) after pre-injection with 10 ppm helium. The temperature dependence of void-swelling in the range 400–700°C, and the dose dependence of void-swelling at 600°C, have been established. In addition, the effects of ageing at 650°C, solution-treatment at 1300°C, and irradiation without helium pre-injection, on the void-swelling at 600°C have been investigated.Differences between void-swelling values obtained using C²⁺ ions, Ni⁶⁺ ions, and previously reported values obtained from 1 MeV electron irradiation of 1150°C solution-treated FV548 steel are discussed, as are the marked differences between the void-swelling behaviour reported here for VEC-irradiated FV548 steel and the established behaviour of type 316 steel irradiated under the same conditions. Finally, the present results are compared with the published data on reactor-irradiated solution-treated FV548 steel.     

Interstitial loop nucleation and growth in solution-treated type 316 stainless steel irradiated to low doses with 22 MeV C2+ and 46.5 MeV Ni6+ ions

The nucleation and growth of interstitial dislocation loops have been studied in solution-treated type 316 austenitic steel irradiated to low doses in the Harwell Variable Energy Cyclotron. Specimens have been irradiated with 46.5 MeV Ni⁶⁺ ions and 22 MeV C²⁺ ions, after room temperature pre-injection with 10 ppm helium and without helium pre-injection, at temperatures in the range 300–600°C. The effects of these irradiation variables on the interstitial loop populations produced are discussed. At low doses, where loop intersection is rare and dislocation network formation is minimal, the number of interstitial atoms stored in loops can give an indication of the swelling rate in circumstances where voids remain submicroscopic. It is shown that extrapolation of the low-dose swelling rates indicated by interstitial loop populations gives reasonable fit with experimentally determined high-dose void swelling values.     

The influence of different inert gases on void nucleation in stainless steel bombarded by 46.5 MeV Ni6+ ions

The implications of irradiation-induced re-solution of inert gas atoms for the nucleation of voids is discussed. The differences between light gases such as helium and the heavier gases such as argon is highlighted as these are shown to give rise to quite different behaviour. For instance, helium is considered to migrate through the solid predominantly by enhanced interstitial diffusion, whereas argon migrates by enhanced vacancy diffusion. This difference gives rise to quite different nucleation densities and has a dramatic effect on the total void swelling. The main predictions of the model have been checked experimentally using ion-bombardment techniques and the results of these experiments are discussed in some detail.     

Vacancy cluster damage in type 316 stainless steel irradiated with Cr+ ions

An electron microscope study has been made of damage in Type 316 stainless steel irradiated to low doses at room temperature with 40, 80, 120 and 200 keV Cr⁺ions. The visible clusters are dissociated Frank loops and stacking fault tetrahedra and it is deduced that they are vacancy in nature having formed by collapse of displacement cascades. Quantitative analysis of the structures have shown that the defect yield and cascade efficiency are approximately independent of incident ion energy and are much lower than in self-ion irradiated pure copper. This and the fact that reducing the level of carbon in solution in the stainless steel increases the cascade efficiency is attributed to the role played by the alloy elements and impurities in defocussing focussed collision sequences and thereby enhancing interstitial-vacancy recombination in cascades. Lastly, the present results are considered in terms of their implication to the formation and growth of voids during irradiation of Type 316 stainless steel at elevated temperatures.     

He+ (np) cross sections for 2, 3, 4 and 5 MeV C4+ ions colliding with He atoms

The cross sections of ionization plus excitation of He are measured by the C⁴⁺ + He prototype reaction with energies ranging from 2 to 5 MeV. Theoretically the independent electron approximation is used to calculate the HeII (np) ionization plus excitation cross sections. The results of the calculations are compared with our experimental data.     

The influence of pre-injected helium on void nucleation and growth in FV548 steel irradiated with 1 MeV electrons

A study has been made of the effect of helium pre-injection on the void populations produced in solution-treated specimens of FV548 austenitic steel irradiated with 1 MeV electrons in the temperature range 450–650°C. The results suggest that helium atom clusters, created during pre-injection, act as void nuclei during subsequent irradiation, although the helium cluster-void transition is limited at high irradiation temperatures by a rapid temperature-dependent increase in the critical void nucleus size. In most cases the void swelling rates at 600 and 650°C decreased with increasing void number density. This was not the case in those specimens in which helium had been pre-injected at elevated temperatures, suggesting that void swelling is an extremely sensitive function of the balance between the void and dislocation sink strengths.     

Void formation in solution-treated aisi 316 and 321 stainless steels under 46.5 mev ni6+ irradiation

The swelling and radiation damage structure developed in solution-treated 316 and 321 stainless steels bombarded by 46.5 MeV Ni⁶⁺ ions in the Variable Energy Cyclotron (VEC) have been determined. Foils were pre-injected with 10^?5 a/a He at room temperature and subsequently bombarded by Ni⁶⁺ ions in the temperature range 450–750°C at a damage rate of 1–3 × 10^?3 dpa per second to doses up to 300 dpa and specimens from the foils were examined by transmission electron microscopy. The data obtained were compared with data from other experiments aimed at simulating the fast-neutron irradiation of 316 and 321 steels, in particular previous work with 20 MeV C²⁺ ions and with data on fast-reactor bombarded material. The swelling rates in Ni-ion bombarded specimens were about a factor two less than those in C-ion bombarded specimens and in good agreement with swelling rates in 5 MeV Ni⁺- and neutron-bombarded material. The peak swelling temperature after a dose of 40 dpa was 650°C in 316 steel and 625°C in 321 steel where the swelling was about 5.8% and 4.6% respectively.     

(n,l)−Subshell electron capture cross sections in collisions of C4+, N5+ and O6+ with atomic hydrogen

By means of VUV-photon spectroscopy we have determined absolute Subshell selective electron capture cross sections σ_nlfor collisions of helium-like carbon, nitrogen and oxygen ions with atomic hydrogen, in the velocity range 0.1–0.5 a.u.The atomic hydrogen beam target was produced by means of a radio-frequency discharge source, and absolutely calibrated by measuring atomic and molecular radiation in the visible region produced by electron impacts.For all systems studied we find that the total capture cross section (σ_t = Σ_nlσ_nl depends only weakly on the impact velocity, and is in good agreement with published results from other authors. In contrast to σ_t, the Subshell selective cross sections σ_nl are strongly velocity dependent.Our results are compared with recent calculations by Fritsch and Lin; the agreement is quite satisfactory.     

Observation of a partially-ordered void lattice in aluminium irradiated with 400 keV Al+ ions

Transmission electron microscopy observations of voids formed in aluminium during irradiation at 50°C and 75°C with 400 keV Al⁺ ions, have shown that partially-ordered void arrays are often present. These arrays occur in high-purity annealed aluminium, which has been implanted with 10^?4 atom/atom helium before ion irradiation. The void concentration is found to be $\text{～3 × 10}{}^{16}\text{/ cm}{}^3$, and the void lattice parameter ～ 700 Å. The ratio of void lattice parameter to void radius is ～ 12. Ordered void lattices have been observed frequently in irradiated body-centred cubic metals but the only previous observation for a face-centred cubic metal was in nickel. Theoretical predictions of void lattices in metals are discussed and related to the observations reported herein.     

Oxygen defects created in CeO2 irradiated with 200 MeV Au ions

CeO₂ films were irradiated with 200 MeV Au ions in order to investigate the damages created by electronic energy deposition. In the Raman spectra of the ion-irradiated films, a broad band appears at the higher frequency side of the F_2g peak of CeO₂. The band intensity increases as ion fluence increases. Furthermore, the F_2g peak becomes asymmetric with a low-frequency tail. In order to understand the origin of these spectral changes, an unirradiated CeO₂ film was annealed in vacuum at 1000 °C. By comparing the results for the irradiation and for the annealing, it is concluded that the broad band obtained for irradiated samples contains the peak observed for the annealed sample. The F_2g peak becomes asymmetric with a low-frequency tail by the irradiation as well as the annealing. Therefore, the above-mentioned changes in the Raman spectra caused by 200 MeV Au irradiation is closely related to the creation of oxygen vacancies.     

Populations of np terms in deuterium atoms emergent from carbon foils bombarded with D+, D2+ and D3+ ions

We have measured relative beam-foil populations of 2p, 3p, and 4p terms in D⁰ as a function of the projectile energy $\text{(20 ?}\text{E}\text{M}\text{? 500}\text{keV}\text{amu}\text{)}$ for D⁺, D₂⁺, and D₃⁺ ions impinging on carbon foils of various thicknesses (? 2–20 $\text{μg}\text{cm}{}^2$).With D⁺ projectiles, the np populations reach their equilibrium values even in the thinnest foils used. We compare the dependence on energy of these populations to the equilibrium neutral fraction variation for hydrogen (deuterium) beams emerging from a carbon foil and deduce some information concerning beam-foil populations.When molecular projectiles pass through very thin foils, well known molecular effects appear which depend on the dwell time, t, i.e., the time spent by the projectile in the foil. In this work we consider only the long-dwell-time region t > 2 × 10^?15s. We study the variation of R_α = I^molec/I^atom (I^molec and I^atom are the Ly-α intensities per incident deuteron (proton) observed with molecular and atomic projectiles of the same velocity, respectively) with the projectile energy per nucleon ($\text{E}\text{M}$) and the thickness (T) of the foil. For a foil of given thickness, R_α increases with $\text{E}\text{M>}$ and reaches a saturation value R_∞ which decreases when T increases. These results, in agreement with our previous measurements using hydrogen projectiles, indicate that t is not the only parameter relevant to molecular effects. Comparisons are reported between $\text{R>}{}_{\mathrm{\alpha }}\text{(E}\text{M>}$) values obtained (a) with H₂⁺ and D₂⁺ projectiles and (b) with D₂⁺ and D₃⁺ projectiles, using foils of various given thicknesses. Ratios $\text{R}{}_{\mathrm{\beta }}\text{(E}\text{M}$) and $\text{R}{}_{\mathrm{\gamma }}\text{(E}\text{M}$) are also measured using Ly-β and Ly-γ radiations and compared to $\text{R}{}_{\mathrm{\alpha }}\text{(E}\text{M}$) values. An interpretation for some of our results is proposed.     

羟基红花黄色素A对碳离子束辐照致放射性脑损伤的保护作用

探究传统活血化瘀中药红花活性成分羟基红花黄色素A(HSYA)对12C6+重离子束诱发放射性脑损伤的保护作用。昆明种小鼠60只,随机分为正常组、辐照对照组、HSYA低(5 mg/kg)、中(10 mg/kg)、高(20 mg/kg)剂量干预组。给药组于辐照前3 d起每日腹腔注射相应剂量药物,末次给药后1 h,以4.0 Gy12C6+辐照小鼠头部。辐照1个月后,通过Morris水迷宫实验检验小鼠认知功能,以伊文思蓝(EB)作为指示剂测定小鼠血脑屏障通透性,并分别用亚硝酸盐形成法和硫代巴比妥酸(TBA)法测定脑组织中超氧化物歧化酶(SOD)活性及脂质过氧化产物丙二醛(MDA)的含量。结果显示,经12C6+辐照后,单纯照射组小鼠表现出明显的认知功能障碍(P<0.01),小鼠血脑屏障通透性明显升高,脑组织SOD活性明显降低,MDA含量明显增加,羟基红花黄色素A可剂量依赖性地改善小鼠认知功能障碍,保护血脑屏障,上调SOD活性,并降低MDA含量,表明羟基红花黄色素A对12C6+重离子束诱发放射性脑损伤有保护作用。     

Structural changes in anatase TiO2 thin films irradiated with high-energy heavy ions

In order to investigate possible structural changes due to high-density electronic excitation, anatase TiO₂ thin film specimens were irradiated with 230 MeV ¹³⁶Xe¹⁵⁺ ions and 200 MeV ¹⁹⁷Au¹³⁺ ions. X-ray diffraction (XRD) patterns were measured before and after irradiation. The intensity of the XRD peak assigned to the (0 0 4) planes of anatase TiO₂ decreases in an exponential manner as a function of ion-fluence. This result can be explained by the formation of the cylindrical damaged regions (i.e. ion tracks) with diameters of 9.6 and 16.3 nm for 230 MeV Xe and for 200 MeV Au ion irradiations, respectively. The difference in the track diameter between Xe ion irradiation and Au ion irradiation can be attributed to the difference in the electronic stopping power (and to the ion-velocity effect, if any). For 200 MeV Au ion irradiation, splitting of the (0 0 4) peak is observed. The original (0 0 4) TiO₂ peak remains in the same position, but the new peak shifts to higher angles as fluence increases.     

Studies of 1s2s 3S-1s2p 3P transitions in helium-like Ne8+ recoil ions using photographic spectroscopy

This work describes the application of the technique of photographic VUV spectroscopy to accurate measurement of the wavelength of the theoretically interesting 1s2s ³S₁-1s2p ³P₂ transition in helium-like Ne⁸⁺ in a recoil ion source. Good resolution is obtained, and a preliminary value of 124.815±0.002 nm is found for the wavelength.     

Measurement of the energy deposition profile for U ions with specific energy 500 and 950 MeV/u in stainless steel and copper targets

The paper presents the results of precision measurements of the total stopping range and energy deposition function of ²³⁸U ions with specific energies E = 500 and 950 MeV/u in stainless steel and copper targets. The experiment was performed at the SIS-18 facility (GSI Darmstadt) in the experimental area Cave A in September 2004-May 2005.The measured energy deposition profiles are compared with calculations using the codes ATIMA, PHITS, SHIELD and SRIM.     

Experimental cross sections for two-electron capture into nitrogen autoionising states in Nq+ (q = 6, 7) on He and H2 collisions at 10.5q keV

Singly differential cross sections for two-electron capture into autoionising states (nl, n'l') with n = 2, 3, 4 and n′≥ in N^q+ (q = 6, 7) on He and H₂ collisions have been measured at 10.5q keV collision energy and an observation angle θ_lab =11.6°Total cross sections are estimated assuming isotropic angular distributions.