Tamotsu Toriyama

Investigation of Iron Films by Internal Conversion Electrons Emitted after the Mössbauer Excitation

The surface structure of an iron metal film prepared by evaporation in high vacuum was investigated by the measurement of K internal conversion electrons emitted after the Mossbauer excitation. The evaporated sample was annealed in hydrogen gas and put into the vacuum chamber of a β-spectrometer to analyze the momentum of the emitted electrons. The Mossbauer spectra were taken using a 100 mCi 57Co source for various momenta of the electrons, corresponding to various depths of the sample. From these spectra it was found that iron oxide (mainly Fe3O4) existed near the surface of the sample and that the quantity of the iron oxides decreased exponentially with the depth from the surface. Possible applications of the present technique are suggested.

Q-Value Determination of the β + Decay of 60 Zn

Direct measurement of the β + spectrum of 60 Zn has been carried out with an online isotope separator. Radioactive 60 Zn was produced by the reaction of nat Ni(α, xn) 60 Zn. Emitted β- and γ-rays were measured with a planar type Ge(Li) and a coaxial type Ge(Li) detectors, respectively. Observed β + spectrum was decomposed by the method of Rehfield. The end-point energies of the analyzed spectra were obtained to be 3.082±0.064 MeV and 2.484±0.059 MeV, respectively. Assuming that the highest component of positrons feeds the 62 keV level in 62 Cu, the Q-value of the β + decay of 60 Zn was determined to be 4.166±0.064 MeV.

Structural and Magnetic Properties of Fe and Au Ion-Implanted Al2O3 Single Crystals

Au ion implantation in Fe ion-implanted Al2O3 (Fe/Al2O3) has been performed in order to tailor the structural, magnetic and optical properties of Fe granules in Al2O3 matrix. After Au ion implantation, Rutherford backscattering (RBS) measurements indicate the decrease and the redistribution of retained Fe atoms with the inclusion of Au atoms, and the patterns of X-ray diffraction (XRD) show the formation of Au granules in the Fe/Al2O3. Besides, the magnetization curves of the Fe/Al2O3 after Au ion implantation show still the superparamagnetic characteristics and the decrease of saturation magnetization, and the optical absorption measurements indicate the formation of Au granules in the Fe/Al2O3 in accordance with the XRD result. In addition, we investigated a behavior of Fe granules in Al2O3 matrix by conversion electron Mossbauer spectroscopy (CEMS), which indicates the decrease of superparamagnetic state as a function of Au ion dose. As a result, it is suggested that Au ion implantation has potentialities to tailor the physical properties of Fe granules in Al2O3 matrix.

Structural and magnetic properties of Fe-Al2O3 films prepared by helicon plasma sputtering

Fe-Al2O3 films have been prepared by on-off deposition of Fe with continuous Al2O3 deposition, and also subsequently irradiated by 400 keV Ar ions for controlling of the structural and magnetic properties of the films. CEM spectra of the as-deposited films show the decrease in the average hyperfine fields (Hhfs) with decreasing Fe/ Fe-Al2O3 volume ratio with keeping the Hhfs orientation parallel to the film plane. The decrease in Hhfs indicates the decrease of the Fe particle size and the in-plane orientation of Hhfs implies the non spherical shape of Fe particles in the film. On the other hand, 400 keV Ar ion irradiation induces the change from the superparamagnetic characteristics to the ferromagnetic one; the ferromagnetic peaks showing the random orientation of Hhfs appear and indicate the spherical growth of Fe particles in Al2O3 matrix.

Construction of 1.7 MV Pelletron Tandem Accelerator System and Its Application to Human Resource Development at Tokyo City University Atomic Energy Research Laboratory

Naoto HAGURA, Noriyosu HAYASHIZAKI, Takafumi UCHIYAMA, Yoshiyuki OGURI, Hitoshi FUKUDA, Katsunori KAWASAKI, Tamotsu TORIYAMA, Koichi MOCHIKI, Yukiko OKADA, Jun KAWARABAYASHI, Ishi MITSUHASHI and Haruaki MATSUURA 1 Department of Nuclear Safety Engineering, Tokyo City University, 1-28-1 Tamazutsumi, Setagaya-ku, Tokyo 158-8557, Japan 2 Atomic Energy Research Laboratory, Tokyo City University, 971 Ozenji, Asao-ku, Kawasaki, 215-0013, Japan 3 Laboratory for Advanced Nuclear Energy, Institute of Innovative Research, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550, Japan 4 Technical Department, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550, Japan 5 Electrostatic Accelerator Research Laboratory, 3-1-22-P2-502 Honcho, Higashikurume-city, Tokyo 203-0053, Japan 6 Laboratory for Materials Engineering with Quantum Beams, 4-2-17 Nishigahara, Kita-ku, Tokyo 114-0024, Japan

Structural Evolution of Fe Particles in Fe–Al2O3 Granular Films by Ar Ion Irradiations

Fe–Al2O3 granular films were prepared by helicon plasma sputtering. Fe64(Al2O3)36 in volume percent of as-prepared films was irradiated with 400 keV Ar ions in the fluence range of 1×1015–5×1016 ions/cm2. The growth of Fe particles with increasing ion fluence was observed from X-ray diffraction (XRD) patterns, magnetization curves, and conversion electron Mossbauer (CEM) spectra. The magnetization curves and CEM spectra of as-prepared Fe–Al2O3 films indicated the superparamagnetic nature and the ferromagnetic nature with increasing ion fluence. In addition, the reduction of Fe3+ component to the Fe2+ and metallic Fe components by ion irradiation was observed from CEM spectra.