H. Kamitsubo

Collective states of 110Cd, 114Cd and 116Cd excited in inelastic scattering of 55 MeV protons

Abstract Vibrational states in the doubly even nuclei 110 Cd, 114 Cd and 116 Cd, were investigated with inelastic scattering of 55 MeV protons. States strongly excited by E4 transitions were observed. The inelastic angular distributions for these states were analysed on the basis of the distorted wave Born approximation. For the interaction, a first-order collective excitation was assumed. The reduced transition ratios B (E4)/ B s.p. extracted from the analysis were several times stronger than the single-particle estimate. Possible collective hexa-decapole (2 4 -pole) vibrational states are discussed.

Effects of TiC distribution on the creep properties of helium injected JPCA

Abstract Creep tests at 650°C were carried out on the helium injected specimens of the Japanese Prime Candidate Alloy (JPCA) to clarify the effects of the TiC distribution on the suppression of helium embrittlement. Three different preinjection treatments were adopted for changing the TiC distribution. The decrease of creep rupture strength by helium was significantly suppressed by the TiC precipitates which had existed in the matrix before the introduction of the helium. On the other hand, the rupture elongation was appreciably reduced by helium in all three treatments, even though 80 to 90% of helium bubbles were trapped at the interfaces of the TiC precipitates in the matrix. Since a higher helium trapping efficiency cannot be easily achieved, it will be necessary to strengthen the grain boundaries themselves if further suppression of helium embrittlement is desired.

Elastic and inelastic scattering of 52 MeV protons from 106Pd, 108Pd and 110Pd

Abstract Elastic and inelastic scattering of 51.93 MeV protons from 106 Pd, 108 Pd and 110 Pd has been studied. The angular distributions for the first 2 + and 3 − states were well reproduced by first-order distorted-wave and coupled-channel calculations on the basis of the collective vibrational model. The differential cross sections for the second 2 + states were well fitted by coupled-channel calculations in which a small admixture of one-phonon states with the predominantly two-phonon states was assumed for the description of these states. The admixtures obtained were appreciably greater than those obtained from the B (E2) values in Coulomb excitation. The angular distributions for the first 4 + states showed strong diffraction patterns which were not reproduced by the calculations, even in the mixed form. The two-phonon picture combined with the coupled-channel theory is still less successful in describing the 4 + states than the 2 + states.

Anharmonic Contributions to High-Temperature EXAFS Spectra: Theory and Comparison with Experiment

In this work the anharmonic contributions to the high-temperature EXAFS spectra have been evaluated by considering the anharmonic contributions to the thermal vibrations of atoms and using the single-shell model. The anharmonicity calculated by our new formula is proportional to the temperature and inversely proportional to the distance between the absorbing atom and its neighbour located in a spherical shell which can be considered as the outer shell in the case of particles. The measured EXAFS spectra of Cu at several temperatures have been presented providing its strucuctural informations, among them the atom position of the first shell is different from the one calculated by the harmonic model by 0.05 A at 700 K and 0.01 A at 295 K. These measured results agree very well with the ones calculated by present anharimonic theory. This creates a good possibility for extraction of physical parameters from experiment by using our procedure.

The first 8+ and 10+ states in 28Si

Abstract A spin determination has been made for the states of 28 Si populated selectively by the 12 C( 20 Ne, α) reaction. From an angular correlation study the 8 + , 10 + and (8 + ) assignments are most probable for the states at 14.00, 15.97 and 17.75 MeV, respectively.

Large-angle scattering of 3He particles by 58Ni

Abstract The large-angle scattering of 3 He particles by 58 Ni is measured to obtain better optical parameters and to estimate the strength of the spin-orbit interaction, which yielded V 1s = 4.7 ± 1.0 MeV.

Collective states of 114Cd excited by inelastic scattering of 55 MeV protons

Abstract Vibrational states of 114 Cd were investigated with inelastic scattering of 55 MeV protons. The angular distributions for the 0.56, 1.95 and 2.39 MeV states were well reproduced with l = 2, 3 and 4 DWBA calculations, respectively, based on single-phonon excitation.

Microstructural observation on helium injected and creep ruptured JPCA

Detailed and quantitative TEM observation was performed on high temperature helium injected and creep ruptured JPCA to seek the prominent TiC distribution developed for suppression of helium embrittlement. Three different preinjection treatments were adopted for changing the TiC distribution. Considerable degradation in creep rupture strength by helium occurred in solution-annealed specimens, although there was much less effect of other treatments which included aging prior to injection. The concentration of helium at grain boundaries and the promotion of precipitation by helium during injection were responsible for the degradation. Therefore, the presence of TiC precipitates before helium introduction will help prevent degradation. On the other hand, the rupture elongation was reduced by helium after all treatments, although helium trapping by TiC precipitates in the matrix was successfully achieved. Consequently, the combined use of several methods may be necessary for further suppression of helium embrittlement.

Irradiation creep simulation at low proton flux

Abstract Light-ion irradiation creep simulation was carried out for 316 stainless steel at low proton flux ( ~ 2.5×10 −8 dpa/s) and with low fluence ( −3 dpa ) in an attempt to prevent a serious microstructural modification. Both 20% cold worked (CW) and recrystallized and aged (RCA) specimens were examined. A linear stress dependence (41–124 MPa) and a weak temperature dependence (200–350°C) were observed for both specimens in the torsional in-situ creep measurements. The creep rate was only slightly lower in the RCA specimen. A transient with a “negative” irradiation creep was observed only in the RCA specimen as previously reported at higher flux. The SIPA climb mechanism fails to predict the high creep rates of the present study as well as those of the primary in-reactor creep. The CCG model of Henager and Simonen for low fluence appears to be more promising, though it still does not provide a complete explanation.

Optical-Model Analysis of Elastic Scattering of 3He Particles from 58Ni at 24.15, 27.64 and 34.14 MeV

The elastic scattering of 3 He particles from 58 Ni at 24.15, 27.64 and 34.14 MeV has been studied. The measurements were done at laboratory angles extending from 15° to 170° at 25° or 5° intervals. An optical-model analysis was carried out with an automatic search code. Both Wood-Saxon potential and derivative Wood-Saxon potential were applied to the imaginary part of the optical potential. The latter gave better fit than the former at backward angles when a spin-orbit coupling potential was not used. An analysis using the optical potential with Thomas type spin-orbit coupling was also carried out. The depth of spin-orbit coupling potential depends on the depth of the real potential and the different potentials that minimize χ 2 / N for the cross section give similar polarizations. Ambiguities in the optical-model parameters appear in all the present analyses.