M. Kondo

Angular Distributions of (α, n) Reaction son Be and C

The angular distributions of neutrons from the Be 9 (α, n )C 12 reaction which leaves C 12 in its ground-, 4.43- and 9.6-MeV excited states have been measured for alpha-particle energies between 17.5 and 22.1 MeV. These angular distributions show patterns which may be interpreted in terms of direct interaction theory. The essential feature of the distributions for each neutron group seems not to change with incident energy. The angular distributions of the ground-state neutron group from the C 12 (α, n )O 15 reaction were taken at alpha particle energies from 20.0 to 21.8 MeV. Marked change of distributions with bombarding energies. is not found, while it was seen in the C 12 (α, p )N 15 reaction at the same energy range.

Deuteron break-up in the fields of nuclei at 56 MeV

Abstract Proton continuum spectra induced by 56 MeV deuterons have been measured for 14 elements ranging from 12C to 209Bi. Each spectrum shows a prominent bump at forward angles due to the break-up of the incident deuteron. The peak energy of the bump is about half the deuteron energy for light elements and increases slightly for heavier elements. Projectile break-up calculations reproduce well the spectral shapes and the angular dependence of the bump spectra. The characteristics of the bump spectra are determined by the proton momentum distribution in the deuteron. The break-up cross section increases with target mass and is nearly proportional to ( A 1 3 + 0.8) 2 . The target mass dependence indicates that all partial waves smaller than the grazing angular momentum contribute to the deuteron break-up cross section at this energy. The total break-up cross section amounts to 24–35% of the deuteron total reaction cross section.

Optical model and folding model potentials for elastic scattering of 56 MeV polarized deuterons

Abstract Differential cross sections σ and all four analyzing powers Ay, Axx, Ayy and Axz have been measured for deuteron elastic scattering from 12C, 16O, 40Ca, 58Ni, 90Zr, 118Sn, 144Sm and 208Pb at 56 MeV. The tensor analyzing power Axz was measured using horizontally polarized deuterons. These data were analyzed in terms of an optical potential containing central, spin-orbit and TR type tensor terms. A complex TR tensor potential was necessary to explain Axz and the quantity X 2 = (2A xx + A yy ) √3 . The optical potentials obtained were compared with exact folding model calculations. The real part of the TR tensor potential is generally smaller than the folding model potential, especially for heavier nuclei. The imaginary TR potential is comparable with the folding model for lighter nuclei and is smaller than the folding model for heavier nuclei. The folding model TR potential overestimates the amplitudes of the Axz and X2 data. Features of the σ, Ay and Ayy data at large angles are discussed in connection with nuclear rainbow scattering.

Polarization measurements for P-12C elastic scattering between 40-75 MeV

Abstract Absolute values of the polarization in p- 12 C elastic scattering have been measured at 60.0 and 64.5 MeV at 47.5° in the laboratory system using a double scattering method and a method to measure an asymmetry with a polarized beam. The results are P (60.0 MeV, 47.5°) = 0.965 ± 0.011 and P (64.5 MeV, 47.5°) = 0.975 ± 0.11. Based on these values, the polarization measurements have been extended to the energy range from 40–75 MeV at several angles round 47.5° using the polarized proton beam and the energy degrader. Differential cross sections and polarizations from 15–115° are also presented at 65 MeV. These data will be valuable for the monitoring of beam polarization in this energy region.

Proton-neutron correlation in the deuteron breakup at 56 MeV and prior-form DWBA analysis

Abstract Proton-neutron angular correlations in the 12 C, 51 V and 118 Sn(d, pn) reactions have been measured at 56 MeV to investigate the deuteron breakup process. The elastic breakup which leaves the target nucleus in its ground state dominates the coincident spectra. The elastic breakup cross sections are estimated to be 36–48% of the inclusive breakup yields at 15° or 17.5°. In the angular correlations the protons are emitted predominantly on the side of the beam opposite to the neutrons. The experimental data have been analyzed using the prior-form DWBA. For both nuclear and Coulomb breakup, sufficient convergence of the calculations is obtained by including the pn angular momenta up to l = 2. For the nuclear breakup calculations, the l = 0 and 2 contributions dominate the cross sections. For the Coulomb breakup the l = 1 contribution is predominant. In the calculations the effect of the Coulomb breakup is seen at forward angles of the angular correlation. The DWBA calculations reproduce fairly well the coincident energy spectra and the angular correlations in the angular region where the protons are emitted on the side of the beam opposite to the neutrons. On the other hand the calculations overestimate the break-up cross sections by a factor of 2 to 10 in the angular region where the protons are emitted on the same side of the beam as the neutrons. The distributions of deuteron c.m. angular momenta that contribute to the breakup amplitude are examined to obtain information on the region of space in which the breakup reactions takes place.

Angular correlation of (3He, pd) reactions at 90 MeV and elastic break-up of 3He particles

Abstract Proton-deuteron angular correlations in the 12 C, 51 V, 90 Zr( 3 He, pd) reactions have been measured at 90 MeV to investigate the break-up process of the 3 He particle. The p-d pairs originate mainly from the break-up of the 3 He without target excitation (elastic break-up). In the coincident deuteron spectra, peaks at forward angles are observed at energies corresponding to the minimum recoil energy of the target nucleus. The p-d angular correlations show oscillatory patterns at large angles. The experimental results of the elastic break-up have been compared with the calculations of the radial-cutoff plane-wave Born approximation. By adjusting the cutoff radius, characteristic features of the experimental results are reproduced by the calculations, except for the absolute cross section. The results suggest that the elastic break-up process is associated with the diffractive scattering of the center of mass of the 3 He particle. The elastic break-up contribution to the break-up yields of the inclusive ( 3 He, d) reactions is also discussed.

The (α, p ) Reactions on Light and Medium-Weight Nuclei

Using approximates 22-Mev alpha particles the angular distributions of protons from ( alpha ,p) reactions on B/sup 10/, C/sup 12/, N/sup 14/, Na/sup 23/ , Mg/sup 24/, Pa/sup 31/, S/sup 32/, Ca/sup 40/, Sc/sup 45/, Mn/sup 55/, Fe/sup 54/, Fe/sup 56 /, and Co/sup 59/ were measured. The angular distributions on the light nuclei show diffraction-like patterns, but those on the medium-weight nuclei are peaked at forward angle and decrease monotonically with angle. These anguiar distributions are fitted with theories of a stripping reaction. At first they are compared with a theory obtained by using plane-wave approximation for wave functions of incoming alpha particles and outgoing protons. They are also compared with a theory using a simple distorted-wave approximation which fits better with the experimental results. The values of parameters in the theoretical formula show systematic differences in cases that tritons are captured by target nuclei with angular momenta 0 and 2. Some results on spectroscopic investigations of the target or residual nuclei are also discussed. The ( alpha ,p), ( alpha ,n), and (p, alpha ) reactions have a strong energy dependence near 20-Mev excitations, and above this region their energy dependences become smaller. (auth)

Measurements of analyzing powers Ay, Axx, Ayy and Axz in dp elastic scattering at Ed = 56 MeV

Abstract The differential cross section and all components of the analyzing powers A y , A xx , A yy and A xz have been measured in dp elastic scattering at 56 MeV. This is the first measurement of A xz in the cyclotron energy region. A xz has been measured with the beam polarized in the horizontal plane using the polarization tagging method. Faddeev calculations have been performed for four cases of the NN interaction. The Coulomb correction gave smaller effects at the present energy than at lower energies. Three of them reproduce the experimental data well. The agreement between the calculations and data for A xz was better than that reported at lower energy. The deuteron asymptotic D- to S-state ratio has been obtained and is consistent within the limits of uncertainty with previously obtained values.

Systematic study of the (d, p) reaction with 56 MeV polarized deuterons

Abstract Differential cross sections and vector analyzing powers were measured for the (d, p) reaction with 56 MeV polarized deuterons. The investigation covered the transitions to the single-particle states of the 1p. 2s, 1d. 2p, 1f, 3s, 2d and 1g shells. The analyzing powers showed a j -dependence which depended on the number of nodes in the radial wave function of the transferred neutron. DWBA and adiabatic model calculations were carried out. The DWBA calculations reproduced the experimental cross sections and analyzing powers for the stripping to the j > states. The adiabatic model did not necessarily improve the fits to the data for these transitions. As for the j transitions, on the other hand, the DWBA calculations could not reproduce the experimental angular distributions, while the adiabatic model calculations improved the agreement with the experimental data.

Polarization of Protons Scattered from Complex Nuclei

The experimental results for the angular dependence of polarization of elastically scattered protons from carbon at 14 and 16 MeV, and the polarization at 45° laboratory angle in the elastic scattering by 12 target nuclei at the energy of 12∼17 MeV are described. Qualitative agreement with the calculation in terms of optical potential with spin-orbit interaction is obtained for elastic scattering of protons by carbon.