T. Toriyama

RIKEN isotope separator on-line GARIS/IGISOL

Abstract This paper describes the fabrication and the characteristics of an isotope separator on-line (ISOL) which was constructed at the RIKEN Ring Cyclotron Facility. The ISOL consists of a gas-filled recoil separator and an ion-guide isotope separator on-line. Because of this combination the ISOL enables us to study short-lived isotopes of almost all elements.

Determination of surface-spin orientations of rare-earth iron garnet films by depth-selective Mössbauer spectroscopy

Spin orientations of a rare‐earth iron garnet film grown by a liquid‐phase‐epitaxial method on a gadolinium gallium garnet substrate were determined as a function of depth by means of the depth‐selective conversion electron Mossbauer spectroscopy. The spin‐tilt angle from the surface normal was found to increase from the bulk value up to 30° at the top of the surface. This phenomenon can be explained by the widening of the domain wall width toward the surface.

An ion-guide technique for on-line isotope separation coupled with a recoil-type beam separator

Abstract The efficiency of an ion-guide isotope separator on-line has been shown to increase to a great extent when only nuclear reaction products of interest are guided into a gas region of the ion-guide system after separating them from beam particles using a gas-filled recoil beam separator. An effective volume to the present ion-guide system is larger than in usual, indicating that this method is very effective in heavy-ion reactions yielding high recoil velocities for reaction products.

Depth selective conversion electron Mössbauer spectroscopy by use of a proportional counter

The depth selectivity of conversion electron Mössbauer spectroscopy by use of a proportional counter was studied in detail. For this purpose the pulse-height spectrum of conversion and Auger electrons emitted from a57Fe absorber was measured at the resonance Doppler velocity. From the spectrum it is found that the energy settings of 2–5 keV, 6–9 keV and 11–14 keV are suitable for depth selective analysis.

Energy distributions of 7.3 keV electrons passing through iron films for depth-selective Mössbauer spectroscopy

Abstract The energy spectra of 7.3 keV electrons passing through iron films were measured with a high resolution electron spectrometer by use of a thin 57Co source. The energy resolution of the spectrometer was set for 1.3% at 7.3 keV. The thicknesses of iron films for electron scatterers were 63, 121, 175, 279 and 385 A. From the measured energy spectra we deduced the energy distributions for a monolayer source. The method of analysis is described in detail. The present energy distributions are in fair agreement with those of the Monte Carlo calculation of Liljequist et al. The weight coefficients for the depth-selective conversion electron Mossbauer spectroscopy are presented for energy resolutions of 1, 2 and 3%.

Determination of surface-spin orientation of rare-earth iron garnet films by the Mössbauer spectroscopy

Abstract Spin orientations and hyperfine-field distributions of rare-earth iron garnet fils were dewtermined as a function of depth by means of energy-resolved conversion-electron Mossbauer spectroscopy. The spin-tilt from the surface normal was found to be (20 ± 5)dg less than 500 A in depth.

Improvement of S/N ratio of a proportional counter for depth selective conversion electron Mössbauer spectroscopy

The S/N ratio of a proportional counter for DCEMS of57Fe was improved by introducing a lead slit which collimates incident γ-rays to hit only a sample. The background spectrum due to the 122 and 136 keV γ-rays was obtained and it was found that the fraction of the background noise of these γ-rays was 65% in the energy region of 2–5 keV. The S/N ratio for a natural iron foil was in good agreement with the calculated one.

Application of the depth-selective conversion electron Mössbauer spectroscopy to rare-earth iron garnet films

Abstract Mossbauer spectra of RIG were measured with an electron spectrometer for energies of 7.3, 7.1 and 6.6 keV. The spectra for 0–100, 100–300 and 300–1500 A were deduced. Spin-orientation, area ratio of d- to a-site and line widths are derived as a function of depth.

CEMS study on iron film oxidized in various oxygen pressures

In order to prepare the Fe1−xO film, Fe metals evaporated on sapphire substrate were oxidized in the furnace for 2 hours at 800°C. The pressure of oxygen between 10−14 and 10−19 atm. was controlled by changing the flow rates of CO2 and H2 gases. After the oxidation, the conversion Mössbauer spectra for the samples were measured by a He+10%CH4 proportional counter. It was found that at this temperature the usually accepted Fe1−xO was not made for 2 hours, but the unknown oxidation state of Fe was formed at the oxygen pressure of 10−16.5 alm.. Its isomer shift relative to α-Fe and quadrupole splitting are 0.92 mm/sec and 1.71 mm/sec. The normal Fe1−xO was formed at the oxygen pressure of 10−16.5 atm. when the oxidation time was extended to 6.5 hours, in addition to Fe3O4.

Magnetic properties of H+ implanted bubble garnet films by means of depth selective conversion electron Mössbauer spectroscopy

Bubble garnet films before and after 50 keV H+ implantation have been studied by means of DCEMS. The spintilt angle of the films as grown after etching off 1000 å was measured to be 30±2‡ relative to the surface normal at the top of the surface. The doses of implanted H+ ions were 2, 4 and 8×1016 ions/cm2. Mössbauer spectra were measured after successive etching of the implanted layer. The magnetic hyperfine field was obtained as a function of depth. The implanted hydrogen distribution was also measured by the1H(15N, αγ)12C reaction.