Itaru Nonaka

A 160 cm Synchro- and Variable Energy Ordinary Cyclotron

A 160 cm cyclotron have been constructed as the first accelerator of the Institute for Nuclear Study, University of Tokyo. This cyclotron can be used as a variable energy ordinary cyclotron as well as a synchro-cyclotron by changing the dee-system and the oscillator system. As an ordinary cyclotron it can produce protons of any desired energy between 7.5 and 15 MeV, deuterons between 15 and 21 MeV, and α particles between 30 and 42 Mev. These beams are now being used for various experiments on nuclear reactions and for production of radioisotopes. As a synchro-cyclotron, it can produce protons of 57 MeV in energy and the beam is extracted with high efficiency at a radius near n =1 with an electrostatic deflector.

Excited 0+ states in 52Fe, 54Fe, 56Ni and 58Ni from the (p, t) reaction

Abstract Excited 0 + states have been observed at 4.14, 2.54, 4.99 and 2.94 MeV in 52 Fe, 54 Fe, 56 Ni and 58 Ni, respectively, in the (p, t) reaction. A shell model interpretation of these 0 + levels is given in terms of four particle(hole) - m hole(particle) configurations.

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.

Angular Distributions of Protons from the Reaction 12C(α, p)15N

Angular distributions of protons corresponding to the ground state transition from the reaction 12 C(α, p ) 15 N have been measured at twelve energies of alpha particles between 25 and 39 MeV. Each angular distribution shows pronounced diffraction-like patterns, but there exists apparently a systematic shift in the shape and magnitude of angular distributions as the energy changes. At lower energies a sharp rise in the backward angles is observed, while at higher energies it is not observed. Angular distributions of protons corresponding to some excited state transitions have also been measured at 34.6 MeV.

Inelastic Proton Scattering from 90 Zr and 92 Zr

Differential cross sections of the inelastic proton scattering for low lying states of 90 Zr and 92 Zr were measured. The incident proton energy was about 14.5 MeV. Inelastic groups were analyzed with a precision magnetic analyzer. Attempts of DWBA fits were made. The general trend of experimental results is in agreement with that of the work of Corolado-ORNL group.

Electrical detection system for broad-range magnetic spectrometers

Abstract The performance of the electrical detection system used for the spectrum analysis of broad range magnetic analysers is described. Two kinds of detector array are used as the position indicator; the one is an array of 250 solid state detectors and the other is an array of 200 proportional-scintillation counter telescopes. They are followed with the same system of pulse handling. Informations are stored in an 1024 channel PHA core memory. Then the spectrum obtained can be processed with the PHA function.

The Hole State by the Reactions 40Ca(p, d)39Ca, 52Cr(p, d)51Cr and 60Ni(p, d)59Ni

Deuterons from (p, d) reactions on 40 Ca, 52 Cr and 60 Ni were investigated by using 55 MeV proton beam from the INS synchrocyclotron. Deuterons were analyzed by a broad range magnetic analyzer coupled with a pair of quadrupole magnets and were detected with forty fold proportional counters followed by a plastic scintillator. Predominant deuteron groups were observed corresponding to the single hole states of neutrons in 39 Ca, 51 Cr and 59 Ni. Angular distributions of the deuteron groups were analyzed in terms of the distorted wave Born approximation. Fairly good agreements between the calculation and the experiments were obtained for the angular distributions and the spectroscopic factors. Brief discussions on the properties of the hole states and the binding energies are presented.Deuterons from (p, d) reactions on 40 Ca, 52 Cr and 60 Ni were investigated by using 55 MeV proton beam from the INS synchrocyclotron. Deuterons were analyzed by a broad range magnetic analyzer coupled with a pair of quadrupole magnets and were detected with forty fold proportional counters followed by a plastic scintillator. Predominant deuteron groups were observed corresponding to the single hole states of neutrons in 39 Ca, 51 Cr and 59 Ni. Angular distributions of the deuteron groups were analyzed in terms of the distorted wave Born approximation. Fairly good agreements between the calculation and the experiments were obtained for the angular distributions and the spectroscopic factors. Brief discussions on the properties of the hole states and the binding energies are presented.

The (p. t) Reaction on Even-Even Deformed Nuclei

The (p, t) reactions on 158 Gd, 164 Dy, 172 Yb, 176 Hf and 184 W have been studied with 51.7 MeV protons. Triton spectra have been measured with a broad-range magnetic spectrometer with a 200 proportional-counter array. The cross sections for the states of the ground state rotational band which have been found to depend on mass number, have been analyzed by the distorted-wave Born-approximation. Especially Y 4 -diformation parameter β 4 for each nucleus has been obtained from the cross section for the 4 + state of the ground state rotational band. The cross sections for the first excited 0 + states have been found to have a mass number dependence and this dependence was compared with the prediction based on the pairing vibrational mode.

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.

Core-excited states of 54Fe from the 56Fe(p, t)54Fe reaction at 52 MeV

Abstract The (p, t) reaction on 56 Fe has been studied at a bombarding energy of 51.9 MeV using a broad-range magnetic spectrometer. States of 54 Fe were identified up to an excitation energy of 7.6 MeV. Differential cross sections were obtained for 16 triton groups. From the shapes of angular distributions J π = 0 + , 2 + , 3 − and 4 + were assigned for 11 levels. The 0 + state at 2.56 MeV was strongly excited (≈ 27% of the ground state transition). Comparison with the DWBA calculation was made based on the shell-model calculation on 54 Fe with ( f 7 2 ) −(n+2) ( p 3 2 , f 3 2 , p 1 2 ) n configurations for the low-lying even-parity states. The agreement with the experimental results was satisfactory for most of the states with appreciable (p, t) strengths which were interpreted as core-excited states mostly with 3h-lp and 4h-2p configurations. An empirical normalization constant of 12.5 was derived from the L = 0 ground state transition.