M. Inoue

Elastic and inelastic scattering of 34.4 MeV alpha particles by 58Ni and 60Ni

Abstract Angular distributions were measured for elastic and inelastic alpha-particle scattering by 58 Ni and 60 Ni using the 34.4 MeV alpha beam of the INS Tokyo cyclotron. Scattered alpha particles were detected with a broad-range magnetic analyser and/or a semiconductor detector. About 40 angular distributions, which included those corresponding to the so-called two-phonon triplet states of 60 Ni, were obtained. The elastic-scattering data were analysed using the optical model. A diffraction theory and a distorted-wave theory were applied to analyse all the inelastic groups. The inelastic scattering leading to the first 2 + , the second 2 + and the first 4 + excited states of 58 Ni was analysed using form factors of a microscopic model. The so-called two-photon states, some possible 3 − states other than the most prominent ones and possible higher-spin (5 − , 6 + ) states are discussed.

Scattering of 34.4-MeV Alpha Particles by the Tin Isotopes

The angular distributions of alpha particles elastically and inelastically scattered by 116 Sn, 117 Sn, 118 Sn, 119 Sn and 120 Sn have been measured at 34.4 MeV. The angular distributions of the prominent groups corresponding to the quadrupole and octupole excitations were fitted with the results of DWBA predictions. In these calculations Coulomb excitation was found to be important for these nuclei. The extracted deformation parameters β 2 and β 3 for the even tin isotopes are in good agreement with those obtained by other workers. Both the shapes and magnitudes of the angular distributions of the groups corresponding to the quadrupole and octupole excitations for the odd-mass tin isotopes were found to be very similar to those for the even tin isotopes. Possible hexadecapole excitations are discussed.

Elastic scattering of 119 MeV 3He particles and energy and mass-number dependence of optical potential parameters

Abstract The elastic scattering of 119 MeV 3 He particles by 12 C, 27 Al, 58,60,62,64 Ni, 59 Co, 90,92 Zr and 89 Y has been investigated over a wide angular range in order to study the mass-number dependence of the optical potential and odd-even differences in the elastic scattering. The elastic scattering cross sections have been analyzed in terms of the optimal model. The data, except for 12 C, 27 Al and 59 Co, were fitted with r R = 1.21 fm, a R = 0.76 fm and r I = 1.17 fm, fixed at the average values. The following formulae were obtained for the three remaining parameters by combining with the energy dependence of the parameters (90–120 MeV) obtained previously: V=111.4−0.173E+ Z A 1 3 +14.9 N−Z A ( MeV ) W D =24.8−0.028E ( MeV ) , a I =0.754+0.78 N−Z A ( fm ) The depths of the valleys of the angular distribution in the case of 59 Co (I = 7 2 ) are considerably shallower than those for Ni isotopes, while the depths in the case of 89 Y (I = 1 2 ) are nearly the same as those for Zr isotopes. Thus it may be concluded that the odd-even differences are attributed to the scattering from the quadrupole moment of the odd- A nucleus (if I > 1 2 ).

Elastic scattering of 90–120 MeV 3He particles and an unambiguous optical potential

Abstract The elastic scattering of 109.2 MeV 3 He particles by 40 Ca, 58 Ni, 90 Zr and 116 Sn has been investigated over a wide angular range. The elastic scattering cross sections have been analyzed in terms of the optical model. The data for each nucleus studied were sufficient to eliminate the discrete ambiguity in the strength of the optical potential; the unique potential which fits the data has a real well depth of about 100 MeV and a corresponding volume integral per nucleon pair of about 310 MeV · fm 3 . The elastic scattering of 3 He particles by 58 Ni has been further measured at bombarding energies of 89.3 and 118.5 MeV, and the incident-energy dependence of the optical potential of 3 He particles for 58 Ni was obtained.

Elastic and Inelastic Scattering of 28.5 MeV Alpha Particles by Medium-Weight Nuclei

Elastic and inelastic scattering of 28.5 MeV alpha particles by Ni 60 , Ni 58 , Ti 48 , Co 59 and Al 27 has been studied. The angular distributions of the prominent group from the 2 + first excited state and the 3 - “anomalous” group for even nuclei were fitted by calculations based on Blair model. The angular distributions of the 4 + groups near 2.5 MeV in Ni 60 , near 2.5 MeV in Ni 58 and near 3.3 MeV in Ti 48 were found to have intermediate phase between the corresponding elastic distribution and the corresponding first 2 + inelastic distribution. On the other hand, the angular distributions of the 2 + groups near 3.1 MeV in Ni 60 , near 3.0 MeV in Ni 58 and near 2.4 MeV in Ti 48 were found to be almost exactly out of phase with the corresponding elastic distributions. Large cross sections of the inelastic alpha scattering to the 2.21– and 3.0–MeV states in Al 27 suggest that these states are the members of a K π =5/2 + rotational band based on the ground state.

The Osaka University RCNP 230-cm Isochronous Cyclotron

This paper describes the design, construction, performance and operation of the 230-cm cyclotron at Research Center for Nuclear Physics (RCNP). The design and construction of the machine were started in 1971. The first internal beam was obtained in July 1974 and the extracted beam was transported to the experimental area in August 1975.

Elastic and Inelastic Scattering of 28.4-MeV Alpha Particles by Sn, Cd, Ag, Cu and Ti

The angular distributions of alpha particles elastically and inelastically scattered by Sn, Cd, Ag, Cu and Ti have been measured at 28.4 MeV. For Sn, Cd and Ag, the angular distributions of the prominent groups corresponding to the quadrupole and octupole excitations were fitted by calculations based on Blair model in a preliminary step. The angular distributions of the groups near 1.22 MeV in Cd and near 0.90 MeV in Ag were found to have an intermediate phase between the corresponding elastic distribution and the distribution for the quadrupole excitation. The angular distributions for the inelastic scattering leading to various states of Cu and Ti were also obtained. Discussions are also presented based on the results of the DWBA analysis.

Excitation of 6+, 8+, 10+ and 9- States in 122Sn by Reactions (p, t) and (p, p')

The reactions 124 Sn( p , t ) and 122 Sn( p , p ) at 54.9 MeV have been studied using a high-resolution magnetic spectrograph “RAIDEN.” Experimental angular distributions were analyzed by DWBA calculations. The lowest 6 + , 8 + , 10 + ( h 11/2 ) 2 and 9 - ( h 11/2 , g 7/2 ) states in 122 Sn were established at 2.56, 2.69, 2.78 and 3.71 MeV, respectively.

Energy Spectra of Inelastic Scattering of 28.4-MeV Alpha Particles

Thin targets of 58 Ni, Cu, Ag, Ta and Au were bombarded with 28.4-MeV alpha particles and the energy spectra of emitted alpha particles were measured at several angles. The experimental values of the peak energies in the energy spectra at 150° arising from the compound-nucleus process were found to be in good agreement with the values of the Coulomb barrier height for an optical model potential. Prominent features of the energy spectra for Ag are as follows. The differential cross sections at a forward angle (30°) increase with alpha-particle energy, while those at backward angles (more than 90°) decrease with alpha-particle energy. At an intermediate angle (60°) between them, the energy spectrum is nearly flat. General features of the energy spectra for Ta and Au resemble those for Ag except for the low energy parts where the cross sections are decreased by the higher Coulomb barrier. These features may be explained by a mechanism which takes account of the collective excitation of the residual nucleus.

Proposal for a New Ring Accelerator

An intermediate energy particle accelerator complex is being designed for the next project of RCNP. This accelerator complex covers a wide energy range above the RCNP cyclotron beams and accelerates ions from proton through uranium with high intensity and good beam quality. Protons of 550 MeV are available for the Meson Factory. The main accelerator is divided into two separated-sector ring cyclotrons to keep away from the ¿z=1 resonance. An ordinary AVF cyclotron and a Wideroe type variable frequency linac will be used for light ion and heavy ion injection respectively.