Kiyota Yoshida

Observation of monochromatic and tunable hard X radiation from stratified Si single crystals

Abstract X radiation by 900 MeV electrons in accurately aligned 1–100 layers of 16 μm thick monocrystalline foils of Si was measured. We found intense and well collimated monochromatic photons, i.e. self-diffracted X rays (SDX), emitted to the “Bragg angle”. The intensity of SDX was much greater than the parametric X rays from a Si plate of equivalent thickness. For 35.5 keV X rays with 100 layered Si target, absolute brightness of SDX was comparable to the synchrotron radiation from a 1.7 GeV storage ring.

X-ray generation produced by relativistic electrons in compound “multifoil structure + crystal” targets

Abstract Novel concepts of X-ray production by relativistic electrons in stratified targets are developed. It is shown that by transmitting an electron beam through a compound target, consisting of a periodic multifoil structure and a crystal, it is possible to obtain the intense, tunable, quasi-monochromatic X-rays, emitting at large (Bragg) angles with respect to the electron beam axis due to the diffraction on the crystal of resonance transition radiation, previously generated in the multilayered structure. The first results of experimental investigation of this effect for 900 MeV electrons, transmitting through the periodic stack of 10 Mylar foils and pyrolytic graphite crystal, are presented. The obtained results show that, by using of the combined radiator, it is possible to produce much more intense X-rays than parametric X-ray radiation, emitting by relativistic electrons due to the diffraction of virtual photons of electron eigenfield during the electron passage through the crystal.

Electrochemical properties of ion implanted steel

Abstract The corrosion behaviour of chromium and nickel implanted steel was investigated by means of immersion potential measurement, polarization resistance measurement and the cyclic voltammetry in 0.5M acetate buffer solution (pH 5.0 ± 0.1) at room temperature. Ion implantation has been carried out with doses of 1 × 10 15 , 1 × 10 16 and 1 × 10 17 ions cm 2 at an energy of 150 keV. The electrochemical properties of implanted steel approach those of Fe18Cr alloy, as the implanted dose increases. The electrochemical properties of chromium implanted steel with a dose of 1 × 10 17 ions cm 2 at 150 keV are almost the same as those of Fe18Cr alloy. Ion implantation at an environmental temperature (typically room temperature) is a useful technique for the improvement of corrosion resistance.

Ion implantation through aluminum thin film deposited on iron

Abstract The effect of ion implantation into aluminum-deposited-iron plates has been investigated with reference to the concentration profiles of aluminum and iron, and the corrosion inhibition. Aluminum thin films ten nanometers thick, were prepared on pure iron substrates by ion beam sputter coating. Argon and oxygen molecule implantations were performed with a dose of 1016/cm2 at an energy of 150 keV. Concentration profiles of aluminum and iron were measured by means of secondary ion mass spectrometry. The corrosion behaviour of these specimens was evaluated by means of the multi-sweep cyclic voltammetry in 0.5 mol/dm3 acetate buffer solutions of pH 5.0 and 3.8. The results show that ion implantation through the deposited thin film results in making the interface of the film-substrate dispersed and improves the corrosion resistance.

Measurements of production cross sections of C and 26Al with high-energy neutrons up to En = 38 MeV by accelerator mass spectrometry

Abstract We have measured the neutron-induced formation cross sections up to E n = 38 MeV for 14 C from oxygen and 26 Al from silicon. SiO 2 and Si targets were irradiated with semi-monoenergetic neutrons from the 9 Be(p,n) 9 B and Li(p,n) 7 Be reactions at several proton energies. The neutron energy spectra were determined by a NE-213 spectrometer. The 14 C and 26 Al produced in the targets were measured by accelerator mass spectrometry using a 4 MV tandem accelerator at the Univeristy of Tokyo. The excitation functions for the 16 O(n,x) 14 C and nat. Si(n,x) 26 Al reactions were obtained from the neutron flux distribution and the measured number of atoms.

Anodic Dissolution Behaviour of Si- and Ti-Implanted Iron

Effects of silicon and titanium ion-implantations on anodic dissolution behaviour of iron have been investigated by multi-sweep cyclic voltammetry in acetate buffer solution (pH~5), secondary ion mass spectrometry and scanning electron microscopy. Ion-implantations have been carried out with a dose of 1×1017 ions/cm2 at an energy of 150 keV at room temperature. It is found that electrochemical properties of Si+- and Ti+-implanted irons are more inert than that of pure iron. Anodic dissolution phenomena of ion-implanted irons are discussed in relation to the shape of an electrochemically corroded surface observed by SEM and to the concentration profiles of implanted atoms measured by SIMS.

RIKEN 200 KV high current implanter for metal surface modification

Abstract A high current, metal ion implanter was constructed in order to aid the formation of a new metastable surface alloy. This implanter, called a RIKEN 200 kV high current implanter, is a modified Lintott high current machine (Series III), which has the advantages of having its own microwave ion source and an extra target chamber. The microwave discharge ion source without a hot-filament has a comparatively long lifetime because the chloride ions and radicals in a plasma during discharge of metal chlorides might prevent metal to deposit on the inner walls of the discharge chamber by bombarding and chemically cleaning them. An extra target chamber for metal modification is able to control the surface composition by utilizing the sputtering effect of the ion beam during ion implantation. The use of this ion source and the extra target chamber is suggested to be suitable for the production of metallic ions and for the implantation into metals. The case study will be introduced for Ti implantation into Fe.

Frictional Properties of Nickel and Copper Implanted Low Carbon Steel Plates

A study has been made of the frictional properties of nickel and copper implanted steel plates. Ion implantation was performed with doses of 1×1015–3×1017 ions/cm2 energies of 50–200 keV. The friction coefficients of Ni and Cu implanted specimens, measured at atmospheric room temperature with a Bowden-Leben type friction testing machine, had a tendency to increase as the total dose increased and the acceleration energy decreased. Concentration profiles were measured by secondary ion mass analysis in order to investigate the element concentration which contributes to the frictional properties. The results suggest that the amount of implanted ions remaining in the surface layer (0–400 A) is of first importance in the frictional properties of Ni and Cu implanted steel plates.

Coloring of iron surface controlled by Ti +O + double-ion implantations

Abstract Ti + O + double-ion implantations in pure iron have been performed with 1 × 10 17 Ti +/cm 2 at 150 keV and with 1 × 10 17 and 2×10 17 O +/cm 2 at 50 or 35 keV at room temperature. Oxidation state of pre-implanted titanium was investigated by means of X-ray photoelectron spectroscopy. Colored surfaces were produced by the double-ion implantations combined with an electrochemical oxidation of the specimens. Colors such as deep blue, purple, and brown appeared after the electrochemical oxidation with cyclic voltammetry in a 0.5 mol/dm 3 acetate buffer solution of pH 5. The mechanism of the coloring is discussed from analysis of the oxidation state of pre-implanted titanium and concentration-depth profiles of the titanium before and after the anodic oxidation of specimen electrodes. These results showed that double-ion implantations are a useful technique to achieve the coloring with corrosion inhibition of iron surfaces.

Comparison between properties of steels implanted with unseparated ions and a selected ion

Abstract Wear and corrosion properties of implanted steels with unseparated ions have been examined by comparing them with those of specimens implanted with selected ions. The gate-valve with a simple target chamber was made for performance of ion implantation without mass separation. Ion beams were produced by an rf-type ion-gun for gaseous elements and by the hollow-cathode type ion-gun for metal elements in order to achieve as pure a beam of ions as possible. When nitrogen or chromium is used as a main element, implanted steels have almost the same properties as those implanted with a single element. The results show that ion implantation in steels even without mass separation is beneficial enough to improve the surface properties.