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In atomic collisions in solids by the ions with very strong electronic interaction, it is confirmed that the atomic displacement process is enhanced by electronic excitation. Two experimental results are introduced as examples. The first is the columnar defect formation in a cuprate superconductor Bi2Sr2CaCu2Ox which is irradiated with 3.5 GeV Xe ions, the second is sputtering induced by highly charged ion (HCI) bombardment (Xeq+; q = 15 –44). Since there are some indications to show that these phenomena might be the outcome of the Coulomb explosion process, we tried to make a molecular dynamics simulation of the sputtering process based on this Coulomb explosion mechanism. Good agreement between the simulation and experiment was found. For sputtering of electrically conductive materials, the importance of neutralization dynamics of the HCI and the highly charged region in the solid materials was indicated.

The radiation damage and the radiation-induced segregation (RIS) in type 304 austenitic stainless steel single crystal were investigated with 1.6 MeV He ion irradiation up to 2.5 × 1017 cm−2 at RT by using RBS and PIXE with channeling conditions (RBS-C and PIXE-C). By the RBS-C experiments, it is found that radiation-induced damage for (1 1 0) orientation increased more slowly than those for (1 0 0) and (1 1 1) orientations with He ion dose. By the PIXE-C experiments, it is found that the Si atoms are displaced from the lattice sites and segregate significantly to the surfaces of (1 0 0), (1 1 0) and (1 1 1) orientations and the S atoms also seem to be enriched slightly in the (1 0 0) and (1 1 0) surfaces during He ion irradiation.

High purity iron sheets were implanted with high-dose nitrogen ions accelerated to 150 keV. The implanted surfaces were examined by thin-film X-ray diffraction method and high resolution transmission electron microscopy (HRTEM). The implanted surfaces contain the metastable Fe 16 N 2 phase in addition to ϵ-nitride. HRTEM reveals that Fe 16 N 2 domains have lattice fringes of double spacing along the [121] direction of the matrix and spherical morphologies with coherent interfaces.

The characterization of the single crystal of type 304 stainless steels was performed by using particle induced x-ray emission and Rutherford backscattering spectroscopy with channeling technique (PIXE-C and RBS-C). They proved that the solution annealing process is absolutely necessary for production of a good single crystal of stainless steels. They are also shown that the positions of P atoms before He irradiation were mostly substitutional sites of fcc structure and that MeV He ion irradiation induced segregation of Si and S atoms to the (110) surface.

Nickel single crystal specimens were bombarded with various heavy ions, 0.2 MeV He+, 2.0 MeV C+, 3.5 MeV Si2+, 4.0 MeV Ni2+ ions, up to the same amounts of displacement per atom (dpa), and residual rate of defects in heavy-ion induced cascades was investigated by Rutherford backscattering (RBS) spectroscopy using channeling technique. Displacement damages are found to be variable with primary knock-on atom (PKA) energies, revealing a cascade quenching due to the recombination of point defects produced primarily. Residual rate of defects obtained experimentally are qualitatively in agreement with existing theoretical calculations.

Variable-energy (0–30 keV) positrons were used to study the depth distribution of heavy-ion induced vacancy type defects in the following specimens, SUS304 and SUS316 austenitic stainless steels, a SUS444 ferritic stainless steel and nickel metal, which were irradiated by 0.5 MeV He+, 2.0 MeV C+, 3.5 MeV Si2+ and 4.0 MeV Ni2+ ions up to 0.01 dpa at peak. Vacancy type effective residual defects (ERD) were evaluated from the line shape parameterS of Doppler broadened positron annihilation photon spectra. With increasing primary knockon atom (PKA) energy, a decrease of the vacancy type ERD was observed. The ERD differences among the specimens are discussed in comparison with theoretical predictions.

The characteristics of stored ions in a Kingdon trap have been investigated. The charge distribution of stored ions was measured by a time of flight (TOF) mass spectrometer. Storage of Arq+ (q = 1, 2, 3, 4) produced by electron beam irradiation has been confirmed. The dependences of Ar ion yields on the trapping potential and storage time have been systematically studied. Applying a voltage to end plates is very important for the storage of ions. Remarkable oscillations of the ion yields are found in the decay curves as a function of storage time for Ar+, Ar2+ and Ar3+ indicating periodical motion of each ion group about the central wire. The three dimensional orbits of ions in the trap are analysed by a computer calculation to understand the experimental results.

K, L, and M X-rays in the wavelengths between 6Å and 130Å generated by the bombardment of 200 keV protons and other heavy ions were measured by means of a wavelength dispersive Bragg’s spectrometer. The X-ray peak intensity was fairly high in general, while the background was very low. The technique was favorably applied to a practical analysis of several light elements (Be, B, C, N, O, and F). Use of moderate-energy heavy ions considering the wavelength selectivity in X-ray generation was effective for the element analysis. The high-resolution spectrometry in the analytical application of ion-induced X-ray generation was found to be useful for the study of fine electronic structure, e.g. satellite and hypersatellite X-ray study, and of the chemical state of materials.

Analyses were conducted of various models and mechanisms of highly charged ion (HCI) and swift-heavy ion energy transfer into a solid target, such as hollow atom formation, charge screening, neutralization, shock wave generation, crater formation, and sputtering. A plasma model of space charge neutralization based on impact ionization of semiconductors at high electric fields was developed and applied to analyze HCI impacts on Si and W. Surface erosions of semiconductor and metal surfaces caused by HCI bombardments were studied by using a molecular dynamics simulation method, and the results were compared with experimental sputtering data.

The effects of columnar defects produced by swift heavy-ion irradiation on magnetic flux pinning were studied for the polycrystalline La1.85Sr0.15CuO4. The bulk specimens were irradiated with 3.5 GeV 136Xe31+ ions from a single direction or multi-directions in order to investigate the effects of columnar defect configuration. The magnetization hysteresis was measured with a super-conducting quantum interference device (SQUID) magnetometer, and the critical current density Jc and irreversibility line were observed. In the specimens irradiated from multi-directions, more enhancement of the critical current density and larger shifts of the irreversibility line to higher fields were observed than in the specimens irradiated from a single direction.

The behavior of a vortex system in the presence of columnar defects in a La1.85Sr0.15CuO4 single crystal irradiated with swift heavy ions (3.5 GeV 136Xe31+) is studied by measuring magnetization and AC susceptibility. The absolute value of the magnetization of the irradiated sample is significantly enhanced compared to the unirradiated one. The irreversibility line is shifted to higher temperatures as the defect density increases. It is found that for B > Bcr similar 0.5 T, " of irradiated samples exhibits double peaks, suggesting that the liquid-glass transition proceeds via two steps.

Carbon thin film was bombarded with high charge state Xeq+ ions, and the secondary carbon yields were measured as a function of charge state in the broad range of q = 8 to 44 at the kinetic energy of 1.0 MeV and, also, q = 44 at 175 keV. It is found that the secondary ion yields per incident ion increase with increasing q; the increase rate is remarkably high in q > 26 with the rate of q8.5 and rather moderate in q > 31. The yield and spectra of the secondary ions are not very different for 1.0 MeV and 175 keV for Xeq+ (q = 44) ion incidence.

High purity iron sheets were cold rolled and then irradiated with N/sub 2//sup +/ ions. Particles of iron nitride (Fe/sub 16/N/sub 2/:/spl alpha/") were formed in the specimens. With increasing rolling reduction, hardness of the specimen increases. TEM observations showed that sizes of /spl alpha/" decreased and number density of /spl alpha/" increased with reduction rate. Interactions between nitrogen atoms and irradiation damages are discussed.

The vortex pinning phenomena were investigated in type II high temperature superconducting material, polycrystalline La/sub 1.85/Sr/sub 0.15/CuO/sub 4/ to which 3.5 GeV Xe ion end 26 GeV Ar ion were irradiated. Changes of superconducting characteristics were measured before and after the ion irradiations using a superconducting quantum interference device (SQUID). In Xe irradiation as well as Ar irradiation, reduction of normalized rate of magnetic relaxation was observed. The reduction rate of Xe ion irradiated specimen was much larger than that of the Ar ion irradiated one. However, in polycrystalline LSCO, existence of grains with various directions and numerous grain boundaries may take considerable roles to pin vortex together with columnar defects. It appears that the creep rate obtained substantiates the collective creep model of the vortex.

Formation of high-quality optical films is increasingly important due to the rapid progress of optical components. These films must be durable, dense and very flat. We have developed a noble film formation process by cluster ion assisted deposition. Unique characteristics of cluster ion bombardment have been found such that it is applicable for various industrial applications that cannot be achieved by conventional ion beam processing (Yamada et al, 2000). Cluster ions can transport thousands of atoms per ion with very low energy and realize dense energy deposition within a very localized region, which enhances the chemical reaction between clusters and target atoms near its surface (Toyoda et al, 1997). Furthermore, cluster ions exhibit a surface smoothing effect due to lateral sputtering effects. These properties are useful for the formation of high quality thin films. In this work, we focused on optical thin films such as Ta/sub 2/O/sub 5/, TiO/sub 2/ and SiO/sub 2/. We have fabricated Ta/sub 2/O/sub 5//SiO/sub 2/ multi-layer structures with O/sub 2/ cluster ion assisted deposition and studied the quality of these optical films by AFM observations, environmental tests and various optical measurements.

Absolute yields for multiple electron capture as well as projectile ionization have been measured for 46 MeV/u U91+ ions traversing thin carbon foils with different surface topologies. Multiple electron capture yields vary strongly, depending on the target manufacturer. The samples including the one with the smoothest surface show a deviation of the yield from the expected scaling based on subsequent single capture for decreasing target thickness. This indicates a strong contribution of the surface, whose nature cannot be identified by the current data.

High purity iron (99.99%) bulk sheet was implanted with high-dose nitrogen ion. The implanted surface was examined by micro-Vickers hardness measurements, thin-foil X-ray diffraction method and high resolution transmission electron microscopy (HRTEM). The implanted surface contains metastable Fe 16 N 2 phase in addition to Fe 2.5 N and Fe 4 N phases. HRTEM showed that Fe 16 N 2 has spherical morphology and coherent interfaces. It was revealed, for the first time, by transmission electron microscopy that the metastable Fe 16 N 2 precipitates were formed in bulk iron by the implantation method.

Sintered polycrystalline La 1.85 Sr 0.15 CuO 4 was irradiated by 3.5 GeV 136 Xe 31+ ions at room temperature. The critical current density increase was found with very low ion fluence (≈1 × 10 11 /cm 2 ) without any degradation of the critical temperature. High resolution transmission electron microscopy revealed the formation of amorphous columnar defects by the ion irradiation, which is considered to play a major role for pinning magnetic fluxes in the oxide superconductors.

The irradiation effect of high energy heavy ions in a foil has been investigated by secondary ions spectroscopy in the energy region where the electronic stopping power is dominant. We observed significant enhancement of the secondary ion yield above the threshold value of the electronic stopping power, where the irradiation effect in high Tc super conductors and metallic materials becomes remarkable.

The application of ion-induced x-rays to spectrochemical analysis was examined by means of a dispersive method with a flat crystal and a 200-kV ion accelerator. For x-rays of longer wavelength than 10 A, x-ray count rates of the order of 104–105 c.p.s. were obtained; the use of heavy ions such as Kr+, Ne+ and O+ was shown to be effective for x-rays shorter than about 30 A, while protons were more efficient for longer wavelengths. X-Ray excitation efficiencies are almost independent of the atomic shell with which the x-rays are associated and are dependent on wavelength only, indicating that almost all elements can yield K, L or M x-rays of considerable intensity. The x-ray excitation method by proton and heavy ion bombardment was applied to the determination of some light elements, F, O, N and Be. Detection limits of 10 p.p.m. could be readily achieved for these elements.

Cross sections for single and double K-shell ionization of Be were obtained from K α diagram and hypersatellite X-ray yields produced by C, N, O and Ne ion bombardments with the energies from 0.3 to 1.3 MeV. The data are compared with the theoretical predictions which consider 2pσ-2pπ MO coupling. The results show a good agreement except for the collision system of Ne+Be.

The K α satellite and hypersatellite X-ray spectra have been measured for fluorine produced by 0.3–2.0 MeV H and He ion bombardments of the thick LiF target. The single and double K-shell ionization cross sections derived from the X-ray yields have been compared with theoretical calculations based on the binary-encounter approximation (BEA) and the semiclassical Coulomb approximation (SCA). The result shows that the observed cross sections for the single K-shell ionization agree with the BEA better than with the SCA and those for the double K-shell ionization systematically differ from the BEA by a factor of three.

Spectra of Al K α X rays induced by H and He ion bombardments in the energy range of 0.2–0.4 MeV/amu have been measured with a Bragg spectrometer and Z 1 dependence of single K- plus multiple L-shell (KL l ) ionization has been investigated. The result shows that the L-shell ionization probability of Al by light ion bombardments follows the scaling law of direct Coulomb ionization considering the binding energy correction.

Cross sections have been measured for K-shell vacancy production for F/sup 6 +/(1s/sup 2/2s) ions incident on He target atoms in the projectile energy range from 10 to 40 MeV. Collisions leading to F/sup 6 +/(1s2s2p) states are attributed to K-shell excitation. The cross sections for F/sup 6 +/(1s/sup 2/2s) to F/sup 6 +/(1s2s2p) excitation agree with a Born calculation for 1s-electron excitation. Collisions leading to F/sup 7 +/(1s2p) states are referred to as K-vacancy production to distinguish it from the K-shell excitation process. The energy dependence of the K-vacancy production cross section for the F/sup 6 +/(1s/sup 2/2s) to F/sup 7 +/(1s2p) process does not agree with the calculation for single 1s-electron ionization. The observed energy dependence is understood in terms of the sum of two two-step processes. One two-step process is 1s-electron ionization simultaneous with 2s-2p--electron excitation and the other is 2s-electron ionization simultaneous with 1s-2p--electron excitation. The latter process is dominant. The F/sup q/+ charge-state dependence at 15 MeV and the F/sup 8 +/ energy dependence for electron excitation, as previously reported, are also compared with theory.

The X-rays of the boron atom emitted from thick boron and boron nitride targets by bombardment with nitrogen (0.3–1.1 MeV) and argon (0.3–1.8 MeV) ions are investigated. The spectra from the boron target consist of two peaks due to single and double K-shell vacancies. For boron nitride, the spectra due to single and double K-shell vacancies have two and one satellites, respectively. The intensity ratio of the high energy side satellites of both spectra to each main peak increases with the decrease of the incident energy of the projectiles in the energy range examined. This fact suggests that the high energy satellites are due to the transition from the 2p level of the nitrogen atom to the 1s level of the boron atom with a 2p vacancy. Moreover, absolute cross sections have been measured for the single and double K-shell ionizatione of the boron atom by heavy ion bombardment. The energy dependence of the ionization cross sections suggests that the mechanism of the inner shell ionization is understood by the electron promotion model during the collisions.

The D permeation rate under bombardment of 50 keV D+ was measured at 500°C for Type 316 stainless steel which was pre-irradiated by 320 keV He ++. In addition, the D permeation rate was also measured during simultaneous bombardment of 57.5 keV D+ and 280 keV He ++ at 442°C. By pre-irradiation of 3 × 1017 He ++ cm−2, the D permeation rate was reduced to about 14 of that without He ++ irradiation. It was also found that a reduction of D permeation rate to about 13 occurred by simultaneous He++ irradiation of 1.3 × 1014 ion/cm2 s−1 in addition to the pre-irradiation effect. The change of the diffusion constant by the He++ irradiation was also evaluated with a computer code, which was developed to solve the diffusion equation by the Crank-Nicolson's method.

Al Kα X-ray spectra for equi-velocity H + and H + 2 ions of ≃ 0.9 MeV/amu incident on thin aluminum oxide films with thickness 100 and 300 A were observed. The intensity ratio of the KL 1 satellite line to the KL 0 main one for H + 2 incident on the films of thickness 100 and 300 A was about 10% and 4% larger than that for incident H + , respectively.