Yujiro Ikeda

Level Properties of 146Nd in the Decay of 146Pr

The decay of 24 min 146 Pr has been studied with Ge(Li), pure Ge, NaI(Tl) and plastic detectors in singles and coincidence modes. Sources were prepared by the chemical separation, called a rapid paper electrophoresis, from the fission products of 235 U. A total of 104 γ-ray transitions, 64 of them not reported before, have been observed and 88 transitions of them are incorporated into a level scheme comprising 32 excited states of 146 Nd. Observed Q β value was 4.15±0.15 MeV. Gamma-gamma directional angular correlation measurements in 146 Nd have been performed with 12 cascades each including 453.9 keV 2 + →0 + ground state transition. Spin assignments of 13 levels in 146 Nd were deduced. The low lying-states in 146 Nd are discussed in terms of the quasi band.

Decay of 148Pr Isomers to Levels of 148Nd

The decay of 148 Pr to levels on 148 Nd has been investigated with Ge(Li) and plastic detectors in singles and coincidence modes. Sources were prepared by a chemical separation from the fission products of 235 U. Forty γ-rays associated with 148 Pr decay have been observed and thirty four of them are incorporated into a level scheme including six new levels at 723.7, 1275.0, 1512.4, 1687.5, 2543.0 and 3129.6 keV. In comparison with the decay study of 148 Pr produced by the 148 Nd(n, p) reaction, this work, for the first time, could make clear the existence of 148 Pr isomers by γ-ray intensity ratios and their half-lives which are 2.27 ±0.04 and 2.0 ±0.1 min. A low lying level at 723.7 keV is assigned as a 0 + state from the γ- γ anisotropy measurements and low lying levels in the transitional nuclide 148 Nd are discussed in terms of the quasi band description.

Decay properties of 145Ce and 146Ce

Abstract γ-ray singles, γ-γ coincidence, s-ray singles, β-γ coincidence and half-life measurements have been performed to study decay properties of 145Ce and 146Ce by using a rapid paper electrophoresis. Thirty-two γ-rays from 145Ce, including 14 new ones, and 26 γ-rays from 146Ce, including 6 new ones, were observed, and 25 γ-rays and 21 ones were assigned to the decay schemes for 145Ce, including 3 new levels and for 146Ce, respectively. The half-lives of 145Ce and of 146Ce are 3.01 ± 0.06 and 13.52 ± 0.13 min, and observed Qβ values for 145Ce and for 146Ce are 2.6 ± 0.1 MeV and 952 ± 50 KeV, respectively.

Radiation Effect of YBa2Cu3O7-y Irradiated by γ-Rays and 14 MeV Neutrons

High-Tc superconductor YBa2Cu3O7-y was irradiated by γ-rays and 14 MeV neutrons to a dose up to 2.5×109 rad and 2×1015 n/cm2, respectively. No significant effects on the critical temperature were found in these irradiations, but the resistivity at 273 K changed slightly. It was concluded from this experiment that electronic process was not very influential in changing the Tc and the effects of 14 MeV neutrons on defect formation were assumed to be comparable to those of inpile neutrons.

Decay studies of 143La and 147Pr

Abstract The decay properties of 143 La and 147 Pr were investigated with Ge(Li), NaI(Tl) and plastic detectors in singles and coincidence modes with the help of a rapid paper electrophoresis. Twenty-three new γ-rays for 143 La and 9 new transitions for 147 Pr were observed and fairly precise decay schemes for 143 La including 5 new levels and for 147 Pr including 4 new levels were proposed. The half-lives of 143 La and 147 Pr are 14.14 ± 0.16 and 13.3 ± 0.4 min, and observed Q β values for 143 La and 147 Pr are 3.28 ± 0.10 and 2.77 ± 0.10 MeV, respectively.

Experiment and analysis of neutron spectra in a concrete assembly bombarded by 14-MeV neutrons

The neutron spectra in a concrete assembly bombarded by 14-MeV neutrons are measured by aa miniature NE-213 spectrometer and the multifoil activation method. The results obtained are within experimental error. The measured spectra are compared with calculated results obtained using the two-dimensional DOT3.5 transport code with 125-group structure cross-section libraries based on ENDF/B-IV,JENDL-2, and JENDL-3T (the test version of JENDL-3). In the deuterium-tritium neutron peak region, the measured and calculated neutron spectra are in agreement. However,all the calculations overestimate the measurements by 10 to 50% in the mega-eletron-volt region. In a still lower neutron energy range, where the {sup 197}Au(n,{gamma}){sup 198} Au reaction is dominant, discrepancies from {minus} 30 to + 40% are observed. Possible reasons are considered, but none explain the discrepancies.

Levels of 178Hf Populated in the Decay of 178m,gLu

Decay of 178m,g Lu has been studied by using Ge(Li), NaI(Tl) and plastic detectors. Sources were prepared by the 179 Hf(γ, p) 178m,g Lu reaction. Thirty-nine of forty γ-rays are assigned to the 178 Hf level scheme, which includes six newly observed levels at 1174.4( I π K =2 + 2), 1199.3(0 + 0), 1276.8(2 + 0) and 1322.4(3 - 2) keV in the 178g Lu decay and at 1364.04(9 - 8) and 1601.6(10 - 8) keV in the 178m Lu decay. Q β values are 2.05±0.05 MeV for 178g Lu and 2.25±0.03 MeV for 178m Lu. The most probable spin-parity assignments of 1 + and 9 - are proposed for the ground and isomeric states of 178 Lu, respectively. There is reasonable agreement between the experimental β branching ratios from 178m Lu to the 8 - band at 1147 keV and the Alaga rules. Discussions on the 178 Hf levels are made mainly on the basis of log f t values.

Measurement and Analysis of Induced Activities in Concrete Components Irradiated by 14-MeV Neutrons

The principal components of concrete were irradiated by 14-MeV neutrons for measurement of their induced activities to verify the activation calculation code THIDA-2 and its related cross-section l...

Decay Study of 144La

The decay of a short lived nucleus 144 La to levels of 144 Ce was investigated with Ge(Li), NaI(Tl) and plastic detectors in singles and coincidence modes. Radioactive sources were prepared by the chemical separation, a rapid paper electrophoresis, from the fission products of 235 U. The half-life of 144 La is 40.6 ±1.0 sec. Fifty-four γ-rays, including 17 new ones, were observed and 46 of them are incorporated in a decay scheme of 144 La including 11 new levels. The Q β value was deduced to be 4.3 ±0.1 MeV on the basis of the results of the γ- β coincidence measurements.

Excited states of 162Dy in the decay of 162Tb

Abstract The decay of 7.76 min 162 Tb has been studied with Ge(Li), NaI(Tl) and plastic detectors in singles and coincidence measurements. Sources were prepared using the 163 Dy(γ, p) reaction. A total of 47 γ-ray transitions, 35 of them not reported before, have been observed and 40 transitions are incorporated in a level scheme comprising 17 excited states of 162 Dy. A spin-parity assignment of 1 − is confirmed for the ground state of 162 Tb. Levels at 1745.5 and 1782.6 keV are assigned as the 1 + and 2 + states of the 1 + {n[521]↑-n[523]↓} band, respectively. Gamma-ray branching ratios favor K = 0 for the 1 − state at 1275.8 keV and K = 1 for the 3 − state at 1357.8 keV. A value of z 2 = 0.0355 ± 0.0021 is deduced for transitions between the γ-band and the ground-state band in 162 Dy.